Effects of air pollutants on Mediterranean and temperate forest ecosystems

United States Department of Agriculture

Forest Service

Pacific Southwest Forest and Range Experiment Station

Berkeley California 94701

General Technical Report PSW-43

Proceedings of Symposium on

Effects of Air Pollutants on Mediterranean and Temperate Forest Ecosystems June 22-27, 1980, Riverside, California

Acknowledgments:

We gratefully acknowledge major conference support from the following organizations:

National Committee for Man and the Biosphere, Project 2-Temperate and Mediterranean Forest Ecosystems, U S . Department of State

Environmental Research Laboratory, U.S. Environmental Protection Agency, Corvallis

U.S. National Science Foundation Forest Service, U.S. Department of Agriculture

Other organizations providing additional forms of cosponsorship include: Statewide Air Pollution Research Center, University of California,

Riverside Department of Forestry and Resource Management, University of Cali-

fornia, Berkeley Lawrence Livermore Laboratory, University of California, Livermore Southern Plains Range Research Station, Agricultural Research, Science

and Education Administration, U.S. Department of Agriculture Oak Ridge National Laboratory, U.S. Department of Energy International Union of Forestry Research Organizations Stan Ranch Audubon Sanctuary, Division of Science and Sanctuaries,

National Audubon Society Society of American Foresters State of California Air Resources Board

Many individuals deserve recognition for making the Symposium a success. At the University of California's Statewide Air Pollution Research Center, 0. Clifton Taylor, Neva Friesen, and Merle Johnson deserve special mention for managing the funding aspects of the conference. As symposium administrator, Neva Friesen performed many difficult tasks with very effective results. Other staff who helped during the symposium are Marian Carpe- Ian, Marjorie McDennont, Joe Lick, Mark Seminoff, Mary Cadman, Donna Shaw, Dave Lick, Ronald Oshima, Patrick Temple, David Duncan, and Rob Lennox. From the Pacific Southwest Forest and Range Experiment Station, Forest Service,' U.S. Department of Agriculture, Berkeley, California, Marcia Wood handled public information and mass-media contacts; John K.

Publisher:

McDonald, Vincent Y. Dong, and Audrey F. Hakim managed the details necessary to the publication of these proceedings. Anthony Gomez and Robert Van Doren of the Station's Riverside staff handled the audiovisual requirements and assisted with the field trip.

Special credit is due Michael A. Fosberg and Lowell Smith who volun- teered to substitute for scheduled speakers who canceled within 2 weeks of the symposium. They also managed toprepare manuscripts on a tight schedule. In a similar situation, William H. Smith agreed to present a review of the subject listed as "Forests and Other vegetation as sinks for Air Pollution'' at theiast minute, in addition to presenting his own scheduled paper.

We are also grateful for the contributions of the Symposium Advisory Committee at all stages of organization. These individuals are Jay H. Blowers and Russel M. Bums, both Man and the Biosphere Program (MAB), U.S. Department of State; Robert Z. Callaham, C. Eugene Conrad, Jimmie L. Hickman, and Charles W. Philpot, all of the Station staff, Peter F. Ffolliott, University of Arizona and MAB 2; Jeffrey B. Froke, National Audubon Society; Herb Hahn, Forest Service and society of American Foresters; James N. Pitts, Jr., and 0. Clifton Taylor, University of California, Riverside; and Lawrence C. Raniere, U.S. Environmental Protection Agency.

Technical Program Committee: Paul R. ~ i i e r , Pacific Southwest Forest and Range Experiment Station,

Forest Service, U.S. Department of Agriculture, Riverside, California (Chairman)

Patrick I. Coyne, Agricultural Research, Science and Education Adminis- tration, U.S. Department of Agriculture, Woodward, Oklahoma

Leon S. Dochinger, Northeastern Forest Experiment Station, Forest Serv- ices, U S . Department of Agriculture, Delaware, Ohio

Joe R. McBride, Department of Forestry and Resource Management, University of California, Berkeley, California

Samuel B. McLaughlin, Jr., Oak Ridge National Laboratory, U S . De- partment of Energy, Oak Ridge, Tennessee

David T. Tingey, Cornallis Environmental Research Laboratory, U.S. Environmental Protection Agency, Corvallis, Oregon

Pacific Southwest Forest and Range Experiment Station P.O. Box 245, Berkeley, California 94701

October 1980

Proceedings of Symposium on

Effects of Air Pollutants Mediterranean and

Temperate Forest Ecosystems June 22-27, 1980, Riverside, California

Paul R . Miller Technical Coordinator

CONTENTS

Introduction Welcoming Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

James N. Pitts , Jr. Opening Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Robert Z . Callaham Air Pollution in Forests: Social Costs, Predictive Models,

and Public Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Charles F. Cooper

Historical Perspectives and International Concerns About Air Pollution Effects on Forests . . . . . . . . . . . . . . . . . . . . . . . . 10 Edwin Donaubauer

Natural Influences of Forests on Local and Regional Air Quality

Emissions and Air Resource Management Within Forests. . . . . . 13 Michael A. Fosberg and Hollis Record

Hydrocarbon Emissions from Vegetation . . . . . . . . . . . . . . . . . . . 24 David T . Tingey and Walter F . Burns

Background Levels of Trace Elements in Forest Ecosystems . . . 31 G . Bruce Wiersma and Kenneth W . Brown

Effects of Chronic Exposures to Gaseous Pollutants on Primary Production Processes

Photochemical Oxidant Impact on Mediterranean and Temperate Forest Ecosystems: Real and Potential Effects . . . . . . . . . . . . . 38 John M. Skelly

Primary Productivity, Sulfur Dioxide, and the Forest Ecosystem: an Overview of a Case Study . . . . . . . . . . . . . . . . . . . . . . . . . .51 Allan H . Legge

Effects of Airborne F on Forest Ecosystems . . . . . . . . . . . . . . . . 63 Robert G . Amundson and Leonard H. Weinstein

Air Pollution-a 20th Century Allogenic Influence on Forest Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79 William H. Smith

Secondary and Interactive Effects of Chronic Gaseous Pollutant Exposure of Producers, Consumers, and Decomposers

Influence of Chronic Air Pollution on Mineral Cycling inForests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 Paul J . Zinke

Forest Genetics and Air Pollutant Stress . . . . . . . . . . . . . . . . . . . 100 Stefan Biafobok

Interactions of Air Pollutants and Plant Disease. . . . . . . . . . . . . 103 Michael Treshow

Studies on Relationship Between Air Pollutants and Microorganisms in Japan . . . . . . . . . . . . . . . . . . . . . . . . . 110 Kiyoshi Tanaka

Sensitivity of Lichens to Air Pollution with an Emphasis on Oxidant Air Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . .117 Thomas H. Nash III and Lorene L. Sigal

Influence of Air Pollution on Population Dynamics of Forest Insects and on Tree Mortality . . . . . . . . . . . . . . . . . . . . . . . . . 125 Donald L. Dahlsten and David L. Rowney

Air Pollutants and Their Effects on Wildlife with Particular Reference to the House Wren (Delichon urbica) . . . . . . . . . .131 James R. Newman

Chronic Effects of Acidic Precipitation and Heavy Metals on Forest Ecosystems

The Acidity Problem-Its Nature, Causes, and Possible Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 Lowell Smith

Acid Precipitation Impact on Terrestrial and Aquatic Systems in Norway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 Lars N. Overrein

The Impact of Acidic Precipitation and Heavy Metals on Soils in Relation to Forest Ecosystems . . . . . . . . . . . . . . . 152 Stephen A. Norton, Denis W . Hanson, and Richard J . Campana

Impact of Heavy Metals on Terrestrial and Aquatic Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Tom C . Hutchinson

Effects of Acidic Precipitation on Health and the Productivity ofForests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 Ellis B. Cowling and Leon S. Dochinger

Simulation Modeling of the Effects of Chronic Pollutant Stress on Plant Processes and Plant Community Dynamics

Modeling Pollutant Uptake and Effects on the Soil-Plant-Litter

System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 R. J . Luxmoore

Data-Based Ecological Modeling of Ozone Air Pollution Effects in a Southern California Mixed Conifer Ecosystem . . . . . . . . 181 Ronald N. Kickert and Barbara Gemmill

Response of Plant Communities to Air Pollution . . . . . . . . . . . . 187 R. Guderian and K. Kueppers

Forecasting Effects of SO, Pollution on Growth and Succession in a Western Conifer Forest . . . . . . . . . . . . . . . . . . . . . . . . . . .200 J. R. Kercher, M.C. Axelrod, and G.E. Bingham

Forest Models: Their development and Potential Applications for Air Pollution Effects Research. . . . . . . . . . . . . . . . . . . . . .203 H. H. Shugart, S.B. McLaughlin, and D.C.West

Synthesis Session Opening Remarks and Summary of Panel/Audience

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215 Walter E. Westman

Integration: a Role for Adaptive Environmental Assessment andManagement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .221 Nicholas C . Sonntag, Robert R. Everitt. and Michael J. Staley

Poster Summaries Effects of Oxidant Air Pollutants on Pine Litter-fall

and the Forest Floor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225 Rodney J. Arkley and Rudolph Glauser

Regional Air Pollution Impacts on Forest Growth . . . . . . . . . . .226 Thomas V . Armentano, Orie L. Loucks, and Wayne T. Williams

Canopy Analysis of Pollutant Injured Ponderosa Pine in the San Bernardino National Forest . . . . . . . . . . . . . . . . . .227 M.C. Axelrod, P.I. Coyne, G,E. Bingham, J.R. Kercher, P.R. Miller, and R.C. Hung

Photosynthesis and Stomatal Behavior in Ponderosa Pine Subjected to Oxidant Stress: Water Stress Response . . . . . . .228 Gail E. Bingham and Patrick I. Coyne

Oxidant Impact on Ponderosa and Jeffrey Pine Foliage Decomposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229 J.N. Bruhn, J.R. Parmeter, Jr., and F. W . Cobb, Jr.

Integrated Lake-Watershed Acidification Study . . . . . . . . . . . . .230 Carl W. Chen and Robert A. Goldstein

Photosynthesis and Stomatal Response to Light and Temperature in Ponderosa Pine Exposed to Long-Term Oxidant Stress.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233 Patrick I. Coyne and Gail E. Bingham

The Effect of Air Pollution on Western Larch as Detected by Tree-Ring Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 Carl A. Fox and Thomas H.Nash 111

Acid Rain: Threshold of Leaf Damage in Eight Species from a Forest Succession . . . . . . . . . . . . . . . . . . . . . . . . . . . . .235 B.L. Haines, M. Stefani, and F . Hendrix

Prioritization of Research on Air Quality Related Resources of the National Parks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 E.A. Howard, L.M. Boyd, W.M. Brock, D.W. Morse, S.S. Shin, and K.L. Steel-Sabo

Estimation of Adverse Effects of Air Pollution on Danish Forests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .237 Ib Johnsen

Changes in Southern Wisconsin White Pine Stands Related to Air Pollution Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . .238 David F.. Karnosky

Effect of 0, and 0, + NO2 on Growth of Tree Seedlings . . . . 239 Lance W . Kress

Impact of Oxidant Air Pollution on Ponderosa and Jeffrey Pine Cone Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Robert F. Luck

Lichens as Air Quality Monitors . . . . . . . . . . . . . . . . . . . . . . . . . 241 P.D. Lulman, R.J. Fessenden, and S.A. McKinnon

Acid Precipitation in California and Some Ecological Effects . 242 John G. McColl and Mary K. Firestone

Leaf Litter Decomposition in the Vicinity of a Zinc Refinery . 243 W.D. Mcllveen

Effects of Chronic Air Pollution Stress on Allocation of Photosynthate by White Pine . . . . . . . . . . . . . . . . . . . . . . . 244 S.B. McLaughlin, R.K. McConathy, and D. Duvick

Effects of SO2 and Ozone on Photosynthesis and Leaf Growth in Hybrid Poplar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 Reginald D. Noble and Keith F. Jensen

Behavior of Airborne Flourides in Soils . . . . . . . . . . . . . . . . . . . 246 Janina Polomski, Hannes Fliihler, and Peter Blaser

Multiple Pollutant Fumigations Under Near Ambient Environmental Conditions Using a Linear Gradient Technique. . . . . . . . . . . . . . . . . . . . . 247 P.B. Reich, R .G. Amundson, and J.P. Lassoie

Changes in Plant Communities with Distance from an SO2 Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 Paul R. Scale

Lichens as Ecological Indicators of Photochemical Oxidant AirPollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .249 Lorene L. Sigal and Thomas H. Nash 111

The Effects of Air Pollutants on Forest Ecosystems inS.R.Slovenia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .250 Marjan Solar

Population Differences in Response to Sulfur Dioxide: a Physiological Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252 G.E. Taylor, Jr. and D.T. Tingey

Ozone Injury to Pines in the Southern Sierra Nevada of California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 Detlev R. Vogler and John Pronos

Modification of Chemical Contents of Precipitation by Passage through Oak Forests . . . . . . . . . . . . . . . . . . . . . . . 254 George T . Weaver and Jon D. Jones

Seasonal Variation of Inorganic and Organic Sulfur in Coniferous Needles Intensified by SO, Pollution. . . . . . . . 255 Karl Friedrich Wentzel and Gunther Gasch

Sulfur Dioxide and Oxidant Effects on Californian Coastal Sage Scrub. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 W.E. Westman and K.P. Preston

PREFACE

Sulfur dioxide from fuel combustion and ore smelting operations has caused significant damage to forest communities throughout the industrialized world. In the temperate regions, notably in Europe, the United States, Canada, and Japan, examples of damage and losses resulting from this pollutant are well-documented. Hydrogen fluoride emissions from aluminum reduction plants, brick kilns, and phosphate fertilizer plants also have caused significant damage in many localities. In Mediterranean climates, the combination of abundant sunshine and poorly controlled emissions of nitrogen oxides and hydrocarbons has resulted in extensive forested regions being exposed to photochemical oxidant air pollution. Ozone is the most damaging pollutant in this mixture. Acidic precipitation, derived principally from sulfur oxide emissions, recently has been shown to have severe effects on aquatic ecosystems in northeastern United States, Canada, and northern Europe. The projected increase in the use of coal for energy generation and the continuing growth of urban centers, accompanied by automobile emissions, are two conditions that suggest a continuing and more pervasive influence of air pollution on terrestrial and related aquatic ecosystems.

A large body of knowledge has been assembled that describes pollutant effects on individual species as a result of both field observations and controlled experiments. Efforts are being made to use the tools of systems analysis (modeling) to interpret and predict pollutant effects on processes at both the individual species and plant community levels. The ultimate goal is to improve interpretation of pollutant effects on ecological systems so that optimal protective and management measures can be taken to assure a more healthy environment.

Experimenters and modelers can advance more rapidly if a better exchange of ideas and essential data can be stimulated. A symposium was planned to encourage closer communication between experimen- talists carrying out specialized studies of the effects of major air pollutants on individual forest species and

researchers using computer simulation models to interpret and predict long-term pollutant effects at the plant community and ecosystem levels. This Sym- posium, held in Riverside, California, June 22-27, 1980, was designed to report and discuss the state of knowledge of single species-single pollutant relationships, the interactions of producers, consumers, and decomposers under pollutant stress, and the use of ecological systems models for interpretation and prediction of pollutant effects. In addition, the present state of knowledge was examined in relation to an overarching ecological concept: resilience of ecosystems. Another important question was the search for indicators of systems-level effects of air pollution on ecosystems. For example, is an effect on nutrient cycling a reliable indicator of system-level change induced by pollution?

Twenty-eight papers were presented in the formal sessions and 29 poster summaries were displayed concurrently. Registered participants numbered 128. Most participants attended a field trip to the San Bernardino mountains for one-half day. Fifteen nations were represented including Austria, Canada, Czechoslovakia, Denmark, Egypt, West Germany, Japan, Mexico, Norway, Poland, Saudi Arabia, Sweden, Switzerland, United States of America, and Yugoslavia.

To facilitate the publication of the Symposium Pro- ceedings, we decided to have each author assume full responsibility for submitting manuscripts in photo- ready format by the time the conference convened. The views expressed in each paper are those of the author and not necessarily those of the sponsoring organizations. Trade names are used solely for necessary information and do not imply endorsement by the sponsoring organizations.

Paul R. Miller Forest Service, U.S. Department of

Agriculture Technical Coordinator

Introduction

Welcoming ~emarks'

2James N . P i t t s , Jr.

Good morning. On behalf of D r . David Saxon, Through t h e i r e f f o r t s and t h e pioneering re-President of the Univers i ty of Ca l i fo rn ia , D r . search of the l a t e Arie Haagen-Smit and o t h e r s , om& Rivera, Chancellor of UCR, and we of t h e i t became c l e a r t h a t we were deal ing with an

Statewide A i r Po l lu t ion Research Center, I would oxidizing atmospheric system formed by t h e l i k e t o welcome you t o t h i s i n t e r n a t i o n a l ac t ion of s u n l i g h t on hydrocarbons and oxides symposium. We t r u s t you w i l l have a s c i e n t i f i - of ni t rogen. c a l l y i n t e r e s t i n g and chal lenging experience during t h i s week. During t h e l a s t twenty years , much of it

under t h e l eadersh ip of Cl i f Taylor, research The sub jec t of t h i s meeting is timely and has been conducted here in two major a r e a s :

important. The accura te assessment of S tud ies of p o l l u t a n t e f f e c t s on p l a n t s , vegeta-b io log ica l , economic, and a e s t h e t i c impacts of t i o n , and f o r e s t ecosystems, and t h e chemistry a i r p o l l u t a n t s on f o r e s t ecosystems i s e s s e n t i a l of a i r po l lu t ion . This has been a p a r t i c u l a r l y i f we a r e t o develop cos t -e f fec t ive con t ro l u s e f u l combination of i n t e r e s t s because we have s t r a t e g i e s of a i r p o l l u t i o n . Overcontrol can one group of s c i e n t i s t s working on one a x i s of lead t o economic p e n a l t i e s i n t h e form of e x t r a the c l a s s i c dose-response curve, t h a t i s , t h e c o s t s f o r expensive technologies f o r p o l l u t a n t atmospheric chemists whose func t ion is t o removal. On t h e o t h e r hand, undercontrol can descr ibe t h e dose received by man, animals, o r l ead t o economically unacceptable p l a n t damage p l a n t s , and another group working on t h e response which impacts n o t only our a g r i c u l t u r a l and a x i s , t h e p l a n t s c i e n t i s t s i n v e s t i g a t i n g t h e f o r e s t indus t ry b u t a l s o our r e c r e a t i o n a l i n t e r a c t i o n s of a i r p o l l u t a n t s with vege ta t ion . a c t i v i t i e s . We t r u s t t h i s symposium w i l l e luc ida te a r e a s of f u t u r e research t h a t w i l l Most of you a r e f a m i l i a r wi th t h e work which provide a more ex tens ive da ta base upon which has been done here in t h e p l a n t sc iences area . t o generate r e l i a b l e models t h a t can be used f o r Let me j u s t mention t h a t one of t h e major r o l e s such c o s t - e f f e c t i v e con t ro l s t r a t e g i e s . of t h e atmospheric chemists a t t h e Center has

been the unequivocal spectroscopic i d e n t i f i c a -We i n C a l i f o r n i a a r e p a r t i c u l a r l y s e n s i t i v e t i o n and measurement of s e v e r a l new gaseous

to t h e t h r e a t , indeed t h e a c t u a l i t y , of s e r i o u s oxygenated and ni t rogenous spec ies t h a t a r e a i r p o l l u t i o n damage t o crops, f o r e s t s , e t c . formed in photochemical a i r po l lu t ion . These Agricul ture remains our number one indus t ry , include formaldehyde, formic a c i d , n i t r i c a c i d , with tourism and assoc ia ted r e c r e a t i o n a l n i t r o u s a c i d , and t h e n i t r a t e r a d i c a l , NO3. a c t i v i t i e s a l s o making a major con t r ibu t ion t o Whether o r n o t such gaseous spec ies w i l l prove t h e economic wel l being of our s t a t e . t o be s i g n i f i c a n t phytotoxicants is a quest ion

t h a t we leave t o you "response" s p e c i a l i s t s . The f a c t t h a t t h e symposium i s being held

here a t UCR seems appropr ia te s i n c e i t was a I n c los ing I want t o thank D r s . Paul Miller group of p l a n t s c i e n t i s t s headed by John Middle- and Cl i f .Taylor and M r s . Neva Fr iesen f o r ton who, i n t h e l a t e 1940s, f i r s t showed t h a t t h e i r outs tanding e f f o r t s in organizing t h i s p lan t damage seen in Los Angeles County was in symposium. Many o t h e r people deserve a g r e a t f a c t due t o a new type of a i r po l lu t ion . dea l of c r e d i t a s we l l , b u t t h e r e simply i s no t

time t o acknowledge them ind iv idua l ly . Le t me j u s t say t h a t w e a r e pleased t o hos t a meeting of t h i s importance and we look forward t o l ea rn ing of t h e s i g n i f i c a n t r e s u l t s t h a t w i l l

p r e s e n t e d a t t h e Symposium on E f f e c t s of Air emerge from your gather ing. I am c e r t a i n P o l l u t a n t s on Mediterranean and Temperate these r e s u l t s w i l l be of l a s t i n g importance t o Forest Ecosystems, June 22-27, 1980, Rivers ide, t h i s c r i t i c a l a r e a of t h e a i r p o l l u t i o n problem. Ca l i fo rn ia , U.S.A.

2 ~ r o f e s s o r of Chemistry and Di rec to r , Statewide A i r P o l l u t i o n Research Center, Univers i ty of C a l i f o r n i a , Rivers ide, Ca l i fo rn ia .

Opening ~emarks'

Robert Z.

My reasons f o r being h e r e a r e t o welcome you on behalf of t h e F o r e s t Se rv ice , U.S. Department of A g r i c u l t u r e , and t o in t roduce you t o t h i s conference. I want t o exp la in t o you t h e o b j e c t i v e s of t h e conference, why i t was organized, and who made i t poss ib le . But I a l s o want t o in t roduce you t o each o t h e r , s o t h a t you w i l l know which c o u n t r i e s you r e p r e s e n t , and why you a r e here .

I w i l l begin by s t a t i n g t h e t h r e e objec- t i v e s of t h i s conference. The f i r s t i s t o review c u r r e n t informat ion on s p e c i f i c gaseous and p a r t i c - u l a t e p o l l u t a n t s and t h e i r e f f e c t s on f o r e s t eco-systems. F o r e s t s a s sources of p o l l u t a n t s and a s s i n k s f o r p o l l u t a n t s a r e included. The second o b j e c t i v e i s t o ana lyze primary, secondary, and i n t e r a c t i v e e f f e c t s of ch ron ic p o l l u t a n t s on ecosystems. Modeling w i l l b e explored a s a t o o l t o s imula te observed and expected e f f e c t s . L a t e i n t h e program, s t r a t e g i e s f o r a s s e s s i n g and managing environmental impacts of a i r p o l l u t a n t s w i l l be discussed. The t h i r d o b j e c t i v e i s t o s t i m u l a t e i n t e r n a t i o n a l communication t o a s s e s s t h e s t a t e of knowledge and t o i d e n t i f y gaps i n our knowledge.

Severa l y e a r s ago, t h e U.S. Environmental P r o t e c t i o n Agency (EPA) gave a g r a n t f o r r e sea rch t o D r . C l i f Taylor i n t h e Sta tewide A i r P o l l u t i o n Center h e r e a t R ive r s ide . The F o r e s t Se rv ice has a c t i v e l y cooperated and p a r t i c i p a t e d i n t h e r e s u l t - ing r e s e a r c h up t o t h e p r e s e n t time. Research under t h a t g r a n t i s drawing t o a c l o s e . This con- f e r e n c e was planned, t h e r e f o r e , t o sum up what has been accomplished. S c i e n t i s t s involved i n t h i s m u l t i m i l l i o n d o l l a r r e s e a r c h e f f o r t have t h i s oppor tun i ty t o t e l l o t h e r s what they have l ea rned

Presented a t t h e Symposium on E f f e c t s of A i r P o l l u t a n t s on Mediterranean and Temperate F o r e s t Ecosystems, June 22-27, 1980, R ive r s ide , C a l i f o r n i a , U.S.A.

D i r e c t o r , P a c i f i c Southwest F o r e s t and Range Experiment S t a t i o n , F o r e s t Se rv ice , U.S.Department of Agr icu l tu re , Berkeley, C a l i f o r n i a .

2Callaham

and t o i d e n t i f y problems t h a t remain t o be solved. Another purpose i n organiz ing t h i s conference is t o broaden l o c a l pe r spec t ives by importing e x p e r t s from around t h e world t o t a l k about our problems. The f i n a l purpose i s t o t r a n s f e r technology gen- e r a t e d by t h i s r e s e a r c h program t o t h e managers of a i r , l and , and f o r e s t r e sources .

This conference was made p o s s i b l e through t h e coopera t ive e f f o r t s of s e v e r a l agencies . The F o r e s t Se rv ice , U.S. Department of A g r i c u l t u r e , and t h e Sta tewide A i r P o l l u t i o n Research Cen te r , Un ive r s i ty of C a l i f o r n i a , a t R ive r s ide , a r e spon-s o r s . IUFRO, t h e I n t e r n a t i o n a l Union of F o r e s t r y Research Organizat ions , having about 380 member o rgan iza t ions i n 86 c o u n t r i e s around t h e world and a s u b j e c t group concerned w i t h a i r p o l l u t i o n , i s a cosponsor. The U.S. Department of Energy and t h e U.S. Environmental P r o t e c t i o n Agency have made t h e i r people and t h e i r r e sources a v a i l a b l e . EPA w i l l he lp t h e F o r e s t Se rv ice t o pub l i sh t h e proceedings. The U.S. Department of S t a t e , p a r t i c u - l a r l y t h e Man and t h e Biosphere Program through i t s P r o j e c t 2 ~ M e d i t e r r a n e a n and Temperate F o r e s t Ecosystems--has provided f i n a n c i a l suppor t . UNESCO, t h e i n t e r n a t i o n a l home of t h e Man and t h e Biosphere Program, has paid t o b r ing t h r e e i n t e r - n a t i o n a l p a r t i c i p a n t s he re . For a l l of t h i s sup- p o r t and cooperat ion, t h e o rgan ize r s a r e most g r a t e f u l .

My f i n a l and, perhaps, unexpected reason f o r being h e r e i s t o in t roduce you t o each o t h e r . Although t h i s is no t o f t e n done a t confe rences , I have found i t t o be an e f f e c t i v e means of stimu-l a t i n g communication. I am going t o c a l l t h e r o l l of c o u n t r i e s , more o r l e s s i n a l p h a b e t i c a l o r d e r . and a s k t h e i n d i v i d u a l s named t o s t and . ( I n t r o -duc t ions followed.) About 20 pe rcen t of t h e people h e r e a r e from o u t s i d e North America. L e t us g i v e t h e s e v i s i t o r s a s p e c i a l welcome. Walk up t o them. Int roduce yourselves . Ask t h e s e v i s i - t o r s about programs and problems i n t h e i r coun t r i e s .

Now t h a t we know what c o u n t r i e s a r e r e p r e s e n t e d , l e t me c a l l f o r a show of hands t o f i n d o u t why

1

130 of you a r e he re . How many a r e p r i m a r i l y teachers o r p ro fesso r s? About 7 pe rcen t . How many a r e managers of l and o r f o r e s t r e sources? About 9 pe rcen t . How many a r e managers of a i r re-sources? Only about 2 pe rcen t . That i s s u r p r i s -ing. How many of you a r e s t u d e n t s , no t y e t i n t o p ro fess iona l a c t i v i t i e s ? About 2 pe rcen t . The remainder of y o u ~ a b o u t80 p e r c e n t ~ a r e s c i e n t i s t s and i n v e s t i g a t o r s . That i s about what I expected.

And now my r o l e is f u l f i l l e d . I have in t roduced you t o t h e conference and t o each o t h e r . I expect you t o b e n e f i t bo th p r o f e s s i o n a l l y and p e r s o n a l l y from t h i s conference . L a s t l y , I express my deep a p p r e c i a t i o n t o a l l who have con-t r i b u t e d t o t h e o r g a n i z a t i o n of t h i s conference and p a r t i c u l a r l y t o Dr. Pau l M i l l e r .

On behal f of t h e F o r e s t Se rv ice , I thank you f o r coming. The u l t i m a t e success and meaning of t h i s conference depend on you.

Air Pollution in Forests: Social Costs, Predictive Models, and Public ~ o l i c y '

Char les F. Cooper 2

A b s t r a c t : Long t ime s c a l e s , s p a t i a l v a r i a t i o n i n ecosystems, and d i f f e r i n g v a l u e judgments make models almost e s s e n t i a l f o r s o c i e t a l consensus about a i r p o l l u t i o n . Three c a t e g o r i e s of pol icy-or iented models a r e desc r ibed . Empirical time s e r i e s models a r e good f o r immediate d e c i s i o n s but a r e i n h e r e n t l y a short-term device . De ta i l ed s t r u c t u r a l - f u n c t i o n a l models emphasize r e l a t i o n s h i p s among components and demonstrate t h e s i g n i f i c a n c e of i n t e rconnec t i o n s . Small e r r o r s , however, can lead t o er roneous q u a n t i t a t i v e r e s u l t s , l i m i t i n g t h e i r va lue f o r d i r e c t p o l i c y d e c i s i o n s . Aggregated po l i cy -o r i en ted models p rov ide b e t t e r compliance between model ou tpu t and v a l i d a t i o n da ta a t t h e c o s t of l o s s of r e s o l u t i o n . Good models should be c l e a r l y documented, r e s u l t s should be comprehensible, l i m i t s and probable e r r o r bands c l e a r l y s t a t e d , t hey should be f l e x i b l e enough t o deal with unan t i c ipa t ed problems without a t t empt ing t o t a l g e n e r a l i t y , and r e s u l t s should be c l e a r l y d i sp layed . A model is an a id t o decisionmaking, not a d e c i s i o n maker. For i t t o be e f f e c t i v e i n t h a t r o l e , t h e r e must be mutually s u p p o r t i v e i n t e r a c t i o n among modelers, b i o l o g i c a l and s o c i a l s c i e n t i s t s , and d e c i s i o n makers. Perhaps t h e most s i g n i f i c a n t r o l e of models i s i n he lp ing t o avoid subopt imizat ion and i n f a c i l i t a t i n g communication among d i s c i p l i n e s and p r a c t i t i o n e r s .

Atmospheric p o l l u t i o n i s a f f e c t i n g f o r e s t The eco log ica l and s o c i a l consequences of a i r ecosystems i n much of t h e world. A major purpose p o l l u t i o n i n f o r e s t s a r e t h e r e s u l t of complex of t h i s symposium is t o e s t a b l i s h a s c i e n t i f i c i n t e r a c t i o n s of processes wi th many temporal , consensus about t h e n a t u r e , magnitude, and t ime s p a t i a l , and va lue s c a l e s . Long-t ime s c a l e s , t r e n d of t h e s e e f f e c t s . A s c i e n t i f i c r e s o l u t i o n , v a r i a t i o n s among ecosystems, and d i f f e r e n c e s of however, is not enough. Analys is of "The E f f e c t s opin ion about va lues make c l a s s i c a l l a b o r a t o r y of A i r P o l l u t a n t s on Mediterranean and Temperate exper imenta t ion almost u s e l e s s f o r de f in ing t h e s e Fores t Ecosystems" must a l s o t a k e s o c i e t a l l a r g e s c a l e consequences. Models a r e t h u s o b j e c t i v e s and l i m i t a t i o n s i n t o account . e s s e n t i a l f o r he lp ing t o a r r i v e a t a s o c i e t a l

consensus about how t o t r e a t a i r p o l l u t i o n . Ecosystems used and enjoyed by man a r e

embedded i n a l a r g e r s o c i a l system; dea l ing wi th COMPLEXITY OF THE FOREST AIR POLLUTION PROBLEM e f f e c t s of a i r p o l l u t i o n on t h e s e ecosystems, l o c a l l y , r e g i o n a l l y , o r g l o b a l l y , t h u s becomes a It is a t ru i sm t h a t t h e f o r e s t a i r p o l l u t i o n ques t ion of pub l i c pol icy . E s s e n t i a l t o sound problem is complex, but t h e n a t u r e of t h a t p u b l i c po l i cy fo rmula t ion is knowledge of t h e complexity must be understood i f we a r e t o s o c i a l c o s t s of a i r p o l l u t i o n and its c o n t r o l . A v i s u a l i z e t h e r o l e of models i n d e a l i n g wi th i t . major problem, of cour se , i s how t o measure t h e s e The po in t s mentioned h e r e a r e e l abora t ed by o t h e r c o s t s . Th i s symposium should lead us some way a u t h o r s i n t h i s volume. toward b e t t e r assessment of t h e r e a l c o s t s of f o r e s t a i r p o l l u t i o n . A i r p o l l u t i o n a f f e c t s i n d i v i d u a l p l a n t s

d i r e c t l y , i n ways which change d u r i n g t h e cour se of t h e p l a n t ' s l i f e h i s t o r y . It a f f e c t s p l a n t s i n d i r e c t 1 y, through impacts on s o i l s and on

p r e s e n t e d a t t h e Symposium on E f f e c t s of A i r consumers and decomposers. E f f e c t s on p l a n t s , i n P o l l u t a n t s on Medi ter ranean and Temperate F o r e s t t u r n , a r e r e f l e c t e d i n o t h e r t r o p h i c l e v e l s .Ecosystems, June 22-27, 1980, R ive r s ide , C a l i f o r - C r i t i c a l l y important i s t h e dynamic r e a c t i o n of n i a , U.S.A. ecosystems, which u s u a l l y cannot be p red ic t ed from

a simple summation of t h e r e sponses of i n d i v i d u a l 2 ~ r o f e s s o r of Biology and D i r e c t o r of Center f o r organisms .

Regional Environmental S tud ie s , San Diego S t a t e U n i v e r s i t y , SanDiego , C a l i f o r n i a 92182. Soc ia l consequences stem from l o s s of

product ive r e sources and amenity va lues . Wood and

forage growth may diminish , a l o s s t h a t w i l l be increas ingly s i g n i f i c a n t i f f o r e s t s a r e i n g r e a t e r demand f o r biomass a s a source of energy o r s t ruc tu red chemicals, o r i f inc reas ing need f o r g r a i n a s food l eads t o more pressure on rangelands. Aesthet ic and r e c r e a t i o n a l values a r e l o s t . The degraded appearance of t h e smog-affected f o r e s t s of t h e San Gabriel Mountains a r e apparent t o a l l who have seen them. W i l d l i f e , both game and non-game, may s u f f e r . Lakes and s t reams i n severa l p a r t s of North America and Europe have l o s t much of t h e i r capaci ty f o r f i s h production (Loucks 1980). Of course, t h e r e may be benef ic i a l impacts a s well--a1 l e v i a t i o n of l o c a l s u l f u r d e f i c i e n c i e s , f o r ins tance. Both b e n e f i c i a l and det r imental e f f e c t s vary i n t ime and space.

A i r p o l l u t i o n opera tes a t many time s c a l e s . Hol l i n g (1973) has d i s t ingu i shed between f a s t and slow v a r i a b l e s . Fas t v a r i a b l e s a r e genera l ly amenable t o convent ional l abora to ry exper imentat ion, and a r e t h e kind t h a t a r e usua l ly s tudied i n b io log ica l research. Slow v a r i a b l e s , however, t ake long enough t o manifes t themselves tha t c o n t r o l l e d exper imentat ion i s impract ica l i n many r e a l world s i t u a t i o n s where a c t i o n cannot wait. Decision makers must a l s o deal with a high degree of s p a t i a l he te rogene i ty i n both p o l l u t a n t s and t h e i r t a r g e t ecosystems. Theory and research i n ecology h a s not u n t i l now d e a l t very well with s p a t i a l processes .

F i n a l l y , a i r p o l l u t i o n is only one of many stresses a f f e c t i n g f o r e s t ecosystems. Mul t ip le s t r e s s e s may i n t e r a c t s y n e r g i s t i c a l l y o r they may he lp t o coun te rac t one another . We need t o know more, f o r i n s t a n c e , about t h e combined impact of a i r p o l l u t i o n and c l ima te change, whether due t o d e l i b e r a t e weather modi f i ca t ion o r inadver ten t c l i m a t i c change. Increased atmospheric carbon dioxide from burning of f o s s i l f u e l seems l i k e l y t o warm t h e e a r t h ' s c l ima te and, perhaps, t o s t i m u l a t e p lan t growth d i r e c t l y . How w i l l t hese processes i n t e r a c t with a i r p o l l u t a n t s ? Fores t ha rves t and regenera t ion is i t s e l f a s t r e s s on t h e ecosystem which w i l l i n t e r a c t with increased po l lu tan t loading. A i r p o l l u t i o n i n f o r e s t s thus i s p a r t of a complex network of b io log ica l and s o c i a l i n t e r a c t i o n s whose i n t e g r a t e d impacts a r e almost impossible t o untangle through s ing le - fac to r a n a l y s i s .

A SCIENTIFIC APPROACH TO COMPLEXITY

There a r e some four poss ib le s o c i e t a l responses t o complex problems such a s a i r po l lu t ion . We can a t tempt t o t r e a t t h e symptoms through such means a s f e r t i l i z a t i o n o r i r r i g a t i o n , a l l e v i a t e t h e cause through emission c o n t r o l , accept t h e degrada t ion a s g r a c e f u l l y a s poss ib le , o r conver t t h e a f f e c t e d ecosystem t o one more r e s i s t a n t t o s t r e s s . Actual pol icy s o l u t i o n s will probably inc lude some combination of these .

How do we go about choosing the- appropr ia te pol icy response? One way is simply t o r e l y on t h e

judgment, hopeful ly good, of t h e people, hopeful 1y experienced, i n charge. This Is t h e common procedure. There is, however, a more organized s c i e n t i f i c approach t o complex problems with many temporal and s p a t i a l s c a l e s . This process includes e i g h t bas ic s t e p s .

1. Make a model of t h e process , based on e x i s t i n g knowledge and understanding of t h e system. The kinds of model which might be undertaken i n t h i s s t e p a r e d iscussed i n more d e t a i l below.

2. F i t t h e parameters of t h e model t o d a t a , preferably obtained from labora to ry o r f i e l d experimentation; o therwise from obse rva t iona l s t u d i e s .

3 . Val ida te t h e model. This involves comparison of model r e s u l t s with r e a l world outcomes i n systems o t h e r than those used i n f i t t i n g t h e parameters. This is a c r u c i a l but a l s o a most d i f f i c u l t s t e p , because t h e o b j e c t i v e of t h e whole modeling e x e r c i s e is o f t e n t o p red ic t responses of systems under s t r e s s e s t h a t exceed t h e range of e x i s t i n g v a l i d a t i o n d a t a .

4. Test t h e s e n s i t i v i t y of t h e model t o parameter changes. This can h e l p t o l o c a t e c r i t i c a l f e a t u r e s where b e t t e r understanding o r more accura te data a r e needed. It can a l s o h e l p l o c a t e p a r t s of t h e system where r e l a t i v e l y small changes may have l a r g e e f f e c t s . S e n s i t i v i t y a n a l y s i s is o f t e n s a i d t o be one of t h e g rea t v i r t u e s of a modeling approach, i n t h a t i t l eads t o d i r e c t i n g l imi ted resources t o a r e a s where they w i l l do t h e most good, o r conversely avoids t h e expendi ture of e f f o r t on measures u n l i k e l y t o have much e f f e c t . P o i n t s of s p e c i a l s e n s i t i v i t y a r e of t e n hard to f i n d , however. Both con t ro l theory and p r a c t i c a l exper ience a r e inc reas ing ly demonstrating t h a t many complex i n t e r 1 inked systems a r e r e l a t i v e 1 y i n s e n s i t i v e t o small changes i n one o r two v a r i a b l e s . This should come a s no s u r p r i s e t o those who have observed t h e evident r e s i l i e n c e of ecosystems under s t r e s s (Holling 1973). S e n s i t i v i t y a n a l y s i s remains, never the less , an important a p p l i c a t i o n of pol icy-or iented models.

5. Use t h e model o u t s i d e t h e ranges of s t r e s s e s previously experienced. One of t h e p i t f a l l s t h a t a l l of us have been warned t o avoid i n sc ience i s e x t r a p o l a t i o n , yet i t is j u s t because of t h e need f o r e x t r a p o l a t i o n t h a t models a r e c a l l e d f o r i n p red ic t ing ecosystem consequences of a i r p o l l u t i o n . The response of t h e model system w i l l u sua l ly need t o be es t imated under p o l l u t i o n loads g r e a t e r than those a l r eady experienced by t h a t system. Even more important is t h e time dimension. A primary goal o f t en i s assessment of t h e long-term consequences of ch ron ic o r e p i s o d i c a i r po l lu t ion . It is j u s t because of t h i s

extended t i m e dimension t h a t models a r e needed, and yet t h i s is perhaps t h e most d i f f i c u l t element i n t h e i r cons t ruc t ion .

6. Array t h e output f o r publ ic d iscuss ion. S ince t h e purpose of t h e models we a r e cons ide r ing h e r e is t o h e l p i n a r r i v i n g a t some s o r t of consensus about appropr ia te s o c i e t a l response, p resen ta t ion must go beyond the immediate s c i e n t i f i c community. Seldom, i f ever , w i l l t h e output of a r e a l i s t i c a i r p o l l u t i o n model lead t o d e t e r m i n i s t i c p red ic t ions . Rather, t h e r e w i l l be a range of a l t e r n a t i v e outcomes, each with a p robab i l i ty l eve l a t tached. It is no to r ious ly d i f f i c u l t t o i n t e r p r e t r i s k p r o b a b i l i t i e s i n terms of publ ic a t t i t u d e s . There is a growing l i t e r a t u r e on p r o b a b i l i s t i c r i s k assessment which is highly p e r t i n e n t t o t h e a i r p o l l u t i o n problem (e.g., Kates 1978, S t a r r and Whipple 1980).

7. Amalgamate with output of o t h e r r e l evan t models of s o c i e t a l i s s u e s f o r f i n a l publ ic eva lua t ion . A i r p o l l u t i o n i s only one of many problems fac ing soc ie ty . Measures t aken t o a l l e v i a t e t h e consequences of a i r p o l l u t i o n a r e l i k e l y t o ramify i n t o many o t h e r a s p e c t s of s o c i e t y . I n my view, t h e most important s i n g l e use of a policy-oriented model is a s an a id i n avoiding suboptimization. By subopt imiza- t i o n , of course , is meant choosing what is c l e a r l y and l o g i c a l l y t h e best s o l u t i o n t o a smal l p a r t of a problem without adequately consider ing t h e impact of t h a t s o l u t i o n on t h e t o t a l system. An example of how subopt imizat ion along a narrow path may t u r n out t o be not j u s t s l i g h t l y wrong, but e x a c t l y wrong i n a broader context is t h e d i s p o s a l of chemical wastes a t Love Canal, N. Y. Out-of - s i g h t , out-of -mind bur ia l was a good s o l u t i o n a t t h e t ime f o r t h e p o t e n t i a l hazard t o workers and t h e publ ic of t h i s m a t e r i a l ; i ts consequences a r e now a f f e c t i n g a l l Americans, a s taxpayers , i f not a s r e c i p i e n t s of d i r e c t chemical i n s u l t . Less extreme cases of subopt imizat ion may be more d i f f i c u l t t o i d e n t i f y before a c t i o n is taken. I f a proper ly designed model, by explor ing a wider range of a l t e r n a t i v e s than can t h e human mind a lone, he lps t o avoid t h e long-term c o s t s of subopt imizat ion, t h e e f f o r t i n its cons t ruc t ion w i l l be well rewarded.

8. Move toward a dec i s ion . There is no hope t h a t a d e c i s i o n , even i f based on t h e best conceivable model, w i l l s a t i s f y a l l i n t e r e s t e d p a r t i e s i n a con t rovers i a l i s s u e . One could expect , however, t h a t t h e d e c i s i o n would be more r a t i o n a l than i f based on emotion and maximization of each p a r t i c i p a t i n g i n d i v i d u a l ' s personal o b j e c t i v e s .

KINDS OF POLICY-ORIENTED MODELS

Models may be merely conceptual and verbal--an i n t u i t i v e , poss ibly q u i t e accura te , v i s u a l i z a t i o n of how t h e world works. We a r e concerned h e r e , however, with mathematical models a b l e t o deal with i n t e r a c t i o n s among more v a r i a b l e s than t h e unaided human mind can r e a d i l y handle. These a r e of severa l bas ic kinds, which d i f f e r i n both t h e i r underlying s t r u c t u r e and t h e i r range of app l i ca t ion . (This s e c t i o n owes much t o d i scuss ions with W. R. Emanuel , Environmental Sciences Divis ion, Oak Ridge National Laboratory . )

1. Empirical time series a n a l y s i s . The emphasis h e r e i s on a n a l y s i s of t h e s e c u l a r t r end of t h e v a r i a b l e s of i n t e r e s t . It is assumed t h a t t h e processes dur ing t h e period of record w i l l cont inue over t h e i n t e r v a l of ex t rapo la t ion . A t ime s e r i e s model need not inc lude e x p l i c i t casual r e l a t i o n s h i p s . It must, however, incorpora te s u f f i c i e n t da ta t o e s t a b l i s h t h e s t a t i s t i c a l s i g n i f i c a n c e of t h e observed pa t t e rns . I n t h e words of Dennis Meadows (1975), i t is "data r i c h , theory poor. "

Such a time s e r i e s a n a l y s i s is o f t e n i d e a l f o r dec i s ions which must be made immediately but which can be revoked i n t h e l i g h t of new informat ion without l a s t i n g damage, b i o l o g i c a l , o r p o l i t i c a l . Time s e r i e s a n a l y s i s has t h e advantage t h a t i t is e a s i l y understood by d e c i s i o n makers who a r e not a n a l y t i c a l l y inc l ined . It i s i n h e r e n t l y a short-term t o o l , however. Lack of e x p l i c i t casual r e l a t i o n s h i p s makes e x t r a p o l a t i o n even more r i s k y than with o t h e r models.

2. Deta i led s t ruc tu ra l - func t iona l models. These incorpora te t h e s t r u c t u r e and func t ion of t h e system t o t h e ex ten t t h a t it is known. There is a wide v a r i e t y of suggested procedures and approaches f o r cons t ruc t ing such models; seve ra l a r e discussed i n t h i s volume. The emphasis throughout is on unders tanding r e l a t i o n s h i p s and processes , no t t r ends . I n Meadows' (1975) words, they a r e "theory r i c h , d a t a poor."

Their p r inc ipa l va lue is a s an a i d t o understanding r e l a t i o n s h i p s among components and t h e s i g n i f i c a n c e of In te rconnec t ions . They a r e o f t e n useful f o r point ing out t o d e c i s i o n makers why c e r t a i n r e l a t i o n s h i p s whose importance is not i n t u i t i v e l y obvious a r e a c t u a l l y more s i g n i f i c a n t than they seem.

Proper1 y const ructed func t iona l models can lead t o p r e d i c t i o n of ecosystem responses t o s t r e s s e s , which a r e l i k e l y t o d i f f e r markedly from those of ind iv idua l organisms t e s t e d i n i s o l a t i o n . West and o t h e r s (1980) used a model of success ional dynamics t o t e s t t h e long-term impact of a i r p o l l u t i o n on e a s t e r n deciduous f o r e s t s . Their model predic ted

enhanced growth of some spec ies d e s p i t e provides a q u a n t i t a t i v e framework f o r t h e po l lu tan t stress, s i n c e they may ga in a t a s k faced by a l l dec i s ion makers, t h a t of compet i t ive advantage because they a r e l e s s achieving an acceptable compromise among a s e n s i t i v e than o t h e r s p e c i e s with which they i n t e r a c t i n t h e success ional process.

s e t of competing o b j e c t i v e funct ions . The va r ious a n a l y t i c a l techniques used f o r t h i s purpose agree i n using t h e model t o o f f e r

Neither eco log ica l models, nor ecological t r adeof f funct ions of some kind t o t h e theory i n genera l , dea l well with s p a t i a l dec i s ion maker. But h e , not t h e model o r t h e dynamics i n f o r e s t s . Most emphasis has been modeler, e s t a b l i s h e s p r i o r i t i e s among t h e on success ional dynamics over time a t a point planning c r i t e r i a . The model is thus j u s t o r i n a small a rea . There have been one more too l f o r bringing p r e c i s i o n i n t o t h e a t t empts , a s by Shugart and o t h e r s (1973) t o model t h e "flow" of one form of land use o r

planning process and f o r eva lua t ing t h e consequences of a l t e r n a t i v e choices .

v e g e t a t i o n cond i t ion t o ano the r , but t h i s approach is c h i e f l y usable f o r very l a r g e u n i t s . Because a i r p o l l u t i o n is both s p a t i a l l y extended and s p a t i a l l y v a r i a b l e , t h e r e is a need t o incorpora te these f e a t u r e s i n t o eco log ica l models of a i r po l lu t ion . A promising approach seems t o be t h e l ink ing of e x i s t i n g f o r e s t success ion models with ca r tograph ic models developed by geographers

Ecological pol icy models would be s u b s t a n t i a l l y improved i f they could d i r e c t l y incorpora te human d e c i s i o n making i n response t o ecosystem change. Act ive research is i n progress t o make t h i s poss ible . For i n s t a n c e , C. L. Smith, J. M. S tander , and A. V. Tyler (personal communication 1980), of Oregon S t a t e Unive r s i ty , an an th ropo log i s t , an ecosystem modeler, and a

f o r dynamic map ana lys i s . E f f o r t s t o do t h i s a r e now underway i n severa l research u n i t s . The r e s u l t s should be va luab le f o r a i r

f i s h e r i e s b i o l o g i s t , have co l l abora ted i n developing an i n t e r a c t i v e model of a mythical human hunt ing and ga the r ing s o c i e t y and an exp lo i t ed

p o l l u t i o n s t u d i e s . f i s h e r y . Human p a r t i c i p a n t s a r e faced with a l t e r n a t i v e s which f o r c e them t o make choices . The

Desp i t e t h e i r g r e a t va lue f o r many purposes, consequences of t h e choices a r e then evaluated by however, d e t a i l e d s t ruc tu ra l - func t iona l t h e models i n accordance with previous1 y developed models a r e u s u a l l y u n s u i t a b l e f o r deciding dec i s ion r u l e s . They found t h a t dec i s ion making i n upon s p e c i f i c a c t i o n s o r p o l i c i e s . Small s imulat ions d id a l t e r model outcomes. e r r o r s , e i t h e r i n t h e o r e t i c a l underpinnings Decisionmaking i n t h e f i s h e r y s imula t ion led t o a o r i n parameter e s t ima t ion , can lead t o s t a b l e equi l ibr ium; without i t , t h e r e was pe r iod ic q u a n t i t a t i v e p red ic t ions t h a t t u r n out t o be cycl ing of f i s h i n g v e s s e l s and f i s h biomass. Wrong q u i t e wrong when t e s t e d aga ins t t h e l imi ted v a l i d a t i o n d a t a usua l ly a v a i l a b l e . We can hope, though, t h a t improvement i n both

dec i s ions , though, led t o extinction-economic e x t i n c t i o n of t h e f i s h e r y before b io log ica l e x t i n c t i o n of t h e f i s h . S imi la r i n t e r a c t i v e

modeling technique and i n b io log ica l and modeling ideas a r e being developed by Hol l ing s o c i a l knowledge w i l l lead t o func t iona l (1978) and h i s a s s o c i a t e s and fol lowers under t h e models t r u l y use fu l a s d e c i s i o n t o o l s . r u b r i c of Adaptive Environment Assessment.

3. Aggregated pol icy-orient ed models. Here, t h e r e is an attempt t o combine t h e many DESIRABLE CHARACTERISTICS OF MODELS s t r u c t u r a l elements of t h e system i n t o a r e l a t i v e 1 y few we1 1-understood components f o r To be e f f e c t i v e t o o l s f o r a s s i s t i n g i n po l i cy which good cause and e f f e c t da ta e x i s t . The major s t r u c t u r a l and func t iona l r e l a t i o n s h i p s

d e c i s i o n s , models should have severa l c h a r a c t e r i s t i c s (Cooper 1976). It is almost

a r e preserved, but a t a lower l e v e l of t o t a l l y i r r e l e v a n t i n t h i s context whether t h e r e s o l u t i o n with r e spec t t o t h e i r model uses d i f f e r e n t i a l o r d i f f e r e n c e equat ions o r in te rconnec t ions . F u l l understanding of t h e whether i t is w r i t t e n i n FORTRAN o r BASIC. There complex system is t raded f o r g r e a t e r computational t r a c t a b i l i t y , and a g r e a t e r p o s s i b i l i t y of showing time s e r i e s d a t a .

a r e more fundamental f e a t u r e s which determine whether a model i s l i k e l y t o be accepted and used i n decisionmaking.

With t h i s s o r t of model i n hand, s c i e n t i s t s 1. It should be ex tens ive ly and c l e a r l y can i n t e r a c t wi th d e c i s i o n makers i n a documented. How was t h e model developed and q u a n t i t a t i v e way t o prepare an a r r a y of what a r e i ts assumptions? This should be a l t e r n a t i v e a c t i o n s and t h e i r probable ev iden t , i f not t o t h e u l t ima te u s e r , a t consequences. Various t o o l s of opt imizat ion, l e a s t t o those who might s e r v e a s t echn ica l a n a c t i v e a r e a of c u r r e n t r e sea rch , come i n t o consu l t an t s . Unfor tunate ly , t h i s is a play here . P a r t i c u l a r l y va luab le i n a problem with a s many c o n f l i c t i n g va lue judgments a s e f f e c t s of a i r p o l l u t i o n may be

s e r i o u s weakness of most models. This a r i s e s p a r t l y from funding limitations--documents-t i o n is an obvious th ing t o skimp i f t h e

t h e m u l t i p l e o b j e c t i v e op t imiza t ion budget has t o be c u t . I suspect t h a t not ex tens ive ly used i n eva lua t ing water resource i n f r e q u e n t l y , though, t h e r e i s a wish, maybe development a l t e r n a t i v e s (Cohon and Marks subconscious, t o keep what t h e modeler did t o 1975). This is a planning concept which himself . A f t e r a l l , knowledge is power.

Its r e s u l t s should be understandable--s u r p r i s i n g , perhaps, but not incomprehensible. F o r r e s t e r (1971), i n a widely quoted a r t i c l e , discussed t h e c o u n t e r i n t u i t i v e n a t u r e of s o c i a l systems, and prescr ibed computer modeling a s an a n t i d o t e . But F o r r e s t e r was a b l e t o exp la in q u i t e c l e a r l y how he obtained h i s c o u n t e r i n t u i t i v e r e s u l t s (o thers d i sagree with h i s a n a l y s i s , but t h a t is i r r e l e v a n t h e r e ) . He would have had no credence whatever i f he had not been a b l e t o provide such explanat ion.

3. The l i m i t s and probable range of e r r o r s should be w e l l explained. Few computer models y i e l d d e t e r m i n i s t i c r e s u l t s , and a l l a r e l imi ted i n t h e i r accep tab le degree of e x t r a p o l a t i o n . This is o f t e n not well understood by t h o s e not a n a l y t i c a l l y i n c l i n e d ; i t needs t o be made c l e a r .

4. The model should be f l e x i b l e enough t o deal wi th problems t h a t had not been f u l l y a n t i c i p a t e d , but a general al l-purpose model i s not a d e s i r a b l e goal . Senator S. I. Hayakawa's dictum, "The map is not t h e t e r r i t o r y ," although made i n q u i t e another context i n h i s r o l e a s a semant ic i s t , is wholly a p p l i c a b l e t o modeling. A model i s a map t h a t t e l l s us how t o get from one place t o ano the r , even t o some places we had not o r i g i n a l l y intended t o v i s i t . It cannot reproduce every f e a t u r e of t h e system and still r e t a i n its use fu lness a s a guide.

5. The r e s u l t s should be d isplayed i n an e f f e c t i v e and unders tandable manner. TOO o f t e n model r e s u l t s a r e presented a s arcane and incomprehensible p r in tou t . T e r r i t o r i a l de fens iveness again? Resu l t s need t o be presented i n a form comprehensible t o those who r e a c t t o graphs r a t h e r than t o columns of f i g u r e s , t o p i c t u r e s r a t h e r than t o equa t ions . Visual p resen ta t ion almost never r e c e i v e s enough a t t e n t i o n .

6. The model should be portable--usable on o t h e r computers with a minimum of reprogramming. I have t h e f e e l i n g t h a t incompat ib i l i ty has become worse i n r ecen t years . This w i l l presumably c o r r e c t i t s e l f even tua l ly , but f o r now i t is a s e r i o u s problem.

CONCLUSIONS

The impact of a i r p o l l u t i o n on f o r e s t s , e s p e c i a l l y when combined with o t h e r s t r e s s e s , has b i o l o g i c a l , s o c i a l , and p o l i t i c a l impl ica t ions which opera te a t s e v e r a l time s c a l e s extended over space. The unaided human mind is not well adapted t o explore t h e consequences of each of t h e l a r g e number of poss ib le combinations of va r i ab les . Therefore , some s o r t of computer model is v i r t u a l l y e s s e n t i a l i f t h e most reasonable a r r a y of a l t e r n a t i v e s is t o be presented f o r r a t i o n a l choice .

A polIcy-oriented model is not a d e c i s i o n maker. It is an a i d t o informed decisionmaking. I f i t is t o func t ion e f f e c t i v e l y i n t h a t r o l e , t h e r e needs t o be mutually suppor t ive i n t e r a c t i o n s among modelers, b iological and s o c i a l s c i e n t i s t s , and dec i s ion makers.

A modeler deal ing with eco log ica l pub l i c pol icy quest ions r e l a t e d t o a i r p o l l u t i o n i n f o r e s t s needs t h e knowledge of a b i o l o g i s t , t o understand t h e essence of t h e mechanisms by which a i r p o l l u t i o n a f f e c t s b io log ica l processes . He needs t h e s k i l l s of an appl ied mathematician, t o understand t h e s t r u c t u r e of t h e model and i t s impl icat ions , and usua l ly t o d i r e c t t h e programmers preparing t h e ac tua l computer code. Most important, he needs t h e pat ience and i n t e r p e r s o n a l a b i l i t i e s of a diplomat, t o persuade t h e b i o l o g i s t and t h e deic ison maker a l i k e t h a t he is he lp ing them t o do t h e i r job b e t t e r , and not usurping t h e i r l e g i t i m a t e r o l e s .

Biological and s o c i a l s c i e n t i s t s dea l ing wi th modelers need t o recognize t h a t modelers a r e t h e r e t o h e l p them, not v i c e ve r sa . A good model, properly presented, w i l l u sua l ly provide t h e d e c i s i o n maker with a f u l l e r exp lana t ion of t h e consequences of a l t e r n a t i v e pol i c i e s t h a n w i l l unaided s c i e n t i f i c s ta tements o r p o s i t i o n papers. Thus, t h e s c i e n t i s t may be b e t t e r a b l e t o get h i s p o i n t s ac ross through t h e medium of a we1 1-constructed and we1 1-presented model .

Decision makers should r e a l i z e t h a t a good model is pr imari ly a means f o r exp lo r ing t h e consequences of a l t e r n a t i v e po l i cy cho ices of nea r ly equal rank. I f t h e model shows one o r two choices t o be s o super io r t o o t h e r s t h a t only they should be considered, t h i s w i l l s u r e l y be obvious t o competent a n a l y s t s i n t h e absence of a model. The r e a l u t i l i t y of a pol icy-or iented model is t o explore those s i t u a t i o n s where t h e r e are a l a r g e number of a1 t e r n a t ives which a r e " n e i t h e r a11 good nor a l l bad. The broader t h e a r r a y of cho ices s e t up f o r exp lo ra t ion , t h e g r e a t e r t h e f i n a l range of o p p o r t u n i t i e s w i l l be.

F i n a l l y , I suggest t h a t t h e g r e a t e s t v a l u e of a modeling approach t o e c o l o g i c a l problem s o l v i n g may be i ts s t imulus t o exchange of in fo rmat ion among d i s c i p l i n e s and among p r a c t i t i o n e r s . mentioned, e a r l i e r , t h e r e l a t i v e l y u n s a t i s f a c t o r y incorpora t ion of s p a t i a l dynamics i n f o r e s t models. Unt i l a few yea r s ago, t h i s would have been t r u e of environmental biology general1 y. There have been recen t s i g n i f i c a n t advances, though, i n dea l ing with s p a t i a l he te rogene i ty i n i n s e c t d i s p e r s a l and i n dynamics of marine plankton. I n taxonomically o r i en ted sc ience , such advances t a k e a long t ime t o come t o t h e a t t e n t i o n of workers i n adjacent f i e l d s . The f a c t t h a t modeling approaches tend t o c r o s s taxonomic boundaries seems l i k e l y t o cut t h i s unnecessary t ime lag . This a lone would be adequate j u s t i f i c a t i o n f o r wider use of modeling i n a complex i n t e r d i s c i p l i n a r y f i e l d such a s t h e e f f e c t of a i r p o l l u t a n t s i n f o r e s t s .

I

LITERATURE CITED

Cohon, J. L., and D. H. Marks 1975. A review and eva lua t ion of mul t iob jec t ive

programming techniques . Water Resour. Res. 11:208-220.

Cooper, Char les F. 1976. Ecosystem models and environmental

policy. Simulation 26:133-138.

F o r r e s t e r , J. W . 1971. Coun te r in tu i t ive behavior of s o c i a l

systems. Tech. Review 73(3):53-68.

Hol l ing , C. S. 1973. Res i l i ence and s t a b i l i t y of ecological

systems. Ann. Rev. Ecol. Systematics 4: 1-23.

Ho l l ing , C. S. [Ed.] 1978. Adaptive environmental assessment and

management. Wiley Inter-Science, Chichester , U . K . 377 pp.

Kates, Robert W. 1978. Risk assessment of environmental

hazard (SCOPE 8) . John Wiley and Sons, New York, 112 pp.

b u c k s , Orie 1980. Acid r a i n : l i v i n g resource impl i ca t ions

and management needs. Trans. 45th North Amer. Wi ld l i f e Nat. Res. Conf. [ I n p res s ]

Meadows, Dennis 1975. A c r i t i q u e of short-term pe r spec t ives

i m p l i c i t i n most resource models. I n Mineral Mate r i a l s Modeling: A state-of-the-art Review. W. A. Vogely, ed. , pp. 66-80.

Shugart , H. H. , Jr., T. R. Crow, and J. M. Hett 1973. Fores t success ion models: a r a t i o n a l e

and methodology f o r modeling f o r e s t success ion over l a r g e regions. Fores t Sci . 19:203-2 12.

S t a r r , Chauncey, and Chr is Whipple 1980. Risks of r i s k dec i s ions . Science

206: 1114-1119.

West, D . C. , H. B. McLaughlin, and H. H. Shugart 1980. Simulated f o r e s t response t o chronic a i r

p o l l u t i o n s t r e s s . J. Env. Q u a l i t y 9:43-49.

Historical Perspectives and International Concerns About Air

Pollution Effects on Forests1

Edwin Donaubauer 2

Abstract: Air pollution from man's activities has a long history; real hazards for forest vegetation occurred more than a century ago which marked the starting point of forest research in the field. The objectives of research have been subject to a steady metamorphosis from simple causal relationships to the task of investigating the long-term influence of pollutant mixtures on trees directly and on entire ecosystems. The IUFRO Subject Group S2.09, Air Pollution, encourages interdisciplinary work in the field and offers an organizational home for close cooperation on an international basis. The consideration of air pollution effects on forest ecosystems goes far beyond limited forest interests, the findings can provide fundamental data on the deterioration of the human environment.

Some forest insect pests develop outbreaks is still in high demand as an energy source, and characterized by high insect population den- in fact is still the most important source for sities that use up the food resource represented over 90 percent of the world's population. Col-by the host species. The direct damage by in- lection of fuel wood and the harvesting of sects and the predisposition of weakened trees timber for many uses have influenced the ex- to certain diseases both result in a serious tension and quality of forests over long per- degradation or even destruction of the local iods of prehistoric and historic time. All forest environment. these activities had, at least in some major

To some extent man-made air pollution prob- regions of the globe, serious consequences for lems show some similar aspects. In many re- the ecosystem and human environment. We are gions of the world mankind cleared the forests reminded of the historical fact, that 2000 years for agriculture, for settlements, for roads, ago forests existed around the Mediterranean for mining, for outdoor recreation, etc. Wood Sea and protected large and prospering ag-

ricultural areas in North Africa, where de- serts are now present. These were direct influences, but among others an additional indirect threat developed by the quick progress

Presented at the Symposium on Effects of Air in technology and by increasing quantities Pollutants on Mediterranean and Temperate Forest and numbers of toxic substances released into Ecosystems, June 22-27, 1980, Riverside, the air. California, U.S.A. Certainly, man-made air pollution has been

mentioned long ago in historic times, but the '~ead, Institute of Forest Protection, dimensions of the problem have changed in re-

Federal Forest Research Institute, lation to regional economic and technical de- Vienna, Austria velopments. The effects of air pollution to Deputy Coordinator, IUFRO, Division 2 forest ecosystems were and seem still to be

underestimated, maybe for these reasons:

1

- symptoms a r e o f ten unspecif ic , o r develop l a t e and slowly, o r a r e even i n v i s i b l e (as depression of growth increment) ;

- ser ious changes i n f o r e s t ecosystems may be-come obvious only a f t e r many years of ac-cumulation of low concentrations o r amounts of tox ic substances (heavy metals, a l -ka l ine dus t s , acid r a i n ) .

- t r e e s a r e more s e n s i t i v e t o widely d i s t r i b - uted po l lu t ion than humans and t h i s d i f -ference i s not f u l l y known o r real ized.

REMARKS ON HISTORY

Perhaps Pliny (65 A.D.) was the f i r s t t o observe and descr ibe apparent Sop-damage t o vegetation surrounding a smelter. Later on we find references f requent ly i n documents of the Middle Ages concerning a i r po l lu t ion by coal burning; i n general people of higher so-, c i a 1 c lasses f e l t inconvenienced. Especially i n such repor t s from England and Central Europe persecutions happened even a t tha t time i f a i r po l lu t ion was caused i n a prohibited area o r time.

A i r po l lu t ion became more than a l o c a l and occasional a f f a i r when i n d u s t r i a l i z a t i o n and the use of f o s s i l energy resources increased rapidly i n Western and Central Europe during the past century. By the time f o r e s t research i n s t i t u t e s and f o r e s t f a c u l t i e s were estab-l ished - more than a hundred years ago - they had severa l repor t s of p r i o r experience and observations of b o t a n i s t s t o draw upon. There-fore f o r e s t research was stimulated t o pay a t -t en t ion t o a i r po l lu t ion problems from the beginning. The present research pro jec t s provide numerous publ icat ions on a i r po l lu t ion e f f e c t s .

CHANGING AIMS AND TASKS

The ob jec t ives of research pro jec t s con-centrated f i r s t on sulphur dioxide including methods f o r de tec t ion and evaluat ion of a i r po l lu t ion damage. Among these e a r l y works we find very forward-looking ones, a s Rusnov' s (1919) study about the inf luence of 'ac id r a i n ' ( t h i s term was introduced much l a t e r ) on f o r e s t s o i l s . Several authors proved the use of chemical ana lys i s of fo l i age f o r de- t ec t ion and evaluat ion of a i r po l lu t ion (SO2, HF) and i t s e f f e c t s on f o r e s t stands. These publ icat ions caused long l a s t i n g discussions and s t imulated f u r t h e r inves t iga t ions ; how-ever, many years passed u n t i l the chemical ana lys i s of fo l i age (needles) became a useful too l fo r a g rea t number of cases. Step by s tep the method was re f ined , so t h a t today s u f f i c i e n t knowledge i s a v a i l a b l e f o r proper sampling, and the thresholds of n a t u r a l s u l f u r and f luor ine contents and t h e i r v a r i a t i o n a r e b e t t e r defined.

Certa inly , s u l f u r dioxide i s s t i l l t h e pollu tant occurring over l a r g e s t a r e a s , but t h e l i s t of substances thus f a r i d e n t i f i e d a s re -sponsible f o r damage t o f o r e s t t r e e s becomes longer and longer. More a t t e n t i o n i s now given

t o ind i rec t and chronic e f f e c t s of a c i d i c o r a l k a l i n e p rec ip i t a t ion and heavy metals on f o r e s t ecosystems.

Formerly, the i n t e r e s t of f o r e s t research concentrated on a s ing le -po l lu tan t - s ing le - t ree species re la t ionship. Today, increased e f f o r t s a r e invested i n e luc ida t ing the complex influences on f o r e s t ecosystems and studying the in te rac t ion of po l lu tan t mixtures which occur i n many cases.

Regional inves t iga t ions on a i r pol luted f o r e s t zones use a l l a ss i s tance of modern technology, such a s remote sensing combined with physiological, chemical and t r e e men-sura t ion methods f o r v e r i f i c a t i o n .

Forest a i r po l lu t ion problems a r e l inked with the economic standard i n general and with c e r t a i n i n d u s t r i a l development.

But i t i s not necessa r i ly so, t h a t only point sources of a i r po l lu t ion o r concentra-t ions of i n d u s t r i e s cause ser ious problems. Automobile t r a f f i c o r even a s i n g l e source area can under s p e c i f i c o rogra f ic and meteor-ologic condi t ions lead t o po l lu tan t accumu-l a t i o n and perhaps t o heavy damage. Further , we a r e learning more about long d i s tance pol- l u t a n t t r anspor t over hundreds and thousands of kilometers.

The experience i n nat ions with highly de-veloped industry makes i t advisable t o s t i m -u l a t e more i n t e r e s t i n t h i s f i e l d of research i n many developing countr ies i n the world. F i r s t of a l l the experiences of o thers should be transmitted and applied i n a l l planning f o r economic development t o avoid the same h i s t o r i c a l lessons received by many developing countr ies . There a r e many f o r e s t research workers and i n s t i t u t i o n s i n North America, Europe (including t h e A s i a t i c p a r t of USSR), and Japan who a r e experienced with the var ious aspects of a i r po l lu t ion e f f e c t s on f o r e s t ecosystems and could provide s c i e n t i f i c in -formation and ass i s tance .

I U F R 0 AND AIR POLLUTION RESEARCH

The In te rna t iona l Union of Forest Research Organizations (IUFRO) has s i x major organi- za t iona l divis ions . Division 2 , 'Forest Plants and Forest Protect ion ' i s home f o r t en Subject Groups, one of which i s S2.09 - ' A i r Pollution. ' The titles of the various Working P a r t i e s e lucidate . the i n t e r d i s c i p l i n a r y scope: Researchers a r e included from the f i e l d s of f o r e s t mensuration, s o i l sc ience, pathology, remote sensing, t r e e physiology, e tc . They work together , and exchange research r e s u l t s t h a t s t imulate t h e i r f u r t h e r research. This IUFRO Subject Group has a long h i s t o r y of a c t i v i t y . For more than a quar te r of a century meetings have brought together an increasing number of pa r t i c ipan ts . A few western and c e n t r a l European countr ies were represented a t f i r s t ; now more countr ies from eas te rn and southern Europe a r e represented too, a s wel l a s a slowly increasing number of pa r t i c ipan ts from Canada and the U.S.A. The eleventh meeting of a l l Working P a r t i e s w i l l

be held this year in Graz, Austria and previous conferences were hosted by nine other European countries. It is somewhat disappointing that the group met only once in another continent: Gainesville, Florida, U.S.A. at the occasion of the IUFRO Congress in 1971. We expect to have a meeting at the occasion of the 1981 IUFRO Congress in Japan.

The interdisciplinary scope of all Subject Group meetings makes them attractive to a certain group, seldom represented at such scientific conferences. We could characterize this group as 'consumers' of research results including: forest managers, representatives from industries, and sometimes politicians. There are of course some difficulties in accommodating the needs of each group, but I consider the interest in such meetings as an expression for a demand to receive the information from the scientists directly and not via more traditional channels, i.e., technical publications. I feel we should think of possibilities for such direct information flow in specific fields like air pollution where we find more and more vital interest from the public.

I feel that this international symposium sets the stage for new conceptualizations by placing the view of effects of air pollutants on forest ecosystems into the center of the de- liberation. The discussions here should stimulate further research and interdisciplinary, international cooperation.

In addition I will emphasize that air pollution effects on forests are not only a question for researchers or foresters, but of fundamental interest to mankind. That may seem overstated but forest ecosystems demonstrate due to the long rotation periods the dynamics and the consequences of long-term influences on complex ecosystem-level processes. Various pollutant effects that are dangerous not only to the forests themselves, as an important resource, but also as an invaluable part of the human environment can be predicted by ecosystem-level research. In this sense one can consider the forest ecosystems as sensitive warning systems for the vital, fundamental interests of life.

Natural Influences of Forests on Local and Regional Air Quality

Emissions and Air Resource Management Within Forests '

2Michael A. Fosberg and H o l l i s Record

Abstract : Subs tan t i a l por t ions of t h e emissions inventory wi th in fo res ted lands a r e from dispersed i n t e r m i t t e n t sources . Chief sources a r e smoke from w i l d f i r e and pre-sc r ibed f i r e , emissions as soc ia ted with concentra ted rec-r e a t i o n and second-home developments , and f u g i t i v e dus t from unpaved roads and e o l i a n s o i l s . E f f e c t s of smoke on f l o r a range from reduced photosynthet ic e f f i c i e n c y a t low dosages t o t i s s u e n e c r o s i s a t high dosages. E f f e c t s on fauna a r e not c l e a r l y def ined. Effect of smoke on s o c i a l va lues , pr imari ly v i s i b i l i t y , is recognized but not under-s tood. Dispers ion process i n complex t e r r a i n , t h e physio-graphic s e t t i n g f o r most fo res ted lands , i s complicated by topography and s p a t i a l l y varying wind f i e l d s , a h igher degree of anisot ropy of turbulence, and a wider range of tu rbu lence i n t e n s i t i e s than found over l e v e l ground. Management of a i r resources wi thin fo res ted a r e a s is l i m i t e d t o land management planning a c t i v i t i e s because of t h e complexi t y of emission c h a r a c t e r i s t i c s , d i spe r s ion processes , and e f f e c t s of p o l l u t a n t s from wi th in f o r e s t sources .

Much of t h i s symposium t r e a t s e f f e c t s of pol- s i o n s from f i r e a r e Con, CO, p a r t i c u l a t e s , and l u t a n t s from major s t a t i o n a r y sources on eco- hydrocarbons. Recreat ional and second-home devel-systems. S i g n i f i c a n t p o l l u t a n t s t r e a t e d i n o t h e r opments emit C O , CO, p a r t i c u l a t e s , and hydro-papers a r e n i t r o u s oxides , oxides of s u l f u r , reac- carbons from f i r e p l a c e s and campfires; SO2 and NOx t i v e hydrocarbons, and t h e photochemical der ived from dispersed t r a n s p o r t a t i o n systems--namely, p o l l u t a n t , ozone. E f f e c t s of NOn, SO2, and On a r e p r iva te automobiles. Fug i t ive dust from unpaved we l l documented i n t h e companion papers i n t h i s roads and e o l i a n s o i l s a l s o c o n t r i b u t e t o t h e volume. p a r t i c u l a t e loading.

P o l l u t a n t s from wi th in f o r e s t sources a l s o E f f e c t s of t h e above p o l l u t a n t s , p a r t i c u l a r l y inc lude emission from w i l d f i r e , prescr ibed f i r e , smoke, f l o r a , fauna, and s o c i a l values a r e poorly unpaved roads , e o l i a n s o i l s , concentra ted recrea- understood. Documented e f f e c t s range from reduced t i o n , and second-home developments, Chief e m i s - photosynthet ic a c t i v i t y through blockage of s o l a r

r a d i a t i o n t o t i s s u e nec ros i s . E f f e c t s on micro-organisms range from i n h i b i t i o n of some spores and fungi t o increased germination of one fungus.

p r e s e n t e d a t t h e Symposium on E f f e c t s of Ai r E f f e c t s of smoke on fauna a r e documented, but with-P o l l u t a n t s on Mediterranean and Temperate Fores t out explanat ion. Ecosystems, June 22-27, 1980, R ive r s ide , C a l i f o r n i a , U.S.A. V i s i b i l i t y is both a physical and s o c i a l value .

V i s i b i l i t y can be quan t i f i ed i n terms of v i s u a l 2 ~ r o j e c t Leader, Fores t and Brushland Meteorol- range and a b i l i t y t o d e f i n e d e t a i l s a t s p e c i f i e d

ogy, P a c i f i c Southwest Fores t and Range Experiment d i s t ances . V i s i b i l i t y is a l s o a personal va lue S t a t i o n , Fores t Se rv ice , U.S. Department of Agri- based on pas t and expected experiences. A r ecen t c u l t u r e , Berkeley, C a l i f . , s t a t i o n e d a t Rivers ide , popular country and western song (McCall and o t h e r s C a l i f . ; and Geo log i s t , Los Padres Nat ional , Fores t , 1976) goes "..... One of t h e guys from New York Fores t Service , U.S. Department of Agr icu l tu re , s a i d 'Hey, look a t t h e smog i n t h e sky, smog c l e a r Goleta , C a l i f . out h e r e i n t h e s t i c k s ' . Someone s a i d , 'Hey J o e ,

t h a t ' s not smog, t h a t ' s t h e Milky Way', Joe had never seen t h e Milky Way ...." Contras t Joe ' s r e a c t i o n t o t h a t of a r e s iden t of t h e Four Corners a rea of Utah v i s i t i n g any urban a r e a i n t h e world on a c l e a r a i r day. Local r e s i d e n t s would comment on t h e c l a r i t y of t h e a i r , but t h e v i s i t o r would n o t i c e t h e impairment of v i s i b i l i t y .

The r e l a t i o n s h i p between a source of p o l l u t i o n and t h e ef f e c t of t h a t po l lu tan t on Mediterranean and temperate f o r e s t ecosystems is through dis-pe r s ion of t h e p o l l u t a n t between t h e source and t h e recep to r point . Nearly a l l d i s p e r s i o n c a l c u l a t i o n s a r e based on t h e Gaussian model i n which t r a n s p o r t is t r e a t e d through d e f i n i t i o n of a mean windspeed and d i r e c t i o n and tu rbu len t d i f f u s i o n is based on a t ransformat ion of t h e turbulence s t r u c t u r e t o a Gaussian s t a t i s t i c a l d i s t r i b u t i o n (Turner 1969). Va l id i ty of t h e c o e f f i c i e n t s used i n t h e Gaussian model a r e uncer t a in i n s i t u a t i o n s where t e r r a i n f e a t u r e s a r e complex. In p a r t i c u l a r , winds a r e known t o con ta in a high degree of s p a t i a l and temporal v a r i a b i l i t y (Fosberg and o t h e r s 1980) and

3t h e tu rbu lence i n t e n s i t i e s a r e h ighly a n i s o t r o p i c . Because much of t h e Mediterranean and temperate f o r e s t ecosystems a r e found i n complex t e r r a i n throughout t h e world, t h e d i spe r s ion o r d e l i v e r y system of p o l l u t a n t s from t h e source t o t h e r e c e p t o r must account f o r complex t e r r a i n atmos- p h e r i c processes .

An understanding of each physical and b io log ica l process is necessary but not s u f f i c i e n t t o develop management p lans f o r a i r r e sources w i t h i n f o r e s t s and brushlands. Acts , laws, r e g u l a t i o n s , and codes e s t a b l i s h e d by Congress down through l o c a l county regu la to ry agencies s p e c i f y goa l s and o b j e c t i v e s f o r a i r q u a l i t y and f requen t ly s p e c i f y t h e methods i n which a i r q u a l i t y o b j e c t i v e s w i l l be met. A s example, o rgan ic a c t s of most Federal agencies i n t h e United S t a t e s r e q u i r e t h a t t h e agency p ro tec t o r preserve , o r meet a i r q u a l i t y o b j e c t i v e s . The Clean A i r Act of 1977 (U.S. Congress 1977) spec i f i-c a l l y r e q u i r e s t h a t a i r q u a l i t y o b j e c t i v e s be met through emissions c o n t r o l . Because i t is not f e a s i b l e t o i n s t a l l scrubbers on prescr ibed f i r e , emission con t ro l is achieved through emissions d e n s i t y planning.

Each of t h e following s e c t i o n s addresses t h e s p e c i f i c t o p i c s of emission c h a r a c t e r i z a t i o n , dis-p e r s i o n i n complex t e r r a i n , e f f e c t s of smoke on f l o r a , fauna, s o c i a l va lues , and a i r r e source management .

EMISSIONS FROM WITHIN FOREST SOURCES

Major emissions from w i l d f i r e and prescr ibed f i r e a r e CO CO, hydrocarbons, and p a r t i c u l a t e s .

2'

anh ham, Lucy M. 1980. Wintertime d i s p e r s i o n processes i n t h e Lake Tahoe Basins. Proc. 2nd Conf. on Appl ica t ion of A i r P o l l u t i o n Meteorology. Amer. Meteorol. Soc. [ i n p r e s s ]

Although C02 i s not a p o l l u t a n t a s such, C02 is of considerable i n t e r e s t i n a n a l y s i s of t h e global h e a t balance. Carbon dioxide emissions range from 1000 kg per me t r i c ton of fue l t o 1750 kg per me t r i c ton of fue l (Ryan and McMahon 1976), wi th extreme values nea r 1830 kg per me t r i c t o n (Vines and o t h e r s 1971).

Carbon monoxide emissions from f i r e a r e h igh ly dependent on can bust i o n e f f i c i e n c y . Values range from 17 t o 98 kg per m e t r i c t o n (Sandberg and Martin 1975, Darley and o t h e r s 1966, G e r s t l e and Kemnitz 1967). The U.S. Environmental P r o t e c t i o n Agency (1978) recommends a value of 4 5 kg per m e t r i c t o n from hemlock, Douglas-f i r , and cedar and 98 kg per me t r i c t o n from ponderosa pine. Inef f i-d e n t combustion f o r smoldering damp f u e l s have r e s u l t e d i n emissions a s high a s 250 kg per m e t r i c t o n of f u e l (Ryan and McMahon 1976). Emissions a s high a s 250 t o 400 kg per me t r i c t o n of fue l have been reported when energy r e l e a s e from f i r e is less t h a n 750 wa t t s per square meter (Sandberg and Martin 1975).

Hydrocarbon emissions range from 2 t o 7 kg per me t r i c t o n of f u e l (U.S. Environmental P r o t e c t i o n Agency 1978) although emissions a s high a s 20 kg per me t r i c t o n have been repor ted (Ryan and McMahon 1976, Darley and o t h e r s 1966). Spec ia t ion of hydrocarbons ( f i g . 1) shows s a t u r a t e d hydrocarbons (mostly methane) comprise about 30 percent a t peak f i r e i n t e n s i t y and about 15 percent a t low f i r e i n t e n s i t i e s (Sandberg and o t h e r s 1979). Low molecular weight o l o f i n e s make up about 17 percent of t h e emission from flaming f i r e and 3 percent from smoldering f i r e (Sandberg and o t h e r s 1979).

Bnissions of SO and N O a r e n e g l i g i b l e . Most x

fue l con ta ins l e s s t h a n 0.2 percent s u l f u r and com-bust ion temperatures a r e low, prevent ing formation of NOx.

P a r t i c u l a t e emissions from f i r e a r e g iven a s 2 t o 6 kg per me t r i c t o n of fue l (U.S. Environmental P r o t e c t i o n Agency 1978). A range of emissions a r e given i n t a b l e 1. P a r t i c u l a t e s i z e s a r e mainly i n t h e submicron diameter c l a s s e s with only a few p a r t i c l e s l a r g e r than a micron ( f i g . 2). Par t icu-l a t e s i z e s a r e dependent on combustion e f f i c i e n c y (Schaefer 1976) with t h e most e f f i c i e n t f i r e -producing s i z e s i n t h e r e s p i r a b l e range.

National emissions of p a r t i c u l a t e s from pre-s c r i b e d f i r e s and w i l d f i r e s a r e shown i n f i g u r e 3. Prescribed f i r e c o n s i s t s of less t h a n 20 percent of a l l f i r e emissions n a t i o n a l l y . Emissions of t h e major p o l l u t a n t s , p a r t i c u l a t e s , CO, and hydro-carbons by S t a t e and regions a r e given i n t a b l e 2 f o r prescr ibed burning.

I n a d d i t i o n t o w i l d f i r e and prescr ibed f i r e , concentra ted r e c r e a t i o n and second-home develop-ments c o n t r i b u t e smoke through f i r e p l a c e burning and more inc reas ing ly through use of wood f o r home hea t ing .

100-IOOM GLASS SCOT OV-101 20-230'Cat 4Ymln I.Sml/mIn H i

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zc furon 26A n-haptone 5 s anlwlÃ 3 n-pentaw 27 a - 2 - htptanÃ 56 2-mathyl-5-IÃ‡ÃˆprÃ3A isoprene 29 2-vinylfuran 30 ocetorr 31 2 3-dimÃ§lhyl-2

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58 n-decone 7 diacet~l 36 tOllWM 6 0 n-propyltfnzew4 8 cyclopÃ§"t<"lhn 32 2.4-dlmÃ§thylhtxo

59 camphena (tÃ§nl. 8 I - hexw 39 I-octene 8A methyl vinyl k Ã § t 4 0 2.3- dimÃ§thylhÃ§i 61 m-ethyltoluene 9 2-methylfuran 1.4-diem 62 p- ethyltoluiw 10 n-hexone 41 n-octane 15 2,4- h e x a d h 4 2 2.3.5-trimtliylfuron 6 6 I-deceni

16 1.3.5-hexatrlÃ§ 4 4 furfurol 67 benzofuron

17 3-methylbutanal 4 9 ethyl benzene 71 m-d ie thy lhzme 7 2 .lne

2 0 benzene SO p-aybne 7 7 p-a-dlrnethylÃ§tyrÃ§

21 cyclohexom 50A 2-propionylfuranftfrtJ 22 4 - methylpentaw 5 2 styrene 78 n-undccane 23 214-dlmethylixf;t(~ 53 Q-XYI~W an n-dodecona 24 I-trans-2-dimethyl-

cyclopentone

Figure IÃ‘Chromatogra of organic vapors i n l o b l o l l y p ine smoke (from Ryan and McMahon 1976).

Table I--Summary of p a r t i c u l a t e emission y i e l d s repor ted from wildland f u e l s (from Sandberg and o t h e r s 1979)

P a r t i c u l a t e s (kg per me t r i c t o n of fue l burned)

L a b l f i e l d Type of f i r e -~

Fuel type experiment Heading Backing Reference

Logging res idues F ie ld 14-53 Sand berg (1974) (Western)

Laboratory Sandberg (1974) F ie ld Radke and o t h e r s (1978) Laboratory F r i t s c h e n and o t h e r s (1970)

Landscape r e f u s e Laboratory 12 F e l d s t e i n and o t h e r s (1963)

Grass burning F i e l d 8 Boubel and o t h e r s (1969)

Live unders tory F i e l d Vines and o t h e r s (1971) (Aus t ra l i a )

Laboratory Vines and o t h e r s (1971) (Southern) F i e l d 7-15 Ward and o t h e r s (1976)

Laboratory 12-49 Ryan (1974)

Pine l i t t e r F i e l d 22-27 Ward and o t h e r s (1976) (Southern)

Laboratory 3-1 4 Ryan and McMahon (1976) Laboratory 11-63 Ryan and McMahon (1976)

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Figure 2--Particle s i z e d i s t r i b u t i o n : (A) S ing le f i r e i n four fue l types; (B) Grand Average, a l l f u e l types; and (C) Normalized d i s t r i b u t i o n , number, s u r f a c e a r e a , and volume f o r a high and low concen t ra t ion (from Ryan and McMahon 1976).

Some hydrocarbons and NO a r e a l s o emit ted from x

t r a n s p o r t a t i o n systems and p r i v a t e veh ic les i n r e c r e a t i o n a l and second-home developments.

Fug i t ive dus t from unpaved roads and e o l i a n s o i l s occas iona l ly c o n t r i b u t e s u b s t a n t i a l l y t o t h e p a r t i c u l a t e l o c a t i o n of p o l l u t a n t s , but t h i s has no t been completely q u a n t i f i e d (Singer 1980).

EFFECTS OF SMOKE ON FORESTS

Few s t u d i e s e x i s t t h a t c l e a r l y d e f i n e t h e e f f e c t s of smoke and f o r e s t b iota . E f f e c t s of smoke on micro-organisms suggest t h a t smoke reduced growth of spore germination of severa l fungal pathogens, but increased spore germination on one

fungi (Panneter and Uhrenholt 1975a, b). E f f e c t s of smoke on photosynthesis a t low dosages reduces t h e photosynthet ic r a t e by d i r e c t blockage of s o l a r r a d i a t i o n . Increased C O concen t ra t ions , however,

could inc rease carbon f i x a t i o n and photosynthet ic a c t i v i t y (Green and Wright 1977).

E f f e c t s of smoke on s o c i a l va lues , p r imar i ly v i s i b i l i t y , a r e not c l e a r l y defined. Although physical a s p e c t s of v i s i b i l i t y ; t h a t i s , v i s u a l range, maximum d i s t ance an ob jec t can be seen, and d i sc r imina t ion of d e t a i l s on a d i s t a n t ob jec t can be defined q u a n t i t a t i v e l y (Malm 1979). perceived psychological b e n e f i t s (Driver and o t h e r s 1979) of v i s i b i l i t y a r e i n t e r r e l a t e d with o t h e r demands on t h e sensory system. Paraphrasing Driver and o t h e r s (1979) a l i t t l e no i se po l lu t ion , a l i t t l e l i g h t

LEGEND: SEASON

1 - JAN 2 - APR 3 - JULY 4 - OCT

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REGIONS AND SEASONS

- MAR - JUNE - SEPT- DEC

- WILDFIRE - PRESCRIBED FIRE

Figure 3--Forest f i r e p a r t i c u l a t e production by region and season (from Ward and o t h e r s 1976).

p o l l u t i o n , a l i t t l e l o s s of open space, awareness of water p o l l u t i o n , nonbiodegradable substances , ae roso l cans and cancer , change expected va lues of v i s i b i l i t y . Referr ing t o t h e quote from a popular song used i n t h e i n t r o d u c t i o n of t h i s paper, we can ask , d i d Joe 's a t t i t u d e s toward v i s i b i l i t y change on h i s v i s i t t o Colorado, and how would those changes i n f l u e n c e h i s view of t h e New York sky l ine? The point Driver and o t h e r s (1979) a r e emphasizing is t h a t t h e perceived va lues a r e t h e r e a l va lues and t h a t t h e phys ica l ly measurable va lues of v i s i -b i l i t y a r e i n d i c e s of t h e values . In p a r t i c u l a r , s c a t t e r i n g and a t t e n u a t i o n of l i g h t is not a s o c i a l value .

DISPERSION PROCESSES I N COMPLEX TERRAIN

Wind p a t t e r n s i n complex t e r r a i n a r e h igh ly v a r i a b l e i n t ime and space. Local mountain and v a l l e y c i r c u l a t i o n s f r e q u e n t l y mask t h e large-scale p a t t e r n s such t h a t a mean t r a n s p o r t wind f o r pol-l u t a n t movement i s d i f f i c u l t t o d e f i n e (Fosberg and o t h e r s 1976a, b; Fosberg and Fox 1978). S p a t i a l v a r i a b i l i t y of winds is c l e a r l y i l l u s t r a t e d i n f i g u r e 4 over t h e Oregon Coast Range and over t h e Cascade Mountains. Con t ras t t h i s v a r i a b i l i t y with t h e uniformity of winds over t h e P a c i f i c Ocean and w i t h i n t h e Willamette Valley.

In a d d i t i o n t o mean t r a n s p o r t of p o l l u t a n t s , t u r b u l e n t d i f f u s i o n is important i n d i spe r s ing a i r

p o l l u t a n t s . The most f r equen t ly used method of quant i fying t h e d i spe r s ion process is through t h e so-called Gaussian d i s p e r s i o n model (Turner 1969) . Downwind concen t ra t ions , X , a r e r e l a t e d t o emission Q by

where u i s t h e mean windspeed and

Here, o and a a r e t h e va r i ances i n t h e Gauss- Y

i a n s t a t i s t i c a l d i s t r i b u t i o n ; y and z a r e t h e distance of t h e po l lu tan t element from t h e plance c e n t e r l i n e . The va r i ance o is r e l a t e d t o t h e tu r - bulence s t r u c t u r e through

2Kxo2 = - ( 3 )u

i n which K i s t h e eddy turbulence c o e f f i c i e n t and x i s t h e d i s t a n c e downwind from t h e source . Tradi-t i o n a l i n t e r p r e t a t i o n s of atmospheric processes t h a t were developed f o r l e v e l ground suggest t h a t t h e K ' s be defined through a n a l y s i s of t h e i n e r t i a l subrange of turbulence and t h a t t h i s mean wind is constant over s u b s t a n t i a l d i s t ances , t h i s i s , 10 ' s of km. Such assumptions a r e extremely d i f f i c u l t t o s a t i s f y i n complex t e r r a i n .

Table 2~Summary of prescr ibed f i r e a c r e s burned and tons of c r i t e r i a p o l l u t a n t emit ted (by geographic r eg ion , annual bas is) (from Sandberg and o t h e r s 1979)

Fuel consumed S t a t e s by Area Metric Metric Region h e c t a r e s tons lha tons

C a l i f o r n i a Oregon Washington

To ta l ROCKY MTN . Arizona Colorado Idaho Montana New Mexico North Dakota To ta l

N. CENTRAL Michigan Minnesota Wisconsin

To ta l EASTERN Delaware New Je r sey

To ta l SOUTHERN

A1a bama Arkansas F l o r i d a Georgia Louis iana Miss i s s ipp i N. Caro l ina S. Carol ina Texas Vi rg in ia To ta l

USA Tot a1

An a1 t e r n a t i v e method of de f in ing t h e va r i ances f o r complex t e r r a i n is mathematically i d e n t i c a l but does no t r e q u i r e t h a t t h e turbulence l ie i n a p a r t i c u l a r por t ion of t h e energy spectrum (Fosberg and o t h e r s 1976b, Fosberg and Fox 1978). In par-t i c u l a r , a mean wind is def ined s t a t i s t i c a l l y over t h e d i s p e r s i o n d i s t a n c e of i n t e r e s t . Devia t ion of wind about t h i s mean, whether i n t h e tu rbu len t i n e r t i a l subrange o r produced by organized flows of s c a l e smal l e r than t h e averaging d i s t a n c e s , a r e t r e a t e d mathematically as components of K. The d e v i a t i o n s about t h e s t a t i s t i c a l l y def ined mean wind a r e u'. The K ' s a r e then defined by

i n which t h e l i n e over t h e square of t h e dev ia t ions i s t h e averaging opera to r . The time constant T is r e l a t e d t o t h e averaging t ime and space. These K ' s do not r ep resen t turbulence. Ins tead , t h e K's

P a r t i c u l a t e s Carbon monoxide Hydrocarbons 8 kg lmet r i c 10 kg lmet r i c 5 kg lmet r i c

tons t o n s t o n s

d e f i n e t h e wind v a r i a b i l i t y a t s c a l e s smal l e r than those used t o d e f i n e t h e mean wind.

MANAGEMENT OF AIR RESOURCES

Emission con t ro l is required t o meet a i r q u a l i t y o b j e c t i v e s (U .S. Congress 1977). Because d i r e c t l i m i t s on emission from open burning can be achieved only by l i m i t i n g t h e mass of f u e l burned a t any given t ime, a model f o r a i r resource a l lo -c a t i o n was developed. The A i r Resource Al loca t ion Model (ARAM) is based on t h e Gaussian d i s p e r s i o n model def ined i n equat ion 1. Because t h e i n t e n t i s t o l i m i t emissions, equat ion 1 is rearranged t o

Q = X-"LG (5

The concen t ra t ion X is i n t e r p r e t e d h e r e a s t h e increment of a i r q u a l i t y a v a i l a b l e f o r prescr ibed

Table 3--Change i n annual burn ( i n h e c t a r e s by p o l l u t a n t )

Basin

Monterey Ranger D i s t r i c t 1. L i t t l e Sur 2. Big Sur 3. Carmel 4. Arroyo Seco 5. Ocean Front 6. San Antonio 7. Nacimiento

Santa Lucia Ranger D i s t r i c t 8. S a l i n a s (A) 9. S a l i n a s (B-)

10. Lopez Canyon 11. Cuyama (A) 12. Sisquoc

Mount Pinos Ranger D i s t r i c t 13. Cuyama (B) 14. an Joaquin Val l ey 15. P i ru

Oja i Ranger D i s t r i c t 16. Sespe 17. ~ a n t aPaula 18. Ventura

Santa Barbara Ranger D i s t r i c t 19. Santa Ynez 20. Santa Barbara Front

burning. ARAM is based on e a r l i e r development on emiss ion l i m i t s f o r s i n g l e sources , s i n g l e r e c e p t o r r e l a t i o n s def ined i n t h e TAPAS model (Fosberg and Fox 1976, Fox and Fosberg 1976). ARAM d i f f e r s from TAPAS i n t h a t ARAM cons ide r s m u l t i p l e sources and m u l t i p l e r e c e p t o r s i t e s and con ta ins improvements i n c h a r a c t e r i z a t i o n of t h e d i s p e r s i o n processes . Re la t ions between m u l t i p l e sources and mul t ip le r e c e p t o r s i t e s a r e def ined through mat r ix a lgebra a s

Here x , , and s o on a r e t h e increments of

p o l l u t i o n allowed a t r e c e p t o r s i t e s 1, 2, and so on; Q,, Q2, ... a r e t h e a l lowable emissions a t

source sites 1, 2, ... and Gll i s t h e d i s p e r s i o n

r e l a t i o n between source 1 and r e c e p t o r 1; G21 is t h e d i s p e r s i o n r e l a t i v e between source. 2 and r e c e p t o r 1, and so on. Expressing equat ion 6 i n ma t r ix format

C.O. T.S.P. H.C.1 1

20,500 170 2,700 6,200 -17 no d a t a

25,500 -7 0 no d a t a

The general ized form of ARAM expressed i n equa t ion 5 i s t h i s

ARAM h a s been appl ied on one National Fores t i n C a l i f o r n i a , t h e Los Padres, i n support of use of p resc r ibed f i r e i n v e g e t a t i o n management. Current a i r q u a l i t y r e g u l a t i o n s i n C a l i f o r n i a recognize t h a t prescr ibed f i r e is an a l t e r n a t i v e t o w i l d f i r e f o r vege ta t ion management. I n p a r t i c u l a r , t h e r egu la to ry agencies accept t h e concept t h a t a t o n of fue l burned i n prescr ibed f i r e can be used t o o f f s e t a t o n of f u e l burned i n w i l d f i r e .

In t h e following example, t h e increment f o r p resc r ibed burning is def ined a s t h e incremental depar tu re from t h e e x i s t i n g emission from pre-sc r ibed f i r e and w i l d f i r e s . This approach circum- ven t s t h e d i f f i c u l t i e s a s s o c i a t e d with development of a complete regionwide emiss ion inventory base. The assumption h e r e i s t h a t t h e e x i s t i n g emission from prescr ibed f i r e and w i l d f i r e a r e def ined wi th in t h e S t a t e Implementation Plan. The follow- i n g c a l c u l a t i o n s then represen t a n a n a l y s i s of

where prescr ibed burning can be increased and where burning must be reduced. The a i r q u a l i t y database i s t h e C a l i f o r n i a A i r Resources Board (1977) Three- Year Summary of A i r Quali ty. Nearly a l l t h e a i r q u a l i t y monitoring s t a t i o n s a r e i n urban a r e a s and, t h e r e f o r e , do no t n e c e s s a r i l y r e f l e c t cond i t ions i n t h e wi ldlands . The following c a l c u l a t i o n s a r e conse rva t ive es t ima tes because of t h e bias i n t h e da tabase . The meteorological database i s from t h e Nat ional F i r e Weather L ib ra ry (Furman and Brink 1975). Th i s database is t h e only r e a d i l y acces-s i b l e da tabase f o r wildlands. Plume r i s e ca lcula- t i o n s were made through t h e equat ions developed by Craig and Wolf (1980) f o r prescr ibed burning. Three c r i t e r i a p o l l u t a n t s were evaluated. These p o l l u t a n t s were p a r t i c u l a t e s , hydrocarbons, and carbon monoxide.

The physical s e t t i n g of t h e Los Padres National Fores t is along t h e C a l i f o r n i a Coast extending from n e a r Monterey i n t h e n o r t h , around Point Concep-t i o n , t o nea r Santa Barbara i n t h e ~ a l i f o r n i a

Bight. The Los Padres National Fores t l i e s wi th in t h e C a l i f o r n i a Coast Range and, t h e r e f o r e , can be broken up i n t o a s e r i e s of small a i r sheds . In p a r t i c u l a r , 20 a i r s h e d s were defined. Several C lass I wi lderness a r e a s a r e included. Emissions i n each of t h e a i r s h e d s were converted t o h e c t a r e s through a f u e l s inventory of tons of fue l per h e c t a r e and t h e emission c h a r a c t e r i s t i c s defined i n t h e second s e c t i o n of t h i s paper. Calcula ted changes i n combined emissions of prescr ibed and w i l d f i r e s a r e defined by t h i s l e a s t a c r e s f o r inc rease o r l a r g e s t nega t ive numbers f o r decrease from cur ren t emissions. A s a n example, a l l a i r -sheds on t h e Monterey D i s t r i c t a r e l imi ted by p a r t i c u l a t e p o l l u t a n t s ( t a b l e 3) . Most a i r s h e d s on t h e Los Padres National Forest could s u s t a i n minor i n c r e a s e s i n prescr ibed burning. Only t h r e e a i r - sheds show a need t o decrease t h e combined pre-sc r ibed f i r e , w i l d f i r e emissions. A l l t h r e e a i r -sheds a r e heav i ly populated, and t h e Fores t must compete with numerous o t h e r p o l l u t a n t sources f o r t h e a i r resource .

W A S H I N G T O N

Figure 4a--Location of weather s t a t i o n s i n northwest Oregon used t o c a l c u l a t e wind p a t t e r n s shown i n f i g u r e 4b.

Figure 4bÃ‘Calcu la te wind p a t t e r n s . Mesh length is 4 km by 4 km. Wind-speed is propor t ional t o length of arrows. Note t h e uniformity of wind d i r e c t i o n and speed over t h e P a c i f i c Ocean and wi th in t h e Willamette Valley. Winds i n complex t e r r a i n , t h e Coast Range, and t h e Cascade Range show a high degree of speed and d i r e c t i o n v a r i a b i l i t y .

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1980. Appl icat ion of i n f r a r e d d a t a from a geo- 1976. Some chemical and physical c h a r a c t e r i s t i c s synchronous meteorological s a t e l l i t e i n su r face of emissions from f o r e s t f i r e s . Paper No. wind modeling. Proc. 6 t h Conf . on F i r e and 76-2.3 presented a t t h e 69th Annual Meeting of Fores t Meteorology. Soc. Amer. For. p. 265- t h e A i r Po l lu t ion Control Associa t ion [June 275. 22-July 1, 1976, Por t l and , Oregon], 15 p.

Hydrocarbon Emissions from vegetation1

David T. Tingey Walter F. ~ u r n s ~

Abstract: A wide range of volatile organic compounds may be emitted by vegetation. The identified emittants, however, are mainly terpenoid in nature. Their emission rates are controlled primarily by the physical/chemical processes that regulate hydrocarbon vapor pressure. Emission rates vary between species and are influenced by environmental factors such as light and temperature. Regional emission estimates indicate that vegetation may emit as much as 30 kg of hydrocarbons k w 2 day-l. The measured atmospheric concentrations are in reasonable agreement with the estimated emission rates. Within the atmosphere, these hydrocarbons may par- ticipate in photochemical reactions leading to aerosol production and the consumption or formation of ozone.

High levels of ozone have been measured in 1955; Rasmussen 1972; Zimmerman 1979a). Individ-rural and remote locations far from significant ual species have relatively distinctive emission anthropogenic sources of oxidant precursors. profiles. For some species, only one or a few These elevated concentrations may have resulted compounds dominate the emission profile; however, from long distance transport and/or the photo- other species have a diffuse emission profile with oxidation of locally-produced biogenic hydro- no dominant compounds (Rasmussen 1972; Zimmerman carbons. Robinson (1978) proposed that ambient 1979a). Despite the wide range of potentially hydrocarbon concentrations were governed by both volatile compounds, only isoprene, monoterpenes, long distance transport and local production. and a few aromatics have been conclusively identi- Volatile organics, including monoterpenes and fied as emission products from vegetation isoprene, have been detected in the atmosphere (Rasmussen 1972; Zimmerman 1979a), hence they form (Rasmussen and Went 1965; Schjoldager and Watine the basis for further discussion. 1978; Whitby and Coffey 1977; Arnts and Meeks 1980; Lonneman and others 1977) and in laboratory studies shown to produce ozone (Arnts and Gay METHODS FOR ESTIMATING EMISSION RATES 1979), suggesting that they may contribute to ambient ozone concentrations. A variety of experimental methods have been

used to estimate emission rates. A tree branch or Plants contain a number of potentially volatile a few small plants were enclosed in a large Teflon

organic compounds including monoterpenes, iso- bag to estimate biogenic hydrocarbon emission prene, aldehydes, alcohols, and ketones (Meigh rates in the field (Zimmerman 1979a, l979b). The

bag was sealed, evacuated and refilled with hydrocarbon-free air. A small gas-exchange rate was maintained through the bag. After an accumulation

Presented at the Symposium on Effects of Air period, the head space was sampled to determine Pollutants on Mediterranean and Temperate Forest the gas phase concentration. Vertical gradients Ecosystems, June 22-27, 1980, Riverside, Califor- of temperature, water, and a-pinene, both within nia, U.S.A. and above the canopy of a loblolly pine (Pinus

Plant Physiologist, Office of Research and taeda L.) plantation were measured and used to

Development, U.S. Environmental Protection Agency, calculate emission rates (Arnts and others 1978).

Corvallis, Ore.; and Chemist, Northrop Services, Inc., Corvallis, Ore.

Sandberg, D. V. 1974. Measurement of p a r t i c u l a t e emissions from

f o r e s t r e s i d u e s i n open burning experiments. Ph. D. t h e s i s , Univ. of Washington. 165 p.

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Paper PNW-199, 7 p. P a c i f i c Northwest Fores t and Range Exp. Stn . , Fores t Serv. , U.S. Dep. Agr ic . , Po r t l and , Oreg.

Sandberg, D. V . , J. M. P i e rov ich , D. G . Fox, and E. W. Ross.

1979. E f f e c t s of f i r e on a i r . Gen. Tech. Rep. WO-9, 40 p. Fores t Serv. , U.S. Dep. Agric., Washington, D.C.

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f a c t o r s , 3d ed., Supplemental No. 8. AP 42.

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1971. On t h e n a t u r e , p r o p e r t i e s , and behavior of brush-fire smoke. CSIRO, Div. of Appl. Chem. Tech. Paper 1. 32 p.

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f o r e s t f i r e s . Paper No. 62-2.2. 6 t h Annual Meeting of A i r P o l l u t . Control Assoc. 14 p.

Hydrocarbon Emissions from Vegetation

David T. Tingey Walter F. ~ u r n s ~

Abstract: A wide range of volatile organic compounds may be emitted by vegetation. The identified emittants, however, are mainly terpenoid in nature. Their emission rates are controlled primarily by the physical/chemical processes that regulate hydrocarbon vapor pressure. Emission rates vary between species and are influenced by environmental factors such as light and temperature. Regional emission estimates indicate that vegetation may emit as much as 30 kg of hydrocarbons k w 2 day-l. The measured atmospheric concentrations are in reasonable agreement with the estimated emission rates. Within the atmosphere, these hydrocarbons may par- ticipate in photochemical reactions leading to aerosol production and the consumption or formation of ozone.

High levels of ozone have been measured in 1955; Rasmussen 1972; Zimmerman 1979a). Individ-rural and remote locations far from significant ual species have relatively distinctive emission anthropogenic sources of oxidant precursors. profiles. For some species, only one or a few These elevated concentrations may have resulted compounds dominate the emission profile; however, from long distance transport and/or the photo- other species have a diffuse emission profile with oxidation of locally-produced biogenic hydro- no dominant compounds (Rasmussen 1972; Zimmerman carbons. Robinson (1978) proposed that ambient 1979a). Despite the wide range of potentially hydrocarbon concentrations were governed by both volatile compounds, only isoprene, monoterpenes, long distance transport and local production. and a few aromatics have been conclusively identi- Volatile organics, including monoterpenes and fied as emission products from vegetation isoprene, have been detected in the atmosphere (Rasmussen 1972; Zimmerman 1979a), hence they form (Rasmussen and Went 1965; Schjoldager and Watine the basis for further discussion. 1978; Whitby and Coffey 1977; Arnts and Meeks 1980; Lonneman and others 1977) and in laboratory studies shown to produce ozone (Arnts and Gay METHODS FOR ESTIMATING EMISSION RATES 1979), suggesting that they may contribute to ambient ozone concentrations. A variety of experimental methods have been

used to estimate emission rates. A tree branch or Plants contain a number of potentially volatile a few small plants were enclosed in a large Teflon

organic compounds including monoterpenes, iso- bag to estimate biogenic hydrocarbon emission prene, aldehydes, alcohols, and ketones (Meigh rates in the field (Zimmerman 1979a, 1979b). The

bag was sealed, evacuated and refilled with hydrocarbon-free air. A small gas-exchange rate was maintained through the bag. After an accumulation

Presented at the Symposium on Effects of Air period, the head space was sampled to determine Pollutants on Mediterranean and Temperate Forest the gas phase concentration. Vertical gradients Ecosystems, June 22-27, 1980, Riverside, Califor- of temperature, water, and a-pinene, both within nia, U.S.A. and above the canopy of a loblolly pine (Pinus

Plant Physiologist, Office of Research and taeda I,.) plantation were measured and used to

Development, U.S. Environmental Protection Agency, calculate emission rates (Arnts and others 1978).

Corvallis, Ore.; and Chemist, Northrop Services, Inc., Corvallis, Ore.

Semi-quantitative estimates of emission rates were made using static gas-exchange chambers containing either detached leaves, twigs or whole plants (Rasmussen 1970; Rasmussen 1972; Sanadze and Kalandadze 1966a). Within these chambers carbon dioxide may be elevated or depleted depending on light intensity. This may modify plant metabolism and the stomatal aperture; humidity will increase; and high concentrations of hydrocarbon gases will build up within the chamber reducing diffusion gradients. These factors can lead to an underestimation of emission rates. Dynamic mass-balance gas-exchange chambers and leaf cuvettes which simulate the gaseous environments of plants in the field have also been used to estimate hydrocarbon emissions (Kamiyama and others 1978; Tingey and others 1979 and 1980; Tyson and others 1974). These chambers may be used to determine the influence of environmental factors on emission rates.

MECHANISM OF HYDROCARBON VOLATILIZATION

Terpenoid Biosynthesis

Knowledge of the mechanism and sites of terpenoid biosynthesis aids in understanding the factors controlling emission rates. Terpenoid biosynthesis starts with the conversion of carbon dioxide to sucrose with its subsequent metabolism to acetyl-CoA and mevalonic acid to form isopentenyl pyrophosphate. The hemiterpene, isoprene, (Cg) is formed from isopentenyl pyrophosphate; monoterpenes (Clo) are formed from a condensation of dimethylallyl pyrophosphate and isopentenyl pyrophosphate. Subsequent additions of isopentenyl pyrophosphate units form higher homologs in the terpenoid series (Loomis and Croteau 1980).

The conditions that promote isoprene biosynthesis indicate that it is likely synthesized within the chloroplast. Isoprene biosynthesis is affected by metabolic inhibitors that regulate photorespiration (Loomis and Croteau 1980).

Monoterpenes appear to be ubiquitous in higher plants (Loomis and Croteau 1980). The accumulation or secretion of significant quantities of monoterpenes is associated with the presence of secretory structures such as glandular hairs or trichromes, oil cells, resin ducts or glandular epidermises, and lysogenous spaces. It is generally assumed that monoterpenes are synthesized within the secretory cells, although this point has not yet been conclusively demonstrated (Loomis and Croteau 1980).

Hydrocarbon Diffusion from Plants

Gaseous diffusion between the plant and its environment is controlled by the chemical potential gradient between the inside and the outside of the leaf and the resistance to mass transfer along the diffusion pathway. The chemical potential gradient can be approximated by a concentra-

tion gradient. The larger the concentration gradient, the larger the hydrocarbon flux; conversely, the larger the resistance to mass transfer, the smaller the flux (Nobel 1974).

Only hydrocarbons with appreciable vapor pressures at ambient temperatures will be emitted at significant rates. The vapor phase concentration of hydrocarbons within the leaf is controlled by the liquid phase concentration, vapor pressure, and solubility. The vapor pressure of terpenoid compounds increases exponentially with the temperature (Jordan 1954). Monoterpene emission rates from black sage (Salvia mellifera Greene) and slash pine (Pinus elliottii Engelm.) also exhibit an exponential increase with temperature (Dement and others 1975; Tingey and others 1980), indi-cating that vapor pressure is a significant factor in controlling emissions. Emission rates from dead slash pine needles and black sage leaves are similar to emission rates from live tissue (Tingey and others 1980; Dement and others 1975), supporting the concept that the volatilization is primarily a physical process. Hydrocarbons with chain lengths greater than Clo generally have low vapor pressures and will not have a large emission rate.

When monoterpenes occur in high concentrations in resin ducts, oil cells or glandular trichomes, their emission rates are essentially independent of concentration. Large pools of isoprene, however, have not been detected. Below 35OC (the boiling point for isoprene), the emission rate is closely linked to its synthesis rate. Above 35OC, the emission rate is diffusion-limited (Tingey and others 1979).

Monoterpenes have a low aqueous solubility (hydrophobic) and higher vapor pressures than similar, more hydrophilic compounds. Therefore, monoterpenes would be emitted at a higher rate than similar oxygenated compounds at equal concentrations within the tissue. Similarly, if the concentration exceeds its aqueous solubility limit, then vapor pressure and emissions are independent of tissue concentrations.

Resistance to mass transfer can occur along either a stomatal or cuticular pathway (Nobel 1974). Either one or both pathways may be significant, depending on the species. Stomata are apparently the main pathway for diffusion of monoterpenes (Hanover 1972), isoprene and other compounds synthesized within the leaves. However, for plants with glandular trichomes or glandular cells in the epidermis, such as in the Labiatae and Solanaceae, the cuticular pathway is the main one for diffusion.

BIOGENIC EMISSIONS

Emission Rates

Emission rates for several plant species are shown in table 1. Total non-methane hydrocarbon and monoterpene emission rates are similar among

Table 1--Biogenic hydrocarbon emission rates estimated at 30Â°C

Species TNMHC1 Isoprene Monoterpenes References

fg [g dry weightl-I hr-l-

Slash Pine 4.1 2.6 Zimerman 1979a Longleaf Pine 7.3 5.6 Zitmerman 1979a Sand Pine 13.6 11.0 Zimerman 1979a Cypress 14.2 8.1 Zimerman 1979a Slash Pine 6.4 Tingey and other? 1980 Loblolly Pine 3.7 Arnts and others 1978 Cryptomeria 3.0 Kamiyama and others 1978 Laurel Oak 12.6 10.0 Zimerman l979a Turkey Oak 26.5 23.4 Zimmerman 1979a Bluejack Oak 56.4 43.9 Zimerman 1979a Live Oak 10.8 9.1 Zimnennan 1979a Live Oak 41.2 Tingey and others 1980 Willow 22.1 12.4 Zimerman 1979a Saw Palmetto 11.5 8.6 Zimmerman 1979a

Mean 7 Hardwood Flyckt and others 1980 Trees--Isoprene 20'0

Wax Myrtle Zimennan 19798 Persimon Zimerman 1979a Orange Zimerman 1979a Grapefruit Zimnerman 1979a Red Maple Zimerman, l979a Hickory Zimnennan, 1979a

Mean 10 Hardwood 1 Flyckt and others, 1980 Trees--Nm-Isoprene 7'3

Total non-methane hydrocarbons

the conifers and as much as 50 percent less than emission rates from hardwoods that emit isoprene. Monoterpenes account for 50 to 75 percent of the total non-methane hydrocarbon emissions in conifers. Similarly, isoprene accounts for 60 to 90 percent of total non-methane hydrocarbon emissions from isoprene emitters. Plants whose emissions were not dominated by either isoprene or a few monoterpenes had emission rates roughly similar to the conifers.

Total non-methane emission rates were estimated at several locations in the United States on similar vegetation types:

Vegetation Type Emission Rate1 and Location: (ye [g dry weight]-I hr-l)

Conifers Washington Florida Texas

Oaks California Florida Texas

Non-Conifers, Non-Isoprene Emitter Washington 7.8 California 4.1 Florida 4.7 Texas 0.2

Data from Zimmerman 1979b and c.

Emission rates for the conifers, oaks and non- conifer, non-isoprene emitting vegetation are similar within each vegetation type. This indicates an apparent high uniformity in emission rates among locations using the same estimation technique.

Hydrocarbon emission rates/unit tissue multi- plied by biomass density yield emission factors. Emission factors for the Tampa-St.Petersburg, Florida, area (Zimmerman 1979a), indicate that 92 percent of the total non-methane hydrocarbon emissions occur in the following four land use types: evergreen forests (35 percent); citrus groves (22 percent) ; pasture and rangeland (19 percent) ; and residential areas (16 percent). The remaining 8 percent was distributed among crop lands, deciduous forests, mangroves, freshwater, marine, and barren lands. Emission factors for trees were approximately 6 mg m-2 hr-l; shrubs, 2.0 mg m-2 hr-l; pastures, mud flats and other land use types were less than 0.1 mg m-2 hr-I .

Emission factors were developed to characterize the various biomes in the United States:

Emission Rate (mg w2hr-l)

Biome: Night

Grassland 0.2 Sclerophyll Scrub 1.4 Temperate Rain Forest 9.4 Deciduous Forest 2.7 Coniferous Forest 2.7 Desert 0.7 Tundra, Alpine Fields 0.4

Data from Zimmerman

Daytime biome emission factors ranged from a low of 0.3 mg m-2 hr-I for grasslands to a high of 10.7 for temperate rain forests. Nighttime emissions were 10 to 60 percent lower reflecting, in part, the absence of isoprene emissions.

Environmental Influences on Emission Rates

Isoprene production is light dependent, and persists for only a few minutes when plants are darkened (Rasmussen and Jones 1973; Sanadze and Kalanadze 1966b). Emissions increase with increasing light intensity until a maximum is reached and then remain constant (Sanadze and Kalandadze 1966a; Tingey and others 1979); similar to a light saturation curve for photosynthesis. Isoprene emissions are light saturated at moderate light intensities (Sanadze and Kalandadze 1966a; Tingey and others 1979). In contrast, monoterpene emissions from slash pine, black sage, and several other plant species, are similar in the dark and light (Tingey and others 1980; Dement and others 1975; Rasmussen 1972).

Isoprene emissions increase sigmoidally with temperature; low emissions occur at 18-20Â° and increase exponentially between approximately 20 and 35OC, then plateau. At higher temperatures (between 43 and 47OC), depending upon the species, there is the large, precipitous decline in isoprene emissions (Sanadze and Kalandadze 1966a; Rasmussen and Jones 1973; Tingey and others 1980).

The increase in isoprene emissions with temperature is greater at high light intensities than low (Tingey and others 1979). Isoprene emissions from several hardwood trees and live oak (Quercus virginiana Mill.) increased at approximately 20 and 16 percentI0C (20-35OC), respectively (Flyckt and others 1980; Tingey and others 1979).

Monoterpene emissions from conifers, black sage and hardwood trees increase exponentially with the temperature (Arnts and others 1978; Kamiyama and others 1978; Rasmussen 1972; Flyckt and others 1980; Dement and others 1975; Tingey and others 1980). The relative percent increase per degree temperature varies between species and ranges from approximately 6 to 20 percent/OC. In conifers, extensive genetic variations in monoterpene pools (Hanover 1972) may explain the lack of an exponential relationship between temperature and emission rates in some field studies (Flyckt and others 1980).

Typical diurnal emission patterns for isoprene and monoterpenes and environmental conditions for an average of summer days in Tampa, Florida, were used to illustrate the interaction of light and temperature on terpenoid emissions (Tingey and others 1979, 1980). During early morning and late afternoon, when the leaves are not light-saturated and the temperature is moderate, light would be the main factor controlling isoprene emissions from live oak. However, during most of the day, the leaves of the canopy are light-saturated; thus varying air temperature would control emission rates. More than 80 percent of the isoprene emissions were expected to occur after mid-morning, ceasing in the evening. Monoterpene emission rates . from slash pine increase after sunrise, peaking during early afternoon, and declining to a minimum shortly before sunrise. Approximately 55 percent of the total daily monoterpene emissions occurred during daylight hours (0600-1800) with an additional 25 percent emitted between sunset (1800) and midnight (2400).

Seasonal emission patterns were estimated for individual ponderosa pine and red oak trees (Flyckt 1979). Monoterpene emissions from ponderosa pine were sinusoidal, at a maximum during late spring (May and June), declining to a minimum around November, and then gradually increasing. In contrast, isoprene emissions from red oak were maximum during July and August and decreased during the fall. No isoprene emissions were detected during the winter; emissions reappeared in the spring with the initiation of new leaves. It is not clear whether seasonal emission changes were due solely to changes in environmental conditions or were, in part, due to changes in terpenoid pools. In addition to changes in the emission rates, there were also qualitative changes in the monoterpene emissions throughout the year (Flyckt and others 1980).

Table 2"-Estimated emissiops for biogenic hydrocarbons.

Emission Location Emissions Factor* References

---metric tons- kg km-x day-'

World 1.75 x 10'/year Went 1960 World 4.38 x lo8/year Rasmussen and Went 1965 World 8.30 x 108/year Zimwrnan 1979b United States 0.23-4.64 x lo7/year Rasmussen 1972 United States 6.5 x lo7/year Z i m e m a n 1979b Florida 157.0lday 32.3 Z i m e m a n 1979a (81 x 60 km) Texas

1 32.4ldav. 27.5 Z i m e m a n 1 9 7 9 ~ .

(38 x 31 to) Pennsvlvania 3.580.0/day 30.7 Flyckt and others 1980

Regional Emissions

Biogenic hydrocarbon emission rates for a variety of plant species and biomass estimates, were used to estimate emissions for various areas (table 2). The emission rate estimates for various estimation scales (world, United States, or regional) were approximately similar. The close agreement between the emission estimates from the three regional studies may have occurred because the same experimental approach was used. Emission estimates for Pennsylvania and the Tampa-St.Petersburg, Florida, area indicate that biogenic emissions range from 12 percent greater to 20 percent less than anthropogenic emissions (Flyckt and others 1980; Zimmennan 1979a; Wayne and Kochis 1978).

Relationship Between Primary Productivity and Emission Rates

A relationship between biogenic hydrocarbon emissions and primary productivity should exist because they are ultimately derived from photosynthetically fixed carbon dioxide. Measurements of the ratio of carbon lost as volatile terpenoids to primary productivity for several tree species indicated loss rates of 0.2 to 2 percent for isoprene and 0.06 to 0.4 percent for monoterpenes (Sanadze 1969; Tingey and others 1979, 1980; Tyson and others 1974). The relationship between primary productivity and biogenic hydrocarbon emissions could be used to delineate geographic areas where emissions would tend to be high. Based on the work of Leith (1975), primary productivity is highest in the Southeast, followed by the Mississippi Valley area and the central part of the United States and lowest in the Great Basin and the Southwest. Zimmennan (1979b) estimated that 45 percent of the total national biogenic hydrocarbon emissions occurred in the South, an area with the highest primary productivity in the United States (Leith 1975).

AMBIENT CONCENTRATIONS OF TERPENOIDS

Biogenic hydrocarbons were measured in the atmosphere over several vegetation types. The average isoprene concentrations varied from 10 ppb carbon for an oak forest to 0.1 ppb carbon for a pine forest. The average monoterpene concentrations ranged from 24 ppb carbon in the coniferous

forest in Norway to 2.7 ppb carbon in the coniferous forest in Idaho (Schjoldager and Watine 1978; Arnts and Meeks 1980; Coffey and Westberg 1978). Measured ambient concentrations of biogenic hydrocarbons and ambient concentrations predicted from biogenic emission rates are in reasonable agreement (Zimmerman 1979c; Flyckt and others 1980; Scully, 1979; Coffey and Westberg, 1978).

Atmospheric hydrocarbon concentrations are dependent on emission rates, mixing height, and the reactivities (photolysis and ozonolysis) of the individual components. Peterson and Tingey (1980) used a box model to estimate ambient air concentrations of isoprene and monoterpenes. The predicted isoprene concentrations increased during the daylight hours, reaching a maximum at mid- afternoon and then disappearing during the early evening when isoprene emissions ceased. Predicted ambient monoterpene concentrations were the lowest during mid-day when atmospheric dilution, photooxidation, and ozonolysis, were the highest, despite the fact that monoterpene emissions were a maximum. In contrast, monoterpene concentrations were the largest during the evening and early morning hours because monoterpenes are emitted at night when atmospheric mixing is low and hydrocarbon decay reactions are slow, permitting an accumulation of monoterpenes. This predicted monoterpene profile was verified by field measurements (Arnts and Gay 1979).

ATMOSPHERIC FATES OF TERPENOIDS

There are several atmospheric fates for the biogenic hydrocarbons, including conversion to aerosols, carbon monoxide formation, and photochemical reactions, both forming and consuming oxidants. Went (1960) attributed the blue haze found over many coniferous forests to the conversion of terpenes to aerosols. When limonene, a monoterpene, was reacted with NO and 03, greater than 50 percent of the limonenexwas converted to aerosols within 2.5 hours (Schuetzle and Rasmussen 1978). The aerosols contained both mono- and dimeric alcohols, aldehydes and acid-substituted products.

Zimmerman and others (1978) suggested that atmospheric isoprene and monotepenes could be oxidized in the atmosphere to CO with a yield of 60-80 percent. Based on biogenic emission estimates, they concluded that natural hydrocarbons may be the largest contributor to the United States carbon monoxide budget.

Nitrogen oxides in the presence of solar radiation form OH radicals (Cleveland and Graedel 1979). Hydroxyl (OH) radicals react with hydrocarbons, forming peroxy radicals, which in turn convert NO to NO2, perturbing the photostationary

ozone, PAN, formic acid, acetone, aldehydes, CO, and Coy formation when terpenes were irradiated in the presence of nitrogen oxides. The amount of ozone formed depended on the C/NO ratio. At a low C/NO ratio, 1 ppb C from terpenoids produced 2-4 ppb ozone. However, when the ratio was large, 1 ppb C produced 0.3 to 0.1 ppb ozone, suggesting that terpenoids also consume ozone. Eschenroeder (1974) and Coffey and Westberg (1978) concluded that emissions of biogenic hydrocarbons did not significantly alter ambient ozone concentrations through scavenging reactions.

Zimmerman (1979~) suggested that photooxidation of isoprene from forests could contribute 22 ppb ozone to the ambient concentration. Similarly, Coffey and Westberg (1978) suggested that emissions from coniferous forests could react to add 1 to 5 ppb ozone to the ambient air.

LITERATURE CITED

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Background Levels of Trace Elements in Forest Ecosystems1

G. Bruce Wiersma and Kenneth W. ~ r o w n ~

Abstract: This study was conducted as part of a project to develop a pollutant monitoring system for biosphere reserves. Sampling was carried out in the Great Smoky Mountains National Park and Olympic National Park. Results are reported for copper, lead, manganese, aluminum, calcium and phosphorus. Olympic National Park had much lower levels of lead and copper than Great Smoky Mountains National Park. Moss appeared to be a good collector for lead and copper. Results indicate that reference levels for trace elements can be established for remote areas, although they cannot be considered true background levels.

Introduction The reserves are areas that can be used to monitor the behavior of pollutants that have long range transport characteristics such as trace

Biosphere reserves are remote, pristine areas elements (Zoller and others 1974; Duce and others set aside in perpetuity. A pollutant monitoring 1975; Thrane 1978; Weiss and others 1971; system is being developed for implementation on Scheslinqer and others 1974; and Chow and Earl the reserves (Wiersma and others 1978a; Wiersma 1970). and others 1979). Purpose of monitoring pollutants on these areas are: Since many trace elements have the potential for

long-term transport the question becomes, in a 1. to serve as locales for background monitoring program for background areas, what

reference levels of certain pollutants . elements should be of prime interest. Two parameters can be used to estimate potential for

2. to provide a frame of reference against long-term transport. First, elements that have a which changes in impacted areas can be measured high vapor pressure, and second, elements that

would have a significant small particle (1.0 p or 3. to reflect changes of a global nature less) association. There is evidence that these

before such changes are obvious in more impacted two phenomena may work in conjunction. Ondov and areas. others (1977a) analyzed the relationships existing

between particle size and elemental composition in power plant emissions. They stated that elements with low vapor pressures tended to be associated

-presented at the Symposium on Effects of Air with larger particle sizes. In a subsequent paper Pollutants on Mediterranean and Temperate Forest Ondov and others (1977b) listed several elements Ecosystems, June 22-27, 1980, Riverside, as having significant small particle association California, U.S.A. including manganese, lead and copper.

2~coloqist, U. S. Environmental Protection Agency, Environmental Monitoring Systems Kyser and others (1978), using a variety of

Laboratory, U.S. Environmental Protection Agency, microprobe analytical techniques, found that

Las Vegas, Nevada; Botanist, U.S. Environmental arsenic, cadmium, cobalt, chromium, manganese,

Protection Agency, Environmental Monitoring nickel, lead, sulphur antimony, selenium,

Systems Laboratory, U.S. Environmental Protection thallium, vanadium and zinc were present on

Agency, Las Vegas, Nevada. particles primarily as surface material. This lends further support to the hypothesis that

elements with high vapor pressure tend to condense on smaller particles.

Methods

Analytical

This paper will present data for trace element levels in vegetation and forest litter. The analytical procedure used was spark source emission spectroscopy (SSES) which determines 26 elements per sample. The analytical procedure has been previously described by Alexander and others ( 1975).

Every tenth sample submitted was a quality assurance sample, alternating between known value samples and replicated samples. Samples were submitted in a set order. The analytical laboratory was required to analyze the samples in the order submitted.

Field Sampling

Two biosphere reserves, the Great Smoky Mountains and Olympic National Park, have been sampled as part of a pilot research project to develop a cost effective pollutant monitoring system. Great Smoky Mountains National Park was originally sampled in the fall of 1977 and again in 1978. The results of this effort have been reported by Wiersma and others (1979). Olympic National Park was sampled in the summer of 1979.

Figures 1 and 2 show sample site locations for the Great Smoky and Olympic National Parks respectively. Details of the Olympic study design are presented by Brown and Wiersma (1979).

*Sampled Autumn, 1977 Â Sampled Spring, 1978

Figure 1--Sampling locations in the Great Sknoky Mountains Biosphere Reserve.

1AirT Water 0 Vegetation-Soil

Figure 2-Sampling locations in the Olympic National Park Biosphere Reserve.

Results and Discussion

Trace Element Selection

The 26 trace elements analyzed by SSES are given in table 1.

Table l~elements and detection limits for spark source emission spectroscopy.

Element PPm Element PPm

P Na K ca M9 Zn cu Fe Mn B A1 Si Ti

Using this listing and selection criteria previously described, we are limiting our presentation in this paper to copper, lead and manganese. Also included are two biologically essential elements, calcium and phosphorus and one non-essential element, aluminum, which also is not one of the elements which has the potential for long-term transport.

Quality assurance results are shown in table 2. Good agreement exists between the analytical results and certified levels. In addition, the replicated samples, which were analyzed sequen- tially, showed no drift and had acceptable reproducibility.

Table 2--Quality assurance results for elements from Great Smoky Mountains.

malytical results for QA samples

Phosphorus 1,950 2,000 to Not significant 2,200

Lead 44.7 4 4 Not significant

Copper 12.0 11.0 to Not significant 13.0

Manganese 92.4 87 to 95 Not significant

Calcium 2.1 2.1 3 Not significant

~luminum~ - - Not significant

'AS determined by 95 pet. correlation coefficient of replicated samples and site numbers analyzed in order with site number

2 ~ o standard

3pct. by weight

Table 3 shows elemental levels for seven species of vegetation collected in the Great Smoky Mountains in the spring of 1978. Lead levels are highest in moss samples. Copper levels tend to be higher in wood fern and witch hobble, while manganese appears to be higher than previously reported for agricultural crops (Hemphill 1972). However, Romney and others (1977) report manganese levels for desert vegetation ranging from approximately 20 ppm to 220 ppm. Van Hook and others (undated) report manganese values in chestnut oak and hickory on the walker Branch water shed ranging up to 1,000 ppm. Grodzinska (1978) reported manganese levels in moss from Poland ranged from 79 to 880 ppm. Therefore, the levels of manganese reported appears reasonable when compared to other studies, particularly from forested areas. Calcium and phosphorus levels appear to be equal to or slightly below calcium levels reported for agricultural crops (Hemphill 1972).

Table 4 presents the results for the second sampling that occurred in the fall of 1978. There was a large increase in lead levels in moss

samples, but the rest of the vegetation samples reflected a slight decline in lead levels. A similar relationship was shown for copper.

Studies using vegetation, particularly for those elements where root uptake is small, as indicators of airborne pollution have ranged from interception phenomenon of vegetative surfaces for modeling purposes (Shreffler, 1978; Davidson and others 1976) to the use of individual species as collectors of airborne pollutants. Smith (1977) has reviewed the probability of urban vegetation filtering out airborne particulates. He reported that fine hairs on vegetative surfaces increase particle trapping phenomenon. Carlson and others (1976) and Wedding and others (1975) found in controlled studies that rough, pubescent leaves entrap seven times more particles than smooth nonpubescent leaves and the particle load increases with leaf area sometimes by a factor of 10. Removal of particle from vegetation surface appears to be through solubilization in rain and not physical impaction from droplets (Carlson and others 1976). Compounding this phenomenon is data reported by Harris and others (1976) which states "...all elements are in a far more soluble phase in the ambient aerosol (and are associated with particles retained by biological and inert surfaces) than in fly ash collected from in stack deflector plates.. .".

From the above discussion, plants with large leaf surface areas, or those with very rough pubescent surfaces (ferns, witch hobble) should collect larger particulate loads, but because of wash off, they probably cannot be expected to increase the particle load throughout a growing season unless another phenomena were at work. This is shown in table 4 by a decrease for lead and copper concentrations for ferns and witch hobble when compared to the results in table 3. Manganese, however, does not follow this pattern.

Tyler (1972) states that mosses, via passive ion exchange, can accumulate a variety of airborne elements. If this is the case then solubilization of surface material will not be an important removal process and fall moss samples should have higher levels than spring, particularly for copper and lead. Data in tables 3 and 4 tends to support this hypothesis.

The forest floor of the Great Smoky Mountains was sampled in the spring of 1978. Two types of samples were collected, the first was the unincorporated organic material and the second was the partially decomposed material of the fermentation layer. The results are shown in table 5. Except for manganese, significant differences existed between the litter and fermentation layer for all trace elements. The fermentation layer showed an increase in lead, copper, phosphorus, aluminum, and a significant decrease in calcium. Site to site correlations for each element, excluding aluminum, were significant between unincorporated organic matter and the fermentation layer.

--

Table 3--Average concentration of selected elements for samples collected in the Great Smoky Mountains biosphere reserve, spring 1978.

Lead Cop&= r Manganese Calcium Phosphorus Aluminum 9/9 9/9 9/9 pet. ~919 M9/9

Moss 42.3 13.4 368 0.32 1,430 1,410

Yellow birch 12.2 13.2 2,090 1.38 2,540 165 Betula allegheniensis

Red maple Acer rubrum

New York fern Thelypteris novaborecensis

Wood fern Dryopteris spinulosa

Witch hobble Viburnum alnifolium

Fraser fir Abies fraseri

Table &-Average concentration of selected elements for samples collected in the Great Smoky Mountains biosphere reserve, fall 1978.

Lead CoPP r Manganese Calcium Phosphorus Aluminum ~ / l ~ / 9 P3/9 pet. Id9 ~-9/<3

Moss

Yellow birch 10.5 2,370 1.50 2,360 154

Red maple 6.6 1,070 1.14 1,920 66

New York fern

Wood fern

11 9.9

5.3

3.9

11.5

1,000

1,350

0.68

0.50

854

2,200

2,040

424

Witch hobble I 13*3 9.2 2,800 1.50 1,700 426

Fraser fir 0.2 3.8 915 0.30 2,680 375

Reiners and others (1975) found lead levels in Wiersma and others (1978b, 1980) indicate that the New Hampshire in litter increase with altitude. probable source of this lead is from anthropogenic At extreme elevations, a slight decrease was activities. noted. The levels of lead in litter ranged from 35 to 336 ppm. The fir forest sites had the Some data are available from samples collected highest lead concentrations. Figure 3 shows a in the summer of 1979 in Olympic National Park. similar relationship from our data for lead in the The forest floor was not sampled by the method Smoky Mountains. This relationship did not. exist previously used in the 1978 Smoky Mountains study. for any of the other elements. Previous work by With the modified technique, unincorporated

Table 5~Compar ison of elemental leve ls i n unincorporated organic material and the fermentation l aye r , Great Smoky Mountains biosphere reserve, spring 1978.

Unincorporated Fermentation Coeff icient organic material layer cor re la t ion ( 8 d f )2

Manganese yg/g

calcium pet . 1 0.89 0.58 -5.22 0 .W4

Phosphorus pet .

Aluminum M / g I 1,980 5,420 Not Calculated

P a i r e d "T" t e s t 'Element i n unincorporated organic matter versus element i n fermentation layer . '95 pe t . confidence '99 pe t . conÂ idence

Copper averagNational Park. a r e 7 National Park.

A sf loor

l eve l s i n moss i n t he Ge about 3 times grea te r

t o 19 times grea te r than

imi la r re la t ionship e x i ssamples:

reat

t he Olym

t s f o r t he f o r e s t

than i n t h e Olympic

pic

30'00 35'00 40'00 4500 5000 55'00 6000

01 ympic l i t t e r

Smokys

Comparison of f o r e s t f l oo r Olympic National Park and

Mountains National Park.

samples from Great Sm

(yg/g) oky

Elevation (Feet)

Figure 3--Relationship between lead residues and a l t i t u d e i n t he Great Smoky Mountains Biosphere Reserve.

organic mater ia l s were sampled along with t he fermentation layer .

Copper and lead l eve l s i n moss and l i t t e r a r e compared f o r the two biosphere reserves:

Comparison of moss samples from Olympic National Park and Great Stooky Mountains

National Park. (pg/g)

Copper Lead-Moss-Olympic 4.4 5.7 Moss-Smoky Spring 13.5 42.4 Moss-Smoky F a l l 15.3 108.0

Smoky Mountains

Lead l eve l s i n t he Smoky Mountains

unincorporated organic matter spring 1978

Smokys fermentation spring 1978

True "background" l eve l s f o r many t r a c e elements a r e probably impossible t o determine. Lead l eve l s f o r moss i n t he Smoky Mountains appear high but i n l i n e with values reported i n t h e l i t e r a t u r e . For example Ruhling and Tyler (1968) analyzed museum samples of moss. They found samples co l lec ted a f t e r 1950 had lead concentra- t i ons of 80 t o 90 ppm. Samples co l lec ted around 1860 contained average lead l eve l s of 20 ppm. These researchers believed t h a t t he 20 ppm l eve l did not represent "natural" lead leve ls . They suspected "natural" lead leve ls might be considerably lower. The moss samples from Olympic

National Park averaged 5.7 ppm lead with some remote sites having average lead levels of 0.4 ppm and 2.2 ppm. Hirao and Patterson (1974) estimated for a remote site on the high sierra crest that 97 percent of the lead detected was from anthropogenic sources. Therefore, even for sites as remote as the high Dosewallips/High Quinault (over 13 miles from the nearest road) in a park that primarily receives wind off the Pacific Ocean, it may not be appropriate to consider the lead levels natural background levels.

It is our opinion that reference levels can be established in vegetation in remote areas for a variety of trace elements. Sites should be regionally representative and sampling should be repetitive through time, at least once a year, preferably twice a year. Biosphere reserves are ideal places to use because of their protected nature and the fact that they are selected to be representative of various biological systems.

Monitoring systems can and should be established in these reserves for the purposes listed.

Literature Cited

Alexander, G. V., D. R. Young, D. J. McDermott, M. J. Sherwood, A. J. Mearns, and 0. R. Lunt. 1975. Marine organisms in the Southern California bight as indicators of pollution. In International Conference on Heavy Metals in -the Environment. [1975. Toronto, Canada], p. 955-972.

Brown, K. W. and G. B. Wiersma. 1979. Pollutant monitoring in Olympic National Park biosphere reserve. In Proc. Second Conference on Scientific Research in the National Parks. [Nov. 28-30, 1979, San Francisco, Calif.] 12 p.

Carlson, R. W., F. A. Bazzaz and J. J. Stukel and J. B. Wedding. 1976. Physiological effects; wind reentrainment and rainwash of Pb aerosol particulate deposited on plant leaves. Environmental Science and Technology 10(12):1139-1142.

Chow, T. J., and J. L. Earl. 1970. Lead aerosols in the atmosphere: increasing concentrations. Science l69:577-580.

Davidson, C. I., S. V. Herring and S. IS. Friedlander. 1976. The deposition of ~b-containing particles from the Los Angeles atmosphere. In Proc. International Conference on -Environmental Sensing and Assessment. [Sept. 14-19, Las Vegas, Nevada] pp. 6-3 to 6-4.

Duce, R. A., G. L. Hoffman, and W. H. Zoller. 1975. Atmospheric trace metals at remote northern and southern hemisphere sites -Pollution or natural? Science 187:59-61.

Grodzinska, Krystyna. 1978. Mosses as bioindicators of heavy metal pollution in Polish national parks. Water, Air and Soil Pollution 9:83-97.

Harris, W. F., B. S. Ausmus, G. J. Dodson, Sidney Draggan, G. K. Eddlemon, Cyrus Feldman, J. M. Giddings, J. W. Huckabee, D. R. Jackson, S. A. Janzen, M. J. Levin, S. E. Lindberg, L. K. Mann, E. G. OINeill, R. V. OINeill, Cheryl B. Phillips, B. M. Ross, W. J. Selvidge, D. S. Shriner, R. R. Turner, P. Van Voris, Martin Witkamp. 1976. Environmental behavior of trace contaminants. The role of vegetation aerosol scavenging. ORNL-5257. Environmental Sciences Div. Annual Progress Report. Oak Ridge National Laboratory, Oak Ridge, Tennessee.

Hemphill, D. D. 1972. Availability of trace elments to plants with respect to soil-plant interaction. Annals New York Academy of Sciences 199:46-61.

Hirao, Y., and C. C. Patterson. 1974. Lead aerosol pollution in the high sierra over-rides natural mechanisms which exclude lead from a food chain. Science 184 :989-992.

Keyser, T. R., D. F. S. Natusch, C. A. Evans, Jr. and R. W. Linton. 1978. Characterizing the surfaces of environmental particles. Environmental Science and Technology 12(7):768-773.

Ondov, J. M., R. C. Ragaini, R. E. Hett, G. L. Fisher, D. Silberman and B. A. Prentice. 1977a. Interlaboratory comparison of neutron activation and atomic absorption analyses of size-classified stack fly ash. Preprint UCRL-78194. Lawrence Livermore Laboratory, Livermore, Calif.

Ondov, J. M., R. C. Ragaini, A. H. Bierman, C. E. Choquette, G. E. Gordon and W. H. Zoller. 1977b. Elemental emissions from a western coal fired power plant: preliminary report on concurrent plume and in-stack sampling. Preprint UCKL-78825. Lawrence Livennore Laboratory, Livermore, Calif. 7 p.

Reiners, W. A., R. H., Marks and P. M. Vitousec. 1975. Heavy metals in subalpine and alpine soils of New Hampshire. OIKOS 26(3):264-274.

Romney, E. M., A. Wallace and G. V. Alexander. 1977. Boron in relationship to a coal-burning power plant. Communications in Soil Science and Plant Analysis 8(9):803-807.

Ruhling, Ake and Germund Tyler. 1968. An ecological approach to the lead problem. Bot. Notiser 121:338-341.

Schlesinger, W. H., W. ,A. Reiners and D. S. Knupman. 1974. Heavy metal concentrations and deposition in bulk precipitation in montane ecosystems of New Hampshire, U.S.A. Environmental Pollution 6:39-47.

Shreffler, J. H. 1978. Factors affecting dry deposition of so2 on forests and grasslands. Atmospheric Environment 12:149-153.

Smith, W. H. 1977. Removal of atmospheric particulates by urban vegetation. Implications for human and vegetative health. The Yale J. of Biology and Medicine 50: 185-197.

Thrane, K. E. 1978. Background levels in air of lead, cadmium, mercury and some chlorinated hydrocarbons measured in south Norway. Atmospheric Environment 12:1155-1161.

Tyler, G. 1972. Heavy metals pollute nature, may reduce productivity. AMBIO 1(2):52-59

Van Hook, R. I., W. F. Harris, G. S. Henderson and D. E. Reichle. Undated. Patterns of trace element distribution in a forested watershed. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.

Wedding, J. B., R. W. Carlson, J. J. Stukel and F. A. Bazazz. 1975. Aerosol deposition on plant leaves.

Enviornmental Science and Technology 9(2) :151-153.

Weiss, H. V., M. K. Koide, and E. D. Goldberg. 1971. Mercury in the greenland icesheet: evidence of recent input by man. Science 74 :692-694.

Wiersma, G. B., C. W. Frank, K. W. Brown and C. I. Davidson. 1980. Lead particles in the Great Smoky ~ountains Biosphere Reserve. EPA-600/ 4-80-002. Environmental Monitoring Systems Laboratory, U.S. Environmental Protection Agency, Las Vegas, Nevada.

Wiersma, G. B. 1979. Kinetic and exposure commitment analyses of lead behavior in a biosphere reserve. MARC Report 15. 41 p. Monitoring and Assessment Research Center, Chelsea College, Univ. of London, London, U.K.

Wiersma, G. B., and K. W. Brown. 1979. Recommended pollutant monitoring system for biosphere reserves. In Proc. Second Conf. on Scientific Research inthe National Parks. [Nov. 26-30, 1979, San Francisco, Calif.] 19 p.

Wiersma, G. B., K. W. Brown, R. Hermann, C. Taylor and J. Pope. 1979. Great Smoky Mountain preliminary study for biosphere reserve pollutant monitoring. EPA-600/4-79-072. Environmental Monitoring Systems Laboratory, U. S. Environmental Protection Agency, Las Vegas, Nevada.

Wiersma, G. Bruce, Kenneth W. Brown and Alan B. Crockett. 1978a. Development of a pollutant monitoring system for biosphere reserves. EPA-600/ 4-78-052. Environmental Monitoring and Support Laboratory, U.S. Environmental Protection Agency, Las Vegas, Nevada. 114 p.

Wiersma, G. B., K. W. Brown and A. B. Crockett. 1978b, Development of a pollutant monitoring system for biosphere reserves and results of the Great Smoky Mountains pilot study. In Proc. 4th Joint Conference on Sensing of- Environmental Pollutants [1978, New Orleans, Louisiana], p. 451-456.

Zoller, W. H., E. S. Gladney and R. A. Duce. 1974. Atmospheric concentration and sources of trace metals at south pole. Science 183:198-200.

Effects of Chronic Exposures to Gaseous Pollutants on Primary Production Processes

Photochemical Oxidant Impact on Mediterranean and Temperate Forest

Ecosystems: Real and Potential Effects

2John M. Skel ly

Abstract: Photochemical oxidants Cprimarily ozone) a s a i r po l lu tan ts pose a more ser ious problem t o f o r e s t s of t he United S t a t e s than any o ther s ing le a i r po l lu tan t . Temperate and Mediterraean fo r e s t s elsewhere have most l i k e l y been s imi l a r l y impacted and current inves t iga t ions of such e f f e c t s a re being pursued. Ozone Land i t s photochemically reac t ive precursors) has been demonstrated t o occur a t con-s iderab le dis tances downwind of major urban sources. Ozone has induced pertubat ions t o vegetation over la rge areas and has therefore impacted innumerable and diverse fo r e s t eco-systems. Direct i n ju ry due t o ozone has been documented t o occur on numerous individual f o r e s t vegetation species but d i r e c t a l t e r a t i o n s of f o r e s t ecosystems a s r e l a t ed t o ozone induced e f f e c t s have only been extensively documented i n the San Bernardino Mountains of Cal i fornia; t o a l e s se r degree s imi la r s tud ies have been done i n the Blue Ridge Mountains of Virginia . Due t o t he current su l fu r dioxide (SO?) problems confronting European f o r e s t s and due t o the planned increased u t i l i z a t i o n of f o s s i l f ue l s i n much of t he North American Continent, the influence of ozone i n combination with SO2 must be f u l l y considered. The influence of o ther photochemical oxidants such a s nitrogen oxides and peroxy- ace ty l n i t r a t e on fo r e s t vegetation has remained r e l a t i v e l y unknown.

I

The d i f f i c u l t y of understanding the r e a l and fo r e s t ecosystems must be several orders of magni- po t en t i a l impact of a i r po l lu tan ts such a s ozone tude i n difference. Several s tud ies have r e l a t ed (03) on individual species within any given p lan t dose e f f ec t s t o f u l l - s i b crosses of various fo r e s t community a s compared t o r e l a t i n g d i r e c t o r t r e e species but such s tud ies have l i s t e d a i nd i r ec t e f f e c t s of OT, on e n t i r e and complex s e r i e s of caveats f o r t he reader t o consider

while in te rpre t ing even t he most bas ic r e s u l t s obtained. Such caveats have taken i n t o account possible unknown e f f e c t s due t o exposure chamber

p r e s e n t e d a t t h e Symposium on Effects of A i r systems, physical and b i o t i c f ac to r i n t e r ac t i ons ,

Po l lu tan ts on Mediterranean and Temperate Forest and/or r e l a t ed monitoring and da ta ana lys i s

Ecosystems, June 22-27, 1980, Riverside, methodologies. A s research advances from s tud ies

Cal i forn ia , U.S.A. of f u l l - s i b crossed p lan t mater ials through ha l f - s i b (open pol l ina ted , maternal l ines ) through species and fo r e s t types, t o f o r e s t communities

Professor, Plant Pathology and Director , Labo- and complex fo r e s t ecosystems, the number of r a to ry fo r A i r Po l lu t ion Impact t o Agriculture and influencing var iab les t o be considered while Forestry, Virginia Polytechnic I n s t i t u t e and in te rpre t ing the r e s u l t s becomes disproport ional S t a t e University, Blacksburg, VA 24060. and d i f f i c u l t t o comprehend.

Most s t ud i e s t h a t have dea l t d i r e c t l y with 03 e f f e c t s t o any given p l an t species have not considered t he e f f e c t s of po l lu tan t combinations even a t higher doses. Under na tura l conditions, f o r e s t ecosystems a r e impacted by a mu l t i p l i c i t y of atmospheric deposi t ions including anthropogenic po l l u t an t s i n gaseous, dry, and wet formulations. In addi t ion such deposi t ions do not occur s ing ly a t doses s imi l a r t o those reported f o r various exposure chamber s tud ies , e .g . , 1-8 hours per day f o r 5 days/week f o r 10 weeks, but r a the r they occur a t low concentrat ions, i n various and cons tan t ly changing combinations and over extended exposure periods. Thus, ecosystem s tud i e s t h a t have not considered even these few f ac to r s must be considered of l imited value f o r any i n t r i n s i c o r e x t r i n s i c i n t e rp re t a t i on .

I t i s a well known concept t h a t a i r po l lu tan t i nc i t ed pertubat ions lead t o s impl i f ica t ion of f o r e s t ecosystems. Continued exposures t o SO2 complexes have resu l ted i n s impl i f ica t ion and reversa l o f once fores ted land t o grassland communities o r i n some severe cases even t o s t e r i l i t y of t h e s o i l and accompanying erosion. However, such severe impacts due t o 0 po l lu t ion have not been reported t o occur with t he possi- b le exception of major f o r e s t vegetat ion species dec l ine i n t h e San Bernardino Mountains of Southern Cal i forn ia . The complexity of such s impl i f ica t ion scenarios involving minor changes i n receptor p l an t physiology and r e l a t ed long- term e f f e c t s on competitive a b i l i t i e s such as reproduction, nu t r i en t cycl ing, and r e l a t ed food chain events has not been well documented.

The main purpose of t h i s paper i s not t o present a review of l i t e r a t u r e per ta in ing t o ozone impact t o f o r e s t species and r e l a t ed ecosystems. Several exce l len t reviews of t h e subject have been previously published and due t o these comprehensive up-to-date ana lys i s of t he t op i c any fu r the r review would r e s u l t i n a redudancy i n t he l i t e r a t u r e (Miller 1973; Mi l le r and McBride 1975; Brown and o thers 1979 and Kozlowski 1980). Rather t h i s symposium paper w i l l attempt t o r e l a t e these review a r t i c l e s and accompanying new l i t e r -a tu r e i n t o an ana lys i s of t he r e a l and po t en t i a l long-term e f f e c t s of ozone on f o r e s t ecosystems. Addit ional ly, an e f f o r t w i l l be made t o r e l a t e ex i s t i ng l i t e r a t u r e i n t o suggestions f o r fu ture considerat ion of ecosystem impacts i n t o the National Ambient A i r Qual i ty Standards.

BACKGROUND AND ANTHROPOGENIC CONCENTRATIONS OF OXIDANTS IN FOREST SITUATIONS

A comprehensive review of ozone and o ther ph'o'tochemical oxidants has been published by the National Academy of Sciences (NAS 1977); a recent compilation of papers has a l s o been published (USEPA 1977b). These co l l ec t i ve s e t s of papers have provided an exce l len t review of t he o r ig in , chemistry, t r anspo r t , and atmospheric modeling of these po l lu t an t s .

Background Concentrations

Ozone is a na tu ra l l y occurring component of the Earth 's atmosphere and concentrations of 0.03-0.05 ppm 03 a r e general ly considered t o be normal due t o mixing v i a the s t r a to suhe r i c t r ans - por t e f f e c t (Corn and o thers 1975) Cfig.1 ) .

Net decay, but effects/ from long term ur, photochemistryand

photochemistry regional input Stratospheric

,-transport effect

Natural photochemical input \

Loss to groundand aerosols

-Rural (upwind)- -Urban- -Run1 (downwtnd)-

Figure I--The tropospheric ozone cycle . (from Corn and o thers 1975).

The emission of oxidant forming precursors such as oxides of ni t rogen and hydrocarbons i n t o t he lower atmosphere leads t o t he buildup of photochemically produced ozone and r e l a t e d peroxyacyl- n i t r a t e s [fig. 2) (NAS 1977).

Figure 2--The normal ni t rogen oxide phyto ly t ic cycle [A) and the cycle a s a l t e r e d by the addi t ion of hydrocarbons leading t o increased ozone concentrations (B) (from NAS 1977).

PAN has not been detected i n non-anthropogeni- c a l l y po l lu ted atmospheres but oxides of n i t r o - gen do occur na tu ra l l y i n the atmosphere and concentrations of 0.02-0.10 ppm NOx have been reported QNAS 1977). Brennan (Personal communication) has reported a high PAN concentra-t i on i n t he Eastern United S t a t e s of 10 ppb but suggested overa l l concentrations of PAN a r e well below West Coast observations.

Anthropogenic Concentrations i n Forested Areas

The long dis tance t ranspor t of oxidant precursors and ozone i n t o remote fores ted a reas has

been well documented (Miller and o thers 1972; Husar and o thers 1977; Hayes and Skel ly 1977; and Cleveland and Kleiner 1975). Concentrations of ozone above t h e cur ren t National Ambient A i r Qual i ty Standard (NAAQS) of 0.12 ppm 03 one hour average per 24-hour period; twice (2 days) per year have r ecen t ly been reported within t he fores ted a reas of Eastern (Skelly and o thers 1979) and mid-Western United S t a t e s (Wolff and o thers 1977). Numerous r epo r t s of high ozone concen-t r a t i o n s have been issued from t h e extensive San Bernardino Mountain Studies (SBM) i n southern Cal i forn ia (USEPA 1977a) . Major episodes of ozone have developed sporad ica l ly over t he summer months of May through October i n eas te rn f o r e s t s whereas a b e t t e r defined and s t a b l e oxidant season e x i s t s i n t he f o r e s t s of southern Cal i forn ia . Galloway and Ske l ly (1978) defined a major a i r po l l u t i on epidose i n J u l y 1977 t h a t involved high ozone concentrat ions and t h e highest ever recorded l a rge and f i n e aerosol SO4 concentrat ions ( f i g . 3, 4, and 5 ) .

By comparing monitoring da t a from t h e SBM s tud i e s with those of t h e Blue Ridge Mountain S tudies (BRM) a 3-4 f o l d g r ea t e r concentrat ion of ozone i s apparent i n t he former over the l a t t e r . Peaks of 0.20 t o 0.40 ppm O3 d a i l y one-hour maximums have occurred i n t he SBM f o r e s t ( f i g . 6) but t h e peak one-hour average ever recorded i n t he BRM a rea has been 0.166 ppm O r . Table 1 presen ts t h e monthly and peak one-hour concentrat ions of ozone a s monitored a t var ious s i t e s i n t he Blue Ridge Mountains of Virginia . PAN and NO have not been monitored i n eas te rn f o r e s t s oi^the United S t a t e s and although detected i n western f o r e s t s l i t t l e has been done t o d i s -t inguish d i f f e r ences i n t h e i r respec t ive e f f e c t s over those induced by ozone alone ( f i g . 6 ) .

OXIDANT CONCENTRATIONS JULY, 1977F

-SALT POND MTN. -- APPLE ORCHARD MTN.

ROCKY KNOB ........PINNACLES

I 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 17 18 192021 22232425262728293031

DATE

Figure 3--Oxidant concentrat ions a s monitored a t severa l loca t ions i n t he Blue Ridge and Southern Appalachian Mountains of Virginia during Ju ly , 1977. Daily averages (24 hours) a r e ind ica ted . Note peak period of Ju ly 15-20.

CHAROLETTSVILLE I

Figure 4--Total s u l f a t e (mg/m3) a s monitored a t Cha r lo t t e sv i l l e , VA during a i r po l l u t i on episode of Ju ly , 1977. Note buildup of Ju ly 15-20 and s imi la r sharp drop a s i n f i gu re 3 on Ju ly . (From Galloway and Ske l ly 1978).

Figure 5(A)--A review of t he Peaks of O t t e r a s taken on a c l e a r day i n t h e Blue Ridge Mountains. Photograph taken from Pine Tree Overlook a t a d i s tance of 11.6 KM from t h e Peaks. (B) Photo taken on Ju ly 20, 1977 during t he worst a i r po l lu t ion s tagna t ion experienced i n Virginia . Same view a s (A) .

4 - OZONEIpphml UV, OASIBIi U TELEMETRY,ONCE HOURLY

1 \

l a PAN (ppb) 5.C. ELECTRON CAPTURE

DAYS

Figure 6--Comparative d a i l y maximum hourly averages f o r ozone, t o t a l oxidant, PAN, and NO2 a t Sky Forest August, 1974. (From USEPA 1977).

Ozone concentrations i n European f o r e s t s have not been extensively invest igated but i n i t i a l s t ud i e s ind ica te t h a t ozone appears t o be episodal i n i t s occurrence i n a manner s imi l a r t o t h a t experienced i n Eastern United S t a t e s . Grennfelt (1979) reported on ozone concentrations a s moni-tored a t Rorvik about 40 KM south of Gothenburg,

Norway; an a rea s i t ua t ed c lose t o t he coast and considered t o be normally unaffected by l oca l oxidant producing sources. The highest 03 concen-t r a t i o n observed a t Rorvik was 0.20 ppm (August 1975) and i n Gothenburg t he highest 03 concentra- t i o n was 0.13 pprn ( tab le 2) . They suggested clockwise a i r movement a s associated with high pressure systems and long d is tance t ranspor t from Europe t o be r e l a t ed t o t he ozone episodes. Skarby (1979) reported t h a t ozone values recorded i n t he summertime have been too high t o be con-sidered a s normal background concentrations f o r Swedish condit ions. During t he summer of 1977 high O3 concentrations (0.20 ppm) were recorded on 21 out of 92 days. She a l s o suggested long- range t ranspor t t o be involved.

From these few repor t s it i s qu i t e obvious t h a t ozone concentrations i n excess of t he NAAQS occur frequent ly i n t he temperate and Mediter- ranean f o r e s t s of t he world. Therefore, it i s a l so obvious t h a t t he i n ju ry thresholds f o r numerous p lan t species have a l so been frequent ly exceeded and t h e e f f e c t s of these exposure doses a r e discussed below.

DIRECT EFFECTS TO FOREST SPECIES

The responses of any given f o r e s t ecosystem t o

Table I--Ozone concentrations (pprn) monitored a t Rocky Knob, Floyd Co., Va. (Blue Ridge Parkway) and a t Pinnacles and Big Meadows, Madison Co., Va. (Shenandoah National Park).

Month

' Rocky Knob Pinnacles Rocky Knob Pinnacles Rocky Knob Big Meadows 1

4onth Peak Month Peak Month Peak Month Peak Month Peak Month Peak h e r . Hour Aver. Hour Aver. Hour Aver. Hour Aver. Hour Aver. Hour

Aver. Aver. Aver. Aver. Aver. Aver.

January February March Apr i1 May June Ju ly August September October November December

Average f o r monitored mo.

%innacles s i t e moved 14 KM t o Big Meadow CSNP) May 1979.

o n l y 8 days out of t he month were used f o r t h i s da ta .

Table 2--The number of days with high ozone concentrations in Goth- enburg and Rsrvik, Norway 1972-1978 expressed as days with one hour mean of ozone exceeding indicated values (Grennfelt 1979).

Year >0.08- >0.10- >0.12- >0.15- Maxhourly PPm PPm PPm PPm mean

(PP~)

Gothenburg

18 11 5 0.20 17 5 0 0.13 6 0 0 0.11 12 8 1 0.15

I

l~ncludes data only until June 30, 1978.

photochemical oxidants must be as a result of the Extensive research has been justifiably done expression of direct effects to the individual on specific forest species to better define the component species within that ecosystem. The injury phase of this scenario of increasingly ability of scientific research to define those inclusive terminology. However, even within this direct effects to individuals and to relate such type of problem definition research a larger defined effects to the whole has been limited. endeavor has been made to define visible plant Three terms have been used somewhat interchangea- responses over the less easily measured physiolo- bly to define these effects and for purposes of gical responses. The latter responses may actual- this paper they shall be defined as: ly be of more importance to understanding the

damage and impact phases of subsequent ecosystem Injury - the result of one or more deleterious deteriorations. Thus, three additional terms

alterations of normal physiological processes as emerge: manifested by the presence of chronic or acute visible symptoms and/or growth reductions (growth acute injury - involves expresion of clinical reduction may be the only manifestation),. symptoms leading to death of cells, tissues,

organs, or entire plants and/or plant communities. Damage - injury that results in measurable Such injury is usually initiated by exposure to

economic loss to specific crops e.g. reduced high doses of pollutants ( concentration x <time)_ height or radial increment growth of forest trees but may result from exposure to lower concentra- resulting in reduced value of the commerical tions of pollutant over extended periods of time. forest.

chronic injury - involves non-lethal types of Impact - the total influence Qdetrimental or clinical symptom expressions such as reduced

beneficial) of air pollutants on all aspects of chlorophyll production and related pigmentation the forest ecosystem including even minor shifts changes, and reduced growth rates. Such injury towards reduced diversity of species, indirect usually results from still lower dose exposures. effects to watersheds and water quality, or direct effects to recreational values due to functional injury - involves injury to the reduced visibility at vistas or overlooks in functional efficiency of the plant as expressed National Forests and Parks. by reduced growth or other expression of loss

without the development of any other clinical symptoms, i.e. injury is only of a physiological and pre-clinical nature. Further visible symptoms do not develop. This form of injury is most difficult to define and measure and is the result of lowest dose exposures at predominantly near background concentrations of pollutants over extended periods of time.

An attempt to define the current status of knowledge concerning these various forms of direct effects due to ozone has been presented in table 3. A more specific assessment of recent documented studies of chronic pollution effects as induced by all species of air pollutants at the ecosystem level has been presented by Kickert and Miller (1978).

It is evident from table 3 that our knowledge of ozone effects following high dose exposures using artificial exposure systems for species level investigations is considered somewhat superior to that of the other levels of activity. However, when the abundance of plant species

indigenous to a mixed hardwood-conifer forest ecosystem of the Northeastern United States is *

taken into account our knowledge is very limited even for the clinical expression of symptoms by most species. Interpretation of available knowledge in the forest community and forest ecosystem columns may be somewhat harsh but most probably realistic. A similar table as constructed for sulfur dioxide related investigations would be much more optimistic thus attesting to the relative ease of working on predominant point sources of pollutants and their related effects. However, our knowledge of SO2 induced pertubations to forest ecosystems located at distances from various sources is relatively poor, e.g. knowledge of the subtle influences of S-related compounds to the productivity of Northeastern United States forests is virtually non-existent.

Direct Effects to Forest Trees

Davis and Wilhour (1976) have provided the most complete listing of woody plant sensitivities to sulfur dioxide and photochemical oxidants as

Table 3--The current status of knowledge concerning ozone induced effects to Temperate and Mediterranean forest tree species, forest communities, and forest ecosystems. Com- parisons of the San Bernardino Mountain Studies (SBM) versus all other investigations (01) have been noted.

Effect Study

Injury 01overall SBM

01 acute SBM

01chronic S BM

01functional SBM

01Damage SBM

Impact

I Forest species2

moderate moderate

abundant abundant

moderate moderate

poor moderate

moderate abundant

Forest Communities

poor moderate

moderate moderate

poor moderate

non-existent moderate

poor moderate

non-existent moderate

Forest Ecosystems

poor moderate

poor moderate

non-existent poor

non-existent poor

non-existent poor

non-existent poor

1In consultation by author with P. R. Miller Cpersonal communication).

2~stimates in this column include responses obtained in fumigation chamber studies If such information was to be detected poor to non-existent descriptions would be appropriate for each category.

^ B ~ definition not applicable.

--

- -

derived from t h e i r review of United S t a t e s , Canadian, and European l i t e r a t u r e .

Eastern White Pine

The predominant f o r e s t t r e e species s tudied i n Eastern United S t a t e s has been eas te rn white Pinus s t robus L. ; extensive l i t e r a t u r e reviews by Gerhold (1977) and Nicholson (1977) a r e ava i l ab l e . I n t e r e s t i n t h i s species has remained high s ince t he f i r s t discovery of i t s somewhat unique s e n s i t i v i t y t o ozone by Berry (1961). The response of t h i s species t o ozone concentrat ions a s monitored i n t he Blue Ridge Mountains of Virginia ( t ab l e 1) has been t he subject of severa l cur ren t inves t iga t ions . Skel ly and o thers (1979) reported t h a t of 315 white pines surveyed by using a modified evaluat ion scheme a s adapted from Mil le r (1973) 17, 80, and 3 percent were considered t o be t o l e r a n t , intermediate and s e n s i t i v e , respec t ive ly , t o ozone. Of t he 315 t r e e s tagged i n 1977, 10 were reported t o have died following repeated t yp i ca l c l i n i c a l symptoms of oxidant induced i n ju ry . Subsequent root exca-va t ions and i s o l a t i o n of fungi has yielded V e r t i c i c l a d i e l l a procera from t h e dying t r e e s . The growth r a t e of t r e e s i n each c l a s s was a l so examined by Benoit (1980) and r a d i a l increment growth over t he period 1955-1978 f o r t he sens i - t i v e c l a s s was s i g n i f i c a n t l y l e s s (p = .0 l ) than t h a t of t h e t o l e r a n t c l a s s (f igure 7 ) . A general dec l ine i n growth f o r a l l c l a s se s was noted.

1 \------=TOLERANT;53 YRS AVG AGE

-= INTERMEDIATE.52 YRS AVG AGE 9

YEAR 1955 '60 ' 70 1978

AVERAGE RADIAL INCREMENT GROWTH OF SENSITIVITY CLASSES

Figure 7--The average r a d i a l increment growth of ea s t e rn white pine i n t h r ee ozone s e n s i t i v i t y c l a s s e s a s found i n t he Blue Ridge Mountains of Vi rg in ia . Trees were located i n groups of 3 per s i t e with each s e n s i t i v i t y c l a s s represented i n each of 10 p l o t s (10 t r e e s / c l a s s ) .

Other Eastern Species

Forest t rees - - the r e l a t i v e 03 s e n s i t i v i t y of species has been inves t iga ted using high dose exposures, e .g . 0.25 ppm O3 f o r 8 hour exposure periods. Using such doses Davis and Wood (1972)

exposed 1.8 coni fe r species and found Austrian Pine (Pinus n igra , Arnold), jack pine (c. E-s iana , Lamb.) and Virginia pine (P. v i rg in iana ,-Mil l . ) t o be t he most s ens i t i ve . However, they reported var iab le symptom response among the d i f f e r en t species , among p l an t s within species , and between branches and needles of individual p l an t s . In a s e r i e s of exposures, numerous deciduous t r e e s were a l s o exposed t o s imi l a r ozone doses and green ash ( ~ r a x i n u s pennsylvanica Marsh.), white ash (F. americana L.) and t u l i p poplar ( ~ i r i o d e n d r o n t u l i ~ i f e r a L . ) were reported t o exhib i t f o l i a r i n ju ry by Wood (1970). Jensen (1973) determined t he s e n s i t i v i t y of 9 deciduous t r e e species on t he ba s i s o f height growth during a 5 month exposure t o 0.30 ppm 03 f o r 8 hours per day. He determined t h a t s i l v e r maple (A& saccharinum, L.) , green ash, and sycamore (Platanus occ identa l i s , L . ) were t he only species determined t o be s ens i t i ve using both parameters. Numerous s imi l a r s t ud i e s using high dose exposures have been reviewed by Skel ly and Johnston (1979).

Typical oxidant symptoms have been noted by Skel ly (unpublished) on several major f o r e s t t r e e species indigenous t o Shenandoah National Park of Virginia [f ig . 8) .

Figure 8--Typical oxidant induced s t i pp l i ng on hickory Garya spp.) a s observed i n t he Shenandoah National Park of Vi rg in ia . Note asymptomatic a rea of covered over por t ion of lower l e a f i n cen t e r of photograph (upper l e a f pul led back).

Very few low dose exposure s t ud i e s have been conducted t o determine e f f e c t s due t o c lo se r t o ambient po l lu tan t concentrat ion o r due t o ambient exposure condit ions. However, severa l recent s tud ies have attempted t o reproduce ambient concentrations of 03, SO2, and NOx (and various combinations thereof) and t o study t h e i r e f f e c t s on t he growth of l ob lo l l y pine (P. taeda L.) Kress and Skel ly (1980a) American sycamore Kress and Skel ly (1980b), and severa l o ther eas te rn t r e e species (Kress 1980). In t h e com-bined pol lu tan t s t ud i e s using 0.05 ppm 03, 0.10 ppm N02, and 0.14 ppm SO2 f o r 6 hours per day f o r 28 consecutive days s i gn i f i c an t height reduct ions

were reported a s induced by O x alone t reatments f o r each species without c l i n i c a l symptoms presen t on sycamore and with <5 percent f o l i a r i n j u r y on l o b l o l l y pine. Kress (1980) reported height growth increases and/or decreases f o r 10 t r e e spec ies following exposure t o 0.05, 0.10, and 0.15 ppm 03 f o r 6 hours/day f o r 28 consecutive days. Lowest dose exposure s i g n i f i - c an t l y reduced t he height of l o b l o l l y pine and 0.10 pprn O3 reduced height growth i n l o b l o l l y pine, green ash , sycamore, p i t ch pine (P. r i g i d a Mi l l . ) and sweetgum (Liquidambar s t y r a c i f l u a L . ) . Sl igh t he ight growth s t imula t ions were reported f o r severa l spec ies following 0.05 ppm 03 t r e a t - ment and sugar maple (A. saccharum Marsh.) responded p o s i t i v e l y even a t t h e 0.10 ppm 03 t reatment (p = 0.05) .

Understory VegetationÃ‘Harwar and Treshow (1971) have conducted one of few s tud i e s designed t o determine ozone e f f e c t s t o understory p l an t s . They exposed 17 r ep re sen t a t i ve species of an aspen community t o various high and low doses of 0

3 5 days pe r week throughout t h e growing

season f o r 3 consecutive years . Several species were found more s e n s i t i v e than expected and s e n s i t i v i t y was so var ied between species t h a t t h e authors suggested major s h i f t s i n community composition would be probable following only a year o r two of exposure.

Kohut and Krupa (1978) determined t he s ens i - t i v i t y of s eve ra l herbaceous p l an t s of t he North- c e n t r a l U.S. f o r e s t s . They l i s t e d a group of p l an t s found i n t he f o r e s t s o f t he North Central region t h a t were a l s o s e n s i t i v e t o 0.08 and 0.15 ppm 0, f o r only 4 hours. These p l an t s a r e a l so na t i ve t o t h e fores ted a r ea s of t h e nor th and southeastern por t ions of t h e United S t a t e s . The s e n s i t i v e p l a n t s l i s t e d were wild buck- wheat, chicory, da i sy , mustard, and Ribes. Other work by Ske l ly (1977, unpublished) has i d e n t i f i e d symptoms t y p i c a l l y induced by 0 on Clematis sp . i n t h e Shenandoah National Park of Vi rg in ia .

Figure 9 has been presented t o f u r t h e r demonstrate t h e e f f e c t of ambient concentrat ions of ozone on a spec ies t h a t i s widely d i s t r i - buted across North America i . e . common milkweed (Asclepias spp.) . Duchelle and o thers (1980) observed severe, moderate, and only s l i g h t i n ju ry t o t h i s spec ies t h a t occurred n a t u r a l l y i n open p l o t s and i n non- f i l t e red and f i l t e r e d open t op chambers, respec t ive ly , a s located i n t h e Shenandoah National Park i n Vi rg in ia . This spec ies i s being t e s t e d f u r t h e r f o r i n j u r y th resholds and f o r use a s p a r t of a p l an t b io ind i ca to r system.

A s another p a r t of t h e Blue Ridge Mountain S tudies , Duchelle and Ske l ly (1980) es tab l i shed 4 r e p l i c a t i o n s of open top chambers receiving charcoal f i l t e r e d a i r o r non-charcoal f i l t e r e d a i r i n order t o i nves t i ga t e height growth of s e l ec t ed f o r e s t t r e e s . Four open p l o t s were a l s o es tab l i shed . By mid-summer it became neces-

sa ry t o c l i p (to a 1 . 3 cm height) and remove compet ing na tu ra l vegetat ion which was then co l - l ec ted f o r dry weight measurements ( table 4 ) .

F igure 9--Oxidant i n ju ry t o milkweed ~ ~ & l e ~ i a sspp.) observed i n t he Shenan- doah National Park, VA a s grown i n (A) open p lo t s , (B) non-f i l t e r e d open top chamber and CC) cha rcoa l - f i l t e r ed open top chamber. Purple s t i p p l e was only noted on upper l e a f sur faces .

Table 4--The dry weight of foliage of composited clippings as collected from 4 filtered air and 4 non-filtered air open top chambers and 4 open plots established in the Big Meadows Area of the Shenandoah National Park, VA.

Exposure Clipping Dates1 Aug. 14, 1979 Oct. 9, 1979

Dry Weight (Grams)

Total Total wt2 Average wt Average

Filtered 7263 1816 1599 400 Non-filtered 4937 1234 1323 331 Open 3128 782 845 211

~ l l species composited as clipped to 1.3 cm height, 10 foot diameter plots.

z 4 replications.

Western Species

Ponderosa Pine

Since the decline of ponderosa pine (P. ponderosa Laws .) during the 1950's (and hence- forth into the 1980's) in the South Coast air basin and San Bernardino Mountains of California, this species has become the most intensively investigated of all western forest vegetation species. Declining ponderosa pines have most recently been reported in the southern Sierra- Nevada mountains by Miller and Millecan (1971) and in the Sequoia National Forest and Sequoia- Kings Canyon National Parks by Williams and others (1977).

The decline of this species was initially termed "X-diseasev by Parameter and others (1962); further study by Miller and others (1963) eluci- dated ozone to be the direct incitant. Inter-relationships of foliar symptoms with increased root disease and increased incidences of bark beetle infestations in injured trees have been determined along with significant growth decreases and mortality (Stark and others, 1968; McBride and others, 1975). Several reviews of the major studies that have dealt with ponderosa pine have recently been published by Brown and others (19791, Miller (1973) and Miller and McBride (1975).

Most recent investigations by Coyne and Bingham (in press) identified characteristics of ecotypic variation in E. ponderosa which varied in their clinical symptom response to ozone under field conditions. Light responses, photosynthetic rates, and stomatal conductances were observed and differences among injury classes were manifest as acceleration of the normal decline of C02

fixation and stomatal conductance usually associated with needle aging. Needles of sensitive trees senesced and abscissed prematurely thus contributing to a steady decline in tree vigor and increased vulnerability to other sources of stress.

Other Forest Tree Species

Miller (1973) ranked the following species for their decreasing sensitivity to ozone following fumigation tests:

Most sensitive Western white pine (P. monti-cola Doug.) Jeffrey x Coulter pine hybrid

Monterey x Knobcone pine hybrid (P. radiata x P. -altenuata) Ponderosa pine [c. ponderosa Laws.)

Intermediate Coulter pine (P. coulteri D. -Don") Douglas fir (Pseudotsuga menziesii (Mirb. ) Franco Jeffrey pine (P. jeffreyi Grev. & ~alf.)-White fir (Abies concolor (Gord. 6 Glend.1 Lindl. ~i~ cone Douglas fir (Pseudo- tsuga macrocarpa (Vasey) Mayr. Knobcone pine (P. attenuata -Lemm.)

Tolerant Incense cedar (Libocedrus decurrens Torr.) Sugar pine (c.lambertiana Doug1.) Giant sequoia (Sequoia gigantea (Lindl. ) Decne.

In one of few low O3 dose exposure studies, 9 western conifer species have been evaluated for foliar injury and growth responses by Wilhour and Neely 0.977). They found significant growth reduction in juvenile seedlings of P. ponderosa and P. monticola exposed to 0.10 ppm 03 for 6 hours/day consecutively for up to 22 weeks. They noted no constant association between growth response and foliar injury.

DIRECT EFFECTS TO FOREST ECOSYSTEMS

A fair number of published reports assessing air pollution induced injury to agricultural crops are available. Damage estimates of yield losses have also been published e.g. air pollution injury to potatoes in the Atlantic Coastal States [Heggestad, 1973). Such evaluations have been based upon extensive knowledge of crop management practices and abundant information exists concerning expected yields. Therefore, yield

losses such as potato tuber number, size, and weight may be easily determined and subsequently correlated with the degree of foliar injury as induced by photochemical oxidants (Heggestad, 1973) .

Advancing from a relatively simplistic agronomic monocultural system of crop management to CHARACTER-

ISTICSa mixed hardwood conifer forest ecosystem poses considerably different problems in determining an effect due to any given single stress factor. As noted previously, an abundance of literature

COMMUNITYdescribing symptoms has become available for COMMUNITY STRUCTURE STRUCTURE

several major forest species that appear sensitive to photochemical oxidants (table 3). How- 5 6 7 8 9 ever, the overall impact of the more subtle changes in functional efficiency of the plant expressed, for example, as slightly reduced photosynthetic capability of otherwise asymptomatic foliage or noted trends of slightly shorter pollen tube length in the presence of low doses of 03 remain relatively little understood.

There have been no major investigations of oxidant impacts to forest communities or forest Figure lo--Community-succession interactions in ecosystems with the single well known exception a mixed-conifer forest ecosystem. (From Taylor, of the San Bernardino Mountain Studies. The 1974). intensity of the various studies and their related interactions within one of many possible areas of investigation has been illustrated in figures 10 and 11. As noted in figure 10, 0oxidant air pollutants are only one of many POLLUTANTS

natural or anthropogenic stress factors important to the forests of the San Bernardino Mountains and if this figure were to be modified for illus- tration of an Eastern U.S. or European forest, /&-$.A 1.

SYNTHESISSO2 and other forms of atmospheric depositions would necessarily be added for emphasis. Figure 11 illustrates only a few of the complex interactions which may take place within an ecosystem

MOISTUREand even a very subtle change in bark charac- 0;teristics or carbohydrate pools as initially induced by oxidant injury of the foliage may be sufficient to encourage a bark beetle attack of

BARKweakened trees. As related in table 3, an

TEXTURE ...... . . ..- ..-evaluation of knowledge concerning injury,

THICKMESS

damage, and impact to forest species of the San .... . ..-....-PHLOEM THICKNESSBernardino Mountains (primarily E. ponderosa) is .......-.- - -PHLOEM MOISTUREabundant and knowledge is considered to be . - - - .....- - -

moderate for the forest community. However, due RESIN QUANTITYto the complexity of any given forest ecosystem, ....-.- - - - - -

including that which has been intensively studied in the San Bernardino Mountains, relatively poor information exists as to the subtle influences to the functioning of any given forest ecosystem.

FUNGI

FUTURE RESEARCH EMPHASIS AND CONSIDERATIONS

Why do we know so little about oxidant induced Figure 11-411 example of tree-level interactions injury, damage, or impact to forest communities in a mixed-conifer forest ecosystem. Data from or forest ecosystems? Why have only a few tree these types of studies would be integrated into species been intensively studied and relatively overall effect illustrated in figure 11. (From few others evaluated for foliar symptom response? Taylor, 1974) . How does the lack of such information influence decisions made regarding the establishment of Intensive management of agronomic crops through National Ambient Air Quality Standards? selection of tolerant varieties for planting in

high oxidant areas and appropriate changes in cultural practices such as withholding irrigation water during oxidant pollution episodes have all served to reduce the immediate injury (and therefore damage and impact) to such important crops as potatoes, tobacco, soybeans, snapbeans and certain horticultural plants. Through the development of such practices, the agricultural scientist has assisted the immediate grower (as should be the case) but concurrently the economic cost/bene- fit justifications for pollution abatement enforcement have been lessened since overall impact has potentially been greatly reduced. The evaluation of forest tree species for sensitivity to various pollutants has also been attempted and likewise long term growth losses may be averted. Such investigations must be approached with a certain degree of caution since long term subtle changes most undoubtedly are occurring in natural forest ecosystems but as yet most remain undetected. Natural ecosystems usually have a system of checks and balances but the system remains deli- cate and trends towards simplification are easily initiated. Changes in primary productivity, energy resource flow patterns, biogeochemical cycles, and species successional patterns may all be challenged by oxidant air pollution but have remained virtually non-studied .

The difficulties encountered in developing research aimed at isolating, identifying, and subsequently integrating the known effects of oxidant air pollutants on the forest ecosystem are too numerous to completely cover in the remaining space available. A partial listing however, must include these important points:

1) Photochemical oxidant is insidious over extremely large areas of diverse forest land and the establishment of control (non- pollution exposed) areas has become virtually impossible.

2) The introduction of charcoal filtration systems into such areas to establish kontrolsw is at best artificial and due to physical restrictions the ability of such systems to define a true ecosystem pertubation is likewise limited.

3) Long-term investigations must take into account innumerable variables some of which are very transient in their occurrence and others for which relatively little is known even under natural conditions.

4) Modeling and related statistical procedures must take into account the diversity and complexity of a forest ecosystem and statistically probabilities of p = .01, .05, or .10 must not be the only acceptable limits of "biological significance." The prediction of a biological event with 70 percent accuracy may be valid. Observation of only a 1-5 percent decrease in annual radial increment growth or similar decreases in pollen production and viability may not

be statistically significant but may have greater long-term biological significance to the ability of a species to survive over their natural range.

The natural forested ecosystems of the temperate and Mediterranean regions of the world may serve to provide the most invaluable bioindicator of long-term photochemical oxidant air pollution induced effects. National air quality standards must be reasonably developed to protect these natural resources from even minor change but initially adequate financial support and associated quality research must be continued to adequately define the real and potential effect of oxidants to plant species, to plant communities, and to entire forest ecosystems.

LITERATURE CITED

Benoit, L. F. 1980. Ozone effects on long term radial incre-

ment growth and reproduction of eastern white pine. (Abstr.) Proc. Potomac Div. her. Phytopath. SOC., Morgantown, W. Va.

Berry, C. R. 1961. White pine emergence tipburn, a physio-

genic disturbance. (Sta. Paper No. 130., 8 p.). Southeast For. Exp. Sta., USDA- For. Serv., Athens, Ga.

Brown, H. D., P. R. Miller, J. M. Skelly, D. B. Drummond, and C. E. Carlson.

1979. Air pollution effects on forest vegetation and the analysis of the role of Forest Insect and Disease Management. 134 p. USDA-For. Serv., Washington, D.C.

Cleveland, W. S. and B. Kleiner. 1975. Transport of photochemical air pollution

from The Camden-Philadelphia urban complex. Environ. Sci. Tech. 9:869-872.

Corn, M., R. W. Dunlap, L. A. Goldmuntz and L. H. Rogers.

1975. Photochemical oxidants: sources, sinks and strategies. J. Air Poll. Contr. Assoc. 25:16-18.

Coyne, P. I. and G. E. Bingham. 1980. Comparative ozone dose response of gas

exchange in a ponderosa pine stand exposed to long term fumigations. (Submitted for publication to J. Air Poll. Contr. Assoc.).

Coyne, P. I. and G. E. Bingham. 1980. Variation in photosynthesis and

stomata1 conductance in an ozone-stressed ponderosa pine stand: Light response. (Submitted for publication to For. Sci.).

Davis, D. D. and R. G. Wilhour. 1976. Susceptibility of woody plants to

sulfur dioxide and photochemical oxidants. 72 p. USEPA Ecol. Res. Series EPA-600/3- 76-102.

Davis, D. D. and F. A. Wood. 1972. The relative susceptibility of eighteen

coniferous species to ozone. Phytopathology 62:14-19.

Duchelle, S. F., J. M. Skelly and L. W. Kress. 1980. The impact of photochemical oxidant

air pollution on biomass development of native vegetation and symptom expression of Asclepias spp. (Abstr.) . Proc. Potomac Div. her. Phytopath. SOC. Morgantown, W. Va.

Galloway, J. N. and J. M. Skelly. 1978. A pollution episode in Virginia.

Virginia Climate Advisory 2(3):4-6.

Gerhold, H. D. 1977. Effect of air pollution on Pinus

strobus L. and genetic resistance. 45 p. USEPA Rep. No. EPA-600/3-77-002. Cor- vallis, Or.

Grennfelt, P. 1979. Ozone monitoring in Scandanavia. In

Report from the workshop "Ozone effects on vegetation in Europe." M. Eastmond and L. Skarby Eds. p. 5-8. Swedish Water and Air Res. Inst., Stockholm.

Harward, M. R. and M. Treshow. 1971. The impact of ozone on understory

plants in the aspen zone. Proc. 64th Ann. Mtg. Air Poll. Contr. Assoc. Atlantic City, N.J.

Hayes, E. M. and J. M. Skelly. 1977. Transport of ozone from the northeast

U.S. into Virginia and its effect on eastern white pine. Plant Dis. Reptr. 51:778 -782.

Heggestad, H. E. 1973. Photochemical air pollution injury to

potatoes in the Atlantic Coastal States. Amer. Pot. J. 50:315-328.

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Primary Productivity, Sulfur Dioxide, and the Forest Ecosystem: an

Overview of a Case study1

Abstract: The objective of the West Whitecourt case study was to determine the consequence of chronic long term exposure of a forest ecosystem to low concentrations of sulphur dioxide emissions originating from a "sour gas" processing plant in west central Alberta, Canada. An interdisciplinary ecological approach was utilized. The vegetation and atmospheric environment were characterized. A concept of ecologically comparable sampling site selection was developed and applied in the West Whitecourt study area. Laboratory and field measurements revealed a reduction in photosynthetic rate in lodgepole pine x jack pine (Pinus contorta x Pinus banksiana) in the field. Reduction of adenosine triphosphate (ATP) concentration in pine tissue during SO2 fumigation in the field followed by complete recovery after termination of SO2 fumigation and the disruption of mineral nutrient cycling in the forest ecosystem were observed. Basal area increment measurements of 200 lodgepole x jack pine trees from 5 ecologically comparable sampling sites revealed a decrease in wood production directly related to the presence of sulphur dioxide emissions. It is recommended that the concepts of the assimilatory capacity of the environment for sulphur gas pollutants and irreversible ecological modification be utilized as measures of environmental quality.

Many review articles have been written' addres- Kickert and Miller, 19791, very little emphasis sing the problem of air pollutants and forest has been placed upon integrated research programs ecosystems (Tam and Aronsson, 1972; Smith, 1974; concerning the impact of chronic long term low Miller and McBride, 1975; and Linzon, 1978). concentration air pollution stress on forest eco- These reviews documented the extreme examples of systems. The objective of this paper is to pre- acute high concentration long term air pollution sent an overview of a four-year integrated forest stress on ecosystems and were essentially post- ecosystem case study designed to determine the mortem studies. Environmental change due to air consequence of chronic long term exposure of a pollution stress was clearly visible in these conifer forest ecosystem to low concentrations of cases. With the exception of the San Bernardino sulphur dioxide emissions originating from a Mountain study investigating the effects of ''sour gas" processing plant in Alberta, Canada photochemical oxidants on a mixed conifer forest (Legge and otters 1978). ecosystem in California (Miller and others, 1977;

BACKGROUND TO THE CASE STUDY

^presented at the Symposium on Effects of Air Potential detrimental environmental impact of Pollutants on Mediterranean and Temperate Forest sulphur dioxide emissions from the sour gas proc- Ecosystems, June 22-27, 1980, Riverside, cessing industry upon the environment in Alberta California, U.S.A. was a major concern of this industry in the early

2~rofessional Associate, Kananaskis Centre for 1970's. This concern lead to the formation of

Environmental Research, University of Calgary, the Whitecourt Environmental Study Group (WESG)

Calgary, Alberta T2N 1N4 Canada in 1971, a consortium of eight companies involved

in the production of saleable natural gas from sour gas (natural gas containing hydrogen sulphide) in the Whitecourt district of west-central Alberta. It was clear at that time that the assessment of the impact of sulphur dioxide on the forest ecosystem was not a simple cause and effect relationship. A five-year environmental research program therefore was initiated in 1972 and was cooperatively funded by both industry and the Alberta Government. The objective of the research program which was called the Whitecourt Environmental Study was to determine the environmental consequences of the operation of sour-gas processing facilities on the forest ecosystem in the Whitecourt district occupied by 11 sour gas processing plants and defined as the Whitecourt study area (figure 1).

Figure 1. Map of western Canada showing in bold outline the province of Alberta and the Whitecourt Study Area.

The Whitecourt study began in 1972 as a remote sensing airborne environmental survey accompanied by assessment on the ground carried out by INTERA Environmental Consultants Limited to determine if there were any visible large scale environmental disturbances. After two years of general re- connaissance no large scale environmental disturbance was found (Whitecourt Environmental Study 1972 and 1973). Controlled SO2 fumigation experiments carried out in the laboratory by the Kananaskis Centre for Environmental Research, University of Calgary, on young lodgepole pine (Pinus contorta Loud.) seedlings, however, revealed a direct effect of SO2 on vegetation. These experiments showed that, although plants have the ability to adjust physiologically within certain environmental limits, plants were adversely affected when these limits were exceeded (Legge and Harvey 1974). A conflict therefore arose; the general environmental field survey indicated no large scale modification of the vegetation while the preliminary laboratory

research indicated the potential for environmental change in the field due to sulphur dioxide exposure. To resolve these contradictory research results it became clear that a detailed field case study of a forest ecosystem surrounding a sulphur dioxide source was required.

The AMOCO Petroleum Company Limited West Whitecourt (Windfall) sour-gas processing plant was chosen for the case study. This gas plant had the longest operational history in the Whitecourt study area beginning operation in 1962.

SOURCE OF SULPHUR GAS EMISSIONS

The following is a brief outline of the operation of the West Whitecourt sour-gas processing and sulphur recovery plant to familiarize the reader with the origin of sulphur gas air pollution from the sour-gas processing industry in Alberta.

Hydrogen sulphide is the principle sulphur compound present in sour natural gas and is removed by a series of chemical processes in a sulphur recovery gas plant as elemental sulphur. The H2S not converted to elemental sulphur is incinerated in a high temperature reaction furnace (580' Celcius) in excess air and methane where it is oxidized to sulphur dioxide (SO2) and vented to the atmosphere from a tall (122 meter) "candy- striped" incinerator stack. In addition to an incinerator stack, smaller stacks called flare stacks, generally less than 46 meters in height,

- TOTAL EMISSIONS/MONTH - - MAIN STACK/MONTH . . . .... . . .. ,. . . FLARE STACK 1 MONTH

3 2 0 0

Figure 2. Monthly sulphur emission history of the West Whitecourt Gas Plant from 1970 through 1976.

are used to burn small waste quantities of sulphur recovery gas plant process and compressor gases. Except in the case of a gas plant operational upset, when for short periods the flare stack may contribute more sulphur gas emissions to the atmosphere on a daily basis than the incinerator stack, the incinerator stack is the main source of sulphur gas emissions from the West Whitecourt Plant.

The monthly sulphur emissions (in long tons) of the West Whitecourt Gas Plant for 1970 through 1976 is shown in figure 2; simply double the sulphur emissions to obtain the SO2 emissions. It is important to note that this gas plant has reduced its sulphur emission output per day an order of magnitude since start-up in 1962 from 150 long tons/day to 18 long tonslday in 1976. This reduction was achieved by enhanced operating procedures and the addition of "tail-gas" recovery units.

SULPHUR: THE NUTRITIONAL CONTROVERSY

Sulphur is an essential nutrient element for normal plant growth and metabolism. It is required in intermediary metabolism and is a con- stituent of many organic compounds such as amino acids and proteins in plant tissue. Sulphur normally enters the plant via the root system in the form of sulphate, which is biochemically reduced and then converted into numerous organic compounds. Plants, however, can also take-up and utilize SO2 from the atmosphere via the stomates and utilize it as sulphur source for plant nutrition. Faller (1971), for example, has shown that tobacco plants can utilize SOy as a source of sulphur in sulphur deficient soils. This type of information has led many government and industry departments to say that SO2 emitted from industrial sources is actually beneficial as an aerial fertilizer for plants growing on sulphur deficient soils (Terman 1978; Noggle and Jones 1979). The situation is not quite -so simple, however. Though a small amount of atmospheric SOo can be nutritional to plants in the short term, the large amount and high frequency of uncontrolled application of sulphur such as SOy to an ecosystem by sulphur sources such as smelters, pulp and paper mills, coal-fired power plants, oil sand and oil shale extraction plants and sulphur recovery gas plants can be detrimental in the long term. Different plant species not only have different nutritional requirements for sulphur, but the rate at which plant species assimilate sulphur is influenced by many other variables, such as physiological status, age, time during the growing season, temperature, soil nutrient availability, and light intensity to name a few. When more sulphur is available than can be assimilated it is accumulated in the tissue (Ulrich and others 1967; Legge and others 1977; Cowling and Koziol 1978; Thompson and Kats 1978). This foliar sulphur accumulation can reach toxic levels and adversely affect plant

growth (Katz 1949; Linzon and others 1978). The distinction between the assimilation and the accumulation of sulphur of atmospheric origin by plantsmust be addressed in any ecosystem study.

CONCEPTUAL APPROACH TO CASE STUDY

To carry out an ecosystem case study one must have a basic understanding of what an ecosystem I s . The ecosystem is the basic functional unit of ecology since it includes both the living organism and the non-living environment in which these organisms live. Odum (1971) has defined an ecosystem as "any unit that includes all of the organisms in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity and material cycling within the system". Due to the inseparable nature and interdependence of the components of ecosystems upon one another, however, any change that occurs in one component of the ecosystem potentially affects all the components of that ecosystem. The higher the diversity of an ecosystem therefore the more numerous the interrelationships within the ecosystem (Jernelou and Rosenberg 1976). The stability of an ecosystem can be viewed as a function of the balances amongst the components of that ecosystem. An environmental stress such as air pollution can modifiy the stability of an ecosystem by disrupting the balance amongst the ecosystem components.

Prior to the initiation of the West Whitecourt case study, it was recognized that an ecosystem study was an interdisciplinary undertaking. The term interdisciplinary in this context means the amalgamation of a set of specific disciplinary talents to work together to address a complex environmental problem. An interdisciplinary research team was assembled by the Kananaskis Centre for Environmental Research of the University of Calgary, The University of Alberta, The University of Washington, San Jose State University and the Southern Alberta Institute of Technology. The scientific expertise of the research team was broadly based and ranged from remote sensing, ecology, taxonomy, genetics, plant physiology, analytical chemistry, biochemistry, stable isotope physics and meteorology to statistics and electrical engineering.

A conceptual model was developed to illustrate the dynamic relationship between the sulphur dioxide "source" and the generalized ecosystem "sink" and is shown in figure 3. For purposes of communication among disciplines, the ecosystem was sub-divided into the following four compartments: air, vegetation, soil, and water. The two- way arrows indicate the inter-relationship of the four ecosystem compartments. The expertise of each member of the research team was thus focussed on more than one of the ecosystem compartments at all times. This lead to the formulation of cooperatively designed experiments to evaluate not

VEGETATION

WATERu Figure 3. Conceptual model of the forest ecosystem in the West Whitecourt case study area.

only the interfaces between ecosystem compartments but also the processes within the ecosystem compartments. Scientists with different areas of expertise were brought into the case study, however, as a function of the needs of the research program. The selection and the timing of interaction of disciplinary participants were viewed as critically important factors for the success of the program so the case study grew in terms of disciplinary participation from 7 in 1974 to 10 in 1975 and finally to 12 in 1976 and.1977. This evolutionary interdisciplinary approach added a dimension of insight into the fate of sulphur gas emissions in the forest ecosystem that would not have been possible had the separate disciplines of the research team been operating in isolation.

VEGETATION CHARACTERIZATION

The vegetation of the Whitecourt area is included in the predominately forest subregion of the Boreal Forest Region of Canada (Halliday 1937) and is characterized as a transition forest area between the Boreal and Subalpine Forest Regions. The transitional nature of the common species of trees occurring in the area are actually represented by populations of hybrid individuals between lodgepole pine (Pinus contorta Loud.) and jack pine (Pinus banksiana Lamb.), while the true fir in the area represents hybrids between alpine fir [Abies lasiocarpa(Hook.) Nutt.] and balsam

fir [Abies balsamea (L.) Mill.] (Legge and others

A physiognomic classification of the vegetation communities in the West Whitecourt study area identified 13 major cover types out of 24 community types. Ten climax vegetation associations were recognized. The vegetation of the study area was mapped using a combination of LANDSAT imagery, LANDSAT digital data and conventional false colour infrared aerial photography both of which were accompanied by ground based verification. With the aerial colour infrared photography of the West Whitecourt study area as a subsample, computer mapping utilizing LANDSAT digital data was completed on 116,000 hectares to place the study area in a regional perspective. The computer mapping of the study area was eight times faster than conventional photography alone and had a comparative accuracy of 93 percent.

ECOLOGICALLY ANALAGOUS SITES

One of the principle difficulties encountered by air pollution researchers, before collecting samples in the field for analysis, is the selection of sampling locations. Most sampling locations in air pollution studies are chosen solely on the basis of a gradient which is usually a function of the prevailing wind and the distance from a pollution source. Not enough emphasis is placed upon the structure and composition of the plant communities from which samples are taken. Since an ecosystem is composed of many interrelated highly variable biological and physical components, the response of these components to a chronic environmental stress such as air pollution will also be highly variable. If the range of variability of the responses of ecosystem components to an environmental stress is not considered, the expression of the effect of the environmental stress on the ecosystem components may not be detected. There must be a common basis for comparison of ecosystem components therefore to determine both the gross and subtle effects of an environmental stress along a gradient.

The concept and criteria for ecologically analogous sample site selection were developed and applied during the West Whitecourt case study in an attemot to minimize the variability of ecosystem components and hence to minimize the variability of the response of the ecosystem components to air pollution stress. The key to this concept of sample site selection is based upon comparable ecological variability of the ecosystem components and comparable environmental variability at the sampling locations chosen along a distance gradient. The criteria for ecologically analogous sample site selection are summarized in Figure 4. When the ecological and environmental variation of ecosystem components at all the sam~ling locations are as similar as possible, the sampling sites are said to be ecologically analogous. The major difference amongst the sampling locations

ECOLOGICAL ANALOGUE CONCEPT

ASSUMPTIONS 1 = 2 + 3

1. Ecological Variables (sites A, +An ) slope soil moisture aspect species density soil type species diversity

2. Environmental Variables (other than pollutants) temperature solar radiation wind precipitation

3. Pollutant Variables composition location distance concentration/conversion frequency/duration

Figure 4. Summary of criteria utilized for the selection of ecologically analogous sample sites.

therefore is distance from the pollution source. The assumption is that the pollutant variables such as concentration, frequency of fumigation and duration of fumigation will decrease in magnitude with increasing distance from the pollution source. The magnitude of the air pollution stress on ecosystem components at the sampling locations will correspondingly decrease with increasing distance from the pollution source. This procedure ensures that the expression of the air pollution stress on ecosystem components will be maximized.

Meteorological and air quality data were essential in sample site selection. The prevailing winds during the growing season in the study area were shown to have the highest frequency of occurrence from the WNW and the second highest frequency from the ESE. Sulphur dioxide emissions from the West Whitecourt Gas Plant therefore occurred with greatest frequency in an ~ S E corridor. Although idealized, the corridor concept provided an essential point of reference for the areas chosen for the selection of sampling locations in the West Whitecourt study area.

The range of distances at which maximum ground level concentrations would occur from sulphur gas emissions from the main incinerator stack and flare stacks was calculated using the simple Gaussian plume model under mean wind conditions and a wide range of stability classes. The maximum ground level concentrations would occur between 1.6 and 34.0 km downwind of the incinerator stack and between 0.4 and 2.6 km

downwind of the West Whitecourt Gas Plant. The intensive experimental site therefore, was principally exposed to sulphur gas emissions from the flare stacks. Only under short-lived meteorological conditions such as would occur during the break-up of an inversion would sulphur gas emissions from the main incinerator stock reach the intensive experimental site.

It must be emphasized at this point that the air quality standards for SO2 of 0.2 ppmh hr. / 24 hr. as set by the Alberta Department of the Environment, were only exceeded on three occasions at the intensive experimental site 1.5 km east of the West Whitecourt Gas Plant in over 2500 hours of ambient air monitoring during the 1975 and 1976 growing seasons in the West White- court study area.

Five ecologically analogous lodgepole x jack pine sampling locations were selected in the West Whitecourt case study area. The five sample sites were chosen in locations which were prog- ressively downwind in the main path of sulphur dioxide emission corridor. These sites were chosen in this manner so that the sulphur dioxide emission impact gradient would be very steep across the five sampling locations to maximize the differences in the responses of the ecological analogues to pollution stress. The conceptual ecological model presented in Figure 3 can be generalized to express the relationships amongst the five ecological analogues and is shown in Figure 5. The ecologically analogous sampling

IMPACT GRADIENT

SOURCE SINK

Figure 5. Replicated conceptual ecological model illustrating the five ecologically analogous lodgepole x jack pine sampling locations along a sulphur dioxide concentration gradient.

sites were located at distances of 1.2 km (A=), 2.8 km (AII), 6.0 km (AII~), 7.5 km (AIv) and 9.6 km (Av) from the Gas Plant. Sampling locations in the study area other than ecological analogues were designated by the letter S.

CASE STUDY DATA OVERVIEW

Foliar sulphate-sulphur concentration in lodgepole x jack pine trees was found to be a better measure of foliar sulphur accumulation than the foliar total sulphur concentration. The method of Johnson and Nishita (1952) was used to determine foliar sulphate-sulphur concentration while a Leco Furnace was used to determine foliar total sulphur. Figure 6 shows a plot of foliar sulphate-sulphur concentration in age-classed lodgepole x jack pine

I I W x t Whilmcourt Study Area --Pinut contort0 a P.banktiam-

1 Birch Mountain Firm Tmw Pinut bonkeiana K R contww

1 0 0 ' , I , , , , , 6 4 2 KILOMETERS WEST KILOMETERS EAST 4

Figure 6. Plot of foliar sulphate-sulphur concentration in age-classed lodgepole x jack pine foliage from eight sampling locations in the West Whitecourt study area as a function of distance from the West Whitecourt Gas Plant.

foliage as a function of distance from the West Whitecourt Gas Plant. The background foliar sulphate-sulphur concentration was determined from age-classed foliage of jack pine x lodgepole pine from the Birch Mountain Fire Tower Ill km (69 mi) NNW of Fort McMurray, Alberta. One can clearly see the decrease in foliar sulphate-sulphur concentration with increasing distance from the sulphur gas emission source. The decrease in foliar sulphate-sulphur concentration with distance was more pronounced with

increasing foliar age. The foliar sulphate-sulphur data strongly support the concept of an environmental stress gradient presented earlier.

The stable sulphur isotopic composition ( s / s3' ratio) of sulphur dioxide emissions from sour gas plants in Alberta have been shown to differ from the natural environmental background stable sulphur isotopic composition (Lowe and others, 1971; Krouse, 1977). This is referred to as the 6 3 4 ~ value. The more positive the 63 S value the

The background greater the enrichment in s ~ ~ . stable sulphur isotopic composition in the West Whitecourt study area is near 0.

The stable sulphur isotopic composition of sulphur dioxide emissions from the incinerator stack at the West Whitecourt Gas Plant was shown to be +22.2'/00 (per thousand). This difference provided an environmental tracer for sulphur of industrial origin.

The mean 6 3 4 ~ value of 1974-1976 foliage from the ecologically analogous sampling locations AI through Av remained close to the mean 6 3 4 ~ value for the incinerator stack at +22.2' loo while the mean foliar sulphate-sulphur concentration in 1974-1976 foliage decreased from 422 ppm to 185 ppm. These data clearly show that lodgepole x jack pine trees were obtaining some of their sulphur directly from the atmosphere from sulphur gas emissions originating from the West Whitecourt Gas Plant. Needles in the upper crowns of many lodgepole x jack pine trees in the West Whitecourt study area, however, displayed foliar @S values which were greater than those associated with incinerator stack emissions. These data when compared to the laboratory data of Wilson and others (1978) was suggestive of iso- topically selective metabolic processes functioning in the lodgepole x jack pine foliage under field conditions .

The 28-meter radio mast tower erected at the intensive experimental site provided a framework for measuring and characterizing SO2 concentration profiles of ambient air above, within and below the lodgepole x jack pine forest canopy. The vertical SO2 profiles revealed that the SO2 concentration minimum measured in the upper crown at 16 meters was orimarily due to an aerodynamic effect and was not due to the trees acting as a biological sink. This aerodynamic effect was described as a splitting of the air flow above and below the crowns of the lodgepole x jack pine trees. The measurements of foliar sulphate- sulphur, foliar total sulphur and foliar S S values revealed that the trees, however, were also a biological sink for sulphur gas emissions but that the rate of atmospheric sulphur uptake by the trees was so slow that it was beyond the resolution of the two Thermo Electron Model 43 Pulsed Fluorescent SO2 analyzers used.

Photosynthetic rates and leaf resistances of lodgepole x jack pine trees in the West Whitecourt study area were shown to be modified. The amount

of this ecological modification was a function of the distance from the West Whitecourt Gas Plant. For example, the seasonal photosynthetic rates of 1976 lodgepole x jack pine foliage were lower and the leaf resistances higher when foliage from S5 (1.5 km east) was compared with foliage from Sin (5.2 km east) (4.38 Â 1.99 mg C02/dry g/hr versus 6.42 Â 1.28 mg C02/dry g/hr and 11.3 2 6.6 s/cm versus 7.8 5 1.9 s/cm for sample sites S5 and Sin respectively). This relative reduction in photosynthetic rates, however, was only partially attributable to increased leaf resistance. Additional ecological factors therefore, such as foliar mineral nutrient status and soil pH were considered since these parameters were known to modify plant response.

A detailed analysis of foliar mineral nutrient concentration of N, P, K, Ca, Mg, Mn, Al, Fe and Zn in lodgepole x jack pine foliage from nine sampling locations (including the ecological analogues) in the West Whitecourt study area revealed that the mineral nutrient status of the lodgepole x jack pine trees had been altered. It must be remembered at this point that normal plant growth requires a balance of all essential mineral nutrients within the plant. The foliar concentration of P, K, Fe, Mg, N and Zn tended to increase while the foliar concentration of Ca and A1 tended to decrease with distance from the West Whitecourt Gas Plant and distance from the WN-SE sulphur dioxide emission corridor. Site type was shown to be a critical factor influencing the concentration of these eight mineral nutrients. Foliar Mn concentration was found to decrease dramatically with distance from the West Whitecourt Gas Plant and distance from the WNWSE sulphur gas emission corridor. Variability of site type, however, did not modify this relationship. A low Fe to Mn ratio was found in foliage from sampling locations within 4 km of the West Whitecourt Gas Plant. The low foliar Fe concentration may contribute to the chlorotic appearance of the foliage at these locations. Foliar mineral nutrient analysis of foliage 82, 85, A1 and Slo revealed that foliar K and P were lower in concentration in foliage from S2, S5 and AT than from Sm.

Since foliar K concentration has been linked with stomatal activity, the reduced foliar K concentration may be inhibiting stomatal opening thus increasing leaf resistance which would then limit photosynthetic rate. Reduced foliar P concentration may inhibit phosphorylation and thereby also limit photosynthetic rate. Foliar nutrient deficiencies of either P and K alone or in combination therefore may be partially responsible for the reduced photosynthetic rates observed in lodgepole x jack pine foliage in the West Whitecourt study area.

The alteration of foliar mineral nutrient status in lodgepole x jack pine trees in the West Whitecourt study area therefore is an important ecological factor contributing to the modification of plant response.

Soil pH profiles were measured at the same nine vegetation sampling locations where foliar mineral nutrient concentrations were determined since soil pH is known to affect the availablility of mineral nutrients to plants. The general trend or gradient in soil pH over all nine sampling locations was an increase in soil pH with depth and with distance from the West Whitecourt Gas Plant and

Edistance from the ~ S sulphur gas emission corridor. The soil pH gradient was most striking when only the ecologically analogous sampling locations were considered. A direct relationship was found between lowered soil pH and the elevated levels of foliar Mn in lodgepole x jack pine trees. The foliar Mn concentration data and the soil pH data suggest that foliar Mn concentration in lodgepole x jack pine trees could be used as a mineral nutrient indicator of modification of the forest ecosystem by sulphur gas emissions.

Soil total sulphur concentration in the soil profiles at the nine soil sampling locations also decreased with soil depth, distance and direction from the West Whitecourt Gas Plant. It is important to note, however, that there was no correlation between soil total sulphur concentration and soil pH. There was also no direct correlation between a given soil pH value and the soil f i 3 % value. These data suggest that the soil S S value can be used as an indicator of the presence and penetration of sulphur gas emissions into the soil profile while soil pH and soil total sulphur can be used as indicators of sulphur loading of the soil.

In terms of plant biochemistry and sulphur gas emissions the most significant observation in the field was a transient metabolic effect; the ATP (adenosine triphosphate) concentration of foliage cells from lodgepole x jack pine trees was found to be directly decreased upon exposure to low-concentration short duration SO2 fumigation (75% decrease upon fumigation with 0.14 ppm SO2 for 15 minutes). It is important to note that when the foliage was no longer exposed to SO2 the foliar ATP concentration increased to the pre- SO2 fumigation ATP concentration (see Harvey and Legge, 1979, for details). This decrease and increase in the foliar ATP concentration was also observed with excised lodgepole x jack pine branches from the West Whitecourt study area which were fumigated under controlled conditions at the Kananaskis laboratory. When lodgepole x jack pine trees, which had been grown in the absence of sulphur gas emissions in the laboratory, were fumigated with SO2 no fluctuation in ATP concentration was observed. It is important to note that the laboratory trees had a foliar ATP content which was over twice the foliar ATP content of the lodgepole x jack pine foliage from the West Whitecourt study area (658 nmoles/dry g versus 1460 nmoles/dry g). The lower foliar ATP concentration of field grown trees compared to laboratory grown trees suggests a partial explanation for the lowered photosynthetic capacities reported for lodgepole x jack pine trees in the West Whitecourt study area.

The photosynthetic rate of lodgepole x jack pine trees grown under controlled conditions in a non-SO2 environment in growth chambers at the Kananaskis laboratory and lodgepole x jack pine trees grown in the sulphur dioxide emission environment in the field at the intensive West Whitecourt study site S5 was measured when both sets of trees were exposed to similar low concentration short-duration SO2 fumigations. The photosynthetic rate of the field grown plant material was not depressed by SO2 fumigation while the photosynthetic rate of the laboratory grown material was depressed by the SO2 fumigations. The photosynthetic rate of the laboratory trees was much greater than the trees in the field. There was also no evidence of a plant- water deficit in lodgepole x jack pine trees severe enough to effect photosynthetic rate.

Adenosine triphosphate is the major biochemical intermediate of energy transfer in biological systems. A decrease in foliar ATP content in lodgepole x jack pine trees caused by SO2 fumigation therefore would also be a decrease in the amount of biochemical energy available for normal metabolic functions. Al- though the ATP content of the lodgepole x jack pine foliage recovered to the pre-SO2 exposure concentration after the SO2 stress was removed, during the SO2 fumigation there would have been a net loss of biochemical energy. The fact that foliar ATP content increased after SO2 fumigation, indicated that the trees were coping with the sulphur gas emissions at the cost of a metabolic energy drain.

In summary, the contrast in the biochemical and physiological responses of the lodgepole x jack pine trees fumigated with SO2 in the field and the laboratory strongly indicates that environmental pre-history and acclimation of the trees to ecological modification of components of the forest ecosystem are the critical factors determining plant response to sulphur gas emissions in the West Whitecourt study area.

A comparison of the mean photosynthetic capacities of 1976 lodgepole x jackpine foliage through the 1976 growing season at sampling locations S2, S5 and Slo revealed that S10 had a positive net C02 fixation balance two to three weeks prior to the foliage at S2 and S5 and is shown in Figure 7. The mean photosynthetic capacity of 1976 Sin foliage was also always higher than the mean photosynthetic capacity measured for 1976 foliage from S2 or S5 . Addi-tionally in terms of photosynthetically active needle biomass lodgepole x jack pine branches sampled at Sl, 82, AI and S5 were chlorotic in appearance with premature abscission (needledrop) of the third year needles and poor leader growth while branches sampled at Sq and Sin were comparatively darker green in color with a needle retention of from four to six years and good leader growth. The photosynthetic potential of lodgepole x jack pine trees based upon needle biomass alone therefore was much greater at S9 and Sin compared to Sl, Sy, A1 or $5.

Figure 7. Comparison plot of the mean photosynthetic capacity of 1976 foliage on lodgepole x jack pine branches from sampling sites S2, S5 and Slo from early in June to mid-September.

When the observed ecological modifications of the forest ecosystem such as reduced needle biomass, reduced biochemical energy, reduced photosynthetic rates, reduced soil pH, the disruption of mineral nutrient cycling, foliar sulphur loading and the shortened growing season are combined, and considered in the long term time sense the net effect should be measurable as a reduction in forest productivity. This decrease in forest productivity, however, would be expected to decrease with increasing distance from the sulphur gas emission source.

Annual basal area increment measurements were taken from 40 lodgepole x jack pine trees at each of the five ecologically analogous sampling locations AI through Av in 1976 to determine if modification of the forest ecosystem was significant enough in the long term sense to be reflected in reduced wood production since the initial start- up of the West Whitecourt Gas Plant in 1961-1962. Statistical analysis of the basal area increment data shown in Figure 8 revealed that distance from the West Wh'itecourt Gas Plant, time in years, and their interaction had significant effects on the basal area increment of the lodgepole x jack pine trees from the five ecological analogues. An exponential growth curve model was determined for lodgepole x jack pine trees from Air and the growth curve of the lodgepole x jack pine trees fromA1, A1l, AIII and AIv were statistically compared to it. The basic underlying assumption was that sulphur gas emissions had not had a significant effect on the growth of the trees at Av. This analysis statistically revealed that there has been a defi- nite reduction in basal area increment in lodgepole x jack pine trees since 1962 in AI, A,.,, AIII and AIv compared to the basal area increment model for AV which was attributable to sulphur gas emissions from the West Whitecourt Gas Plant.

l l I I I I I 1950 1955 1960 1965 1970 1975

YEAR O F GROWTH

Figure 8 . Comparative p l o t s of the mean basa l a r e a increments from 40 lodgepole X jack pine t r e e s a t each of the f i v e eco log ica l ly analagous sampling s i t e s i n the West Whitecourt study a r e a .

The maximum reduc t ion i n b a s a l a rea increment occurred a t A 1 and A 1 1 and p rogress ive ly decreased t o zero a t Ay. The e f f e c t of sulphur gas emissions on b a s a l a r e a increment growth i n lodgepole x jack pine t r e e s s ince 1961 a t AI, AII, AIII, and AIv r e l a t i v e t o Av i s thus a g r a d i e n t wi th the reduc t ion i n b a s a l a r e a increment r e s u l t i n g from sulphur gas emission f a l l i n g t o ze ro a t Av o r 9.6 km. I f the t o t a l b a s a l a r e a increment reduc t ion of AT r e l a t i v e t o Av i s averaged over the four teen years s ince t h e s t a r t - u p of the West Whitecourt Gas P l a n t , t h i s would correspond t o approximately a one t o two percen t r educ t ion i n b a s a l a r e a incre-ment growth of AI r e l a t i v e t o Av.

The a r e a l e x t e n t of poss ib le modif icat ion of components of the f o r e s t ecosystem by sulphur gas emission from the West Whitecourt Gas P l a n t can be es t imated using the following assump-

t ions : 1. sulphur gas emissions reach the f o r e s t

ecosystem wi th in 17 km. (10.6 mi.) of the source; and

2. the impact of sulphur gas emissions is r e s t r i c t e d t o a r e a s NW and SE of the West Whitecourt Gas P l a n t .

The a r e a a f fec ted by sulphur dioxide emiss i n s , the re fo re , i s approximately 454 km 2 (175 m i5) o r 45,373 h e c t a r e s (112,130 a c r e s ) . This a r e a l ex ten t e s t imate of impact i s conse rva t ive because t h e 17 km d i s t a n c e i s only one-half the d i s t a n c e range ca lcu la ted using the simple Gaussian plume model under a l l s t a b i l i t y c l a s - s e s f o r maximum ground l e v e l concen t ra t ion of sulphur dioxide emissions from the main i n - c i n e r a t o r s t a c k .

It i s important t o bear i n mind a t t h i s p o i n t , however, t h a t t h i s projected impact a rea has no t been uniformly modified by su l - phur gas emissions but r a t h e r has been mod- i f i e d i n terms of an impact g rad ien t extending NW and SE from the West Whitecourt Gas P l a n t . I n o t h e r words, the e x t e n t of ecosystem component modif icat ion w i l l decrease wi th d i s - tance from the sulphur gas emission source.

Another f a c t o r must be considered a t t h i s p o i n t . Sulphur emissions from the West White- cour t Gas P l a n t have been reduced almost a n o rder of magnitude s ince 1970 ( r e f e r t o Fig- u re 2 ) . This s i g n i f i c a n t reduct ion i n emissions w i l l no t only genera l ly decrease the magnitude of the impact ,of sulphur emissions on the f o r - e s t ecosystem, i t w i l l a l s o decrease the a r e a l ex ten t of the a r e a impacted by sulphur emissions i n the p a s t thus allowing a por t ion of the f o r - e s t ecosystem t o recover from the previous sulphur gas emission s t r e s s .

When one uses f o l i a r sulphate-sulphur con-c e n t r a t i o n i n lodgepole x jack pine t r e e s a s a measure of sulphur accumulation from exposure t o the c u r r e n t l e v e l of sulphur gas emissions, i t appears t h a t a t o l e r a b l e concen t ra t ion i s reached by 9-12 km (5.6-7.5 mi) of the West Whitecourt Gas P l a n t . This i s ind ica ted by a decrease i n f o l i a r sulphate-sulphur concen t ra t ion with needle age which i s w i t h i n the range of t h e background f o l i a r sulphate-sulphur con-c e n t r a t i o n . The f o l i a r &^s va lues , however, could be used t o provide a more exac t measure of the d i s t ance a t which the presence of su l -phur gas emissions become n e g l i g i b l e t o com-ponents of the f o r e s t ecosystem.

CONCLUSI O N It i s c l e a r from t h i s c a s e study t h a t s u l -

phur gas emissions from the West Whitecourt Gas P l a n t have modified the f o r e s t ecosystem i n a number of ways. The main eco log ica l pro- c e s s which has been d i r e c t l y and i n d i r e c t l y a f f ec ted by sulphur dioxide emissions i s min- e r a l n u t r i e n t cyc l ing . By p rogress ive ly a l t e r - ing the mineral n u t r i e n t balances of ecosystem components f o r example, the b i o l o g i c a l r e -l a t i o n s h i p s amongst the components and the phys io log ica l and biochemical func t ions of the components a r e modified. It i s these ecosystem

component modifications which are the expressions of environmental deterioration re-sulting from chronic exposure to sulphur dioxide over time. Despite this measurable deterioration of the forest ecosystem, however, it does not appear at this time that sulphur dioxide emissions from the West Whitecourt Gas Plant have caused irreversible ecological degradation. With the significant reduction in sulphur emissions from the West Whitecourt Gas Plant (See Figure 2) it is not anticipated that there will be significant irreversible ecological modification of the forest ecosystem in the remaining 10 to 20 years of operation of the West Whitecourt Gas Plant.

One philosophical dilemna has resulted from the West Whitecourt case study. There is no relationship between air quality standards and the maintenance of environmental quality since the term environmental quality excludes environmental modification. No effort to date has been made to address or to quantify acceptable limits of environmental modification resulting directly or indirectly from air pollution stress despite the fact that the presence of air pollutants in the atmosphere implies that a certain amount of environmental modification is acceptable.

Since, at the present time it is techno- logically and economically impossible to remove all air pollutants from industrial processes, it is suggested that irreversible ecological modification of the environment be used as an additional criteria for limiting pollutant emissions to the atmosphere. The assimilatory capacity of the environment, in other words, must be taken into account by both industry and regulatory agencies. The uniform application and enforcement of fixed air quality standards over a geographical area the size of the p ovince of Alberta (661,183 km2 or 255,285 mi 5) with its physiographically complex terrain, heterogeneous vegetation and diverse climatology is clearly not enough to maintain environmental quality. Future research will be required to determine the assimilatory and accumulatory capacity of the environment to pollutants and to provide the biological monitoring techniques to assure that the assimilatory and accumulatory capacity of the environment is not exceeded.

After the assimilatory and accumulatory capacity of the environment have been considered, flexible air quality standards may be possible. These standards could be ad- justed regionally and seasonally in order to minimize pollutant impact on the environment. All emission sources, however, would have to be viewed in the context of their regional location, projected longevity of their operations, composition of their emissions, the proximity of neighboring emission sources as well as regional land use priorities since it is the total pollutant load to the environment which must be considered when one uses assimilatory capacity as a measure of environmental quality.

The conceptual interdisciplinary nature of the West Whitecourt case study has proven to be the basis for the success in unravelling the very complex interrelated consequences of the chronic exposure of the forest ecosystem to sulphur gas emissions from the West White- court Gas Plant. It is suggested that future air pollution research on forest ecosystems follow a similar experimental design if the environmental perturbations caused by air pollution stress are to be understood. Direct extrapolation of the data summarized in this paper to other areas would be mis- leading unless local environmental factors, vegetation and pollutant parameters, are taken into consideration prior to interpretation.

ACKNOWLEDGMENTS

The West Whitecourt Case Study could not have been completed without the enthusiasm and cooperation of the following interdisciplinary team members: D.R. Jaques, G.W. Harvey, H.R. Krouse, H.M. Brown, E.C. Rhodes, and M. Nosal of the University of Calgary; H.U. Schellhase of the Southern Alberta In- stitute of Technology; J. Mayo and A.P. Hartgerink of the University of Alberta; P.F. Lester from San Jose State University; and R.G. Amundson and R.B. Walker of the University of Washington.

The majority of the financial support for this research was in the form of a grant-in- aid of research to the Kananaskis Center for Environmental Research of the University of Calgary from the Whitecourt Environmental Study Group. Additional financial support was received from the Research Secretariat of Alberta Environment, the Oil Sands En- vironmental Study Group (OSESG) , the Alberta Oil Sands Environmental Research Program (AOSERP), and the University of Calgary Inter- disciplinary Sulphur Research Group (UNISUL) .

A special note of thanks is in order for Mr. Ron Findlay and Mr. E. Baraniuk of AMOCO Canada Petroleum Company Limited and the rest of the Whitecourt study group members companies who had the foresight to initiate the White- court Environmental Study and the patience to see it through.

Finally I wish to thank my air pollution colleagues throughout North America for their genuine interest and support during the research program.

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Effects of Airborne F on Forest Ecosystems'

Robert G. Amundson and Leonard H. Weinstein

Abstract : Although t h e r e a r e many r e p o r t s of f l u o r i d e (F) i n j u r y t o f o r e s t s , t h e r e have been no sys temat ic s t u d i e s on t h e f o r e s t ecosystem. I n t h i s paper , we have reviewed t h e p r e s e n t s t a t e of our knowledge on F p o l l u t i o n and e f f e c t s on phys io log ica l p rocesses , t r e e growth, F accumulation and p l a n t i n j u r y , community s t r u c t u r e , i n t e r a c t i o n wi th pathogens and i n s e c t s , and d i s t r i b u t i o n of F i n t h e environment. The p repara t ion of t h i s review i n d i c a t e d t h e many a r e a s of t h e F-plant i n t e r a c t i o n on which t h e r e i s no in fo r -n a t i o n , where i t is poorly understood, o r where a v a i l a b l e informat ion i s h igh ly c o n t r o v e r s i a l . I n some cases , we have jo ined t h e controversy.

I n j u r y t o f o r e s t t r e e s p e c i e s by a i r b o r n e watched c a r e f u l l y . f l u o r i d e (F) has been repor ted i n many p a r t s o f t h e world (e .g . , Adams and o t h e r s , 1952; Horntvedt Resu l t s of only a few f i e l d s t u d i e s made n e a r and Robak, 1975; Niklfeld.1975; EPA, 1973; F l i i i l e r F-emitting sources a r e a v a i l a b l e i n t h e s c i e n t i - and o t h e r s , 1979), but many F-emitt ing sources a r e f i c l i t e r a t u r e . One reason f o r t h e absence of i n a g r i c u l t u r a l o r urban a r e a s and r e p o r t s of more r e p o r t s i s t h a t t h e s t u d i e s were o f t e n rou- i n j u r y t o agronomic crops , ornamental and urban t i n e and no t q u a n t i t a t i v e , making p u b l i c a t i o n i n t r e e s ( e .g . , Bolay and Bovay, 1965; Facteau and re fe reed j o u r n a l s d i f f i c u l t . A second reason is Mel lenthin , 1976; de Ong, 1946; Leonard and Graves, t h a t r e s u l t s of a s tudy performed f o r an i n d u s t r y 1966) o r on f l u o r i d e accumulation and product ion may b e sequestered from p u b l i c a t i o n o r o t h e r use of f l u o r o s i s i n l i v e s t o c k and o t h e r he rb ivores because of a c t i v e , pending, o r p o t e n t i a l l i t i g a - ( S u t t i e , 1977) a r e a l s o common. t i o n . Often, f i e l d s t u d i e s t h a t have been d i s -

t r i b u t e d were i n a form t h a t was n o t sub jec ted t o The p r i n c i p a l i n d u s t r i a l sources of a i r b o r n e pee r review, was c a r e l e s s l y assembled, and/or

F a r e primary aluminum smel t ing; s t e e l manufacture; r e f l e c t e d t h e pe r sona l b i a s e s of t h e au thors . conversion of f l u o r a p a t i t e t o phosphate and phosphorus; and g l a s s , ceramic and b r i c k product ion. Because of t h e s e problems, we have n o t confined Na tu ra l sources of a i r b o r n e F a r e p r i n c i p a l l y t h i s review t o works publ ished i n j o u r n a l s , b u t from s o i l p a r t i c l e s , fumaroles, and volcanoes. we have t r i e d t o judge t h e r e p o r t s t h a t we have The ash from t h e r e c e n t e r u p t i o n of Mount S t . c i t e d i n terms of t h e i r pe r t inence and/or a v a i l - Helens conta ined 8 ppm s o l u b l e F (S to ibe r and a b i l i t y , and our pe r sona l views a r e o f t e n pre- o t h e r s , 1980) and 400 ppm t o t a l F and i t s impact sented. Host i n t e r n a l r e p o r t s were avoided, bu t on f o r e s t s i n t h e nor thwestern U.S. w i l l be t h e l a c k of publ ished informat ion o f t e n l e f t no

recourse b u t t o c i t e them. We hope t h a t we have s t a t e d our c r i t i c i s m s of some s t u d i e s a s f a i r l y

p r e s e n t e d a t t h e Symposium on E f f e c t s of A i r a s p o s s i b l e . P o l l u t a n t s on Mediterranean and Temperate Fores t Ecosystems, June 22-27, 1980, R ive r s ide , C a l i f o r n i a , U.S.A. LABORATORY STUDIES ON PLANT PRODUCTIVITY

zResearch Associa te and Program D i r e c t o r , The p r o d u c t i v i t y of t h e p l a n t depends upon t h e

Environmental Biology, r e s p e c t i v e l y . Boyce coord ina t ion and r a t e o f CO-; a s s i m i l a t i o n , res-Thompson I n s t i t u t e a t Cornel l Unive r s i ty , I t h a c a , p i r a t i o n , t r a n s p i r a t i o n , t r a n s l o c a t i o n of photo- New York. syn tha te , mineral n u t r i t i o n , growth, and repro-

duct ion. The amount of informat ion a v a i l a b l e on

t h e impact of a i r b o r n e F on t h e s e processes ranges from v i r t u a l l y none, e .g . , on t r a n s l o c a t i o n of photosynthates , t o a moderate amount, e.g. , on C02 a s s i m i l a t i o n (apparent photosynthesis) and r e s p i r a t i o n .

There a r e few d a t a on t h e chemical composi- t i o n , d i s t r i b u t i o n , and p a t t e r n s and frequency of exposure of atmospheric F i n t h e f i e l d . One reason f o r t h i s i s t h a t a i r moni tors wi th s h o r t averaging t imes have no t been genera l ly a v a i l a b l e . Because F concen t ra t ions i n t h e am- b i e n t a i r have n o t been c h a r a c t e r i z e d and f luc - t u a t i n g F concen t ra t ions a r e d i f f i c u l t t o c o n t r o l , t h e des ign of meaningful l a b o r a t o r y o r c o n t r o l l e d f i e l d experiments i s formidable. The informat ion t h a t is a v a i l a b l e i s g e n e r a l l y f o r averaging t imes of 12 o r 24 hours (McCune and o t h e r s , 1976) and t h e peak F concen t ra t ions t h a t occur nea r sources a r e n o t known. This informat ion would b e ve ry u s e f u l s i n c e i t has been shown f o r o t h e r a i r p o l l u t a n t s , such a s S02, t h a t shor t - term peak exposures a r e more important i n exp la in ing p l a n t damage than average concen t ra t ions (McLaughlin and o t h e r s , 1979). Unfor tunate ly , most l a b o r a t o r y s t u d i e s have employed continuous exposures a t cons tan t concen t ra t ions t h a t do n o t s imula te f i e l d exposures. For t h e s e reasons t h e d a t a a v a i l a b l e a r e of l i m i t e d va lue i n p r e d i c t i n g t h e impact of a i r b o r n e F on f o r e s t ecosystems.

Gas Exchange

Apparent Photosynthesis

Given t h e problems o u t l i n e d above, i t i s no t s u r p r i s i n g t h a t t h e r e have been s o few s t u d i e s on t h e e f f e c t s o f F on apparent photosynthesis (AP) of f o r e s t tree s p e c i e s (Table 1 ) . Consequently, we have included i n Table 1 n o t only s t u d i e s on f o r e s t t r e e s b u t a l s o those on h o r t i c u l t u r a l s p e c i e s exposed t o hydrogen f l u o r i d e (HF) o r supp l i ed wi th sodium f l u o r i d e (NaF). We have a r b i t r a r i l y separa ted experiments wi th HF i n t o a c u t e exposures (over 1 0 pg m 3 f o r a few 'days o r l e s s ) and chron ic exposures (ca. 5 \E HF m 3 o r l e s s f o r a few days t o more than a growing season) , a l though we recognize t h a t many exposures c l a s s i - f i e d a s ch ron ic could more r e a l i s t i c a l l y be c l a s s i f i e d a s acute . Exposures t o s o l u t i o n s con-t a i n i n g NaF have v a r i e d from s e v e r a l hours t o months and w i l l be discussed i n d i v i d u a l l y .

Acute exposures -- With t h e except ion of c o t t o n , where h igh concen t ra t ions of HF had no e f f e c t (Thomas, 1958) , a c u t e exposures have c o n s i s t e n t l y reduced AP (Thomas and Hendricks, 1956; Thomas, 1958; H i l l , 1969; Bennett and H i l l , 1973). Bennett and H i l l (1973) exposed a l f a l f a t o HF f o r 2 hours and found t h a t (1) approximately 120 yg m-3 HF were needed t o produce f o l i a r n e c r o s i s ; (2) about 40 pg m-3 were necessary t o c l e a r l y i n h i b i t AP; (3) t h e depress ion of AP and subsequent recov-e r y a f t e r exposure were slower f o r HF than f o r t h e o t h e r major a i r p o l l u t a n t s t e s t e d (S02, 03, N02, NO and Cl2). They a l s o noted t h a t of t h e pol lu- t a n t s t e s t e d , HF p roduced- the g r e a t e s t r educ t ion

i n AP f o r an equ iva len t p o l l u t a n t dose, b u t s t a t e d t h a t t h e occurrence i n the f i e l d of a concentra-t i o n t h a t would produce a 1 0 pe rcen t r educ t ion i n AP would be r a r e . One can conclude t h a t a s i g n i -f i c a n t in f luence of an a c u t e exposure on p l a n t community p r o d u c t i v i t y would l i k e l y b e preceded by l e s i o n s and a b s c i s s i o n o f f o l i a g e .

Chronic exposures -- Several i n v e s t i g a t o r s have repor ted t h a t chronic exposure t o HF had no e f f e c t on AP i f t h e r e was no v i s i b l e i n j u r y ( H i l l , 1969; H i l l and o t h e r s , 1958; Thompson and o t h e r s , 1967), and when f o l i a r i n j u r y occurred, t h e reduct ion i n AP was p r o p o r t i o n a l t o ( H i l l , 1969; Thomas and Hendricks, 1956; Thomas, 1958) o r g r e a t e r than t h e amount of f o l i a g e i n j u r e d (Thomas, 1958, f o r f r u i t t r e e s ; and Woltz and Leonard, 1964, f o r c i t r u s ) . Thomas (1958) proposed t h a t t h e r e is a th resho ld of F concen t ra t ion and d u r a t i o n o f ex-posure f o r each s p e c i e s above which AP is reduced more than can be accounted f o r by c h l o r o s i s and nec ros i s .

McCune and o t h e r s (1976) descr ibed experiments i n which field-grown sorghum was exposed f o r 14 days t o t h r e e concen t ra t ions of HF (0.7, 1 . 7 and 3.5 t o > 5 yg m-3) and AP of t h e whole p l a n t canopy was measured t h r e e t imes d a i l y b e f o r e , dur ing, and a f t e r t h e exposure pe r iods . The lowest HF concen t ra t ion had no e f f e c t on AP; t h e i n t e r - mediate concen t ra t ion reduced AP dur ing t h e expo- s u r e pe r iod , b u t immediate recovery occurred upon c e s s a t i o n o f t h e exposures. P l a n t s sub jec ted t o t h e h i g h e s t concen t ra t ion a l s o had reduced r a t e s of AP f o r t h e f i r s t week. But when t h e HF concen- t r a t i o n was r a i s e d t o g r e a t e r than 5 m-3 on t h e e i g h t h day, seve re f o l i a r i n j u r y occurred, t h e r a t e s of AP dropped d r a s t i c a l l y , and t h e r e was no recovery i n t h e post-exposure pe r iod .

I n an ex tens ive s e r i e s o f experiments, K e l l e r (1977) placed 11 d i f f e r e n t t r e e s p e c i e s ( see Table 1 ) a t varying d i s t a n c e s from a source of a i r -borne F f o r s e v e r a l months and measured r a t e s of AP on t h e whole p l a n t s r e tu rned t o t h e l abora to ry . Exposure t o F produced f o l i a r i n j u r y and a b s c i s s i o n , and reduced t h e r a t e o f AP of t h e whole p l a n t . The reduc t ion i n AP of t h e whole p l a n t was due p r i m a r i l y t o t h e l o s s of f o l i a g e , because t h e r a t e of AP of needles remaining on t h e p l a n t s was a s h igh a s those on c o n t r o l p l a n t s .

Sodium f l u o r i d e -- Navara (1963) r epor ted bo th depress ion and s t i m u l a t i o n of AP of beans grown i n s o l u t i o n c u l t u r e f o r 16 days wi th 0.03 o r 0.3 ppm NaF, whi le those supp l i ed wi th 3 ppm had depressed r a t e s of AP. When P icea exce l sa Link. c u t t i n g s were watered p e r i o d i c a l l y through t h e win te r and s p r i n g wi th deionized water con ta in ing 100 ppm NaF, t h e AP r a t e s were n o t only reduced b u t n e c r o s i s was produced on t h e newly f lushed f o l i a g e . The F con- c e n t r a t i o n s i n t h e new f o l i a g e t h a t e x h i b i t e d i n j u r y contained only 3.7 t o 8 ppm when i n j u r y f i r s t occurred. By t h e end of J u l y , those need les t h a t survived conta ined from 31.5 t o 52.2 ppm F (Ke l l e r , 1980).

McLaughlin and Barnes (.I9751 exposed c u t b ranch le t s of t h r e e p ine spec ies and leaves of s i x deciduous t r e e s t o 0 , 1 .9 , 19, and 190 pprn NaF f o r 24 hours and then measured t h e r a t e s of APT With 1.9 pprn NaF, t h e r a t e s of AP of o l d e r needles of Pinus taeda --L. and P. ech ina ta Mi l l . were reduced while t h e o ther spec ies were unaffected (s-ee Table 1 f o r spec ies used). Needles with reduced r a t e s of AP contained l e s s than 10 pprn F. Although low concentrat ions of f o l i a r F reduced AP and s t imulated r e s p i r a t i o n , the authors warn of t h e l i m i t a t i o n s of ex t rapo la t ing labora- t o r y da ta t o t h e f i e l d s i t u a t i o n . However, t h e i r da ta r a i s e d s e v e r a l quest ions: (1) What concen-t r a t i o n of HF would be necessary t o inc rease t h e f o l i a r F concentrat ion 4-8 pprn i n a 24-hour per iod a s did t h e comparable dose of NaF? (2) I f upon exposure t o HF, a branch on a t r e e accumulated F a t t h e same r a t e , would t h e reduct ion i n AP be permanent o r would i t recover t o t h e pre-exposure r a t e ' a f t e r t h e exposure? (3) Would t h e 4-8 pprn inc rease i n f o l i a r F assoc ia ted with t h e reduct ion i n AP produce v i s i b l e i n j u r y ? One could view t h i s kind of exposure a s acu te , because t h e comparable dose of HF t o accumulate t h i s amount of F i n 24 hours could be 4-8 -ng m--, assuming an accumula- t i o n c o e f f i c i e n t of 1 pprn p g l m3 daym1.

Respirat ion

Resp i ra t ion (measured a s oxygen uptake) was s t imulated i n i n t a c t p l a n t s (Applegate and Adams, 1960a; Applegate and o t h e r s , 1960) o r i n t i s s u e s from i n t a c t p l a n t s fumigated with HF, i n t h e absence (Weinstein, 1961; Applegate and Adams, 1960b; Yu and M i l l e r , 1967; Mi l le r and Mi l le r , 1974) o r presence of f o l i a r l e s i o n s ( H i l l and o t h e r s , 1959). Fluoride i n h i b i t i o n of oxygen uptake has a l s o been reported and was dependent on p l a n t t i s s u e age (Bejaoui and P i l e t , 1975) dura t ion of exposure (Applegate and Adams, 1960a), n u t r i e n t s t a t u s (Applegate and Adams, 1960b), and t i s s u e F concentrat ions (Applegate and o t h e r s , 1960). However, t h e r a t e of r e s p i r a t i o n of some t i s s u e s i s r e l a t i v e l y i n s e n s i t i v e t o F ( H i l l and o t h e r s , 1959; Givan and Torrey, 1968). In t h e i r experiments with c u t b ranch le t s of p ines and hardwoods suppl ied with 1 , 9 , 19 o r 190 pprn NaF i n s o l u t i o n f o r 24 hours , McLaughlin and Barnes (1975) found t h a t t h e lower two concentrat ions genera l ly s t imulated r e s p i r a t i o n (measured a s C02 evolut ion) whi le t h e h ighes t concentrat ion both s t imulated and i n h i b i t e d r e s p i r a t i o n , depending on t h e spec ies .

Transp i ra t ion and Water Use

There a r e few r e p o r t s on t h e e f f e c t s of F on t r a n s p i r a t i o n . Navara (1963) grew beans i n s o l u t i o n c u l t u r e s containing 0.03, 0.3, and 3.0 pprn F and found reduced r a t e s of t r a n s p i r a t i o n a f t e r 12 and 16 days i n p l a n t s suppl ied with t h e two h ighes t concentrat ions of F. Soybeans fumigated wi th 12 -ng m-- HF had dramatical ly reduced r a t e s of t r a n s p i r a t i o n wi th in 4 hours (Poovaiah and Wiebe, 1973). This agrees with Navara and Kozinda (1967) who found s i m i l a r r e s u l t s i n bean

and a p r i c o t exposed t o 70 pg mV3 HF. But Thompson and o thers (1967) did not f i n d s i g n i f i c a n t d i f f e r - ences i n water use of c i t r u s exposed over a growing season t o e i t h e r ambient l e v e l s of F o r f i l t e r e d a i r wi th added F (both < 0.5 v& m-3) compared t o con t ro l p l a n t s . Amundson and o t h e r s ( i n review) exposed corn t o 1 .5 lie mF3 HF continuously f o r one week and found an increased r a t e of t r a n s p i r a -t i o n over con t ro l s . The d a t a a v a i l a b l e on F e f f e c t s on t r a n s p i r a t i o n a r e v a r i a b l e and i n s u f f i - c i e n t t o p r e d i c t poss ib le e f f e c t s on p l a n t comu-n i t y water r e l a t i o n s . However, s i n c e F can e l i c i t changes i n stomata1 a p e r t u r e , these e f f e c t s may be important i n a f o r e s t ecosystem where water d e f i c i t s l i m i t AP a t c e r t a i n times of t h e day o r year (Larcher, 1975; Kramer and Kozlowski. 1979).

p lan t ' Metabolism

F has long been used a s a metabolic i n h i b i t o r and t h e l is t of published r e p o r t s of F e f f e c t s on enzyme systems and metabolic processes i s extensive. Many of t h e e f f e c t s of F on p l a n t metabolism have been reviewed (McCune and Weinstein, 1971; Chang, 1975) and Horsman and Wellburn (1976) have com-p i l e d a use fu l l i s t of F-induced metabolic re-sponses.

Since F a l t e r s normal p l a n t metabolism, e f f o r t s have been made t o i d e n t i f y metabo l i t es t h a t could be used a s i n d i c a t o r s of i n c i p i e n t F i n j u r y . Yee-Meiler (1975) found t h a t non-specific e s t e r a s e a c t i v i t y i n young Norway spruce (Picea a b i e s [L.] Kars t . ) and European white b i r c h (Betula verrucosa Ehrh.) exposed t o a i rborne F was increased l a t e i n t h e growing season without t h e appearance of i n j u r y symptoms. Needles of c o n i f e r s placed a t varying d i s tances from an in-d u s t r i a l F source had s i g n i f i c a n t inc reases i n phenols i f they came from t r e e s with F i n j u r y (Yee-Meiler, 1977). The r e s u l t s were v a r i a b l e f o r deciduous t r e e s . Ke l le r and Schwager (1971) found increased peroxidase a c t i v i t y i n l eaves of seven t r e e spec ies exposed t o an i n d u s t r i a l source of HF and noted t h a t t h e enzyme a c t i v i t y increased before o r i n t h e absence of development of F i n j u r y symptoms. Unfortunately, many environmental s t r e s s e s and labora to ry manipulations can inc rease pei-oxidase a c t i v i t y , l i m i t i n g t h e usefulness of

t h i s assay (Endress and o t h e r s , 1980).

Mineral Nut r i t ion

Wide d i f fe rences i n t h e response of peaches t o HF l e d t o t h e f i r s t s tudy of t h e in f luence of mineral n u t r i t i o n on HF s u s c e p t i b i l i t y (Brennan and o t h e r s , 1950). With low o r d e f i c i e n t amounts of N , Ca, and P i n tomato f o l i a g e , t h e r e was re-duced uptake of NaF by r o o t s o r HF by leaves ; s i m i l a r r e s u l t s were found with excessive amounts of N and Ca (Brennan and o t h e r s , 1950). Other s t u d i e s have r e s u l t e d i n increased f o l i a r F i n P-, K-, o r Fe-deficient beans (Applegate and Adams, 1 9 6 0 ~ ) ; reduced f o l i a r F i n Mg-deficient tomato p l a n t s (MacLean and o t h e r s , 1969); smal ler f r u i t s i n Ca-deficient tomato p l a n t s (Pack, 1966); and increased to le rance t o HF exposure i n tomato p l a n t s

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Table 1. Reported e f f e c t s of f l u o r i d e (HF and NaF) on apparent pho tosyn thes i s (as measured by changes i n C02 uptake) of h i g h e r p l a n t s .

Genus o r Species Concentra t ion Duration pg m-3 HF

Gladiolus 0.8 - 8.0 7 days

Hordeum 32 4-8 hours Medicago 200 4-8 hours F r u i t t r e e s 16-40 4-8 hours

Hordeum 32 2 hours Medicago 32 2 hours

Lycopersicon 1.4 - 5.2 4 weeks 0.9 -11.2 3 weeks

F r u i t trees 2.1 av. 183 hours

Glad io lus 3.1 - 5.2 30-205 days

Gossypium 13.6 138 hours

C i t r u s .32 -.77 growing season

Glad io lus 0.8 39 days 1.2 27 days

F r a g a r i a 2.3 63 days 38 1 day

Lycopersicon 5.1112 17/21 days Prunus 1.6 42 days Zea 7.7 16 days

Sorghum 0.7 14 days 2.2 then 1.7 1212 days 3.5 then 5+ 717 days

Pinus s y l v e s t r i s ambient Nov- A p r i l -P. n i g r a n e a r -P. s t r o b u s source Lar ix l e p t o l e p i s Quercus b o r e a l i s 1 Pseudotsuga m e n z i e s i i P i c e a e x c e l s a Ainus incana -- I Sorbus A r i a Acer pseudopla tanus Lar ix decidua.

Cornus f l o r i d a 1 1.9 ppm 24 hours Liquidambar S t y r a c i f l u a NaF P lan tanus o c c i d e n t a l i s Acer rubrum I 19 PPm 24 hours Lir iodendron t u l i p i f e r a NaF O x y d e n d r s arboreurn Pinus s t r o b u s 190 ppm 24 hours -P. t a e d a -P. e c h i n a t a

P icea e x c e l s a 100 ppm winter- s p r i n g

Response Reference

p e t . r educ t ion i n AP = p e t . i n j u r y Thomas & Hendricks 1956

t o t a l i n t e r r u p t i o n i n AF' w i t h recovery i n few hours t o days

AP reduced dur ing exposure w i t h Bennett & recovery a f t e r exposure H i l l 1973

no e f f e c t H i l l & no e f f e c t o t h e r s 1959

14 p e t . r educ t ion i n AP 1 0 pe t . i n j u r y Thomas 1958

p e t . r educ t ion i n AP = p e t . l e a f i n j u r y

no e f f e c t

no e f f e c t Thompson o t h e r s 1967

no e f f e c t H i l l 1969 3 p e t . r e d u c t i o n over i n j u r y no e f f e c t 50 pe t . r educ t ion no e f f e c t no e f f e c t no e f f e c t

no e f f e c t McCune & reduced w i t h recovery a f t e r exposure o t h e r s 1976 reduced dur ing 3.5 exposure then s e v e r e l y i n j u r e d l i t t l e recovery

reduced AP of whole p l a n t due t o l o s s K e l l e r 1977 of f o l i a g e w i t h vAsible i n j u r y on remaining f o l i a g e

AP reduced i n o l d e r need les of 2. McLaughlin & t aeda and P. e c h i n a t a o t h e r s 1975

AP reduced i n a l l s p e c i e s

AP reduced i n all s p e c i e s

AP reduced i n o l d fo l i age lnew i n j u r e d K e l l e r 1980

grown with excess Mg (MacLean and others, 1976).

There is little information on the effects of F on forest tree nutrition, but there is a considerable amount of information on mineral cycling in forest ecosystems (Grier and Cole, 1972; Bormann and Likens, 1979), and airborne F can influence this cycling in forest vegetation (see "Tree Growth").

Growth and Production

Effects of F on the physiology and metabolism of plants are ultimately manifested as changes in the height, diameter, dry weight, and reproduction of the plant. But most of the available literature describes studies with agronomic crops.

Relatively low concentrations of F have been reported to stimulate growth, but growth can be inhibited by amounts of foliar F that do not produce chlorosis or necrosis in the same species (Treshow and Harner, 1968).

The effects of F on reproduction have been demonstrated and its possible implications dis-cussed by Pack and Sulzbach (1976). They hypothesized that lowered seed production was a result of inhibition of pollen germination or pollen tube growth, inhibiting or preventing, fertilization. Growth of pollen tubes in apricot (Facteau and Rowe, 1977) and sweet cherry (Facteau and others, 1973) was reduced by HF fumigation during flowering, but Dinh and others (1973) found no effect on sweet cherry pollen tube growth after exposure to 97 pg F m-3.

Joint Action with Other Pollutants

Experiments on the joint action of HF with other pollutants have emphasized effects on F accumulation (Matsushima and Brewer, 1972; Mandl and others, 1975, 1980), foliar lesions (Solberg and Adams, 1956; Hitchcock and others, 1962; Mandl and others, 1975, 1980); and growth and yield (Hatsushima and Brewer, 1972; Mandl and others, 1980). Field studies that attempt to determine the response of plants or plant connnuni- ties to F emissions must consider not only environmental and edaphic factors (Treshow and others, 1967), but also the presence of other pollutants (Bunce, 1978; McClenahen, 1978; Carlson, 1978) that complicate assessment of the impact of F alone. McCune (1980) has discussed published and unpublished results of experiments with HF in combination with S02, 03, and N02.

FIELD STUDIES

F has many characteristics that make it an ideal toxicant to study in an ecosystem. Firstly, it is an apparently non-essential element that normally occurs in foliar tissues at a concentration of <10 ppm; thus, the presence and amount of airborne contamination can be measured. Secondly, F is easily identified with specific emission

sources. Thirdly, the source strength is often known and can be applied to dispersion modelling. Fourthly, F is not very mobile in plants and tends to accumulate along the margins and distal end of the leaf. Consequently, most of the F that enters a leaf remains, except for that lost by weathering and perhaps a small amount by translocation. But, as mentioned earlier, one major drawback is the difficulty of monitoring ambient concentrations.

Smith (1974) recognized three broad classes of air pollutant-dose relationships with respect to potential impacts on forest ecosystems. The Class I relationship pertains to a very low dose where the forest acts as a sink for the pollutant and the impact may be immeasurable or stimulatory. A moderate dose relationship (Class 11) is expected to cause significant direct and indirect physiological impairment to individuals resulting in reduced growth, reproduction and/or increased morbidity. With a high dose (Class 111), there is acute morbidity resulting in ecosystem simplification with drastic changes in primary productivity, mineral cycling, succession, etc.

All three pollutant-dose relationships have been described in one form or another around F sources (Bunce, 1978; Treshow and others, 1967; Carlson and Dewey, 1971; Wheeler, 1972).

Fluoride Accumulation in Soils

The amount of total F in soils that has been reported ranges up to 8300 ppm but is generally from 20-500 ppm (Weinstein, 1979). In general, plants are poor accumulators of soil F (Hansen, 1958; MacIntire and others, 1949; Merriman and Hobbs, 1962; McClenahen, 1976), but there are some exceptions, notably species of Theaceae, such as tea and camellia (Zimmerman and others, 1957; Zimmerman and Hitchcock, 1956), hickories and flowering dogwood (McClenahen, 1976).

The deposition of fluoride in soils near sources of emission has been the subject of several in-vestigations. McClenahen (1976) examined the geographic distribution of total F in soils at two seasons and at different distances from an alumina reduction smelter. Of course, the highest accumulations occurred in the direction of the prevailing winds and extended about 10 km. In areas where F deposition was lowest, total F increased with depth of the soil profile, but the opposite was true in areas where deposition was heaviest. There was a lower concentration of F in the soil profile in outlying areas than near the source. The total F in the soil profile in low and high impact areas over the two-year study period was consistently different. No attempt was made to correlate soil F with the amount of F accumulated by plants.

Relatively large amounts of F-containing amendments are necessary to increase the accumulation of 7 in plants (Weinstein, 1977), and Israel (1974) has estimated that each 120 vg/g increment

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i n s o i l F r e s u l t e d i n a gain i n forage F of 1 ?~g/g.

The accumulation of F i n con i fe r needles and i n l'soil-humus" samples near a phosphorus p l a n t i n Canada has been s tud ied (Thompson and o t h e r s , 1979; Sidhu, 1977). Sever i ty of damage t o vegeta t ion was repor ted t o be c o r r e l a t e d with F concentra t ion of f o l i a g e and of "soil-humus". Because t h e d i s t r i - bu t ion of a i rborne F i n s o i l s would be expected t o follow t h e same p a t t e r n a s i n vege ta t ion , i t would be d i f f i c u l t t o es t imate t h e proport ion of F pres- e n t i n f o l i a g e t h a t was accumulated from t h e atmosphere and t h a t from t h e s o i l . Water-soluble F from t h e "soil-humus" was p o s i t i v e l y c o r r e l a t e d with f o l i a r F and because t h e s o i l s were highly a c i d i c , roo t uptake could have been an important pathway i n t o t h e vegeta t ion.

The s o i l a s a source of F t o p l a n t s has not been adequately inves t iga ted and t h e long-term e f f e c t of a c i d i c p r e c i p i t a t i o n i n making s o i l F a v a i l a b l e t o p l a n t s , e s p e c i a l l y i n a c i d i c , non-agr icul tural s o i l s should be inves t iga ted . There a r e many o t h e r gaps i n our understanding of t h e cycl ing of F i n f o r e s t ecosystems, such a s t h e e f f e c t s of F accumulation on l i t t e r decomposition,on changes i n n u t r i e n t a v a i l a b i l i t y , and on s o i l s t r u c t u r e .

F Accumulation and Occurrence of In ju ry

In many r e p o r t s , t h e au thors have presented values f o r t h e F content of vege ta t ion a t d i f f e r - e n t d i s t ances (and sometimes, d i r e c t i o n s ) from a source , but o f t e n they d id not provide information on t h e source s t r e n g t h , ambient a i r concentra t ion, o r t h e forms of a i rborne F t h a t were p resen t . Often, q u a l i t a t i v e o r semi-quant i ta t ive es t imates of i n j u r y a r e given and t h e r e is l i t t l e o r no con-s i d e r a t i o n t o o t h e r poss ib le causes of i n j u r y , such a s i n s e c t s , pathogens, environmental s t r e s s e s , o r even t h e presence of o t h e r p o l l u t a n t s . These da ta a r e most u s e f u l i n eva lua t ing t h e r e l a t i v e s e n s i t i v i t y of d i f f e r e n t spec ies , t h e i n t e r s p e c i f i c d i f fe rences i n s e n s i t i v i t y , t h e most s e n s i t i v e s t ages of p l a n t o r f o l i a r development, t h e compo- nen t s of t h e f o r e s t ecosystem most vulnerable t o an e f f e c t , and, i f evaluated c a r e f u l l y , t h e dose of atmospheric F o r t h e amount of t i s s u e F accumulated t o produce a measurable e f f e c t , whether i t i s r e g i s t e r e d a s a metabolic o r physiologic change o r a s a c h l o r o t i c o r n e c r o t i c l e s i o n .

As one would expect , t h e atmospheric concen- t r a t i o n of F and t h e amount accumulated i n vegeta- t i o n decreases wi th d i s t ance from t h e source (Treshow and o t h e r s , 1967; Sidhu, 1977, 1978; Thompson and o t h e r s , 1979; Roberts and o t h e r s , 1979; Bunce, 1978, 1979; Wheeler, 1972; Carlson and Dewey, 1971). The amount of F accumulated i n f o l i a g e , however, w i l l depend upon many f a c t o r s including t h e dose and form of F, t h e spec ies , a c c e s s i b i l i t y of t h e p o l l u t a n t t o t h e p l a n t (e.g. , screening of unders tory by overs tory s p e c i e s ) , plant-to-plant v a r i a b i l i t y , e t c . I n general , broadleaf spec ies w i l l accumulate more F than c o n i f e r s when they occur toge ther (Sidhu, 1977, 1978); and g r e a t d i f f e r e n c e s can occur between

con i fe r spec ies , ce te rus parabus, wi th t h e most t o l e r a n t ones accumulating t h e most F (Weinstein, 1977) . A l i k e l y explanat ion f o r t h i s is t h a t when t h e most s e n s i t i v e spec ies a r e in ju red (metaboli-c a l l y o r phys io log ica l ly ) by a given dose of F, continued absorpt ion and accumulation a r e reduced.

Not only a r e t h e most t o l e r a n t s ~ e c i e s t h e most e f f i c i e n t accumulators, bu t t h e amount of accumula- t i o n and t h e threshold f o r i n j u r y wi th in a genus (o r even spec ies ) may be v a s t l y d i f f e r e n t i n d i f f e r e n t f o r e s t ecosystems. For example, Treshow and o t h e r s (1967) did no t f i n d needle i n j u r y i n Douglas-fir (Pseudotsuga menzies i i [Mirb.] Franco) i n Idaho a t F concentra t ions i n needles t h a t averaged 150 ppm (composite va lue f o r t h e c u r r e n t year , 2-year-old, and 3-year-old need les ) , whi le Carlson and o t h e r s (1979) repor ted t h a t "mottl ing o r c h l o r o s i s was present a t 6-8 ppm" (needles of uncer ta in age) . Obviously, t h i s d i f f e r e n c e is r e f l e c t e d i n p a r t by t h e environmental d i f f e r e n c e s between t h e s tudy a r e a s (Idaho and Montana) bu t o the r d i f fe rences between t h e r e s u l t s of t h e two s t u d i e s should be considered. F i r s t l y , Carlson and o t h e r s (1979) analyzed a number of needle c h a r a c t e r i s t i c s a t d i f f e r e n t d i s t ances from t h e source of f l u o r i d e e m i s s i o n s i n Montana. The most common needle i n j u r y observed was mot t l ing (presumably c h l o r o t i c mot t l ing) and, although s i g n i f i - cant i t was a weak a s s o c i a t i o n t h a t d id not corre-l a t e very c l o s e l y wi th F content of needles . The ~2 values f o r F content of needles and needle mot t l e i n Douglas-fir, lodgepole p ine (Pinus con tor ta va r . l a t i f o l i a Engelm.) and whi te p ine (Pinus monticola Lamb.) were 0.0266, 0.0445, and 0.1604, r espec t ive ly (Carlson, 1980). But one might conclude from t h e o r i g i n a l r epor t t h a t t h e occurrence of mot t l ing on these c o n i f e r needles was increased g r e a t l y by F. The p o s s i b i l i t y t h a t o t h e r p o l l u t a n t s a ssoc ia ted with t h i s symptom, such a s ozone o r another oxidant , would be d i s t r i b u t e d i n t h e same a i r mass a s F was not considered. Carlson and o t h e r s (1979) a l s o concluded t h a t t h e r e i s no threshold content of F i n needles above which i n j u r y w i l l occur, and t h a t any d e t e c t a b l e amount of atmospheric F i s de t r imenta l t o c o n i f e r s . This is a s i m p l i s t i c explanat ion and i t ignores s e v e r a l f a c t s . The f i r s t is t h a t a l l c o n i f e r needles a r e not equal ly s e n s i t i v e t o F i n j u r y , a s i s noted i n many compilations (e .g . , Weinstein, 1977; Fluor ides , 1971; Thomas and Al the r , 1966). Secondly, s e n s i t i v i t y t o F i s r e l a t e d t o t h e age of t h e needle a t t h e time of exposure. It would be absurd t o a s s e r t t h a t "adverse e f f e c t s were v i s i b l e o n needles when t h e i r f l u o r i d e concentra t ion reached 8-10 ppm" (Carlson and o t h e r s , 1979) of t h e F accumulated a f t e r t h e c o n i f e r needles had com-p l e t e d t h e i r e longat ion. Thirdly , t h e form of F t o which needles a r e exposed and whether i t i s i n t e r n a l o r s u p e r f i c i a l would a l s o determine t h e kind of e f f e c t produced. F i n a l l y , i f t h e r e i s no threshold f o r i n j u r y then t h e r e a r e no mechanisms of d e t o x i f i c a t i o n i n p l a n t s and physiologic o r metabolic processes , such a s photosynthesis o r enzyme a c t i v i t y , t h a t have been a l t e r e d by I? should evidence no recovery. There is ample proof t h a t once a fumigation ceases , o r i f t h e periodsbetween

successive fumigations are sufficiently separated, recovery processes (repair mechanisms) are active (see Dinman, 1972; McCune and Weinstein, 1971; Thomas and Alther, 1966). Carlson and others (1979) appear to have equated injury from F with such destructive agents as ionizing radiation.

Another interesting contrast in the sensitivity of conifers to F is exemplified by the conditions near a phosphorus plant at Long Harbour, Newfound- land and an alumina reduction smelter at Kitimat, B.C. The Long Harbour area is classified as belonging to the Boreal Forest. Its productive forests are 8-12 m tall and are composed principally of dense stands of balsam fir (Abies balsamea [L.] Mill.) and black spruce (,Picea mariana [Mill.] B.S.P.). Non-productive scrub forests are less than 5 m tall and are composed of larch (Larix laricina IDuRoi] K. Koch), black spruce, and balsam fir. Rock-barrens and peat- lands are common (Thompson and others, 1979). Soils are generally shallow, precipitation is heavy, and the forests are exposed to high winds containing saline aerosols.

Kitimat is in the Pacific Coastal Rain Forest area. The forest is an uneven-aged, overmature, decadent, and stable climax forest. Logging is an important commercial activity. The forest consists of about 60% western hemlock (Tsuga heterophylla [Raf.] Sarg.), 25% balsam fir (Abies amabilis [Dougl.] Forb.), 7% western red cedar (Thuja plicata Lamb.), 6% yellow cedar (Chamaecy- paris nootkatensis [Lamb.] Spach.), and 2% sitka spruce (Picea sitchensis [Bong.] Carr.). The average age of fir and hemlock is more than 300 years, and it is not unusual to observe trees of 1 or 2 m dbh. Total annual precipitation is about 115 inches and occurs on 53% of the days. The site lies in a wide trough that runs north and south, and bisects the Coast Mountains (Reid, Collins, 1976).

Emissions at the Long Harbour phosphorus plant are not known, but are certainly lower than those at Kitimat, which have ranged from 2.5 to 6.6 tons of gaseous F/day between 1955 and 1977 (Alcan Surveillance Committee, 1979). F concentrations in conifers were frequently higher than 100 ppm in late summer without evidence of any foliar lesions. This can be contrasted to the published threshold value for needle injury in balsam fir at Long Harbour of as low as 14 ppm (Sidhu, 1978). Although the same species do not occur in the two areas, the different responses of conifers are so striking that one must conclude that (1) it is not possible to generalize from one site to another, (2) foliar F contents alone may be a poor determinant of injury, and (3) environmental stresses (such as wind, salt, nutrient, or water) are as important predictors of an effect as is F content..

It is difficult to classify conifers and other tree species into groups based upon their relative tolerance to airborne F because most compilations are based upon foliar injury, and not according to effects on timber volume, fruit production, or

other objective criteria related to the intended use of the tree.

There is insufficient information to develop these kinds of lists because existing compilations are based primarily on field and laboratory observations of foliar injury. Sensitivity lists based on foliar injury (Weinstein 1977, 1979) are only a guide iind do not provide evidence of relative effects on plant processes.

Tree Growth

Many studies have identified F as the cause of tree mortality around industrial sources (Adams and others, 1952; Scurfield, 1960; Jung, 1968; Robak, 1969). The determination of F as the causal agent usually entailed determination of foliar F concentrations and, occasionally, air quality monitoring. In these class 111 relationships (Smith, 1974), determination of the area of impact is normally easy to identify. This is not true for class I1 relationships for several reasons: (1) environmental factors (mainly weather patterns) change from year to year and not only distribute the pollutants randomly but also produce more or less favorable growing conditions for the impacted vegetation; (2) normal biotic factors (insects and pathogens) and abiotic factors (soils) also account for variability in growth; (3) stage of development of the stands of trees also dictate growth rates and the degree of competition between individuals; and (4) all of these factors combined with pollutant exposure produce a given effect. Therefore, to quantify the reduction in growth caused solely by the pollutant, the variability due to the other parameters must be accounted for.

Treshow and others (1967a) measured radial growthyneedle length, needle dry weight, and foliar fluoride concentrations in Douglas-fir (Pseudot-

menziesii [Mirb.] Franco) located at different distances from a fluoride source (also see 'F Accumulation and Occurrence of Injury"). They classified the study plots into three groups based on foliar F concentrations of composite samples o f four age-classes of needles. The groups were cpntrol (average 24 ppm F), intermediate fluoride (average 150 ppm F), and high fluoride (average 225 ppm and with some needle necrosis). Signifi-cant reductions in radial growth were found in both groups subjected to elevated F concentration There was a significant negative correlation of needle length with radial growth, but there were no significant effects on needle dry weights. Thus, they found that (1) radial growth reduction can occur without foliar lesions and (2) Douglas- fir needles can average as much as 150 ppm F without foliar injury.

A study of the impact of F on nutrient cycling in stands of loblolly (Pinus taeda L.) and slash pines (Pinus elliotti Engelm.) and the impact on tree growth was made by Wheeler (1972). No injury symptoms attributable to F exposure were noted in the sample plots but trees at the edge of some stands did show some "burning of needles".

Increased foliar F concentrations (from 13 to 49 ppm in pooled samples) were correlated with increased return rates of Ca and K from greater leaf leaching and of Ca, K, and Mg by greater litterfall. This altered nutrient cycling presumably should alter productivity but no relationship was found between needle concentrations of F, Ca, Mg, and K and productivity as measured by amount of bole wood. Wheeler (1972) concluded that either these fluctuations in needle status did not affect growth or that the sampling was insufficient to detect differences that were present.

Extensive studies on growth and F accumulation have been made at Kitimat, B.C. (Bunce, 1978) and Columbia Falls, MT (Carlson, 1978). Both areas were subjected to F for many years before any scientific assessment of growth reduction due to F were made and each area was subjected to insect infestation (see section "Insects"),

Bunce (1978) used "foliage analysis, observations of lichens, air flow patterns and topographic features" to estimate the area of impact and to establish the distribution of his sample plots. Tree ring cores were taken from western hemlock, the dominant species, from all sample locations, and were used to determine the amount of growth reduction due to F emissions. After variability in growth rates due to weather, insect infestation, and another pollutant (SO2) were accounted for, Bunce (1978) reported the annual loss of wood production to be 950 cunits (95,000 cu. ft.) per year compared to the 800,000 cunits attributed to insect damage. Obviously the cause of the insect outbreak is fundamental to the assessment of the magnitude of the F-related effects on growth and is discussed elsewhere. Although the primary and secondary (bark beetles) insect outbreaks ended by 1968, F emissions have continued at a lower rate since 1975 and trees in the insect damaged zone are regenerating satisfactorily. The question ofwhether there is a cause-and-effect relationship between F emissions and insect infestation has not yet been answered for reasons discussed elsewhere.

F from an aluminum reduction plant in Columbia Falls, MT caused growth reductions in Douglas-fir fir, lodgepole pine, and western pine (Carlson, 1978, 1979). However due to questionable assumptions and miscalculations, an overestimate of the loss of usable timber due to F pollution was made. Statistically, the data (Carlson, 1978) showed only a weak correlation between foliar F concentrations and reduced radial growth. The area of growth reduction was substantially smaller than reported previously (Carlson, 1980). It has also been stated (Carlson, 1978) that any increase in foliar F above background concentrations is detrimental to tree growth. This assumption was generated by the implied growth reduction of trees located in areas designated as having reduced growth; but upon closer examination of the data, no growth reduction could be demonstrated (Carlson, 1980). Consequently, the original

assumption, which implies that'^thereg no threshold concentration of foliar F below which injury does not occur, cannot be substantiated. This is not meant to imply that F is not phytotoxic, because it is the most toxic of the common atmospheric pollutants. But an understanding of its effects in the ecosystem, requires much research and the synthesis of an enormous amount of information. ~och's Postulates were not written frivolously.

Community Structure

Large areas of the Eastern United States are subjected to a complex mixture of air pollutants from urban centers and industrial sources. Most of the Eastern Deciduous Forests are subjected to at least moderate air pollution (Class 11). McClenahen (1978) studied the effects of a mixture of pollutants derived from industrial sources (containing F, SO?, NOx, chloride, and oxidant) on changes in structure and composition of a mixed deciduous forest in the Ohio River Valley. The study sites were arbitrarily divided into overstory, subcanopy, shrub and herb layers and the stands were measured for diversity (Pielou, 1975), evenness (Williams, 1977), and species composition.

In genera1,the average total stand densities of the overstory and herb layers were found to decrease in proximity to the F source while the subcanopy and, shrub layer increased with the shrub layer being the only layer thatshoweda significant correlation to F exposures. Chloride from another source had a greater influence in the other layers.

Murray (1979) conducted a study of plant comunity structure around an aluminum smelter in Australia. Although a number of study sites were lost by fire, he was able to ordinate species associations with F stress. More of these kinds of studies are needed to provide data to predict the risk of an effect when an ecosystem is exposed to airborne F.

Incidence and Severity of Diseases and Insects

There is evidence, from laboratory and field experiments or observations, that airborne F may alter the plant-pathogen and plant-insect relationships. The exact relationships between F and these biotic stresses and their underlying mechanisms are only beginning to be understood.

Plant pathogens -- Although there are many industrial sources of F, we are not aware of any field or laboratory reports that link airborne F with incidence or severity of forest tree diseases. It is necessary, therefore, to discuss some laboratory research on the effects of HF on diseases of crop plants in order to evaluate possible forestry effects and to establish research needs.

The plant-pollutant-pathogen interaction was reviewed by Heagle in 1973 and Laurence in 1978. For the kinds of effects that have been found, McCune and others (1973) provided three possible

explanat ions: (1) there could be a d i r e c t e f f e c t of the po l lu t an t on growth and development of the organism; (2) the po l lu tan t could a f f e c t the sus-c e p t i b i l i t y of the p l an t t o the pathogen; and (3) the po l lu tan t could a f f e c t the microbiota o r micro- environment of p l an t sur faces and thereby a f f e c t the pathogen.

Tobacco leaves in fec ted with tobacco mosaic v i ru s and containing 200-300 ppm F had a higher t i t e r of v i ru s than con t ro l leaves when a l o c a l l e s ion assay was used. The t i t e r was lower a t 500 ppm F (Dean and Treshow, 1966; Treshow and o thers , 1967b). But perhaps the be s t evidence f o r a d i r e c t e f f e c t of a irborne F on growth and development of a pathogen was t he cons is ten t reduction i n bean powdery mildew (Erysiphe polygoni DC.) found a s a r e s u l t of HF fumigation, ind ica t ing t ha t HF was a f f e c t i n g the i n f e c t i v i t y of the pathogen i t s e l f , because reduction i n d i sease was propor t iona l t o the length of the exposure period, i n f ec t i on was continuous throughout the exposure period, and the pathogen i t s e l f i s epiphytic .

The most l i k e l y mechanism f o r an e f f e c t of F on p lan t pathogenic d i seases would be an a l t e r a t i o n i n the s u s c e p t i b i l i t y of the hos t p l an t t o the pathogen. The reduct ion i n the numbers of bean r u s t (Uromyces phaseol i [Pers . ] Wint.) uredia by pre- and post-inoculation exposures t o HF may have been due t o a change i n hos t metabolism by the accumulation of F (McCune and o the r s , 1973). The bes t evidence ava i l ab l e t h a t suggests an i nd i r ec t e f f e c t of F was found i n halo-blight of bean (Pseudomonas phaseol icolus [Burkh. ] Dows. ) where stem col lapse was a f f ec t ed , but f o l i a r symptoms were not . Thus, the s i t e a f f ec t ed was s p a t i a l l y removed from the s i t e of F accumulation, the l e a f (McCune and o the r s , 1973).

There is no reason t o be l ieve t h a t crop p l an t s should respond d i f f e r e n t l y than f o r e s t spec ies t o a i rborne F and p l an t pathogens, and laboratory and f i e l d s t ud i e s a r e needed t o determine and evaluate e f f e c t s on the incidence of d i sease and poss ib le epidemiological consequences.

I n sec t s -- The cont rovers ies assoc ia ted with the e f f e c t s of F on p l a n t s i n general , and ecosystems i n p a r t i c u l a r , a l s o extend t o the poss ib i l - i t y t h a t F a l t e r s the r e l a t i onsh ip between p l an t s and des t ruc t i ve i n s e c t s , t h a t F k i l l s bene f i c i a l i n s e c t s , o r t h a t accumulation of F i n i n s e c t s makes them a vehic le f o r the t r a n s f e r of F i n ecosystems. There i s ample evidence t h a t an assoc ia t ion can e x i s t betwen F-contaminated yege ta t ion and i n sec t s , but t he r e l a t i onsh ip i s not understood and i t does not occur under a l l condi t ions o r with a l l insec ts .

P f e f f e r (1962-1963) reported t h a t a t t a c k by bark bee t l e s , snout bee t l e s , and f i r l e a f r o l l e r s were assoc ia ted with F emissions i n a f i r f o r e s t i n Czechoslovakia. Carlson and Dewey (1971) and Carlson and o the r s (1974) have reported t h a t F accumulation i n coni fe r f o l i age i s c lose ly r e l a t ed t o i n f e s t a t i o n s by severa l de s t ruc t i ve i n sec t s : pine needle s c a l e (Phenacapsia p i n i f o l i a e F i t ch ) ,

pine needle sheath miner (Ze l l a r i a haimbachi Busck), needle miner (Ocnerostyma strobivorum [Ze l l e r ] ) , and sugar pine t o r t r i x (Choristoneura lambertiana [Busck] ) t h a t ranged from no s ign i -f icance ( la rch casebearer) t o a non-significant trend (pine needle sca le ) t o s t rong evidence of a weak cor re la t ion (needle miners). Only about 6% of the va r i a t i on i n needle damage by needle miners was associated with f o l i a r F concentration. There was an even more remote assoc ia t ion between needle miner population and f o l i a r F concentration. Edmunds and Allen (1956) and Compton and o the r s (1961) found no assoc ia t ion between ~ i n e needle & a l e (Nuculopsis c a l i f o rn i ca [ ~ o l e m k ] ) and the extent of F i n ju ry o r F content of needles of - 7

ponderosa pine (Pinus ponderosa Laws) and Edmunds (1973) questioned the r e s u l t s of Carlson and Dewey (1971). Thalenhorst (1974) and Wentzel (1965) found pos i t i ve re la t ionsh ips between spruce g a l l s induced by Adelges a b i e t e s (L.) and F. But Temple (personal communication) could f i nd no co r r e l a t i on between the F content of washed s i l v e r maple f o l i - age and g a l l s induced by the bladder-gall mite (Vasates quadripes [deshimer]).

One of the most i n t e r e s t i n g examples of a possi- b l e F-plant-insect assoc ia t ion was observed near an alumina reduction smelter i n Kitimat, B.C. (see sec t ion on "F Accumulation i n P lan ts and Occurrence of Injury" and "Tree Growth"). Between 1960 and 1963, an ep izoot ic of saddleback loopers (Ectropis crepuscular ia [Denis & Sch i f f . ] ) and spruce bud- worms (Choris tmeura 9Free.) occurred t h a t k i l l e d many t r e e s over a l a rge a rea t h a t coincided wel l with the pa t t e rn o f f u m e dispersion. In 1961, balsam bark bee t l e s (Pseudohylesinus grandis [Swaine] and P. nebulosus [Lee.]) appeared a s secondary pes t s throughout the a rea at tacked by the looper and the budworm. We used the word 'poss ib le" above i n r e f e r r i n g t o F as the causa l agent i n t h i s outbreak because (1) there i s no way now t o e s t a b l i s h a cause-and-effect r e l a t i onsh ip ; (2) the emissions were a l s o high i n p a r t i c u l a t e mater ia l s , s u l f u r compounds, p i t c h v o l a t i l e s , and even CO2; (3) t he problem was no t s tudied a t t he time t h a t the outbreaks occurred; and (4) o ther poss ib le e t i o log i e s have been suggested by entomol- o g i s t s from the Canadian Forestry Service. Several of the theor ies t h a t might explain the i n sec t a t t a cks a t Kitimat a r e : (1) F absorbed by the fo l i age of the t r e e a l t e r s i t s metabolism and increases i ts a t t r ac t i venes s t o i n s e c t s ; (2) F weakens the t r e e , rendering i t l e s s ab l e t o r e s i s t i n sec t a t t a ck ; (3) gaseous o r p a r t i c u l a r emissions a r e tox ic t o p a r a s i t i c and/or predaceous i n sec t s t h a t provide important cont ro ls of the population of des t ruc t ive i n sec t s ; (4) t he emissions have a "blanket" e f f e c t t h a t r e s u l t s i n a s l i g h t tempera- t u r e a l t e r a t i o n and gives the la rvae of the loopers and budworm a competitive advantage over p a r a s i t e s and preda tors ; (5) loopers and budworm moths were ca r r i ed on winds i n t o the Kitimat a rea and dispersed i n the same pa t t e rn a s smelter emissions; and (6) there were an unusually l a rge number of l i g h t s i n the va l ley above the smelter i n the ea r ly 1960's and they provided l i g h t of wavelengths t h a t a t t r a c t e d moths (Alcan Survei l lance Committee,

Although the primary and secondary insect attacks were extremely destructive, amounting to a total net loss of mature timber estimated at 800,000 cunits (80,OOQOOO cu. ft.) (Reid, Collins, 1976) a considerable number of trees were not damaged and regrowth has been extensive. In some areas near the smelter, F-induced injury was a prominent feature on young hemlock, Sitka spruce, black cottonwood, and even western red cedar (Weinstein, unpublished field reports for 1971 and 1974 cited in Alcan Surveillance Committee, 1979). In the intervening years, especially since 1975, there has been a substantial reduction in total emissions from the smelter (more than 50% between 1975 and 1977), accompanied by greatly reduced foliar injury. Nevertheless, vegetation exhibiting no foliar symptoms often contains 100 ppm F or more, and the incidence of insect attack is no-greater than in nearby areas not exposed to the smelter emissions. Because any reduction in emissions would include gaseous F, particles, and other components of the fumes, no cause- and effect-relationship can be made. From subjective observations, however, particulate emissions have been reduced strikingly, at least since 1971, and we feel that this fraction of the emissions was perhaps of great significance in the original outbreaks. Certainly, the indirect relationship between an increase in insect colonization and particles has been known for many years (Bartlett, 1951). Even before Carlson and his colleagues were attempting to demonstrate a relationship between F and insects on U.S. Forest Service land and in Glacier National Park, an enormous outbreak of mountain pine bark beetle (Dendroctonus ponderosae [Hopkins]) was beginning on the Canadian border many km to the north. It extended throughout the entire Flathead National Forest and the western part of Glacier National Park, and has destroyed many thousands of lodgepole, ponderosa, and white pines.

Although there is little doubt that an association exists between airborne contaminants and insect outbreaks, the evidence for a cause-and- effect relationship with F in unconvincing, and at times it appears that some investigators have forced a relationship. Insect outbreaks occur in unpolluted as well as polluted areas. The question to be resolved is not whether there is or isn't a relationship between airborne substances and insects, but to determine the nature of this relationship and the features it has in common with other stresses.

Evaluation of F Injury in the Field

The most common measures of F injury to forests include (1) assessment of the presence and amount of foliar injury, especially of indicator species; (2) loss or depletion of sensitive receptors and community changes; (3) measurement of biomass production; and (4) the accumulation of F in plant tissues that might produce foliar injury or render the plant unsuitable for indigenous herbivores.

Regardless of the approaches used, the path to useful information can be a difficult and confusing one, as is well-known for other atmospheric pollutants. Some of these problems have been discussed by Weinstein and McCune (1970).

There are a number of indigenous plant species that are sensitive to atmospheric F, including goat- weed (Hypericum perforaturn L.), common barberry (Berberis vulgaris L.), Oregon grape (Mahonia repens [Lindl.] Don. and g. nervosa [Pursh.] Nutt.), blue-berry (Vaccinium spp.), and young needles of many conifers (see Table 2 for a list of F-sensitive higher plants). One general conclusion can be made: field observations of plants can be a good qualitative but is usually a poor quantitative indicator of effects.

In many cases of F pollution, there has been a severe depletion of lichen populations (reviewed by Gilbert, 1973). In areas nearest the F source, a lichen desert may exist, but they appear and increase in frequency and diversity with increasing distance from the source (LeBlanc and others, 1972). Nash (1971) and LeBlanc and others (1971) transplanted several species of lichens into the field in areas of F-emitting industries and found that the species used were injured near the source (but sometimes up to 10 km away) and were effective F accumulators. Corticolous lichens accumulate F more rapidly than saxicolous species, and consequently, demonstrate accelerated damage and reduced abundance (Perkins and others, 1980), but much research remains to characterize and classify the sensitivity of the different lichen types growing on their many kinds of habitats.

Problems associated with the measurement of biomass have been discussed in many treatises on forest mensuration, and Bunce (1978, 1979) and Parker and others (1974) have discussed the problems associated with discriminating between effects of F, insects, and environmental stresses in evaluating effects on tree growth. The relationship between F accumulation and production of foliar lesions or other effects, is discussed elsewhere, and fluorosis in indigenous herbivores is beyond the scope of this review.

F Distribution in the Environment

In its most elementary form, the transfer of F to and from the atmosphere, waters, soils and rocks, and living organisms, due to natural or anthropogenic causes, has been described (Fluoride, 1971; Weinstein, 1977). F that is accumulated in plants enters the food chain through herbivores and passes into the soil in their wastes. The transfer from one animal to another is possible in the case of insects that have accumulated F on or in their bodies and are eaten by birds or other carnivores, but this has not beenstudied. It is also not known if increased levels of F associated with a variety of insects was due to accumulation by ingestion or by surface contamination. Hughes and others (in preparation) cultured cabbage loopers (Trichoplusia ni [Hubner]) on two kinds of diets. One contained -

i n c r e a s i n g amounts of F a s NaF o r KF and equiva- l e n t amounts of c o n t r o l cabbage. The o t h e r con-ta ined F from HF-fumigated l eaves and was com-bined wi th c o n t r o l l eaves t o g ive t h e same dose curve. Analyses of prepupae and pupae showed t h a t F accumulated i n t h e bodies of t h e loopers suppl ied wi th F s a l t (G.1 0 pe t . of t h e concen-t r a t i o n of t h e d i e t on a dry weight b a s i s ) ; no F accumulated i n loopers grown with t h e fumigated cabbage d i e t . There was evidence t h a t loopers grown wi th t h e l a t t e r d i e t developed f a s t e r and grew l a r g e r than those on t h e c o n t r o l cabbage NaF o r KF d i e t s . These r e s u l t s suggest t h a t t h e F repor ted a s having accumulated i n i n s e c t s prob- a b l y was due t o s u r f a c e contamination of p a r t i c l e s (Carlson and Dewey, 1971; Dewey, 1973). Inges-t i o n of surface-contaminated i n s e c t s by ca rn ivores , however, s t i l l t r a n s f e r s t h e F t o t h e next t r o p h i c l e v e l , bu t t h e amount of accumulation t h a t might occur a t t h a t l e v e l i s no t known.

There a r e g r e a t d i f f e r e n c e s i n t h e c a p a c i t i e s of p l a n t s growing i n the same s o i l s t o accumulate F. Most p l a n t s accumulate low concen t ra t ions of F (0 - 1 0 ppm), bu t some s p e c i e s can accumulate hundreds of ppm from t h e same s o i l . I n any s p e c i e s , s o l u b l e F i n t h e s o i l s o l u t i o n can be r e a d i l y absorbed by p l a n t s (Romney and o t h e r s , 1969). When deposi ted upon p l a n t s u r f a c e s , t h e r e l a t i v e l y i n s o l u b l e forms of F have low phyto- t o x i c i t y (McCune and o t h e r s , 1977), b u t t h e i r i n g e s t i o n can be harmful t o he rb ivores . Conse-quen t ly , t h e main source of phytotoxic a i r b o r n e F i s HF.

Once i t e n t e r s a l e a f , F moves i n t h e t r a n s p i r - a t i o n s t ream t o t h e t i p s o r margins of t h e l e a f and s t a y s i n a form t h a t can be leached from many leaves (Leone and o t h e r s , 1956; Ledbet ter and o t h e r s , 1960; Jacobson and o t h e r s , 1966). Con-sequen t ly , f o l i a r concen t ra t ions of F need no t s t e a d i l y i n c r e a s e (Knabe, 1970). Twigs of deciduous s p e c i e s can accumulate F i n t h e win te r , presumably through t h e l e n t i c e l s , and e leva ted concen t ra t ions have been found i n young f o l i a g e i n t h e s p r i n g (Ke l le r , 1974, 1978). A smal l pro- p o r t i o n of F e n t e r i n g a l e a f can a l s o be t r ans -l o c a t e d t o o t h e r p a r t s of t h e p l a n t (Kronberger and o t h e r s , 1978).

F a l ready p resen t i n most s o i l s is i n an inso l -uble form and has l i t t l e i n f l u e n c e on vege ta t ion , The f a t e of F leached from f o l i a g e and of F de-p o s i t e d d i r e c t l y from t h e atmosphere has no t been s t u d i e d ex tens ive ly . Any e f f e c t w i l l depend upon t h e n a t u r e and chemistry of t h e s o i l . Fl i ih ler and o t h e r s (1979) have shown t h a t l each ing of p a r t i c u l a t e F depends upon i ts water s o l u b i l i t y (NaF > powdered p i n e need les con ta in ing F > c r y o l i t e > CaFy). The F i n powdered p ine needle l i t t e r leached n e a r l y a s r a p i d l y a s d id NaF. When NaF s o l u t i o n s were app l ied t o s o i l columns, o rgan ic mat te r , aluminum, and i r o n were l o s t , bu t t h e amount depended upon t h e s o i l type,

E f f e c t s of F on s o i l composition and s t r u c t u r e , mineral cyc l ing , and l i t t e r decomposition a r e

important a spec t s of t h e impact of F on f o r e s t ecosystems and research i n these a r e a s should have a high p r i o r i t y .

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Air Pollution-a 20th Century Allogenic Influence on Forest ~cosystems'

W i l l i a m H. smith2

Abstract: Chronic doses of ozone, s u l f u r d ioxide , nitrogen oxides, hydrogen f luor ide and other primary or secondary gaseous a i r contaminants may cause subtle effects on forest ecosystems. Air pollutants may influence reproduction, n u t r i e n t cyc l ing , photosynthes is , p r e d i s p o s i t i o n t o entomological or pathological s t r e s s or quant i ty of healthy f o l i a r t issue. Forest ecosystem response t o chronic a i r p o l l u t i o n may inc lude a l t e r a t i o n s i n growth r a t e s and successional patterns. The establishment of comprehensive f i e ld and laboratory investigations t o systematically examine chronic a i r pol lut ion s t r e s s on f o r e s t ecosystems i n those p a r t s of the world subjec t t o atmospheric contamination is concluded t o be of top priority. In the United States, forest ecosystems judged t o be a t particular risk and i n need of more intensive investigation include the Northern Hardwood fores t , C e n t r a l Hardwood f o r e s t and Western Montane f o r e s t .

The interactions between a i r contaminants t o high dose - Class I11 re la t ionship - may and f o r e s t ecosystems a r e extremely complex, induce acute morbidity or mortality of specific but can be conveniently divided i n t o - three trees. A t the ecosystem l eve l the impact of major c lasses (Smith 1980). Under conditions these various i n t e r a c t i o n s would be very of low dose - Class I re la t ionship - the va r i ab l e . I n t h e C las s I r e l a t i o n s h i p , vegetation and s o i l s of f o r e s t ecosystems pollutants would be exchanged between the atmo- function a s important sources and sinks for a i r s p h e r i c compartment, a v a i l a b l e n u t r i e n t pollutants. When exposed t o intermediate dose compartment, other s o i l compartments and - Class I1 re la t ionship - i n d i v i d u a l t r e e various elements of the biota. Depending on the species o r individual members of a given nature of the pollutant, the ecosystem impact species may be subtly and adversely affected by of this transf e r could be undetectable (inno- n u t r i e n t s t r e s s , impaired metabolism, cuous e f f ec t ) or s t imu la to ry ( f e r t i l i z i n g predisposition t o entomological or pathological effect) . I f t he e f f ec t of a i r pol lut ion dose s t r e s s , or d i r e c t disease induction. Exposure on some component of the biota is inimical then

a Class I1 re la t ionship is established. The ecosystem impact i n t h i s c a s e could include reduced productivity or biomass, alterations in

%?resented a t the Symposium on Effects of Air species composition or community s t ructure, Pollutants on Mediterranean and Temperate Forest increased insect outbreaks or microbial disease Ecosystems, June 22-27, 1980, Riverside, Cal- epidemics and increased morbidity. Under ifornia, U.S .A. conditions of high dose and Class I11 rela-

tionship, ecosystem impacts may include gross p r o f e s s o r of Forest Pathology, School of simplification, impaired energy flew and bio-

Forestry and Environmental S tud ie s , Yale geochemical cycling, changes i n hydrology and University, New Haven, Conn., U.S.A. erosion, climate alteration and major impacts

on associated ecosystems.

This paper is spec i f ica l ly concerned with Class I1 in t e r ac t i ons resu l t ing from f o r e s t ecosystem exposure t o chronic doses of ozone, su l fu r dioxide, nitrogen oxides, hydrogen fluoride or other primary or secondary gaseous a i r contaminants. It spec i f i c a l l y addresses the relationship between these gases, and their mixtures, on f o r e s t reproduc t ion , f o r e s t metabolism and direct forest s t ress as detailed by previous contr ibutors t o t h i s sect ion and attempts t o examine resulting perturbations i n ecosystem structure and function.

FOREST REPRODUCTION

Sexual reproduction of f o r e s t t r e e s is cr i t i ca l ly important for maintenance of geneticf lex ib i l i ty and the persistence of most species i n na tura l f o r e s t communities. Reproductive s t r a t eg i e s , however, a r e typ ica l ly beset by a va r i e ty of "weak points" and reproductive growth of many f o r e s t t r e e s is, a t best , irregular and qui te unpredictable. Generally there is a very good cor re la t ion between t r e e vigor and t h e capacity fo r flowering and f r u i t i n g (Kramer and Kozlowski 1979). A va r i e ty of environmental cons t r a in t s impose r e s t r i c t i o n s on t r e e reproductive processes. Because a i r contaminants may reduce t ree vigor and i n view of the f ac t that numerous potential po in t s of i n t e r ac t i on have been i den t i f i ed between a i r p o l l u t a n t s and r ep roduc t iveelements (Smith 19801, it has been hypothesized t h a t a i r con taminants may impact f o r e s t ecosystems by i n f l u e n c i n g r ep roduc t ive processes.

Considerable evidence has been presented ind ica t ing a p o t e n t i a l adve r se impact of numerous gaseous p o l l u t a n t s on p o l l e nmetabolism. Other papers have i n d i c a t e d reduced cone and f r u i t production under f i e l d conditions (Smith 1980). I f one or more of these various reproductive stress mechanisms is operat ive i n na tura l f o r e s t ecosystems, it is possible t h a t changes i n species composition may ultimately occur. In their study of ozone impact on the understory vegetation of an aspen ecosystem, Harvard and Treshow (1975) concluded t h a t only one or two years of ozone exposure might be s u f f i c i e n t t o cause s h i f t s i n community compos i t ion because of seed production responses t o ozone exposure.

FOREST METABOLISM

Photosynthesis is t h e most fundamental metabolic process of forest ecosystems and is the primary determinant of growth and biomass accumulation. The r a t e of net photosynthesis of mature t rees frequently is within the range of 10-200 mg of carbon dioxide taken up per gram of dry weight per day. The r a t e is

extremely variable, however, and influenced by genetic, c lonal and provenance differences, season of t he year, t ime of day, posi t ion within the crown of t he t ree , age of fol iage, climate and edaphic factors.

Studies with a wide variety of agricultural and herbaceous spec i e s , under control led environmental conditions, have indicated t h a t a i r contaminants must be added t o t h e list of environmental var iab les t h a t can po ten t ia l ly a l t e r the ra te of photosynthesis.

Because of e a s e of h a n d l i n g a n d experimental design, investigators studying the re la t ionsh ip between a i r po l lu tan ts and t r e e photosynthesis have pr imari ly employed t r e e seedlings for research material and controlled environmental f ac i l i t i e s for growth. Evidence h a s been p r o v i d e d , unde r t h e above circumstances, f o r photosynthetic suppression caused by su l fu r dioxide, ozone, f luor ide, heavy metals and coal dust. The thresholds of photosynthetic toxicity for tree seedlings vary w i t h i n d i v i d u a l s p e c i e s and i n d i v i d u a l p o l l u t a n t s . For s e v e r a l s e e d l i n g s t h e threshold of su l fur dioxide photosynthet' c influence may approximate 1ppm (2620 pg m o r l e s s f o r an exposure of several hours. For ozone, the threshold of photosyn9e t i c response may approximate 0.5 ppm (980 g m or l e s s fo r an exposure of several days (Smith 1980).

Cons iderab le r i s k i s associated with extrapolation of seedling photosynthetic da ta accumulated i n c o n t r o l l e d envi ronmenta l f a c i l i t i e s t o older t r e e s i n na tura l forests . Excised leaf and s m a l l chamber techniques, theref ore, have been employed t o assess the a i r pollutant influence on photosynthetic rates of t r e e s f ive-years-old and older. The use of sapling-age experimental material avoids the unique characteristics of seedling metabolism. Evidence for forest t ree sapling photosynthetic suppression has been presented f o r su l fu r dioxide, ozone and cadmium. For sulfur dioxide and ozone exposure, t h e s a p l i n g ev idence suggests t h a t t he threshold of photosynthetic reduction may approximate 0.5 t o one ppm for 5- 10 hours for one or two days (Smith 1980).

Much of the seedling and sapling evidence suggests t h a t t he photosynthetic i nh ib i t i on caused by s u l f u r d i o x i d e and ozone i s reversible i f the pollutant s t ress is removed. Under the circumstance of var iab le po l lu tan t concentration i n ambient atmospheres, photosynthetic recovery might be common. Synergism,o r g rea te r s t r e s s result ing from simultaneous pollutant exposure relative t o either pollutant alone, appears f requent ly i n t h e seedling and sapling literature. Evidence f o r synerg is t i c photosynthetic suppression by su l fur dioxide and ozone and f l uo r ide and cadmium has been presented. Almost a l l of the s t ud i e s repor t photosynthetic depression in the absence, or a t l e a s t p r io r to, t h e appearance of v i s i b l e

-3

fo l ia r symptoms.

The evidence f o r a i r pol lut ion induced photosynthetic suppression i n l a rge t r e e s i n na tura l environmentsis extremely meager and f rag i le . The seedling - sapl ing evidence however, demonstrates a threshold of e f f ec t t h a t approaches ambient concentrations i n numerous temperate environments. Because of the profound importance of the photosynthetic process and t h e po ten t ia l f o r suppression by widespread a i r contaminants, appropriate f i e ld s tud i e s must be conducted i n s p i t e of t h e i r d i f f i c u l t y and cost . The oppor tun i ty t o examine t h e impact of contaminants on resp i ra t ion and t ransp i ra t ion should a l so be included i n experimental designs. Inclusion of one or both of these physiologic processes i n seedling - sapl ing s tud i e s has revealed some i n d i c a t i o n f o r s i g n i f i c a n t a l t e r a t i o n . Increased r e sp i r a t i on coupled with reduced pho tosyn thes i s could exace rba t e growth consequences.

FOREST FOLIAGE

Under conditions of s u f f i c i e n t dose, a i r po l lu tan ts d i r e c t l y cause v i s i b l e in jury t o forest trees. The accumulation of particulatecontaminants on leaf surfaces or the continued uptake of gaseous po l lu tan ts through leaf stomata w i l l eventually r e s u l t i n c e l l and tissue damage that w i l l be manifest i n fo l ia r symptoms obvious t o t h e trained, but unaided eye. This direct induction of disease in t rees by a i r po l lu t an t s is t h e most dramatic and obvious individual t r e e response of a l l Class I1 interact ions. It is t h e only Class I1 in t e r ac t i on t h a t can be detected i n t he f i e l d by c a s u a l observa t ion . Unlike a l t e r e d reproductive strategy, nu t r i en t cycling, t r e e metabolism or insect and disease relationships; the degree of f o l i a r symptoms induced by a i r po l lu tan ts can be r e l a t i v e l y easily observed, inventoried and quantified. In the presence of s u f f i c i e n t dose, t r e e damage may be of sufficient severity t o cause mortality.

Acute f o l i a r disease may be caused i n f o r e s t v e g e t a t i o n by w i d e s p r e a d a i r contaminants i nc lud ing ; s u l f u r d iox ide , nitrogen oxides, ozone, peroxyacetyl-nitrates, f l u o r i d e and s e v e r a l t r a c e me ta l s , and localized a i r contaminants including acid rain, ammonia, chlorine, hydrocarbons and hydrogen sulfide. The response of woody plants t o these atmospheric po l lu t an t s is extremely variable and dramatically controlled by genetic factors, p l a n t age and h e a l t h and envi ronmenta l conditions. F ie ld symptoms of a i r po l lu t ion injury a r e not highly specific, are mimicked bya wide variety of other t ree s t ress factors and a r e u s e f u l on ly t o experienced observers f a m i l i a r w i t h t h e r a n g e of e d a p h i c , entomological and pathological s t ress factors c h a r a c t e r i s t i c of a given f l o r a i n a given

location. The dose required t o produce acute i n j u r y v a r i e s wide ly w i t h p o l l u t a n t and vegetative type. There has been su f f i c i en t work done t o enable a generalized ranking of r e l a t i ve f o r e s t t r e e s e n s i t i v i t y t o t h e most important a i r po l lu tan ts (Davis and Wilhour 1976). A summary treatment of general symptoms and i n j u r y t h r e s h o l d s f o r t h e gaseous contaminants inc luded i n t h i s sec t ion is contained i n Smith (1980).

FOREST ECOSYSTEM RESPONSE

The primary response of a forest ecosystem t o sustained intermediate dose and Class I1 in te rac t ion would be reduced growth and consequently reduced biomass. Reduced essential element availability, decreased photosynthesis, increased respirat ion, increased in sec t and disease s t r e s s and decreased f o l i a r t i s s u e would a l l contr ibute t o a reduction i n t r e e growth rates and ultimately t o lessened forest biomass. Alterat ions i n t h e reproductive s t r a t e g i e s of i n d i v i d u a l t r e e s p e c i e s o r d i f f e r e n t i a l response of these species t o reduced nutrition, altered metabolism and pest s t r e s s and t o d i r e c t f o l i a r in jury may cause changes i n competitive a b i l i t y and u l t imate ly lead t o a l t e r a t i o n s i n t r e e succession and species composition. Recent reviews of Class I1 vegetat ive responses t o a i r po l lu tan ts include Heck and o thers (19772, Jensen and others (1976) and Weinstein and McCune (1979).

Forest Growth

Forest growth is complex i n concept and measurement. Addition of woody tissue is the dominant f e a t u r e of f o r e s t growth. The accumulation of woody biomass (1iving weight) represents gross photosynthetic production less respiratory losses. The most fundamental characteristic of an ecosystem is its produc-t iv i ty . Forest productivity is high r e l a t i v e t o other ecos stems nd n e t product ivi ty of 1200 dry g m-' year-' f o r t r e e s and shrubs together is quite typical for temperate forests (Whittaker 1975). Productivity is s t ronglycontrolled, however, by a variety of variables i nc lud ing system age and envi ronmenta l parameters. The most important of the l a t t e r include nu t r i en t ava i l ab i l i t y , water availa- b i l i t y and temperature. Because of the variety of Class I1 i n t e r a c t i o n s i d e n t i f i e d , a i r quality also influences forest productivity i n certain environments.

P r o d u c t i v e f o r e s t s a r e c r i t i c a l l yimportant, not only f o r the obvious relat ion- s h i p between wood volume and commercial products i n managed fores t s , but a l s o fo r t h e regulat ion and maintenance of qua l i t y f o r associated ecosystems, amenity funct ions and general climatic and te r res t r ia l stability. It is disconcerting t o rea l ize , theref ore, t h a t

there is substantial and impressive evidence t o indicate that two widespread a i r contaminants, su l fu r dioxide and ozone, a r e capable of reducing f o r e s t growth. The more loca l ized release of fluoride can also reduce the amount of forest biomass (Smith 1980).

Evidence from a v a r i e t y of s t u d i e s examining f o r e s t growth i n the v i c i n i t y of l a rge point sources of su l fur dioxide has i n d i c a t e d s i g n i f i c a n t l y reduced growth. Generally the correlation of growth impact w i t h degree of f o l i a r i n j u r y caused by s u l f u r dioxide is not high. Growth retardation occurs i n t he absence of any v i s i b l e indicat ion of s t ress . Most su l fur dioxide s tud ies have accounted for precipitation influence on forest growth over t he study periods. Evidence f o r ozone suppression of f o r e s t growth has been provided by t h e comprehensive oxidant impact study of the Western Montane forest ecosystem i n California. Localized reduction of f o r e s t growth may also occur i n environments subject t o elevated levels of fluoride.

There a r e two ser ious def ic ienc ies of forest growth - a i r pollution s t ress research. The f i r s t re la tes t o the paucity of ambient a i r quality determinations i n growth studies. This makes establishment of dose thresholds or co r r e l a t i ons of dose with growth influence nearly impossible. The second serious l i m i t a -t i o n r e l a t e s t o t h e i n a b i l i t y t o p a r t i t i o n reduced growth t o t h e v a r i o u s C l a s s I1 in t e r ac t i ons t h a t may actually be responsible f o r it. For example, what percentage of reduced growth may be due t o reduced nutrition, reduced photosynthesis, increased in sec t or disease act ivi ty or increased f ol iar damage?

Future investigations of forest growth, a s impacted by a i r qua l i ty , must a l s o include better accounts of growth inÂ luencing f a c t o r s other than p rec ip i t a t i on and a i r pollutants. Bet ter awareness of addi t iona l c l ima t i c factors, impacts of insect and disease influence, and management strategies must be indicated.

Forest Succession

A s a r e s u l t of the considerable v a r i e t a l a n d s p e c i e s v a r i a t i o n i n r e l a t i v e s u s c e p t i b i l i t y t o t h e v a r i o u s C l a s s I1 interactions, it is reasonable t o suppose that d i f f e r e n t i a l t o l e r a n c e t o a i r p o l l u t i o n influence a t the species level may be reflected i n a l t e r e d pa t te rns of succession and species composition a t the ecosystem level.

Ecologists recognize two major types of processes tha t influence ecosystem succession. Autogenic processes a r e those resu l t ing from b io logica l f a c t o r s within t h e system. In f o r e s t ecosystems autogenic processes would i n c l u d e s i t e a l t e r a t i o n s caused by t h e vegetation, inf luence of one p lan t species on

another and impact of native insect or disease microorganisms. Allogenic processes, on t he other hand, are abiotic factors tha t influence s u c c e s s i o n f r o m w i t h o u t t h e sys t em. Geochemical and climatic forces a re especially important examples of a l logenic f a c t o r s t h a t inÂ luence f o r e s t ecosystems. Ideal ized ecosystem development c h a r a c t e r i s t i c a l l y i s portrayed a s an order ly change of b io log ica l p rog re s s ion occu r r ing i n a more o r l e s s constant environment (Odum 1969, Woodwell 1974). It has been general ly assumed t h a t au togen ic p roces se s dominate a l l o g e n i c processes in te r res t r ia l ecosystem succession. This general izat ion, however, is qui te incon- s i s t e n t w i t h d a t a gene ra t ed by r e c e n t imaginative s tud i e s with f o r e s t ecosystems. The importance of f i r e (an allogenic force) i n influencing pre-settlement forest ecosystems i n t h e North Central s t a t e s of t h e United S t a t e s has been subs tan t ia l (Loucks 1970, F r i s s e l l 1973, Heinselman 1973). The s ignif icance of wind s t r e s s (an a l logenic force) has been suggested t o exe r t subs t an t i a l control over successional development of forest ecosystems i n New England (Stephens 1955, 1956, Raup 1957, Henry and Swan 1974). Forest management prac t ices imposed by man, f o r example clearcutting, may simulate the influence of natural a l logenic forces on f o r e s t development and i n t e r r u p t p r o g r e s s toward a steady s t a t e c o n d i t i o n (Bormann and L i k e n s 1979) . Conversely other forest management procedures, f o r example f i r e control, may e l imina te a c o n t r o l l i n g a l l o g e n i c f o r c e and p e r m i t succession t o proceed toward an unnatural steady s t a t e condition. Class I1 s t r e s s e s imposed on forest ecosystems by a i r pollutants may be considered a 20th Century a l logenic process of po ten t ia l importance t o f o r e s t ecosystem development. As i n t h e case of clearcutting, t h i s human related force might be expected t o a l t e r t he at ta inment of steady s ta te conditions. Air pol lut ion s t r e s s would appear t o have ce r t a in unique q u a l i t i e s t h a t may make it an a l l o g e n i c i n f l u e n c e of pa r t i cu l a r importance. Length of exposure t o t h i s force precludes evolutionary adjustment and its influence, i n ce r t a in areas , may be qu i t e continuous ra ther than cyc l i c a s a r e windstorms and f i r e s . What is t h e evidence ava i lab le t o support t he importance of a i r pollution a s an allogenic force of significance in forest ecosystem development?

I n 1968 , p r i o r t o s o p h i s t i c a t e d understanding of most Class I1 in te rac t ions , Treshow (1968) provided an excellent review of t h e impact of a i r contaminants on p l a n t populations. Treshow's review, along w i t h a va r i e ty of addi t ional l a t e 1960's papers, f o r example Niklfeld (19671, ~ a j d f i k and ~ u s i 6 k a (1968) and Trautmann and o thers (19701, have indicated a l t e r a t i o n s i n successional pattern or species composition i n f o r e s t ecosystems subject t o a i r pollution exposure.

The f o r e s t s of t h e San Bernard ino

Mountains i n southern Cal i forn ia have been subject t o oxidant stress from the Los Angeles m e t r o p o l i t a n complex f o r t h i r t y years . Intensive investigations conducted i n t he San Bernardino National Forest over the years have provided valuable insight and perspective on a variety of forest a i r pollution relationships. I n 1970, Cobb and Stark concluded t h a t i f a i r pollution from the Los Angeles basin continued t o increase, there w i l l be a conversion from w e l l stocked f o r e s t s dominated by ponderosa pine Qirui Doug ex. Laws) t o poorly stocked stands of l e s s susceptible tree species i n the San Bernardino Mountains. Miller (1973) has provided a thorough discussion of this oxidant induced f o r e s t community change. Ponderosa pine is one of f ive major species of the "mixed conifer type" that covers wide areas of the western S i e r r a Nevada and t h e mountain ranges, including the San Bernardino Mountains, i n southern Cal i forn ia from 1000 t o 2000 m (3000-6000 f e e t ) elevation. Other species r e p r e s e n t e d i n c l u d e sugar p i n e (Wlamkrthu Douql.) , white f i r Wigs[Gord. & Glend.] L i n d l . ) , incense-cedar (Woce- Torr.) and Cal i forn ia b l ack oak ( Q u e r c u Newb.). The response of these f i v e major t r e e species t o oxidant a i r contaminants i n the San Bernardino National Forest has been variable. Ponderosa pine exhibits the most severe fo l ia r response t o elevated ambient ozone. A 1969 aer ia l survey conducted by t h e U.S.D.A. F o r e s t S e r v i c e indicated 1.3 mi l l ion ponderosa (or Je f f rey , Pinus jeffre i Grev. & Balf.) p i n e s on more than 405 km2 (100,000 acres) were s t ressed t o some degree. Mortal i ty of ponderosa pine has been extensive. Actual death is typ i ca l ly a t t r i b u t e d t o bark bee t l e i n f e s t a t i on of a i r po l lu t ion s t r e s s e d t r e e s . White f i r ha s suf fe red s l i g h t damage, but sca t te red t r e e s have exhibi ted severe symptoms. Sugar pine, incense cedar and black oak have exhibited only s l igh t fo l i a r damage from oxidant exposure. A 233 ha (575 acre) study block w a s delineated i n the northwest sec t ion of t h e San Bernardino Na t iona l F o r e s t i n o r d e r t o conduct an in tens ive inventory of vegetation present i n v a r i o u s s i z e c l a s s e s and t o evaluate the hea l thfu lness of t h e forest . Ponderosa pines i n the 30 can (12 inch) diameter class or larger were more numerous than any other species of comparable s ize i n the study area. These pines were most abundant on the more exposed r idge c r e s t sites of the sample area. Mortali ty of ponderosa pine ranged from 8-10 percent during 1968-1972. The loss of a dominant species i n a forest ecosystem clearly exerts profound change i n t h a t system. Miller concluded from h i s investigation that the lower two-thirds of the study a r ea w i l l probably s h i f t t o a grea te r proportion of white f i r . It was judged t h a t incense cedar w i l l probably remain secondary t o white f i r . Sugar pine was presumed t o be r e s t r i c t e d by l e s s e r competit ive a b i l i t y and dwarf m i s t l e t o e i n f e c t i o n . The r a t e of composition change w a s deemed dependent on the

r a t e of ponderosa pine mortali ty. The upper one-third of the study area, character ized a s more environmentally severe due t o climatic and edaphic s t r e s s , supports less vigorous white f i r growth. Following l o s s of ponderosa pine i n this area, sugar pine and incense cedar may assume grea te r importance. Mil ler judged, however, t h a t na tura l regeneration of t h e l a t t e r species may be r e s t r i c t e d i n t h e more barren, dry sites cha rac t e r i s t i c of t he upper ridge area. Ca l i forn ia black oak and shrub species may become more abundant i n these disturbed areas. Additional and in tens ive research on f o r e s t composition i n t h e San Bernardino National Forest has been reported (Miller 1977). Tree population dynamics were examined on 18 permanent plots established i n 1972 and 1973 and on 83 temporary p l o t s es tabl ished i n 1974 t o i nves t i ga t e f o r e s t development a s a funct ion of t i m e s ince t h e most recent f i re . Generally the da ta still support the hypothesis t h a t f o r e s t succession toward more tolerant species such as white f i r and incense cedar occurs i n t h e absence of f i r e . In t h e presence of f i r e , pine may be favored by seedbed preparation and elimination of competing spec ies . These more recent studies suggest a larger number of forest sub-types may e x i s t within the f o r e s t ecosystem than i n i t i a l l y realized.

The changes i n f o r e s t composition caused by oxidants in this southern California forest have created a management concern, a s w e l l a s ecological change, because t h e f o r e s t is intensively used as a recreational resource and the loss of ponderosa pine is judged t o reduce aesthetic qual i t ies of the forest.

Other examples, not as dramatic a s the San Bernardino example, can be found. Hayes and Skelly (1977) have monitored to t a l oxidants and associated oxidant injury t o eastern white pine i n t h r ee r u r a l Virginia sites between Apri l 1975 and March 1976. V a r i e t i e s of p i n e categorized a s s ens i t i ve and intermediate t o oxidant s t ress were judged t o be under stress. The authors speculated that susceptible eastern white pine LJ i n the Blue Ridge and Southern Appalachian Mountains may be rendered less competit ive by a i r po l lu t ion s t ress . S h i f t s i n species composition away from white pine importance along with other changes i n tree distributions may be occurring i n certain eastern regions. Brandt and Rhoades (1973) in their investigation of limestone dust impact i n deciduous f o r e s t s i n southwestern V i r g i n i a p r e d i c t e d changes i n s p e c i e s composition resu l t ing from dus t influence. Dusty s i t e s had reduced seedling and sapl ing density of red maple Q & ~ L LJ, chestnut oak (Quercw L.1

Michx. Â£.I This observation along w i t h documentation of reduced mean basal area and l a t e r a l growth of these t rees , l ed t h e a u t h o r s t o sugges t t h a t yel low-poplar. . L),more resistant t o

(-and red oak

s t r e s s caused by dust accumulation, would increase i n importance i n t h e s e hardwood stands.

Treshow and Stewart (1973) have conducted one of the few studies truly concerned with a i r p o l l u t i o n impact on an e n t i r e vegetative community. Portable fumigation chambers were p l a c e d o v e r r e p r e s e n t a t i v e p l a n t s i n intermountain grassland, oak, aspen and conifer communities. Ozone fumigations were conducted t o e s t ab l i sh injury thresholds f o r 70 common plant species indigenous t o these communities. Genera l ly i n j u r y was ev iden t a t varyjJigconcentrations above 15 pphm (294 p g m 1. Species that were found t o be most sensitive t o ozone i n t he grassland and aspen communities investigated included some dominants which were considered key t o community integri ty . The most dramatic example was aspen (mh a n u l o i d e s Michx.) i t s e l f . Single two-hour exposure t o 15 pphm ozone caused seve re symptoms on 30 percent of the foliage exposed. White f i r seedlings require aspen shade f o r optimal juvenile growth. The authors judged t h a t s ign i f i can t aspen l o s s might r e s t r i c t w h i t e f i r development and a l t e r f o r e s t succession. In a companion study, Harward and Treshow (1975) pursued t h e i r i n t e r e s t i n evaluating ozone impact on aspen communities by evaluating the growth and reproductive response of 14 understory species t o ozone. Plants were fumigated i n greenhouse chambers throughout their growing seasons. It w a s concluded from these fumigations t h a t p lan t s e n s i t i v i t i e s varied su f f i c i en t ly t o make probable major s h i f t s i n composition i n aspen communities following only a year or two of exposure t o ozone above concentrations of 7-15 (137 -294 (tg m 3 ) . The a u t h o r s observed t h a t comparable doses a re widespread in the vicinity of urban areas and t h a t widespread impacts on plant community s t a b i l i t i e s may be common i n nature. The e f f o r t s of Michael Treshow and co l l eagues h i g h l i g h t s t h e importance of examining shrub and herb s t r a t a when assessing a i r pollution impact on forest ecosystems.

McClenahen (1978) has provided a most interesting study with quantitative data on the impact of polluted a i r on the various s t ra ta of a f o r e s t ecosystem. Forest vegetation was measured i n seven stands on similar s i t e s in a 50 km area of the upper Ohio River Valley. The stands were s i t ua t ed along a gradient of polluted a i r containing elevated concentrations of chloride, su l fu r dioxide, f luor ide and perhaps other contaminants. Species richness (number of d i f f e r e n t s p e c i e s ) evenness (dominance index - low values ind ica te dominance by one or a few species) and Shannon d ive r s i t y index were typically reduced within the overstory, subcanopy and herb s t r a t a near i ndus t r i a l sources of a i r contaminants. In-creasing a i r pollutant exposure reduced canopy stem density, but abundance of vegetation i n other s t ra ta tended t o increase along the same

gradient. The r e l a t ive importance of sugar maple (AQX s a c c ~Marsh.) was grea t ty reduced in all s t ra ta with increasing pollutant. dose, while yellow buckeye ( A e s c w octandra Marsh.) appeared tolerant of poor air quality. In the shrub layer the importance of spicebush(mb e n z a 1L.I B1.1 increased wi th increasing pollutant exposure.

In southern Cal ifornia t he predominant n a t i v e shrubland v e g e t a t i o n c o n s i s t s of chaparral and coastal sage scrub. The former occupies upper e l e v a t i o n s of t h e c o a s t a l mountains, extending i n t o the North Coast ranges, ea s t t o cent ra l Arizona, and south t o Baj a California; while t he former occupies lower elevat ions on the coastal and i n t e r i o r sides of the coast ranges from San Francisco t o Baja Cal i fornia . Westman (1979) a p p l i e d standard p lan t ordination techniques t o these shrub communities t o examine the influence of a i r pollution. The reduced cover of nat ive species of coastal sage scrub documented on some s i t e s was s t a t i s t i c a l l y indicated t o be caused by elevated atmospheric oxidants. Si tes of h i g h a m b i e n t o x i d a n t s w e r e a l s o characterized by declining species richness.

Influence of a i r pol lut ion s t r e s s on succession and ecosystem species composition probably varies with the age and successional s t a t u s of t he forest . Harkov and Brennan (1979) have observed t h a t most woody p l an t s susceptible t o ozone injury are generally early succes s iona l p l a n t spec ies . Most t r e e s intermediate or t o l e ran t of ozone s t r e s s a r e typically mid- or l a t e successional types. It is not unreasonable t o propose, a s Harkov and Brennan did, t h a t l a t e successional f o r e s t communities may be the most r e s i s t a n t t o compositional change as a result of chronic a i r pollution exposure. Mature ecosystems are also typ i f ied by other cha rac t e r i s t i c s t h a t may increase the i r resis tance t o a i r pol lut ion s t r e s s . Low n e t product ion may reduce potential importance of restrictions imposed by a i r contaminants on photosynthesis. Closed and slow nutrient cycling may make nutrient capital l e s s l iable t o loss by a i r pollutant influence.

There is increasing appreciation of t he importance of a l l o g e n i c forces on f o r e s t ecosystem succession. The significance of f i r e and wind s t r e s s on f o r e s t development is subs tan t ia l i n ce r t a in environments. It is concluded t h a t a i r pol lutant impact may a l s o exert cr i t ical ly important control over forest succession and species composition. Long-term, continual s t r e s s tends t o decrease the t o t a l f o l i a r cover of vege ta t ion , decrease the s p e c i e s r i chness , and t o i n c r e a s e t h e concentration of dominance by favoring a few, tolerant species.

CONCLUSIONS

Large a r e a s of t h e t empera t e f o r e s t ecosystem a r e cur ren t ly experiencing major perturbation from a i r pollution. The influence of a v a r i e t y of a i r c o n t a m i n a n t s on biogeochemical cycling, patterns of succession and competit ion and individual t r e e health, designated Class I1 interactions (Smith 19801, a r e causing s ign i f i can t f o r e s t change i n t h e temperate zone. A t t he ecosystem l eve l t he m a j o r p e r t u r b a t i o n s i n c l u d e decreased productivity, biomass and d ivers i ty ; a t the community l eve l reduced growth; and a t t he population level a l t e r ed species composition. Ea r ly and mid-successional f o r e s t s a r e concluded t o be a t particular risk. Temperate f o r e s t s have h i s t o r i c a l l y been subjected t o major change resulting from the ac t iv i t i es of human beings. For c e n t u r i e s t h e majori n f l u e n c e was g r o s s d e s t r u c t i o n f o r a g r i c u l t u r a l , f u e l o r o the r wood-product purposes. In the present Century reduced need fo r ag r i cu l tu ra l land and increased f o r e s t management has reduced the adverse impact on f o r e s t s i n t empera t e l a t i t u d e s . Human ac t iv i t i e s of primary contemporary importance t o forest structure and function have included the in t roduc t ion of e x o t i c a r th ropod and m i c r o b i a l t r e e p e s t s i n t o f o r e s t systems l a c k i n g e v o l u t i o n a r y exposure t o t h e s e des t ruc t ive agents, enhancement of native and natural stresses by cultural practices, and the creation of a r t i f i c i a l forests of one or a few commercially important species. In the pas t several decades, however, w e have accumulated s u f f i c i e n t ev idence t o i n d i c a t e t h a t an addi t iona l major anthropogenic modifier of temperate forest ecosystem development is a i r pollution.

Research

During the l a s t decade forest researchers have outlined numerous Class I1 interactions by l a rge ly u t i l i z i n g r e l a t i v e l y young f o r e s t p l a n t s grown i n c o n t r o l l e d environment f a c i l i t i e s . During t h e next decade we must make an e f f o r t t o perform experiments i n n a t u r a l f o r e s t ecosystems t o confirm our hypotheses t h a t ambient a i r p o l l u t i o n i s reducing f o r e s t product ivi ty and a l t e r i n g species composition.

The very highest research p r i o r i t y is reserved for the establishment of comprehensive investigations t o systematically examine Class I1 interactions i n forest ecosystems located i n t h o s e p o r t i o n s of t h e t empera t e zone pa r t i cu l a r ly subjec t t o a i r po l lu t ion s t ress . These investigations should include analysis of a i r contaminant inf luence on s o i l metabolism and s t r u c t u r e f n u t r i e n t cyc l ing , t r e e reproduction, photosynthesis and respirat ion, important arthropod and microbial pathogens, f o l i a r symptoms of important vegetation i n a l l

f o r e s t s t r a t a and a carefu l examination of f o r e s t p r o d u c t i v i t y and a l t e r a t i o n s i n successional t rends and species dominance. These s tud ies w i l l be of extended term. They w i l l require the pa r t i c ipa t ion of numerous s c i e n t i f i c d i sc ip l ines , minimally including pathology, entomology meteorology, s o i l science, so i l microbiology, ecology and systems analysis. Continuous meteorological and a i r qua l i t y monitoring w i l l be required. Air po l lu tan ts measured should include su l fu r dioxide, nitrogen oxides, hydrocarbons, ozone and p a r t i c u l a t e s , t h e l a t t e r t o i n c l u d e determination of sulfates , n i t r a t e s and t r a c e metals . P r e c i p i t a t i o n a c i d i t y w i l l be routinely determined. The object ive of these comprehensive s tud ies w i l l be t o c l a r i f y and quant i fy various Class I and I1 interact ions. The ecosystems w i l l be evaluated f o r their a b i l i t y t o r e s i s t ( i n e r t i a ) and respond (resilience) t o disturbance from a i r pollution s t ress . Model development f o r t h e various i n t e r a c t i o n s w i l l hopefu l ly allow fu tu re p r o j e c t i o n s r g iven v a r i o u s a i r q u a l i t y sceneries, and allow extrapolation of findings t o other ecosystems.

In t h e United S t a t e s t h e only research program presently addressing this need is the oxidant study in progress on the San Bernardino Nat iona l F o r e s t i n Ca l i fo rn i a . I t is imperative t h a t addi t iona l inves t iga t ions be i n i t i a t e d a s soon a s possible. The s tud i e s should be established i n those areas judged t o be under the greatest stress and they should be init iated, where possible, i n association with integrated and comprehensive f o r e s t ecosystem studies currently in progress. Priority forest ecosystems i n t h e United S t a t e s include: 1) Northern Hardwood fo re s t , 2) Central Hardwood f o r e s t and 3) Western Montane f o r e s t (San Bernardino pro jec t i n progress). Appropriate locat ions, i n te rms of e x i s t i n g r e s e a r c h f a c i l i t i e s or abundant ancillary information, fo r t h e Northern f o r e s t a r e t h e Hubbard Brook Experimental Forest i n New Hampshire, the Isle Royale National Park, Michigan and the I t a sca Forest, Minnesota. I n t h e Central f o r e s t the CampBranchForestwatershed i n east-central Tennessee and the Coweeta Hydrologic Laboratory i n western North Carolina would be appropriate. With regard t o locat ion, t he Wayne National Forest i n Ohio would appear t o represent an in-teresting research opportunity. In addition t o t he San Bernardino Forest study, t h e Andrews Experimental Forest, Oregon and the Bitterroot Na t iona l Fo re s t , Idaho would be o t h e r s t r a t e g i c a l l y located sites f o r the Western Montane forest.

Policy

It is recognized that a i r pollution is one of t h e most s i g n i f i c a n t c o n t e m p o r a r y anthropogenic s t r e s s e s imposed on temperate forest ecosystems. Gradual and sub t l e change in forest m e t a b o l i s m and composition over wide

areas of the temperate zone over extended time, rather than dramatic destruction of forests i n t he immediate v i c i n i t y of point sources over shor t periods, mus t be recognized a s t he primary consequence of a i r pol lut ion stress. This realization means that forest interactions with a i r contaminants must be given con-s idera t ion i n de l ibera t ions concerning clean a i r laws and regulations, a l t e rna t ive energy s t r a t eg i e s , i ndus t r i a l and t r a n s p o r t a t i o n location and forest research funding.

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Secondary and Interactive Effects of Chronic Gaseous Pollutant Exposure of Producers, Consumers, and Decomposers

Influence of Chronic Air Pollution on Mineral Cycling in Forests1

Paul J. Zinke 2

Abstract: This paper reviews the literature concerning the impact of'chronic air pollution on mineral element cycling in forests. The concept involves the forest trees taking up essential and other elements from the soil and surrounding en-vironment eventually to return them to the soil upon mortality and decay. Chronic pollutants are considered in the context of this cycling as another form of elemental addition to the site subject to cycling in the same manner. The review is organized to assess the addition of the major elements, carbon, nitrogen, and sulfur, and the trace metallic elements. In addition, pollutant effects upon the ecosystem living components in terms of producers and decomposers are considered along with potential changes in the redox and pH state of the different portions of the forest. Some oriuinal data on foliar comnosition of Big Cone Spruce (Pseudotsuga macrocarpa (vasey) Mayr) in relation to pollution exposure, and the evaluation of a soil subject to increments o$ hydrogen in simulated acid rain leaching are presented.

I N T R O D U C T I O N The f o r e s t w i l l be cons idered t o b e t h e s tand of t r e e s and t h a t p o r t i o n of

This paper w i l l p r e sen t a review of t h e atmosphere encompassed by canopy and va r ious a s p e c t s of minera l element t runk space , and t h e p o r t i o n of t h e s o i l c y c l i n g i n f o r e s t s as a f f e c t e d by chronic encompassed by t h e r o o t space. Mineral a tmospheric p o l l u t i o n . c y c l i n g i s t h e process of c y c l i n g of e l e -

ments from t h e s o i l through uptake by r o o t s o r by f o l i a g e , t r a n s p o r t w i th in t h e t r e e s and t h e even tua l r e t u r n t o t h e f o r e s t s o i l i n t h e p roces ses of f o l i a r l each ing , r o o t exudat ion , f o l i a g e drop ,

Presented at the Symposium on Effects e t c . Return t o t h e s o i l s t o r a g e occu r s , of Air Pollutants on Mediterranean and and t h e c y c l e is cont inued by uptake Temperate Forest Ecosystems, June 22-27, aga in , o r i t may be broken by l o s s from 1980, Riverside, California, U.S.A. t h e s o i l , o r t i e u p as i n s o l u b l e p rec ip i -

t a t e s o r compounds. A i r p o l l u t i o n expo-s u r e w i l l be cons idered t o be t h e a d d i -Associate Professor of Forestry, Dep. t i o n a l a tmospheric i n p u t s which e n t e r t h eof Forestry and Resource Manage., Univer- n u t r i t i o n a l and e lementa l cyc l e ofsity of California, Berkeley, Calif. f o r e s t s due t o man made e f f e c t s on atmos-phe r i c composition.

L

ELEMENTAL CYCLIdG

The i d e a o f t h e c y c l i n g of e lements from v e g e t a t i o n t o s o i l , f o l lowing uptake from s o i l probably o u t d a t e s w r i t t e n r e c o r d s as is appa ren t from t h e p r i m i t i v e a g r i c l t u r a l p r a c t i c e of s h i f t i n g c u l t i v a - t i o n wherein a f o r e s t i s cu t and burned f o r s o i l enrichment by t h e ash. This i s fol lowed by t h e regrowth of a f a l l o w f o r e s t c rop , which i n t u r n is burned aga in . The f o r e s t vege ta t ion c y c l e s e l e - ments e s s e n t i a l f o r v e g e t a t i v e growth as w e l l as unncessary elements a c c i d e n t a l t o t h e p a r t i c u l a r environment. The 16 o r 17 e s s e n t i a l e lements ( c , d, 0, P, K , N, S, C a , Fe, Mg, Mn, Cu, Zn, Mo, B, C l , and perhaps Se) , a r e cyc led by n e c e s s i t y f o r without them t h e r e would be no f o r e s t . I n a d d i t i o n almost every o t h e r element is t r a n s l o c a t e d by p l a n t s . This concept i s used i n geochemical p rospec t ing f o r many of t h e more va luab le elements , u s i n g t h e p l a n t as a chemical prospec tor (NASA 1968). These elements which a r e cycled may be enr iched i n concen t r a t ion i n v a r i - ous p o r t i o n s of t h e c y c l e , as i n t h e f o l i a g e , t h e p l a n t d e t r i t u s on t h e ground, o r i n t h e s u r f a c e of t h e s o i l beneath t h e p l a n t s . Such enrichment i s o f t e n t h e i n d i c a t i o n of an extraneous element . S i m i l a r l y t h e inpu t of ex t rane-ous e lements i n t h e process of p o l l u t i o n may be evidenced by enrichment over t h e normal background amounts.

The s t a t e o f t h e v e g e t a t i o n and its c a p a c i t y f o r s t o r a g e of e lements w i l l determine t h e r e l a t i v e change induced by t h e a d d i t i o n of a p o l l u t a n t element. The s t a t e of t h e v e g e t a t i o n is p a r t l y de t e r -mined by t h e f a c t t h a t v e g e t a t i o n is a g i a n t r educ t ion r e a c t i o n i n which pho-t o s y n t h e s i s reduces carbon from carbon d iox ide t o carbon i n reduced carbon com-

ounds as desc r ibed by Stumm and -Morgan 71 970) . The f o r e s t t r e e s c a r r y out t h i s r e d u c t i o n r e a c t i o n , fol lowed by t h e i r dea th and t h e subsequent o x i d a t i o n of t h e carbon compounds i n t h e s o i l . The c y c l i n g of t h e elements on t h e s i t e occurs i n t h e c o n t e x t of t h i s g i a n t redox r e a c t i o n ( ~ a r r e l s , e t a l . , 1975) , and i ts s t a t e and magnitude determine t h e r a t e and amount a t which t h e o t h e r e lements w i l l be cyc l ed .

The c y c l i n g of most of t h e elements which undergo redox changes i n t h e f o r e s t n u t r i e n t c y c l e (C H 0 N S Mn ~ e )w i l l tend t o be reduced i n t h e l i v i n g vegeta ted p o r t i o n o-f t h e c y c l e and com-p l e t e t h e c y c l e t o an oxid ized form i n t h e s o i l . However, l o c a l s o i l f a c t o r s f avo r ing anaerobic c o n d i t i o n s such as water i n exces s , may cause t h e s o i l t o become a s i n k f o r some elements i n t h e reduced form, o r f o r o the r e lements i n t h e oxid ized form.

Thus p o l l u t a n t s may e n t e r t h e e l e -mental cyc l e s i n f o r e s t s and vary i n mob i l i t y depending upon t h e redox poten-t i a l at va r ious p o r t i o n s of t h e e lementa l cyc le . Some p o l l u t a n t s may a l s o b e oxi-dants i n r e l a t i o n t o t h e p o r t i o n of t h e ecosystem t h a t i s absorb ing them and thus a f f e c t t h e redox p o t e n t i a l a t t h a t po in t accord ing t o Haagen-Smit (1958) .

STORAGE POINTS AND SINKS

The soil and vegetation of the forest have several points of long term s t o r a g e of m a t e r i a l s added t o t h e elemen-ta l c y c l i n g system. It has been l ea rned from pas t f e r t i l i z a t i o n exper ience t h a t e lements added t o t h e f o r e s t , e i t h e r t o s o i l o r d i r e c t t o t r e e s , may be s t o r e d f o r vary ing pe r iods of t ime i n d i f f e r e n t p o r t i o n s of t h e f o r e s t . Obviously, t h e t r e e t runks provide s t o r a g e of t h e m a t e r i a l s conta ined i n t h e wood f o r t h e l e n g t h of l i f e of t h e t r e e and i t s subse-q.uent decomposition t ime. Deciduous por- t i o n s of t h e t r e e r e t a i n m a t e r i a l s f o r l e n g t h s of t ime p ropor t iona te t o t h e i r r e s idence t i m e on t h e t r e e ; bark f o r longer pe r iods , l e a v e s and twigs f o r l e s s e r pe r iods . The s t o r a g e t ime i n t h e decomposing o r o x i d i z i n g p o r t i o n s of t h e d e t r i t u s dropped t o t h e s o i l depends upon l o c a l environmental c o n d i t i o n s of tem-p e r a t u r e , redox s t a t e , and a v a i l a b i l i t y o r t o x i c i t y of e lements t o decomposing ( ox id i z ing ) organisms. For example, decomposition t imes f o r s u r f a c e d e t r i t u s on t h e s o i l s u r f a c e i n a f o r e s t may va ry from a f r a c t i o n of a year t o many yea r s .

The s o i l beneath t h e f o r e s t i s a g i a n t fixed-bed ion exchanger, and once elements e n t e r t h e s o i l fo l lowing r e l e a s e from s t o r a g e i n t h e v e g e t a t i v e p o r t i o n of t h e f o r e s t and i t s d e t r i t u s t h e y may be s t o r e d on t h i s exchange complex. The c a p a c i t y of t h i s i o n exchange bed as we l l as t h e n a t u r e of a s s o c i a t e d c a t i o n s w i l l determine t h e s t o r a g e p r o b a b i l i t y of e l e -ments added t o t h e f o r e s t whether as a d d i t i v e s ( p o l l u t a n t s , f e r t i l i z e r s ) , o r i n t h e normal course of mineral weather-i n g o r r a i n f a l l a d d i t i o n s . The t o t a l capac i ty of t h i s bed f o r c a t i o n exchange i n con i f e rous f o r e s t s o i l s ranges from 40 t o 300 gm e q u i v a l e n t s per meter squared t o a meter depth (Zinke , & g. , 1979). Whether t h e p o l l u t a n t added has a s i g n i -f i c a n t e f f e c t depends upon t h e n a t u r a l base l i n e composition of o t h e r c t i o n s o n t h e s o i l column ( u s u a l l y H , CaÂ¥f, Mg , K', N a ) maintained. by t h e f o r e s t and t h e l y o t r o p i c s e r i e s ( l e a c h i n g pre-cedence) of t h e s e elements . The f o r e s t s o i l a l s o has an ion exchange c a p a c i t y a l though u s u a l l y of l e s s e r amount. Thus, depending upon t h e n a t u r e of t h e pol lu-

t a n t a d d i t i v e , and whether i t a t t a i n s i o n i c form, it may be s u b j e c t t o scrub-b ing out a t t h e s o i l exchange complex s t a g e of t h e e lementa l cyc l e . This would apply t o t h e hydrogen and s u l f a t e of a c i d r a i n , o r t h e c a t i o n i c forms of some m e t a l l i c p o l l u t a n t s such as l ead o r z inc . Laboratory s imu la t ion through l each ing wi th succes s ive increments of t h e pol lu-t a n t such as a c i d r a i n can be made r e a d i l y t o determine t h i s c a p a c i t y , and an example o f t h i s fo l lows l a t e r .

The s o i l has o t h e r c a p a c i t i e s f o r s t o r a g e of a d d i t i v e s i n a d d i t i o n t o t h a t of t h e ion exchange c a p a c i t i e s . E i t h e r fo l lowing breakthrough o r s a t u r a t i o n of t h e exchange c a p a c i t y , an a d d i t i v e e l e -ment may be s t o r e d on t h e m e t a l l i c oxide complex of t h e s o i l , o r as i n s o l u b l e pre-c i p i t a t e s o r ox ides . The r e l e a s e and uptake of e lements i n t o s t o r a g e i n asso-c i a t i o n wi th t h e m e t a l l i c oxides ( u s u a l l y i r o n and manganese) w i l l depend upon t h e pH and redox p o t e n t i a l of t h e s o i l as reviewed by Jenne ( 1 968) . Reten t ion w i l l be l e a s t under t h e reducing cond i t i ons brought about by l a r g e amounts of organic mat te r and poor ly dra ined - wet condi-t i o n s .

Thus, t h e f o r e s t s o i l i s a major de te rminant i n t h e f a t e o f t h e chronic p o l l u t a n t element added t o t h e f o r e s t . The break through c a p a c i t y of t h e s o i l f o r t h e added m a t e r i a l w i l l depend upon t h e c u r r e n t i npu t of s i m i l a r e lements by t h e n a t u r a l c y c l i n g of c a t i o n s from t h e t r e e cove r , t h e i n p u t s by c u r r e n t minera l weather ing , t h e c u r r e n t a d d i t i o n s of hydrogen from r a i n f a l l and o rgan ic com-pounds produced by t h e f o r e s t , t h e deple-t i o n of b a s i c m e t a l l i c c a t i o n s taken up by t h e t r e e growth as t h e t r e e s age on t h e s i t e . The g r e a t e r t h e s t o r a g e capa- c i t y of t h e s o i l e i t h e r as i o n exchange o r m e t a l l i c ox ide (hydrous) c a p a c i t y t h e g r e a t e r t h e b u f f e r i n g c a p a c i t y of t h e f o r e s t on t h e inpu t of p o l l u t a n t s .

It w i l l be of i n t e r e s t now t o review some of t h e expe r i ence of how t h e va r ious p o l l u t a n t s behave i n r e l a t i o n t o t hese p roces ses of e lementa l c y c l e s i n a f o r e s t .

POLLUTANT ADDITIVES T O FOREST CYCLES

Any of t h e elements added t o t h e f o r e s t as p o l l u t a n t s can i n f l u e n c e e le -mental c y c l i n g , e i t h e r by a c t i n g as n u t r i e n t e lements r e q u i r e d f o r t h e growth o f t r e e s , by changing t h e redox s t a t e o f any p a r t of t h e f o r e s t , o r by changing t h e pH a t some p o i n t i n t h e system. Some o f t h i s i n t e r a c t i o n may be phys io log ica l i n t h e v e g e t a t i o n , o r i n t h e s o i l micro-

f l o r a , o r may be a mat te r of s o i l chemis- t r y . Growth r a t e s of t h e v e g e t a t i o n may be changed, t h u s a f f e c t i n g t h e r a t e s of e lementa l cyc l ing . Each p o l l u t a n t may have s e p a r a t e e f f e c t s depending upon i t s chemical and phys io log ica l n a t u r e , and t h e r e may be s y n e r g i s t i c e f f e c t s w i th combinations of a d d i t i v e s . Some of t h e major ch ron ic p o l l u t a n t s w i l l be con-s i d e r ed s e p a r a t e l y .

Carbon Compounds &i Accompanying Oxi-dan-fcs

Carbon a d d i t i o n s t o t h e f o r e s t may be important because of t h e r o l e t hey p l ay i n p l a n t growth and subsequent minera l cyc l ing . F in layson and P i t t s (1976) have r epor t ed t h a t carbon may account f o r 45$ of t h e mass of smog aero- s o l . Much of t h i s may be t h e r e s u l t o f secondary r e a c t i o n s c r e a t i n g ca rboxy l i c a c i d s , e s t e r s , carbonyl compounds, a l c o h o l s , pe rox id i c polymers, l ong cha in a lkanes and a lkenes , and f a t t y a c i d s . I n a d d i t i o n , carbon i n t h e forms of va r ious compounds is a world-wide atmospheric p o l l u t a n t due t o human a c t i v i t i e s ox id i z - i n g reduced carbon f o r energy, and t o i n d i r e c t e f f e c t s such as enhanced oxida-t i o n of s o i l o rganic mat te r due t o c l e a r -i n g f o r e s t l a n d f o r a g r i c u l t u r e . Thus carbon d iox ide as a ch ron ic p o l l u t a n t has been measured by obse rva t ions a t Mauna Loa (Hawaii) t o be r i s i n g a t t h e r a t e o f from .35 t o 1 .79 ppm per year t o a l e v e l of 325 ppm i n 1 974 (Hobbs, g &., 1974).Pe terson (1969) i n a review s t a t e d t h a t carbon d ioxide a t i t s p re sen t l e v e l i n t h e atmosphere i s s t i l l l i m i t i n g t o p l a n t growth and t h a t t h e p r o d u c t i v i t y of p l a n t s should i n c r e a s e as t h e C o n con ten t i n c r e a s e s . A r e s u l t i n g i n c r e a s e of p l a n t and f o r e s t growth of 5$ by t h e year 2000 is a ' p r e d i c t e d , and t h i s would i n c r e a s e t h e r a t e s of uptake of necessary growth elements from t h e s o i l , t h u s i n c r e a s i n g r a t e s of e lemental cyc l ing . This a l l assumes o t h e r e lements o r requi rements such as water a r e no t l i m i t i n g t o p l a n t growth. On t h e o t h e r hand, r educ t ion i n p l a n t growth may occur where t o x i c carbon compounds from p o l l u t i o n cause damage t o t r e e f o l i a g e , t h u s reducing r a t e s of mineral cyc l ing . Ozone produced as a secondary product from u l t r a v i o l e t radia-t i o n on hydrocarbons i n t h e atmosphere may reduce p l a n t growth. Evans, g &. ( 1 974) found ozone c o n t e n t s of 0.1 ppm a t t h e t o p of a smoke plume from a f o r e s t f i r e . However p l a n t s syn thes i ze methyl c h l o r i d e accord ing t o Lovelock (1 975) , and t h i s may d e s t r o y such added ozone. The ox idan t s formed from t h e o rgan ic pol- l u t a n t s in t roduced t o t h e atmosphere w i l l have adverse e f f e c t s upon va r ious amino a c i d s i n p l a n t s r e s u l t i n g i n damage

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(Haagen-Smit , 1958). F a t t y a c i d s on p l a n t s u r f a c e s may be a l t e r e d by t h e s i n g l e t oxygen r e s u l t i n g from NO2, ben-zaldehyde, and polynuclear hydrocarbons, i n c r e a s i n g s a t u r a t e d a c i d con ten t of t h e f o l i a g e accord ing t o Dowty &. (1 973) . Other o x i d a n t s such as peroxyacetyl n i t r a t e (PAN) , hydroxyl OH, hydroperoxyl HO , a l s o have similar e f f e c t s on vegeta- t i $ n . Their e f f e c t s as ox idan t s a r e def ined by t h e i r c a p a b i l i t y t o ox id i ze i o d i d e ion i n aqueous s o l u t i o n of potas-sium i o d i d e accord ing t o Kuntz, e t 9. (1 973). Also, t h e i r a c t i o n may b e s y n -e r g i s t i c , s o t h a t a l though one o r another is i n low atmospheric concen t r a t ion t h e sum of t h e ox idan t s must be considered i n e f f e c t on t h e v e g e t a t i o n . Also, t h e v o l a t i l e t e r p e n e s produced by t h e f o r e s t i t s e l f must be taken i n t o account , and accord ing t o Rasmussen (1 970) , as many as 1008 of t h e s p e c i e s i n some western coni-f e r o u s f o r e s t s may produce such v o l a t i l e hydrocarbons.

Nitrogen

Nitrogen as i t c y c l e s i n t h e f o r e s t i s i n reduced form i n t h e p l a n t and f o l -lowing m i n e r a l i z a t i o n t o ammonia i n decomposing d e t r i t u s i n t h e s o i l it is g r a d u a l l y oxid ized t o n i t r a t e where it is aga in taken up by p l a n t s t o be reduced i n va r ious n i t r o g e n compounds. Nitrogen is added as a ch ron ic a i r p o l l u t a n t as ammonium, and n i t r a t e n i t r o g e n which a l s o i s t h e end product of o x i d a t i o n of 80 by ozone. Where n i t r o g e n i s l i m i t i n g i n t h e f o r e s t as an e s s e n t i a l element t h i s should s t i m u l a t e f o r e s t growth and decom- p o s i t i o n p roces ses provided o t h e r e le -ments a r e no t l i m i t i n g . However, i f o t h e r e lements a r e l i m i t i n g t h i s would tend t o emphasize t h e o t h e r d e f i c i e n c i e s . Addi t ions as a ch ron ic p o l l u t a n t should show similar symptoms t o t hose o f t h e a d d i t i o n of n i t r o g e n as a f e r t i l i z e r . Thus f o l i a r n i t r o g e n c o n t e n t s should be h ighe r . A r e s u l t similar t o t h i s encoun-t e r e d i n Big cone spruce f o l i a g e i n t h e San Bernardino mountains i s repor ted l a t e r i n t h i s paper .

S u l f u r

t h a t The s u l f u r c y c l e i n f o r e s t s t h e s u l f u r i s i n reduced

is such form i n

a s s o c i a t i o n wi th o rgan ic compounds i n t h e p l a n t s , bu t i s oxid ized upon decomposi-t i o n i n t h e o rgan ic d e t r i t u s r e tu rned t o t h e s o i l . The decomposing s o i l micro-f l o r a conve r t t h e s u l f u r t o s u l f a t e . The degree t o which t h i s t a k e s p l ace depends upon t h e redox p o t e n t i a l of t h e s o i l . For example, i f it is ve ry low, t h e s u l f u r w i l l be r e t a i n e d i n s u l f i d e form, f r e -q u e n t l y t y i n g up heavy me ta l s .

The forms of s u l f u r added i n ch ron ic atmospheric p o l l u t i o n have been SO?, SO ", w i t h a s s o c i a t e d c a t i o n s H , NH a n t HSO as determined i n t h e p o l l u t h ~ plume trim S t . Louis Missouri by Charl-son , g 9. ( 1 973) . They found t h a t t r o p i c a l a i r masses were dominated by t h e more a c i d i c NH HSO wh i l e n o r t h e r n a i r masses were l e s s a c i d i c and dominated by (NH ) SO (1 975) . Usual ly t h e s u l f u r i n the4a?mo%-phere w i l l be oxid ized t o su l -f a t e and t h i s w i l l occur e i t h e r a s ammonium o r ca lc ium s u l h a t e d u s t accord- i ng t o daagen-Snit (1959), and s i n c e t r a p p i n g s u r f a c e s o f v e g e t a t i o n a r e aero-b i c , any reduced s u l f u r w i l l be oxid ized t o s u l f a t e i n t h e f o l i a g e .

S ince s u l f u r is an e s s e n t i a l element f o r p l a n t growth, t h e a d d i t i o n s may o r may n o t be d e l e t e r i o u s . Actual d e l e t e r i-ous e f f e c t s would occur t o t r e e s i f s u l -f u r d iox ide were t h e main a d d i t i v e . This would occur only c l o s e t o t h e emiss ion source as has happened a t Kennet t , C a l i -f o r n i a ; Copper Basin, Tennessee; and Sud- bury, Ontar io. A t g r e a t e r d i s t a n c e t h i s would be oxid ized . Presumably i f t h e p o l l u t a n t were added i n extreme amounts, t h e t i t r a b l e a c i d i t y produced would break through t h e s o i l exchange c a p a c i t y a f t e r d e p l e t i n g o t h e r c a t i o n s p r e s e n t . An example of a s imu la t ion of t h i s i s offered i n t a b l e 2 expla ined l a t e r .

Trace Elements lusts ' .

Washout, P a r t i c u l a t e s ,

Most of t h e elements o t h e r t han C , N, and S w i l l be added i n dus t and r a i n as ch ron ic p o l l u t a n t s . The p a r t i c u l a t e s i n atmospheric p o l l u t i o n c o n t a i n elements such as l e a d , sodium, magnesium, aluminium, vanadium, and z i n c i n Los Angeles t ype smog accord ing t o F in layson and P i t t s ( 1 976). Sedimentary c o r e s t aken o f f s h o r e i n t h e P a c i f i c Ocean by Bruland, e t S., (1974) , i n d i c a t e d t h a t l e a d , s i l v e r , copper , z i n c , chromium, n i c k e l , molybdenum, and c o b a l t a r e ch ron ic p o l l u t a n t s i n t h e Los Angeles a r e a . Lead, i r o n , manganese, n i c k e l , copper and z i n c were analyzed i n p r e c i p i -t a t i o n as common t r a c e element p o l l u t a n t s throughout t h e U.S. accord ing t o Lazarus e t- al . (1 970) . Beryllium is common i n i n d u s t r i a l d u s t s near sources . The amount of t r a c e element f a l l out l e s s e n s as t h e square of t h e d i s t a n c e from sources accord ing t o B e r t i n e & Goldberg (1974). Cannon and Boles (1962) found t h a t high-ways r ep re sen ted l i n e a r sou rces f o r l e a d , t h e amount i n v e g e t a t i o n dec reas ing r a p i d l y wi th d i s t a n c e from t h e source. Dedolph e t ( 1 970) found t h a t t h i s d i m u n i t i o n was loga r i thmic wi th d i s t a n c e f o r p a r t i c u l a t e l e a d . However, some e l e -ments such as cadmium, n i c k e l , l e a d , and

z i n c may b e v a p o r i z e d a t t h e s o u r c e and c a r r i e d l o n g e r d i s t a n c e s a c c o r d i n g t o Lagerwer f f & Spech t (1 970) .

The t r a c i n g o f i n p u t o f t r a c e e l e -ments i n t h e e l e m e n t a l c y c l e s i n vege ta - t i o n h a s been a t t e m p t e d by many i n v e s t i -g a t o r s . C h e s t e r and S t o n e r (1 973) used an e n r i c h m e n t f a c t o r i n which a r a t i o o f t h e e l e m e n t t o i r o n . i n t h e p a r t i c u l a t e b e i n g added i s d i v i d e d by t h e a v e r a g e r a t i o o f t h e e lement t o i r o n i n t h e e a r t h ' s c r u s t . They found t h a t t i n , l e a d , and z i n c most o f t e n were t h e e l e -ments e n r i c h e d b y p o l l u t i o n . P e i r s o n , e t -a l . (1 974) employed a n enr ichment f a c t o r i n t h e form o f t h e r a t i o o f t h e e lement t o Scandium c o n t e n t , compared t o t h e same f o r t h e l o c a l s o i l s . They found t h e s o i l s e n r i c h e d f o r V , Co, N i , Zn, A s , Se , Sb, and Pb t h i s way. S i m i l a r en r ichment r a t i o s f o r o t h e r p o l l u t a n t s shou ld iden-t i f y a u g m e n t a t i o n s o f t h e e l e m e n t s i n e l e m e n t a l c y c l e s i n f o r e s t s .

The c o n t e n t s o f p o l l u t a n t s i n t h e p l a n t s s h o u l d b e i d e n t i f i a b l e by a n o m a l i e s i n c o m p o s i t i o n . Thus, Schack-l e t t e and Connor (1 973) used t h e r e g i o n a l v a r i a t i o n of vanadium i n Span i sh moss ( ~ i l l a n d s i a ) a l o n g t h e g u l f c o a s t o f t h e U.S. t o i d e n t i f y a r e a s where c h r o n i c pol-l u t i o n by a i r b o r n e vanadium o c c u r s . Con-t e n t s as h i g h as 560ppm V were found i n c e r t a i n a r e a s , and t h e s e were assumed t o r e p r e s e n t t h e o u t p u t from o i l r e f i n e r i e s u s i n g Venezuelan c r u d e o i l which i s h i g h i n vanadium. I n s o i l - v e g e t a t i o n c y c l i n g , vanadium i s f r e q u e n t l y h e l d a t t h e s o i l -r o o t i n t e r f a c e due t o i m m o b i l i z a t i o n i n t h e o x i d i z e d s t a t e ( p e n t a v a l e n t f o r m ) . Thus, t h e redox s t a t e o f t h e s o i l -v e g e t a t i o n sys tem and i t s components i n t h e f o r e s t may d e t e r m i n e where a c h r o n i c p o l l u t i n g e lement may b e immobi l ized. E lements u n d e r g o i n g changes i n s o l u b i l i t y w i t h v a r i o u s o x i d a t i o n s t a t e s may b e immobi l ized a t v a r i o u s i n t e r f a c e s where pH o r Redox change. Chromium, vanadium, manganese, and i r o n a r e s u s c e p t i b l e t o t h i s .

Some o f t h e c h r o n i c p o l l u t a n t s added t o t h e e l e m e n t a l c y c l e o f f o r e s t s may l a t e r b e r e l e a s e d from t h e f o r e s t by v a p o r i z a t i o n . For example, C u r t i n e t a l . ( 1 974) found t h a t t i n i s t r a n s p i r e d i n v a p o r s from c o n i f e r s t o t h e amount o f 23-80 ppm i n t h e r e s i d u e o f t h e vapor . They found t h a t some c o n i f e r o u s t w i g s c o n t a i n e d up t o 6-40 ppm t i n i n t h e a s h . The t i n w a s added as a t m o s p h e r i c p o l l u -t a n t i n d u s t from i n d u s t r i a l a r e a s . How-e v e r , no ment ion w a s made o f t h i s as b e i n g d e l e t e r i o u s .

The i n p u t s o f d r y p a r t i c u l a t e m a t e r i a l s as d u s t s may b e washed o f f by r a i n . T h i s washoff may b e a major pro-c e s s of c y c l i n g o f t h e added e lement t o s o i l s . C a r l s o n --e t a l . (1 976) found t h a t a s i m u l a t e d r a i n removed 45% of a n a p p l i e d a e r o s o l o f PbC12, and t h a t l i g h t m i s t y r a i n i s most e f f e c t i v e . H e i c h e l & Hankin (1972) found t h a t t h e p a r t i c u l a t e s i n which l e a d adhered t o t r e e s averaged 7 mic romete r s i n d i a m e t e r . C h l o r i n e and Bromine were t h e main a s s o c i a t e d n e g a t i v e e l e m e n t s a s s o c i a t e d w i t h them. The assessment o f t h e i n t e n s i t y o f i n p u t o f c h r o n i c p o l l u t a n t s s u c h as t h e s e have been made by a n a l y z i n g c o n c e n t r a t i o n s on t r e e b a r k by L o t s c h e r t ( l 9 7 7 ) , and Grod-z i n s k a (1 977) . Some o f t h e s e accumula-t i o n s a r e washed down t h e t r e e t r u n k by s t em f l o w and may b e accumulated i n t h e s o i l a t t h e t r e e b a s e .

POLLUTANT INPUT I N PRECIPITATION

Washout as w e l l as i n p u t o f e l e m e n t s i n s o l u t i o n i n p r e c i p i t a t i o n is a major p a t h o f i n p u t t o t h e e l e m e n t a l c y c l i n g t h a t o c c u r s i n f o r e s t s . For example, t h e n i t r o g e n c o n t e n t s t o r e d i n a 1000 y e a r o l d redwood f o r e s t i s a b o u t t h e amount c o n t r i b u t e d by r a i n f a l l d u r i n g t h a t t i m e p e r i o d ( ~ i n k e ,5 g . , 1979) . The geo-c h e m i s t r y o f p r e c i p i t a t i o n w a s reviewed t h o r o u g h l y b y C a r r o l l (1 9 6 2 ) . She found t h a t t h e c a t i o n s which b a l a n c e t h e i o n s i n r a i n w a t e r were m o s t l y b a s i c m e t a l l i c e l e m e n t s n e a r c o a s t l i n e s o r a r i d r e g i o n s , b u t t h a t a l o n g t h e s t o r m v e c t o r from t h e s e s o u r c e s and over r e g i o n s w i t h more v e g e t a t i o n , t h e r e would t e n d t o b e a c i d i f i c a t i o n due t o l e s s d u s t o r ocean a e r o s o l s t o p r o v i d e t h e b a s i c m e t a l l i c c a t i o n s . The c o n t r o l o f wind e r o s i o n o v e r t h e G r e a t P l a i n s t h u s would t e n d t o add t o t h e a c i d f i c a t i o n o f r a i n f a l l downwind from t h e a r e a . However t h e c u r r e n t emphasis on p o l l u t i o n h a s added t h e c o n s i d e r a t i o n o f s o u r c e s o f a n i o n s i n p r e c i p i t a t i o n t h a t come from b u r n i n g f o s - s i l f u e l s . A s C a r r o l l ( 1 9 6 2 ) ment ioned, a pH below 5.7 i n d i c a t e s t h a t hydrogen is i o n i z i n g t o meet t h e n e c e s s a r y b a l a n c e w i t h a n i o n s .

The e f f e c t o f p r e c i p i t a t i o n i n p u t upon n u t r i e n t e l ement c y c l i n g i n a f o r e s t w i l l t e n d t o b e s p e c i f i c t o t h e s i t e con-d i t i o n s . T h i s would b e de te rmined by t h e f o l l o w i n g l o c a l f a c t o r s : 1. background n a t u r a l compos i t ion o f t h e s o i l s o l u t i o n . 2. t h e c a t i o n exchange c a p a c i t y o f t h e s o i l and t h e c o m p o s i t i o n o f c a t i o n s occu- py ing t h i s c a p a c i t y . 3. t h e volume o f wa te r e n t e r i n g as r a i n f a l l , 4. t h e a c i d b a s e b a l a n c e o f t h e r a i n f a l l , 5. t h e n a t u r e of t h e v e g e t a t i o n s p e c i e s w i t h

regard t o i n t e n s i t y of c y c l i n g b a s i c m e t a l l i c e lements , and perhaps o t h e r s unique t o t h e s i t e . The e f f e c t s of i npu t i n p r e c i p i t a t i o n w i l l most obvious on i n p r e c i p i t a t i o n w i l l be most obvious on sites wi th s o i l s having low exchange ma t t e r con ten t s o i l s ) and wi th s p a r s e slow growing v e g e t a t i o n ( p i n e s , sp ruces , h e a t h l a n d ) , and i n c l i m a t e s wi th l a r g e amounts o f p r e c i p i t a t i o n .

FOREST ECOSYSTEM EFFECTS

The minera l c y c l i n g i n a f o r e s t t a k e s p l a c e i n t h e c o n t e x t of an ecosys-tem of p roces ses l i n k i n g t h e va r ious l i v -i n g organisms and t h e components o f t h e environment. Chronic atmospheric pol lu-t i o n is one of t h e s e components. The e lements added w i l l be u t i l i z e d by t h e Producers i n t h e f o r e s t . These a r e t h e organisms which c a r r y out t h e r educ t ion of carbon t o carbon compounds which comprise t h e f o r e s t . This f i x e d carbon then s e r v e s as an energy source f o r t h e Decomposers i n t h e f o r e s t which a l s o have requi rements f o r t h e n u t r i e n t e lements e i t h e r i n t h e biomass of t h e producers o r fu rn i shed d i r e c t l y by t h e s o i l . Thus p o l l u t a n t e lements w i l l i n t e r a c t i n t h e c y c l e between Producers and Decomposers, w i th s t o r a g e of e lements and p o s s i b l e s i n k s of u n a v a i l a b l e m a t e r i a l accumulat- i n g i n t h e s o i l p o r t i o n of t h e c y c l e .

E f f e c t s -of Chronic P o l l u t i o n on Producers

These e f f e c t s can range from enhancement of p r o d u c t i v i t y t o a marked decrease depending upon whether t h e addi-

. t i v e is an e l e m e n t c u r r e n t l y l i m i t i n g growth o r is a t o x i c element. I f t o x i c , t h e e f f e c t s w i l l show up i n f o l i a r dam-age , o r i n t e r f e r e n c e wi th va r ious physio-l o g i c a l p roces ses . The syposium proceed- i n g s e d i t e d by Naegele (1973) con ta ins many d e s c r i p t i o n s of t h e s e t o x i c e f f e c t s . Mc Cune i n t h i s p u b l i c a t i o n f e l t t h a t such t o x i c e f f e c t s should be s p e c i f i c w i th regard t o t h e Receptor ( l e a f , t r e e , f o r e s t ) , t h e P o l l u t a n t , t h e Event , and t h e Environment. Acute e f f e c t s a r e r e l a -t i v e l y easy t o de te rmine , as i n t h e dea th of l e a v e s near a sme l t e r r e l e a s i n g SO2. Obviously t h i s would decrease t h e r a t e of e lementa l c y c l i n g a t t h e s i t e a long wi th a b r i e f s u r g e of added m a t e r i a l s t o t h e s o i l as t h e d e f o l i a t i o n took p l a c e and l eaves dropped t o t h e s o i l t o be decom-posed. Whether t h i s is a l o s s t o t h e s i t e depends upon t h e c a p a c i t y o f t h e unde r ly ing s o i l as d i scussed i n r e l a t i o n t o d e f o l i a t i o n by h e r b i c i d e s by Zinke (1974) . The e f f e c t s a r e more d i f f i c u l t t o a s s e s s i n t h e case o f ch ron ic low l e v e l p o l l u t i o n as d iscussed by 'Feder (1 973) . The changes i n p r o d u c t i v i t y

would need t o be s t a t i s t i c a l l y s i g n i f i -cant be fo re and a f t e r t h e i n i t i a t i o n of t h e p o l l u t i o n . Mi l l e r (1 973) has made an approach t o i n d i c e s of l e v e l of ch ron ic p o l l u t i o n i n terms of v i s u a l c h a r a c t e r i s -t i c s on t h e t r e e s ; need le r e t e n t i o n , nee-d l e l e n g t h , needle c h l o r o s i s , branch dea th i n t h e case of ponderosa p ine . Fol iage composition should i n d i c a t e such i n p u t s , and a paper by Arkley and Glauser i n t h i s symposium covers t h i s . Also an example i n t h e case of Big Cone Spruce f o l i a g e is presented i n t a b l e 1 . McBride, e t al . (1975) made measurements of a c t u a l g r o w t h r a t e r e t a r d a t i o n o f 26% f o r he ight and volume growth of ponderosa

In1974) found a g r i c u l t u r a l p l a n t s , White a decrease i n C02 uptake due

t o s y n e r g i s t i c e f f e c t s of NO + SO2 when each were p re sen t a t l e v e f s n o t con-s ide red i n h i b i t i n g t o growth. S t imu la t ion of primary producers by p o l l u t i o n is no t o f t e n r e p o r t e d due t o t h e nega t ive conno-t a t i o n of t h e t e r m . However, Schnappinger (1975) found an i n c r e a s e i n growth due t o response t o z i n c conta ined i n f l y ash .

There a r e numerous v a r i a b l e s which may a f f e c t t h e i n t e n s i t y w i th which a given l e v e l of p o l l u t a n t w i l l a f f e c t t h e producers i n an ecosystem. Thus t h e t r a p p i n g e f f i c i e n c y of t h e f o l i a g e sur -f a c e is d i f f e r e n t f o r va r ious s p e c i e s as d iscussed by Zinke (1966) , t h e v e l o c i t y of t h e a i r pas t t h e t r a p p i n g s u r f a c e as h a s been eva lua ted by Hori (1 953) and S l i n n ( 1 976). Following t r a p p i n g t h e m a t e r i a l may not be absorbed by t h e sur-f a c e as found by Motto (1970) . This is p a r t i a l l y a t t r i b u t a b l e t o t h e p a r t i c l e s i z e accord ing t o Natusch & Wallace (1974) . There may be s y n e r g i s t i c e f f e c t s a t t h e f o l i a g e s u r f a c e . iiovelock (1974) has a l l uded t o t h e p o s s i b l e c r e a t i o n of PAN on f o l i a g e s u r f a c e by t h e combination of 0 and hydrocarbons ing l i n e n .

Once absorbed by p o l l u t i n g element w i l l t a l c y c l e on t h e s i t e . from t h e p l a n t may be

as occurs on dry-

t h e producer t h e e n t e r t h e elemen-

The d i s p o s i t i o n n o t on ly through

l e a f drop , but may be by d i r e c t r o o t exu-d a t i o n as Olson e t a1 (1 962) found wi th a d d i t i o n s of r a d i o a c t i v e Cesium added t o a t r e e t runk . However upon be ing dropped t o t h e s o i l as d e t r i t u s o r e n t e r i n g i n o t h e r ways, t h e p o l l u t i n g element w i l l t hen be a f f e c t i n g t h e decomposers i n t h e f o r e s t .

E f f e c t s of- Chronic P o l l u t i o n on Decom-nosers

The e f f e c t s upon decomposers, t h e s o i l mic ro f lo ra and f auna t h a t complete

t h e e lementa l c y c l e s i n t h e s o i l , w i l l be v a r i a b l e . A s w i th t h e producers which f i x carbon d i o x i d e , t h e a d d i t i v e s t o t h e s i t e th rough a i r p o l l u t i o n may i n c r e a s e o r decrease t h e i r a c t i v i t i e s . These organisms r e q u i r e t h e same n u t r i e n t e l e -ments as t h e producers as w e l l as t h e a d d i t i o n a l ones of sodium, i o d i n e , and vanadium f o r t h e s o i l fauna. If t h e pol-l u t a n t s a r e added i n t o x i c q u a n t i t i e s t h e y would presumably r e t a r d t h e decompo-s i t i o n of organic ma t t e r i n t h e s o i l and thus slow o r b lock e lementa l c c l i n g .They may be s u b l e t h a l o r even mutagenic t o t h e s e organisms accord ing t o S to t zky 1 9 7 4 ) .

The d e t r i t u s o r l i t t e r l a y e r on t h e f o r e s t f l o o r is t h e f i r s t major a r e a of a c t i v i t o f t h e decomposers. Wittkamp & Frank (1969) found t h a t l i t t e r samples impregnated w i t h in t roduced elements such as Cobal t 60 and Cesium 137 had loga-r i t h m i c r e l a t i o n s h i p wi th t ime i n t h e f r a c t i o n remaining, and t h a t l o s s c o e f f i - c i e n t s were d i f f e r e n t f o r d i f f e r e n t e l e -ments. These v a r i e d w i t h t h e s p e c i e s of t r e e y i e l d i n g t h e d e t r i t u s . The s t o r a g e per iod of t h e a d d i t i v e element depended upon r e l a t i v e chemical m o b i l i t y of t h e element , composi t ion of o the r e lements p r e s e n t , and t h e mois ture and tempera ture c o n d i t i o n s o f t h e s i t e .

If a p o l l u t a n t i s an element which i s l i m i t i n g r a t e of decompostion, t h e e f f e c t on t h e decomposers may be posi-t i v e . For example l e a f l i t t e r wi th t o o h igh a ~ a r b o n / ~ i t r o g e nr a t i o ( n i t r o g e n l i m i t i n g ) decomposes ve ry s lowly . Adding n i t r o g e n as a ch ron ic p o l l u t a n t would a c c e l e r a t e t h i s decomposition and r e l e a s e s t o r e d elements more r a p i d l y .

The s o i l f a u n a s e r v e a major t a s k i n e lementa l c y c l i n g i n a f o r e s t ecosystem by p h y s i c a l l y decomposing organic d e t r i t u s , reducing i t i n s i z e and i n c r e a s i n g s u r f a c e a r e a t o b r i n g about f a s t e r r a t e s of funga l and b a c t e r i a l decomposition. Earthworms of va r ious s p e c i e s were found by Gish & Chris tensen (1973) t o accumulate t r a c e elements from p a r t i c u l a t e p o l l u t i o n i n o rde r of i n c r e a s i n g atomic weight : N i < Zn < Cd < Pb. The s o i l f auna may s e r v e as a l i n k f o r t r a n s f e r of n u t r i e n t e lements t o v a r i o u s p r e d a t o r s i n t h e f o r e s t ecosys-tem.

S to t zky ( 1 974) c h a r a c t e r i z e s t h e s o i l as bo th an a b i o t i c as w e l l as b i o t i c s i n k f o r p o l l u t a n t s . Ethylene and C O a r e degraded by s o i l micro organisms. Fungi i n s o i l metabol ize v o l a t i l e s from p l a n t f o l i a g e such as e thane , b u t a n e , , e t c . Thus s o i l by v i r t u e o f t h e v a r i o u s organ- i s m s p r e s e n t has a s t r o n g c a p a b i l i t y t o

d e t o x i f y p o l l u t a n t s . A t low concentra-t i o n s p o l l u t a n t s may b r i n g about an enrichment o f t h e micro organisms which can u t i l i z e them.

The u l t i m a t e r o l e of t h e decomposers i s t h u s t o c y c l e elements from t h e vege-t a t i o n t o t h e s o i l , u s u a l l y o x i d i z i n g them as energy s o u r c e s , and u l t i m a t e l y r e l e a s i n g them t o t h e chemical and physi-c a l p roces ses of t h e s o i l o r renewed uptake by t h e r o o t s of t h e producers .

Chronic P o l l u t a n t s i n t o S o i l

The f i n a l f a t e of a d d i t i v e s t o t h e ecosystem may be t o remain i n t h e s o i l i n i n s o l u b l e form. Thus once processed by t h e decomposers t h e elements may become minera l p r e c i p i t a t e s which may a c t as s i n k s (Nat . Res. Council 1977) . Thus f l u o r i n e added through p o l l u t i o n may be p r e c i p i t a t e d i n t h e s o i l a s i n s o l u b l e CaF2. Page and Ganje (1970) showed t h a t t he t o p 2.5 cm. of s o i l w a s most a c t i v e i n t r a p p i n g l e a d e n t e r i n g t h e s o i l -v e g e t a t i o n system i n sou the rn C a l i f o r n i a . S o i l s sampled i n 1967 were compared wi th previous samples obta ined i n 191 9. An average inc rease of 15-36 ppm l e a d accounted f o r 1/5 of t h e l e a d contained i n t h e 47 b i l l i o n g a l l o n s of g a s o l i n e which had been burned du r ing t h e per iod encompassed. Keaton ( 1937) added l a r g e amounts of l ead n i t r a t e t o s o i l (2784 ppm) and found t h a t very l i t t l e ( 1 7 ppm) remained i n s o l u b l e form. Lee & Tallis (1973) found it p o s s i b l e t o d a t e p e r i o d s of l e a d p o l l u t i o n i n a p e a t bog i n Grea t B r i t a i n , f i n d i n g a peak i n 500 A.D. w i t h t h e o p e r a t i o n of Roman l e a d mines, and a subsequent i n d u s t r i a l peak beginning about 1460 AD. S imi l a r b u t r e c e n t h i s -t o r i c a l evidence of l e a d c o l l e c t i o n i n ecosystem s i n k s w a s found i n wood con ten t of l ead dated by annual r i n g s by Sheppard & Funk (1975) .

S o i l o rganic mat te r g e n e r a l l y enhances t h e r o l e of s o i l as a s i n k f o r added t r a c e elements . Purr e t a1 (1971) have noted t h a t pH w i l l determine whether s o i l i s a sou rce o r s i n k . Thus, a t neu-t r a l t o s l i g h t l y a l k a l i n e pH; A s , B, Cd, Go, Cu, F, Fe, Pb, Mn, N i , Sn, and Zn w i l l tend t o be immobilized, bu t Ca, Cr, K Mg, Mo, Rb, Se, and Sr may become more a v a i l a b l e t o p l a n t s . Thus anyth ing caus-i n g a change i n s o i l pH may r e l e a s e pre-vious p o l l u t a n t s t h a t had t empora r i l y become t rapped i n t h e s o i l as a s i n k . Various p r e c i p i t a t e s such as s o i l car-bonates may form, a l s o depending upon pH.

The s o i l i on exchange c a p a c i t y w i l l r e t a i n elements i n a form ready t o be

Table 1: Big cone sp ruce f o l i a g e a n a l y s e s a c r o s s g r a d i e n t s o f dec reas ing ch ron ic p o l l u t i o n i n t e n s i t y .

WESTERN SAN GABRIEL MTNS. Angeles Nat ional F o r e s t Location Weldon Canyon Woodwardia Canyon Cloudburst Can yon T i e Canyon Summit NITROGEN

p e r c e n t 1.80 r ank 93

PHOSPHORUS PPm 601 r ank 7

N /P r a t i o 20.2 r ank 92

EASTERN SAN GABRIEL MTNS. Angeles Nat ional F o r e s t Locat ion Lower San Antonio Camp Baldy Snowcrest Camp Big P i n e s NITROGEN

p e t . rank

PHOSPHORUS Ppm 1093 rank 25

N /P r a t i o r ank

SAN BERNARDINO-SAN JACINTO MTNS. San Bernardino N.F. - Cleveland N.F. Locat ion Lower Waterman Upper Waterman C r e s t l i n e Camp Angeles Keene Palomar

(young) ( o l d ) (young) ( o l d ) NITROGEN

p o t . 2.12 1.80 2.02 2.04 1.22 .99 1.06 1.13 rank 97 92 96 96 52 13 26 38

PHOSPHORUS PPm 648 838 1016 1685 1658 1552 1544 1580 r ank 1 7 18 . 81 79 70 69 72

N /P r a t i o 32.7 21.4 19.8 12.2 7.3 6.4 6.8 7.1 rank 9 9 94 92 70 36 26 3 1 34

CHRONIC POLLUTION HEAVIEST HEAVY MODERATE-LIGHT LOW NIL INTENSITY

Table 2: S imula t ion of a c i d r a i n f a l l a d d i t i o n by l each ing a sur-f a c e s o i l developed under t h e i n f luence of a mature pon- de rosa p ine a t t h e a r i d l i m i t o f t h e occur rence of t h e s p e c i e s . ( i n m i l l i e q u i v a l e n t s per 100 m s . f i n e e a r t h p o r t i o n ex-c e p t last column as i n d i c a t e d )

Exchangeable Cat ions S o i l Treatment Exchange Remaining on S o i l

Capac i ty %

Leached s o i l s :

Leachate Composition- 3 I 500 m l H20

+5.71 meq. H+

+11 .40 meq. H+

+17.09 meq. H+

+22.9 meq. H+

1' Fine e a r t h p o r t i o n , 0-2.5 i nch sampling hor izon .

D i f f e r ence between t h e sum ( ~ a " + M ~ + + + K' + ~ a ' ) and t h e Exchange Capaci ty .

^-IThe H' w a s added as 0.1N H C 1 t o the.500 m l of d i s t i l l e d wa te r , s i n c e 1 m l of 0.1N H C 1 = 0.1 meq. H .

recyc led back t o t h e l i v i n g organisms on t h e s i t e , and a l s o keep them from leach- i n g away from t h e s i t e . Depending upon t h i s c a p a c i t y , e lements added through ch ron ic p o l l u t i o n may be r e t a i n e d i n t h e e l emen ta l c y c l e of a f o r e s t provided t h e y a r e n o t t rapped i n a s i n k o r l eached away.

FOLIAGE ANALYSES I N D I C A T I N G FOLLrnION

The e f f e c t o f ch ron ic air p o l l u t i o n of t h e t ype t y p i c a l of t h e Los Angeles -San Bernardino b a s i n on f o l i a r ana lyses of t h e Cone Spruce (Pseudotsuga macrocarpaBi. Vasey) Mayr) w a s determined. Samples o f t h e f o l i a g e were ga thered throughout t h e range of t h e s p e c i e s , and a l s o on g r a d i e n t s o f e l e v a t i o n o r d i s -t a n c e from t h e a r e a s t y p i f i e d by "smog" t o a r e a s r e l a t i v e l y f r e e o f "smog". Ana-l y s e s were made of 9 major e lements i n t h e v a r i o u s age c l a s s e s of t h e f o l i a g e . The e lements most obvious ly r e l a t e d t o t h e i n t e n s i t y o f t h e smog and t h e i r rat-i n g i n a cumula t ive p r o b a b i l i t y d i s t r i b u -

t i o n from lowest t o h ighes t va lue a r e shown i n t a b l e 1.

Nitrogen con ten t of t h e f o l i a g e and t h e r a t i o of n i t r o g e n t o phosphorus con-t e n t were t h e most obvious i n d i c a t o r s of t h e e f f e c t o f ch ron ic air p o l l u t i o n o f t h e Los Angeles t ype . Where t h e r e w a s ambigui ty i n t h e n i t r o g e n v a l u e s as i n San Antonio Canyon, t h e n i t r o g e n t o phos-phorus r a t i o was t h e b e s t i n d i c a t o r i n t h i s s p e c i e s .

SIMULATED A C I D RAINFALL LEACHING

A l a b o r a t o r y experiment w a s con-ducted i n which samples o f a n e a r l y c a t i o n s a t u r a t e d s o i l under t h e i n f l u e n c e of ponderosa p ine were leached wi th so lu- t i o n s c o n t a i n i n g s u c c e s s i v e increments of H The s o i l samples were ob ta ined a t t h e lower r a i n f a l l l i m i t o f ponderosa p ine where t h e s o i l was most l i k e l y t o be base s a t u r a t e d . F ive s e p e r a t e t e n gram samples of t h i s s o i l were leached by s o l u t i o n s which were r e s p e c t i v e l y 500 m l of d i s t i l l e d wa te r , and s o l u t i o n s t o

which increments of H' as H C 1 equ iva l en t t o 20$, 40$, 808, of t h e exchange capa- c i t y of t h e sample were added. The r e s u l t s presented i n t a b l e 2 show t h e l e a c h i n g of t h e exchange complex of s o i l s t h a t t a k e s p l a c e wi th added increments of a c a t i o n . Presumably t h e a d d i t i o n s of increments of H i n a c i d r a i n f a l l would have similar e f f e c t s which would have t o be cons idered i n t h e con tex t of o t h e r c a t i o n s be ing cycled by t h e f o r e s t , and by t h e composi t ion of c a t i o n s a l r e a d y on t h e exchange complex of t h e s o i l . Follow- i n g t h i s l e a c h i n g , each s o i l p o r t i o n w a s analyzed f o r remaining exchangeable m e t a l l i c c a t i o n s .

These d a t a show t h a t given t h e s to- chiometry of t h e l e a c h i n g of c a t i o n s from t h e s o i l exchange complex by H t h e e f f e c t s of increments of a c i d r a i n f a l l t o a g iven s o i l may be s imula ted wi th so lu- t i o n s having composi t ions s i m i l a r t o t h a t of t h e r a i n f a l l . Also, as t h e increment of H i n t h e p r e c i p i t a t i o n inc reased , e i t h e r because of concen t r a t ion o r of volume of r a i n f a l l l e a c h i n g t h e s o i l would tend t o become hydrogen s a t u r a t e d , d i s p l a c i n g b a s i c m e t a l l i c c a t i o n s i n pro- p o r t i o n . In t h e f o r e s t s i t u a t i o n t h e s e would be leached out o f t h e s o i l p r o f i l e i n a base s a t u r a t e d s o i l , o r taken up by t h e v e g e t a t i o n .

CONCLUSIONS

This review of t h e l i t e r a t u r e and t h e p r e s e n t a t i o n of some o r i g i n a l work i s a p p l i c a b l e t o t h e e f f e c t of ch ron ic a i r p o l l u t i o n on minera l element c y c l i n g of f o r e s t s . The l i t e r a t u r e i s g e n e r a l , i l l u s t r a t i n g p roces ses , but i s no t s i t e s p e c i f i c except f o r t h e l o c a t i o n of t h e s t u d i e s . S ince e f f e c t s a t any s p e c i f i c s i t e may be i n small increments each y e a r , but s eve re i n cumulat ive e f f e c t s over a number o f y e a r s , a major remaining problem is t o f i n d ways of determining s i t e s p e c i f i c i n d i c a t i o n s of d e t r i m e n t a l e f f e c t s of such ch ron ic p o l l u t i o n . Some p e r t i n e n t conc lus ions from t h e l i t e r a t u r e reviewed i n t h i s paper a r e :

1 . The f o r e s t v e g e t a t i o n as is t r u e of any v e g e t a t i o n r e q u i r e s many e s s e n t i a l growth e lements which i t w i l l cyc l e i n a d d i t i o n t o o t h e r s mobilized by l o c a l minera l weather ing o r i npu t through pre- c i p i t a t i o n .

2. To t h e e x t e n t t h a t ch ron ic p o l l u t i o n adds e lements normally r equ i r ed by p l a n t s , o r chemica l ly mobile i n t h e p l a n t , t h e s e w i l l be cycled much as t h e o t h e r s on t h e s i t e .

3. The f o r e s t i s c r e a t e d i n a v a s t reduc-

t i o n r e a c t i o n wherein CO i s reduced t o organic compounds by Producers i n t h e ecosystem, and subsequent ly oxid ized i n energy r e l e a s i n g s t e p s by t h e s e p l a n t s o r by t h e Decomposers i n t h a t ecosystem.

4. The cyc l ing of e lements t a k e s p l ace i n t h e con tex t of t h e s e redox r e a c t i o n s , and those elements which change s t a t e w i th redox p o t e n t i a l change a r e u s u a l l y i n t h e reduced form i n t h e producer v e g e t a t i o n and subsequent ly oxid ized i n energy r e l e a s i n g s t e p s by t h e s e p l a n t s o r by t h e decomposers on t h e s i t e .

5. Chronic air p o l l u t i o n a d d i t i v e s t o t h e f o r e s t a f f e c t the c y c l i n g of e lements n o t on ly by d i r e c t a d d i t i o n s of t h e p o l l u t i n g elements t o t h e c y c l e s , bu t a l s o by a f f e c t i n g t h e redox s t a t u s of t h e absorb- i ng p l a n t t i s s u e , and o the r p o r t i o n s of t h e s o i l - v e g e t a t i o n system.

6 . Concentrat ion p o i n t s and s i n k s f o r t h e elements added i n chronic p o l l u t i o n e x i s t i n t h e va r ious p a r t s of t h e v e g e t a t i o n , t h e s u r f a c e d e t r i t u s on t h e s o i l , and i n t h e s o i l c a p a c i t i e s f o r abso rp t ion on ion exchange; hydrous ox ide complexes, and as i n s o l u b l e p r e c i p i t a t e s .

7. The e f f e c t s of chronic p o l l u t a n t s added t o a given f o r e s t and i t s e lementa l c y c l i n g processes w i l l be h igh ly s i t e s p e c i f i c ; depending upon c l i m a t e , degree of weathering development of t h e s o i l , t h e type of mine ra l s from which t h e s o i l is forming, t h e c h a r a c t e r i s t i c s of t h e f o r e s t s p e c i e s and t h e i r s tock ing densi- t i e s , t h e topographic s i t u a t i o n wi th regard t o a i r f l o w , and t h e n a t u r e of t h e p o l l u t a n t .

8. Local s i t e s p e c i f i c i n d i c a t o r s o f i n t e n s i t y of p o l l u t i o n e f f e c t may be v i s u a l as i n appearance and s i z e of f o l i - age, f o l i a r ana lyses f o r p o l l u t a n t e l e - ments and t h e i r r a t i o s t o background s i t e e lements , and s o i l assessment of capaci- t i e s t o absorb t h e added elements.

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Schnappinger, M. D. Martens, & C . Plank. 1975. Zino a v a i l a b i l i t y as inf luenced by, a p p l i c a t i o n of f l y ash t o t h e s o i l . Env. S c i . & Tech. 9:3 258-261 .

Shephard, J. & W. Funk. 1975. Trees as Environmental s e n s o r s moni tor ing long term heavy meta l contaminat ion of t h e Spokane R ive r , Idaho. h v . Sc i . & Tech. 9:7 638-642.

S l i n n , W. 1976.' Some approximations f o r t h e wet and d r y removal of p a r t i c l e s and gases from t h e atmosphere. Jou r . O f A i r , Water, and S o i l P o l l u t i o n . Accept- ed fo'r Publ.

Smith, W. 1973. Metal contaminat ion of Woody P l a n t s . Env. S c i & Tech. 7:7 631 -636.

S to t zky , G. 1974. A c t i v i t y , Ecology, & Popula t ion dynamics of microorganisms i n S o i l . i n Microbial Ecology by Las- k i n , A . I . & H. Lecheval ie r . CRC P r e s s Cleveland Ohio. pp. 73-1 35.

Stumm, W. & J . J . Morgan. 1970. Aquatic Chemistry. 583pp. Wi ley- In te rsc ience N.Y.

White, K.L., A.C. H i l l & J. Bennet t . 1974. S y n e r g i s t i c i n h i b i t i o n of appa ren t pho tosyn thes i s r a t e o f a l f a l f a by combinat ions of s u l f u r d iox ide and n i t r o g e n d ioxide . Env. S c i & Tech. 8:6 574-575

Witkamp, M. & M. Frank. 1969. Loss of weight of Co 60 & C s 137 from t r e e l i t t e r i n t h r e e subsystems of a watershed. Env. S c i & Tech. 3:11 1195- 1198.

Zinke, P. J. 1966. Fo res t i n t e r c e p t i o n s t u d i e s i n t h e United S t a t e s . pp. 137- I61 i n Fo res t Hydrology Proc. o f a Na- t i o n a l Science Foundation advanced Sci- ence Seminar Penn. S t a t e Univ. Penn. Pergamon P res s . N.Y.

Zinke, P. J. 1974. E f f e c t of Herb ic ides on s o i l s of South Vietnam.. P a r t B. Working Papers -The e f f e c t s of h e r b i c i d e s i n South Vietnam. 39pp. Nat iona l Ac. of S c i . , N a t . Res. Council . Wash. D.C.

Zinke, P . J . , A. S tangenberger , W. Colwell . 1979. The f e r t i l i t y of t h e f o r e s t . C a l i f o r n i a A g r i c u l t u r e 33: 5 1 0-1 1 .

Forest Genetics and Air Pollutant stress'

2Stefan Bialobok

Abstract : The breeding of t r e e s , p a r t i c u l a r l y c o n i f e r s , f o r c u l t i v a t i o n in regions under t h e in f luence of indus t ry i s of considerable economic importance. The r o l e of gene t ic polymorphism in t h e process of adap ta t ion t o such environments i s discussed. Resu l t s a r e presented of research on t h e g e n e t i c v a r i a b i l i t y in Scots pine populat ions growing under t h e in f luence of indus t ry and i n regions f r e e of gaseous po l lu t ion . Methods of s e l e c t i n g t r e e populat ions t o l e r a n t t o i n d u s t r i a l emissions a r e discussed aimed a t t h e i d e n t i f i c a t i o n of gene t ic markers of to le rance .

I n o r d e r t o reduce l o s s e s in f o r e s t ecosystems a s wel l a s i n some spec ies of broadleaf trees caused by i n d u s t r i a l emissions a t tempts were made (Gerhold et al , . , 1977). The g r e a t e r to le rance of t o determine t h e s e n s i t i v i t y of trees (depending Scots pine and Norway spruce t o t h e a i r p o l l u t i o n on t h e i r g e n e t i c p r o p e r t i e s ) t o acu te i n j u r y of within a population i s sometimes assoc ia ted with t h e a s s i m i l a t i o n apparatus by t h e most common t h e g r e a t e r r e s i s t a n c e t o low temperatures d i seases gaseous p o l l u t a n t s . The degree of p l a n t i n j u r y a i d a xerothermic adap ta t ion (Bialobok, 1979). A by gases i s dependent a l s o on t h e system of suggestion a l s o e x i s t s t h a t t h e cause of t o l e r -eco log ica l f a c t o r s opera t ing in t h e environment. ance t o some gases may depend on mechanisms t h a t

reduce t h e access of gases t o t h e p l a n t organism GENETIC VARIATION OF TOLERANCE BETWEEN AND WITH- (Gerhold et a l . , 1977). I N SPECIES

However, i t has been experimentally e s t a b l i s h e d So f a r a wide s c a l e of g e n e t i c v a r i a b i l i t y was o r deduced from r e l i a b l e evidence t h a t t h e r e

observed wi th in var ious spec ies of t r e e s and e x i s t g e n e t i c mechanisms condi t ioning higher shrubs i n t h e i r s e n s i t i v i t y t o a i rborne po l lu t ion . to le rance t o i n d u s t r i a l emissions (Niemtur, 1979). The r e s u l t s l i s t e d i n reviews (Davis et a l . , 1976, The l a t t e r i n v e s t i g a t o r s tud ied 58 progenies of Bialobok 1979) a r e only approximate. It appears Scots pine from 4 provenances obtained from seeds t h a t most t o l e r a n t a r e some spec ies of broadleaf c o l l e c t e d on remnant l i v i n g t r e e s in t h e h igh ly trees. Coniferous t r e e s which a r e of g r e a t e r po l lu ted condi t ions of t h e Upper S i l e s i a n indus-economic importance a r e genera l ly charac te r i sed t r i a l region. He has shown t h a t these progenies by low to le rance . have a g r e a t e r to le rance than those c o l l e c t e d

from t r e e s growing beyond t h e range of p o l l u t i o n . It was a l s o found t h a t t h e r e is g e n e t i c

v a r i a b i l i t y in response t o SO^, O3 and HF POLYMORPHISM AND ITS ROLE wi th in one populat ion of Pinus s y l v e s t r i s , P. s t robus , P. ponderosa and within Picea a b i e s S tud ies on t h e g e n e t i c v a r i a b i l i t y of enzymes

in f o r e s t t r e e s developed s t r o n g l y a f t e r S t e m , (1974) pointed o u t t h e g r e a t importance of gen-

p r e s e n t e d a t t h e Symposium on E f f e c t s of A i r e t i c polymorphism f o r t h e development of ecolog-

P o l l u t a n t s on Mediterranean and Temperate Fores t i c a l g e n e t i c s , f o r e s t gene t ics and t r e e breeding.

Ecosystems, June 22-27, 1980, Rivers ide, Cal i for-n i a , U.S.A. Thanks t o t h i s method i t i s poss ib le t o

recognize t h a t g e n e t i c s t r u c t u r e of a populat ion

2 ~ r e eB i o l o g i s t , I n s t i t u t e of Dendrology, P o l i s h ( a l l e l e f requencies and degree of heterozygosi ty)

Academy of Sciences , 63-120 Kornik, Poland. in space and time, t o conduct s t u d i e s on i n h e r i t -ance and l inkage , t o determine t h e gene t ic d i s t a n c e

between ind iv idua l s and populat ions , t o i d e n t i f y mechanisms of adap ta t ion t o an environment and t o employ i t in p r a c t i c a l f o r e s t r y .

Polymorphism of f o r e s t trees which a r e long- l i v i n g organisms r e p r e s e n t s adapt ive s t r a t e g i e s of populat ions t o a changing environment (Stern e t a l . , 1974). In t h i s gene t ic system hetero- zygotes a r e favored and thus t h e population is capable of e x i s t i n g i n a heterogenic environment surviving numerous and major changes.

, Tree populat ions in i n d u s t r i a l regions grow under s i m i l a r condi t ions a s t h e herbaceous p l a n t s t h a t co lon ize m i n e s p i l l s having high concen t ra t ions of heavy elements (Pb, Zn, Cu). This phenomenon S t e m (1974) a l s o cons iders a s being a good example of t h e developing polymorphism.

I n condi t ions where a t l e a s t a p a r t of t h e t r e e s can surv ive i n an i n d u s t r i a l environment t h a t has n o t been too s t r o n g l y po l lu ted , the populat ion adopts t h e optimal s t r a t e g y i n reac-t i o n t o t h e changes t ak ing place. This, of course , i s t h e r e s u l t of t h e evolut ionary adap ta t ion process t o t h e new environmental condi t ions where t h e g e n e t i c system i s under a cons tan t s e l e c t i o n pressure . Tolerant genotypes appear t o have a c e r t a i n l e v e l of f i t n e s s t o t h e i n d u s t r i a l environment. What is most important t o us i s t h a t t h e d r a s t i c changes in the i n d u s t r i a l environment should n o t exceed the l e v e l of g e n e t i c f l e x i b i l i t y of t h e popula- t i o n s of t h e most important f o r e s t forming spec ies . I n t h e acute" condi t ions of change i n an i n d u s t r i a l environment, t h e coded gene t ic system wi th in a populat ion, t h a t condi t ions i t s adapt ive capac i ty , gradual ly ceases t o opera te s i n c e t h e p o t e n t i a l of ind iv idua l genotypes f o r adap ta t ion has been surpassed.

GENETIC VARIABILITY OF ENZYMES I N SCOTS PINE POPULATIONS

The use of e l e c t r o p h o r e t i c a n a l y s i s of enzymes f o r t h e i d e n t i f i c a t i o n of v a r i a b i l i t y determining g e n e t i c to le rance t o i n d u s t r i a l p o l l u t i o n i s so f a r only i n an in t roduc tory phase. The r e s u l t s obtained so f a r a r e encouraging. The s t u d i e s conducted on Scots p ine a r e t r e a t e d only a s a model.

Mejnartowicz (1978) has s tud ied t h e var ia - b i l i t y of izozymes of leucyloaminopeptidase (LAP) and a c i d phosphotase (APH) in 19 populat ions of Sco ts p ine from t h e whole range of t h e spec ies in Eurasia . The Poland populat ions were chosen fromregions under i n d u s t r i a l in f luence and from reg ions beyond p o l l u t i o n . I n a l l t h e populat ions APH was coded in locus B wi th 15 a l l e l e s , and t h e r e was considerable polymorphism in t h e s t u d i e d populat ions , and LAP was coded in 2 l o c i , LAP-A having 5 a l l e l e s and LAP-B 6 a l l e l e s .

It i s i n t e r e s t i n g t h a t t h e population of Scots pine from Babki ( c e n t r a l Poland--strong indus-t r i a l po l lu t ion) has had t h e lowest degree of heterozygosi ty on locus LAP-A, ha0.1124 and t h e h ighes t va lue i n LAP-B, h=0.3970. Among individ- u a l s s e n s i t i v e t o SO2 t h e genotype APH-B4/B6 dominated and among ind iv idua l s t o l e r a n t t o t h i s gas t h e a l l e l e APH-B5 appeared commonly (Mejnartowicz, 1977-78). Szmidt (1978) when studying t h e gene t ic polymorphism of c a t a l a s e i n t h r e e populat ions of Scots pine from i n d u s t r i a l regions and 5 populat ions from regions f r e e of p o l l u t i o n , has found 7 phenotypes of t h e ca ta lase . When comparing t h e populat ions on t h e b a s i s of heterozygosi ty he has shown t h a t popula- t i o n s from regions f r e e of p o l l u t i o n were charac-t e r i z e d by g r e a t e r p a r t i c i p a t i o n of homomorphic ind iv idua l s of t h e type C-l /C-1 compared t o populat ions under t h e in f luence of emissions.

Mejnartowicz, e t a l . , (1978) having taken m a t e r i a l from p l u s t r e e s in a Scots p ine seed orchard e s t a b l i s h e d a l a c k of c o r r e l a t i o n between t h e degree of heterozygosi ty of t r e e s i n LAP l o c i and t h e degree of t h e i r s e n s i t i v i t y t o t h e a c t i o n of SO2 in a l abora to ry t e s t .

These in t roduc tory r e s u l t s i n d i c a t e t h a t t h e r e i s d i f f e r e n t i a t i o n in t h e frequency of some a l l e l e s in a populat ion depending on t h e inclu- ence of i n d u s t r i a l emissions. The important th ing i s t h a t an enzymatic marker b e found f o r to le rance which would be independent of environ-mental inÂ luences . INHERITANCE OF TOLERANCE TO INDUSTRIAL EMISSIONS

Not many i n v e s t i g a t o r s have attempted determining in genera t ive progeny t h e combining a b i l i t y , h e r i t a b i l i t y and r e p e a t a b i l i t y of to le rance t o i n d u s t r i a l emissions. I n t h e case of Scots p ine h e r i t a b i l i t y and r e p e a t a b i l i t y of to le rance t o Oq is t o be found under a low o r medium gene t ic c o n t r o l . However, some provenances have a h igher h e r i t a b i l i t y of to le rance t o 03. Needle i n j u r y in these pines was p o s i t i v e l y c o r r e l a t e d wi th t h e i n j u r i e s caused by SO2 (Gerhold e t a l . , 1977, Demeritt, 1977). Bialobok e t a l . , (1978) have a l s o found a s i g n i f i c a n t c o r r e l a t i o n between t h e degree of needle i n j u r y on mother t r e e s and on t h e i r progenies following treatment wi th SO?. However, t h e s e c o r r e l a t i o n s were n o t found following treatment with 03 o r a mixture of 03 and SO2.

The s e l e c t i o n of t r e e ind iv idua l s t o l e r a n t t o i n d u s t r i a l emissions i s being done by t h e r e l a - t i v e l y simple methods of mass s e l e c t i o n , without understanding t h e gene t ic b a s i s f o r t h e popula- t i o n s t r u c t u r e . This s e l e c t i o n i s usua l ly being conducted on seed l ings in labora to ry condi t ions . Sometimes p o s i t i v e r e s u l t s were obtained f o r t h e p r a c t i c e which with some p r o b a b i l i t y a r e being u t i l i z e d in e s t a b l i s h i n g tree p l a n t a t i o n s o r producing t r e e s f o r ornamental purposes (Demeritt , 1977).

So f a r i t was n o t poss ib le t o so lve t h e prob- l e m of breeding var ious pine spec ies f o r cu l t iva - t i o n in f o r e s t s under t h e in f luence of i n d u s t r i a l emissions, and t h e r e i s no cheap way of propaga-t i o n of s e l e c t e d ind iv idua l s .

Gerhold, (1977) has discussed s e v e r a l methods of breeding trees more t o l e r a n t t o i n d u s t r i a l emissions , i n which t h e use of seeds orchards e s t a b l i s h e d from t o l e r a n t c lones i s envisaged.

It appears, however, t h a t it would be va luab le t o expand t h e i n v e s t i g a t i o n s of gene t ic va r ia - b i l i t y of enzymes in populat ions of coniferous trees endangered by i n d u s t r i a l po l lu t ion . W e have considerable information a l ready on t h e course of metabol ic c y c l e s in t h e tree organism exposed t o t h e a c t i o n of some gases. I b e l i e v e these two sources of information could be combined, (biochemical gene t ics and metabolic changes) in order t o i d e n t i f y t h e enzymatic gene t ic marker t h a t would be use fu l i n t h e s e l e c t i o n of t o l e r a n t populations.

LITERATURE CITED

Bialobok, Stefan. 1979. I d e n t i f i c a t i o n of r e s i s t a n t o r t o l e r a n t

s t r a i n s and a r t i f i c i a l s e l e c t i o n o r produc- t i o n of such s t r a i n s in order t o p r o j e c t vege ta t ion from a i r po l lu t ion . Symp. on t h e e f f e c t s of a i r b o r n e p o l l u t i o n on vege ta t ion , Warsaw (Poland) 20-24 Aug. 1-16, 1979.

Demeritt, Maurice E. JK. 1977. Genetic Evaluation of Two-Year Height

and Ozone Tolerance in Scotch Pine (Pinus s y l v e s t r i s L.) . A Thesis i n Genetics. The Pennsylvania S t a t e Univers i ty .

Davis, Donald D. and Raymond G. Wilhour. 1976. S u s c e p t i b i l i t y of woody p l a n t s t o su l -

f u r d iox ide and photochemical oxidants . EPA-600/3-76-102. p. 72. U. S. Environmental Pro tec t ion Agency, C o r v a l l i s , Oregon 97330.

Gerhold, Henry G. , and Raymond G. Wilhour. 1977. E f f e c t of a i r p o l l u t i o n on Pinus

s t r o b u s L. and g e n e t i c r e s i s t a n c e . A Li te ra -t u r e Review. EPA-600/3-77-002 p. 45 Environ- mental P r o t e c t i o n Agency, Corva l l i s , Oregon, 97330.

Mejnartowicz, Leon. 1977-1978. Genetic c h a r a c t e r i s t i c of some

Scots pine t r e e s suscep t ib le or somewhat r e s i s t a n t t o t h e a c t i o n of SO . Annual Report from P r o j e c t PL-Fs-74 from U. S. Department of Agricul ture under PL-480.

Mejnartowicz, Leon. 1978. S t ruk tura genetyczna populac j i sosny

zwyczajnej z terenow przemyslowych zanieczy- szczonych przez S02. In Proc. from: Reakcje biologiczne drzew na e m i s je przemyslowe. Kornik 4-5 maj 1978.

Mejnartowicz, L., S. Bialobok and P. Karolewski.

1978. Genetic c h a r a c t e r i s t i c of Sco ts p ine specimens r e s i s t a n t and s u s c e p t i b l e t o SO2 ac t ion . Arboretum Komickie . 23: 233-238.

Mejnartowicz, Leon. 1979. Genetic v a r i a t i o n i n some isoenzyme

l o c i i n Scots p ine (Pinus s i l v e s t r i s L.) population. Arboretum Komickie . 24: 91-104.

Niemtur, S tanislaw. 1979. Badania nad wewnatrzgatunkowym

zroznicowaniem odpomosci sosny zwy- c z a j n e j (Pinus s i l v e s t r i s L.) na emisje przemyslowe. Doctoral Thesis , Uniwersytet &ski , Katowice.

S t e m , K. and P e t e r M. A. T i g e r s t e t . 1974. Okologische Genetic. 98-p. 75 p. G.

Fischer. S t u t t g a r t .

Szmidt, Alfred. 1978. Zmiennosc ka ta lazy w populacjach

sosny zwyczajnej znajdujacych s i e pod wplywem zanieczyszczen przemyslowych. I n Proc. from: Reakcje biologiczne drzew na emisje przemyslowe. Komik 4-5 maj 1978.

Interactions of Air Pollutants and Plant

Michael reshow^

Abstract: Each in te rac t ion between an a i r pollu-t a n t and disease is unique. Pol lutants may m i t i -gate disease response or in tens i fy it; and the presence of ce r t a in diseases can modify the p lan ts response t o a pol lutant . Air po l lu tan ts can a c t d i r e c t l y on a fungus or bac te r ia inh ib i t ing parasi- t i s m . They may a l so ac t most s t rongly on the hos t , modifying i t s physiology and rendering it e i t h e r more or l e s s sens i t ive t o a plant pathogen. Where t he plant is weakened by the po l lu tan ts , it tends t o be more s ens i t i ve t o weak pathogens, but l e s s s ens i t i ve t o obl igate parasi tes . Where the pollu-t an t physical ly in jures the host, in fec t ion may be f a c i l i t a t e d . Pol lutant in te rac t ions have been demonstrated both i n the laboratory and the f i e l d a t ambient pol lutant concentrations. In te rac t ions between pol lu tan ts and ab io t i c s t r e s s a r e part icu-l a r l y c r i t i c a l . Water regime, temperature rela-t ions , mineral nu t r i t i on and other parameters of the physical environment play a major ro le i n the expression of a i r pol lut ion injury.

Air po l lu t ion can k i l l plants . Even when the concentrations of an a i r po l lu tan t a re not d i r e c t l y l e t h a l , they may be harmful, adversely a f f e c t i n g growth, reproduction and myriads of other b io log ica l processes (Mil ler and McBride 1975). One such process is the i n t e r ac t i on t ha t r e s u l t s between the po l lu tan t and plant pathogens.

There a r e many ways i n which such i n t e r -ac t ions might take place. But do they? The most obvious would be i f the pol lutant d i r ec t l y a f fec ted the fungus, v i rus , bac te r ia ,

p r e s e n t e d a t t he Symposium on Effec ts of A i r Po l l u t an t s on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, Ca l i forn ia , U.S.A.

2 ~ r o f e s s o r of Biology, University of Utah, S a l t Lake City, Utah 84112.

i n sec t or other pathogen. I f some stage of an organism's l i f e cycle , o r some s t age of paras i t -i s m , were adversely impaired by a po l lu tan t , the pol lutant e s sen t i a l l y would be ac t ing as a fungicide, bacter iocide or other biocide and could be expected t o bring about some degree of control.

The second way an a i r pol lutant might a c t would be i n adversely a f f ec t i ng the growth or reproduction of the host plant and thereby influencing i t s s u i t a b i l i t y as a host. There a r e two ways i n which such act ion could be brought about. Most apparently, the po l lu tan t might cause some physical in jury t o the plant leaving les ions t ha t could serve a s i n f ec t i on cour t s for a fungus or bacteria. O r , the plant might simply be weakened, thus lowering i t s res i s tance t o a prospective pathogen. Presum-ably the weaker pathogens, the f acu l t a t i ve pa ra s i t e s , would benef i t most by such

--

conditions. Obligate parasites, on the other hand, preferring a vigorous host, might respond quite differently and their development might even be discouraged in the weakened host.

Conversely, the impact of various diseases or plant stresses on the plant's response to air pollutants has also been considered. It should be quite apparent that adverse climatic or edaphic factors might affect a plant's sensitivity to a pollutant, but the presence of certain biotic diseases may also increase or decrease a plant's sensitivity.

A major question is not so much do such interactions take place, but what concentrations of an air pollutant are required to precipitate such effects, and how widely do such concentrations occur?

Many of the interactions that will be discussed have been demonstrated under laboratory conditions, often at pollutant concentrations known to be fairly widespread. Some of the interactions have been observed in the field.

The literature treating such air pollutant- plant pathogen interactions has been reviewed most recently in 1978 (Laurence), 1975 (Treshow), and 1973 (Heagle); it is not the intent of this paper to once again provide an exhaustive review of this literature. Rather, I should like to first bring the literature up to date, briefly including that delving into the interactions of abiotic stresses on pollutant effects, and discuss the implication and possible practical relevance of such interactions, especially concerning forest ecosystems. Pri-marily I should like to develop some of the principles in pollutant-pathogen interactions.

INFLUENCE OF POLLUTANTS ON DISEASE EXPRESSION

Sulfur Dioxide

There is no question that sulfur dioxide interacts with fungi, suppressing their growth and acting fungicidally. The only question concerns the SO2 concentrations at which such interactions occur.

A few examples exist where SO2 has acted in such a way in the field, limiting the development of certain plant diseases. The examples provided by Scheffer and Hedgcock (1955) in which parasitic fungi generally appeared to be retarded or inhibited near smelters where SO2 was present is most often cited (Treshow 1975). Suppressed disease development was especially apparent where rust fungi, Melampsora and Puccinia, or needle cast fungi were involved. Linzon (1973) also discusses the reduced heart rot and blister rust (Cronartium ribicola) near a smelter.

But such incidents are becoming more infrequent as ground level SO2 concentrations become reduced by modern control technology or use of tall stacks. Higher SO2 concentrations, often exceeding 1 ppm for extended periods, now tend to be of only historic record. We are now interested in the possible impact of SO2 concentrations in the 0.1 to 0.5 ppm range or even lower in cases of prolonged duration. Where such concentrations still exist near smelters, power plants, or large urban centers, some pollutant-pathogen interaction might be sought.

There is some evidence from laboratory and <

field research that certain pathogenic fungi respond to SO2 in this concentration range. Weinstein and others (1975) for instance, have demonstrated that SO2 concentrations of 0.14 to 0.15 ppm, continuous for 7 days, while not visibly injuring plant foliage, affected the bean rust fungus, Uromyces. The incidence and severity of the rust as measured by the abundance of uredia was decreased as were both the size and percent germination of the uredo- spores. Hence the reproductive potential of the pathogen was reduced. The results suggested that the effect on the pathogen was indirect; perhaps involving an 802-induced chemical change in the resistance of the host and its suitabil- ity as a habitat for the fungus. The authors speculated that production of phytoalexins or supply of metabolites might have been altered, or compounds derived from SO2 might have accumulated.

One of the most comprehensive field studies of the interactions of industrial air pollutants, especially SO2, with plant disease was conducted by A. Grzywacz and J. Wazny (1973). The study was notable since it dealt with economically significant diseases of a coniferous forest, specifically Scots pine (Pinus sylvestris L.). Interactions with six fungi were considered: Armillaria mellea, Fomes annosus, Lophodermium pinastri, Microsphaera alphitoides, Melampsora pinitorqua, and Cronartium flaccidium.

In an overall study, comparisons were made of disease presence in industrial areas and forests throughout Poland. In a more detailed approach, disease presence was compared at increasing distances from an industrial town, Torun, with one major SO2 source.

The general comparisons showed that Armillaria was present in 3.7 percent of the trees in the area damaged by SO2 compared with only 1.38 percent in all forests. Lophodermium also tended to be more serious in the industrial areas, but the results were indefinite. This was consistent with earlier findings of Donabauer (1966) that high SO2 concentrations increased the intensity of Armillaria root rot.

Fomes showed the reverse trend and occurred

in 0.87 percent of the areas affected by industrial pollution compared with 1.5 percent in the country as a whole. Fomes, as in the overall study, was least prevalent in areas of highest SO2 concentrations. Grzywacz and Wazny (1973) found that stumps close to the SO2 source were sound. Related, decomposition fungi were also less abundant closest to the source. Only 50 percent of the stumps showed signs of decomposing, and 10 percent strongly decomposing, compared with 30 percent strongly decomposing farther out. However, Gryzwacz (1978) later reported that stands influenced by air pollution were more subject to decomposition by brown, white or soft rot fungi. Sufficiently high SO2 concentrations might suppress the fungal growth directly. Such was the case where Mejstrik (1978) showed SO2 concentrations as low as 84 ug/m3 (.03 ppm) inhibited growth of Flamulina velopes, Nematoloma fasciculare, and Pleurotus ostreatus from 34 to 39 percent.

Lophodermium injury was least significant near the SO2 source. At distances beyond 1 km injury appeared on up to 70 percent of the needles. There was a slight decrease beyond this. When annual SO2 concentrations averaged below 0.2 ppm, disease incidence was essentially the same as in the control group. Fungus development was noticeably affected. Within 1 km, reproduction was largely by pycnidia; further distant, apothecia were common. The numbers of needles with both the sexual and asexual stages increased with distances. Closest to the SO2 source, apothecia were only 15 percent the length of controls deformed, collapsed, under- developed, closed or even dried up and with ill- developed asci. Chiba and Tanaka (1968) however reported high SO2 concentrations of 2 ppm for 14 hours caused increased infection of injured pine needles (P. densiflora) by Rhizosphoera kalkhoffii.

Weidensaul and Darling (1979) inoculated Scots pine seedlings with the fungus Scirrhia acicola. The plants were inoculated either 5 days before or 30 minutes after fumigation for 6 hours with 533 ug/m3 (0.20 ppm) SO2). After 8 weeks, the seedlings inoculated 5 days before fumigations had more lesions incited by the fungus than those inoculated 30 minutes af ter fumigations in the control group. It was postulated that since the needle blight fungus pene- trates through the stoma, the ability of the SO2 to keep the stoma open facilitated entry of the fungus.

The pollutant-disease interaction may vary with the host species. Ham (1971) found that when loblolly pine served as the host, the brown spot fungus (5. acicola) was not measurably affected by SO2 in the 0.5-0.9 ppm range for 2-3 hours even when SO2 caused visible injury.

Simulated rain, acidified with sulfuric acid has also been shown to influence pollutant-

pathogen interactions (Shriver 1974). Although not involving forest species, the work did demonstrate the way in which plant species might be affected.

Kidney beans (Phaseolus vulgaris var. red kidney) and willow oak (Quercus phellus) were exposed to simulated rain acidified to a pH of 6.0 or 3.2 for 10 minutes each day for 30 to 60 days. The acid "rain" caused an 86 percent inhibition in the number of telia produced by Cronartium fusiforme on willow oak, a 66 percent inhibition in the reproduction of the root knot nematode (Meloidogyne hapla) on beans in the field, and a 29 percent decrease in the percent of leaf area of field erown beans affected by "-- -- - - - - - -

Uromyces phaseoli. Exposures to pH 3.2 "rain" completely destroyed the integrity of the cuti- -cular waxes in both oak and bean. Exposures to the pH 6.0 solution did not visibly alter the cutin. Shriver postulated that damage to the cutin facilitated leaching of carbohydrates from the leaf including those that might inhibit hyphal growth of Botrytis cinerea thus predisposing plants to infection.

This is consistent with the findings of F. A. Last and 0. D. Fowler at the Institute of Terrestrial Ecology at Penicuik, Scotland (personal communication) who showed that the cuticle of Scots pine was gradually broken down by low concentrations, of S02.

Sulfur dioxide, perhaps largely as acid rain, may have an effect on soil microorganisms (Wainwright 1978). Sulfur-oxidizing microorganisms, including Alternaria tenuis, Auriobasidium pullulans and Cephalosporium sp., were isolated from leaves, litter and soils polluted with high levels of S02. The predominant autotroph on leaf surfaces was Thiobacillin thioparis.

Hibben and Taylor (1975) found that S02- pathogen interaction depended on the infection stage. Conidial gemination and the appres- sorial stages of Microsphaera =were most sensitive to S02. Since infection was not reduced when leaves were previously fumigated, the effect was thought to be mostly fungicidal.

Ozone

There is considerable evidence that photochemical pollutants, most notably ozone, affect plant pathogens and fungus-host interactions. The interaction may be positive or negative depending on the 03 concentrations and the 03 sensitivity of the host.

In one such study, Miller and Elderman (1977) showed that fumigation of ponderosa and Jeffrey pine seedlings with ozone enhanced infection by Fomes annosus. Average infection of the two

species increased from 57 percent to 78 percent when the seedlings were exposed to 431.2 pg/~3 (.25 ppm) ozone. They also found that ozone injury increased the susceptibility of pine stumps to colonization by Fomes annosus. In the laboratory, wood from trees slightly damaged by oxidants was more decay-susceptible than wood from severely damaged trees.

Far more research has involved powdery mildew (Heagle and Strickland 1972, Heagle 1975, Scheutte 1971), and the negative impact of ozone on disease. Even ozone concentrations in the 5 to 50 pphn range reduced infection when conidia were exposed. According to Scheutte, appresoria formation was largely affected. Also, some epidermal cells, hypersensitive to ozone, were killed thereby reducing infection. Eight hour exposure to 50 pphm ozone reduced formation of secondary hyphae 66 percent and 4 hour exposure reduced 41 percent. Ozone impaired formation of the penetration peg thus inhibiting subsequent development of a functional host-parasite relationship.

While ozone impacted certain critical stages of infection under controlled conditions, in the field such effects would be less apparent since all stages of parasitism would be present simultaneously.

Interactions of facultative parasitic and saprophytic fungi with their hosts may also occur and are most pronounced when the plants are weakened or injured by ozone (Manning 1975). Obligate parasitism appears to be retarded by ozone and ozone-injured host tissue. Colonization of ozone-in jured white pine needles by Lophodermium pinastri was reduced while colonization by the saprophyte Aureobasidium pullulans was increased. Ozone-injured lilac leaves were rarely infected by powdery mildew Micosphaera a.

When the fungus is especially sensitive to ozone the impact may be mostly fungicidal thereby reducing infection. Sporulation and germination of the weak parasite Botrytis cinerea was significantly inhibited by 2, 6 hour ozone exposures at a concentration of 30 pphm (Krause and Weidensaul 1978). There was also less infection, based on total lesion area, when plants were exposed to 15 pphm. Ozonation of conidia produced in vivo and in vitro decreased germination of conidia, germ tube length, and pathogenicity. The authors postulated that the mode of action was to alter the permeability of the conidia membrane. Ozone may increase the conidiophore respiration causing prematurely- formed and non-viable conidia. Ozone also may inhibit, directly or indirectly, enzyme activity of the fungus and cause less maceration of the host cells resulting in a decreased infection.

Curtis and others (1976) found that plants exposed to ozone produced peroxidases and iso-

flavonoids that are toxic to microorganisms. According to Laurence and Wood (1978), ozone inhibited infection of soybean by Pseudomonas glycinea presumably because of a bacteriostatic compound, possibly an isoflavinoid compound, produced in response to ozone.

Fluoride

Fluoride is accumulated in the foliage of plants and affects many metabolic processes. Consequently, it is reasonable to presume that pollutant-pathogen interactions can be influenced, perhaps to a greater extent than with any other pollutant. This was confirmed with viruses by some of the early work reviewed by Heagle (1973) and Treshow (1975).

Host-fluoride interactions also have been demonstrated for fungi (McCune and others 1973) although not on forest species. Studying the interactions of 7 to 10 with 3 diseases of bean and 2 diseases of tomato, HF consistently reduced uredial formation as the foliar fluoride content increased. Tender green beans exposed to HF and inoculated with powdery mildew conidia developed fewer foliar lesions than non- fumigated control plants; 4.4 compared with 48.7 on fumigated leaves having an average of 399 ppm F. Powdery mildew was reduced proportionate to the length of the exposure period. Early blight lesions on tomato were similarly reduced by the presence of fluoride.

INFLUENCE OF DISEASE ON POLLUTANT SEVERITY

Not only may the presence of a pollutant influence pathogenicity, the reverse may be true~presence of diseases influence the degree of pollutant injury. This has best been demonstrated with viruses. None of these involved forest species though, and there has been no new results published since last reviewed by Laurence (1978).

Also, in the forest, variation in pollutant resistance among individual trees would far exceed any disease and pollutant interaction, and any impact of a disease on pollutant severity probably wouldn't be measurable.

ABIOTIC STRESS

Severity of air pollution injury is determined not only by the dose of the pollutant to which plants are exposed but on the predisposition of the plant. Predisposition is determined by any environmental parameter to which the plant is subjected. It has been discussed more in passing than as a major concern (Heck and others 1965, Heck 1968, Treshow 1970, Taylor 1974), but the interactions of abiotic stress or disorders with any pollutant is far more

significant than with biotic pathogens. Moisture stress, the light regime, edaphic factors and temperature relations all influence the sensitivity of plants to every pollutant.

Unusually high or low temperatures prior to exposure tend to reduce plant sensitivity to ozone, for instance. A normal high light intensity renders plants more sensitive. High humidity, by encouraging open stomates , also increases sensitivity. In dry air, plants are more tolerant of ozone than at higher humidi- ties, and PAN injury is most severe in the Los Angeles area when the relative humidity exceeds 50 percent.

Any factor favoring moisture stress and reduced water uptake would cause stomatal closure and favor resistance to pollutant uptake and injury. In this way, plants in more saline soils are more tolerant of certain pollutants (Oertli 1958) and there is little to no ozone or PAN injury when soil moisture is deficient.

Ozone injury may be negligible when ambient air temperatures during and after exposure are below 90Â F., yet may be severe when temperatures exceed 90' F. (Taylor 1974).

Effects of low atmospheric and soil moisture on tolerance or sensitivity of plants to SO2 injury are well known; suffice it to note that plants are far more sensitive under higher moisture conditions.

Mineral nutrition also plays arole in pollutant sensitivity. Vegetable crops are known to be most susceptible to ozone when nitrogen nutrition is adequate although some reports suggest injury is greatest when nitrogen is low. Sulfur dioxide sensitivity is reported to be greatest with increased sulfur nutrition. Stomata1 behavior may be involved since a deficiency of nitrogen, potassium or phosphor,us may decrease stomatal opening. Plants low in sulfur had the lowest stomatal capacity, thus less capacity for gas absorption (Leone and Brennan 1972).

Toxicity from heavy metals also plays an interesting role with air pollutants. Ormrod (1977) has found that ozone toxicity was enhanced on pea plants growing in elevated concentrations of cadmium or nickel. However, when cadmium concentrations were sufficiently high to adversely affect growth,100 umol of CdS04, then ozone injury was less than that of control plants.

Harkov and others (1979) found that the amount of ozone injury depended on the cadmium and ozone levels as well as other environmental conditions. Where environmental conditions were not conducive to ozone in jury (e .g. bright sunlight), cadmium had little effect on the amount of leaf damage. When environmental

conditions allowed only slight to moderate foliar injury on tomato leaves, damage was enhanced by cadmium treatment especially at higher concentrations.

Along the same line, low concentrations of SO2 affected metal uptake, increasing zinc and cadmium susceptibility of bean plants. Foliar injury caused by heavy metals was significantly enhanced by SO2 (Krause and Kaiser 1977).

Lamoreaux and Chaney (1978) also found significant interactions between cadmium and S02. While cadmium or SO2 alone reduced net photosynthesis and transpiration of excised silver maple leaves, the reduction in cadmium-treated leaves was greatest in the presence of S02.

CONCLUSIONS

Virtually every environmental parameter, biotic and abiotic can interact with air pollutants to aggravate or mitigate the extent of pollution damage. The significant question then becomes, to what extent and at what concentrations? Is the net impact real, and if so, how meaningful is it under field conditions?

All pollutants don't interact the same. Sulfur dioxide, for instance, appears primarily to act fungicidally reducing disease and decomposition activity. It is also postulated though that SO2 induces chemical changes imparting resistance to certain pathogens. Ozone tends to act more on the host, weakening it and accentu- ating disease activity. Research with vegetable crops at low ozone concentrations indicate that pollutant-disease interactions do occur with some diseases and very likely occur in forest stands weakened by photochemical pollutants. Ozone has increased susceptibility to Fomes and rendered trees more susceptible to decay. Each interaction is unique since every fungus has its own sensitivity as does each plant. Thus the potential for interaction is enormous.

Pollutants such as fluoride that accumulate significantly in plants would likely have the greatest interaction. While the trend is to inhibit disease development, the concentrations at which this has been demonstrated are now infrequent in the field.

The significance of abiotic stress and pollutant interactions is often taken for granted, but it should be emphasized that this is of paramount importance. Climatic and edaphic factors are often determinants in the expression of pollutant damage. While the abiotic environment strongly influences the severity of air pollution damage, air pollutants influence the severity of plant diseases caused by biotic pathogens. It would appear that as in all life systems, every environmental parameter has some influence on every other. In the case of

pollutants and pathogens, this interaction can be significant.

LITERATURE CITED

Chiba, 0. and K. Tanaka. 1968. The effect of sulfur dioxide on the development of pine needle blight caused by Rhizosphaera kalkhoffii Bubak (I). J. Jap. For. Soc. 50: 135-139.

Curtis, C. R., R. K. Howell and D. F. Kremer. 1976. Soybean peroxidase from ozone injury. Environ. Pollut. 11:189-194.

Donabauer, E. 1966. Secondary damage to forest caused by industrial exhaust fumes. Mitt. Forst. Bundesvers. 73:lOl.

Grzywacz, A. 1978. Interactions between air pollutants and decaying fungi of pine wood. In. 3rd Internat. Congress of Plant Pathology. Munchen. 1978.

Grzywacz, A. and J. Wazny. 1973. The impact of industrial air pollutants on the occurrence of several important pathogenic fungi of forest trees in Poland. Eur. J. For. Path. 3:129-141.

Ham, Donald L. 1971. The biological interactions of sulfur dioxide and Scirrhia acicola in loblolly pine. Ph.D. Thesis, Duke Univ., No. Carol. 75 p.

Harkov, R., B. Clarke and Eileen Brennan. 1979. Cadmium contamination may modify response of tomato to atmospheric ozone. J. Air Poll. Control Assoc. 29: 1247-1249.

Heagle, A. S. 1973. Interaction between air pollutants and plant parasites. Ann. Rev. Phytopathol. 11:365-388.

Heagle, A. S. 1975. Response of three obligate parasites to ozone. Environ. Pollut. 9:91-95.

Heagle, A. S. and Alice Strickland. 1972. Reaction of Erysiphe graminis f. sp. hordei to low levels of ozone. Phytopathol. 62:1144-1148.

Heck, W. W. 1968. Factors influencing expression of oxidant damage to plants. Ann. Rev. Phytopathol. 6:165-188.

Heck, W. W., J. A. Dunning and I. J. Hindawai. 1965. Interactions of environmental factors on the sensitivity of plants to air pollution. J. Air Poll. Control Assoc. 15:511-515.

Hibben, C. R. and M. P. Taylor. 1975. Ozone and sulfur dioxide effects on the lilac powdery mildew fungus. Environ. Pollut. 9:105-114.

Krause, G. H. M. and H. Kaiser. 1977. Plant response to heavy metals and sulfur dioxide. Environ. Pollut. 12:63-71.

Krause, C. R. and T. C. Weidensaul. 1978. Effects of ozone on the sporulation, germination, and pathogenicity of Botrytis cinerea. Phytopathol. 68:195-198.

Lamoreaux, R. J. and W. R. Chaney. 1978. Photosynthesis and transpiration of excised silver maple leaves exposed to cadmium and sulphur dioxide. Environ. pollut. 17:259-268.

Laurence, J. A. 1978. Effects of air pollutants on plant- pathogen inteactins. 71st Ann. Mtg. Air Poll. ControlAssoc. Houston, Texas. 1978.

Laurence, J. A. and F. A. Wood. 1978. ~f fects of ozone on infection of soy bean by Pseudomonas glycinea. Phytopathol. 68:441-445.

Leone, I. A. and Eileen Brennan. 1972. Sulfur nutrition as it contributes to the susceptibility of tobacco and tomato to SO2 injury. Atmos. Environ. 6:259-266.

Linzon, S. N. 1973. The effects of air pollution on forests. Pap. 4th It. Chem. Cong. Conf. 1973 pp. 1-18.

Manning, W. J. 1975. Interactions between air pollutants and fungal, bacterial and viral plant pathogens. Environ. Pollut. 9: 87-90.

McCune, D. C., L. H. Weinstein, J. F. Mancini, and P. van Leuken. 1973. Effects of hydrogen fluoride on plant- pathogen interactions. Internat. Clean Air Congress, Dusseldorf.

Mejstrik, V. 1978. Influence of sulfur dioxide on the growth of some fungus species. Zbl. Bakt. I1 Abt. 133: 464-467.

Miller, Paul R., and Joe R. McBride 1975. Effects of air pollutants on forests. In Responses of plants to air pollution. J.-Brian Mudd and T. T. Kozlowski, eds. p. 192- 235. Academic Press, New York.

Miller, Paul, R. and M. J. Elderman. 1977. Photochemical oxidant air pollution effects on a mixed conifer ecosystem. Ecological Research Series EPA 60013-77-104.

Oertli, J. J. 1958. Effect of salinity on susceptibility of sunflower plants to smog. Soil Sci. 87:249- 251.

Ormrod, D. P. 1977. Cadmium and nickel effects on growth and ozone sensitivity of pea. Water, Air and Soil Pollut. 8:263-270.

Saunders, P. J. W. 1971. & Ecology of Leaf Surface Microorganisms, pp. 81-89, T. F. Preece and C. H. Dickinson. Academic Press, London.

Scheffer, T. C., and G. G. Hedgcock. 1955. Injury to northwestern forest trees by sulfur dioxide from smelters. U.S. Forest Serv. Tech. Bull. 1117, 1-49.

Scheutte, L. R. 1971. Response of the primary infection process of Erysiphe graminis f. sp. hordei to ozone. Ph.D. Thesis, Univ. Utah, Salt Lake City, 71 p.

Shriver, D. S. 1974. Effects of simulated rain acidified with sulfuric acid on host-parasite interactions. Ph.D. Thesis, N. Carolina State, Raleigh, N.C.

Taylor, 0. C. 1974. Air pollution effects influenced by plant-environmental interaction. Amer. Chem. Soc. Sympt. Ser. 3:l-7.

Treshow, M. 1970. Environment and plant response. 422 p. McGraw-Hill Co., New York.

Treshow, M. 1975. Interactions of Air Pollutants and Plant Disease. InResponses of plants to air pollution. J. Brian Mudd and T. T. Kozlowski, eds. p. 307-334. Academic Press, New York.

Wainwright, M. 1978. Sulphur-oxidizing microorganisms on vegetation and in soils exposed to atmospheric pollution. Environ. Pollut. 17:167- 174.

Weidensaul, T. C. and S. L. Darling. 1979. Effects of ozone and sulfur dioxide on the host-pathogen relationship of Scotch pine and Scirrhia acicola. Phytopathol. 69:939-941.

Weinstein, L. H., D. C. McCune, A. L. Aluisio and P. van Leuken. 1975. The effect of sulphur dioxide on the incidence and severity of bean rust and early blight of tomato. Environ. Pollut. 9:145-155.

Studies on Relationship Between Air Pollutants and Microorganisms in

Japan1

Kiyoshi ~ a n a k a ~

Abstract: A review of the literature on the interaction of air pollutants with parasitic and epiphytic microorganisms is presented with a brief outline of air pollution problems in Japan. Some fungi such as Cercospora sequoiae, Pucciniastrum styracinum, Puccinia kusanoi, Melampsora coleosporioides, Trichoroma matsutake, and some epiphytic bacteria disappeared in the areas affected by air pollutants, and Rhizosphaera kalkhoffii increased its activity due to SO2 in the air.

Fungi, bacteria, viruses and nematodes, as well as insects are all responsible for bringing a certain species of higher plants into equilibrium with its environment (Treshow 1968). The effect of air pollutants on population trends of various microorganisms, therefore, is extremely important in all ecological systems. Further, air pollutants may affect plant disease development in different ways. Pathogenicity may be influenced through a direct effect of the pollutants on the parasite, or the effects may be indirect through pollution-induced changes in physiology of the host plant eagle 1973).

Prior to 19601s, the interaction of microorganisms with pollutants in the air had received limited attention in Japan. But during the past decades, a series of experiments has been conducted in order to explain the effect of air pollution on dis-ease development, and only recently, some attempts have been made to understand the change of populations of microorganisms for use as biological indicators of air pollution.

From the beginning of recognition of the significant and sometimes devastating effects of air pollutants on vegetation, plant pathologists have been

presented at the Symposium on Effects of Air Pollutants on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, California, U.S.A.

2~orest Pathologist , Kansai Branch, Forestry and Forest Products Research Institute, Momoyama, Fushimi, Kyoto 612 Japan.

confused with the similarities between the symptoms of many types of pollution damage and those of in- fectious diseases sometimes leading to incorrect diagnoses. Fortunately, each of the common air pollutants produces a characteristic injury pattern, and the sensitivity of many species differs sufficiently for the trained eye to determine the caus- ative agent dams and Salzbach 1961) .

This paper will review the literature on: 1)the modification of parasitism and the population changes of epiphytic microorganisms induced by air pollutants; 2) attempts to make reliable guides in distinguishing among symptoms caused by air pollutants and parasites, and those occasionally produced by saprophyfcic fungi. These subjects are considered in conjunction with a brief outline of air pollution effects on forest ecosystems in Japan

SULFUR DIOXIDE

In Japan, towards the end of 19th century, air pollution was reported to be harmful to forests around ore smelters that emitted large amounts of SO2. Plume behavior resulted in pollutants dispersion in the surrounding area, killing all the vegetation (mainly Cryptomeria japonica D.Don and Pinus densiflora Sieb. et Zucc.) and causing erosion of topsoils following the death of the plants (Doi 1919). The concentration of SO2 of the smoke was reported to be 1 ppm at 1 mile from a large ore smelter located in Ashio, Tochigi Prefecture, and occasionally reached as high as 8 to 10 ppm at the ground level (Doi 1919 ) .

Raising the height of stacks in order to reduce the concentration of SO at the ground level was

2the first and primitive control measure, new technology involves the installation of sulfur recovery devices. In 1915, one ore smelter in Hitachi, Ibaraki Prefecture, built a new stack on a hill rising about 350 m above sea level; the stack was nearly 170 m high, so that the smoke was discharged at an elevation of approximately 520 m. Although smelter smoke is released from high stacks, it tends to diffuse rather slowly, and the SO., there-fore, reaches the ground in harmful concentrations even after a considerable length of time and distance. Observations made three years after the replacement of stacks revealed the fact that the severity of damage in the area near to the smelter was markedly reduced,while the total damaged area increased as large as 24,000 ha ( ~ o i 1919).

The reduction of the concentration of S O in the area in the vicinity of the ore smelter on account of the change of stack height was good enough to resume the seedling production of Cryptomeria Japonica in nurseries. Kaburagi (1930) was im- pressed with the absence of a needle blight of Cryptomeria ,japonica caused by Cercospora sequoiae Ell. et Ev. in the nurseries located in the recovered area close to the higher stack. The needle blight is one of the most destructive diseases in forest nurseries producing Cryptomeria seedlings, and has spread rapidly throughout Japan except Ho- kkaido. The causal fungus was introduced from North America in the end of 19th century, and Iba- raki Prefecture including the ore smelter is considered to be the epicenter of the introduced disease (Ito 1976). Kaburagi (1930) suggested that a strong correlation existed between SO in the air 2and the absence of the disease. This is believed to be the first report on the effect of air pollution on diseases caused by parasites in Japan. Ka- buragi's observation is strongly supported by the following hypotheses that: 1)SO

? might act direct-

ly upon the fungus on the surfaces of host plants; and 2) the reduction of disease severity resulted in a decrease of inoculum for new infection.

Some of the acute type of damage by the emissions from smelters still continues in areas near to sources. In the 19601s, widespread SO, air pollution damage to ornamental trees had become apparent to the public; this increase was due to urbanization and industrialization. The one most apparent episode in and around Tokyo was the stunting and death of a large number of Zelkova serrata Mak., widely used as shade trees throughout Japan (yambe 1973).

With a considerable increase in public awareness of the chronic type of pollution in many parts, automatic SO 2 recorders were set up by the national and the prefectural agencies to determine the concentrations, frequency, and the duration of atmospheric SO exposures. The number of measuring locations $ad increased from the beginning at the 15 strategic locations in 1965 to as many as 1473 locations in 1979, forming an extensive sampling system for SO2 (The Japanese Environmental Agency

The analysis of air provides a framework of knowledge, and a foundation for developing air quality management strategies, and for prompting the enactment of the Clean Air Act in 1967, and its amendments made in 1970.

Figure 1.Mean value of annual concentrations at 15 strategic locations.

Figure 1 shows annual changes in average concentrations of SO

2 at 15 strategic locations between

1965 and 1977, the concentration increased until 1967, and then declined gradually. The decline has proved the continuing effectiveness of regulation of air pollution sources by the national and the prefectural governments based on the act.

During the summers in the middle of 19601s, the worst average concentrations of SO 2 were experienced. In this period, an unrecorded needle blight of Japanese red pine, Pinus densiflora, occurred throughout the normal range of that species, predominantly in central Japan. Up to that time the disease had been little known and of little concern to forest pathologists. A specific fungus dominantly found on blighted needles was investigated by Kobayashi (1967), and he identified it as Rhizo- sphaera kalkhoffii Bubak which had been known as a causal fungus of a needle blight of spruce and fir in northern Europe and North America.

The results of inoculation experiments to Japa- nese red pine seedlings proved that the pathogenicity of the causal fungus was considerably weak for pines, and the disease would scarcely occur if pines grew under normal conditions anak aka and Chi- ba 1971). The unusual incidence of the disease occurring in the early s m e r of 1.965 might be related to abnormal weather conditions--extremely little rain fell in early spring followed by heavy rain in May (Chiba and Tanaka 1968). Although the disease has not occurred so widely as in 1965, severe damage has been observed in the vicinity of ore smelters or industrial areas. In addition, Japanese red pine is highly sensitive to S O (Ino- ue 1973), and the distinction between the needle blight symptoms caused by the disease and those caused by SO is exceedingly difficult (Tanaka 1975, Tanita 1976)? Theref ore exhaustive experiments were conducted to examine the relationship of SO,,

c-with disease development.

A t o t a l of 163 two-year-old seedlings of Japan- ese red pine were exposed t o 2.0 ppm SO

2 f o r 1,2,3, and 4 hours i n a fumigation chamber before o r a f t e r inoculation i n t h e middle of Ju ly , with a water suspension of conidia of t h e fungus produced on PDA p la t e s .

Damage was more severe i n t he treatment combin-ing t h e fumigation with inoculation, especial ly inoculat ion before fumigation, compared with those i n t h e treatment of fumigation without inoculation. Numerous pycnidia of t h e fungus were produced i n l a rge l e s ions on needles t r ea t ed by fumigation a f t e r inoculat ion a s well a s fumigation f o r longer duration before inoculat ion, no obvious change i n t he appearance of needles was detected on t h e seed- l i ngs inoculated with t h e fungus without fumigation. Symptoms produced on t h e SO t r ea t ed needles, name-

2l y , l a rge les ions with numerous pycnidia, were i den t i ca l t o symptoms of t h e needle 'blight occur-r ing i n t h e f i e l d ( ~ h i b aand Tanaka 1968).

Most pine seedlings displayed acute symptoms of in jury following exposure t o 2.0 ppm SO f o r 2 hours. The SO concentration used i n this study

2 was several times higher than t h a t found i n t h e ambient a i r . It was necessary t o elucidate t he re la t ionship between SO

2 and disease development a t

lower concentrations because such conditions a r e frequently encountered i n r u r a l and fo re s t regions. Therefore, three-year- o ld seedlings of Japanese red pine were exposed f o r 2 weeks i n chambers t o 0.2 ppm SO t h e l e v e l of SO i s l i k e l y t o be found

2i n t h e ambient a i r (Tanaka 1576a).

In t h i s experiment, spec ia l emphasis was placed on t h e e f f ec t of SO fumigation a f t e r inoculation i n comparison with $he treatment before inoculation. The t r ea t ed needles with SO2 fumigation a f t e r inocu- l a t i o n were more severely affected by the fungus, compared with those fumigated by SO gas before inoculat ion. This r e s u l t i s consis tent with findings of t h e 2.0 ppm SO

2 fumigation (Chiba and Tana-

ka 1968). S O in jury appeared t o f a c i l i t a t e t he spread and reproduction of t h e fungus within tis-sues of needles r a the r than t o increase t h e i n i t i a l r a t e of in fec t ion by t h e fungus.

To fu r the r examine these findings from a r t i f i - c i a l SO exposure of seedlings i n chambers, f i e l d

2experiments were planned and conducted during the summers of 1972 and 1973 by using a t ransplant ing method anak aka e t a l . 1974a) and a f i l t e r e d a i r method (Tanaka e t a l . 1974b) i n Hiroshima Prefec- t u r e . In t h e t ransplan t ing study, two experimental p lo t s were establ ished. One was i n Fukuyama c i t y close t o a l a rge s t e e l re f inery . Especially i n t h i s a rea , d i s t i n c t SO damage markings on t h e needles of Japanese reg pine were v i s ib l e . The other was i n a r u r a l a rea i n Miyoshi c i t y . It was loca ted about 60 km north of a highly indus t r ia l ized area along the Seto Inland Sea including Fukuyama c i t y . I n t h e r u r a l a rea , t h e disease caused by Rhizosphaera ka lkhoff i i had not been noted i n recent years . A t o t a l of 900 pot ted seedlings of Japanese red pine used i n t h e t ransplant ing study were cultivated, previously i n t h e nurseries i n t he

r u r a l area i n Miyoshi c i t y . Seedlings were divided in to 12 groups as shown i n f igure 2 according t o t he combination of t ransplant ing and inoculation.

SO concentrations of both areas were determined2by means of t h e lead peroxide method. Needles were analyzed f o r sulfate-S and f o r total-S dry bas is i n order t o determine the accumulation of su l fu r i n t h e needles. Fol ia r symptoms were r a t ed from 0 t o 5 , according t o t h e degree of injury,and t h e average of these individual indexes provides t h e disease sever i ty f o r each group.

After being t ransported from t h e r u r a l a rea t o t h e indus t r ia l ized area, several seedlings exhib- i t e d t yp i ca l symptoms and signs of t he disease, while others remaining i n t h e r u r a l a rea displayed no evidence of in jury , even though they received the conidial spraying of t h e causal fungus ( f i gu re 2 ) .

In t he experiment using a f i l t e r e d a i r method, an experimental p lo t was establ ished i n an a rea i n Mihara c i t y close t o a powdered-coal-burning power p lan t . In t h i s a rea , a l a rge number of nee-d ie bl ighted Japanese red pines were found, and they displayed gradual reduction i n shoot and wood growth. The previous year 's annual mean contents of su l fu r compounds i n the a i r was 1.04 mg SO3 1100 cm2 PbO2 per day.

Plants were grown i n p l a s t i c covered chambers. One chamber ( 2 x 4 ~ 2 m ) was equipped with carbon f i l - t e r s and blowers, and t h e control o r ambient a i r chamber was provided with blowers. The a i r passed through each chamber a t a r a t e of about one a i r change / min. SO2 concentrations of t h e ambient a i r were determined by means of an automatic re-corder, and SO concentrations i n chambers were 2measured, by t h e lead peroxide method.

The experimental design was s imi la r t o t h e t ransplant ing experiment i n Fukuyama and Miyoshi, t h a t i s , a t o t a l of 300 seedlings were divided i n t o 12 groups according t o t h e combination of exposure t o SO2 and inoculation of t h e causal fungus, then seed- l i ngs were placed i n chambers t o determine whether some protect ion from infec t ion could be obtained when the a i r drawn i n t o t he chamber was f i l t e r e d . There was a la rge reduction i n t h e sever i ty of t h e disease i n t h e f i l t e r e d a i r compared with t h a t of t he disease i n t h e ambient a i r . These findings by f i e l d s tudies furnished t h e evidence t h a t SO2 i n t he a i r was responsible f o r t h e development of t h e disease. The su l fu r content espec ia l ly sulfate-S i n t h e needles of t h e t r e e s exposed t o SO2 was s ig-n i f i can t ly grea te r than t h a t of untreated needles both i n t h e t ransplant ing and t h e f i l t e r ed -a i r ex-periments.

An increasing i n disease:severity may.be expected when a i r po l lu tan ts weaken t r e e s , making them more susceptible t o infec t ion by weak paras i tes , o r re-duced vigor t o a degree t h a t p lan ts become predisposed t o a t tack by f acu l t a t i ve pa ra s i t e s , such as Rhizosphaera ka lkhoff i i , and Botryt is cinerea Pers. ( ~ a n n i n ge t a1. 1970) . Conversely, Linzon (1958)

--- 4

On July 18, 1970, Zelkova serrata trees in a

i! 2j,6;/(U 2sp jCO

0-0-0-0-

0 0

J A S D J A S D J A S D

5.11

transportat ion inoculation

PJ A S J T !

J : Jun 20

A:Aug 1

S: Sep 13

JASDJ A S D J- J-0

Figure 2. Effect of SO2 on the development of needle blight of pine caused by Rhizosphaera kalkhoffii

found that smelter emissions decreased the incidence of Cronartium ribicola C.J.Fis.,and there are additional reports that aggressive or obligate parasites, such as Microsphaera alphitoides Griff. et Maubl. (~och 1935) , and Melampsorella cerastii Wint , Peridermium coloradense Arth. et Kern, and some species of Melampsora and Gynmosporangium (Scheffer and Hedgcock 1955) were less abundant in areas adjacent to smelter zones or to industrialized areas. ltol found a similar case in Tokyo that a" close relationship existed between the increase of distance from the metropolitan area and the increase of the incidence of willow rust disease caused by Melampsora coleosporioides Dietel and a leaf rust disease of Styrax japonicum Sieb. et Zucc. caused by Pucciniastrum styracinum Hirat. The complex of air pollutants was brought about by urbanization and industrialization, typical of the mixture of pollutants occurring in and around Tokyo, but SO2 was considered to be principally responsible for reducing the abundance of these fungi.

OXIDANTS MAINLY OZONE ( 0 )

Beginning in the 19701s, changes from solid to liquid and gas fuels, and especially increasing use of motor vehicles, have caused a reduction of the SO type of urban pollution and an increase of "ozone" pollution.

Personal communication from S. Ito, University of Tokyo, January 15, 1980.

yard of a senior high school located in Suginami Ward in Tokyo showed unusual shedding of their leaves, and strawberry leaves showed white spots clearly indicating the effects of oxidants. In addition to the damage to plants, 45 students of the school were hospitalized for treatment of irri- tated eyes, sore throats and difficulty in breath- ing. From this evidence, the Metropolitan Govern- ment issued the statement that the damage to humans and vegetation was caused by photochemical air pollution (The Tokyo Metropolitan Government 1971), and this was thought to be the first episode of 'Los Angeles type smog" in Japan. But as a result of later investigations it was found that there were differences between Tokyo and Los Angeles air pollution, since SO2 concentration and humidity in Tokyo were much higher than in Los Angeles; furthermore, it was confirmed that there was formation of sulfuric acid in the air (The Tokyo Metro- politan Government 1971). These findings suggest that the complex of photochemical oxidants and sulfuric acid might exert a far greater influence on humans and vegetation than any other alone at that time.

In the latter half of 19701s, with continuous increasing industrialization and transportation, every major city in Japan has experienced an increasing in photochemical oxidants even though there was a slow but steady decline in the concen-. tration of SO2, in the ambient air (figure 1).

Photochemical oxidants , mainly ozone (0 ) ,con-tinue to cause the defoliation of broad leaf trees. Especially, in the Kanto district, at the center of Tokyo, unusual defoliation of Zelkova serrata still continues, since it is sensitive to both SO 2(Inoue 1973) and 0 (Kadota and Ohta 1972). While, in the Kansai dist?ict,at the center of Osaka, there is a high incidence of defoliation of poplar trees in the early summer in the parks, the gardens or the yards of schools throughout the district.

In addition to the measuring system of SO 2throughout the country, a number of automatic oxidant recorders were also set up by the national and the prefectural agencies, but there is still a shortage of satisfactory apparatus for monitoring the low ambient concentrations. To make up for the shortage of an instrumented system, plants have been used extensively as bioindicators of air pollution. The use of bioinaicators has long been accepted, since damage to green plants is usually one of the first signs that air pollution is becoming a serious problem e err^ 1964); their usefulness in this capacity is based primarily on the sensitivity of selected plant species and varieties for specific pollutants (Heck 1966).

Many clones, species and varieties of poplars were selected as bioindicators because of their high sensitivity to oxidants and their wide distribution, especially in the Kansai district. They also have enounnous advantages in that they are fast growing, easy to propagate vegetatively by

cutt ings, and are uniformely sens i t ive t o oxidant injury.

Despite these advantages, poplars are frequently plagued by various kinds of insects and diseases t h a t degrade the usefulness of poplar clones as pollut ion indicators . For example, in te rpre ta t ion of t he response t o oxidants i s made d i f f i c u l t by l ea f diseases caused by Marssonina brunnea (El1.et Ev.) Magnus, Septot inia podophyllina Mhetz. and Melampsora lar ici-poplul ina Kleb. A r e l i ab l e guide t o d is t inguish among symptoms caused by a i r pollu- t a n t s , insec ts , and diseases has been developed and published (Tanaka 1975 ) . The defol iat ion caused by Marssonina brunnea i s one of the most serious diseases. It occurs wherever poplars grow, and i s not r e s t r i c t e d t o urban regions, but frequently occurs with sever i ty i n urban areas. The disease develops t i n y spots with l i g h t margins about 1mm i n diameter over the e n t i r e surface of t he l ea f . These superf ic ia l spots a r e not so d i f f i c u l t t o d is t inguish from the symptoms caused by ozone by plant pathologists with a t ra ined eye, but many people who want t o use poplars as indicators a re confused with the s imi lar symptoms produced by ozone and the disease (Tanaka 1975). In addition, t he disease causes premature lower l e a f abscission,and the de- fo l i a t i on progresses upward toward the t i p s of the shoots from the l a t e spring through the summer months. The unsightly appearance of affected t r ee s discourages poplars ' use as indicators of oxidants.

A number of invest igators suspected t h a t abscis- s ion was not due d i r ec t ly t o t he pathogen but re-su l ted instead from increased r a t e s of ethylene production from the infected p lants (Abeles 19731, fur ther , ozone-induced abscission of leaves of varying maturity was closely correlated with r a t e s of ethylene production ( ~ b e l e s 1973). From these

reasons, Tanaka (1976~)) hypothesized t h a t increased r a t e s of ethylene production caused by the syner- g i s t i c e f f ec t s of t he infect ion of t he fungus and ozone was responsible fo r t he incidence of the disease i n t he urban area.

Fortunately, there i s s t r i k ing v a r i a b i l i t y i n suscept ib i l i ty of poplar clones t o the fungus and ozone. Clones were selected tha t a re sens i t ive t o ozone and r e s i s t an t t o t he disease. The se lec t ion of fers one of t he best means of increasing t h e usa- b i l i t y of poplar clones as ozone indicators (Tanaka 1977a). Table 1presents t he re la t ionship between ozone sens i t i v i ty and disease resis tance of poplar clones (Tanaka 1 9 ~ ~ a ) . The data of resis tance of poplar clones t o t he disease are based on the three years' observation made i n Osaka using 38 clones of young rooted cut t ings t an aka 1 9 7 ~ a ) , and t h e data of ozone sens i t i v i ty of them are based on the re-s u l t s from the exposure experiments with 0.15 ppm ozone fo r 40 hours i n chambers conducted by Enoki (1977).

Populus maximowiczii cv. O J 115 and cv. OJP 1, P.m a x i m o ~ i ~ c h o c a r ~ acv. OP 41, P .maxino-& z i i x 2.nigra pl&tierens cv.0P 52, and P.nigra i t a l i c a x ~.maximowiczii,cv.Kamabuchiare promising clones for ozone indicators because they are sensi-t i v e t o ozone and r e s i s t an t t o the disease ( tab le 1).

Yambe (1978) a l so attempted t o f ind a possible usefulness of the change of microbial f l o r a on bamboo leaves as indicators fo r a i r pol lut ion. He found t h a t Puccinia kusanoi Die te l and epiphytic bac ter ia on the l ea f surfaces of bamboo decreased sharply i n number i n the urbanized and indus t r ia l - ized areas.

Table 1. Relationship between clonal suscep t ib i l i t y of poplars t o 0 and t o Marssonina brunnea. 3

Suscept ib i l i ty t o Marssonina brunnea I Highly Resistant Moderately Susceptible Highlyres i s t an t r e s i s t an t susce'otible

r e s i s t a n t

1R e s i s t a n t ( R ) HE 2, OP 26, NR 19, I 45/51Serotina MR 32

Moderately r e s i s t an t

Gerlica I 262I 154, I 214

I 72/51, Kamabuchi, Highly O J 115, OJP 1, OJP 2, I 77/51,

I 488susceptible(ss^ OJP 3, OJP 4, OJP 5 , . OP 4 1

I

OTHE8 POLLUTANTS pa ra s i t ey Rhizosphaera ka lkhoff i i (Chiba and Tana- ka 1968).

In addit ion t o SO and oxidants, s ign i f icant and 2

sometimes devastating e f f ec t s of other a i r pollu- t a n t s have long been recognized i n Japan. Fluoride compounds have a long h i s to ry as pol lutants i n t h e v i c in i ty of ceramic industry, and more recent ly, plant in jury resu l ted from f luor ides has gradually increased because of t h e expansion of indus t r ies such a s aluminum re f ine r i e s m d f e r t i l i z e r manu- factures ( ~ a t u u r a and Kokubu 1972). Chlorine (Ta- naka 1977b), ethylene, acidic dust from stacks, and a lka l ine dust from cement k i l n s (Inoue 1972a and 1972b) have a l so been recognized as agents of dm- age t o vegetat iony but t he damaged areas a r e re la - t i v e l y r e s t r i c t e d because most of them a re emitted from point sources o r by accidental s p i l l s .

The in te rac t ion of these minor pol lu tan ts with fungi and bac ter ia has received only minor at ten- t i o n , but Inoue (1972a and 1972b) found t h a t t he number of f r u i t i n g bodies of Tricholoma matsutake Singer was s ign i f i can t ly reduced i n t he heavily dusted fo re s t s i n t h e v i c i n i t y of cement works compared t o l e s s severely dusted o r non-dusted por- t i ons of fo re s t s . According t o t he r e s u l t s of hand-dusted experiments,he concluded t h a t t h e alka- l i n e so lu t ion from t h e dust severely decreased the formation of t h e f r u i t i n g bodiesy and reduced the development of t h e fungus colonies.

CONCLUSIONS

The in te rac t ion of po l lu tan ts with pa ra s i t i c and epiphytic microorganisms has received l imi ted a t - t en t ion i n Japan. The ex is t ing reports a r e only associated with t r e e s and bamboos and no report with annual p lan ts was found i n a search of avai l- able l i t e r a t u r e .

Some pol lu tan ts a r e d i r e c t l y tox ic t o microorganisms on the leaf surface. They might possibly impair t h e i r growth o r reproductiony and change the population and community composition of mCcroorgan- i s m s on the host p lan ts , s ince t he s ens i t i ve spe- c i e s t o a i r po l lu tan ts would be gradually replaced by more t o l e r an t species (Treshow 1968). Especial- l y y aggressive o r ob l iga te paras i tes such a s Cerco- spora sequoiae (Kaburagi 1930), Pucciniastrum m- racinum and Melampsora coleosporioides (1 to1)~ and Puccinia kusanoi (Yambe 1978) a r e l e s s abundant i n polluted a r easy and the disease sever i ty they induce? is sharply reduced.

On t h e other hand, i n fo re s t stands under inf luence of i n d u s t r i a l and urban a i r pol lut ion, some f o l i a r pathogens counted by pathologists i n t h e group of so-called ' f acu l t a t i ve pa ra s i t e ' a r e of grea te r importance because a i r po l lu tan ts i n ju re l ea f t i s s u e and predispose t r e e s t o a t tack by f acu l t a t i ve paras i tes . A close cor re la t ion has been found between SO i n t h e a i r and a high inc i - dence of needle bl ighz of pine caused by a weak

' Personal communication from S. It0 University of Tokyo, January 1980.

Although plant in jury caused by spec i f ic pollu- t a n t s such a s SOpy 0 and f luor ides has gradually been abated by enginJering improvements o r by-products recovery, chronic in jury caused by a complex of urban a i r po l lu tan ts has assumed addi t iona l importance a s urbanization and t h e use of motor ve- h i c l e s have increased.

Injury t o green p lan ts i s usually one of t h e f i r s t s igns t h a t a i r po l lu t ion is becoming a ser ious problem, and sever i ty of spec i f ic diseases i n pol- l u t ed areas must be regarded a s an addi t iona l expression of unbalanced na tura l conditions. These spec i f ic diseases and t h e change of composition of l ea f surface microorganisms provide a ids f o r moni- to r ing a i r po l lu tan tsy espec ia l ly i f they a r e sen- s i t i v e t o very low concentration of a i r po l lu tan ts . These diseases and microorganisms should be considered a useful supplement t o t h e more expensive techniques and instruments used f o r t h e i den t i f i - cat ion of chronic a i r po l lu tan t e f f ec t s .

Acknowledgments: I thank D r . Paul R. Mi l le r , Pac i f ic Southwest Forest and Range Experiment Sta- t ion , U.S. Dep. Agr icaY f o r h i s c r i t i c a l readings of the manuscript.

L1T.ERATURE CITED

Adms $D ,F . and C . W. Sulzbach . 1961. Nitrogen deficiency and f luor ide suscepti-

b i l i t y of bean seedlings. Science 133: 1425-1426.

Abeles ,F.B. 1973. Ethylene i n plant biology. 302pp. New York.

Berry,C.R. 1964. Eastern white pine, a t o o l t o de tec t a i r

pol lut ion. Southern Lumberman 209(2609):164,166

Chiba,O. and K.Tanaka. 1968. The e f f ec t of sulphur dioxide on t h e develop-

ment of pine needle b l igh t caused by Rhizosph- aera ka lkhoff i i Bubk. I. J.Jap.For.Soc. 50: - 135-139

Doi ,T. 1919. orest st p ro tec t ion) . b09pp. Tokyo.

Enoki ,M . 1977. (Clonal suscep t ib i l i t y of poplars t o ozone). Ann. ~ e p . 1976. ,Osaka Agr . Centr . : 117-119.

Heagle,A.S. 1973. Interact ions between a i r po l lu tan ts and

plant paras i tes . Ann.Rev.Phytopath. 11:365-388.

Heck,W.W. 1.966. The use of p lan ts a s indicators of a i r pol-

lu t ion . A i r Water Poll.1nt.Nat.J. 10:gg-111.

Inoue,I. lg72a. Studies on the influence of smoke-dust from a cement plant on the vegetation of pine forests, especially on Tricholoma matsutake. I. Trans .Mycol. SOC. Jap. 13: 196-214.

Inoue,I. 1972b. Ditto 11. M:215-288.

Inoue T . 1973. (Tree injury caused by sulfur dioxide). Plant Protection 27:8-12.

It0 ,K. 1976. Blight and canker of Cryptomeria Japonica D.Don. caused by Cercospora se uoiae Ellis et Everhart. Ann.Phytopath. Soc .-%-2:234-236.Jap

Japanese Environmental Agency. 1979. (White paper on environment for 1979) . 2163pp. Tokyo.

Kaburagi,T. 1930. (Smoke damage to plants). Iwanami Lectures for Bioloa. 1-39.

Kobayashi >T. 1967. Critical revision on the genera Rhizosphaera Mangin et Harriot and Rhizophoma Petrak et Sydow, a little-known fungus group associated with needle disease of conifers. Bul1.Gov.For.Exp. Sta. 204 :91-112,

Kadota,M. and K.Ohta. 1972. Ozone injury to some Japanese woody plant species in summer. J. Jap. For. Soc . 54:226-229.

K6ch9G. 1935. Eichenmehltau und Rauchgasschaden. Z.Pf-lanzenkr. 45:44-45.

Linzon,S.N. 1958. The influence of smelter fumes on the growth of white pine in the Sudbury region. Can.Dep. Agr.Publ. ,Ontario Dep. Lands Forests. 45pp.

Matuura,S. and N.Kokubu. 1972. Fluorine, its distribution and role in nature. 150pp. Tokyo.

Scheffer,T.C. and G.G.Hedgcock, 19.55. Injury to northern forest trees by sulfur dioxide from smelters. UDSA,For.Serv.Tech.Bull. 1117:49pp.

Tanaka,K. 1975. The similarity between symptoms caused by air pollutants, insects, and diseases. Agr. and Hort. 5O:Preface.

Tanaka ,K. 1976~~.m e effect of low-level SO fumigation on the development of needle bligh$ of pine caused by Rhizosphaera kalkhoffii. Anr1.Rep.1975.~ m e range of tolerance of biological indicators to pollutants:5-9.

Tanaka,K. 1976b. Tree diseases in air polluted areas and their usability as indicators. a : 51-56.

Tanaka,K. 1977a. Pest problems in the use of poplar clones as indicator plants for photochemical oxidnats . Trans. 88th Mtg .Jap.For. Soc . :419-421.

Tanaka,K. 1977b. Accidental chlorine gas damage to ornamental woody plants. w:4l5-4l7.

TanakayK.,T.Okada and K.Hako. 1974a. Effect of SO2 on the development of needle blight of pine caused by Rhizosphaera kalkhoffii, Transplanting experiment. Trans. 86th Mtg .Jap .For. Soc.:290-292.

Tanaka,K.,M.KuwakiBT.Okada and K.Hako. 1974b. A plastic covered chamber with activated carbon filters. =:211-213.

Tanaka,K. and 0.Chiba. 1971. On a needle blight ~f pine caused by Rhizo- sphaera kalkhoffii--Life historyy physiological characteristics and pathogenicity of the causal fungus. J. Jap .For, Soc . 53: 279-286.

Tanita, S . 1976. Histological effects of air pollutants and pathogens on Pinus thunbergii. Trans 88th Mtg. Jap .For. Soc . :373-37k.

Tokyo Metropolitan Government. 1971. ~okyo fights pollution. 2 6 7 ~ ~ . Tokyo.

Treshow, M. 1968. m e impact of air pollutants on plant populations. Phytopathology 58 :1108-1113.

Ymbe, Y. 1973. decline of trees in Tokyo. Bul1.Gov.For. Exp.Sta. 257:lOl-107.

Ymbe, Y. 1978. Decline of trees and microbial florae as the index of pollution in some urban areas. Bull. For.& For.Prod.Res.1nst. 301:llg-129.

Sensitivity of Lichens to Air Pollution with an Emphasis on Oxidant Air

Pollutants1

^ Thomas H. Mash I11 and Lorene L. Sigal

Abstract: The hypothesis that lichens are sensitive indicators of air pollution is now well established for oxidants, sulfur dioxide, hydrogen fluoride and trace elements. From field studies differential sensitivity of different lichen species around pollution sources is evident. Laboratory studies with the particular air pollutant generally confirm the same degree of differential sensitivity.

LICHENS AND THEIR ECOLOGY

Lichens, which strictly speaking are called lichenized fungi, are composite plants represent- ing a symbiotic union of algae and fungi to form morphological entities unlike either component (Ahmadjian 1967, Hale 1967). Although a few species survive in aquatic environments, most are found in terrestrial habitats, occurring on soil, rocks and as epiphytes on other plants. All lichens are perennial plants with life spans varying from a few decades to reportedly thousands of years (Weber and Andrews 1973). Essentially all lichens are autotrophs because of the photosynthetic activity of the algae. Metabolic activity in general is limited to period's when the lichens are moist, a condition which varies in concert with atmospheric moisture conditions as lichens have no roots by which moisture might be absorbed from the substrate. Thus lichens are prominent examples of poikilohydric plants (Larcher 1973) which also include bryophytes and some lower vascular plants, such as desert species of Selaginella and ferns. Because of moisture


'~r. Nash is associate professor of botany, Dept. of Botany, Arizona State University, Tempe, Arizona 85281 USA; Dr. Sigal is a research scientist, Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box X, Oak Ridge,. Tennessee 37830 U.S.A.

constraints on photosynthetic activity, primary productivity assignable to lichens is generally small compared to higher plants. Nevertheless lichens may be important in ecosystem functioning. For example, lichens are generally recognized as important pioneer plants of xeric successional sequences because of their role in biologically controlled weathering (Syers and Iskandar 1973). In addition, lichens are important in mineral cycling, not only because of their ability to alter precipitation chemistry (Ianq and others 19761, but also from the ability of blue-green algae containing lichens to fix atmospheric nitrogen. Den son (.1973) has estimated that lichens are respons ble for 50 percent of the nitrogen fixed in the Douglas-fir forests of the Pacific Northwest.

Lichens are morphologically divided into 3 major growth forms: crustose, foliose and fruticose. Crustose species are generally small, tightly attached to (or imbedded in) their substrate and poorly differentiated. Foliose species are generally larger, loosely attached to their substrate and stratified into several distinct layers. In contrast to the basically 2-dimensional foliose species, fruticose s~ecies are strongly 3-dimensional and grow out from their substrate. Most fruti'cose species are also differentiated into distinct layers. Of these morphological forms fruticose species are generally considered to be the most sensitive to air pollution (Fenton 1964), a fact which may be related to the high surface- to-volume ratio of this form.

LICHENS IN RELATION TO AIR POLLUTION

Different species of lichens are well-known to

be differentially sensitive to air pollution (Nash 1976). A few species actually grow better in urban environments where air pollution levels are high in contrast to their performance in rural areas. Most species, however, exhibit varying degrees of sensitivity to air pollution and some are more sensitive than higher plants. Thus by documenting variations in abundance and species richness of lichen communities, it is frequently possible to identify poliution sources and to document the magnitude of the air pollution probla, Patterns within lichen communities may be attributable to many environmental factors other than air pollution, of course, and consequently it is extremely important that studies be made within a multivariate context, including both pollution factors and non-pollution factors.

The fact that lichens are differentially sensitive to air pollution is based on a series of field observations and laboratory experiments extending back over the past 130 years. Grindon (1859) and Nylander (1867) noted that lichens were disappearing from city centers. Later Arnold (1892) documented that lichens transplanted from rural areas to the center of Munich were not able to survive. Subsequently this "city effect" has been reported for many cities in Europe and North America (Hawksworth 1971). By air pollution most workers of the 1800's generally meant coal soot and related particulates. However, over the past decades a number of invisible gases, such as sulfur dioxide and ozone, have been identified as the major causes of air pollutant injury to plants. Experiments with these air pollutants over the past two decades have also demonstrated differential sensitivity among different lichen species. In general, the sensitivity patterns demonstrated in the laboratory have remarkably Corresponded to the patterns observed in the field around pollution sources. Perhaps the strongest evidence supporting the contention that lichens are sensitive to air pollution comes from studies documenting lichen recovery following pollution abatement. For example, Seaward (19761 has documented that Lecanora muralis fairly rapidly reinvaded an urban complex in southern England following amelioration of air pollution in the area.

In the following sections specific evidence related to various types of air pollutants w211 be reviewed.

Oxidant Air Pollutants

Oxidant air pollutants, including ozone and peroxyacetplnitrate (PANI, are a group of gases characteristic of the oxidizing atmospheres found in the Los Angeles type smog (Pitts and Finlayson 1975). Although the effects of these compounds have been studied extensively with higher plants (National Academy of Sciences 19771, relatively few studies have been conducted with lichens. Probably the only field study in which lichens have been shown to be sensitive to oxidants is that of Sigal and Nash (1980) for the southern

Californian mountains* The study was centered in the San Bernardino Mountains, utilizing the sites mployed by the University of California (Riverside and Davis] ecosystem study of air pollutant effects in contrast to sites in a control region, Cuyamaca Rancho State Park in southern San Diego County. In addition, there was an excellent historical record of the lichens of the San ~ernardinos based on collections made by H. E. Hasse at the turn of the century. Of the 91 foliose and fruticose lichen species reported by Hasse (1913) in his lichen flora of southern California, only 34 species were found during three sunnners of study throughout southern California. Thus there has been a significant reduction in the number of species present. To obtain quantitative data on lichen variation, both conifers (Ab2es concolor, Pinus ponderosa, Pinus jeffreyi and Pseudotsuqa macrocarpa) and California black oak (Quercus kelloggii) were sampled for lichen cover at breast height.

In the case of conifers Hasse (1913) reported the presence of 16 foliose and fruticose lichen species in the San Bernardino Mountains. In our recent study [Sigal and Nash 19801 only 8 of these species were found in the San Bernardino Mountains and 4 of these were only present in vestigial quantities. In contrast, at sites to the north and to the south K'uyamacasl 15 of the 16 species reported by Hasse were found. Thus in the San Bernardinos which lie adjacent to the Los Angeles Bash, there has been a SO percent decline in species richness of lkhens on conifers. Of the species which do occur in the San Bernardinos only two (Letharia Vulpina and Hypogymnia entero- momha) occur commonly. The latter species, although it is common, is definitely showing signs of deterioration (Table 1) when randomly selected thalli from the San Bernardinos are compared with a similar set from the Cuyamacas. The San Ber- nardino population has a much higher percentage

Table 1-- Morphological characteristics of recent collections of Kypogymnia enteromorpha from the San Bernardinos and the Cuyamacas.

Percent Bleaching

Forest

38 59 41

Percent Convoluted

Forest

38 38 47 15

of bleached and convoluted thalli. In addition, there was a decrease of approximately 50 percent in overall thallus dimensions in the San Bernardino population and a decrease in fertility of 42

percent. Thus there are marked trends between the San Bernardinos and the Cuyamacas of reduced species richness and species vitality in the former area. Within the San Bernardinos themselves, significant variation exists. Below approximately 150 ppm-h oxidant dosage, cover of both Letharia and Hypogymnia is normal in comparison with other areas. At higher dosages of up to 285 ppm-h lichens are almost completely eliminated from conifers.

Comparisons of trends of lichens occurring on black oak between the San Bernardinos and Cuyamacas also indicated that a deterioration was occurring in the San Bernardinos, but the trends were not as dramatic as in the case of lichens occurring on conifers. No direct comparison with the Hasse material was possible because Hasse did not note the species of oak in his collections. From our sampling 39 species of lichens were found on black oak in the Cuyamacas and 30 specie3 in the San Bernardinos. Fourteen of the species found in the Cuyamacas were not found in the San Bernardinos whereas three species were found exclusively in

13.5 12.1 . ucc

7.6 COO. 12.9

10.2 12.1

TOTAL % COVER ALL L ICHENS

15.7

BF.

Bp CA GVC 4 230.8 186.7 DWA T2 145.8

184.9. ,,cc i33.2

COO. 134.7

175.0

OXIDANT DOSE ESTIMATES 183.2 BF.

the San Bernardinos. Among the 20 species which occurred in common there was a general shift from high frequency in the Cuyamacas to relatively low frequency in the San Bernardinos. In the case of cover of the 6 most common species, no significant difference was observed between the two mountain ranges except for Collema nigrescens, the only nitrogen fixing lichen in the groupi which was completely absent from the San Bernardinos. Fur- ther analysis revealed that Parmelia subolivacea, the most common lichen, was a successional species. Because older trees occurred in the Cuyamacas, a significantly higher value for this species in the Cuyamacas was predictable. Further evidence supporting the hypothesis that the dominant species was in fact respondhg to oxidants was obtained by running ordinations (princiwal component analysis) of the sites within the San Bernardinos and relating the observed variation in species composition to oxidant dose estimates and other environmental variables (fig. 1). An initial ordination (not shown) included all sites sampled within the San Bernardinos. It exhibited a small cluster of low cover sites which occurred at the

I % COVER

PARMELIA SUBOLIVACEA 8.2 BF

D

SAN BERNARDINO NAT'L FOREST STUDY -SITE LOCATIONS

Fig. 1--Principal component analysis ordination of 10 sites in the San Bernardino Moun- tains using cover data for the 5 most important lichen species occurring on Quercus kelloggii. Eighty percent of the variation is explained by axis one (the abscissa). Figure 1A shows the positioning of the sites on the ordination plot with respect to total cover of all lichens; figure lBf the same ordination but with cover values for =- melia subolivacea; figure lC, the same ordination, but with oxidant dose estimates (ppm-h); figure IDf the geographic location of the sites within San Bernardino Nation- al Forest.

highest elevations where summer fog is infrequently observed. Consequently these sites and one other site on the desert side of the San Bernardinos were excluded from the subsequent analysis. The 10 sites plotted in figure 1 are thus homogeneous with respect to altitude and position along the Los Angeles side of the San Bernardinos (fig. 1Dl. In the subsequent ordination (fig. lA, 1B and lC), 80 percent of the variation is explained by axis 1 (the horizontal axis). From figures 1A and 1B it is clear that the primary source of variation is the percent cover of all lichens, which in turn corresponds closely to the percent cover of E. subolivacea. Furthermore, there is an inverse relationship between percent cover of E. s-olivacea (fig. 1 ~ ) and oxidant dose estimate (1C). This inverse relationship was substantiated by running a Speaxman rank correlation between the two variables. The test was significant with an alpha value of 0.007. For the other 4 species no relationship between oxidant dose estimates and cover values were found. Thus some species have been completely eliminated from the San Bernardinos, other species have probably declined in abundance and a few species are apparently unaffected.

Preliminary ozone fumigations have shown differential responses in photosynthesis reduction between Pamelia sulcata and Hypogymnia enteromorpha with the former species exhibiting greater sensitivity (Nash and Siyal 19791. The Parmelia, which grows on black oak, is absent from the San Bernardinos whereas the Hypogymnia is present, but is exhibiting signs of deterioration. For these species, at least, the pattern of sensitivity observed in the field and the laboratory are com- plementary. A similar pattern of response for the two species was observed after fumigations with PAN (Sigal and Taylor L979). Further stud2es with both ozone and PAN should be run, but the current evidence strongly supports the assertion that oxidants are a major cause of the decline of the lichen flora in the San Bernardino Mountains.

Sulfur Dioxide

Sulfur dioxide is released into the atmosphere by combustion reactions involving products containing the ubiquitous element sulfur, such as coal and oil. It has long been recognized as a phytotoxic agent in general (Daines 1968). Lichens are well known to be sensitive to sulfur dioxide (Nieboer and others 19761. Most of the field studies in northern Europe and North America have involved sites where sulfur dioxide was a major factor (Hawksworth 1971). One of the classic studies by Rao and LeBlanc (1967) demonstrated a severe decline in lichen abundance along a 70+ km transect NNE of Wawa, Ontario where an iron sintering plant is present. Because there is essentially no human development in the affected region, air pollution, and particularly sulfur dioxide, is undoubtedly a major cause of the decline in the reqionts lichens. Other studies have shown that lichens accumulate sulfur (Olkkonen and Takala 1975, Laaksovirta and Olkkonen 1977) in situations where the presumed

source of sulfur is sulfur dioxide. The gas readily dissolves in water forming a sulfite or bisulfite solution depending on the pH. As a consequence acidification of the substrate frequently occurs, as has been shown in Stockholm where Skye (19681 found that urban tree bark had a pH of more than two units less than corresponding trees from the country-side. Acidification strongly affects the ability of lichens to survive, in part because sulfur dioxide is much more toxic at lower pH's (Tuerk and Wirth 1975). Gilbert (1965 and 1970) has clearly demonstrated the ability of lichens to penetrate into central Newcastle on basic substrates when they are absent from acidic ones. In the laboratory studies, photosynthetic decline in response to short term sulfur dioxide exposures as low as 0.2 ppm have been demonstrated (Tuerk and others 19741. In aqueous experiments with reputedly lower concentrations, effects have also been documented Baddeley and others 1973, Puckett and others 19741.. In addition to reduction of photosynthesis, bleaching of lichen thalli may occur due to phaeophytinisat2on of the chlorophyll~ (Nash 1973, Puckett and others 19731. More recently potassium efflux from lichens exposed to sulfur dioxide has been shown to be the most sensitive criterion of response (Tomassini and others 1977). Alteration of membrane permeability may thus be an immediate response to sulfur dioxide exposure. Subsequently it is suggested (Nieboer and other 1976, Puckett and others 1974) that interference in electron flow in photosystem I and I1 will occur'and that proteins will be affected through sulfur dioxide$ ability to cleave disul- phide linkages. Thus there is very strong evidence from both field and laboratory studies that lichens are sensitive to sulfur dioxide.

Hydrogen Fluoride

Hydrogen fluoride is extremely volatile and is released into the atmosphere during aluminum and rare earth metal refining, fertilizer production and glass and ceramic manufacturiny. Patterns of lichen decline are well demonstrated around aluminum factories (Martin and Dacquard 1968, Gilbert 1971, LeBlanc and others 1972, Horntredt 1975) and around a titanbn plant (Nash 19711 and around a phosphate plant (Takala and others 19781. In these areas fluoride accumulat~on by the lithens has been demonstrated with decline in the lichen cornunities being associated with elevated fluo-ride levels. Transplants of healthy lichens into the impoverished zones resulted in fluoride accumulation and subsequent death of the transplants. Gilbert suggested that the critical fluoride level lay between 20 and 50 ppm and Nash independently suggested that the value lay between 30 and 80 ppm. Schoenbeck (1969) found that his transplants died near a fluoride source, but that new transplants survived well for several months following cessa- tion of the fluoride emissions. In a laboratory study with exposure to approximately 5 ppb fluoride over a 9-day period Nash (1971) found that lichens accumulated 84-115 ppm fluoride in contrast to control levels of 14-25 ppm and that the fumigated samples developed chlorotic and necrotic symptoms

similar to the injury observed in the field transplants. Thus fluoride as the probable cause of the injury was confirmed.

Trace Elements

Lichens have a well demonstrated ability to accumulate elements from dilute aqpeous solutions (Nieboer and others 1977)# a fact probably related to their apparent dependence on atmospheric sources for mineral nutrition. As a consequence of this ability to retain elements# the study of trace element concentrations in lichens is frequently useful in demonstrating "fallout" patterns of particulates and aerosols. For exampleI mercury is found in elevated concentrations near a chlor- alkali works in Finland (Lodenius and LaaJcsovirta 1979); lead is elevated in lichens adjacent to highways (Laaksovirta and other 1976# Lawrey and Hale 1979); and a number of elements are present in high concentrations in citiesI such as Tel Aviv (Garty and others 1977) and Sendalp Japan (Saeki and others l977lI near the nickel complex at SudburyI Ontario (Tomassini and others 1976) I near a coal-fired power plant (Gough and Erdman 1977) and in coal mine ecosystems of Ohio (Lawrey and Rudolph 19751. In none of these cases is toxicity of the accumulated elements demonstrated. Toler-ance to high concentrations of elements may occur if the elements are relatively insoluble and are localized extracellularly. For exampleI Noeske and others (1970) showed that iron and copper were encrusted on the surface of lichens which grew on metal rich substrates in the Harz Moun- tains of Germany. FurthermoreI Garty and others (1979) have shown that particulates in Tel-Aviv are incorporated extracellularly within the lichen thallus.

In contrast to the above studies "trace" elements do occasionally occur in toxic concentrations. Lawrey and Hale a9791 have shown accumulation of approximately 1000 ppm lead in a lichen growing near an expressway in the vicinity of WashingtonI D.C. They demonstrated that.lead accumulation is correlated with reduction in growth of the speciesI but they have neither demonstrated experimentally that lead was the cause of the reduced growth nor demonstrated that other factors associated with automobile emissions were unimportant. Probably the most convincing study documenting trace element toxicity is that of Nash (1975) around a zinc smelting complex in eastern Pennsylvania. In the vicinity of the smelting complexI lichen species richness was reduced to 7 in contrast to the 77 species found in a control area (Nash 1972). The zone of lichen impoverishment extended for a distance of 15 km W and 10 km E of the smelting complex (fig- 2). Although detectable and potentially toxic levels of sulfur dioxide were found adjacent to the smeltersI the distribution of elevated levels of sulfur dioxide did not extend as far as the lichen impoverishment zone extended- The relative unirnprtance of sulfur dioxide was further documented by the lack of acidification of the bark of oak trees and by the fact that the

2oE 10 0 low DISTANCE FROM EAST SMELTER (kml

Fig. 2 ~ T h e distribution of the lichen-impoverished zone (Nash 1972) at Palmerton# PennsylvaniaI in relation to the zones of modified forest (Jordan 1975)# to detectable levels of ambient sulfur dioxide (Nash l975lI and to elevated levels of cadmium and zinc in surface soils (Buchauer 1973).

company had installed and subsequently continuously used an acid plant at the time that zinc sulfide ores were initially processed. In contrast# metal concentrations in the soil duff were as high as 1351000 ppm zinc and 1750 ppm cadmium at a site adjacent to the smelting complex Duchauer 1973). The concentration of zinc and cadmium decreased exponentially with distance from the smelters until background concentrations were found at 20 to 25 km E and 16 km W of the smelters (fig. 21. Physiological studies demonstrated that zinc and cadmium were toxic to the lichens when concentrations reached 300-500 ppm in the thallus. Since zinc was present in concentrations 100 times that of cadmium and since zinc is approximately as toxic as cadmiumI zinc was inferred to be the most important pollutant. Â¶i points beyond the li'chen impoverishment zone zinc concentrations ranged from 20-200 ppm and cadmium from 1-30 ppmI where both sets of values were demonstra5ly non-toxic.

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Buchauer* M. 1973. Contamination of soi 1 and vegetation

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related t o a i r pollution from industry in Odds* western Norway. Meddr. Norsk Ins t ' Skogforsk. 31: 581-604.

Jordan, M. J . 1975. Effects of zinc smelter emissions and

f i r e on a chestnut-oak woodland. Ecology 56: 78-91.

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and M. Kessel . -;.-a1 iza t ion of heavy metals and other

elements accumulated in the lichen thal lus . New Phytol . 82: 159-168.

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i n the Tyne Valley. & Ecology and the indus t r ia l society. G . T. Goodman* ed. p. 35-47. Oxford Univ. Press* London.

1976. Further s tudies on the e f f ec t of sulphur dioxide on 1 ichens and bryophytes. New Phytol . 69: 605-627,

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, 1 ichens. The Lichenologist 5: 26-32.

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on the element content of parme: i a chloro- chroa. The Bryologist 80: 492-501.

Grindon* L. H. 1859. The Manchester Flora. London.

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Arnold Ltd. London.

Hassey tt. E. 1913. The lichen f l o r a of southern Califor-

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lichen and bark adjacent t o a highway in southern Finland. ~ n v i r o n .POI 1u i . li : 247-255.

Lang* G. E a Y W. A. Reiners and R . K. Heier. 1976. Potential a l t e r a t ion of prec ip i ta t ion

chemi s t r y by epiphytic 1 ichens. Oecologia (Berl .) 25: 229-241.

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Lawrey* J . D. and M. E. Hale* J r . 1979. Lichen growth responses t o s t r e s s in-

duced by automobi 1e exhaust pol 1 ution. Science 204: 423-424.

and E. D. Rudolph. 1975. Lichen accumulation of some heavv met-

a l s from ac id ic surface substrates of" coal mine ecosystems in southeastern Ohio. Ohio J . Sci. 75: 113-117.

LeBlanc. F.* D. N. Rao and G. Comeau. 1972. Indices of atmospheric puri ty and f luor-

ide pollution pat tern in Arviday Quebec. Can. J . Bat. 50: 991-998.

Lodeniusy M. and K. Laaksovirta. 1979. Mercury content of Hypogymnia physodes

and pine needles affected by a chlor-a1 ka1 i works a t Kuusankoski, SE Finland. Ann. Bot. Fennici 16: 7-10.

Martin, J. F. and F. Jacquard. 1968. Inf luences des fumges d'usines sur l a

d i s t r i b u t i o n des l ichens dans l a va l l ge de l a Romanche (IS&-e) . P o l l u t Atmos. 19: 95-99.

Nash, T. H., I 1 1 1971. Lichen s e n s i t i v i t y t o hydrogen f l u o r -

ide. Bu l l . Torrey Bot. Club 98: 103-106.

7 2 . S i m p l i f i c a t i o n o f the Blue Mountain l i chen communities near a z inc factory. The Bryo log is t 75: 315-324.

1973. S e n s i t i v i t y o f l ichens t o s u l f u r dioxide. The Bryol og i s t 76 : 333-339.

1975. In f luence o f e f f l uen t s from a z inc fac- t o r y on 1 ichens. Ecol . Monogr. 45: 183-198.

1976. Lichens as ind ica to rs o f a i r po l l u t i on . Die Naturwissenschaften 63: 364-367.

and L. L. S igal . 1979. Gross photosynthet ic response o f 1 i ch -

ens t o short- term ozone fumigations. The Bryol og i s t 82 : 280-285.

National Academy o f Sciences. 1977. Ozone and other photochemical oxidants.

719 p. Washington, D. C.

Nieboer, E., D. H. S. Richarson, K. J. Puckett and F. D. Tomassini.

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1977. Ecological and physiochemical aspects o f the accumulation o f heavy metals and su l - phur i n l ichens. I n Proc. In tern. Conf. on heavy metals i n theEnv i ron . (Oct. 27-31, 1975, Toronto, Ontar io) , p. 331-352.

Noeske, O., A. Laeuchli, 0. L. Lange, G. H. Vieweg and H. Z iegler .

1970. Konzentrat i on und Lokal is i erung von Schwermetall en i n Flechten der Erzschl acken- halden des Harzes. Dtsch. Bot. Ges. Neue Folge 4: 67-79.

Nylander, W. 1867. Les l ichens du j a r d i n du Luxembourg.

Bu l l . Soc. Bot Fr. 13: 364-372.

Olkkonen, H. and K. Takala. 1975. Total sulphur content o f an ep iphy t i c

l i chen as an index o f a i r p o l l u t i o n and the usefulness o f the x-ray fluorescence method i n sulphur determinations. Ann. Bot. Fen-n i c i 12: 131-134.

P i t t s , J. N. and B. J. Finlayson. 1975. Mechanisms o f photochemical a i r pol l u -

t i on . Angew. Chem. 14: 1-15.

Puckett, K. J., E. Nieboer, W. P. F lo ra and D. H. S. Richardson.

1973. Sulphur d ix ide : i t s e f f e c t on photosyn- t h e t i c C f i x a t i o n i n l ichens and suggested mechanisms o f phy to tox ic i t y . New Phytol . 72: 141-154.

D. H. S. Richardson, W. P. F lora and E. T'I eboer.

1974. Photosynthetic 14c f i x a t i o n by the 1ichen Umbi 1 i c a r i a muhl enbergi i (Ach. ) Tuck. fo l low ing shor t exposures t o aqueous sulphur dioxide. New Phytol . 73: 1183-1192.

Rao, D. N. and F. LeBlanc. 1967. In f luence o f an i r o n s i n t e r i n g p l a n t on

cor t i co lous epiphytes i n Wawa, Ontario. The Bryo log is t 70: 141-157.

Saeki, M., K. Kunii, T. Seki, K. Sugiyama, T. Suzuki and S. Shishido.

1977. Metal burden o f urban l ichens. Environ. Res. 13: 256-266.

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ischen Workung von Luftverunreiningungen durch t r ansp lan t i e r t e Flechten. Staub 29: 14-18.

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urban environment. I n D. H. Brown, D. L. Hawksworth and R. ~ . B a i l e y , eds. Lichenology: progress and problems. p. 323-357. Academic Press, Inc., London.

Sigal, L. L. and T. H. Nash 111. 1980. Lichen communities o f southern Cal i f o r -

n i a mountains: an ecological survey r e l a t i v e t o oxidant a i r po l l u t i on . Ecol. Monog. 50: ( i n press).

and 0. C. Taylor. 1 9 7 9 . Pre l iminary s tudies o f the gross photo-

syn the t i c response o f l ichens t o peroxyacetyl- n i t r a t e fumigations. The B ry l og i s t 82: 564-

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geogr. Suec. 52: 1-114.

- 9

Syers, J. K. and I.K. Iskandar. Tuerk, R. and V. Wirth. 1973. Pedogenetic s ign i f i cance of 1ichens. 1975. The pH dependence o f SOn damage t o -I n The l ichens. V. Ahmadjian and M. E. Hale, l ichens. Oecologia (Be r l i n ) 19: 285-291. eds. p. 225-248. Academic Press, Inc., New York. -9 -and 0. L. Lange.

1974. CO,,~Gaswechsel-Untersuchunqen z u r SOo- Takala, K., P. Kauranen and H. 01 kkonen. ~ e s i s t e d z von Flechten. o e c o l o ~ i a (Ber l .?

1978. F luor ine content o f two 1 ichen species 15: 33-64. i n t he v i c i n i t y o f a f e r t i l i z e r factory . Ann. Bot. Fennici 15: 158-166. Webber, P. J. and J. T. Andrews.

1973. Lichenometry : a commentary. Arct. Tomassini, F. D., P. Lavoie, K. J. Puckett, E. Alp. Res. 5 (4 ) : 295-302.

Nieboer and D. H. S. Richardson. 1977. The e f f e c t o f t ime o f exposure t o sulphur d iox ide on potassium loss from and photosynthesis i n t he l ichen, Cladina rang i f e r i na (L.) Harm. New Phytol . 79: 147-155.

K. J. Puckett, E. Nieboer, D. H. S. Rich- Acknowledgments : This research was supported ardson and B. Grace. by the U.S. Nat ional Science Foundation

1976. Determinat ion of copper, i ron, n icke l , grants DEB-7610244 and DEB-7921953. and sulphur by X-ray fluorescence i n l i chens from the Mackenzi e Val 1 ey, Northwest T e r r i -t o r i es , and the Sudbury D i s t r i c t , Ontario. Can. J. Bot. 54: 1591-1603.

Influence of Air Pollution on Population Dynamics of Forest Insects and on

Tree Mortality1

Donald L. Dahlsten and David L. ~owney2

Abstract: Weakened trees are often predisposed to injury or death by insects, and in forest ecosystems particularly by bark beetles. In the San Bernardino National Forest the interaction between photochemical oxidant weakened ponderosa pine and the western pine beetle (WPB) was examined in detail. The major results from this study suggest that oxidant damaged trees attacked by WPB produce about the same total brood with lower initial attacks compared to healthier trees. This higher productivity trend is most evident in generation 1 trees Generation 2 trees, both damaged and healthy, are under much greater moisture stress and produce much less WPB brood than generation 1 trees regardless of oxidant damage.

The implication of these results is that in stands with a higher proportion of damaged trees, a given population of WPB could kill more trees and increase at a greater rate than in a stand with a lower proportion of damaged trees. Simulation modelling with these results and other factors that affect ponderosa pine mortality should provide a basis for predicting long term effects of air pollution on the WPB population and pine mortality.

Most of the work on air pollution damage has There have been some studies on the direct focused on direct injury to the plant and effects of air pollution on insects. Feir (1978) Kozlowski (1980) gives a good review of the im- studied the effects of air pollutants on insect pact of air pollution on forest ecosystems. By growth and reproduction and Hillmann and Benton comparison, little has been done on the indirect (1972) looked at the reactions of honey bees to effects such as the predisposing of plants to sulfur dioxide. insects or pathogens. Watt (1969) speculated on the effects of air pollution on population fluc- Bromenshenk (1976, 1978) has studied the tuations of insects and Heagle (1973) reviewed effects of coal-fired power plant emissions on a the interaction between air pollutants and plant variety of insects. In another study, Gilbert parasites. More recently the occurrence of (1971) looked at the indirect effects of air diseases and insect pests of trees in air pollution on several bark inhabiting insects. polluted regions of North America has been Air pollution may be the cause for the scarcity recorded (Dominik 1978). of all orders of insects in New Jersey (Muller

1971).

The effects of insects in pine stands influ- 'presented at the Symposium on Effects of Air enced by air pollution, particularly xylophagous

Pollutants on Mediterranean and Temperate Forest insects, have been studied (Sierpinski 1972, Ecosystems, June 22-27, 1980, Riverside, 1977). In California on the San Bernardino California, U.S.A. Mountains, ponderosa pine shown to have advanced

professor of Entomology and Statistician in symptoms of oxidant injury were most frequently

Entomological Sciences, respectively, University infested and killed by western pine beetle

of California, Berkeley, Calif. (Dendrocbonias'-brevicabis), and mountain pine

- -

beetle (2. ponderosae) (Stark et al. , 1968). The purpose of this study was to look a little closer at the interaction between the western pine beetle and oxidant affected ponderosa pine, to see what effect diseased trees would have on the dynamics of bark beetle populations and to look for differences between beetle population parameters in diseased and healthy ponderosa pine.

MATERIALS AND METHODS

Field Procedures

Beginning about the first week in July, the San Bernardino mountain areas with substantial ponderosa pine stands were searched for first generation western pine beetle attacked trees. These areas are generally on the southern side of the mountains at about 1500-1800 m elevation, and are areas where high oxidant air pollution levels occur. Second generation trees were located in mid-August to raid-September, depending on the timing of the first generation. Trees under attack were detected by pitch tubes or frags in bark crevices. Attacked trees were checked with an axe at the base to see which species were attacking and to check the staqe. Trees with mixed brood (2. ponderosae and 2. brevicomis) and trees with strip attacks (one side only) were relatively uncommon and were not selected for this study. Trees with spp. in the tops were selected, but sampling for western pine beetle was stopped at the base of infestation of the

z. Each suitable tree located was used in the study until the required number were found (12 per generation in 1973 and 1974, 6 per generation in 1975 and 1976). In the time period allowed for sampling the initial WPB stages there was no practical way to locate all the attacked trees in the area and thenpick a random subsample for the study.

Sampling

Prior to sampling, the major tree characteristics were recorded: location, height, DBH, height of first green branch, and estimated tree damage due to air pollution. The air pollution damage was rated by rating upper and lower crown needle retention, needle condition, needle length, and branch mortality. Needle condition and retention were difficult to rate on the sample trees because in many cases, fading and needle loss due to the bark beetle attacks had begun. For 1973 only one needle length rating was made for the entire tree, so the needle length rating for the other years was combined to be consistent in the analysis ( in nearly all cases the upper and lower crown needle length was the same).

Samples for all procedures except where noted later were taken at 1.5 meter intervals over the length of the western pine beetle infestation. Two 88 cm2" discs taken on opposite sides of the tree at 1.5 meter intervals gave the desired level of precision.

The samples were taken from the tree using a modified ortable 4.5 kg gas powered drill D l P r e c o n Multiple Control, Ridgewood, New Jersey). A standard circular hole saw with an 11 can diameter blade was used in the chuck of the drill. This saw cuts an area of approximately 88 cm2.

At each sample height the circumference was measured, then the two discs were cut. With the egg discs it was desirable to take a portion of the xylem with each disc to protect the galleries. After a disc was removed it was examined by the climber for insects, which were identified and called down to the notetaker.

During the last larval sample emergence cartons were placed on the trees at each sample height. These cartons were not removed until well after brood emergence.

Laboratory Procedures

Once the samples had been returned to Berkeley, they were placed in cool storage until analyzed. X-rayed samples were placed into rearing immediately after the radiographs were taken. Basically there were four laboratory analysis procedures for sample discs.

Egg Disc Analysis

To determine egg mortality discs were taken at 3.0 meter intervals approximately two to three weeks after the mass attack period. Sampling at every 3.0 m interval gave 4 or more heights for each tree. Egg discs were taken only once, at the time of the first larval sample. This avoids an additional climbing of the sample tree, assures that maximum egg hatch has occurred and mortality can still be determined.

If xylem tissues still remained on the disc it was carefully removed so that the galleries in the phloem tissue were not disturbed. Gallery length was measured with a metric map reader and all attacks were recorded. Each disc was then examined with a dissection scope (10-20x) along the length of all the adult galleries. Each egg niche was evaluated asempty or as containing a viable egg or nonviable egg in addition to re- cording larval eclosion. The difference between the total number of egg niches recorded and the total number of larvae hatched was calculated as egg mortality.

X-ray Analysis

The first samples to be x-rayed were taken concurrently with the egg discs (egg discs are destroyed during analysis so they can not be placed into rearing). For generation one, an additional x-ray sample was taken late in the brood development period, usually in mid to late July. For the second generation, x-ray samples were removed on two later occasions: once in mid-September to October to check for early emergence of brood and

adult re-emergence, and finally in the following spring (March to April) after brood development was nearly complete, but before spring emergence.

The discs to be x-rayed were tkken from cold storage as soon as possible and removed from the plastic bags. The average bark thickness of each disc was measured with a metric caliper and the percentage woodpeckering on each disc was recorded. The two 88 cm2 discs from each height were placed on one sheet of 8" x 10" Industrial ~odak@AA-2 film and exposed with a picker@ radiograph machine. The samples were then re- bagged and transported to a large storage shed f a rearing (see below).

X-rays were interpreted for western pine beetle, live and dead parent adults, brood adults, pupae, and larvae, parasitoids, predators and miscellaneous. The miscellaneous category included buprestid and cerambycid larvae, weevils, *,and unknowns, of which there were many judging from the rearing of these discs. A light table was used for interpretation and all inclusions were marked with a grease pencil by the interpreter, counted and then erased. A second interpreter then repeated the process, thereby reducing error and bias. The x-rays from each tree were then stored in envelopes as a permanent record.

Laboratory Rearing

Each x-rayed disc was placed in a 1/2 gallon ice cream carton with a small 2 or 3 dram glass vial pushed through the lid. Since the insects in the discs are positively phototropic at least in the adult stage, and since very few beetles or other insects bore through the sides of the cartons, this was a suitable rearing procedure. The cartons were stored in racks in a large unheated warehouse where Berkeley's mild, cool climate provided an ideal rearing environment.

The emerging insects were collected from the vials three to five times per week. Most of the specimens could be identified with a lox hand lens and then recorded on a data sheet by collection date. Only the parasitoids and the western pine beetle were sexed. All specimens have been identified by taxonomic experts and specimens were sent for verification regularly; the collection is updated as necessary. Approximately 130 different insects were recorded. In this paper, only WPB, 4 predators (Enoclerus lecontei, Temnochila chlorodia, Aulonium longum, Medetera aldrichii) and 4 parasites (Roptrocerus XJ&-phagorum, Dinotiscus burkei, Eurytoma conica, Coeloides sp. nr. brunneri) are considered.

Sample discs were kept in rearing for nine months and at the end of this period the cartons were examined for any remaining insects; the discs were then discarded. The gallery length and number of attacks were recorded for each disc prior to discarding. Attack holes can be dis- tinguished from emergence holea as they are

oblique to the surface of the bark and often have pitch as a remnant of a pitch tube.

Field Emergence Cartons

As an additional check on emergence, a procedure for rearing in situ on the sample trees was also used.

One quart squat ice cream cartons that cover 88 cm2 of bark were painted silver on the outside and prepared with a screened ventilation hole. Stikem specialawas placed on the inside of the cartons to discourage insects from boring out or from going back into the bark. A groove was cut in the bark with the sampling saw into which the lip of the carton was placed; a nail was driven through the bottom of the carton and into the tree to increase stability.

The cartons were placed on the tree at the time the last x-ray or brood sample was taken (to coincide with the pupal and/or callow adult stages of the brood) and were left in place for up to three months, until well after beetle emergence and the collection of all associated insects had taken place. The second generation cartons were nofc placed on the tree until early spring since cartons do not weather well and therefore cannot be left ort the trees for four to six months over winter. The cartons were split open and examined under the microscope and then discarded. The same insects that-were recorded for laboratory rearing were recorded for the sticky emergence carton.

RESULTS AND DISCUSSION

Attacked tree characteristics and variation by year and generation:

The tree heights of the 71 attacked trees sampled over the four year period varied from 13 to 44 meters, but most trees were in the 20-30 meter range (Fig. 1). Tree DBH, stem volume, and infested bark area varied more widely, but exhibited no significant trends with regard to year and generation. Western pine beetle attack and emergence density, however, both showed significant differences (P < -05) by generation. Year differences were not significant for these variables except for a lower attack density for generation one trees of 1976 compared to the generation one trees of the other three years.

Effect of tree oxidant damage on beetle population:

In order to determine if damage to the sample trees had an effect on the western pine beetle populations, the individual components of the damage score were analyzed with respect to beetle attack density. Each individual component of the score can be regarded as an interval level variable, so multiple regression techniques were used to determine their relationship to attack density. The technique used was a full screen analysis

/,* L : ,, ,, , -

1 2 1 2 1 2 1 274 75 74 75

GENERATION GENERATION

which calculated p2 values for all possible linear combinations of the score components, year, and beetle generation for the attack den-sity dependent variable. The results of this analysis indicated that only the needle length (NL) component (upper and lower crown combined) of the score was significant (P < -05) along with beetle generation. The effect of any other com-ponents was insignificant when added to the equa-tion containing NL and generation. Some of the other components which have been significant in other studies - needle retention and needle con-dition - probably were unreliable for these trees as they were examined in a partly faded condition some weeks after being mass attacked by bark beetles. In subsequent analyses the needle length (NL) was used to distinguish between trees highly affected by air pollution (NL=O) and less affected trees (NL=l). Table 1 gives mean values of the attack density and other western pine beetle variables for each generation and needle length category. In our sample of trees significantly fewer short NL trees were found in generation one (7 of 36) compared to generation two (16 of 35), but due to the practical limita-tions of our sample selection procedure, it is uncertain whether this difference holds true for the entire population of attacked trees;

The attack density was significantly higher for long NL trees compared to short NL trees for both generations, while generation two trees had lower attack densities than generation one re-gardless of ML.

Fig. 1. Western pine beetle attacked tree characteristics, attack density and emergence density by generation and year for 71 ponderosa pines in the San Bernardino National Forest, California. (dashed lines = mean + one standard deviation)

Most other generation one beetle variables were not significantly different between short aid long NL trees, except for eggs per attack and emerged brood per attack (Table 1). This prob-ably indicates that the attacking beetles for generation one were more productive when the trees had lower attack density and less compe-tition within the trees. The short NL generation 1 trees, with lower attack densities, had essen-tially equal numbers of eggs and emerging brood compared to the long NL trees.

The trend toward high productivity in the lower attack density, short NL trees for generation 1 was not evident for generation 2. The beetles in the short NL trees had essentially the same eggs/attack and emerged brood/attack as those in long NL trees (Table 1). Total eggs, hatched eggs, and late larval densities were all significantly lower in the lower attack density, short NL trees. Mortality proportions for each life stage sampled seemed relatively independent of NL although they were higher in generation 2 compared to generation 1.

Table I--Western pine beetle variable means by gen-eration and tree a: pollution injury(needle lerytH

Generation 1 Generation 2 Short Long Short Long

Injury: NL ML NL NL

No. of trees ~ t t a c k s / ~ ~ ~ Gallery length/^^^ Total eggs/~M2 Eggs/attack Hatched eggs/Dll

(1st instar larvae/~~2)

Egg mortality Late larvae/DM2

Larval mortality--early to late larvae (LM)

Emerged WPB (REAR)/Dd

Mortality-late larvae to emer-gence (REAR) (BPI)

Mortality-eggs to emergence (REAR)

Emerged brood per attack

*significant differences between NL

classes, P < .05.

Needle length was also used to compare differences in predator and parasite densities for each generation (Table 2). Predators included the 4 common species: Enoclerus lecontei, Temnochila chlorodia, Au1oniw.1 longum, and Medetera aldrichii. Parasites included Roptrocerus e-phagorum, Dinotiscus burkei, Eurytoma conica and -Coeloides sp. nr. brunneri. For generation 1, only emerged (REAR) predators/dm2 were significantly higher for the long NL trees. For generation 2, initial parasitized larvae/dm2 were higher for short NL trees, but late parasitized larvae/ dm2 were higher for long NL trees. A much larger increase in numbers of parasitized larvae occurred for the gen. 2, long NL trees. Increased woodpeckering, along with a higher final larval density for the long NL trees may explain the increased numbers of parasitized larvae. A similar proportion (about 1%) of initial larvae were parasitized in both cases.

Table 2--WPB predator and parasite means by generation and tree air pollution injury class (needle length).

Generation 1 Generation 2 Short Long Short Long

Injury: NL NL NL NL 2

No. trees 7 29 16 19 Initial pred./~~2 0.962 1.910 0.53 0.30 Initial para- 0.20 0.36 0.18* 0.08 sitized lar./DM

Late predators/~~2 1.83 2.75 0.80 0.84 Late parasitized 0.56 0.61 0.26* 0.48 larvae/~ll^

Emerged (REAR) 0.73* 1.50 0.25 0.27 predators/~~^

Eraer.(REAR) para/D~2 0.48 0.42 0.22 0.28 % area samples wood-0.1% peckered

0.8% 7.0% 11.0%

*Significant difference between means of smog injury classes, P < .05 .

Table 3--Ozone effects table: western pine beetle in ponderosa pine.

tree mort.

low long 4.0 3.9 consbat constant or de- or decreasing creasing

high short 2.4 3.7 increaskq increasing

Motes: (1) Effect depends on individual tree character-

istics. (2) Based on both generations combined and multi-

plying female adult attacks by two to account for males.

(3) Based on both generations combined. (4) Assuming constant no. of damaged pines/stand.

The consequences of bark beetle activity in an area are summarized in Table 3 and show that attack rates are lower on oxidant affected trees, but the output of brood is essentially the sane in healthy and diseased trees. Bark beetles, assuming no direct deleterious effects of air pollution,should increase in areas with high ozone damage and tree mortality will also increase in these areas. The possible interactions of air pollution, ponderosa pine, and western pine beetle and the effects on forest succession are shown in Table 4.

Table 4~Interaction table: air pollution, ponderosa pine, and western pine beetle.

Causes a change in VPB 1 Ponderosa Forest pop. pine mortal- succes- level ity caused sion

by WPB An increase In: air pollution + + + soil water ? ? ? foliar injury ++ + + soil nutrients ? ? ? mature tree growth ? ? ? root disease + + + forest succession - - 0 WPB pop. level 0 ++ + pine mort. caused by WPB ? 0 +

Key: 0 = unrelated or not possible + = moderate increase

++ = large increase - = a large decrease ? = unknown, needs more investigation

LITERATURE CITED

Kozlowski, T. T. 1980. Impacts of air pollution on forest ecosystems. BioScience 30:88-93.

Watt, K.E.F. 1969. Prospective effects of air pollution on insects. Can. Entomol. 101:1235-1238.

Heagle, A. S. 1973. Interactions between air pollutants and plant parasites. Annu. Rev. Phytopathol. 11: 365-388.

Dominik, J. 1978. Investigations of the occurrence of diseases and insect pests of North American trees in the regions of different degrees of air pollution caused by the industry. Final Report of Investigations covering the period of August 1, 1973-June 30, 1978. Warsaw: Sin., 1978. 91, 21 leaves: 111.

Feir, D. 1978. Effects of air pollutants on insect growth and reproduction. Physiologist 21:36.

Hillman, R. C., and A. W. Benton. 1972. Biological effects of air pollution on insects emphasizing the reactions of the honey bee, e m e l l i f e r a to sulfur dioxide. J. Elisha Mitchell Sci. SOC. 88:195.

Muller, J. 1971. Is air pollution responsible for melanism in Lepidoptera and for scarcity of all orders of insects in New Jersey, U.S.A. J. Res. Lepid. 10:189-190.

Gilbert, 0. L. 1971. Some indirect effects of air pollution on bark living invertebrates. J. Appl. Ecol. 8: 77-84.

Bro~~ienshenk,J. J. 1976. Biological impact of air pollution on insects. Ecol. Res. Ser. 600/3-76-013: 295-312.

Bromenshenk, J. J. 1978. Investigation of the impact of coal-fired power plant emissions upon insects: entomological studies at the zonal air pollution systems. Ecol. Res. Ser. 600/3-78-021:473-507.

Sierpinski, 2. 1972. The economic importance of secondary noxious insects of pine on territories with chronic influence of industrial air pollution. Mitt. Forstl. Bundes-Versuchsanst Wein. 97: 609-615.

Sierpinski, Z. 1977. Economic significance of noxious insects in pine stands under the permanent impact of the industrial air pollution. Slyvan. .64:59-71.

stark, R.W., P.R. Miller, F.W. Cobb, Jr., D.L. Wood, and J.R. Parmeter, Jr. 1968. Photochem- ical oxidant injury and bark beetle (Coleop- tera: Scolytidae) infestation of ponderosa pine. I. Incidence of bark beetle infestation in injured trees. Hilgardia 39:121-126.

Air Pollutants and Their Effects on Wildlife with Particular Reference to the House Wren (Delichon urbica)'

James R. Newman, P ~ . D . ~

Abstract : In ju ry and death t o w i l d l i f e from a i r emissions have been recorded s ince before the t u r n of the century. A i r po l lu t ion can d i r e c t l y a f f e c t w i l d l i f e ( i . e . , cause dea th ) , or can i n d i r e c t l y a f f e c t w i l d l i f e ( i . e . , cause h a b i t a t l o s s ) . A recent inves t iga t ion on the chronic and s u b l e t h a l e f f e c t s of a i r po l lu t ion on the house mart in (Delichon u rb ica ) has shown t h a t a i r v

emissions can s i g n i f i c a n t l y a f f e c t the nest ing ecology of t h i s spec ies .

INTRODUCTION emissions ( P r e l l 1936; Hais and Masek 1969). Eighty-five percent o f the w i l d l i f e inc iden t s

Since the end of the 19th cen tu ry , over have been recorded i n the l a s t 25 y e a r s . The 100 a i r p o l l u t i o n episodes have been repor ted inc rease i n the number o f w i l d l i f e inc iden t s involving i n j u r y and death t o animals (Newnan appears t o be due no t on ly t o an increase in a i r 1975, 1979). Although the major i ty o f the emissions but t o a b e t t e r understanding of a i r i n c i d e n t s involved domesticated animals, a number p o l l u t i o n e f f e c t s , broader communications, and a o f i n c i d e n t s have been repor ted f o r w i l d l i f e g r e a t e r i n t e r e s t i n repor t ing such problems. s i n c e the 1880's ( t a b l e 1 ) . Overal l , the few r e p o r t s involving w i l d l i f e appear t o be more a Table I-The number of reported a i r p o l l u t i o n func t ion o f economic b i a s t o repor t i n j u r y and i n c i d e n t s involving w i l d l i f e and af f ec ted groups dea th o f domestic animals than some innate (adapted Newman 1979) r e s i s t a n c e o f w i l d l i f e t o a i r p o l l u t i o n . For example, i n the e a r l y 1900's a r sen ic emissions from a smelter caused the i n j u r y and death o f Number of I s e v e r a l thousand c a t t l e and horses in r u r a l Wildl i fe Groups consumer Groups Montana arkin ins and Swain 1908). No mention was Period I n c i 1 Game \ one game IPrim. [secondary made o f i n j u r y o r death t o deer o r o ther w i l d l i f e den t s 1 1 p l e n t i f u l i n the a r e a , a 1 though deer and r a b b i t s a r e known t o be ve ry s e n s i t i v e to a r sen ic Before 1 1 1

1900

1900-1950

p r e s e n t e d a t t h e Symposium on E f f e c t s of Air P o l l u t a n t s on Mediterranean and Temperate Fores t 1951-1970

Ecosystems, June 22-27, 1980, Rivers ide , 1971 t o

C a l i f o r n i a , U.S.A. Present

^sen2ior Eco log i s t , P ro jec t Operations, Environmental Science and Engineering, Inc ., TOTAL P.O. Box ESE, Ga inesv i l l e , F lo r ida 32602.

Recent Federal l e g i s l a t i o n , namely the 1977 Clean A i r Act Amendments, now r e q u i r e formal c o n s i d e r a t i o n o f the e f f e c t s o f a i r emissions on w i l d l i f e and o the r components o f eco log ica l systems.

The purpose o f t h i s paper i s t o summarize some o f the known e f f e c t s o f a i r emissions on w i l d l i f e and present p re l iminary f i n d i n g s on the e c o l o g i c a l e f f e c t s o f a i r emissions on the house m a r t i n ( ~ e l i c h o n u r b i c a ) , an insec t ivorous b i r d . For t h i s paper , d i s c u s s i o n i s l imi ted t o t e r r e s t r i a l wild1 i f e and v e r t e b r a t e consumers . Previous speakers h e r e discussed the e f f e c t s on i n v e r t e b r a t e consumers.

GENERAL EFFECTS OF A I R EMISSIONS ON WILDLIFE

One of the e a r l i e s t w i l d l i f e inc iden t s (1887) involves t h e death of f a l low deer (Dama dama) from a r s e n i c emissions from a s i l v e r foundry i n Germany (Tendron, 1964). As e a r l y a s 1900 t h e Royal Soc ie ty of London was charged to i n v e s t i -g a t e t h e phenomenon of i n d u s t r i a l melanism. This i n c i d e n t i s recognized more f o r i t s demonstration o f "natura l" s e l e c t i o n than a s an environmental problem. Recently, g e n e t i c changes i n small mammals because of a i r p o l l u t i o n have been repor ted (Newman 1980).

One of t h e ' e a r l i e s t d e t a i l e d d e s c r i p t i o n s of t h e harmful e f f e c t s of a i r emissions on w i l d l i f e i s from Germany. Arsenic emissions were the cause o f widespread death of game animals i n the Tharandt f o r e s t of Germany i n 1936. S i x t y t o seventy percent of t h e red deer (Cervus e iephus ) , r o e dee r (Capreolus capreo lus ) , and wild r a b b i t s ( ~ r ~ c t o l a g u scun icu lus ) d ied. The deer exhibi ted d e f e c t i v e h a i r growth and a n t l e r formation, c i r r h o s i s of t h e l i v e r and spleen, and emaciation ( P r e l l 1936).

Adverse e f f e c t s of a i r emissions on w i l d l i f e have been repor ted from North America, Euro-pe, and Asia , and have included game and nongame animals; b i r d s and mammals; primary and secondary consumers; and he rb ivores , omnivores, and ca rn ivores ( t a b l e 1 ) . The e f f e c t s on w i l d l i f e have included d ie -o f f s and o the r population r e d u c t i o n s , phys io log ica l abnormal i t i e s , d i s e a s e , phys ica l i n j u r y , and bioaccumulation. The m a j o r i t y of w i l d l i f e i n c i d e n t s repor ted involve dee r and small b i r d s (~ewman 1979). These groups a r e not n e c e s s a r i l y more s e n s i t i v e but a r e more l i k e l y t o be monitored, e s p e c i a l l y dee r , which i s a widely managed game spec ies . The s t a t u s of smal l b i r d s i s not only of s c i e n t i f i c concern, bu t a l s o of more widespread publ ic i n t e r e s t .

Pathways of contamination by a i r emissions f o r w i l d l i f e a r e : i n h a l a t i o n , adsorp t ion , and i n g e s t i o n . Wellings (1970) repor ted the occurrence of pulmonary an th racos i s i n urban sparrows (Passe r domesticus) compared to r u r a l popu la t ions i n C a l i f o r n i a . One of t h e most s t a r t l i n g examples of contamination by i n h a l a t i o n involved the die-off of 200 t o 500 songbirds near

a B r i t i s h Columbia pulp m i l l which emitted high concen t ra t ions of H2S and o the r p o l l u t a n t s . The dead b i r d s showed i n t e r n a l hemorrhaging i n t h e lungs and l i v e r . 3

Adsorption of a i r emissions involves the adhesion of gases o r p a r t i c u l a t e s t o the e x t e r n a l s u r f a c e s o r e x t e r n a l membranes, e .g . , cornea of eyes. Light (1973) r e p o r t s a high incidence of b i i n d n e s s i n bighorn sheep (*canadensis) found i n mountain a r e a s of Ca l i fo rn ia with heavy oxidant l e v e l s . Oxidants a r e known eye i r r i t a n t s . I n v e s t i g a t o r s i n ~ z e c h o s l o v a k i a ~ have observed e a r l y aging of the cornea i n ha res ( ~ e p u s europaeus) found i n a reas with heavy SO2 and p a r t i c u l a t e depos i t ion from power p l a n t s and o the r i n d u s t r i e s .

Inges t ion i s the most commonly repor ted mode o f contamination f o r w i l d l i f e . I n j u r y and death t o w i l d l i f e from inges t ion o f contaminated food and water have been repor ted f o r numerous animal spec ies including r a b b i t s and deer from a r s e n i c emissions ( P r e l l 19361, dee r from f l u o r i d e emissions (Karstad 1967; Robinette and o t h e r s 1956; Newman and Yu 19761, and sparrows from cadmium emissions (Nishino and o t h e r s 1973). There a r e many r e p o r t s of the bioaccumulation of a i r p o l l u t a n t s i n w i l d l i f e . With a few excep t ions , the e f f e c t s of t h i s bioaccumulation a r e not known (Newman 1980).

A i r emissions may not be l e t h a l t o w i l d l i f e but may lower the h e a l t h and r e s i s t a n c e of w i l d l i f e so t h a t n a t u r a l s t r e s s such a s cold and shor tage of food may r e s u l t i n f u r t h e r i n j u r y o r dea th . Studies on the h e a l t h of wild hares (Lepus europaeus) l i v i n g i n a reas of h igh a i r p o l l u t i o n i n Czechoslovakia showed physiological responses s i m i l a r t o animals with i n f e c t i o n s o r a l l e r g i c r e a c t i o n s . There were a l s o changes i n t h e normal age s t r u c t u r e of the ha re popula t ions ( ~ o v a k o v a 1969). The general h e a l t h of deer popula t ions a f f e c t e d by f l u o r i d e emissions i s poor ( ~ o b i n e t t e and o t h e r s 1957; Karstad 1967; Newman and Yu 1976; Newman and Murphy 1979). The s u r v i v a l of these deer dur ing times of n a t u r a l s t r e s s i s quest ionable . Hais and Masek (19691, r e p o r t t h a t a r s e n i c contamination of red and roe dee r caused emaciation and loss of h a i r so t h a t many of the animals f roze t o death dur ing the win te r .

I n j u r y o r death t o vege ta t ion caused by a i r emissions can have s i g n i f i c a n t i n d i r e c t e f f e c t s on w i l d l i f e . The l o s s of food resources and h a b i t a t can occur a s the r e s u l t of i n j u r y o r

3 ~ n p u b l i s h e d r e p o r t , R.D. Harris 1971. Birds Collected (Die Off) a t Pr ince Rupert , B.C. Canadian Wi ld l i f e Service , Pr ince Rupert , B r i t i s h Columbia.

4 ~ e r s o n a l communication from E l i s k a Novakova, I n s t i t u t e o f Landscape Ecology, Prague, Czechoslovakia.

- -

dea th t o v e g e t a t i o n which provides cover , r ep roduc t ive h a b i t a t , o r food f o r w i l d l i f e . Many examples e x i s t o f e x t e n s i v e damage t o ecosystems from a i r emiss ions . Large a r e a s o f the mixed con i fe rous f o r e s t o f southern Ca l i fo rn ia (over 40,000 h e c t a r e s ) have been k i l l e d o r in jured from photochemical ox idan t s ( ~ a y l o r 1973). No o v e r a l l assessment has been made a s t o the l o s s o f w i l d l i f e whose f o r e s t h a b i t a t has been des t royed. S imi la r l a r g e w i l d l i f e h a b i t a t l o s s e s have occurred i n Montana, Tennessee, B r i t i s h Columbia, and Onta r io , Canada (~ewman 1980).

ECOLOGICAL EFFECTS OF AIR EM IS S IONS ON THE HOUSE MARTIN

With few excep t ions , t h e r e i s l i t t l e informat ion a v a i l a b l e on the e f f e c t s o f chronic exposure o f w i l d l i f e t o a i r emissions (Newman 1980). Since 1976, RNDr. E l i ska Novakova, CSC, from the I n s t i t u t e o f Landscape Ecology, Prague, and myself have been s tudying the eco log ica l responses o f the house mart in (Delichon u r b i c a ) t o chronic a i r p o l l u t i o n . In t h i s por t ion of the t a l k I would l i k e t o p resen t some o f our p re l iminary f i n d i n g s .

The house mar t in belongs t o the family Hirundinidae . It i s an insec t ivorous b i r d lAiich feeds p r imar i ly on aphids and d i p t e r e a n s . A migra to ry s p e c i e s , t h e mar t in summers throughout Europe and win te r s i n Af r i ca . As a c o l o n i a l n e s t i n g s p e c i e s , i t b u i l d s mud n e s t s on the w a l l s o f b u i l d i n g s . The n e s t i n g l o c a t i o n s a r e used each y e a r , o f t e n by t h e same b i r d s .

Previous s t u d i e s have ind ica ted t h a t 2. u r b i c a i s s e n s i t i v e t o a i r p o l l u t i o n . Fer iancova- Masarova and Kal ivodova (1965) observed changes i n the s p e c i e s d i v e r s i t y o f b i r d s , including the house m a r t i n , i n the a r e a o f an aluminum p lan t i n Czechoslovakia. Cramp and Gooders (1967) observed a c o r r e l a t i o n with increased nes t ing of D . u r b i c a and a decrease i n smoke p o l l u t i o n in London. A follow-up s tudy (~ewman 1977) in the v i c i n i t y o f t h e same aluminum p lan t s tudied by Feriancova-Masarova and Kalivodova i n 1965 showed t h a t 2. u r b i c a decreased i t s n e s t i n g d e n s i t y with inc reased a i r emiss ions .

In 1978 d i r e c t coun t s o f a c t i v e n e s t s were made i n 141 v i l l a g e s and towns loca ted i n i n d u s t r i a l i z e d (contaminated) and non- indus t r i a l i zed ( c o n t r o l or. background) a r e a s . Of t h e 141 n e s t i n g l o c a l i t i e s censused, 101 v i l l a g e s and towns were inf luenced by a i r emiss ions from var ious i n d u s t r i a l sources . Power p l a n t s and assoc ia ted su r face mines, chemical p l a n t s , l o c a l hea t ing p l a n t s ( coa l burn ing) , cement p l a n t s , and general urban emiss ions sources were the major a i r emission i n f l u e n c e s . Censusing was conducted a t pre-determined upwind and downwind l o c a t i o n s from an emiss ion source . This census represented obse rva t ions o f over 20,000 b u i l d i n g s . Records were kept o f t h e number o f a c t i v e n e s t s . A

s tandard n e s t i n g d e n s i t y measure was der ived a s we l l a s measures o f t h e occupancy o f a n e s t i n g l o c a t i o n and colony s i z e . The environmental a t t r i b u t e s o f each n e s t i n g l o c a l i t y was c h a r a c t e r i z e d . Comparisons o f background n e s t i n g l o c a l i t i e s were then made t o e c o l o g i c a l l y s i m i l a r , bu t contaminated, n e s t i n g l o c a l i t i e s .

The mean n e s t i n g d e n s i t y o f 2. u r b i c a from c o n t r o l a r e a s was 0.56521.94 n e s t s per s i d e . The range i n colony s i z e was 1 t o 33 a c t i v e n e s t s per occupied s i d e , wi th an average colony s i z e o f 2.721.1 a c t i v e n e s t s per occupied s i d e . The average occupancy ( t h e number o f occupied s i d e s per s u i t a b l e s ide ) f o r the 32 background n e s t i n g a r e a s was 2 1 . 0 3 . 1 pe rcen t .

The o v e r a l l n e s t i n g d e n s i t y f o r 1.u r b i c a from contaminated a r e a s was 0 .3933.734 a c t i v e n e s t s per s u i t a b l e n e s t i n g s i d e . This n e s t i n g d e n s i t y (30 pe rcen t ) was s i g n i f i c a n t l y lower

= 3.674, df = 8968) when compared t o^0.002 background nes t ing s i t e s . Occupancy was on ly 13.6 pe rcen t . Attempts a t n e s t i n g were a l s o lower , wi th on ly 0.74 a t t empts per contaminated v i l l a g e compared t o 1.12 a t t empts per background v i l l a g e . Colony s i z e was s i g n i f i c a n t l y lower (2.1+1.5 a c t i v e n e s t s per occupied s i d e ) . -

The house mart in responds a l s o t o the l e v e l of a i r emissions. The o v e r a l l nes t ing d e n s i t y f o r downwind l o c a t i o n s was 0.23720.378 (n = 4891) n e s t s per s i d e compared t o 0.41521.603 (n = 1969) n e s t s per s i d e f o r upwind l o c a l i t i e s . This d i f f e r e n c e was s i g n i f i c a n t (P < 0.001; t = 7.263; d f = 6808). The o v e r a l l upwind nes t ing d e n s i t y was not s i g n i f i c a n t l y d i f f e r e n t from background a r e a s .

Colony s i z e and occupancy a l s o changed with proximity t o emission sources . Upwind colony s i z e s averaged 2.521.0 n e s t s per occupied s i d e compared t o 1.820.8 n e s t s per occupied s i d e f o r downwind loca t ions . These d i f f e r e n c e s were s i g n i f i c a n t (P < 0.001; t = 3.492 d f = 99). Upwind occupancy (18.828.9 percent) was a l s o s i g n i f i c a n t l y h igher (P < 0.001, t = 5.70, d f = 99) when compared t o downwind occupancy (9.1+7.7 pe rcen t ) . -

The n e s t i n g d e n s i t y f o r downwind loca t ions dec reases s i g n i f i c a n t l y a s the d i s t a n c e to the emission source decreases ( t a b l e 2) . For upwind l o c a t i o n s , the c l o s e r t o the source , the higher t h e nes t ing d e n s i t y ; f o r increased d i s t a n c e s , n e s t i n g d e n s i t i e s decl ined. The upwind nes t ing d e n s i t i e s c l o s e s t t o emission sources were not s i g n i f i c a n t l y d i f f e r e n t from background nes t ing d e n s i t i e s . Colony s i z e was lower a t a l l downwind d i s t a n c e s , but only s i g n i f i c a n t l y lower a t t h e two c l o s e s t d i s t a n c e s . Occupancy was s i g n i f i -c a n t l y lower f o r a l l d i s t a n c e s censused downwind. For the two c l o s e s t upwind d i s t a n c e groups (ou t t o 6 tan) , bo th colony s i z e and occupancy were no t s i g n i f i c a n t l y d i f f e r e n t from background cond i t ions .

- -

- -

Table 2--Comparison of nes t ing dens i ty of D.- -u r b i c a a t var ious d i s t ances upwind and downwind from emission sources

Sample S i z e Me an Percent

Locat i o n ( , N ~ . of Sides)

Nesting Densi ty

Difference From Background

Downwind I

Upwind I

S i g n i f i c a n t , P < 0.025. ^ot S i g n i f i c a n t , P<O.O5

The a i r d i s p e r s i o n p a t t e r n s a s soc ia ted with t h e s t a c k h e i g h t s inf luenced the observed e f f e c t s . For sources w i t h h igh s t a c k s ( g r e a t e r than 100 meters) the adverse e f f e c t s on n e s t i n g were observed i n both downwind and upwind l o c a l i t i e s . For downwind l o c a t i o n s , t h e lowest n e s t i n g d e n s i t y d id not occur c l o s e s t t o the emission source , bu t a t an in termediate d i s t a n c e ( 3 t o 6 km). Nesting d e n s i t y was s i g n i f i c a n t l y . depressed out t o 12 km. For low s t a c k sources ( l e s s than 100 m e t e r s ) , t he lowest n e s t i n g d e n s i t y , colony s i z e , and occupancy occurred a t t h e c l o s e s t d i s t a n c e s (0 t o 3 km). Average n e s t i n g d e n s i t i e s were 20 pe rcen t o f background. In c o n t r a s t t o h i g h s t a c k sources , t h e n e s t i n g d e n s i t y inf luenced by low s t a c k sources was near normal a t t h e 9 .1 t o 12 km d i s t a n c e c a t e g o r i e s . For upwind l o c a l i t i e s , emiss ions from high s t a c k sources have an adverse in f luence , e s p e c i a l l y c l o s e t o the source . For low s t a c k l o c a l i t i e s , upwind n e s t i n g d e n s i t i e s were e i t h e r a t o r above background l e v e l s a t a l l d i s t a n c e s censused.

When the house mar t in n e s t s i n optimum nes t ing c o n d i t i o n s , such a s apartment b u i l d i n g s and f e e d l o t s i n proximity t o wa te r , the e f f e c t s o f a i r emiss ions were m i t i g a t e d . The g r e a t e s t adverse e f f e c t s on the n e s t i n g ecology o f D . u r b i c a were observed surrounding power p l a n t s and open s u r f a c e mines. Chemical p l a n t emissions had the n e x t most s i g n i f i c a n t e f f e c t on the house m a r t i n .

In summary, s u b l e t h a l and chronic l e v e l s o f a i r emissions from i n d u s t r i a l sources , such a s power p l a n t s and chemical p l a n t s , adverse ly a f f e c t the n e s t i n g ecology o f 2. u r b i c a , inc lud ing a r educ t ion o f the n e s t i n g d e n s i t y , colony s i z e , and occupancy o f t h i s s p e c i e s . The g r e a t e s t e f f e c t s on the n e s t i n g p a t t e r n o f D . u r b i c a were observed i n a r e a s downwind from t h e emission sources and a t decreas ing d i s t a n c e s from the a i r emission sources ( f i g . 1 ) . For low s t a c k emission sources , g r e a t e s t e f f e c t s were observed i n the immediate v i c i n i t y o f the s t acks where the h ighes t emission l e v e l s a r e expected t o occur . For h igh s t a c k s o u r c e s , g r e a t e s t e f f e c t s were observed a t in te rmedia te d i s t a n c e s from the s t a c k s and a g r e a t e r d i s t a n c e than observed i n low s t a c k l o c a l i t i e s .

Evidence suggests t h a t w i l d l i f e popula t ions l i v i n g i n optimal h a b i t a t c o n d i t i o n s a r e l e s s a f f e c t e d by a i r emissions than w i l d l i f e popula- t i o n s l i v i n g i n l e s s than optimal cond i t ions . This obse rva t ion has p a r t i c u l a r importance f o r t h e management and p rese rva t ion o f endangered spec ies .

Overal l the e f f e c t s o f a i r p o l l u t a n t s on w i l d l i f e can be dramat ic , such a s t h e d i e - o f f s , o r q u i t e s u b t l e , such a s s h i f t s i n the age s t r u c t u r e o f popula t ions . In many c a s e s the e f f e c t s have been d e b i l i t a t i n g i n j u r i e s , o f t e n c o n t r i b u t i n g to the dea th o f animals dur ing pe r iods o f n a t u r a l s t r e s s . A i r emissions can a l s o reduce w i l d l i f e popula t ions n o t on ly d i r e c t l y , bu t i n d i r e c t l y through l o s s o f h a b i t a t .

Acknowledgments: Specia l r ecogn i t ion is given t o RNDr. El i ska Novakova, CSc f o r c o l l a b o r a t i o n on the mar t in s tudy . I wish t o thank National Academy o f Science and the Czechoslovak Academy o f Science f o r support o f the b i r d s tudy and Environmental Sc ience and Engineering f o r a s s i s t a n c e i n the manuscript p repara t ion .

LITERATURE CITED

Cramp, S. , and J. Gooders. 1967. The r e t u r n of the house mart in .

Lond. Bird Rep., No. 31:93-98.

Feriancova-Masarova, Z . , and E. Kalivodova. 1965. Niekolko poznamok vplyve fluorovych

exhala tov v o k o l i Hl inikarne v Z i a r i nad Hronom na k v a n t i t u hn iezd iac ich vtakov (The e f f e c t s o f exha la t ions from the aluminum p l a n t i n Ziar nad Hronom on the spectrum of b i r d ' species i n the v i c i n i t y of the p l a n t ) . Biologia ( B r a t i s l a v a ) 20: 341-346.

Hais, K., and J. Masek. 1969. Vcinky nekterych exha lac i na hospodarska

z v i r a t a ( E f f e c t s of some exha la t ions on a g r i c u l t u r a l animals) . Ochr. Ovzduzi 3: 122-125.

Harkins, W.D., and R.E. Swain. on a Western Coniferous Forest Ecosystem. 1908. The chronic a r s e n i c a l poisoning of O.C. Taylor, ed. P a r t B, pp. 1-12. Task B

herbivorous animals. Rep. A i r P o l l u t i o n Research Center, J. Am. Chem. Soc. 30: 928-946. Unive r s i ty of C a l i f o r n i a , Rivers ide ,

C a l i f o r n i a . Kars tad, L.

1967. F luoros i s i n deer . Newman, J. R, ( ~ d o c o i l e u s v i r g i n i a n u s ) . 1977. S e n s i t i v i t y o f the house mart in

Bul l . 'Wildl. Dis. Assoc. 3:42-46. ( ~ e l i c h o n u rb ica ) t o f l u o r i d e emissions. F luor ide 100:'73-76.

L igh t , J.T. 1973. The e f f e c t s of oxidant a i r p o l l u t i o n on Newman, J.R.

f o r e s t ecosystems of t h e San Bernardino 1979. E f f e c t s of i n d u s t r i a l a i r p o l l u t i o n on Mountains. 2 Oxidant Air P o l l u t i o n E f f e c t s w i l d l i f e . Biol . Conserv. 15:181-190.

Chronic Effects of Acidic Precipitation and Heavy Metals on Forest Ecosystems

The Acidity Problem-Its Nature, Causes, and Possible Solutions1

Lowell smith2

Abstract: Interest within the scientific community in North America and Europe about the nature, effects, and causes of atmospheric acid deposition has grown rapidly over the past decade. This interest has recently intensified because of the explosion in public awareness of, and concern over, the acid deposition problem, and a growing political will to address the problem within appropriate national and international forums. his paper sketches the nature of the acid deposition problem; describes the atmospheric processes that convert precursor emissions into acidic compounds as these are transported over distances ranging from a few to more than a thousand kilometers; discusses past and possible future trends in geographical distribution and rate of acid deposition; and summarizes the governmental activities which have been initiated to address the problem.

The scientific study of acid deposition is invites reaction from any who take exception archtypical of many contemporary environmental to the summaries presented in this paper.3 problems, in that it necessarily covers a wide spectrum of disciplinary interests. Simply The major features of acid deposition are: listing the many subdisciplines involved

0would fill more than a page. It is impor- acid deposition results primarily tant for the active research worker in the from the combustion of fossil field to recognize the many interconnections fuels which releases sulfur dioxide between her or his own endeavors and other (SO2) and nitrogen oxides (NOx) research areas. This involves a careful in the form of nitric oxide (NO) balance because, at the same time one is and nitrogen dioxide (NO?) to the encouraging a cross-fertilization of ideas atmosphere; among various disciplinary efforts, one must guard against extending scientific judgements depositing acidic material is beyond one's own limits of competency. Since formed out of these precursor the author is fully aware of this hazard, he emissions by means of a large

number of chemical reactions as

'presented at the Symposium on Effects of the emissions are transported

Air Pollutants on Mediterranean and Temperate away from their source region;

Forest Ecosystems, June 22-27, 1980, Riverside, California, U.S.A. he views expressed in this paper are

those of the author and do not neces- '~irector, Program Integration and Policy sarily reflect those of the Environmental

Staff, Office of Research and Development, U.S. Protection Agency. Environmental Protection Agency, Washington, D.C.

acidic material is deposited dry in the form of fine particulate matter and is incorporated into all of the possible physical forms of precipitation;

transport distances between source and receptor regions can exceed a thousand kilometers, although a major source can, on occasion, significantly affect the rate of acid deposition within the first few kilometers downwind of the source; and

the effects of the deposited acid can vary markedly, depending upon the form in which the acid is deposited, the biologic, geologic and hydrologic pathways between deposition site and the receptor of interest, and the sensitivity of the receptor.

This paper explores these major features of acid deposition.

Nature of Acid Deposition

Acidic compounds may be deposited by several forms of precipitation (rain, snow, hail, dew, rime, and mist) as well as by fine particles that settle out of the atmosphere on to biologic, mineral, and aquatic surfaces, and on to man made materials, buildings, and artistic objects. Because monitoring techniques are not well developed for measuring and characterizing the dryfall component of acid deposition, comparatively little is known about its extent and variability (~urham and Hicks, 1980). Monitoring data from eastern North America indicates that the sulfate ion is the predominant anion present in acidic precipitation; the nitrate ion is associated with about half as much acidity as the sulfate ion, and chloride and other anions make substantially lower contributions (Hales, 1980). In some areas of the West the nitrate ion contributes an equal or larger share than the sulfate ion (McColl, 1980; and Morgan and Liljestrand, 1980).

Some regional scale atmospheric models estimate that up to half of the sulfate component may be deposited dry, while other models estimate a lower percentage (Whelpdale and Galloway, 1979). The variance results from a basic lack of understanding of the physical, as well as biological processes, and their variation over space and time, as these processes transfer gases and particles across the atmosphere/surface interface (~urham and

Hicks, 1980). In addition, nitric acid depositing onto surfaces out of its vapor phase may at times be an important contributor to dry deposition; but even less is known about its ambient concentration and geographical distribution (Altshuller, 1979). Thus, until monitoring techniques are developed for routine reliable measurements of dryfall deposition, we are compelled to rely on isolated spot measurements and tentative inferences to characterize this important phenomenon.

The characterization of wet deposition is a more tractable problem. While it is doubtful that precipitation at any place on the globe is entirely free of anthropogenic contaminants, relatively "clean" rainfall is generally found on the windward edge of continental land masses and where frontal storm systems have traversed large expanses of sparsely populated land surfaces (Granat, 1978). Because of the formation of carbonic acid from the hydrolization of background atmospheric carbon dioxide, such clean rainfall is thought to have a pH of about 5.6, approximately 25 times more acidic than a neutral pH of 7 (Likens, et. g.,1979). Yet even the pH of -rainfall relatively unaffected by anthropogenic emissions can vary by several pH units due to the entrainment of alkaline soil particles, reaction with atmospheric ammonia, and possibly other little understood factors (Stensland, 1979).

The concentration of acidity in precipitation is observed to be quite episodic (Smith and Hunt, 1979), which combined with the episodicity of precipitation rates, leads to great variability over space within a particular rain event and over time at a particular location of the rate of acid deposition (~ales, 1980). A range of over seven orders of magnitude of acidity (pH 2 to pH 9) has been recorded for various isolated rainfall events in North America. Averaged over time, spatial variations tend to vanish at locations distant from large sources. An excep-tion is the orographic effect produced by high terrain features on precipitation rates. This effect can be further augment- ed by the increasing acidity of cloudwater at higher elevations within a cloud structure (Falconer and Falconer, 1980). Terrain subject to orographic precipitation in North America and Europe, such as the Nothern Alps, that is downwind of high emission areas has been observed to sustain substantially increased quantities of deposited acidic material than similarly situated low lying terrain (Schrimpff, 1980).

Averaging wet acid deposition rates over an annual cycle for monitoring stations in eastern North America produces a pattern of depressed pH values in the northeast United States (Pack, 1980) extending northward into southern Ontario and Quebec, westward to the eastern Midwest, and southward along the Appalachian ridge into Tennessee and the Carolinas. Less depressed average pH levels extend deep into Florida (~rezonik,s.&. , 1980), west to Arkansas and Missouri, and northward an undetermined distance into Canada (Likens and Butler, 1980). The average acidity of precipitation in the central portion of this pattern approaches pH 4, approxi-mately a factor of forty more than what many consider to be the "normal" value of pH 5.6 (Likens and Butler, 1980).

Due to the spottiness of available monitoring information less is known about acid deposition rates west of the Mississippi River. Measurements made in the Boundary Waters Canoe Wilderness Area (northern Minnesota) (Glass and Loucks, 19801, the Colorado Rockies (northwest of ~enver) (Lewis and Grant, 19801, and California (the Sierra Nevada, and the Los Angeles and San Fran- cisco Bay basins) (McColl, 1980; and Morgan and Liljestrand, 1980) all suggest that this problem is not unique to the eastern half of the continent.

Effects of Acid Deposition

Acid deposition creates a public policy problem to the extent that potentially sensitive receptors are harmed by the deposition rates they sustain. Research results on acid deposition effects are multiplying rapidly in North America and Europe (International Conference on the Ecological Impact of Acid Precipitation, 1980). An impressive body of information now exists as to the impact of acidifying surface waters on the ecosystems they support (Gorham, 1976). Some fish species show adverse effects below pH 6; while other more tolerant fish species do not evidence serious effects until pH 4 or lower has been reached. Eggs and especially the fry of sensitive species are more susceptible than are adult fish (Johannson, -et. &., 1977). Thus, during the initial melting of a snowpack, acid pulses may be released which abnormally skew subsequent fish population distributions to the extent that one or more generations may be completely absent in some instances. Other portions of aquatic food chains can also be affected to the detriment of wildlife species at the top of these chains, including fish eating birds (Peakall, 1980) and freshwater wading birds (~oucks, 1980).

Recent evidence from Europe suggests that leaching of calcium and other nutrients from the lower horizons of sensitive soils and the concomitant mobilization of Al3+ ion within these soils (Ulrich, 1980) is promoted by atmospheric acid deposition. Also observed is a reduction of the decomposition rate of forest litter and decreased numbers of micro-organisms (Baath, s.&., 1978) within the

upper soil horizons of forest soils subjected to heavy rates of acid deposition. In extreme cases ground water quality may be adversely affected (Hultberg and Wenblad, 1980). Abnormally low pH for drinking water supplies drawn from wells in some of these regions has been observed. This can result in unacceptably high concentrations of copper and lead in drinking water in those . homes which are equipped with copper plumbing systems (~ultberg and Wenbald, 1980).

Agricultural crop species cultured in pots and subjected to lowered pH simulated acid rain irrigation water have displayed mixed responses in yield (Lee, z.e.,1980). Some cultivars exhibit enhanced yields and others depressed yields while many cultivars show no discernible effect on yield. The effect of acidic deposition on forest growth rates is more uncertain. Early stages of acidification can accelerate growth rates for a few years, possibly due to the increased mobilization of nutrients within the soil structure. But sustained elevated rates of acid deposition are hypothesized to depress forest growth rates in geologically sensitive areas due to nutrient depletion and elevated concentrations of AI^+ ion within the root zone. Other ecological effects are discussed elsewhere (Overrein, 1980, Norton, et. G., 1980, and Cowling, 1980). -Mechanisms of Atmospheric Formation

As previously stated, acid deposition is primarily the result of the anthropogenic release of SO2 and NOx to the atmosphere where these react through several available chemical pathways to sulfuric and nitric acids. To a lesser extent hydrochloric acid can also be involved. Coal and oil fired electric utility generating stations, predominantly in the central and eastern portions of the U.S. are responsible for two-thirds of the national SO2 emission inventory (U.S. EPA, 1979a). Nine-tenths of these emissions are from coal-fired stations. Industrial and commerical boilers account for nearly half of the remaining emissions. SO2 emissions in the U.S. are likely to increase slowly over the next few decades as emissions from well-controlled new sources slightly overbalance emission reductions expected to be achieved by the control or retirement of existing sources (Altshuller and McBean, 1979). Canadian SO2 emissions come predominantly from their non-ferrous smelter industry at present, but by the end of the century coal fired utility boiler emissions are expected to about equal those from the smelter industry (Choquette, 1980).

Two-fifths of the nation's NOx emissions come from motor vehicles. Geographically, these mobile sources are clustered around large population centers. Nine-tenths of the remaining NOx emissions are released by the same large utility and industrial boilers which are responsible for the predominant portion of the SO2 inventory (U.S. EPA, 1979a). NOx emissions are expected to increase significantly in the U.S. and Canada over the remainder of the century,

unless some promising breakthrough in NOx emission controls is achieved and rapidly implemented by industry (Altshuller and McBean, 1979).

Although no emission inventory exists for chloride ions, these emissions are likely to be primarily the result of burning high chloride coals produced from many coal seams in the midwestern and eastern U.S. Therefore, chloride emissions are likely to be colocational with large SO2 and NOx emitting sources. Natural emissio s of SO2 (Adarns,s. &., 1980) and NO: make only modest additions to the anthropogenic sources in eastern North America, though natural emissions may make an appreciable contribution to the global background of these atmospheric constituents (Husar, s. al., 1978).

These precursor emissions react in the atmosphere with water vapor, other minor atmospheric constituents and sunlight to produce fine sulfate particles, nitric acid vapor and dilute acids in cloud droplets. These submicron particles agglomerate into larger particles until a natural barrier to further growth is reached at slightly above one micron mean diameter. The growing particle may be deposited in dry form onto a surface, incorporated into a cloud droplet (rainout), or scavenged by a falling raindrop (washout) (Hales, 1980). The hydroxyl ion in conjunction with sunlight is believed to promote the formation of particulate sulfate (Davis, s.&., 19741, while the peroxyl ion is believed to promote the conv r- sion of SO2 to sulfuric acid in cloud droplets. 5

In the summer months, substantially enhanced concentration of sulfate ion are found in deposited rainwater while nitrate ion concentrations tend to be more constant throughout the year (Hales, 1980). There is some evidence to suggest that nitrogen oxides are deposited more rapidly from the atmosphere on the average than are sulfates (Mueller, s.&. , 1979), so nitric acid -deposition may be relatively less important for receptor sites far from emission regions than is sulfuric acid deposition.

Another complicating feature in the atmospheric chemistry of acid deposition is the atmosphere's ability to partially neutralize its acid load. Alkaline fine wind blown soil particles, particularly over arid regions, appear to neutralize the acid load (Eisenreich, s.&.., 1980), or create aerosols with basic chemical properties. The ammonium ion is also effective in partially neutralizing dry and wet atmospheric acidic materials. Many natural and anthropogenic sources produce ammonia, but a complete ammonia emissions

4~ersonal communication from Dr. Rudolph Husar, August 15, 1980, Washington, D. C.

'personal communication from Dr. A. L. Lqzrus, May 21, 1980, Washington, D. C.

inventory has yet to be constructed. Stockyards, municipal waste water treatment plants, certain industrial processes, and decaying vegetable matter are among its important sources.

Some investigators have hypothesized that fly ash from coal combustion has historically played a major role in reducing atmospheric acidity and that recent efforts to control fly ash emissions have noticeably worsened the acid deposition problem (Frohlinger and Kane, 1975). Such an effect is unlikely to have been nearly as important as was once supposed. As will be discussed later in this paper it is unclear what the historic trends for deposited acid are in the Northeast. Thus, such an ad hoc explanation may not be relevant to explain what is an inconclusive trend. More importantly, considerations such as the size of fly ash particles relative to the size of sulfate particles, the chemical composition of fly ash from midwestern and eastern coals, and the change from stoker-fired coal boilers to pulverized coal boilers during this period, all suggest that the neutralizing effect of emitted fly ash could only have been important in the immediate locality of a relatively few heavy fly ash emitting sources.

Mechanisms of Atmospheric Acid Transport

Several physical processes are important to the atmospheric transport of acid precursors and their acidic products. Particularly important for the S~~/sulfuric acidlsulfate complex is the elevated height of injection into the atmosphere level for SO2 emissions from most major power plant sources. A nocturnal inversion layer frequently isolates these tall stack plumes from the gr~und (Smith, s.&., 1978) until after sunrise when the incident solar energy begins to mix the atmosphere through the activation of convective cells. In the Midwest during summertime conditions, a nocturnal bulge in the wind speed vertical profile is frequently observed at normal tall stack plume heights. This condition can transport emissions from a tall stack several hundred kilometers overnight (Smith, s.&., 1978). The gas to particle conversion of the emissions in this displaced plume can be greatly accelerated the next day as these transported emissions are mixed with a polluted urban air mass.

The highest ambient concentrations of particulate sulfate are observed under summertime conditions when a synoptic scale high pressure system stalls for more than a day over a region of high SO2 emission density, such as the Ohio River Basin (Hidy, s. al., 1978). In this situation weakly circulating winds can trap a large air mass while it is being continually filled with precursor emissions (Vukovich, 1979). The higher temperature, moisture and sunlight levels generally encountered under these conditions tend to increase the chemical reactivity of the atmosphere, so the higher concentration of precursor emissions can more rapidly be converted to particulate sulfate.

I

A common atmospheric cleansing mechanism for this condition is for a cold front to approach the high pressure center from the north or northwest (Whelpdale, 1978). This creates a strong pressure gradient which sweeps much of the polluted air mass parallel to the line of the front for many hundreds of kilometers, frequently to the northeast. (LaFleur and Whelpdate, 1977). Frontal storm activity can further remove considerable amounts of pollutants as rainout and washout. Similarly, large convective storms are believed to be an efficient mechanism for processing and removing pollutants from the large volume of air they entrain. These storms are capable of pumping large quantities of polluted air from the planetry boundary layer to high elevations where these can be left as isolated patchy layers to be transported considerable distances and eventually deposited.

Alternating periods of stagnation and ventilation over a high emission area produce episodic concentrations of pollutants (~ttar, 1978) which result in highly variable acid deposition rates in downwind regions. Likewise, the variability in wind direction, as it guides and mixes isolated plumes from major sources and the regional scale plumes described above, adds to the temporal variability of deposition rates at any monitoring site. Thus, acid deposition must be viewed as a stochastic process which, in areas not under the influence of a major source and not affected by orographic terrain effects, is temporally and spatially chaotic over a small scale but is rather spatially homogeneous within a given region when averaged over a large number of events.

Historical Trends in Acid Deposition Rates

While the routine measurement in a scienti- fically reliable manner of wet deposited acid has only recently, with the exception of a very few monitoring stations, been undertaken in this country, it has been practiced in . several European countries over a longer period of time (Granat, 1978). Both the European and North American experiences have demonstrated the need for strict quality assurance procedures for collecting and analyzing the rain water samples. Failure to establish sufficiently stringent quality assurance procedures early in monitoring programs has created questions about the validity of much of the early data (Tyree, 1980).

The need to calculate retroactively the acidity of monitored rainfall using one of several ion balancing procedures, has compounded these measurement difficulties since acidity or pH was usually not measured directly (Kramer, 1978). Such procedures can propogate the experimental uncertainties, which were introduced by the collection and laboratory procedures employed, into rather sizable uncertainties in the calculated hydrogen ion concentration. Further careful analysis of all

available rainwater chemistry monitoring data is required in order to establish the level of certainty with which historical trends of acid deposition in North America can be determined.

Fortunately, it may be possible to describe the gross features of deposition trends by relying on other related physical phenomena for corroborative support. Since sulfate aerosols are highly efficient light scatterers due to their characteristic submicron size, and since sulfate is the dominant component of Eastern aerosols (U.S. EPA, 1979b), visibility trends probably serve as a useful indicator for dry sulfate deposition trends. The ratio of dry to wet sulfate deposition should have remained relatively constant for a particular area unless a climate change has occurred.

Visibility measurements have been routinely made at medium and large size airports in the U.S. for several decades. Recent analysis of these data shows that summertime visibility has significantly deteriorated throughout large portions of the eastern U.S. (Trijonis and Shapland, 1979). Some regions such as the Tennessee Valley appear to have sustained nearly a factor of two decrease in average summertime visibility over a twenty- five year period (Husar, =.&., 1979). Similar trends in summertime solar insolation are also suggestive of a increase in atmospheric turbidity during this same period. Further analysis effort is required to assess the possible causal relationships between trends in precursor emission rates and these trends in environmental conditions.

Although the trends of such surrogates for acid deposition may only be used to corroborate an inconclusive record for monitored acid deposited, other studies strongly support the conclusion that anthropogenic emissions are deposited on ecosystems far from their point of origin. Dated lake bottom cores from remote lakes in North America and Greenland icecap cores show a marked increase in deposition rates for fossil fuel combustion-related pollutants shortly after the beginning of the industrial revolution.

A review of emission trends from U.S. sources over the past forty years indicates several clear trends. First, SO2 emissions increased about forty percent. ~ l t h o u ~ h ~ 0 ~ emissions have decreased from most economic sectors during this period, the electric utility sector's emissions increased by more than a factor of six during this same period (EPA, 1978). Second, the increase in SO2 emissions from this one sector occurred concurrently with a substantial increase (by approximately a factor of five) in the stack height for utility sources. Third, SO2 emissions from coal burning changed from a wintertime peak to a summertime peak in emission rate (Husar, =.&., 1979). Fourth, the precursor emissions for photochemical oxidants increased markedly during this time (EPA, 1978). At the beginning of the period photochemical smog was hardly recognizable as a problem, whereas, currently urban plumes of photochemical oxidants now frequently blanket the Northeast during the summer months (Altshuller, 1978). Fifth, total NOx emissions approximately quadrupled during this period (EPA, 1978).

These trends suggest a situation in which the atmosphere has become chemically more reactive, and for which greater quantities of acid-forming precursors are added to the atmosphere during its most reactive period. Further, a substantially greater quantity of these emissions is now injected high into the mixed layer where the emissions and their reaction products have much longer residence times as they travel to areas remote from their point of origin.

Possible Solutions

At present there are no regulatory requirements that are primarily directed at reducing emissions to control acid deposition. However, the Clean Air Act's requirement to reduce ground level SO2 concentrations has achieved modest overall reductions in SO2 emissions during the first part of the past decade (u.S. EPA, l979a). But, average stack heights continued to increase, as did the emission rates for NOv, over this period. Regulatory requirements established for new coal-fired utility boilers mandate control of seventy to ninty percent of their SO2 emissions and require NOx emission reductions of approximately forty percent (U.S. Federal Register, 1979). EPA is currently developing new source control performance standards for industrial boilers which could require similar levels of control for this important source category. From a regulatory perspective the principal problem for SO2 emission control is the control of emissions from existing sources. In addition, there are large opportunities for improved NOx control requirements for new and existing sources.

Others have maintained that the costs of emission control are so high that the only cost-effective mitigation measure is to raise artifically the pH of affected lake water by the addition of lime (~arnes, 1979). Repeated treatments would be required as long as acid deposition rates exceeded the geologically controlled release rates for a given area (Horn, s.&., 1980). Recent Swedish experience indicates that liming the entire watershed for a lake may be necessary, while others believe that even though it is possible to raise the pH of an acidified lake, it is not possible to restore the lake to a natural condition containing its original food chains. Others have observed that the potentially sensitive areas in North America cover millions of hectares, and question the feasibility of liming such a vast area for hundreds of years.

Federal government efforts to address the acid deposition problem include:

monitoring activities to establish more fully the geographical var-iation and temporal trends in rainwater chemistry;

research activities to determine more completely the range of environmental effects produced by acid deposition and the atmospheric processes which transport and convert emissions into acid deposition;

assessment activities to determine the potential seriousness of the acid deposition problem in North America and the most cost-effective measures that could be employed as first steps to combat the problem;

the creation of a ten year inter-agency Federal Acid Rain Assessment Program to coordinate the above activities;

working with the states in order to promote a mutual understanding of the nature and causes of the acid deposition problem, and to encourage the states to engage in collective problem solving on this issue; and

becoming a signatory to an international Convention on Long-Range Transboundary Air Pollution, developed under the auspices of the United Nations Economic Commission for Europe, and pursuing bilateral discussions with Canada which are expected to evolve into formal negotiations on a U.S.-Canada bilateral transboundary air pollution agreement.

Such efforts cannot be expected to bring about immediate and complete relief from the acid deposition problem - nor are they designed to achieve this objective. Rather the goals are to establish as quickly as is feasible a scientific basis for understanding the full range of receptors at risk and the extent of risk to each receptor category; to determine the extent of the control measures which are required to reduce the acid deposition problem to an acceptable level; to develop new air pollution control policies and strategies as necessary and appropriate; and to promote full cooperation and understanding across interstate and international borders to deal effectively with this complex and challenging problem.

Acknowledgments

The author is deeply indebted to many colleagues and research workers for the opportunity to learn from and share ideas with them. Particular credit is given to Dr. Brand L. Niemann for

^~ote added in editing: A Memorandum of Intent was signed in Washington, D. C., on Aug. 5, 1980, by the two governments in which they agreed to initiate formal negotiations by June 1, 1981.

his helpful comments, to Ms. Barbara H. Brandon and Mr. Paul Schwengels for their editorial advice, and to Ms. Mable Scales and Ms. Veronica Parker for their special efforts in typing the manuscript. Finally, I wish to thank Dr. Paul R. Miller for the extraordinary patience he displayed while coaxing me to complete this paper.

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Acid Precipitation Impact on Terrestrial and Aquatic Systems in Norway'

2Lars N. Overrein

Abstract: In recent decades the ac id i ty of r a i n and snow has increased sharply over wide areas. The pr inc ipa l cause i s the release of sulphur and ni t rogen oxides by the burning of f o s s i l fue ls . The a i r qua l i t y i n any one European country i s measurably a f fec ted by emissions i n o ther European countries. Strong ac ids have lowered the annual mean pH of prec ip i ta t ion i n much of northern Eu- rope t o between 4 and 5. In southern coas ta l areas of Norway, the annual mean ac id i ty i n prec ip i ta t ion i s now 4.3 pH-units, o r even more acidic .

Acid p rec ip i t a t i on has increased leaching of nut r i - en t s from the uppermost s o i l layers . These losses of nu t r i en t s may be expected t o decrease p lan t growth, but f i e l d evidence i n Norway and elsewhere, has not ye t been obtained. It is possible t h a t po l lu ted a i r and p rec ip i t a t i on over a period of years can influence p l an t production.

Atmospheric t ranspor t of sulphur and o ther acidifying components has l ed t o extensive regional ac id i f ica- t i on of water courses i n areas with very l i t t l e neutra- l i z a t i o n capacity. Acidif icat ion of watercourses had had major e f f e c t s on l i f e i n r i v e r s and lakes. Lakes i n an area of 13,000 km2 i n southern Norway have become empty of f i s h i n recent decades, and a fu r the r a rea of approx. 20,000 km2 contains lakes with s ign i f i can t ly reduced f i s h stocks.

The ecological impact of ac id prec ip i ta t ion has In Norway ac id prec ip i ta t ion was a t t h a t time seen been a matter of growing concern over the l a s t de- a s a possible cause of increasing ac id i ty of t he cade p a r t i c u l a r l y i n the i ndus t r i a l i zed countr ies watercourses i n the southern p a r t of t he country, of t he Northern Hemisphere. and of the gradual disappearence of valuable f i s h

populations from many lakes and r i ve r s . It was a l - The Norwegian In te rd isc ip l inary Research Pro- so feared t h a t t he inputs of acid might over time

gramme "Acid Prec ip i ta t ion - Effec ts on Forest and reduce f o r e s t growth pa r t i cu l a r ly through increased Fish", (The SNSF-project) was i n i t i a t e d i n 1972. leaching of nu t r i en t elements from the s o i l .

The SNSF-project has t h i s year marked the con-Presented a t t h e Symposium on Effec ts of A i r c lusion of e igh t years of research by organizing

Pol lu tan ts on Mediterranean and Temperate Forest the In te rna t iona l Conference on the Ecological Im-Ecosystems, June 22-27, 1980, Riverside, pact of Acid Prec ip i ta t ion . This Conference, which Cal i forn ia , U.S.A. was held i n Sandefjord, Norway, March 11 - 14, 1980,

2 ~ e s e a r c hDirector,The Norwegian In t e rd i sc ip l i - a t t r ac t ed more than 300 pa r t i c ipan t s from some 20 nary Research Program, Acid Prec ip i ta t ion - countries. Ef fec ts on Forest and Fish. The SNSF-project - 1432 Aas-NLH, Norway. The present report is mainly a summary and b r i e f

discussion of the ecological impact of acid precipitation in Scandinavia with particular reference to Norway.

EMISSIONS, TRANSPORT, AND DEPOSITION

The concept of acid precipitation is now used to denote precipitation with high amounts not only of the hydronium ion (H+ for short), but with enhanced concentrations of the acidifying anions sulphate, 304 and nitrate, NO3, which predominantly stem from anthropogenic sources. "Acid" precipitation regularly also contains high amounts of ammonium, NH4, and of various heavy metals and trace elements including organic micropollutants.

It should also be kept in mind that comparable amounts of anthropogenic pollution may be deposited by dry deposition processes from the same air masses giving acid precipitation. In studies of effects of acid precipitation the contribution from dry deposition is often difficult to quantify. In areas remote from the main industrial centres, like in Southern Norway, acid precipitation is more or less synonymous with long-range transported air pollution, but the distinction should always be observed. In our context, sulphur and nitrogen compounds giving rise to the acidifying properties of precipitation, are of prime interest, and their sources should be described with a view to finding their geographical distribution, emission rates and seasonal variation. This is necessary both for enabling modelling of their transport, and for formulating abatement policies against their negative effects.

Sulphur Emissions

Most of the man-made sulphur emissions occur as SO2 from combustion of coal and petroleum products. Comparatively less stems from smelting of sulphur-containing mineral ores and other industrial processes, on a global basis about 10 percent. Knowledge of the location of industrial and powerproducing units in addition to population distribution has allowed quantification of annual emissions in a 150 km x 150 km grid over Europe (Semb, 1979) . The main area of SO2 emissions corresponds to the industrial belt from the Midlands in U.K., the Netherlands and Belgium, central and southern parts of Germany and Poland. Parts of northern France, Czechoslovakia and USSR also have industrial concentrations with very high emission rates. On a country basis, total SO2 emissions in 1973 were estimated at e.g. 2.8 lo6 tonnes S from UK, 2.0 from the Federal Republic of Germany and 1.6 from France (OECD, 1977) . Nor- wegian annual emissions were estimated at 91,000 tonnes of S.

Seasonal variations in SO2 emissions occur as the demand for energy fluctuates through the year. At high latitudes the variable component of emis-

sions is related to space heating and illumination during winter. In warmer climates, the maximum demand may occur during summer due to the use of air conditioning. In most of Europe, the fuel consumption will probably be at its peak in Janu- ary - February. The seasonal variation is about 30 percent of the annual mean emission.

Nitrogen Emissions

Both nitrogen oxides, NOx, and ammonium, NH4, play important roles for the composition of acid precipitation. Although global budgets of nitrogen compounds are even more uncertain than those of sulphur, natural sources seem to be larger than the man-made. However, major man-made emissions also of nitrogen compounds occur in Europe and thus influence strongly precipitation chemistry in Scandinavia. The main anthropogenic source of nitrogen oxides is combustion of fossil fuels, by oxidation of nitrogen compounds in the fuel and oxidation of nitrogen in the combustion air.

It is well known that the NOx emissions depend on fuel types, combustion chamber design and operating conditions. High combustion temperatures favour the emissions. There is, naturally, a high spatial correlation between SO2 and NOx emissions. OECD studies indicated almost a doubling of anthropogenic nitrogen oxides emissions in Europe from 1959 to 19%73, thus increasing more than sulphur dioxide emissions in the same period (OECD, 1977).

Trace-Element Emissions

Acid precipitation contains a wide range of minor and trace elements associated with the major chemical constitutents. Heavy metals, other trace elements and organic micropollutants of man- made origin are receiving increasing interest as some of these are enriched in living organisms.

Emission rates for trace elements and micropollutants are largely unknown, but the main sources are known . Many of the organic micropollutants in the atmosphere are products of human activity, including industrial and waste products, and also chemicals used in industry as solvents or intermediate products. The emissions are very complex mixtures of chemical compounds.

Transport and Deposition

Of particular interest for long-range pollutant transport is the build-up of high concentrations in stagnant air near the ground during inversion situations. Observations show that such parcels of contaminated air may subsequently move over long distances without much dilution. A much used technique in analyzing source areas and transport directions of air pollutants, is the sector analysis, grouping together trajectories belonging to the same sector.

Of considerable i n t e r e s t f o r the proportion of sulphate i n ac id p rec ip i t a t i on t o dry deposited sulphur components, i s the oxidation r a t e from sulphur dioxide t o sulphates. The oxidation takes place both by absorption of SO2 i n cloud drople ts with subsequent oxidation, and by oxi- dat ion i n the gas phase with oxygen compounds i n the atmosphere. High concentrations of ozone and photochemical oxidants, which a r e observed over la rge a reas of Europe, w i l l increase the t rans- formation r a t e . The t r a n s f e r of gases and par- t i c l e s from the a i r t o na tura l surfaces, and the adsorption, a r e usual ly described i n analogy with the theory of e l e c t r i c a l res i s tance . The t ranspor t from the atmosphere t o the boundary layer close t o the surface, takes place by turbulent diffusion. The aerosol p a r t i c l e s i n question, i - e . , sulphur and nitrogen aerosols , a r e mostly i n t he 0.1 - 1.0 pm s i z e range with low gravi ta- t i ona l s e t t i n g , and the turbulent t ranspor t w i l l depend on meteorological conditions.

Model ca lcu la t ions of wet and dry deposition pa t t e rns over Europe show t h a t i n Scandinavia, pa r t i cu l a r ly i n Norway, the wet deposition out- weighs t he estimated dry deposition. For southern Norway dry deposition i s estimated t o account f o r about 30 percent of the t o t a l deposition of ex-cess sulphate.

The p rec ip i t a t i on i n Norway i s la rge ly determined by po la r f ron t lows bringing moist maritime a i r i n wester ly t o south-easterly d i rec t ions . Of p a r t i c u l a r importance i s the orographic enhancement of p rec ip i t a t i on , caused by the l i f t i n g and subsequent cooling of t he a i r masses when flowing across t he Scandinavian mountain chain. This gives r i s e t o a maximum zone of elevated precipi- t a t i o n some 40 - 50 km from the coast l ine. In this zone, annual mean p rec ip i t a t i on exceeds 1000 mm along the SE coast increasing t o an abso- l u t e maximum of perhaps more than 5000 mrn i n north western Norway. S t i l l f u r the r north, i n northern Norway, annual p rec ip i t a t i on i n t he maximum zone exceeds 2000 mm.

The group of macrocomponents t yp i ca l of ac id p rec ip i t a t i on , i . e . H+, NH4, SO4 and NO3, has a marked north-south gradient . The cor re la t ions between sulphate, n i t r a t e and ammonium a r e high, and there a r e roughly equivalent amounts o f t h e p r inc ipa l ca t ions H + NH4+ and anions SO4 and-NO3 . The content of s t rong mineral ac id i n pre- c i p i t a t i o n i s strongly cor re la ted with excess sulphate. The cor re la t ion coe f f i c i en t i s 0.7 -0.9 a t Norwegian s t a t i ons . A t Norwegian s t a t i ons No3 makes about 30 percent of t he sum SO4 + NO3. Ammonium and n i t r a t e occur i n Norwegian precipi- t a t i o n i n about equivalent concentrations, lowest a t mountain s t a t i ons . The concentrations of ~ 0 4 ~ -and H+ i n p rec ip i t a t i on a r e highest along the south-east coast . The mountain plateau i n northernmost Norway i s af fec ted by a i r t ranspor t from the south, which gives ac id prec ip i ta t ion (pH 4.5 - 5.0) a s f a r north a s 70O~. l a t . In southernmost Norway about 10 percent of t he pre-

c ip i t a t i on has a pH below 4.0 and about 5 percent above pH 5.0. Prec ip i ta t ion ac id i ty below 3.5 has been observed several times a t several places, Dovland and Semb, (1980).

Present knowledge of atmospheric deposi t ion of inorganic t r ace elements i n Norway i s compiled by Semb (1978). They a r e found i n the watersoluble f rac t ion of aerosols , o r absorbed on the o ther pa r t i c l e s , and are mostly contained i n t h e aerosol s i ze f r ac t i on with aerodynamic mass diameter below 2 urn. Available da ta f o r lead, zinc and cad- m i u m i n prec ip i ta t ion shows a deposition pa t t e rn s imi la r t o t h a t of excess sulphate. Also antimony, arsenic, selenium and vanadium seem t o have s imi la r deposition pa t te rns . Influence from me- t a l l u r g i c a l i ndus t r i a l centres is evident f o r instance f o r chromium (western Norway) and arsenic , selenium, nickel , chromium and copper (smelting industry i n the Murmansk area , U.S.S.R.). In northern Norway t r a j ec to ry ana lys is shows t h a t highly pol luted episodes a r e of ten associated with t he re turn flow pa t te rn discussed by Rahn and McCaff- rey (1980). Several s tud ies of organic micropol- l u t an t s i n prec ip i ta t ion and i n aerosols have been performed within t he SNSF pro jec t . They have iden t i f i ed a wide range of compounds i n the same a i r masses bringing ac id p rec ip i t a t i on t o Norway.

ECOLOGICAL IMPACT

The e f f e c t s of a i r po l lu t ion have h i s t o r i c a l l y been considered loca l problems, occurring near pol- l u t a n t s sources, usually urban areas. This concept of pol luted c i t i e s versus clean r u r a l areas is no longer applicable. The increase i n anthropogenic emission sources coupled with t he increased height of emissions have enhanced the phenomena of a i r po l lu t ion e f f e c t s on r u r a l areas. The most s t a r t l i n g e f f e c t s discovered so f a r of t he long-range transmission of pol lu tan ts , have appeared i n r e l a t i v e l y remote, p r i s i t i n e a reas of Norway, Sweden and the Eastern United S ta tes and Canada.

Despite the f a c t t h a t sulphur dioxide emissions t o a large ex ten t contr ibute t o ac id p rec ip i t a t i on the two pol lu tan ts show g rea t differences i n e f - fec ts . Sulphur dioxide i s a primary a i r po l lu tan t a s well a s a primary toxicant . Acid p rec ip i t a t i on on the o ther hand, i s a secondary pol lu tan t caus-ing mainly i nd i r ec t e f f e c t s on ecosystems.

Forest Ecosystems

The e f f e c t s of a i r po l lu tan ts on p l an t s i s ex-tremely d ivers i f ied ; it depends upon species- linked tolerance o r suscep t ib i l i t y , and is a func-t i o n of many exposure parameters (frequency, time, concentration, e t c . ) . Many types of response have been described on the bas i s of laboratory experiments, where known chemicals were t e s t ed under control led conditions with d i f f e r en t p lan t species.

However, the inverse operation - namely ident ify- i ng and est imating the nature and importance of an ex i s t i ng source on the bas is of response symp-toms - i s of ten d i f f i c u l t , except i n the case of acute i n ju ry and when a pol lu t ion source i s known o r suspected i n the v i c in i ty .

Vegetation damage due t o the emission of acid and poisonous substances has long been observed i n the v i c i n i t y of emission sources. Visible symptoms have been decribed and a r e often asso-c i a t ed with the decrease i n growth. Recently, however, concern has been expressed t h a t f o r e s t growth may ako be a f fec ted f a r away from emission sources. Even i f the d i r e c t evidence i s meagre, Tam, (1976), there i s f a i r l y subs tan t ia l indi- r e c t evidence t h a t continued exposure t o ac id r a i n has a growth-decreasing e f f ec t . The most s ign i f i can t i n d i r e c t evidence i s the pos i t ive cor re la t ion between f o r e s t y i e ld and the s o i l base s t a tu s . Jonsson and Sundberg (1972) c l a s s i - f i e d areas i n southern Sweden a s r e l a t i ve ly re-s i s t a n t t o ac id r a i n and r e l a t i v e l y susceptible t o ac id r a in , respec t ive ly , and compared the growth trends i n both areas by measuring annual r ings on increment cores from groups of t r e e s which were otherwise a s i den t i ca l a s possible . They found a s t a t i s t i c a l l y s ign i f i can t difference and "found no reason f o r a t t r i b u t i n g the reduc- t i o n i n growth t o any cause o ther than a c i d i f i - cat ion." These r e s u l t s however, have not been confirmed by Norwegian researchers , Abrahamsen and o thers , (1976) ; Abrahamsen, (1980), Strand, (1980).

When evaluat ing the e f f e c t of ac id prec ip i ta - t i on on the supply of p l an t nu t r i en t s i n a for-e s t , a ba s i s could be t o consider the nu t r i en t cycle i n a t e r r e s t r i a l ecosystem. P lan t avai l- able nu t r i en t s a r e general ly supplied t o the system from two sources; from the atmosphere, a s f o r N and S, and from the minerals, a s f o r Ca, Mg, P I K, S, and the micronutrients. I n na tura l systems not harvested by man, nu t r i en t s a r e a l so l o s t i n two ways: To the atmosphere by v o l a t i l i - zat ion and t o the sea by leaching. Evaluation of the e f f e c t of ac id p rec ip i t a t i on on the amount of p l an t nu t r i en t s i n a f o r e s t ecosystem can there-fore be r e s t r i c t e d t o the consideration of four processes; deposi t ion from the atmosphere, wea-thering, v o l a t i l i z a t i o n and leaching from the s o i l . Obviously many processes i n the s o i l and the p l an t s can a f f e c t the acces s ib i l i t y of p l an t nu t r ien ts . Acid r a i n may a f f e c t some of these processes.

Experimental s tud ies on t r e e growth i n re la - t i o n t o ac id r a i n have been conducted i n recent years i n severa l countr ies . A s y e t no conclu-s ive evidence of decreased growth has evolved. On the contrary, a s l i g h t l y pos i t ive growth ef - f e c t on the seedl ing, which was explained a s a nitrogen f e r t i l i z e r e f f e c t , was reported by Wood and Bormann, (1975). Such increases, though, a r e l i k e l y t o be temporary, a s deplet ion of nu-t r i e n t ca t ions through accelerated leaching

should eventually r e t a rd growth. Experiments on the e f f e c t of a r t i f i c i a l a c id i f i ca t i on on f o r e s t growth under f i e l d conditions have been ca r r i ed Out i n Sweden and Norway. The Swedish experiments have shown t h a t increasing applicat ion of d i l u t e H2S04 has s ign i f i can t ly increased the ba- s a l area growth, Tanun e t a l . , (1980). The Norwe- gian s tudies cons is t of f i ve f i e l d p l o t experiments where a r t i f i c i a l r a in has been produced by mixing groundwater and H2S04 t o pH values from 6 t o 2. In one experiment with Scots pine, increas-ed height and diameter growth was observed i n 1976 and 1977 a t t he p l o t s supplied with 250 mm of water per year of pH 3 , 2.5 and 2. In 1979 however, the most ac id i f i ed p l o t s showed s ign i f i - can t ly l e s s growth than the o ther experiments. (See Abrahamsen 1980).

The experiments thus show increased growth the f i r s t couple of years i n the ac id i f i ed p l o t s , followed by decreased growth the l a s t year. Sim-i l a r pa t t e rns , though not s ign i f i can t , have been found i n some of the o ther experiments. Chemical analyses of the fo l iage have revealed t h a t the most l i k e l y explanation of the increased growth is increased N uptake. The decrease i n growth observed i n 1979 might be r e l a t ed t o reduced a-va i l ab l i t y of Mg a s t he f o l i a r concentration i s close t o values giving v isua l deficiency symptoms.

Short-term growth r e s u l t s from ac id i f i ca t i on experiments must be t r ea t ed with caution. They indica te , however, t h a t t r e e growth may be rea-sonably s t ab l e when the p lan t -so i l system i s s t ressed by ac id ra in . Another d i f f i c u l t y t o be kept i n mind i s t h a t p a r t of the ac id i ty of r a i n i s due t o n i t r i c ac id o r nitrogen oxides, which means t h a t the pos i t ive f e r t i l i z e r e f f e c t of nitrogen may p a r t l y o r f u l l y compensate f o r any harmful e f f ec t s .

Theoretically there might be cases where acid-i t y caused by sulphur oxides i s counteracted by f e r t i l i z e r e f f e c t s , s ince sulphur i s an indispen-sable p l an t nu t r ien t . However, deficiency i n sulphur has never been observed i n f o r e s t t r e e s under na tura l conditions i n Scandinavia, and con- s ider ing the ra ther t i g h t nu t r i en t c i r cu l a t i on i n the f o r e s t ecosystem, it i s not l i k e l y t o occur except possibly on very extreme s i t e s .

A number of possible e f f e c t s of acid r a i n on biological processes i n t he f o r e s t s o i l has been considered by Tam, (1976), Abrahamsen, (1980) . Most f o r e s t s o i l s have a considerable buf fer ca-paci ty. Therefore, we may assume t h a t the supply of ac id i ty , measured e i t h e r a s hydrogen ions o r a s "strong acid" of i n d u s t r i a l o r ig in , cannot ye t have a f fec ted the e n t i r e s o i l p r o f i l e , ex-cept possibly i n t he immediate v i c i n i t y of emis- s ion sources. S t i l l , e f f e c t s may be found on processes occurring i n t he top-soi l o r on the surface of s o i l pa r t i c l e s . So i l organisms, in-cluding roots , i n the upper s o i l horizons may a lso be affected. Soi l resp i ra t ion , ni t rogen

turnover which i s intimately connected t o organic matter decomposition i n s o i l , n i t r i f i ca t ion , ni-trogen fixation and nitrogen immobilization are some of the processes apparently affected by increasing s o i l acidity. There are a number of other biological processes which may be affected by a change i n s o i l ac idi ty or sulphur supply which have not yet been studied.

Several comparative and experimental investigations have yielded evidence i n support of the theoretical assumption tha t acidif ied precipita t ion, l i k e any other change i n climate, w i l l r e su l t i n changes i n the properties of so i l . In-fluences from t h i s changed chemical climate on s o i l conditions have been indicated through decreases i n pH and base saturation as well as increased leaching. From the studies performed up t o now, however, it is d i f f i c u l t t o draw any de- f i n i t e conclusions on the time required fo r the reactions and t h e i r in tens i t ies . Many s o i l s are f a r from the s table and mature stage, and it is a well-known fac t t h a t considerable changes due t o factors other than acid precipitat ion may si-multaneously be affecting the properties of the so i l . The great variation i n s o i l types and i n t h e i r suscept ib i l i ty t o acid precipitai ton make detection even more d i f f i c u l t before the expected e f fec t s have become extensive.

The re la t ive significance of strong acids and associated heavy metals found i n heavily polluted areas has not been c lear ly established i n terms of toxic e f fec t s on plants and s o i l organ- i s m s . The most serious consequence of regional acidif ication a t currently observed levels may be the increased ra te of leaching of major elements and t race metals from fores t s o i l s and vegetat ion. This is t rue fo r the fores t ecosystem and a lso has a bearing on the aquatic systems receiving these effluents.

Aquatic Ecosystems

Freshwater bodies i n many areas of northern Europe and eastern North America, t h a t today l i e i n and adjacent t o the areas where precipitat ion i s most acid, are threatened by the continued deposition and fur ther expansion of acid preci- p i ta t ion. Many of these bodies of fresh water are poorly buffered and vulnerable t o acid inputs. These ecosystems appear fated t o suffer ac idi f ica t ion and loss of f i sh populations. E-qually a s serious as damage t o f i sh are the l e s s conspicuous e f fec t s of the acidif ication of fresh water including changes occurring i n commu-n i t i e s of aquatic organisms such as microdecom- posers, algae, aquatic macrophytes, zooplankton and zoobenthos.

Water chemistry

The composition of the lakes which are discussed i n connection with acidif ication depends

on three principal sources of chemical components - atmospheric inputs of sea-water s a l t s , atmospher-i c inputs of acid precipitat ion and t e r r e s t r i a l inputs of chemical-weathering products.

Unpolluted, so f t water lakes are generally dilute solutions of Ca and Mg bicarbonate. The bicarbonate system consti tutes the main buffering system i n the water. Lakes i n regions underlain by highly res is tant , carbonate-poor rocks have lower buffer capacities, and are vulnerable t o the input of acid precipitat ion. A major number of the lakes i n Scandinavia f a l l within t h i s ca-tegory, especially above the postglacial marine l i m i t , where the bedrock over large areas i s covered by only th in g lacia l deposits. A contin-uous supply of acid substances t o lakes and streams eventually leads t o the depletion and loss of the normal buffer system. The pH f a l l s t o below 5.0, and sulphate becomes the major anion. Such lakes have only minimal capacity t o neural- i z e additional inputs of acid; and new inputs of acid cause sharp drops i n pH, Wright and Gjessing, (1976), Henriksen, (1980).

Acid precipitat ion also causes other changes i n lake water chemistry as well. The acidic, high sulphate lakes a lso have high aluminum concentrat ions. Since precipitat ion contains very l i t t l e A l l the A 1 i n the l a k e water must come from the drainage basins. That has been shown t o be the case i n investigations conducted on 9 small drainage basins i n southern Norway. It has been shown tha t loss of calcium, magnesium and aluminum from the basins is par t ly due t o natural wea-thering processes, but a major fraction probably resul ts from the massive inputs of acid precipitat ion. In grani t ic basins there i s approximate- l y equivalence between net H+ input and Ca + Mg + A 1 output.

The deposition of acid precipitat ion occurs epi-sodically. Acid precipitat ion generally causes two seasons of increased acidi ty i n streams and r ivers - the f a l l , a season of frequent rain, and the spring, when pollutants stored i n the snow-pack are released i n the f i r s t p a r t of snowmelt. Laboratory and f i e l d studies of polluted snow have shown tha t the f i r s t fractions of meltwater due t o concentration effects within the snowpack con- t a in higher concentrations of pollutants than the bulk snow. The f i r s t 30 per cent of the meltwater contains up t o 70 - 80 per cent of the t o t a l a-mount of H', ~ 0 ~ "and s ~ ~ ~ .

The episodic deposition of a i r pollutants and a certain temporary accumulation of sulphate i n the summer resu l t s i n major short-term increases i n the ac idi ty of lakes and r ivers and these changes are most frequent i n the f a l l and spring. From a biological point of view these periods are often c r i t i c a l because they are spawning and hatching seasons for many aquatic organisms.

Regional surveys

A large number of surveys have been conducted t o give a picture of the acidif ication of Scan- dinavian lakes and rivers. A systematic survey of 155 lakes i n southern Norway was conducted i n October 1974, and repeated every year since, on varying number of lakes.

Excess sulphate i s sulphate tha t does not come from sea water sa l t s . Although i n some lakes, t h i s excess sulphate comes from a t e r r e s t r i a l source i n the drainage basin, the regulari ty of a SE-NW gradient most probably i s due t o chronic inputs of anthropogenic sulphur through precipita t ion and dry deposition. Indeed, the d i s t r i - bution of excess sulphate i n lakes i s remarkably similar t o the weighted average concentration of excess sulphate measured i n precipitat ion over southern Norway.

The pH levels i n the lakes can be largely explained by inputs of acid precipitat ion i n the SE-NW gradient superimposed upon the variations i n buffer capacit ies due t o the geology of the drainage basin.

Aquatic organisms

Acid s t r e s s on l i f e i n r ivers and lakes has e f fec t s on a l l stages i n the food chain. Prima-ry producers communities, l ike phytoplankton, are simplified by a reduction i n the number of species. The composition of a community may a l t e r with a s h i f t t o more acid-tolerant species.

Macrophytic vegetation has been observed t o change i n ac idi f ied lakes. In some lakes Sphag- num occurs i n dense mats, and epiphytes are well developed. Generally, the vegetation i n acidi- f ied lakes i s poor i n species.

The same tendency of an acid-tolerant "shift is observed i n diatom communities i n 7 locations i n southern Norway described i n 1949 and revis i ted i n 1975. There was an increase i n the proportion of species which prefer o r require acid water.

In some acidi f ied lakes, an increased accumu-la t ion of organic bottom sediment has been observed, indicating a reduced ra te of decomposi-t ion. There are strong suggestions t h a t micro- b i a l decomposition is reduced i n acid water and t h a t slow-acting fungi take over. This w i l l in-fluence the nutrient exchange with the lake sediments.

In the invertebrate freshwater fauna the same trends are observed: a reduced number of species and a t o t a l reduction i n biomass i n the acid locations. Experiments on the tolerance of cer ta in crustaceans which are important as f i sh food (Gammarus l acus t r i s and Lepidurus t icus) have shown a d i rec t mortality of eggs a t pH 5.5 o r lower. There are a lso delays i n the

development from stage t o stage of surviving animals. Exposure below pH 5.5 w i l l k i l l a majority of adult individuals even a f t e r a short time, 1 - 2 days. In Norwegian lakes, snai ls are rare a t pH below 5.8 and disappear below 5.2.

In spi te of the strong e f fec t s on f i sh food organisms, the indications are tha t changes i n f i sh food supply play a small role i n the elimination of f i sh from acid r ivers and lakes. In-stead,lack of recruitment seems t o be the dominant factor. The tolerance against acid water i s low-e s t i n newly hatched larvae. This f ac t makes the spring flood a part icularly c r i t i c a l time for the f i sh population.

The physiological mechanism or mechanisms responsible fo r f i sh death i n acid water are not fu l ly understood,, but it has been well established tha t acid s t r e ss i s accompanied by a f a i l -ure i n s a l t regulation within the f i s h body. Metabolism and osmotic c e l l regulation seem t o be affected. It i s also quite clear tha t the s a l t uptake and loss i s influenced by the ion content of the water. Elevated concentrations of aluminum, manganese, zinc, cadmium, lead, cop-per, and nickel have frequently been observed i n acidif ied lakes. The abnormally high concentra- t ions are apparently due i n par t t o d i rec t depo- s i t ion with precipitat ion as well as t o increase release (solubil i ty) from the sediments. These metals may represent a major physiological s t r e s s fo r various aquatic organisms.

Fish population s t a t i s t i c s from nearly 1000 lakes i n southern Norway show tha t when both pH is low (e.9. pH 4.7) and sa l in i ty i s low (e.g. K 10 IJS cm) almost a l l lakes are empty of f ish. A t higher s a l i n i t y (K 20pS/cm) several lakes have sparce populations and a few even good.

The recent acidif ication of freshwater i n par ts of Europe and eastern North-America has profound impacts on aquatic l i f e . It can be s ta ted with r e l i a b i l i t y tha t a l l trophic levels are affected. Of immediate concern t o the people l iving i n the acidif ied regions i s the major decl ine i n f i sh populations. In the four southernmost counties i n Norway more than half of the f i sh populations have been l o s t during the 1940 -1980 period. Today, lakes i n more than 13,000 km2 of south Norway are pract ica l ly devoid of f i sh , and i n an additional 20,000 km2 the f i s h stocks are reduced. Continued water acidif ica- t ion i s a threat t o hundreds of lakes s t i l l har- bouring valuable f i sh populations(Muniz and Leivestad, 1980).

LITERATURE CITED

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fo re s t growth. In Proc. Internat ional con-ference on the ecological impact of acid p rec ip i t a t i on , Norway, March, 1980. SNSF,1432 Aas-NLH, Norway ( In press)

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1976. Ef fec ts of ac id p rec ip i t a t i on on coni-ferous fo re s t . In SNSF-project FR 6/76, SNSF, 1432 as-NL~ Norway

Dovland, H. and A. Semb. 1980. Atmospheric t ranspor t of po l lu tan ts .

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Henriksen , A. 1980. Acidif icat ion of freshwaters - a la rge

s ca l e t i t r a t i o n . In Proc. In te rna t iona l conference on the ecological impact of ac id p rec ip i t a t i on , Norway, March, 1980. SNSF, 1432 Aas-NLH, Norway (In press)

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pol lu t ion caused a growth reduction i n Swed- i s h fo re s t s ? A comparison between regions with d i f f e r en t s o i l propert ies . In Rapp. Uppsatser In s t . f o r skogproduktion, Skoghog-skolan, N r . 20, 48 p.

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Strand, L. 1980. The e f f e c t of ac id p rec ip i t a t i on on t h e

growth. In Proc. In te rna t iona l conference on the ecological impact of ac id prec ip i ta - t i on , Norway, March, 1980. SNSF, 1432 Aas-NLH, Norway ( In press)

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1980. Ef fec ts of a r t i f i c i a l a c id i f i ca t i on with sulphuric ac id on t r e e growth and s o i l chemis- t r y i n Scots Pine fo re s t . In Proc. In te r -nat ional conference on ecological impact of ac id p rec ip i t a t i on , Norway, March, 1980. SNSF, 1432 Aas-MLH, Norway ( In press )

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chemical 'composition of lakes. Ambio , 5 : 219.

The Impact of Acidic Precipitation and Heavy Metals on Soils in Relation to

Forest Ecosystems

2Stephen A. Norton, Denis W. Hanson, and Richard J. Campana

Abstract: Normal terrestrial cycling of metals in eastern North America and the Pacific Coast states has been altered by the increasing acidity of precipitation, and associated heavy metal deposition and mobilization. Pb and chemically similar metals are accumulating in soils. Al, Ca, K, Mg, and Mn are being leached from soils. The mobilities of Fe, Zn, and P vary with site characteristics. Biological recycling of nutrients by decomposition and uptake is impeded by lowered pH and elevated levels of toxic metals in soils. Increased leaching of nutrients in the 0 and A horizonscaused by increased H"1" inputs, decreases percent base saturation and thus decreases nutrient pools for shallow rooted plants, especially seedlings. Deeper rooted plants are subjected to elevated, potentially toxic, concentrations of dissolved metals (e.g., A1 and Mn). In many contemporary forest ecosystems, nutrient availability is barely adequate for sustained yield with bole harvesting techniques. Our work indicates that nutrient pools are dimin- ishing in the northeastern United States, suggesting that decreases in forest productivity will occur.

Large areas of the northern hemisphere are re- ranged up to about 8.2 (corresponding to semi- ceiving precipitation which is more acidic than arid to arid regions where CaC03 dust, or its would be predicted by equilibration of rain and equivalent, dominatesthe rain chemistry). atmospheric CO2:

Atmospheric concentrations of CO2 should result in a pH of about 8.2. In eastern North America, where vegetation cover minimizes particulate injection into the atmosphere, unpolluted precipitation would probably have a pH of about 5.6. Associated with the precipitation are numerous

The resulting pH should be about 5.6. This may be metals and plant nutrients (e.g., Na, K, Ca, Mg, modified by the hydrolysis of particulates or the NO;, NQ, H2P04, Pb, Zn, etc.). addition of naturally occurring.organic and inorganic acids. Precipitation pH's in the U.S., Precipitation (wet and dry) is one of three prior to pollution of the atmosphere, probably inputs into the nutrient budgets for forest eco-

systems. The others are chemical weathering of inorganic soil and nutrient cycling within the

presented at the Symposium on Effects of Air canopy/root space. Both are closely linked to Pollutants on Mediterranean and Temperate Forest precipitation chemistry. Ecosystems, June 22-27, 1980, Riverside, California, U.S.A. Simply put, from a nutritional point of view:

Professor and Chairman of Geological Sciences; Input - Output = Net accumulation of organic

M.S. degree candidate in Geological Sciences; material.

Professor of Botany and Plant Pathology; Univer- sity of Maine at Orono, Orono, Maine 04469. Output consists of leaching to groundwater (below

the root zone), injection of particulates into the atmosphere, volatilization of certain elements, and loss of particulates "downstream", including harvesting. If the mass balance (above) is positive for all limiting nutrients, growth and accumulation of organic matter will occur as living biomass or as soil organic matter. If the mass balance is negative, growth can occur only so long as the decreasing reservoirs of organic matter and nutrients from precipitation and chemical weathering can supply necessary nutrients; organic matter must decrease. The amount of organic material on the forest floor and contained in the rooting zone of the mineral soil is generally of the same order of magnitude orlarger than the organic material contained in the above ground biomass. Removal of this biomass disrupts the recycling of nutrients. Continued growth of new biomass must occur from the reservoir within the soil, forest floor, and from precipitation.

A forest ecosystem can subsist on nutrients de- livered solely by precipitation, both wet and dry (Art et al. 1974). However, it is doubtful that this precipitation-based forest ecosystem could be harvested periodically and still have sustained growth. If there are changes in the chemistry of precipitation, specific inputs/outputs of the forest nutrient budget may be altered so as to affect both sustained growth yields and net organic matter accumulation.

Many forest ecosystems are not forced to subsist on atmospheric inputs alone. They receive additional primary inputs of nutrients from chemical weathering of mineral matter. However, in unglaciated areas of the eastern U.S. where chemical weathering dominates over mechanical weathering or in glaciated granitic (nutrient poor) ter- rains characteristic of large areas of eastern North America, nutrient pools are largely contained within the organic litter of the forest floor. Thus, these areas are the most vulnerable to depletion of nutrient pools due to acidic precipitation.

Nutrient availability is commonly classified as deficient (where addition of the limiting nutrient elicits a positive response), adequate (where addition of a nutrient does not elicit a response), and excessive (where addition of the nutrient elicits a negative response). This paper investigates some of the consequences of increased acidity and metal availability, associated with acidic precipitation to nutrient availability (and thus to forest productivity). Excellent reviews of potential problems are given by Voigt (1979) and in Hutchin- son and Havas (1980).

EFFECTS OF DECREASED pH

Although early precipitation chemistry is sparse for North America, Cogbill and Likens (1974) constructed 3 pH isopleth maps spanning 1952 to 1972 which suggested increasing acidity for precipitation in the eastern U.S. and a broadening of the

Figure I~Generalized pH (dotted) (NADP 1979, 1980; CANSAP 1979),Pb (solid) and Zn (dashed) isopleths (Davis and Galloway 1980) for eastern U.S. precipitation. Fluxes are g/h/mo.

area receiving acidified precipitation. Recent data (NADP 1979; NADP 1980 a,b; CANSAP 1980) shows a continued decrease in the pH to average values of less than 4.0 for the "bull's eye"; the eastern half of the U.S. and the eastern half of southern Canada is receiving precipitation with a pH less than 5.0 (fig. 1).

Most of the lowering of the pH of precipitation from "normal" to present levels occurred over the last 40 years. In North America, there are no long term regional studies of the acidification of soils showing trends related to regional pH gradients. Linzon and Temple (1980) (in Ontario) found acidification of soils over a 16 year observation period. Many studies have been made of soil acidification and nutrient status in areas heavily affected by point sources.

Expected changes in the inorganic aspects of soil chemistry associated with acidification include desorption of metals from organic and inorganic cation exchange surfaces, increased solution of "mineral" colloids and crystalline minerals, and changes in metal speciation and thus biological availability.

Desorption of metals

Regardless of the nature of the substrate, ion exchange (for a monovalent ion) may be represented as

+where X i s an exchange s i t e , R i s any monovalent meta l , H+ is a proton, and aq r e f e r s t o an aqueous spec ie . Th i s r e a c t i o n can be fo rced i n e i t h e r d i - r e c t i o n by changing H"1' o r R+ a c t i v i t i e s .

P re -po l lu t ion p r e c i p i t a t i o n i n e a s t e r n North America e n t e r e d t h e s o i l w i t h a pH probably i n t h e r ange 5 .5 t o 6.0. Microbia l a c t i v i t y i n t h e organ ic l i t t e r produces molecular CO2 which can reduce t h e pH cons ide rab ly (as low a s 4.5 t o 5 .0) . The product ion of v a r i o u s o rgan ic weak a c i d s (e.g. f u l v i c and humic) may depress t h e pH f u r t h e r t o 4 .0 t o 4.5. To mainta in e l e c t r i c a l n e u t r a l i t y i n t h e s e s o l u t i o n s t o o f f s e t t h e ff4' product ion, e i -t h e r an ions must be gained ( H C O ~ a c t i v i t y i s re-duced by t h e lower ing of pH; o rgan ic an ions may be produced) o r c a t i o n s must be l o s t from t h e so-l u t i o n . Th i s i s most e f f e c t i v e l y accomplished i n t h e l i t t e r and a t r o o t s u r f a c e s where H+ i s ex-changed f o r p e r c o l a t i n g c a t i o n s . Thus n u t r i e n t s a r e gained by t h e s o i l .

I f t h e p r e c i p i t a t i o n has a pH of 4.0 due t o t h e s t r o n g a c i d s H2S04 and HN03, t h e exchange r e a c t i o n i s f o r c e d s t r o n g l y t o t h e r i g h t , s t r i p p i n g c a t i o n s ( p a r t i c u l a r l y Ca and Mg) from t h e l i t t e r , reducing pe rcen t of base s a t u r a t i o n . Continued p roduc t ion of CO2, o r g a n i c a c i d s , by mic rob ia l a c t i v i t y as- s u r e s t h a t t h e c a t i o n s a r e l o s t from t h e system.

No l o n g term s t u d i e s of s o i l s e x i s t t o demon- s t r a t e t h e swi t ch from accumulation t o l o s s of c a t i o n i c n u t r i e n t s a s a r e s u l t of low pH p r e c i p i - t a t i o n . I n d i r e c t evidence f o r t h e swi t ch c o n s i s t s of long term changes i n s u r f a c e water q u a l i t y such a s c o n d u c t i v i t y (Malmer 1976 [ i n wede en] ) , a l k a l i and a l k a l i e a r t h c o n c e n t r a t i o n s (Malmer 1976), and t h e commonly observed r e l a t i o n s h i p between non- d y s t r o p h i c low pH w a t e r s and e l e v a t e d Ca, Mg, Al, Mn, and o t h e r meta ls . U l r i c h (1980) and Linzon and Temple (1980) have shown l o s s of base sa tu ra -t i o n i n s o i l s over 8 and 16 y e a r s , r e s p e c t i v e l y . Abundant exper imenta l evidence (e .g . , Hutchinson 1980; Abrahamsen and Stuanes 1980) and s t u d i e s of s o i l s a d j a c e n t t o l a r g e p o i n t source e m i t t e r s of SOx and NOx suggest what long t e rm r e s u l t s might look l i k e . Ca, Mg, K, Zn, Cd, and Mn a r e r e a d i l y leached from l i t t e r . However, t h e pH l e v e l s em-ployed f o r exper imenta l work a r e commonly w e l l below what we might expect on a r e g i o n a l b a s i s . P rocesses o p e r a t i n g a t a pH <4.0 may n o t be e f fec - t i v e even over long p e r i o d s of t ime a t pH>5.0.

A t r a n s e c t of "equivalent" s o i l s i t e s a c r o s s a r e g i o n a l pH g r a d i e n t ( f i g . 2 ) , i n e f f e c t , i s a t ime s tudy of t h e e f f e c t s of low pH p r e c i p i t a t i o n . Table 1 i n d i c a t e s a p r o g r e s s i v e dec rease i n

and -i n a sou thwes te r ly d i r e c t i o n , to-A1203 A1203 ward lower pH p r e c i p i t a t i o n . We i n t e r p r e t t h i s a s a p r e f e r e n t i a l l e a c h i n g (deso rp t ion ) of Ca and Mn from t h e l i t t e r .

Organic m a t t e r i n l a k e sediment is de r ived from bo th t h e watershed and t h e l a k e water column. O r -gan ic - r i ch l a k e sediments i n a c i d i f i e d l a k e s i n New England (Will iams 1980) a r e d e p l e t e d of CaO,

Figure 2--Location of s o i l l o c a l i t i e s r e p o r t e d i n Table 1 (Hanson 1980) and l o c a t i o n of l a k e s f o r which Figure 4 i s developed. pH i s o p l e t h s a r e f o r 197516 (Likens e t a l . 1979).

a l s o sugges t ing t h a t f o r e s t l i t t e r i s be ing leached b e f o r e i t i s t r a n s p o r t e d t o t h e l a k e and/or t h a t l each ing con t inues whi l e t h e sediment i s i n con-t a c t w i t h a c i d i c l a k e wa te r .

So lu t ion of Metals from Minera ls o r Co l lo ids

The r e l e a s e of c a t i o n s from minera l s due t o a c i d i c s o i l water weather ing may be r ep resen ted

Table I ~ C h e m i s t r y of f o r e s t l i t t e r from h i g h a l t i t u d e f i r f o r e s t s . Sample s i t e s a r e shown on f i g u r e 2. Note: S i t e 6 i s anomalous f o r a l l parameters . S i t e 12 had abundant admixed mine ra l s o i l and t h e bedrock i s v e r y low i n MnO. D e t a i l s of c o l l e c t i o n and a n a l y s i s a r e i n Hanson (1980).

CaO MnO S i t e A ~ ~ O ?~ 1 . 7 0 3 Pb ( P P ~ ) Zn ( P P ~ )

1 7.62 0.21 189 72

PH Figure 3--Eh-pH diagram for the system Al-Te-Mn- 0-H20 at 2 5 " ~ and 1 atmosphere. Solubility in moles/I.

where R is a metal, n is the valence of the metal, Xxl is the stoichiometric formula for the mineral (minus R), H+ is a proton, and aq refers to aqueous species. Reactions of this type are forced by elevated H+ levels. MII+~-, ~e+2-, F~-^-Y and ~ l + ~ - bearing minerals are somewhat unique in that the respective metal's mobility is a function of [@I2 or even [&I3 activity and the transition from geochemical immobility to mobility under oxidizing conditions takes place at a pH between 4 and 6 (fig. 3).

Increased mobilization of A1 from inorganic soils has been documented by Cronan and Schofield (1979). Both experimental and field studies (Table 1) suggest that Mn is leached from upper levels of soils. Data are sparse but indicate that acidic non-dystrophic surface waters have elevated Mn levels. A1 and Mn have toxic effects on plants via root effects, and on aquatic animals. Fe, although leached somewhat by acidic percolating solutions (Cronan and Schofield 1979), is relatively enriched in the litter in leaching experiments and in the field (Hanson 1980). Downstream reduction in concentration of metals may be accomplished by dilution (Ca, Mg, K), precipitation (Fe, Al, Mn), and adsorption (P, Zn).

Overall, acidic precipitation accelerates pod- solization, expanding depths of upper soil horizons, and depleting thenutrient pool in the upper soil.

Changes in Speciation of Dissolved Metals

Biological uptake of nutrients and toxicants is via molecular diffusion through semi-permeable membranes which are somewhat specific to the species involved. Biological response is highly specific to the dissolved form ("biological availability") of the element.

Decreasing pH affects speciation in two ways. Elements which complex with OH groups will be preferentially partitioned into a less hydroxylated form. For example:

Lowered pH also results in protonation of weak acid radicals (e-g. HC03, fulvic , humic ) causing a decrease in ligands for the cation of interest. For example:

Because toxicity is generally greater for the uncomplexed metal (Hg is an exception), acidification of soil waters should result in greater direct toxicity to roots and micro-organisms or foliage after uptake, and on "downstream" ecosystems.

INCREASING TRACE METAL MOBILITY/AVAILABILITY

Trace metal levels, particularly heavy metals, are intimately affected by acidic precipitation in that their flux to the forest ecosystem is greatly increased over pre-pollution values and their mobility is in some cases greatly altered.

Historic data to evaluate the changing atmos- phericflux of heavy metals in North America is absent. Changes in fluxes with time in remote regions have been evaluated from snowlice cores (Cragin et al. 1975). Anthropogenic emission rates may be compared with natural emission rates to obtain an estimated percentage increase or mobilization factor. For Cd, Mn, Pb, and Zn the factors are 13, 0.48, 180, and 13 respectively. However, these factors may not relate closely to deposition values (Galloway et al. 1980), because of spatially non-homogeneous emission, dispersion, and deposition.

Limits on pre-pollution metal concentrations in precipitation may be established using modern data for precipitation chemistry from modern remote sites. Metal levels for eastern North Ameri- can must have been between the remote (Antarctica)

MRRRNR GRRNITE SPECK UNNRMED

Zn

u

PPÃ ICN. P M IGN. PPU IGN.

PPU IGN. PPH IGh. PPK IGh.

CONC. VS. DEPTH (CM)

Figure A--Pb and Zn p r o f i l e s f o r sediment from a circum-neutral (Maranacook), s l i g h t l y a c i d i c (pH, 5-6) (Gran i t e ) , and a c i d i c (pIK5) (Speck) l a k e wi th s u r f a c e i n l e t s and o u t l e t s and an a c i d i c (pH < 5 ) k e t t l e pond ("unnamed" Pond). Ponds a r e lo-ca ted on F igure 2.

and North A t l a n t i c va lues . (We know t h a t Green- l and [ c r a g i n e t a l . 19751 has been r e c e i v i n g p o l l u t e d p r e c i p i t a t i o n f o r approximately 200 y e a r s . ) Modern d e p o s i t i o n r a t e s f o r Pb and Zn a r e roughly known ( f i g . 1 ) . However, our poor knowledge of p re -po l lu t ion d e p o s i t i o n r a t e s doesn ' t permit a good assessment of t h e i n c r e a s e s t h a t have occurred f o r e a s t e r n North America.

Lake sediments r ecord changes i n atmospheric depos i t ion bu t normally no t i n a s t r a i g h t forward manner because of watershed e f f e c t s , sediment focus ing, and d i a g e n e s i s (Norton e t a l . 1980). .F ig - u r e 4 (unnamed Pond p r o f i l e ) sugges t s a minimum of an 800% and 200% i n c r e a s e f o r t h e depos i t ion r a t e f o r Pb and Zn, r e s p e c t i v e l y , over t h e l a s t 100 yea r s . These f i g u r e s assume t h a t t h e background l e v e l s (below 15-30 cm, depending on t h e l a k e ) a r e due t o atmospheric depos i t ion . However, most of t h e background concen t ra t ions a r e probably bedrock c o n t r i b u t i o n s . Based on i n c r e a s e s f o r Pb and Zn concen t ra t ions i n sediments from remote l a k e s i n New England, we e s t i m a t e t h a t atmospheric d e p o s i t i o n r a t e s i n New England have inc reased a t l e a s t by a f a c t o r of 30X. Pre-pol lu t ion concentra-t i o n s of heavy meta l s i n s o i l s a r e unknown. Shor t term s t u d i e s (Siccama e t a l . 1980) of heavy meta l s i n s o i l s i n d i c a t e t h a t concen t ra t ions a r e inc reas -i n g wi th t ime. Our d a t a ( f i g . 2, Table 1 ) shows a s t r o n g r e l a t i o n s h i p between t h e pH g r a d i e n t and Pb accumulation, c o n s i s t e n t wi th t h e Pb depos i t ion g r a d i e n t ( f i g . 1 ) . These concen t ra t ions a r e of concern w i t h r e s p e c t t o t o x i c e f f e c t s f o r s o i l mic rob ia l a c t i v i t y and n u t r i e n t cycl ing. High Pb concen t ra t ions i n l i t t e r a r e a l s o considered a s p o s s i b l e c o n t r o l s on t h e b i o l o g i c a l a v a i l a b i l i t y of phosphorus i n s o i l s (Cox and Raisons 1972).

However, even wi th e l eva ted depos i t ion r a t e s i t appears t h a t Zn (and o t h e r elements wi th s i m i -l a r chemical behavior) i s no t accumulating i n fo r -

e s t l i t t e r (Table 1 ) a l though b i o l o g i c a l l y a v a i l - a b l e B-horizon accumulation occurs (Conrad, p e r s . corn . ) . This appears t o be r e l a t e d t o inc reased l each ing of Zn from l i t t e r due t o decreasedpHof p r e c i p i t a t i o n ; l a k e sediments from New England e x h i b i t s i m i l a r behavior ( f i g . 4 ) . Ac id i f i ed watersheds have l a k e sediments being deposi ted which have l e s s Zn than sediments depos i t ed p r i o r t o t h e i r a c i d i f i c a t i o n .

SUMMARY

Acidic p r e c i p i t a t i o n , exper imental ly and em-p i r i c a l l y , a c c e l e r a t e s podso l i za t ion and d e p l e t e s n u t r i e n t pools i n f o r e s t l i t t e r and shal low inor - ganic s o i l s . Some heavy meta l s (e.g. Pb) accumu-l a t e t o concen t ra t ions which may impede b i o l o g i c a l s o i l processes and immobilize phosphorus. Other metals a r e mobilized (Al, Mn, Zn) and may a f f e c t ecosystems "downstream". Paleolirnnological and s o i l s d a t a from New England i n d i c a t e t h a t a c i d i - f i c a t i o n of dra inage b a s i n s ( inc lud ing s o i l s ) has occurred and n u t r i e n t d e p l e t i o n i s underway.

P a r t i a l suppor t f o r t h i s work came from t h e U.S. Nat ional Science Foundation g r a n t //DEB-78- 10641 t o S.A. Norton; t h e U.S. Dept. of t h e In- t e r i o r g ran t #14-31-001-4240, and t h e U.S. Dept. of t h e I n t e r i o r g ran t #AO26-W (Off ice of Water Resources and Research).

LITERATURE CITED

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Art, Henry W., F.H. Bormann, G.K. Voigt, and G.M. Woodwell. 1974. Barrier island forest ecosystem: Role of meteorologic nutrient inputs. Science. 184: 60-62.

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Cragin, J.H., M.M. Herron, and C.C. Langway, Jr. 1975. The chemistry of 700 years of precipitation at Dye 3, Greenland: CREEL Research Report 341, 18 p.

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Impact of Heavy Metals on Terrestrial and Aquatic Ecosystems1

2Tom C. Hutchinson

Abstract : The high t o x i c i t y of many metals and metal loids t o a wide range of b i o t a , coupled wi th t h e i r long res idence times i n t h e s o i l s , i n sediments and i n t h e oceans has l e d t o r e a l concern about t h e i r r o l e i n environmental de te r io ra - t i o n . Residence times i n watersheds a r e commonly measured i n hundreds of years , whi le res idence of metals i n a i r i s r a r e l y a s long a s s e v e r a l days. Overal l i n d u s t r i a l a c t i v i t y and t r a n s p o r t a t i o n l eads t o widespread metal d i spers ion . Major e leva t ions i n many metals occur around mines and smel ters and f o r l ead e s p e c i a l l y , alongside highways. Coal-burning and app l ica t ions of f e r t i l i s e r s and p e s t i c i d e s add metals t o a g r i c u l t u r a l s o i l s and t o n a t u r a l ecosystems. The s u r f a c e organic l a y e r s of both s o i l s and sediments a c t a s adsorpt ion and exchange s i t e s so t h a t major accumulations may occur. Yet, t h i s shallow organic l a y e r is t h e c r i t i c a l s i t e f o r many microbial a c t i v i t i e s , including those e s s e n t i a l f o r n u t r i e n t cycl ing, n i t rogen f i x a t i o n and f o r pathogens. Genetic and phys io log ica l to le rances a r e shown i n a wide a r r a y of d i f f e r e n t organisms which have survived i n metal- s t r e s s e d h a b i t a t s . 'Most recen t ly , ac id p r e c i p i t a t i o n has mobilised A l , Mn, Fe and Zn from the s o i l and sediment. These a r e now producing p a r t i c u l a r s t r e s s e s f o r a q u a t i c b i o t a .

The considerable t o x i c i t y of many metals t o b i o t a is w e l l known e.g. lead, mercury, cadmium, a r s e n i c . The q u a n t i t i e s mined and smelted f o r innumerable uses cont inues t o r i s e each year . It is apparent t h a t both n a t u r a l and man-made eco-

p r e s e n t e d a t t h e Symposium on E f f e c t s of Air P o l l u t a n t s on Mediterranean and Temperate Fores t Ecosystems, June 22-27? 1980, Rivers ide, C a l i f o r n i a , U.S.A.

~ r o f e s s o r of Botany and Fores t ry , Chairman, Dept. of Botany, Univers i ty of Toronto, Toronto, Ontario, Canada. M5S 1 A 1 .

systems a r e the r e c i p i e n t s of inc reas ing quanti- t i e s of these elements and t h a t we have t o be continuously v i g i l a n t t o ensure t h a t we do no t e i t h e r poison ourselves , our fe l low b i o t a , o r our a g r i c u l t u r a l and n a t u r a l ecosystems. Major human poisonings have occurred such a s t h a t by mercury i n Japan and i n I r a q , and t h a t of cadmium i n Japan. The beer-deaths i n Birmingham, England a t t h e t u r n of t h e century were a l s o bel ieved t o be metal- re la ted, being var ious ly asc r ibed t o a r s e n i c and/or selenium. Concern has a l s o been expressed about no t only the p o t e n t i a l f o r food chain contamination leading t o man b u t a l s o t o d i r e c t a e r i a l inpu ts t o man v i a t h e r e s p i r a t o r y t r a c t . Lead from automobile emissions where i t i s used a s an anti-knock i n gasol ine, and from primary and secondary smel te r s , a s w e l l a s many o ther smel ter-

-- -

emitted metals such as arsenic , copper, nickel , zinc, cadmium, antimony and selenium, a l l have po ten t ia l ly harmful consequences due t o t h e i r persis tence i n the body, and t h e i r a b i l i t y t o i n t e r f e r e with s p e c i f i c enzyme systems. It should a l s o be noted t h a t many instances a r e known of syne rg i s t i c and an tagonis t ic i n t e r ac t i ons between metals, both i n aquat ic and t e r r e s t r i a l systems and i n the human body. Notable amongst these a e the ameliorat ive e f f e c t s of seleniumfand a r sen i c on both mercury and cadmium toxic i ty i n mammals and t he recent ly described syne rg i s t i c e f f e c t s of ozone on cadmium and n icke l tox ic i ty i n c e r t a i n crop p lan ts , e.g. Parizek 1978, Levander 1977, Groth and others 1973, Czuba and Onnrod 1974. Nickel and copper synergisms Rave been described f o r a va r i e ty of b io t a , including freshwater un ice l lu la r a lgae, f l oa t i ng aquat ic p lan ts , and t r e e seedl ings, Hutchinson 1973, Hutchinson and Stokes 1975, Hutchinson and Czyrska 1972, and Hutchinson and Whitby 1974.

Despite what sometimes seems t o be a gloomy p ic ture with respec t to metal accumulations i n the environment, i t ought t o be borne i n mind t h a t concentration of a irborne pa r t i cu l a t e s i n urban and i n d u s t r i a l areas of Europe and North America have o f t en been much worse i n the past . Cohen and Ruston (1925) reported very high a r s en i c l eve l s i n the a i r of Leeds, England i n 1902-1910 due t o coa l burning, while the ove ra l l l eve l s of SO2 and ac id i c aerosols were much higher than present ly occur.

Residence Times and Watershed Loss

Rather l i t t l e a t t en t i on has been paid t o the residence times of metals i n components of the biosphere. The s t rong r e t en t i on of metals on the organic sur face layers of the s o i l and of the sediments is of g r ea t importance, i n t h a t i t causes long residence times a s we l l as i n allowing accumulation of metals t o po t en t i a l l y tox ic concentrations. Since i t is prec ise ly i n these sur face zones t h a t the major populations of microbes a r e located, and where the e s s e n t i a l processes take place of decomposition of organic matter , of ni t rogen f i x a t i o n and of elemental cycling e t c . Thus, the pers i s tence and accumulations of tox ic elements is of r e a l concern. L i t t e r i n urban areas contains elevated lead concentrations.

The r e t en t i on of t h e metals themselves i s an exchange process, with the elements behaving i n a reasonably pred ic t ive way, based on such proper t ies a s i on i c radius and e lec t ronega t iv i ty . Acid leaching can cause a downward movement of heavy metals through the p ro f i l e , s o t h a t they may en t e r ground water o r watershed streams. (e.g. Abrahamsen, Stuanes and Bjor 1979, Cronan and Schofield 1979, Hutchinson 1980, Bacon and Maas 1979 .) Both rock surfaces and s o i l s can cont r ibu te and such c lay -mineral cons t i tuen ts a s

aluminium, manganese, z inc and f e r r i c i r o n e n t e r drainage water i n t h i s way. Sediments can s imi la r ly l o se these same elements t o t he water bodies of lakes under ac id i fy ing conditions (Schindler and others 1980). The damaging e f f e c t of the r e su l t an t aluminium concentrations t o f i s h have been described by various authors , including Schofleld 1976, Baker and Schofield 1980, a t l eve l s as low a s 0.1-0.2 mg/1. Increased t ranspor t of aluminium In to aquat ic systems can a l s o a f f e c t phosphorus a v a i l a b i l i t y (Cronan and Schofield 1979).

The residence time of metals i n the a i r i s always very much shor te r than t h a t i n s o i l , water , sediments o r oceans. This is I l l u s t r a t e d by Table 1, which emphasises the r a the r l a r g e r residence time of lead i n a i r than t h a t of a wide range of o ther metals . This pa r t l y explains the elevat ions of l ead noted a t remote loca t ions , such a s i n the a r c t i c , i n g l a c i a l i c e i n Greenland and a t moun- t a i n tops i n Cal ifornia (see National Academy of Sciences Lead Review 1980). It i s a l s o a funct ion of pa r t i cu l a t e s i z e and p a r t i a l vapour pressure.

Table 1. Residence times1 of metals i n the atmosphere a t La J o l l a and Ensenada, from Hodge, Johnson and Goldberg, 1978.

days

L a J o l l a ' '1 ' Ensenada

7 8 0.7 0.5 0.2 0.1 0.4 0.3 0.5 1 3 0.8 1.2 0.2 1.0 0.4 0.8 0.2 0.8 0.4

0.6 1.0 0.2 5 ---1

Standing rop of metals on pa r t i cu l a t e s i n 1,000 m X 1 an3 column of a i r $f i l t e r data--Table 1 ) divided by the f l u x t o 1 cm of ground surface ("bucket da ta --Table 2) . F i l t e r da ta averaged over period during which buckets exposed. F i l t e r concentrations of Co, Fe, Mn, C r and A l h a v e been mul t ip l ied by 2 i n order t o account f o r the discr iminat ion aga ins t l a rge p a r t i c l e s by the H i -Vol sampler.

The contrast ing da ta f o r watershed s o i l s a r e i l l u s t r a t e d by Table 2, taken from Bowen 1975, and from which i t is apparent t h a t soil-watershed residence t i m e s a r e measured i n hundreds of years .

zTable 2 . Inputs and outputs i n mg X/m yr , and residence times i n years, f o r nine elements i n s o i l s of the Upper Thames basin.

Rain F e r t i l i z e r Rock Drainage Cropping Residence time/ X input input input output output years

Clearly the po t en t i a l f o r accumulation t o toxic l eve l s is much grea te r . The excess of lead and chromium i n input over output i s a f ea tu r e of systems subjected t o i n d u s t r i a l deposition. The v o l a t i l i z a t i o n of some of these heavy metals from the fo l i age of vegetat ion e.g. zinc, mercury, and selenium (Beauford and others 1975) may re-mobilise small quan t i t i e s of these metals and increase atmospheric residence times bu t i t w i l l not inf luence l o s s i n t o drainage waters. Allen and Steinnes (1979) determined t he regional d i s t r i b u t i o n of lead, z inc, cadmium, copper, arsenic , antimony and selenium i n Norwegian sur face s o i l s , u t i l i s i n g 500 humus samples. Lead leve ls were 10-fold higher i n the south than i n the a r c t i c a reas and a l s o higher along the coast than inland. Cadmium, arsenic , antimony and selenium showed a s imi l a r north-south trend. Al l of these elements a r e highly v o l a t i l e , low bo i l i ng point components of the atmospheric load from i n d u s t r i a l and urban centres .

Residence times i n s o i l water a r e a f fec ted t o a grea t ex ten t by pore s i z e . The water i n t he l a rge pores i n f i l t r a t e s i n t o lower layers and a i r en te rs again behind i t . The residence t i m e i n these pores is not more than hours. Meanwhile, the water i n t he narrow pores is displaced only centimetres o r mil l imetres . An example i s shown i n Table 3 from the work of F r i s s e l (19781, with residence times a s high a s 5000 years . The implicat ions f o r ground water contamination a r e apparent.

+Targets f o r H and Heavy Metals

I should l i k e t o emphasize t ha t one very usefu l way of considering t he po t en t i a l t h r ea t s t o ecosystems is through a considerat ion of t a r -ge ts i n the ecosystem. Clearly, a l l surface i n t e r f ace s f a l l i n t o t h i s category. Surfaces present areas of p o t e n t i a l accumulation o r residence. I n t e r r e s t r i a l ecosystems , including

ag r i cu l t u r a l ones, the sur face of the l e a f i s one such i n t e r f ace . Higher plants a r e covered by a r a the r impermeable waxy cu t i c l e , which reduces gas and water flow to a minimum but i s perforated by numerous stomata, o f t en on the underside of the leaf espec ia l ly . While pa r t i cu l a t e s can accumulate on such a surface, they a r e a l so r a t h e r e a s i l y washed off by r a i n or blown of f by wind. Frequently, however, small p a r t i c l e s can be incorporated i n t o the c u t i c l e o r en t e r the stomata. The leaf surface of many p lan ts a l s o a r e covered By numerous f i n e branched h a i r s o r glands. These can a c t as t r aps f o r pa r t i cu l a t e s s o t h a t very d i r t y leaf sur faces can occur i n areas of high dus t f a l l . Nevertheless, the d i r e c t l y tox ic e f f e c t s of pa r t i cu l a t e metal cons t i tuen ts a r e l imi ted a s they a re kept away from metabol ical ly a c t i v e s i t e s .

I n the mosses, l iverworts and l ichens, the c u t i c l e i s e f f ec t i ve ly absent. The exposed c e l l wal l sur face is a t the a i r i n t e r f ace and i t cons is t s of charged s i t e s , which can exchange both cat ions and anions. The metals a r e s e l ec t i ve ly exchanged onto t h i s surface and a r e held there. Large accumulations can take place. Lichens i n pol luted regions a t t e s t t o t h i s , as do mosses Ce.g. RUhling and Tyler 1970) . The use of Sphagnum moss bags a s a i r monitors is based on t h i s cat ion exchange capacity. The s p e c i a l sensi- t i v i t y of -many l ichens t o a i r po l lu tan ts is due t o the ready entry of t he po l lu tan t t o metabolically ac t i ve s i t e s .

S o i l Surface Layers a s Target Areas a t Risk

The surface of the s o i l a s a c r i t i c a l s i t e f o r accumulation of a irborne me ta l l i c contaminants has already Been re fe r red t o here . It is i n t h i s upper few centimetres of the s o i l t ha t nu t r i en t uptake i n t o p lan t roots takes place and i n which new root h a i r s a r e developed. Seeds germinate i n t h i s l ayer amongst the f o r e s t l i t t e r and seedl ings es tab l i sh there. The microbial sequences e s s e n t i a l

Table 3. Residence times of water i n the s a t u r a t e d zone of the s o i l .

Discharge per y e a r b u d

Estimated res idence time depending on t h e p lace of i n f i l t r a t i o n and on porosi ty of t h e s o i l o r rock

System and pathways

Watershed

About constant 100-500 years slow discharge 17 p a r t l y 12 slow discharge 12 1-500 years f a s t discharge 10 1 dayÃ‘1 years p a r t l y 12

Merkenf r i t zbach (Federal Republic of Germany, Land Hessen, Main a rea ) 1600 ha

10Ã‘100 y e a r s 1 d a y ~ 1 0years 1h o u r ~ lday

Okkenbroek (The Netherlands, I J s s e l a rea ) 443 ha

f o r e f f e c t i v e l i t t e r decomposition take place, i n t h i s zone pathogens s t r i v e t o i n f e c t seedl ings o r r o o t systems, and t h e mycorrhizal fungi e s s e n t i a l f o r e f f e c t i v e n u t r i t i o n of many f o r e s t t r e e s , e s p e c i a l l y i n t h e b o r e a l f o r e s t , develop here . The r h i z o b i a l b a c t e r i a which a c t as n i t rogen f i x e r s i n legumes and t h e actinomycetes and blue- greens which f u l f i l l t h i s r o l e i n o t h e r shrubs and grasses a l s o have t o i n f e c t roo t s i n these upper few cent imetres of t h e s o i l . Yet, onto t h i s s u r f a c e is being deposi ted inc reas ing loads of t o x i c heavy metals , of a c i d i f y i n g substances and a l s o of gaseous p o l l u t a n t s . The t h r e a t t o the s a f e funct ioning of such ecosystems and t o t h e well-being of man a r e focused on t h i s zone. Indeed, we can consider t h a t the reduct ion o r e l imina t ion of j u s t a few key processes could put t h e whole system a t r i s k . The enzyme a r y l su lpha tase which produces t h e plant-avai lable su lpha te from t h e non-available organic sulphur i n s o i l s i s one such s t e p , and i t i s known t h a t so i l -ex t rac ted a r y l su lpha tases a r e s u s c e p t i b l e t o a wide range of heavy metals inc lud ing aluminium. The a b i l i t y of r h i z o b i a l b a c t e r i a l t o i n f e c t legume r o o t s i s a l s o known t o be a c i d s e n s i t i v e and heavy metal suscep t ib le . The condi- t i o n s f o r s e e d l i n g es tabl ishment might be af f ected i f t h e atmospheric inpu ts of wet and dry deposi t ion were t o a c i d i f y s u r f a c e s o i l s s o a s t o favour fungi a t the expense of b a c t e r i a .

The t h r e a t t o l i t t e r decomposition may be a long time i n developing i n most a r e a s b u t i n those where i n t e n s e heavy metal accumulations have occurred from smelter emissions, examples of t h i s have al ready been demonstrated. I n both t h e remnant f o r e s t i n t h e major Sudbury smel t ing a r e a , where n i c k e l and copper concentrat ions have reached up t o 2000 ppm i n t h e p a s t and i n t h e New Lead B e l t of Missouri, where l ead , z inc, cadmium and

copper a r e now h igh , abnormal accumulations of l i t t e r on t h e f o r e s t a r e reported (Freedman and Hutchinson 1980, Watson and o t h e r s 1976). A t the z inc smel te r of Palmerton i n Pennsylvania, S t ro jan (1978) reported reduced decomposition of t h e f o l i a g e of a number of spec ies and asc r ibed i t t o e leva ted z inc and cadmium concentrat ions .

The r e p o r t s have a l s o included de t r imenta l e f f e c t s on a number of s o i l enzyme a c t i v i t i e s , on o v e r a l l mic rob ia l r e s p i r a t o r y a c t i v i t y and on micro-arthropod and earthworm ac t ion . Indeed, many repor t s a r e now a v a i l a b l e which show sensi- t i v i t y of earthworms t o heavy metal accumulations.

Sediments a s S i t e s of Risk

It should b e noted t h a t a r a t h e r s i m i l a r b u t p a r a l l e l case can b e made f o r e f f e c t s on s u r f a c e sediments. Again, i n t h i s zone, much of t h e microbial a c t i v i t y t akes place, t h e a q u a t i c p l a n t s have t o r o o t , t h e ben th ic organisms l i v e and reproduce and t h e important gas exchanges take place with t h e water column. This is the zone of depos i t ion of t h e dead planktonic organisms, of incoming p a r t i c u l a t e mat ter and of p o l l u t a n t m a t e r i a l equal ly . The sediments a r e o f t e n h igh ly organic and have a l a r g e ca t ion exchange capaci ty . Toxic l e v e l s can develop (mercury i n po l lu ted sediments of t h e D e t r o i t River and Lake S t . C l a i r ) , and benthic-feeding f i s h , clams, c rayf i sh e t c . come i n con tac t wi th p e s t i c i d e s , PCB's and heavy metals which have been i n i t i a l l y t ransported by a i r . The methylation t ransformat ion which c r e a t e s organic mercury compounds n ine t o t en times more tox ic than inorganic equivalents take p lace h e r e i n t h e sediment sur face l a y e r s .

Reproduction: c ruc i a l s teps a t r i s k

A number of e s s e n t i a l sequent ia l s teps can be i den t i f i ed , t he in te r fe rence with which places the whole reproductive process a t r i sk . These include a ) the hea l th of po l l ina tors , espec ia l ly the i n sec t s e s s e n t i a l f o r those plants with spec ia l i sed mechanisms and appropriate f l o r a l guides, t r i p mechanisms, nectar production, pol len posi t ioning etc . , b) the a b i l i t y of the pol len t o germinate successful ly on t he stigma and t o then success- f u l l y produce a pol len tube which can reach the un fe r t i l i s ed ovules c) the a b i l i t y of sperm t o successful ly reach and f e r t i l i s e the egg d) the a b i l i t y of p lan ts and animals t o successful ly disperse t h e i r progeny t o su i t ab l e new hab i t a t s .

I n t e r e s t i ng ly , i t is known tha t s teps a-c can a l l be a f fec ted by elevated l eve l s of heavy metals. For example, bees a r e known to be very suscept ib le t o airborne arsenic . I n the region of the Novatny power s t a t i o n i n Czechoslovakia bee hives have been wiped out. The power-station burns coa l with high l eve l s of a rsen ic i . e . severa l hundred ppm, and consequent elevated a i r l eve l s of As203 occur. Bees a l s o w i l l pick up and accumulate selenium when po l l i na t i ng high selenium plan ts , such a s some of t he loco-weeds (As t raga lus species) .

The success fu l growth of t h e pol len tube is reported t o be pH-dependent and a l s o t o be inÂ luenced by the presence of tox ic heavy metals such a s zinc and copper. The f e r t i l i z a t i o n of f e r n archegonia has been reported to be inh ib i ted by acid so lu t ions and ac id r a in , L. Evans, (personal communication) . L. Schl ic te r , a graduate s tudent i n botany a t University of Toronto, has recent ly shown t h a t t h e successful post- f e r t i l i z a t i o n s t eps i n embryo development of f rog eggs is inh ib i ted by even qu i t e minor decreases i n pH below 6.0 and t h a t mu l t i p l e - f e r t i l i z a t i on of an egg, which normally a r e precluded, can occur under these ac id i c conditions. The consequence is an ea r ly aborted embryo. Ef fec t s on t rou t eggs, on New Jersey f rogs and on reproductive success i n planktonic crustaceans have been reported by a number of workers, e.g. Krishna (1953), Gosner and Black (1957), Havas (1980).

Other Factors which Inf h e n c e the Outcome of Metal Impacts

It does seem to be the case t h a t the damage to ecosystems from airborne metals, a s we l l as from gaseous po l lu tan ts , i s g rea t e s t when the ind iv idua ls i n the ecosys tem are metabolically most a c t i ve . Thus, the damage t o f o r e s t eco-systems i n temperate zones is c l ea r ly g r ea t e s t i n the summer growing season. Damage during t he day when stomata a r e open Is grea te r than a t night when they a r e closed. The l ichens and mosses a r e most suscept ib le when they a r e moist and photo- synthesizing ac t i ve ly . I n dry o r a r i d hab i t a t s ,

such as the deser t s of Arizona, the damage from large smelter-emitted SO2 and copper pa r t i cu l a t e s is minimal i n cont ras t t o t h a t of wet te r areas such as Palmer ton Pennsylvania, Ducktown Tennessee or Sudbury, Ontario. This probably pa r t l y r e l a t e s t o metabolic a c t i v i t y including the percentage of time stomata remain open, but a l so t o the a c t i v i t y of the roo t systems. I f one follows through with t h i s general izat ion, then we can pred ic t t h a t a r c t i c regions with very s h o r t growing seasons and very long dormant periods w i l l be l e s s a f fec ted by equivalent metal pollu- t an t inputs (or SO?, O3 or F l inputs) than would Temperate o r espec ia l ly Tropic Rain Forest systems. Equally, one can pred ic t t h a t the more a r i d an area, the l e s s suscept ib le t h i s a r ea ' s vegetation w i l l be t o tox ic damage.

The importance of the longevity of t he individual a l s o needs t o be s t ressed . Damage t o long-lived trees- may take a long time t o become apparent and f i n a l l y perhaps only through t h e i r i n a b i l i t y t o reproduce. Equivalent reproductive f a i l u r e i n an annual w i l l obviously be very rapidly apparent. Metal s t r e s s e s of ten seem t o favour perennial p lan ts with la rge ly vegetat ive reproduction, such as grasses and sedges. The equivalent aquat ic examples would be t h a t of f i s h compared with planktonic algae or crustaceans.

F ina l ly , i t must be emphasised t h a t the i n i t i a l s e n s i t i v i t i e s of the species , populations and ind iv idua ls of an a rea when f i r s t subject t o meta l s t r e s s , a re no t the f i n a l response. While pre-adaptation o r p re -sens i t iv i ty may allow an i n i t i a l s e l ec t i on and so r t i ng , the s t r e s sed environment represents a changing h a b i t a t i n which evolutionary change occurs. The occurrence of metal- tolerant grasses on mine waste s i t e s i s we l l known. The a b i l i t y of some of these grasses t o evolve multiple-metal tolerances and co- tolerances is now a l s o receiving a t t en t i on (Tatsuyama- and o thers 1975, Cox and Hutchinson 1980J. Even i n hab i t a t s such as the Smoking H i l l s of a r c t i c Canada, where pond water pH's may reach a s low a s 1.8 and s o i l pH's t o < 3.0 from the i n i t i a l values of pH > 7.0, some organisms do survive. These even have the a b i l i t y to t o l e r a t e the high ac id i ty , low ni t rogen and phosphorus a v a i l a b i l i t y and the extremely elevated leve ls of normally tox ic metals such a s aluminium, manganese, f e r r i c ion and zinc, Hutchinson and others (1978). A t the extreme, some organisms seem t o have evolved spec i f i c a l l y on areas of very elevated metal l eve ls . The occurrence of a legume Becium homblei on copper mineral izat ions is an example of t h i s , i n which the p l an t accumulates enormous leve ls of copper and a l s o requires concentrations which would be l e t h a l to o ther p lan ts (Rei l ly 1967).

While t h i s allows a ce r t a in re-assurance about the a b i l i t y of l i f e to th r ive under even most adverse conditions, i t does not a t a l l inf luence

t h e f a c t t h a t we must b e extremely concerned with the a c c e l e r a t i n g l i b e r a t i o n of heavy metals t o our a g r i c u l t u r a l and n a t u r a l environments. Economic and s o c i a l pressures do compel us t o t ake s tock. Proposals f o r d i sposa l of metal-contaminated sewage s ludge on farm o r f o r e s t lands have al ready caused agencies and s c i e n t i s t s t o think i n a much longer time frame than we a r e used t o do.

Acknowledgments: I wish t o thank D r . A 1 Page of t h e S o i l Science Dep., Univers i ty of Ca l i fo rn ia , Rivers ide, f o r most use fu l discussions i n connec-t i o n with t h i s paper.

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Effects of Acidic Precipitation on Health and the Productivity of Forests1

Ellis B. Cowling and Leon S. Dochinger 2

Abstract: Acid precipitation has become a dominant feature of man-induced change in the chemical climate of the earth. But acid precipitation is only one special feature of the changing chemistry of atmospheric deposition in developed and developing regions throughout the world. In recent decades, human activities (mainly increased combustion of fossil fuels and decomposition or combustion of waste products) have greatly increased the total emissions and deposition of beneficial nutrients and injurious substances (such as strong mineral acids) from the atmosphere. Pro-jected increases in the use of fossil fuels, and especially in the use of coal, will add still further to the total burden of beneficial and injurious substances deposited on forest and rangeland ecosystems from the atmosphere. The purpose of this brief paper is to summarize certain important principles concerning the phenomena of acid precipitation and atmospheric deposition and their beneficial and detrimental effects on the health and productivity of forests.

The supply of both beneficial nutrientelements transpiration and the maintenance of cell and injurious substances in the atmosphere influ- turgor. ence the health and welfare of forests. Plant life as we know it would be impossible without Some epiphytic plants, such as orchids, atmospheric sources of carbon dioxide for photo- spanish moss, and certain lichens, obtain essen- synthesis, nitrogen for biological fixation and tially all their nutrients and water from the proteins synthesis, oxygen for respiration and atmosphere. Although these plants represent an synthesis of carbohydrates, and water for extreme case of dependence on atmospheric resources,

many forest trees and some herbaceous plants also derive a significant portion of their nutrients from the atmosphere.

presented at the Symposium on Effects of Air Plants suffer when the concentrations of inju- Pollutants on Mediterranean and Temperate Forest

rious substances in the atmosphere exceed the Ecosystems, June 22-27, 1980, Riverside, amounts they can tolerate. Injurious gases can California, U.S.A. enter through the stomata of leaf tissues and poison the photosynthetic system of living cells.

~ssociate Dean for Research, School of Toxic particles can accumulate on plant surfaces Forest Resources, North Carolina State Univer- and injure plant cells. Strong acids can dissolve sity, Raleigh. N. C.; and Project Leader, in rain drops or adsorb to snowflakes and then be Northeastern Forest Experiment Station, Forest deposited in precipitation. Dissolved substances Service, U. S. Department of Agriculture, can accumulate in snow where they may be concen- Delaware, Ohio. trated and released with the first meltwater. In

all these ways substances transferred from the atmosphere to the biosphere can influence plant growth, beneficially (as in the case of beneficial nutrient elements) or harmfully (as in the case of toxic gases, aerosols, dry particulate matter, and injurious substances dissolved in precipitation).

The growth and productivity of forests are determined by the availability of sixteen elements that are essential for growth and a few that are toxic to plants. The essential elements include nine major elements: carbon, hydrogen, oxygen, nitrogen, phosphorous, potassium, sulfur, calcium, and magnesium and seven minor elements: iron, copper, zinc, manganese, molybdenum, boron, and chlorine.

Some elements are both essential and injurious to plants. For example, sulfur and nitrogen are needed for synthesis of protein, nucleic acids, and other substances; hut gaseous sulfur and nitrogen oxides and sulfuric and nitric acid aerosols are also injurious to plants at very low concentrations. Similarly, excess amounts of the minor nutrient elements also can injure plants. Atmospheric fluoride is toxic to plants at 25-50 ppm. Aluminum is the most abundant potentially toxic element in soils. Its availability (and thus its toxicity) is influenced greatly by the acidity of soils, which in turn is influenced by the abundance of acid precipitation.

Uptake of nutrients from atmospheric sources is especially important in natural ecosystems such as lakes, estuaries, wetlands, forests, and rangelands where nutrients from other sources are scarce and where fertilization is not a normal management procedure. But this capacity also increases the vulnerability of terrestrial and aquatic organisms to injury by acid precipitation and toxic aerosols and gases (Galloway and others 1978).

ACID PRECIPITATION AS PART OF A GENERAL PHENOMENON 0F.ATMOSPHERIC DEPOSITION

Air-borne substances that influence terrestrial plants include sea spray from oceans and large lakes; dust resulting from wind erosion of soil as well as from volcanic and cosmic sources; gases such as CO2, NH3, SOy, H2S, CH4, released from decomposing organic matter and volcanoes; biogenic particles such as spores, hyphal frag- ments, bacteria, and pollen; particulate matter, aerosols, and gases produced by wild fires and controlled burning of agricultural, forest and urban wastes as well as from industrial, agricultural residential and commercial heating, and transportation operations (Tam 1958).

Rain and snow change in chemical composition within, as well as between, precipitation events. In cold climates, acid substances accumulate in the snowpack where they are released in concentrated form with the first melt water and thus

cause very sudden increases in acidity of surface soils, vegetation, and surface waters. Thus a given plant may be subject to beneficial atmospheric influences at one time and to negative influences at another time within a given day, month, growing season, or the years of its development in the case of perennial plants and animals. Even a given substance, such as sulfur or nitrogen dioxides, may be absorbed and utilized as a beneficial nutrient at one concentration in the atmosphere. At another, higher concentration, even on the same day, however, the same substance may be absorbed and found to be toxic or even injurious to the very same plant.

Forests and rangelands cover a larger fraction of the total land area of the United States than all other uses of land combined. For this reason, terrestrial vegetation, soils, and surface waters are the primary deposition sites for precipitation and airborne particulate matter of all types. Trees develop very large canopies of leaves and branches that extend high into the air. Thus, forests and range plants provide an extremely large surface for deposition and assimilation of both beneficial nutrient elements and injurious substances dispersed in the atmosphere.

Direct injury to vegetation is most likely when a particularly vulnerable life form is exposed at a particularly vulnerable life stage, and is growing in a poorly buffered environment during a season of the year when acid precipitation is most likely. For example, a tender young plant, at the earliest stage of reproduction, growing on a poorly buffered sandy soil, during a heavy spring rain is especially vulnerable to acid rain.

Both herbaceous and perennial plants are subject to changes in atmospheric deposition within a given growing season. In addition, perennial shrubs and trees live in the same environment for many years or even decades. As a result, they are subject to very long-term changes in the chemistry of the air and precipitation.

The effect of acid precipitation on plants is only one facet of the much larger subject of atmospheric/plant/soil interactions. Acidity in precipitation should be understood as a reflection not only of the amounts of substances yielding hydrogen ions (such as sulfuric, nitric, hydrochloric, and organic acids) but also of the total balance between all the cations and anions dissolved in precipitation. These major anions and cations include W-, NH4+, NO3-, SO4= and many others including K+, Na+, Ca*, Mg*, C03-, Cl-, and PO .

For all of the above reasons, it is difficult to assess the effects of acids in rain or snow in isolation from the general chemistry of precipitation and atmospheric deposition. Also, the effects of a given "acid rain" or a prevailing condition of "acid rains" are very complex,

variable in time, and involve significant interactions that are only partially understood.

POSSIBLE DETRIMENTAL EFFECTS OF ACID PRECIPITATION ON VEGETATION

A partial list of theoretical effects of acid precipitation on vegetation was developed earlier by Tam and Cowling (1977) and is reproduced in Table 1. The effects are classified as either direct or indirect, although most direct effects will have many indirect consequences as well.. A decreased rate of growth is the expected consequence of most of the effects postulated in Table 1 but unequivocal evidence of significant growth effects have yet to be demonstrated in forest or range ecosystems. Specific biological effects that have been proven to occur in at least one experimental plant are marked with an asterisk (*) in Table 1.

Many factors (i.e., genetic composition, biotic and abiotic stress factors, dose of pollutant, and pollutant combinations) affect the impact of acid precipitation and other pollutants on terrestrial plants and animals. Variation fn any one factor can result in variation in the nature and magnitude of pollutant effects. This is shown simplis- tically in Figure 1.

Previously, it was believed that the essential and potentially toxic elements listed above were taken up by plants almost entirely from the soil solution. Now, it is recognized that airborne gases, particulate matter, and aerosols significantly augment the supply of both essential and injurious elements. All of the substances

POLLUTANT CONCENTRATION

NUMBER OF DURATION OF EXPOSURES -I

DOSE -*Ã‘Ã‘'Ã EACH EXPOSURE

EDAPHIC FACTORS Ã‘

MECHANISM OF ACTION

7

ACUTE CHRONIC SUBTLE

Figure 1. Conceptual model of factors involved in air pollution effects on vegetation (Heck and others 1977).

listed above can be taken up readily through foliar organs as well as by absorption from the soil solution (Tam 1958; Wittwer and Bukovac 1969).

Much larger amounts of essential nutrients are required for sustained-yield agriculture than for sustained-yield range management or hardwood or softwood forestry. This is true in rangelands because biomass yields are very low and in forests because the parts of trees that usually are harvested(thewood and bark of treestems) contain much less of most essential elements than the seeds and fruits that are commonly harvested in agriculture. This is a major reason why fertilization is so common in agriculture and so rare in forestry and range management. In some forested regions, atmospheric deposition alone is more than adequate to permit harvesting of crop after crop of trees without fertilizing the forest. This is much less likely to remain so, as more and more of the nutrient-rich branches, foliage, and roots of trees are harvested in so-called "whole-tree chipping" 2nd other modern harvesting practices.

Some scientists believe that acid rain and snow are deposited directly onto soils where acid substances can be neutralized in well- buffered soils or by applications of lime. This is true on some agricultural lands, especially after harvest, but is not true in forests, rangelands, or even on most agricultural lands during the growing season. Most raindrops are intercepted by the foliage of plants where substances dissolved in rain can induce various physiological changes before reaching the soil (see Table 1). In a mature forest, for example, rain will wash over at least three tiers of foliage before reaching the soil.

SOURCES, AMOUNTS, AND DISTANCES OF TRANSPORT OF BENEFICIAL AND INJURIOUS

SUBSTANCES IN THE ATMOSPHERE

Forest, range, and aquatic biologists are becoming increasingly concerned about atmospheric transport and deposition of both nutritionally beneficial and potentially injurious substances for three major reasons :

(1) vegetation, soils, and surface waters are the primary deposition sites for precipitation and airborne particulate matter;

(2) atmospheric deposition constitutes an important source of nutrients and potentially injurious substances that affect the productivity and stability of agricultural, forest, and aquatic ecosystems; and

(3) human activities are steadily increasing the amounts and variety of substances dispersed in the atmosphere (Oden 1968; Bolin and others 1972).

Table I - -Potent ia l E f f e c t s of Acid P r e c i p i t a t i o n on T e r r e s t r i a l Vegetation

DIRECT EFFECTS

*1. Damage t o p r o t e c t i v e s u r f a c e s t r u c t u r e s such a s c u t i c l e . Damage t o sur face s t r u c t u r e s may occur due t o acce le ra ted e ros ion of t h e c u t i c u l a r l a y e r t h a t p r o t e c t s most f o l i a r organs. It a l s o could r e s u l t from d i r e c t i n j u r y t o sur face c e l l s by high concentrat ions of s u l f u r i c ac id and o t h e r harmful substances t h a t a r e concentrated by evaporation o r adherence of soot p a r t i c l e s on p l a n t su r faces .

*2. I n t e r f e r e n c e with normal funct ions of guard c e l l s . Malfunction of guard c e l l s w i l l l ead t o l o s s of c o n t r o l of stomata and thus a l t e r e d r a t e s of t r a n s p i r a t i o n and gas-exchange processes and poss ib ly increased s u s c e p t i b i l i t y t o pene t ra t ion by lea f -a t t ack ing p l a n t pathogens.

*3. Poisoning of p l a n t c e l l s a f t e r d i f f u s i o n of a c i d i c substances through stomata o r c u t i c l e . This could l ead t o development of n e c r o t i c o r senescent spo t s on f o l i a r organs including leaves , f lowers , twigs , and branches.

*4. Disturbance of normal metabolism o r growth processes without necros i s of p l a n t c e l l s . Such dis turbance may lead t o decreased photosynthet ic e f f i c i e n c y , a l t e r e d r e s p i r a t o r y p a t t e r n s and intermediary metabo l i sm,aswel l a s abnormal development o r premature senescence of l eaves o r o t h e r organs.

*5. A l t e r a t i o n of l e a f - and root-exudation processes. Such a l t e r a t i o n s may lead t o changes i n populat ions of l ea f - sur face and root-surface microorganisms, including ni t rogen-f ixing organisms.

*6. I n t e r f e r e n c e with reproduction processes. Such i n t e r f e r e n c e may be achieved by decreasing t h e v i a b i l i t y of po l len , i n t e r f e r e n c e with f e r t i l i z a t i o n , decreased f r u i t o r seed production, decreased germinab i l i ty of seeds , e t c .

7. Synerg i s t i c i n t e r a c t i o n with o ther environmental s t r e s s f a c t o r s . Such re in forc ing i n t e r - a c t i o n s may occur with gaseous s u l f u r dioxide, ozone, f l u o r i d e , soot p a r t i c l e s , and o t h e r a i r p o l l u t a n t s a s w e l l a s drought, f looding, e t c .

INDIRECT EFFECTS

*l. Accelerated leaching of substances from f o l i a r organs. Damage t o c u t i c l e and s u r f a c e c e l l s may l e a d t o acce le ra ted leaching of mineral elements and organic substances from leaves , twigs, branches, and s t e m s .

2. Increased s u s c e p t i b i l i t y t o drought and o ther environmental s t r e s s f a c t o r s . Erosion of c u t i c l e , i n t e r f e r e n c e with normal funct ioning of guard c e l l s , and d i r e c t i n j u r y t o s u r f a c e c e l l s may lead t o increased evapotranspirat ion from f o l i a r organs and v u l n e r a b i l i t y t o drought, a i r p o l l u t a n t s , and o t h e r environmental s t r e s s f a c t o r s .

* 3 . A l t e r a t i o n of symbiotic assoc ia t ions . Changes i n l ea f - and root-exudation processes and acce le ra ted leaching of organic and inorganic substances from p l a n t s may a f f e c t t h e formation, development, balance, and func t ion of symbiotic a s s o c i a t i o n s , such a s mycorrhizae, nitrogen- f i x i n g organisms, l i c h e n s , e t c .

*4. A l t e r a t i o n of hos t -paras i t e i n t e r a c t i o n s . Resistance and/or s u s c e p t i b i l i t y t o b i o t i c pathogens, p a r a s i t e s , and i n s e c t s may be a l t e r e d by sub jec t ing p l a n t s t o any environmental stress. Acid p r e c i p i t a t i o n may increase t h e s u s c e p t i b i l i t y of p l a n t s t o these i n j u r i o u s agen ts , a l t e r t h e i r capac i ty t o t o l e r a t e d i sease o r i n j u r y , o r a l t e r t h e v i ru lence of pathogens. The e f f e c t s of a c i d i c p r e c i p i t a t i o n may vary with t h e following: t h e na ture of t h e pathogen involved (whether a fungus, bacterium, mycoplasma, v i r u s , nematode, p a r a s i t i c seed p l a n t , i n s e c t , o r multiple-pathogen complex); t h e spec ies , age and physiological s t a t u s of t h e h o s t ; and t h e s t a g e i n t h e d i s e a s e cyc le i n which t h e a c i d i c s t r e s s is appled, f o r example, a c i d i c r a i n might decrease t h e i n f e c t i v e capaci ty of b a c t e r i a before i n f e c t i o n and increase t h e s u s c e p t i b i l i t y of t h e hos t t o d i sease development a f t e r i n f e c t i o n .

Source: Tamm and Cowling, 1977

Recent increases in the deposition of substances on terrestrial vegetation are due mainly to increases in combustion of fossil fuels in industrial enterprises, residential heating, transportation, and agricultural operations. Previously, it was believed that most of these materials fell out of the atmosphere near the site of emission. Now it is recognized, particularly with increased use of tall stacks at power plants, that atmospheric processes can lead to extensive mixing and both chemical and physical interactions and transformations of atmospheric particles, aerosols, and gases. Furthermore, these substances and their reaction products are dispersed by meteorological processes and finally are deposited on vegetation or soils as much as several hundreds of kilometers from the original sources of emission. The recent fallout of radioactive materials in the eastern United States as the result of atomic explosions in the Peoples Republic of China provides a dramatic reminder of the long-distance transport and deposition of pollutants.

The amounts of substances introduced delib- erately or inadvertently by man are becoming so large that man is becoming a major force in the biogeochemistry of the earth (Kovda 1975). This is shown in table 2 which contains a tabulation of data on annual outpuG of fertilizers, industrial dusts, garbage and other urban wastes and by-products, mine refuse, and discharges of aerosols and gases mainly from the combustion of fossil fuels. All these categories of matter are becoming comparable in magnitude to the discharges of dissolved and suspended substances in all the rivers of the world, the annual yield of photosynthetic products, or the cycling of inorganic elements in the earth as a whole. Man-made emissions into the atmosphere are also

Table 2--Biogeochemical and Technological Forces in the Biosphere of the Earth

Biosphere Components Tons /Year: .

Biogeochemical processes: Global yield of photosynthesis Cycle of inorganic elements

River discharges: Dissolved substances Suspended substances

Anthropogenic sources: Output of fertilizers Industrial dust Garbage, urban wastes and byproducts

Mine refuse Aerosols and gas discharges

Source: Kovda, 1975

very large, as shown in table 3. Most gases, carbon oxides, and aerosols result from the combustion of fossil fuels. A very large part of these global emissions are produced in the United States.

If the United States continues to add to the amount of substances dispersed in the atmosphere and deposited into the biosphere of the earth, it is essential that we measure the amount and chemical form of the deposited matter and understand the biological consequences of that deposition. Regret-tably our understanding of these processes in the United States is very fragmentary. Fortunately, however, more extensive measurements of atmospheric deposition and its biological consequences have been made in Europe, where an atmospheric-deposition network has been maintained since the late 1940s (Oden 1968).

The European Air Chemistry Network began in Sweden and has gradually spread to include most of western Europe and parts of eastern Europe, including Poland and the Soviet Union. Since the mid 19501s, a network of about 100 stations has made monthly measurements of changes in the chemistry of precipitation. The substances analyzed at most of these stations include the following major cations and anions: NH4, Na, Ca, K, Mg, 804, NO3, PO4, Cl as well as pH, conductivity, and titratable acidity and akla- Unity. These data have shown various long-term trends. for example, the amount of nitrate nitrogen in precipitation (an important fertilizer element) increased markedly in many parts of Europe during the fifteen years between 1955 and 1970. Nitrate nitrogen helps plants grow. Thus, the nitrogen added in precipitation probably increased yields of agricultural and forest crops.

But not all the substances detected in precipitation were beneficial. Long-term trends of injurious sulfate and hydrogen ions also were detected from 1955-1970. The latter changes were attributed to strong acids formed in the atmosphere, mainly from oxides of sulfur and nitrogen produced during combustion of fossil fuels. More recent data show that thesetrends of Increasing acidity are

Table 3--Anthropogenic Emissions into the Atmosphere

Types of Emissions I~onsf~ear I

Dust 2.5 x lo8 Gases (mainly .SOg, HC and NO) Carbon oxides (CO + C02) Aerosols

6.5 x lo8 2.0 lo9 1.0 x 10 9

Note: Doubling about every 7-10 years

Source: Kovda, 1975

continuing although t h e r e l a t i v e con t r ibu t ion of s u l f u r i c and n i t r i c a c i d s is changing (Likens 1976).

CHANGES I N THE CHEMISTRY OF PRECIPITATION I N THE UNITED STATES

Some monitoring of t h e chemistry of p rec ip i - t a t i o n has been c a r r i e d on i n t h e United S t a t e s (Feth and o t h e r s 1964; Lodge and o thers 1968). Many of t h e s e s t u d i e s provide e x c e l l e n t and r e l i a b l e information about t h e a c i d i t y of p rec ip i - t a t i o n . But most s t u d i e s i n t h i s country have suf fe red from t h r e e major shortcomings:

1. The d a t a were c o l l e c t e d f o r a l imi ted land a r e a ~ t y p i c a l l y only a s i n g l e po in t o r a few p o i n t s i n one o r two s t a t e s (Gambell and Fisher 1966);

2. The d a t a were co l lec ted f o r very l imi ted per iods of t i m e ~ t y p i c a l l y only one o r two years ;

3. Very few d i r e c t measurements of a c i d i t y have been made.

There i s only one l o c a t i o n i n t h e United S t a t e s ~ a tHubbard Brook Experiment Forest i n New Hampshi re~where t h e a c i d i t y of r a i n has been measured d i r e c t l y and c o n s i s t e n t l y f o r a s long a s 10 years . The longest-term n a t i o n a l monitoring program was operated by t h e U.S. Publ ic Health Service f o r 6 y e a r s , from 1960 t o 1966 (Lodge and o t h e r s 1968). These d a t a showed t h a t p r e c i p i t a t i o n genera l ly i s a c i d i c e a s t and genera l ly a l k a l i n e west of t h e Miss i s s ipp i River, t h e l a t t e r because of a l k a l i n e dust i n t h e a i r .

Using fragmentary b i t s of information, obtained i n d i r e c t l y and i n l i m i t e d a r e a s and per iods of t ime, Cogbi l l and Likens (1974) managed t o c a l c u l a t e t h e probable changes i n average a c i d i t y of r a i n f a l l i n var ious p a r t s of t h e e a s t e r n United S t a t e s from 1955-1973. 'P rec ip i -t a t i o n i n a l a r g e por t ion of t h e e a s t e r n United S t a t e s was l e s s than pH 5.6 i n 1955-56; t h e zone of g r e a t e s t a c i d i t y (lowest pH) was genera l ly c o n s i s t e n t wi th t h e zone where s u l f u r emissions were high--parts of Ohio, Pennsylvania, West Vi rg in ia , New York, and New England. By 1973, however, t h e a r e a with an average pH of r a i n below 4.5 had extended t o include p a r t s of Missouri, Arkansas, Miss i s s ipp i , Alabama, Georgia, South Carol ina, Virginia , Kentucky, I l l i n o i s , Michigan, and f u r t h e r n o r t h i n t o New England and Canada. E s s e n t i a l l y , i t embraces most of t h e a r e a e a s t of t h e Miss i s s ipp i River. Ind iv idua l ra instorms with pH values between 2.1 and 3.6 have been reported i n New York, I l l i n o i s , Indiana, New Hampshire, Massachusetts and North C a r o l i n a ~ i nsome cases many hundreds of k i lo - meters from major sources of a i r p o l l u t i o n (Likens 1976).

The r e l a t i v e con t r ibu t ion of s u l f a t e and n i t r a t e t o t h e t o t a l a c i d i t y of p r e c i p i t a t i o n

apparent ly changed markedly during t h e years s i n c e 1964-65. A t Hubbard Brook, New Hampshire, t h e r a t i o of s u l f a t e t o n i t r a t e changed from 83:15 i n 1964 t o 66:30 i n 1974. During t h i s same decade, t h e t o t a l input of hydrogen ions increased by 36 pet . Thus, most of t h i s inc rease appears t o be due t o increased deposi t ion of n i t r i c ac id .

EFFECTS OF ACID PRECIPITATION ON TERRESTRIAL ECOSYSTEMS

Cowling (1980a, 1980b) has recen t ly completed 2 h i s t o r i c a l analyses of progress i n s c i e n t i f i c and publ ic understanding of ac id p r e c i p i t a t i o n and i t s b i o l o g i c a l consequences. Several pub1i.- ca t ions a r e worthy of s p e c i a l n o t i c e i n t h i s connection. The pioneer ing researches by Robert Smith. E v i l l e Gorham and Svante Oden d e a l t wi th e f f e c t s on l ake wate rs , aqua t ic vege ta t ion , t e r r e s t r i a l vege ta t ion , andhuman h e a l t h (Smith 1872: Gorham 1958, 1976: Oden 1968). I n 1971. Bolin and h i s co-workers completed t h e Swedish Case Study Contribution t o t h e United Nations' Conference on t h e Human Environment (Bolin and o thers 1972). I n 1972, t h r e e Norwegian research organizat ions es tab l i shed a s p e c i a l research pro jec t c a l l e d Acid P r e c i p i t a t i o n : E f f e c t s on Forests and Fish, wi th an annual budget of 10,000,000 Norwegian kroner (U. S. $2,000,000). The f i r s t I n t e r n a t i o n a l Conference on Acid P r e c i p i t a t i o n and t h e Forest Ecosystem was he ld a t Ohio S t a t e Univers i ty a t Columbus i n May of 1975 (Dochinger-and Se l iga 1976a). I n June of 1976, an I n t e r n a t i o n a l Conference on E f f e c t s of Acid P r e c i p i t a t i o n was held a t Telemark, Norway, and t h e major papers assembled f o r t h i s meeting published by Braekke (1976) and i n a s p e c i a l i s s u e of Ambio (1976). I n November, 1976, Gene Likens published h i s summary repor t i n Chemical and Engineering News (Likens 1976). In May. 1978, a NATO Advanced Research I n s t i t u t e on Ecological Ef fec t s of Acid P r e c i p i t a t i o n was held a t Toronto, Canada (Hutchinson and Havas 1980). In September, 1978, t h e Central E l e c t r i c i t y Generating Board i n England and t h e E l e c t r i c Power Research I n s t i t u t e i n t h e United S t a t e s sponsored an i n t e r n a t i o n a l symposium on t h e b i o l o g i c a l e f f e c t s of ac id p r e c i p i t a t i o n (Howells 1979). In March, 1980, t h e Norwegian s p e c i a l p r o j e c t on ac id p r e c i p i t a t i o n sponsored an I n t e r n a t i o n a l Conference on E f f e c t s of Acid P r e c i p i t a t i o n i n Sandefjord, Norway (SNSF 1980).

The e f f e c t s of ac id p r e c i p i t a t i o n on t e r r e s t r i a l ecosystems genera l ly have been l e s s w e l l documented than those on populations of f reshwater f i s h and o t h e r aqua t ic organisms (Ambio 1976; Braekke 1976). Nevertheless, c e r t a i n d e f i n i t e e f f e c t s have been reported. The most s t r i k i n g of these e f f e c t s was t h e development of peat moss (Sphagnum s p . ) a s a submarine, r a t h e r than a t e r r e s t r i a l p l a n t i n a c i d i f i e d l akes and streams i n Sweden. Dense mats of Sphagnum and heavy f e l t s of a lgae develop on t h e bottom of these l akes i n water a s deep a s 18 m. This growth is reported by Grahn and o thers (1974) t o induce o l igo t roph ica t ion (opposite of eutrophication)--a s e l f - a c c e l e r a t i n g

process that leads to a substantial nutrient impoverishment of lake waters.

Analyses of forest growth in southern Sweden from 1896 to 1965 showed a 2 to 7 percent decrease in growth between 1950 and 1965. Johnsson and Sundberg (1972) "found no good reason for attrib- uting [this] reduction in growth to any cause other than acidification." Similar attempts to quantify possible effects on growth of forests in the United States have been inconclusive.

Both direct and indirect damage to crops and forests have been reported by various investigators in laboratory, greenhouse, and field experiments in which synthetic rain equivalent in chemical composition and rate of deposition to natural rains has been applied. The biological effects recorded in these experiments include the fol3.owing (Cowling 1980c) :

--Induction of necrotic lesions on foliage; --Loss of nutrients due to leaching from leaves and other foliar organs;

--Predisposition of plants to infection by bacterial and fungal pathogens;

--Accelerated erosion of waxes on leaf surfaces; --Inhibition of nodulation of legumes leading to decreased fixation of nitrogen by symbiotic bacteria; and

--Reduced rates of decomposition of leaf litter leading to decreased mineralization of organically-bound nutrients.

Abrahamsen (1980) has recently summarized many years of research showing both positive and negative effects of acid precipitation on forest growth. He concludes with the following general statements: "Apart from possible direct effects of acid precipitation on forest trees, the effects on forest growth can be considered a nutrition problem . . . increased deposition of N and S can be regarded as a . . . fertilization effect, and the increased leaching of nutrient cations . . . as an oligotrophication or acidification effect . . . the general hypothesis that acid precipitation significantly will decrease forest production over large areas must be revalued. The deposition of N and to some extent S . . . is likely to increase forest production. Reduced growth may be expected where or when nutrients like Mg and possibly K are the growth limiting elements."

RECENT INITIATIVES DEALING WITH ACID PRECIPITATION AND ITS BIOLOGICAL EFFECTS

In 1975, the National Academy of Sciences' Committee on Atmospheric Sciences published its report on Atmospheric Chemistry: Problems and Scope (NAS 1975). Growing awareness of important influences of acid precipitation on fish populations and potential effects on forest and crop plants led the U. S. Forest Service to sponsor the First International Symposium on Acid Precipi- tation and the Forest Ecosystem at Columbus, Ohio in May, 1975. The proceedings of this Symposium and the Associated Workshop Report were

published by Dochinger and Seliga (1976a, 1976b). At Congressional hearings in July, 1975, Cowling (1976) testified on the inadequacy of research in the United States on Acid Precipitation and its biological consequences. Specifically, the lack of a coordinated program of research on ecological effects and lack of a stable monitoring network were recognized as primary causes of our profound ignorance of acid precipitation. In the spring of 1976, however, a cadre of scientists in various institutions and agencies throughout the United States began the process of creating the National Atmospheric Deposition Program (NADP) to meet these two critical needs (Kennedy 1977; Galloway and Cowling 1978).

In the fall of 1977; the President's Council on Environmental Quality contracted with the NADP for the drafting of "A National Program for Assessing the Problem of Atmospheric Deposition (Acid Rain)." This publication (Galloway and others 1978) provided the basis for a Presidential Initiative on acid precipitation which President Carter announced on August 2, 1979 in his Second Environmental Message (Carter 1979). This initiative calls for a 10-year long, $10,000,000 per year program of research on the causes and consequences of acid precipitation. A standing Acid Rain Coordinating Committee was established by the President to plan and manage the program. Leadership for the Committee is provided by co-chairmen from the Department of Agriculture and the Environmental Protection Agency. At the present time, the Acid Rain Coordinating Committee is drafting a coherent program of research on atmospheric chemistry and transport, chemical and biological monitoring, ecological and materials-damage effects, economic assessments, and public-policy options for control of acid precipitation and/or amelioration of its ecological effects.

Wetstone (1980) has recently summarized the biological and materials-damage effects of acid precipitation in relation to the pollution- control laws in North America.

In conclusion, the Presidential Initiative on Acid Precipitation, coupled with growing Congres- sional, public, and private-industrial interest in acid precipitation research, provide a basis for increasing hope that the United States will do its part, together with Sweden, Norway, England, Canada and other nations, to meet the challenge of continuing economic development with adequate safeguards for the quality of life and the long- term productivity of ecosystems on which our good life critically depends.

LITERATURE CITED

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Ambio. 1976. Report of t h e I n t e r n a t i o n a l Conference on

t h e e f f e c t s of ac id p r e c i p i t a t i o n i n Telemark, Norway. Ambio 5 :200-252.

Bo l in , B., L. Granf t , L- Ingels tam, M. Johannesson, F. Mattsson, S. Oden, H. Rodhe, and C . 0 . Tam.

1972. A i r p o l l u t i o n a c r o s s n a t i o n a l boundaries. United Nations Conference on t h e Human Environ- ment. 97 p. P . A. Nors tedt and Sons, Stockholm.

Braekke, F. H. , ed. 1976. Impact of a c i d p r e c i p i t a t i o n on f o r e s t

and f r e shwate r ecosystems i n Norway. Res. Rep. 6: Acid p r e c i p i t a t i o n - e f f e c t s on f o r e s t s and f i s h . Aas, Norway. 1 1 3 p.

C a r t e r , J , 1979. The P r e s i d e n t ' s Environmental Program 1979.

57 p. The P r e s i d e n t ' s Council on Environmental Qua l i ty . Washington, D. C . , USA.

Cogb i l l , C . V., and G. E. Likens. 1974. Acid p r e c i p i t a t i o n i n t h e n o r t h e a s t e r n

United S t a t e s . Water Resources Res. 10:1133-1137.

Cowling, E. B. 1976. Testimony on r e s e a r c h and development

r e l a t i n g t o s u l f a t e s i n t h e atmosphere. & Research and development r e l a t i n g t o s u l f a t e s i n t h e atmosphere - Hearings b e f o r e t h e Subcommittee on t h e Environment and t h e Atmos- phere of t h e Committee on Science and Tech- nology. U. S. House of Rep., 94th Congress, F i r s t Sess ion , p. 398-440. Washington, D. C .

Cowling, E. B. 1980s. From r e s e a r c h t o p u b l i c p o l i c y : p rogress

i n s c i e n t i f i c and p u b l i c unders tanding of a c i d p r e c i p i t a t i o n and i t s b i o l o g i c a l e f f e c t s . -Proc. Act ion Seminar on Acid P r e c i p i t a t i o n [Nov. 1-3, 1979, Federa t ion of On ta r io Natnral- ists , Don M i l l s , Ontar io , Canada], 27 p.

Cowling, E. B. 1980b. An h i s t o r i c a l resume of p rogress i n

s c i e n t i f i c and p u b l i c unders tanding of a c i d p r e c i p i t a t i o n and i t s b i o l o g i c a l consequences. I n Proc. I n t . Conf. on Eco log ica l Impacts of -Acid P r e c i p i t a t i o n [Sandef jord , Norway].

Cowling, E . B. 1980c. Acid p r e c i p i t a t i o n and i t s e f f e c t s on

t e r r e s t r i a l and a q u a t i c ecosystems. 5 Aerosols : anthropogenic and n a t u r a l , sources and t r a n s p o r t . T. J. Kneip and P. J. Lioy, eds Ann. New York Acad. Sc i . Volume 338:540-555.

Dochinger, L. S., and T. A. Se l iga . 1976a. Proceedings F i r s t I n t e r n a t i o n a l

Symposium on Acid P r e c i p i t a t i o n and t h e F o r e s t Ecosystem. USDA F o r e s t Se rv ice , Gen. Tech. Rep. NE-23, 1079 p. Nor theas t . For. Exp. S t n . , Upper Darby, Penn.

Dochinger, L. S. , and T. A. Se l iga . 1976b. Workshop r e p o r t on a c i d p r e c i p i t a t i o n

and t h e f o r e s t ecosystem. USDA Fores t Service . Gen. Tech. Rep. NE-26, 1 8 p . , Northeast . For. Exp. S ta . , Upper Darby, Penn.

Feth , J. H . , S. M. Rogers, and C . E. Roberson. 1964. Chemical composition of snow i n t h e

nor the rn S i e r r a Nevada and o t h e r a r e a s . Geol. Survey Water Supply Paper 1535-J. 39 p.

Galloway, J. N . , and E. B. Cowling. 1978. The e f f e c t s of p r e c i p i t a t i o n on a q u a t i c

and t e r r e s t r i a l ecosystems: a proposed p r e c i p i t a t i o n chemistry network. J. A i r P o l l u t i o n Control Assoc ia t ion 28:229-235.

Galloway, J. N . , E. B. Cowling, E. Gorham, and W. W. McFee.

1978. A n a t i o n a l program f o r a s s e s s i n g t h e problem of atmospheric d e p o s i t i o n ( ac id f a i n ) . 97 p. Nat ional Atmospheric Deposi t ion Program, Na tu ra l Res. Ecology Laboratory , For t C o l l i n s , Colorado.

Gambell: A. W. , and D. W. F i she r . 1966. Chemical composit ion of r a i n f a l l .

e a s t e r n North Caro l ina and s o u t h e a s t e r n Vi rg in ia . Geol. Survey Water Supply. Paper 1335-K. 41 p.

Gorham, E. 1958. The i n f l u e n c e and importance of d a i l y

weather cond i t ions upon t h e supply of c h l o r i d e , s u l p h a t e , and o t h e r i o n s t o f r e s h wa te r s from atmospheric p r e c i p i t a t i o n . P h i l . Trans. Royal SOC. Lond. Biol . Sc i . 241:147-178.

Gorham, E. 1976. Acid p r e c i p i t a t i o n and i t s i n f l u e n c e upon

a q u a t i c ecosystems - an overview. Water, A i r , S o i l P o l l u t i o n 6:457-481.

Grahn, .0., H. Hul tberg , and L. Landner. 197L. Ol igo t roph ica t ion - a s e l f - a c c e l e r a t i n g

process i n l a k e s sub jec ted t o excess ive supply of a c i d substances . Ambio 3:93-94.

Heck, W. W . , A. S. Heagle, and E. B. Cowling. 1977. Impact of a i r p o l l u t a n t s on s o i l , wa te r ,

f l o r a and fauna: impact on p l a n t s . I n Proc. S o i l Conservation Soc ie ty of America p. 193-207.

Howells, G. 1979. Eco log ica l e f f e c t s of a c i d p r e c i p i t a t i o n .

Report of a workshop h e l d a t Galloway, Scot land [September 19781. Prepared by t h e Cen t ra l E l e c t r i c i t y Research Labora to r i e s , Leather-head, Surrey, United Kingdom.

Hutchinson, T. C . , and M. Havas, eds . 1980. E f f e c t s of a c i d p r e c i p i t a t i o n on

t e r r e s t r i a l ecosystems. 654 p. Plenum P r e s s , New York.

Johnsson, B., and R. Sundberg. 1972. Has the acidification by atmospheric pollution caused a growth reduction in Swedish forests? Research Note No. 20. 48 p., Department of Forest Yield Research, Royal College of Forestry, Stockholm, Sweden.

Kennedy, V. C. 1977. Research and monitoring of precipitation chemistry in the United States - present status and future needs. 75 p., Federal Interagency Work Group on Precipitation Quality. Office of Water Data Coordination. U. S. Geological Survey, Reston, Va.

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Likens, G. E. 1976. Acid rain. Chem. & Eng. News 54(48):29-44.

Lodge, J. P., J. B. Pate, W. Basbergill, G. S. Swanson, K. C. Hill, E. Lorange, and A. L. Lazrus. 1968. Chemistry of United States Precipitation. 66 p., Final report on the National Precipita- tion Sampling Network, National Center for Atmospheric Research, Boulder, Colo.

National Academy of Sciences. 1975. Atmospheric Chemistry: Problems and Scope. 130 p., National Academy of Sciences, Washington, D. C.

0d&n, S. 1968. The acidification of air and precipitation and its consequences in the natural environment. Ecology Committee Bulletin No. l., 117 p., The State National Science Research Council, Stockholm. Translation Consultants, Ltd., Arlington, Va.

Smith, R. A. 1872. Air and rain: the beginnings of chemical climatology. 600 p., Longmans, Green, London.

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Tam, C. O., and E. B. Cowling. 1977. Acidic precipitation and forest vegetation. Water, Air, Soil Pollut. 7: 503-511.

Wetstone, G. 1980. Air pollution control focus in North America and the problem of acid rain and snow. Environ. Law Reptr . X(2) :50001-50020.

Wittwer, and Bukovac. 1969. The uptake of nutrients through leaf surfaces. 'InHandbuch der Pflanzenernahrung und Dungung. K. Scharrer and H. Linser, eds. p. 235-261. Springer-Verlag, New York.

Simulation Modeling of the Effects of Chronic Pollutant Stress on Plant Processes and Plant Community Dynamics

Modeling Pollutant Uptake and Effects on the Soil-Plant-Litter System '

R. J. Luxmoore2

Abstract: Five coupled models of water, carbon, and chemi-cal dynamics in a soil-pl ant- l i t ter system are outlined. Algorithms defining gaseous and particulate pollutant uptake are described along with functions for chemical effects on plant growth and l i t t e r decomposition. Some simulation results of a deciduous forest i l lus t ra te the importance of diurnal and annual cycles of environmental conditions on pollutant movement in vegetation. This modeling approach has provided (1) insights into plant physiological processes and their interactions, ( 2 ) identi-f i cati on of plant properties important i n pollutant uptake, (3) a1 ternati ve hypotheses about pollutant effects, and ( 4 ) a unified basis fo r assessment of diurnal and long-termpollutant impacts on plant communities.

'and a l l the king's horses and a l l the king's paper, an outline i s presented of f ive models men coul dn I t p u t Humpty together again.'' that link together and provide a framework fo r

study of pollutant uptake and effects in thefrom Humpty Dumpty, Anon. whole plant environment complex. Some appl ica-

tions are shown and the use of models inThe discouraging words of the nursery rhyme analysis of experiments i s explored. Lastly,

suggest that the synthesis of bits of an egg to some specul ati ons are presented about pol 1 utant a whole will not happen at leas t while horses impacts on whole plants and their diurnaland men are in charge! Our task of trying to metabolism.couple together bi ts and pieces of mechanistic information about the physiology of trees and MODELING THE SOIL-PLANT-LITTER SYSTEM responses to soil and atmospheric environments i s no less awesome a challenge. Simulation The development of a unified approach to themodeling is a remarkable tool fo r meeting t h i s modeling of terres t r i a1 processes has beenchallenge, since through mathematics coupled undertaken a t Oak Ridge. Five component modelsrelationships may be quantified. In th i s paper, of water, carbon, and chemical dynamics in a

soil-pi ant-1 i t t e r system were constructed and linked together (Baes e t a1. 1976). The models

presented a t the Symposium on Effects of Air ( table 1) are deterministic. The flow processes Pollutants on Mediterranean and Temperate Forest are dependent on gradient terms calculated byEcosystems, June 22-27, 1980, Riverside, the models to provide the flow driving forcesCalifornia, U.S.A. and empirical inputs are used to represent path-

way resistances or conductivities. Flowresearch staff member, Environmental directions are not predetermined and the models

Sciences Divisi on, Oak Ri dge National can be applied to a range of different soil-Laboratory,

by Oak Ridge, Tennessee 37830. plant systems (e.g., coniferous, deciduous

Operated Uni on Carbi de Corporati on under fores t ) by changing the empirical properties in contract W-7405-eng-26 with the U .S. Department the input data. The reader i s referred to theof Energy. Publication No. 1553, Environmental documentation reports ( table 1) for furtherSciences Division, ORNL. details .

Tab1 e 1--Some attr ibutes of coup1 ed models describing carbon, water, and chemi cal dynamicsin the soil -pi ant-li t t e r system.

CoMFONErn WATER SOIL EHCHANBE MOT mLUTl UPTAKE SOLUTES

NAME PROSPER ITEHMI SCEHM CERES DIFMAS DRYADS

TIME STEP 1 6 0 8 60mi". IS OR 00 mi". w m h IS OR w m;". I 6 OR 80 mi".

ATTRIBUTES EVAPOTRANsflRATIOt BY COMBINATION

USES EMPIRICAL DISTRIBUTION

W2 DIFFUSION EOUATION FOR

IMPLEMENTS MODEL 3F DIFFUSION AND

SOLUTEUPTAKEBY ROOTS AND LEAVES.

EOUATION. COEFFICIENT NET PHOTOSYN. MASS FLOW OF

SOIL WATER FLOW BY DARCV FLOW

IKdl FOR SOIL OF INTEREST.

THESIS.

SUBSTRATE GHADt:

SOLUTES TO ROOTS BY BALDWIN. NYE AND TINKER 119731.

DIFFUSIVE GAS UPTAKE BY LEAVES.

EOUATION. ENT EOUATION FOR GRADIENT EOUATION

USES EMPIRICAL RELATIONSHIP

lRANSLOCAT10N

USES INPUT VALUES

FOR PHLOEM TRANS- LOCATION

BETWEENSURFACE RESISTANCE AND SURFACE WATER POTENTIAL.

FOR POTENTIAL GROWTH OF LEAF. STEM. BOOT, FRUIT

TRANSPIRATION FLUX USED FOR XYLEM TRANSPORT.

EMPIRICAL DATA EMPIRICAL LITTER DECOMPOSITION

P U N T DEMAND FUNC- TION DETERMINED BY

FOR SOIL HYDRAU- LIC PROPERTIES.

RELATIONSHIPS. POTENTIAL SOLUTE CONCENTRATION INPUT VALUES.

REFERENCE MUFF fI,11977; BEGOVICH AND OIXON rn i l 119781 JACKSON 118751

The coupling between models (fig. 1) shows that every model has informati on transfer with at least two other models, and these take place on either an hourly time step or every 15 minutes during storm events. Hourly values of sto-matal resistance and plant water potential from PROSPER are used in CERES to determine photo-synthesis and growth respectively. Leaf and root growth in t u r n influence transpiration and thus soil water flow. During ra infal l , in f i l -tration and the movement of water between soil layers (calculated in PROSPER) i s used in the soil chemistry model (SCEHM) to calculate chemical f l uxes. Chemi cal concentrati on and root water uptake information are used in DIFMAS to calculate chemical uptake into root by diffusion and mass flow. Chemicals within the plant are moved up in the transpiration stream and down in the phloem pathway.

This se t of models can be run for simulation periods of several years and annual budgets for water, carbon and chemicals can be evaluated as well as detailed results for hourly periods of interest . The algorithms defining gaseous and parti cul ate pollutant uptake and effects on plant growth and l i t t e r decomposition are out-lined in the next two sections along with example simulation results .

AIR POLLUTANT UPTAKE

The uptake of a i r pollutants by vegetation may occur directly through leaves (gaseous and parti cul ate) or indirectly through roots after the pollutants have been incorporated into soil . Gaseous uptake i s represented by a diffusion equation (same form as the photosynthesisequati on ) . Thus

where g i s the external pollutant concentration (ml/ml)

gi i s the internal pollutant concentration (ml/ml)

g i s gas density (Ug/ml)

ra i s boundary layer diffusion resistance (seclcm)

rs i s stomata1 resistance (seclcm)

rm i s mesophyll resistance (sec/cm)

Ug i s uptake (iig/cm* leaf/sec)

The value of gi i s made to vary between zero and ge depending on the level of pollutant in leaf storage (Ei) as follows,

Em i s the maximum allowable level of pollu-tant in leaf storage, an input parameter.Operationally th is i s the pollutant level at which the leaf tissue becomes necrotic.

ORNL-DWG 75-15812R2

JroweRI

PROSPER CERES SCEHM DIFMAS

soi 1 -pi ant-atmosphere water f l ow model carbon dynamics of vegetation and l i t t e r soil chemistry model diffusion andmass flow of chemicals t o roots

DRYADS chemi cal dynami cs of vegetation 1 i t t e r

and

Figure 1--Coupling of f ive process models that describe hourly carbon, water, and solute dynamics of the soil-plant-l i t ter system.

Sulfur dioxide uptake by an oak-hickory f o r e s t in the v i c in i ty of a lead mining and smelter complex in southeastern Missouri was simulated and r e su l t s i l l u s t r a t e the behavior of the model. Cumulative su l fur levels in leaves ( f i g . 2) show a rapid increase on the 25th of August, a day in which the atmospheric SO2 level was increased 10 fo ld above ambient. The t ranslocat ion of su l fur from leaf t o stem ( f ig . 2 ) c l ea r ly shows a diurnal pat tern and a t elevated r a t e s on the 25th of August. Some of the su l fu r material t ha t was transported t o the roots , leaked in to the t ranspi ra t ion stream and returned from the roots t o the stem, a l b e i t in t r ace amounts. The phloem and xylem transport pathways can a l l ow considerable mobi 1 i t y of sol-utes between plant t i s sues according t o the simulation. The cumulative su l fu r leve ls in the l ea f , stem and root components ( f i g . 3 ) show t h a t the majority of su l fu r remained in t he leaves. The value of 8 x 105 p g ~/m2 i s equivalent t o a 1 eaf concentration of 180 ppm.

ORNL- DWG 80-11126 â‚¬

-21 23 25 27 29 31

DAYS IN AUG

Figure 2--Simul ated cumulative su l fur dioxide uptake by vegetation ( g/m2) and leaf t o stem phloem translocat ion r a t e ( pg/m^/h) f o r 11 days in August.

The uptake of po l lu tan ts from par t icu la tes deposited on leaves (Ui ) i s represented by a gradient equation using empirical input values for the cu t icu lar conductivity ( k l ) and thick-ness ( W ) . Thus,

where S i s the external po l lu tan t on leaf surface (g/m2 land)

S i i s the in te rna l po l lu tan t within fo l iage (g/m2 land)

The amount of dissolved pol lutant on leaf surfaces i s calculated as the lesser of e i t he r the product of sol ubi 1 i t y and the water , volume on leaves ( in te rcept ion) or the current amount of po l lu tan t on leaves. The soluble pol lu tan t within leaves ( S i ) i s assumed t o be uniformly

dis tr ibuted and has one of two f a t e s . I t may be transported t o other plant parts or be incorpo-rated in the leaf in an immobile form. The cu-t i cu l ar uptake process i s considered revers ib le in the model. Thus during r a i n f a l l , wash-off occurs and i f Se becomes l e s s than Si , then leaching of pol lutant out of leaves will occur.

ORNL- DWG 76- 13390R

'06 6

10' 22 23 24 25 26 27 28 29

DAYS O F AUGUST

Figure 3--Simul ated su l fur elemental accumul a-t ion in leaf , stem, and root t i s sue (pg/m2) resu l t ing from gaseous uptake.

Sens i t i v i t y analysis of the leaf c u t i c l e con-duct iv i ty ( f i g s . 4a, b) shows tha t grea te r conductivity i s associated with greater chemical (zinc in the example) uptake by leaves and a s l i g h t l y reduced uptake of zinc from the so i l solution (Begovich and Luxmoore 1979). This l a t t e r and more subt le e f f ec t i s induced by the higher zinc level in the plant with higher con-ducti vi t y which feeds back a reduced chemical demand in the root uptake algorithm. I t i s pos- s i b l e t h a t subt le e f f ec t s may become s ign i f i can t when integrated over long time periods. Cuticu-l a r conductivity and the equivalent property a t the root-soi l in te r face ( root conductivity, k c ) were shown t o be very s ens i t i ve parameters in the model, and yet these are perhaps the l e a s t well characterized experimentally. Results from a s e n s i t i v i t y analysis of root conductivity on lead uptake ( t a b l e 2) show large increases in uptake by roots and lead c o n c e n t r a t i o ~ i n t r e e t i s sues with increase in kr from 10" cm/sec t o 10-6 cmlsec. The simulations a l so show tha t pol lutants accumulate p re fe ren t i a l l y in t he leaf and root , the s i t e s of pol lutant entry. A modification has subsequently been added t o t he model t o allow chelation of chemical within the

176

plant (Luxmoore and Begovich 1979) which has the The monthly pattern of lead uptake by roots effect of i ncreasing the mobi 1 i ty of pollutant and foliage simulated for an oak forest near a within the plant. Thus, the s i t e of pollutant mine-smelter complex during the f i r s t year of entry may not be the s i t e of accumulation. operation shows that uptake corresponds with the

growing season (table 3). The major proportion ORNL-OWG 80- 11127 ESD

(88%) of root uptake occurred during the day chiefly due to two compl ementary transportation processes; the mass flow of pollutant to roots and mass flow of pollutant from roots to shoots. The la t t e r was the controlling process in the simulations. Overall, leaf uptake was more than double that simulated for roots for the f i r s t year of smelter operati on.

Tabl e 3--Simul ated root and leaf uptake, (mg pb/m2 landlmonth) of lead by oak vegetation in the vicinity of a mine-smel t e r complex.

- Month Night2.0 I --lo-' YT1.8

I- - - --- 10-9 ---..-....-.! o - ~ ~/ -1.6

a ! ? -- 10-13 Jan.-2 2 1.4 1 -' 0 - Feb.

.-.--*' March*.---

- April

- May ,

June -

July

Aug . 0 5 10 15 20 25 30 Sept.

DAYS IN JULY Oct. Figure 4--a. Influence of leaf cuticle perme-ab i l i ty on zinc uptake by leaves. Nov.

b. Influence of leaf cuticle penne- Dec. ab i l i ty on zinc uptake by roots.

Total

Tabl e 2--Sensi t i vity of annual root lead uptake and tissue concentration (prior to leaf f a l l ) in an oak forest to change in the root solute conductivity parameter ( k r ) .

September t issue concentration (ppm)I I I I Annual Stem Root

root uptake ( pg/cm2/year) Leaf Sapwood Heartwood Sapwood Heartwood Fruit

Pollutant Impacts

Simple ramp functions are used to determine pollutant effects on the growth and decomposi-tion of leaf, stem, root and f r u i t components.Separate ramp functions for either growth ef-fects ( f ig . 5) or control of decomposition in the l i t t e r (same form as for growth effects) represent ranges of chemi cal def i ciency, sufficiency, and toxicity as the chemical con-centrati on increases. Hypotheses concerning benefici a1 ( f e r t i l i z e r ) and toxic pollutant effects can thus be examined. The product of the growth coefficient and tissue growth ra te (from CERES) provides a modified growth rate due to pol 1 u tant effects.

Figure 5--The re1 ati onship between the growth coefficient ( G c ) and the amount of element in tissue (Ei) used to represent deficiency(Ei < E1)m sufficiency ( E l < Ei < E?), and toxicity (Ei > E 2 ) effects of the elements on tissue growth rate.

A six-year simulation of heavy metal deposi-tion, transport, and uptake in an oak-hickory forest in southeastern Missouri showed that the lead accumulation was greatest in the l i t t e r (Luxmoore et a1. 1978). Root uptake of lead i ncreased through the six-year period, whereas leaf uptake was a constant for the repeti t ive annual deposition of 25 g Pb/m . Due to the buildup of lead in the plant tissues, the mor-ta l i ty of pl ant parts returned increasingly greater amounts of lead to the l i t t e r system . The l i t t e r dry weight increased through the six- year period by 949 g/m2. This comparesreasonably with a difference of 1130 g/m2 between the l i t t e r mass at a control s i t e and a s i t e exposed to equivalent heavy metal deposi-tion (Watson e t a1. 1976). The simulation results pose an alternative hypothesis to the experimental inference of reduced rates of l i t -t e r decomposition at the elevated levels of heavy metal accumul a t i on (Jackson and Watson 1977), by showing that the same effect could be obtained with increased mortality of plant parts.

Next Step

The previous sections outline one particular se t of models and show some simulation results including sensi t iv i ty analysis of selected

parameters. The work presented i s best viewed as "equipment"; the subrouti nes being component parts which collectively form a package of hypotheses, theories, or knowledge in mathematical form. We need to thoroughly t es t models through applications to experimental studies as much as possible to, hopefully, invalidate parts of the model structure. The deviations of model predictions from experimental findings provide the key to new insights - in th i s way models f a c i l i t a t e the analysis and synthesis of complex interactions. Putting models to work in th i s way requires data from well-documented experi-ments. For example, the uptake and physiolog-ical effects of gaseous pollutants have been documented for several t ree species (Jensen and Kozlowski 1975, Thompson e t a1. 1967, Roberts 1974, Lawhon 1973, Houston and Stai rs 1973), and these experimental data can be used in leaf physiological models (Kercher 1977) or in the models outlined in the ear l ier sections. A con-siderable body of experimental data has been developed for a i r pollutant effects on plants, and i t i s timely to apply modeling techniques in the research analysis of impacts. An alterna-t i ve approach i s one of conceptual extrapol a t i on of the model behavior. Some speculations are presented in the next section.

Pollutants and the Diurnal Cycle

The modeling of water, carbon, and chemicals as coupled components in soi 1-pl ant-1 i t t e r systems has stimulated the development of a con-ceptual framework for the diurnal cycle in plants ( f ig . 6) that can be used to invent hypotheses of pollutant effects on whole plants. In the diurnal cycle, plants change between two relative states: (a) lowest sucrose, metabolite, and solute reserves at max-imum hydration (dawn s ta te) ; and ( b ) highest sucrose, metabol i t e , and solute reserves a t minimum hydration (dusk s ta te) . These states are relative and apply to a given day. Photosyn-thesis recharges the plant with sucrose and increases starch storage (or equivalent) during the day. A t the same time, the plant i s also recharging with nutrients and undergoing dehy-dration. The loss of water can reduce the ra te of cell expansion processes during the day with greater growth being favored with rehydrati on. Thus plants may need to solve a timing imbalance between carbon gain and uti 1 ization by changes in internal storage. The higher internal carbon status of leaves during the afternoon may reduce the significance of pollutant impacts on leaves during this part of the day. Photosynthesis may be already slowed by product accumulation, or alternatively detoxification mechanisms using readily avai 1 able carbon metabolites and/or energy may more easily cope with pollutant in-su l t than during early morning when internal carbon status i s lower.

The diurnal pattern of behavior (fig. 6) also suggests that root exudation of carbon compounds could be faci l i ta ted during the day. In the

same way, the carb6n supply t o mycorrhizae and root nodules may be f a c i l i t a t e d . Disruption of these processes through the impact of a i r pol-lu tan ts may be of great importance t o under-standing who1 e pl ant responses. Pol lutant s t r e s s t ha t causes reduced ,photosynthesis and/or greater r e sp i r a t i on in fo re s t ecosystems may decrease the carbon 1 eakage t o mycorrhizal asso-c i a t i ons with roots , po ten t ia l ly decreasing the extent and ef f ic iency of the fungi in supplying nut r ien ts back t o the t ree . T h u s , i t may be fur ther hypothesized tha t phytotoxic a i r pol lutants may cause fo re s t ecosystems t o be less e f f i c i e n t in nutr ient r e t en t i on ( i .e., become more leaky, see also OINeill et a1. 1977) and conversely beneficial a i r po l lu tan ts may in-crease nut r ien t r e t en t i on of fo re s t ecosystems. Elevated atmospheric CO2 leve ls may be an ex-ample of the l a t t e r .

I PHOTOSYNTHESIS RECHARGESPL.hT WITH SUCROSE 2 'LOWER WAlEm POTEhTIAL REDUCES CELL EXPANStON IMINIMUM G R M H RATE1 3. +ACTIVE SOLUTE UPTAKE FROM MASSFLOW POOL

5. ROOT EXUDATION PROMOTED. LESS ROOT SLOUGHING & FASTERPHLOEMTRANSLOCATIONOFSUCROSEFROMLEAVESTOSTEMSANDROOTS 7 FASTER XYLEM TRANSPORT OF SOLUTES AND METABOLLTES FROM ROOTS TO STEMS AND LEAVES

SUCROSE STARCH-CYTOPLASM

-,I SUCROSE -P STARCH \, / SUELL SHRINK \

I' SOLUTES IN -^----P SOLUTES IN \, CYTOPLASM VACUOLE

NIGHT CONDITION

4. METABOLITE -CYTOPLASM S. ROOT SLOUGHING PROMOTED. LESS EXUDATION 6. SLOWER PHLOEM TRANSLOCATION - REDUCED SUCROSEGRADIENT 7. ,SLOWER XYLEMSOLUTE AND METABOLITE FLUX - REDUCEDTRANSPIRATION

.OOMINANT EhERGV UTIL#.?ATsON FOR T M E PERIOD

N D L C E D B Y ROOT RESISTANCE TO TRANSPIRATION

Figure 6--Diurnal pat tern of carbon, water, and solute dynamics showing re1 a t i ve tendencies and r e l a t i v e s t a t e s i n vegetation.

Perhaps, l i k e Humpty Dumpty, these attempts a t deriving whole system understanding from the pieces involved shows many cracks and flaws. Nevertheless, we give i t a go! The key t e s t i s our answer t o the question "Did we learn some-thing t h a t we d idn ' t know before?"

SUMMARY

Modeling of pol lutant in te rac t ions with whole pl ant processes has provi ded :

1 Insights about the processes and t h e i r in te r re la t ionships , e.g., ( a ) Transpiration may f aci 11 i t a t e pol -l u t an t uptake by t ransport ing chemical from roots t o stem thus maintaining a favorable chemical gradient fo r continu-ing uptake. (b) Phloem and xylem may provide ready transport pathways f o r pol lutant movement between plant par t s ( f i g . 3 ) . Ident i f ica t ion of plant propert ies im-portant in pol lutant uptake. In particu-1 a r , 1 eaf and root chemical conductivity have great influence on pol lutant uptake ( f i g . 5, t ab l e 2) . Alternat ive hypotheses, e.g., increased f o r e s t 1 i t t e r in areas polluted with heavy metals could be due t o increased mortal i ty of plant par t s in addition t o reduced decomposition r a t e . A basis f o r short-term (d iurna l ) and long-term speculation or pol lutant impacts, e.g., ( a ) Hourly changes in water, carbon, and nutr ient s t a tu s of pl ants may inf 1 uence physiological s e n s i t i v i t y t o pol lutant i n su l t . (b) Pol lutant disruption of carbon a l lo-cat ion t o be1 owground processes may have long-term nut r ien t cycling impacts.

LITERATURE CITED

Baes, C. F., C. L . Begovich, W. M. Culkowski, K. R . Dixon, D. E. Fields, J. T. Holdeman, D. D. Huff, D. R . Jackson, N . M. Larson, R. J . Luxmoore, J. K. Munro, M. R. Patterson, R. J . Raridon, M. Reeves, D. C. S te in , J. L. Stolzy, and T. C. Tucker.

1976. The unified t ransport model. In Ecology and analysis of t r ace contaminants progress report October 1974-December 1975. R. I . Van Hook and W. D. Shults, eds., pp. 13-62. ORNL/NSF/EATC-22. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830. 200 pp.

Baldwin, J. P. , P. B. Nye, and P. B. Tinker. 1973. Uptake of solutes by mult iple root

systems from s o i l , 111. A model fo r calcu- l a t i ng the solute uptake by a randomly dispersed root system developing in a f i n i t e volume of so i l . Plant Soil 38:621-635.

Begovich, C. L . , and D. R. Jackson. 1975. Documentati on and appl i c a t i on of SCEHM.

A model of so i l chemical exchange of heavy metals. ORNL/NSF/EATC-16. Oak Ridge National Laboratory, Oak Ridge, Tennessee. 67 PP.

Begovich, C. L., and R . J . Luxmoore. 1979. Some s e n s i t i v i t y s tudies of chemical

t ransport simulated in models of the so i l - plant- 1 i t t e r system. ORNL/TM-6791. Oak Ridge National Laboratory, Oak Ridge, Tennessee. 97 pp.

Dixon, K. R. , R . J . Luxmoore, and C. L. Begovich. 1978. CERES - A model of f o r e s t stand biomass

dynamics fo r predicting t r ace contaminant, nutr ient and water e f f ec t s . I . Model descript ion, 11. Model documentation. Ecol. Model. 5: 17-38. 93-114.

Houston, D. B., and G. R. S t a i r s . 1973. Genetic control of su l fu r dioxide and

ozone tolerance i n eastern white pine. For. Sci . 19: 267-271.

Huff, D. D., R . J . Luxmoore, J . B. Mankin, and C . L. Begovich.

1977. TEHM. A t e r r e s t r i a1 ecosystem hydrology model. ORNL/NSF/EATC-27. Oak Ridge National Laboratory, Oak Ridge, Tennessee. 153 pp.

Jackson, D. R . , and A. P. Watson. 1977. Description of nu t r ien t pools and

transport of heavy metals i n a forested watershed near a lead smelter. J. Environ. Qual. 6: 331-338.

Jensen, K. F., and T. T. Kozl owski. 1975. Absorption and trans1 oeati on of su l fur

dioxide by seedlings of four f o r e s t t r e e species. J. Environ. Qual. 4:379-382.

Kercher, J. R. 1977. GROW1: A crop growth model f o r

assessing impacts of gaseous pol lu tan ts f rom geothermal techno1 ogi es. UCRL-52247. Lawrence Li vermore Laboratory, Cal i f orni a.

Lawhon, W. T. 1973. Radial growth and wood densi ty of white

pi ne in re1 a t i on t o coal -deri ved envi ronmental pol lutants . Ph.D. d isser ta t ion . Graduate program in ecology, University of Tennessee, Knoxvi 11 e , Tennessee. 110 pp.

Luxmoore, R . J., and C. L. Begovich. 1979. Simulated heavy metal f luxes in t r e e

microcosms and a deciduous fo re s t . Internal . Soc. Ecology. Model1 ing. J. 1:48-60.

Luxmoore, R. J . , C. L. Begovich, and K. R . Dixon. 1978. Modeling solute uptake and

incorporation in to vegetation and l i t t e r . Ecol. Model. 5:137-171.

O'Neill , R. V . , B. S. Ausmus, D. R. Jackson, R. I . Van Hook, P. Van Voris, C. Washburne, and A. P. Watson.

1977. Monitoring t e r r e s t r i a1 ecosystems by analysis of nutr ient export. Water, Air, and Soil Pollut. 8:271-277.

Roberts, B. R . 1974. Fol i ar sorption of atmospheric su l fur

dioxide by woody plants . Environ. Pollut. 7:133-140.

Thompson, C. R., D. C. Taylor, M. D. Thomas, and J. 0. Ivie .

1967. Effects of a i r pol lutants on apparent photosynthesis and water use by c i t r u s t r ee s . Environ. Sci. Technol. 1:664-650.

Watson, A. P., R . I . Van Hook, D. R . Jackson, and D. E . Reichle.

1976. Impact of a lead mining-smelting complex on the f o r e s t f l oo r l i t t e r arthropod fauna in the New Lead Belt region of southeast Missouri. ORNL/NSF/EATC-30. Oak Ridge National Laboratory, Oak Ridge, Tennessee. 163 pp.

Data-Based Ecological Modeling of Ozone Air Pollution Effects in a Southern

California Mixed Conifer Ecosystem1

Ronald N. Kicker t and Barbara emm mill^

Abstract : The purpose of t h i s r esea rch was t o determine t h e e f f e c t s of ozone a i r p o l l u t i o n on a mixed c o n i f e r f o r e s t ecosystem i n t h e San Bernardino National F o r e s t , C a l i f o r n i a .

We used an eco log ica l systems modeling approach i n con- c e r t wi th var ious b i o l o g i o a l s p e c i a l i s t s . This r. quired conceptual model development, computer programming, and t h e a n a l y s i s of o r i g i n a l p r o j e c t d a t a f o r model c a l i b r a t i o n .

fie found t h a t t h i s process l e d t o t h e i n v e s t i g a t o r s con- duc t ing new research of an i n t e g r a t i v e nature . A s t r u c t u r e f o r complex i n t e r a c t i o n s of f o r e s t e f f e c t s was produced. I n s i g h t s on changes i n ecosystem dynamics and a worst-case scenar io of f u t u r e f o r e s t changes were der ived. ,

We conclude t h a t sudden q u a l i t a t i v e changes i n c o n i f e r f o r e s t composition can occur under t h e in f luence of ozone a i r p o l l u t i o n and t h e exclusion of n a t u r a l f i r e events .

I f it were known t h a t a i r p o l l u t a n t s d id n o t on The b i o l o g i c a l , eco log ica l , and phys ica l envi- a f f e c t people and t h e i r environments, s o c i e t y ronment, t h e secondary s tandard. Recently, t h e would be l i k e l y t o have l i t t l e i n t e r e s t i n those s t andards were r a i s e d from 0.08 t o 0.12 ppm f o r one p o l l u t a n t s . The c e n t r a l i s s u e i s "What a r e t h e hour pe r yea r (u.s. Environmental P r o t e c t i o n Agency e f f e c t s ? " . 1979). I n view of t h e f a c t t h a t knowledge of p o l l -

u t a n t e f f e c t s cont inues t o develop, t h e c r i t e r i a f o r j u s t i f y i n g t h e l e g a l s tandard i s expected t o

INSTITUTIONAL SETTING be re-evaluated every few years .

I n t h e United S t a t e s , Nat ional Ambient A i r Q u a l i t y Standards f o r ozone have been l e g a l l y es - THE PROBLEM t a b l i s h e d with a view f o r e f f e c t s on humans, t h e primary s t andard , and s e p a r a t e l y f o r t h e e f f e c t s I n eva lua t ing c r i t e r i a f o r deciding upon t h e

secondary s tandard f o r ozone, i t has been recognized throughout t h e 1970's t h a t b i o l o g i c a l and eco log ica l e f f e c t s informat ion was biased toward

p r e s e n t e d a t t h e Symposium on E f f e c t s o f A i r t h e more r e d u c t i o n i s t i c l e v e l s , i . e . , biochemis-P o l l u t a n t s on Mediterranean and Temperate Forest t r y , p l a n t sc ience , p l a n t physiology, and, because Ecosystems, June 22-27, 1980, Rivers ide , of l o g i s t i c a l problems with l a r g e r s p a t i a l and C a l i f o r n i a , U . S . A . time s c a l e s , biased a g a i n s t , o r a t l e a s t f a i l i n g

t o cons ide r , e f f e c t s on "na tu ra l " eco log ica l systems i n t h e landscape. Biological e f f e c t s c r i t e r i a

s e n i o r Systems Analyst and Ass i s t an t have been based on d a t a f o r i n d i v i d u a l organisms, S p e c i a l i s t , r e s p e c t i v e l y , Divis ion of but t h e d i r e c t and i n d i r e c t e f f e c t s on p l a n t and Bio log ica l Control , Univers i ty of C a l i f o r n i a , animal communities have been mostly s p e c u l a t i v e Albany, C a l i f . (u.s. Environmental P r o t e c t i o n Agency 1978).

History of The Study

Object ives of t h e E n t i r e P r o j e c t

I n 1973, t h e EPA e s t a b l i s h e d a several -year s tudy of oxidant e f f e c t s on t h e mixed c o n i f e r ecosystem i n t h e San Bernardino National Fores t . The i n t e r p r e t a t i o n s der ived t o d a t e from t h i g p r o j e c t have c o n s t i t u t e d t h e major source of informat ion f o r t h e ecosystem chap te r on a i r q u a l i t y c r i t e r i a published by t h e EPA; however, t h e ma jo r i ty of t h e d a t a i n t e g r a t i o n remains t o be completed. A s a f u r -t h e r focus o f t h e p r o j e c t , two y e a r s a f t e r i t was i n i t i a t e d , t h e s e n i o r au thor was brought i n t o in t roduce computer s imula t ion a s a t o o l i n guiding t h e c o l l e c t i o n , i n t e g r a t i o n and i n t e r p r e t a t i o n of d a t a on f o r e s t responses t o oxidant s t r e s s . The p o t e n t i a l use of t h i s s tudy i n f u t u r e policy-making requ i red an emphasis i n t h e modeling e f f o r t p a r t i c - u l a r l y on long-term e f f e c t s , p ro jec ted e f f e c t s a t d i f f e r e n t t h e o r e t i c a l l e v e l s of oxidant f l u x , and e f f e c t s on t h e behavior of t h e n a t u r a l community a s opposed t o i n d i v i d u a l organisms.

Object ives o f t h e Modeling A c t i v i t y

S t r u c t u r a l Simplification--The goa l of t h e ecosystem modeling e f f o r t i s twofold, and equa l ly d i - v e r s e i n each d i r e c t i o n . Due t o t h e na tu re of t h e SBNF p r o j e c t , i t was requ i red t h a t t h e modeler be- g i n wi th a l o c a l i z e d , real-world s i t u a t i o n and make ex tens ive use o f t h e l a r g e data-base i n con- s t r u c t i n g t h e model. The real world s i t u a t i o n , from which t h e d a t a a r e der ived i s extremely var- i a b l e , c o n s i s t i n g of an east-west t r end ing moun- t a i n range which i n c r e a s e s i n e l e v a t i o n and changes i n s p e c i e s composit ion a long t h e same g r a d i e n t of oxidant f l u x , such t h a t e s s e n t i a l l y no c o n t r o l a r e a s a r e poss ib le . Given such a complex system, The f i r s t goa l of t h e modeling a c t i v i t y was t o break down t h i s system s t r u c t u r a l l y i n t o i t s s i m p l i f i e d , b a s i c components and d r i v i n g f a c t o r s .

Experiments and Model Behavior-- The o t h e r h a l f of t h i s goa l was t o provide answers t o t h e quest ion: how might one use a s imula t ion model f o r computer experiments t o a s s e s s t h e t o t a l i t y of t h e s e e f f e c t s , a c t i n g a lone o r s y n e r g i s t i c a l l y , on ecosystem s t r u c - t u r e and func t ion? A l i s t of e f f e c t s does n o t h e l p p o l i c y makers very much when they a r e i n t h e posi - t i o n of making d e c i s i o n s i n t h e f a c e of uncer t a in -t y - even l e s s does i t inform b i o l o g i c a l l y know- ledgeable people who r i g h t f u l l y suspec t t h a t i n t e r - a c t i o n s occur between i t ems on t h e l i s t t h a t w i l l a f f e c t f u t u r e outcomes a s much o r more than a sum-mary of s imple e f f e c t s could eve r express . Thus, t h e modeling e f f o r t has been developed t o address t h e fol lowing quest ions:

The EPA/SBNF P r o j e c t has attempted t o e s t ab - l i s h e f f e c t s o f ozone a i r p o l l u t i o n on t r e e stem growth, f o l i a r i n j u r y , t r e e m o r t a l i t y , r egenera t ion , cone product ion, n u t r i e n t cycl - i n g , and i n s e c t and d i s e a s e occurrence. What i s t h e consequence of t h e s e e f f e c t s when combined t o g e t h e r i n a s imulated ecosystem? What time s c a l e i s necessa ry t o use t o s e e t h e

f u l l long-term ecosystem e f f e c t s ? Is t h e r e p o t e n t i a l i n t h i s system f o r sudden jumps and i r r e v e r s i b l e t r ends?

The modeling methods and philosophy used i n t h e p r o j e c t have been descr ibed i n previous p u b l i c a t i o n s ( ~ i c k e r t 1977a, 1977b, 1980).

RESULTS

Because t h e modeling a c t i v i t y i s s t i l l being conducted, t h e r e s u l t s presented he re a r e no t based on experiments performed on t h e computer us ing t h e models. R a t h e r , t h e y a r e based on i n s i g h t s gained dur ing t h e model development process , from concep- t u a l i z a t i o n , t o mathematical formulat ion, t o compu- t e r coding, and a n a l y s i s of o r i g i n a l d a t a toward t h e goa l of c a l i b r a t i n g t h e models f o r t r e e s p e c i e s and s i t e s wi th in t h e SBNF and then applying those mod- e l s i n experiments of a i r p o l l u t i o n e f f e c t s .

How t h e Systems Modeling Process Aided t h e P r o j e c t

There a r e two ways i n which t h e t o t a l s tudy was improved. Model development a ided t h e p r o j e c t i n - v e s t i g a t o r s i n viewing t h e i r own work a s a p a r t o f an i n t e g r a t e d conceptual s t r u c t u r e . Also, wi th t h e des ign of a graphic model of va r ious subsystems, d i scuss ions wi th i n v e s t i g a t o r s l e d t o t h e i d e n t i f i - c a t i o n of ques t ions subsequent ly turned i n t o re-sea rch which otherwise would no t have been done. A mixed t r e e s p e c i e s popula t ion dynamics approach l e d t o s e e d l i n g es tabl ishment experiments, s tudy p l o t s e e d l i n g regenera t ion surveys , and a compre-hensive p e s t damage inventory, t o determine morta l - i t y p a t t e r n s . Data needed f o r c a l i b r a t i n g a s t and moisture model l e d t o a seismograph survey f o r p l o t s o i l depths which i n d i c a t e d s o i l water moni tor ing p r o f i l e s were t o o shal low on s e v e r a l p l o t s . In fo r -mation requ i red f o r r o o t d i s e a s e and bark b e e t l e dynamics l e d t o more cau t ious use of t h e smog i n j u r y scor ing procedure, a s well a s t o t h e dendrochrono- l o g i c a l a n a l y s i s o f t r e e r a d i a l growth.

A S t r u c t u r e f o r Complex I n t e r a c t i o n s

The e f f e c t s o f a i r p o l l u t i o n i n t h e f o r e s t eco-system a r e no t only t h e d i r e c t v i s i b l e e f f e c t s t h a t a casua l observer might n o t i c e by d i sco lo red f o l i a g e on t h e t r e e s , bu t a l s o l e s s apparent , b u t nonetheless r e a l , i n d i r e c t e f f e c t s t h a t a r e s u b t l y t r a n s f e r r e d through t h e system. Such i n d i r e c t c h a i n r e a c t i o n s can occur a t t h e l e v e l of i n d i v i d u a l t r e e s , a t t h e popula t ion l e v e l of t r e e s of a c e r -t a i n s p e c i e s , and because of changes i n t h e mixtures o f t h e l a t t e r over t h e long-term, changes which occur a t t h e whole community l e v e l . A s a map of how such changes can be t r a n s f e r r e d throughout t h e system, f i g u r e 1 d i s p l a y s some s i g n i f i c a n t p o r t i o n s of a f o r e s t ecosystem which must be considered. The re fe rence numbers a s soc ia ted wi th each component i n t h i s diagram p e r t a i n t o va r ious kinds of environmental cond i t ions and b i o l o g i c a l organisms impor- t a n t t o understanding changes occur r ing i n a f o r e s t ecosystem. These numbers a l s o re fe rence p a r t i c u l a r

I

OIHER L E M A L DEAD r R E E S

Figure 1--Components of t h e f o r e s t ecosystem d i r e c t l y and i n d i r e c t l y a f f e c t e d by photochemical a i r po l lu t ion .

r esea rch t o p i c s which have been s tud ied between 1973 through 1980 i n t h e San Bernardino National Fores t .

The purpose of t h i s overview is t o p resen t an i n t e g r a t e d , s i m p l i f i e d frame of re fe rence within which t h e d i s c o v e r i e s , r e s u l t s , and conclusions from the p r o j e c t may be viewed a s a whole.

While a f o r e s t i s more than simply a group of t r e e s , t h e l a t t e r is by d e f i n i t i o n t h e dominant l i f e form of such a system. Reference w i l l be made t o t h e numbers i n va r ious p a r t s of f i g u r e 1. To view t h e e f f e c t of a i r p o l l u t i o n (1) on a community of t r e e s , i t i s necessary t o consider s e v e r a l r e l a - t i v e l y s t a t i c s i t e and s o i l p r o p e r t i e s ( 7 ) , a s we l l a s very dynamic meteorological cond i t ions such a s a i r temperature and p r e c i p i t a t i o n ( 3 ) . s i n c e a l l of these may c o n t r i b u t e t o a s y n e r g i s t i c e f f e c t of a long-term, chronic a i r p o l l u t i o n exposure i n terms of t r e e response. Some of t h e p r e c i p i t a t i o n ( 3 ) , depending on s i t e and s o i l c h a r a c t e r i s t i c s ( 7 ) , e n t e r s t h e s o i l a s a v a i l a b l e s o i l water (2) f o r t r e e growth ( 3 , 9 ) . For l a c k of b e t t e r d a t a , we en-v i s i o n a i r temperature ( 3 ) a s a rough index of hea t a v a i l a b l e f o r enabl ing a v a i l a b l e s o i l water t o be depleted through water l o s t from t r e e l eaves t o t h e atmosphere through t r a n s p i r a t i o n .

Over t ime, and depending on s e n s i t i v i t y between and wi th in va r ious t r e e s p e c i e s , some of t h e green f o l i a g e ( 4 , 5 ) on t r e e s becomes i n j u r e d , d i sco lo red f o l i a g e ( 4 , 5 ) , and some of t h a t i s dropped from t h e t r e e s . Th i s , added t o normal amounts of needle shed a f f e c t e d by t h e a v a i l a b i l i t y of s o i l mois ture ( 2 ) , becomes a p a r t of ground l i t t e r ( 6 ) .

The r e l a t i v e amount of f o l i a g e t h a t changes from green t o in ju red i s thought t o have a bear ing on t h e r a t e of stem wood growth (8 ,g ) of t r e e s . These t h r e e responses a r e thought t o be assoc ia ted with t h e r a t e of production of cones and t h e r e f o r e seeds (13) f o r regenerat ion of new t r e e s . A s po l lu -t a n t s lead t o a g r e a t e r degree of f o l i a g e i n j u r y f o r some t r e e s p e c i e s , and stem growth i s reduced, otherwise mature i n d i v i d u a l s of these s p e c i e s produce l e s s and l e s s cones, i f any.

It has been mentioned how a i r p o l l u t i o n can i n - c rease t h e ground l i t t e r depths ( 6 ) . This is s i g n i -f i c a n t because seeds (1 3) of some t r e e s p e c i e s have a b i o l o g i c a l behavior which i s adapted t o lit-t l e o r no ground l i t t e r f o r sp rou t ing and surviv- i n g 3s seed l ings (14,15) dur ing dry summers ( t h e e f f e c t of a v a i l a b l e s o i l water (2) once aga in ) . Many cones, seeds , and small s e e d l i n a s a r e l o s t t o w i l d l i f e of var ious forms under n a t u r a l condi t ions . Any f u r t h e r reduct ion i n t h i s reproduct ion chain because of a i r p o l l u t i o n e f f e c t s can make continued replacement of some t r e e spec ies a very p reca r ious circumstance.

Those seed l ings t h a t do survive t h e f i r s t few years even tua l ly grow t o a l a r g e r s i z e o f t e n c a l l e d s a p l i n g s (1 6) i n t h e populat ion s t r u c t u r e . The ex-t e n t t o which t h e e f f e c t of a i r p o l l u t i o n r e t a r d s stem growth (8.9) simply tends t o keep t r e e s i n t h i s s i z e range f o r a longer t ime, s u b j e c t t o t h e many causes of death which can occur. Eventual ly , some sap l ings grow i n t o l a r g e r s i z e s which a r e mature (16) and p o t e n t i a l l y capable of producing cones, a s wel l a s b e i n v a l u e d f o r e s t h e t i c purposes and a s

p o t e n t i a l l y merchantable t imber. Those mature t r e e s t h a t develop a s i g n i f i c a n t

degree of v i s i b l e f o l i a g e i n j u r y ( 4 , 5 ) a r e some- t imes c u t down whether l e g a l l y o r by poaching. This produces stumps. I t has been discovered t h a t t h e degree of f o l i a g e i n j u r y ( 4 , 5 ) , namely t h e younger t h e age of t h e o l d e s t need les , i s s i g n i f i c a n t l y c o r r e l a t e d with t h e inc idence of i n f e c t i o n and co l - o n i z a t i o n of such stumps by t h e roo t r o t d i s e a s e (10) Fomes annosus, i f t h e f r e s h stumps a r e no t t r e a t e d e n t h e l i v e t r e e i s f i r s t c u t . One would ha rd ly be concerned about t h i s i f i t were n o t f o r t h e obse rva t ion t h a t such d i s e a s e s can spread from dead stump roo t systems i n t o ad jacen t l i v e t r e e roo t systems, from s e e d l i n g s , up t o l a r g e , mature, p o l l -u t i o n - r e s i s t a n t t r e e s , depending on t h e s p a t i a l d e n s i t y of t h e s t and . When t h i s does happen wi th t h e l a t t e r , and those t r e e s a l r e a d y have a consider-a b l e degree of i n j u r e d f o l i a g e ( 4 , 5 ) , then, espec-i a l l y on ponderosa pine , bark b e e t l e s (1 1 ) appear b e t t e r a b l e t o s u c c e s s f u l l y a t t a c k and k i l l such t r e e s . M o r t a l i t y surveys show numerous o t h e r pat - t e r n s o f d i s e a s e and i n s e c t combinations (1 2) a l s o a c t t o k i l l t r e e s . Reduced growth cannot be sus-t a ined i n d e f i n i t e l y , and t h e l e n g t h of t ime of re-duced growth p r i o r t o dea th appears t o be age- dependent.

Over t ime , t h e complexion of t h e f o r e s t ecosystem w i l l change according t o which t r e e s p e c i e s a r e b e s t a b l e t o r e s i s t t h e agen t s t h a t cause dea th ( 1 6 ) , whether n a t u r a l o r human-caused, and a r e a l s o capable of providing new young s e e d l i n g s (1 4,15) a b l e t o s u r v i v e t o ma tu r i ty . I n many cases , t h e evidence seems t o i n d i c a t e t h a t t h e balance between va r ious t r e e s p e c i e s i s s h i f t i n g d ramat ica l ly i n t h e San Bernardino Nat ional F o r e s t .

Given t h r e e d i r e c t e f f e c t s of a i r p o l l u t a n t s on f o r e s t growth, namely f o l i a r i n j u r y and acce le ra ted need le c a s t , woody growth reduc t ion , and i n d i r e c t l y inc reased m o r t a l i t y , t h e s e e f f e c t s might be t i e d t o g e t h e r i n t h e fol lowing scenar ios of ecosystem- l e v e l e f f e c t s .

Ecosystem Dynamics Under a S i n g l e S t r e s s

F o l i a r I n j u r y Consequences-- F o l i a r i n j u r y and premature shedding of p a s t y e a r ' s needles w i l l slow down t h e n a t u r a l development of canopy c l o s u r e i n a s tand. It has been shown and repea ted ly confirmed t h a t a s a s t a n d grows, l e a f a r e a expands u n t i l i t reaches a p l a t e a u , a t which it remains f o r t h e r e -mainder o f t h e l i f e of t h e s t and ( ~ r i e r and o t h e r s 1978) ( f i g . 2 ) . Stand growth, developmental p a t t e r n s and t ime t o m a t u r i t y a r e e n t i r e l y dependent upon t h e r a t e o f canopy c losure . Net product ion by con i fe rous f o r e s t s i s r e l a t e d t o l e a f a r e a (Whit taker and Nier ing l975) , and a l l o t h e r t h i n g s being equa l , t h e g r e a t e r t h i s l e a f a r e a , t h e g r e a t e r i s t h e p r o d u c t i v i t y . Once maximal l e a f a r e a (cano-py c l o s u r e ) i s ob ta ined , o t h e r ecosystem func t ions begin t o make major q u a l i t a t i v e changes, a s d i scuss - ed below. I f time t o canopy c l o s u r e i s inc reased , no t only a r e p r o d u c t i v i t y r a t e s reduced, but a l s o q u a l i t a t i v e e c o l o g i c a l changes may occur.

Since f o r e s t f o l i a g e always t ends toward form- i n g a cont inuous , complete s u r f a c e a r e a , t h e degree of completion r e p r e s e n t s t h e degree of occupancy of t h e s i t e . A v igorous , h e a l t h y s t and o f t r e e s w i l l

STAND AGE- YEARS

Figure 2--Natural f o r e s t s t and canopy c losure .

achieve occupancy o f an open s i t e a t about 12 y e a r s of age, e s t a b l i s h i n g dominance over competing vege- t a t i o n , and w i l l mainta in occupancy u n t i l a t l e a s t middle age (smith 1962). A given genera t ion o f t r e e s u l t i m a t e l y l o s e s command of t h e s i t e , g iv ing way t o younger members and/or o t h e r spec ies . A'for-e s t canopy exper iencing pol lu t ion-caused i n j u r y might no t be a b l e t o f u l l y e s t a b l i s h occupancy of t h e s i t e . The amount o f accompanying vege ta t ion , e s p e c i a l l y of an unders tory n a t u r e , might i n d i c a t e t h e degree t o wh'ich t h e main s tand f a l l s s h o r t of f u l l occupancy.

Growth Reduction Consequences-- Leaf a r e a i s d i r e c t -l y r e l a t e d t o woody product ion i n a f o r e s t s t a n d , a s mentioned. Impediments t o l e a f a r e a expansion and canopy c l o s u r e might a f f e c t t h e o v e r a l l p a t t e r n of woody growth i n a s tand. S tud ies have shown t h a t second-year needles a r e more important i n providing photosynthate f o r stem growth, while c u r r e n t y e a r needles c o n t r i b u t e p r i m a r i l y t o shoot and need le e longa t ion (walker and o t h e r s 1972); t h e second yea r needles a r e t h e most impacted by a i r po l lu - t i o n . Trees might cont inue t o put on h e i g h t growth a t t h e expense of d iameter growth f o r a longer period of time than with a normally c l o s i n g canopy, both because of a l a c k of photosynthate f o r stem growth and because t h e open canopy f o s t e r s r a p i d h e i g h t growth r a t e s . However, because growth and p r o d u c t i v i t y i s suppressed, both he igh t and diame- t e r growth r a t e s i n genera l would be much s lower than normal.

I t i s a t e n e t o f s i l v i c u l t u r e t h a t changes i n s tand d e n s i t y do no t s i g n i f i c a n t l y a l t e r t h e t o t a l amount of d ry mat t e r o r stem wood produced by a s tand. Thus, precommercial th inn ings do no t marked- l y change production r a t e s but r a t h e r add t h e same amount of wood t o a l e s s e r number o f t r e e s ( smi th 1962). Mathematically, mean p l a n t s i z e m u l t i p l i e d by d e n s i t y tends toward a cons tan t . This r e l a t i o n - s h i p has been confirmed t o hold t r u e f o r many veae- t a t i o n types , inc lud ing f o r e s t s t a n d s (cooper 1961). I n a p o l l u t i o n s t r e s s e d f o r e s t , however, one might expect t h e r e l a t i o n s h i p e i t h e r t o be weak, o r t o break down a l t o g e t h e r ( f i g . 3 ) . A t low dens i -

I -unstressed forest

STAND DENSITY - TREES/ ACRE

Figure 3--Relation between stand dens i ty and average t r e e s i z e with and without a i r pol lut ion.

t i e s , mean p lan t s i z e i s not remarkably l a rge a s t he t r e e s a r e not i n good vigor; a t high dens i t i e s , p lan t s i z e i s suppressed even more than would be expected due t o dens i ty e f f ec t s alone. I n especial- l y damaged and open s tands , the r e l a t i onsh ip might be expected t o break down. The functioning of t he r e l a t i onsh ip i s dependent upon t r e e s exer t ing an inf luence over each other . I f a l l t r e e s a r e gener- a l l y weakened i n competitive a b i l i t y , t h e i r growth w i l l depend more on l im i t a t i ons imposed by t he phy- s i c a l environment and l e s s on i n t e r - t r e e inf luences. An open stand with highly var iab le t r e e s i z e s might be t he r e s u l t .

Tree Mortal i ty Consequences-- Typical ly , a stand of t r e e s achieves a dens i ty i n balance with t he physi- c a l environment by means of death of l e s s competi- t i v e t r e e s i n t he s tand. Thus, t he r e i s general ly a continuous decl ine i n stand dens i ty with increasing stand development. I n a pol lut ion-stressed for -e s t , one f i nds t he phenomenon of s e l ec t i ve mortal i - ty . However, t he magnitude of the mor ta l i ty can be g r ea t e r and t he cause i s o ther than simple competi- t i v e s t r e s s . A s young t r e e s prematurely age, t aper off i n growth, and d i e , more openings a r e created i n the canopy. While i n a heal thy f o r e s t t h i s provides room f o r t he dominant t r e e s t o expand, i n pol lut ion-stressed f o r e s t s t he open canopy i s open-ed fu r the r . Even i f t he po l lu t ion should be removed from the system, a lower stand dens i ty because of increased mor ta l i ty r a t e s requi res a g r ea t e r time t o develop a f u l l canopy than would a stand with a more normal s tocking r a t e .

Po t en t i a l Responses Under Multiple S t resses

Dolan and Hayden (1978) c l a s s i f i e d types of changes i n nature reserve park ecosystems a s e i t h e r steady s t a t e , eddy s t a t e , o r t rend s t a t e . Steady s t a t e changes include d iurna l and seasonal environmental changes under which t he system has evolved. Eddy s t a t e changes a r e d i s c r e t e pulses of environmental dis turbances. Trend s-cate changes a r e long- term changes t h a t a r e of ten t he most sub t l e t o de- t e c t , a s well a s t he most d i f f i c u l t from which t o

pro tec t na tura l landscape ecosystems i f those changes a r e associated with human inf luences. Ef fec t s of a i r po l lu t ion on f o r e s t s can have t h i s trend s t a t e nature. A Worst-case Scenario of Future Forest Change-- I t could be i n s igh t fu l t o i n t eg ra t e t he present s t a t e of ecological understanding on combinations of trend s t a t e changes i n an attempt t o see what a possible worst-case scenario might be f o r vegetat ion i n western coniferous fo r e s t s . The r e l a t i v e order of s e n s i t i v i t y , conceived as probabi l i ty of mortal- i t y associated with a pa r t i cu l a r environmental s t r e s s , i s of ten d i f f e r en t (even opposite) between various species f o r one s t r e s s , compared t o another. Ranking t r e e species of mature ind iv idua ls i n terms of l i k e l y mor ta l i ty t o f i r e would place ponderosa and lodgepole pine a s "low", while white f i r and incense cedar would of ten be rated "high". The l a t - t e r would be k i l l e d by a moderate i n t e n s i t y sur face f i r e (not a prescibed burn necessar i ly ) .

I n con t r a s t , research on ambient oxidant a i r po l lu t ion s e n s i t i v i t y has shown ponderosa pine as very s ens i t i ve , while white f i r and incense cedar might have a low s e n s i t i v i t y t o t h i s s t r e s s . A i r po l lu t ion weakens c e r t a i n t r e e species which a r e subsequently h i t by b i o t i c d i seases and i n s e c t s , and produces a decreased competitive advantage, compared t o l e s s s ens i t i ve species . I n t he commun-i t y , t h i s can lead t o decreased longevi ty of the s ens i t i ve species .

A s a worst case condition, one could envision t h a t our present western f o r e s t her i tage from pr i s - t i n e decades ago under a na tura l f i r e frequency sh i f t ed t he balance of t r e e spec ies composition such t h a t i t was heavi ly proportioned with what a r e now a i r po l lu t ion s ens i t i ve species . I f t he a i r pollu- t i o n problem i n t e n s i f i e s over t he years , these species can be expected t o be decimated. The combined e f f ec t of both of these trend s t a t e changes, each working on d i f f e r e n t t r e e spec ies , micht make it impossible t o preserve and protect coniferous f o r e s t s i n c e r t a i n loca t ions ( f i g . 4).

A I R 4

SENSITIVE,

FIRE-

TOLERANT

SPECIES

ABUNDANCE

v

0 A I R POLLUTION-TOLERANT.

FIRE- SENSITIVE SPECIES A B U N D A N C E

Figure 4--Possible fu ture course of f o r e s t spec ies composition under combined s t r e s s of a i r po l lu t ion and na tura l f i r e exclusion.

CONCLUSIONS

In t h e case of a i r p o l l u t i o n , t h e r e could be t h e gradual e l imina t ion of many f i r e - t o l e r a n t t r e e spe- c i e s from f o r e s t s . Whenever a n a t u r a l f i r e does oc-cur under such a f u t u r e scenar io , t h e proport ion of f o r e s t s tand spec ies i n t h e f i r e - s e n s i t i v e cate-gory could be much h igher than normal, and sudden q u a l i t a t i v e changes, o r ecosystem ca tas t rophes , i n c o n i f e r f o r e s t s p e c i e s composition could be expected. There i s a s t rong l ike l ihood t h a t c o n i f e r s t ands might change i n t o mixtures of deciduous t r e e and shrub communities a t mid-elevations, and perhaps scrub f i e l d ecosystems a t higher e leva t ions which presen t ly con ta in c o n i f e r f o r e s t s . This would repre-s e n t a q u a l i t a t i v e change from one successional pat- t e r n t o another , and i s a p o s s i b i l i t y which f o r e s t management has a r e s p o n s i b i l i t y t o t r y t o evaluate .

Acknowledgments: This s tudy was funded i n p a r t with f e d e r a l funds

from t h e Environmental Pro tec t ion Agency under Contract Numbers 68-03-0273, 68-03-2442, and Grant Number R805410. The content of t h i s paper i s not t o be construed a s represent ing views o r p o l i c i e s of t h e EPA, nor a s a concurrence of t h e Agency with t h e r e s u l t s presented. Mention of t r a d e names o r commercial products i n t h i s paper does not c o n s t i t u t e e i t h e r an endorsement o r a recommendation f o r t h e i r use. This paper does not represen t EPA pol icy , p o s i t i o n , o r f indings.

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Gr ie r , C . C . , R.L. Edmonds, R.H. Waring and D.W. Cole. 1978. Fores t management impl ica t ions of

p roduc t iv i ty , n u t r i e n t cycl ing and water r e l a t i o n s research i n western con i fe r s . p.96-106 In: Proc., J n t Conv. of S.A.F. and Can. I n s t . For. , 1978.

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Kicker t , R.N. 1980. Ecosystem simulat ion modeling. Chpt. 2

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Sons, New York. 578p.

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U.S. Environmental Pro tec t ion Agency. 1979. EPA changes ozone s tandard t o 0.12 ppm.

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review. pp.211-225 In: Proc., Res. on Coniferous Fores t Ecosystems Symp., Bellingham, WA. March 23-24, 1972.

Whittaker, R.H. and W.A. Niering. 1975. Vegetation of t h e Santa Cruz Mountains,

Arizona. V. Biomass, production and d i v e r s i t y along t h e e leva t ion gradient . Ecol. 56:771-790.

Response of Plant Communities to Air Pollution1

R. Guderian and K. ~ u e ~ ~ e r s *

Abstract : Under the in f luence of a i r p o l l u t i o n two r e t r o g r e s s i v e processes a r e s e t i n motion i n p l a n t com-muni t ies : By means of d i r e c t and i n d i r e c t e f f e c t s , changes occur i n s t r u c t u r e and funct ion of the community leading up t o t o t a l des t ruc t ion . P a r a l l e l t o t h i s degradat ion ( r e t r o g r e s s i o n ) is a spontaneous o r man i n i -t i a ted process dur ing which t h e p r i g i n a l adap t ive r e - s i s t a n t members of t h e e x i s t i n g community a s we l l a s new a r r i v a l s undergo secondary succession. The causes and mechanisms f o r a i r pollution-induced changes i n p l a n t communities a r e demonstrated by means of l i t e r -a t u r e a n a l y s i s and the i n t e r a c t i o n of dose response determining f a c t o r s a r e summarized. I n order t o empha- s i z e t h e e x i s t i n g p o t e n t i a l danger and t o s e t remedial procedures i n motion, r esea rch themes a r e pointed out t h a t must r ece ive immediate a t t e n t i o n .

Thus f a r r esea rch on the e f f e c t s of a i r pol- c e r t a i n inheren t p a t t e r n s of t h e conf ron ta t ion l u t a n t s on p l a n t s has been centered on homotyp- between p l a n t communities and a i r p o l l u t i o n i c a l populat ions of economically important may be deduced. spec ies , With t h e development of long-term For t h e following comparative s tudy of t h e loading of ex tens ive a r e a s e n t i r e ecosystems inf luence of varying concen t ra t ions of a i r a r e a l s o inc reas ing ly being inf luenced by a i r p o l l u t a n t s on vege ta t ion , a d i v i s i o n i n t o t h e p o l l u t a n t s . From t h i s , t h e ques t ion a r i s e s fol lowing l e v e l s , derived from Smith's c l a s -a s t o t h e poss ib le r e a c t i o n s of phytocoenoses s i f i c a t i o n (1974) seems p r a c t i c a l : h igh, in -t o changed a i r q u a l i t y a s a new h a b i t a t f a c t o r . termediate and low dosage e f f e c t s .

REACTIONS OF PLANT COMMUNITIES RELATED TO High P o l l u t i o n Dosage AIR POLLUTANT CONCENTRATIONS

A c h a r a c t e r i s t i c of t h e r e l a t i o n s h i p be- S ing le o r repeated observat ions i n t h e v i - tween high dosage and t h e r e a c t i o n of a p l a n t

c i n i t y of s i n g l e sources a s w e l l a s wi th in and community is a breakdown of community s t r u c - ou t s ide of extended regions subjected t o a i r t u r e -- more or l e s s obvious depending on t h e p o l l u t i o n load can only provide momentary r e - complexity of t h e ecosystem. The degradat ion cords o r sequences of changes under t h e respec- of t h e system is charac te r i zed by a rap id change t i v e l o c a l cond i t ions . I n general , however, i n s t r u c t u r e , including composition. It is

accompanied and f i n a l l y replaced by a second-a r y success ion which can lead t o a new e q u i l -

~ r e s e n t e d a t t h e Symposium on E f f e c t s of Air ibrium under sus ta ined load.

P o l l u t a n t s on Mediterranean and Temperate Fores t Direct a c u t e and chronic i n j u r y appearing

Ecosystems, June 22-27, 1980, Rivers ide , e s p e c i a l l y on l eaves , bu t no t always cor re -

C a l i f o r n i a , U.S.A. l a t e d with t h e i r p o l l u t a n t con ten t , (Guderian, 1970; Linzon, 1979) w i l l f i r s t a f f e c t t h e most

2 ~ e s p e c t i v e l y , Biowissenschaften, Universi- s e n s i t i v e spec ies of t h e t r e e s t ra tum i n a t a t Essen, Gesamthochschule, 4300 Essen 1, f o r e s t and can l ead t o t h e t o t a l d e s t r u c t i o n of West Germany t h e canopy. Without p ro tec t ion from t h e f r e e l y

--

e n t e r i n g a i r masses of p o l l u t e d a i r (Bennett and H i l l , 1975) sh rub , he rb and moss o r l i c h e n lay- e r s a r e des t royed one a f t e r ano the r , u n t i l a ba r ren zone r e s u l t s (Gordon and Gorham, 1963; Woodwell, 1970). As an example of such condi- t i o n s , t he zonat ion under t h e i n f l u e n c e of ap-proximately 10 tons of SO2 per day from an i r o n o r e r o a s t i n g fu rnace i n B ie r sdor f (Germany) w i l l be desc r ibed b r i e f l y .

The denuded zone i n the immediate v i c i n i t y of t h e emission source i s surrounded by the t r a n s i -t i o n zone wi th i s o l a t e d c l u s t e r s of g r a s s (Des-champsia f l exuosa ) and r e s i s t a n t ground c o v e r (Er ica c i n e r e a , Galium mollugo, Veronica o f f i c i n - a l i s , Rumex a c e t o s a , and Conva l l a r i a m a j a l i s ) . Now and then one a l s o encounters the r e l a t i v e l y r e s i s t a n t Sambucus racemosa and Rhamnus f r angu la i n t h i s zone. I n t h e g r a s s cover of v e g e t a t i o n c o n s i s t i n g mostly of Deschampsia f l exuosa t h e f i r s t shoo t s of Quercus p e t r a i a a r e e s t a b l i s h e d i n t h e s h e l t e r of t h e herbaceous v e g e t a t i o n . The popu la t ions of t h i s oak and Fagus s i l v a t i c a which a d j o i n t h e s tun ted f o r e s t zone show s i g n s of d i s i n t e g r a t i o n s t a r t i n g a t t h e p e r i - phery. As SO2 loading dec reases t h e s p e c i e s d i v e r s i t y i n c r e a s e s , u n t i l f i n a l l y i t r eaches t h e combination t y p i c a l f o r the a c i d i c s o i l - mixed f o r e s t (Fago-Quercetum).

A comparison wi th o t h e r s t u d i e s (Treshow, 1968; Smith, 1974; M i l l e r and McBride, 1975; and, Linzon, 1978) shows t h a t t h i s i s t he typ-i c a l p i c t u r e of t h e break-down of a p l a n t com-munity, t h a t i s , a change i n s p e c i e s composit ion toward a s i m p l i f i c a t i o n of t h e system. I n p r i n c i p l e i t does n o t d i f f e r from t h a t caused by gamma r a d i a t i o n (Woodwell, 1963, 1970). The secondary success ion which s e t s i n a s soon a s t h e o r i g i n a l v e g e t a t i o n begins t o change l e a d s i n t ime under c o n s t a n t loading t o t h e format ion of new, l e s s complex s t a b l e s t r u c t u r e s . Thus, i n an o l d manufacturing d i s t r i c t of Upper S i l e s i a (Poland), i n l o c a t i o n s once stocked wi th n a t i v e c o n i f e r o u s o r mixed deciduous f o r e s t s , Wolak (1977 and 1979) desc r ibed a s t a b l e zon- a t i o n i n r e l a t i o n t o d i f f e r e n t loads of S02, z i n c , and l ead . Under heavy loads an i n d u s t r i a l waste land i s followed by a g r a s s zone wi th a s s o c i a t i o n s dominated by Deschampsia f l exuosa on o l i g o t r o p h i c sand, by Calamagrost is e p i g e i o s on mesotrophic s i t e s , and by Calamagrost is a-l o s a on damp o rgan ic s o i l . I n t h e ad jacen t -shrub zone one f i n d s both c u l t i v a t e d and v o l - un tee r scrub t r e e spec ies . It i s remarkable t h a t P inus s i l v e s t r i s can t a k e on t h e shape of a c reep ing shrub o r of a t r e e wi th branches p r o j e c t i n g h o r i z o n t a l l y up t o 5 m from t h e stem. These dwarf forms a r e no more than 2 m h igh a t an age of 30 t o 50 y e a r s . On low grade sands groups of t h e desc r ibed Pinus s i l v e s t r i s forms and Solanum dulcamara were found which were n o t found i n s i m i l a r l o c a t i o n s wi thout t h e s t r o n g i n f l u e n c e of a i r p o l l u t i o n . Those p l a n t communities a r e c a l l e d indus t r io -c l imax communities (Wolak, 1971). They r e p r e s e n t spon-taneous a s s o c i a t i o n s wi th r e l a t i v e l y cons tan t s p e c i e s composit ion which have developed grad- u a l l y through indust r iogenous (secondary)

success ion, both from spec ies p r e s e n t b e f o r e p o l l u t a n t loading a s w e l l a s from new a r r i v a l s , under t h e combined in f luence of t h e h a b i t a t f a c t o r s ; c l i m a t e , s o i l , i n s e c t s and p a r a s i t e s - - dominated by the f a c t o r a i r p o l l u t i o n .

In t e rmed ia te P o l l u t i o n Dosage

In termedia te a i r p o l l u t i o n dosage c o n d i t i o n s a r e e c o l o g i c a l l y s i g n i f i c a n t because t h e i r sub- t l e , d i r e c t and i n d i r e c t e f f e c t s on t h e i n d i v i - dua l spec ies can s e t t h e s t a g e f o r changes i n t h e s t r u c t u r e of t h e community wi th p o s s i b l y ir-r e v e r s i b l e consequences. I n p l a n t communities exper iencing in t e rmed ia te p o l l u t i o n dosage, in -t e r r u p t i o n of growth and rep roduc t ion processes a s w e l l a s impairment of t h e v i t a l i t y of i n d i -v i d u a l p l a n t s , among o t h e r f a c t o r s through in - creased v u l n e r a b i l i t y t o a b i o t i c and b i o t i c s t r e s s , become p a r t i c u l a r l y important (Wentzel, 1965; Huttunen, 1979; and Laurence, 1980).

I n p ine and spruce popu la t ions i n t h e Lower Main Region (Germany), which indeed show an in -c reased s u l f u r con ten t i n t h e l eaves , b u t d i d n o t y e t d i s p l a y an abnormal l o s s of i n d i v i d u a l s , morphological changes such a s t h i n crowns coup- l e d wi th s h o r t e r need les were d e t e c t e d i n o l d e r s t ands (Wentzel, 1979). Such changes occur slow-l y and only t h e accumulation of annual e f f e c t s g radua l ly l eads t o h i g h e r morbidi ty (Wentzel, 1980). I n t h i s c o n t e x t the carry-over of ac-cumulated t o x i c a n t s i n t h e new shoo t s of t h e nex t growing season should be mentioned (Ke l l e r , 1978; P res ton , 1979). A s l i g h t change of t h e h o r i z o n t a l s t r u c t u r e i n t h e canopy w i l l i n f l u - ence such h a b i t a t f a c t o r s a s t h e supply of l i g h t and p r e c i p i t a t i o n f o r the lower-lying vege ta t ion . F requen t ly , t he i n t e r a c t i o n of changed s o i l r e -action--pH--and t o x i c a n t c o n t e n t b r i n g s about a r e s t r u c t u r i n g of t h e shrub and herb s t r a t a over extended a r e a s sometimes i n f l u e n c i n g na- t u r a l reproduct ion of woody s p e c i e s (Lux, 1964; Wentzel, 1971; Harward and Treshow, 1975)

Such changes i n t h e composit ion of p l a n t communities were d e t e c t e d through v e g e t a t i o n surveys caused by a complex of f a c t o r s . For example, c e r t a i n s p e c i e s were found i n dense c l u s t e r s , wh i l e o t h e r s were evenly d i s t r i b u t e d and s t i l l o t h e r s were t o t a l l y absen t , depending on dosage (Borgsdorf, 1960; Gordon and Gorham, 1963; Nik l fe ld , 1967; Ionescu, e t a l . , 1971; Trautmann, e t a l . , 1971). Hajduck (1961) t a l k s about p o s i t i v e o r n e g a t i v e p h y t o i n d i c a t o r s , wh i l e Anderson (1966, quoted i n Treshow 1968) employs the terms " inc rease r " o r "decreaser .' I

The concept of phy to ind ica to r s i s e s s e n t i a l l y t h e same a s b i o i n d i c a t i o n w i t h l i c h e n o r moss s p e c i e s (Le Blanc and Rao, 1975; Taoda, 1977; and P i l egaa rd , 1978). Ka le t a (1972) was a b l e t o demonstrate i n a d d i t i o n t h e dynamics of change of whole p l a n t a s s o c i a t i o n s under t h e in f luence of magnesite.

Brandt and Rhoades (1972, 1973) took t r e e s p e c i e s of s e v e r a l s t r a t a i n t o c o n s i d e r a t i o n i n t h e i r s tudy on t h e i n f l u e n c e of l imestone d u s t on a f o r e s t community. This method made

i t p o s s i b l e t o a s s e s s t h e t r end of f u t u r e success ion , e s p e c i a l l y through s h i f t s de tec ted i n t h e s p e c i e s d i v e r s i t y of t h e s e e d l i n g and s p r o u t d a t a . Thus, Quercus coccinea , Quercus v e l u t i n a o r T i l i a americana oan drop ou t a s members of t h e oak-chestnut a s s o c i a t i o n and Lir iodendron t u l i p i f e r a , & saccharinum and p o s s i b l y Quercus muehlenbergii could become dominant spec ies . Through t h i s example it a l s o becomes e v i d e n t how a i r p o l l u t a n t s can in f luence t h e makeup of phytocoenoses by i n - f luenc ing reproduc t ion (Wentzel, 1963; Karnoskv, and S t a i r s , 1974; K e l l e r , 1976).

McClenahen (1978) u t i l i z e d community comp- o s i t i o n a s a means t o i n v e s t i g a t e changes i n p l a n t communities a long a p o l l u t i o n g r a d i e n t i n t h e Ohio Val ley (USA). I n t h i s s tudy, an e a s t e r n deciduous f o r e s t exper iencing interme- d i a t e dosages was shown t o d e c l i n e i n s p e c i e s r i c h n e s s , evenness, and Shannon d i v e r s i t y in - dex w i t h i n a l l s t r a t a of t h e community, p a r t - i c u l a r l y i n those l o c a t i o n s exper iencing t h e h i g h e s t r e l a t i v e dose. Simultaneously, t h e s i m i l a r i t y i n composit ion decreased wi th i n - c r e a s i n g dosage. Thus, t h e r e l a t i v e importance of saccharinum, a s p e c i e s s l i g h t l y s t im- u l a t e d by l imestone d u s t (Brandt and Rhoades, 1972), showed d i s t i n c t d e c l i n e i n a l l s t r a t a , whi l e t h e importance of Aesculus octandra in - c reased . Opposing tendencies i n d e n s i t y were observed i n some s t r a t a . A d e c l i n e i n t h e t r e e and h e r b s t r a t a was accompanied by an i n c r e a s e of t h e subcanopy and t h e shrub s t r a t a . This can be a t t r i b u t e d t o b e t t e r l i g h t cond i t ions i n t h e lower s t r a t a combined wi th a r e l a t i v e i n - c r e a s e of herbs i n t o l e r a n t t o shade.

Low P o l l u t i o n Dosage

The e f f e c t s of low dosages on vege ta t ion l i e i n t h e borde r zone between t h e f l u c t u a t i n g s t a t e s of normal, i . e . , una f fec ted v e g e t a t i o n on t h e one hand, and s i g n i f i c a n t i n j u r i o u s e f - f e c t s on t h e o t h e r hand. Depending upon t h e r e s p e c t i v e p o l l u t a n t , i t s concen t ra t ion and d u r a t i o n of a c t i o n , a s w e l l a s t h e a f f e c t e d ob- j e c t and t h e l o c a l c o n d i t i o n s , t h e s e e f f e c t s can range from i n c r e a s e s t o r educ t ions i n growth, r ep roduc t ive c a p a b i l i t y o r q u a l i t y of p l a n t s . Under p r a c t i c a l c o n d i t i o n s such e f f e c t s can be d e t e c t e d t o only a c e r t a i n degree of t h e a c t u a l i n t e n s i t y . The d e t e c t i o n l i m i t h a s been low- e red through t h e development of new exposure systems w i t h f i l t e r e d and u n f i l t e r e d a i r (Mandl, e t a l . , 1973; Lee, e t a l . , 1973; M i l l e r , e t a l . , 1979; Shinn, e t a l . , 1979). However, measure-ment of p o l l u t a n t e f f e c t s on p l a n t communities occupying l a r g e reg ions p r e s e n t s p a r t i c u l a r d i f f i c u l t i e s because t h e necessary p o l l u t i o n - f r e e c o n t r o l a r e a s w i t h comparable s o i l and c l i m a t e a r e n o t a v a i l a b l e .

Before d e t e c t a b l e r educ t ions occur i n pro- d u c t i v i t y o r a l t e r a t i o n of environmental con- d i t i o n s can b e observed, t h e r e a r e va r ious changes t h a t a r e induced a t t h e p l a n t biochem- i c a l , phys io log ica l o r s u b s t r u c t u r a l l e v e l

(Ke l l e r , 1974; Jager and Klein , 1977; Horsman and Wellburn, 1977; and, Raabe and Kreeb, 1979). Of course t h e ques t ion of how much such f indings r e v e a l about t h e economic and eco log ic performance of a p a r t i c u l a r p l a n t s p e c i e s remains of c e n t r a l importance here . Some of t h e r e - a c t i o n s undoubtedly have no e f f e c t s on t h e t o t a l organism; even i f s i g n i f i c a n t e f f e c t s a r e found, it i s very d i f f i c u l t t o e s t a b l i s h a c a u s a l l i n k t o t h e primary responses mentioned above. The p o s s i b l e e f f e c t s of low dosage on p l a n t com-muni t i e s , f o r example, through changes i n i n - t e r s p e c i f i c compet i t ion, a r e a lmost t o t a l l y unresolved. The f i l t e r i n g e f f e c t s of vege ta t ion is an important process bu t t h i s t o p i c w i l l only be introduced he re .

A s shown i n t h e S o i l i n g p r o j e c t (Ul r i ch , e t a l . , 1978) o r t h e Hubbard Brook s tudy (Bormann and Likens, 1979) v e g e t a t i o n can f i l t e r l a r g e amounts of p o l l u t a n t s ou t of t h e atmosphere wi thout showing s i g n s of e x t e r n a l i n j u r y o r growth depress ion. P a r t i c u l a t e and gaseous p o l l u t a n t s e n t e r a n ecosystem through adsorp- t i o n and absorp t ion mainly on l e a f s u r f a c e s a s w e l l a s s o i l and water s u r f a c e s ( H i l l , 1971; Bennett and H i l l , 1975; and, Olsen, 1976). The s p e c i f i c behavior of t h e substance i s important f o r t h e p o s s i b l e long-term e f f e c t s of low do-, sage on p l a n t communities. P o l l u t a n t s which a r e s u b j e c t t o r a p i d decomposition such a s ozone o r PAN take e f f e c t through t h e summation of d i r e c t e f f e c t s . NOx, NH3, o r s u l f u r compounds can be channeled i n t o t h e n u t r i e n t c y c l e and may des t roy t h e balance of e s p e c i a l l y s e n s i t i v e ecosystems, such a s moors, through eu t roph i - c a t i o n ( P o r t e r , e t a l . , 1972; Cowling and Lock- y e r , 1976). The importance of a c i d p r e c i p i t a t i o n i n t h i s con tex t i s no t y e t c l e a r (Braekke, 1976; and, T a m , 1976). Accumulating substances such a s heavy meta l s , r e p r e s e n t a s p e c i a l danger f o r ecosystems (Kraemer, 1976; and Guderian, 1980). S o i l samples and ana lyses of moss specimens have revea led t h a t a cons tan t inpu t i n t o ecosystems is o f f s e t by only a l i m i t e d expor t , and t h a t t h i s i s now occur r ing over wide a r e a s (Huckabee, 1973; Ruhling and Ty le r , 1973; and Grdzinska, 1978). Such components can a l s o endanger t h e n u t r i e n t c y c l e (Mags, 1977 and Uba, 1977); f u r t h e r , they reduce t h e number and a c t i v i t y of decomposers, thereby impair ing remineral - i z a t i o n a s a requirement f o r un in te r rup ted biogeochemical c y c l e s (Taylor , 1975; and, Greszta , e t a l . , 1979). Espec ia l ly , wi th accumulating substances and under continuous loading, it i s only a ques t ion of t ime be fo re t h e d i r e c t and i n d i r e c t e f f e c t s descr ibed above begin t o in - t e r r u p t t h e s t r u c t u r e and func t ion of p l a n t communities.

THE INFLUENCE OF POLLUTANTS ON THE FUNCTION OF PLANT COMMUNITIES

Changes i n p l a n t communities caused by pol- l u t a n t s can l ead t o more o r l e s s l a s t i n g impairment of economic and eco log ic func t ions depending on t h e dosage. The damage t o a g r i c u l t u r e

--

through growth reduct ion, l o s s of q u a l i t y and higher l abor c o s t s have long drawn consider- ab le a t t e n t i o n , bu t only now i s an a t tempt being made t o t ake the e f f e c t s on performance of ecosystems i n t o account. I n t h i s connec-t i o n , an e s p e c i a l l y important quest ion i s how p o l l u t a n t s a f f e c t such func t ions of vege ta t ion a s f i l t e r e f f e c t , s t a b i l i z a t i o n of c l imate , r egu la t ion of water and n u t r i e n t cyc les , s o i l conservat ion a s we l l a s the p rese rva t ion of l i v i n g space f o r polymorphic zoo- and phyto- ceonoses. Extensive changes i n vege ta t ion cover a r e probably l inked t o i n t e r r u p t i o n o r even t o t a l breakdown of a l l t h e above-men- t ioned func t ions . For example, the func t ion of p l a n t communities a s p r o t e c t i o n aga ins t e ros ion o r a s a f a c t o r i n counter balancing excess ive temperature f l u c t u a t i o n s and the accompanying danger from l i g h t f r o s t dur ing bud break i s considerably more impaired i n a r e a s experiencing high p o l l u t a n t dosage where woods have been replaced by sparse vege ta t ion than i n unpolluted a r e a s . Cur ren t ly , t o what ex ten t in termediate and low dosages a f f e c t the func t ions of vege ta t ion mentioned, can, a t b e s t , be deduced t o an o rder of magnitude (Materna, 1980) from the known r e a l e f f e c t s on vege ta t ion .

Causes f o r the Observed Responses of P l a n t Communities

The e f f e c t s of a given p o l l u t a n t on p l a n t communities, a s i l l u s t r a t e d by s e v e r a l exam-p l e s , a r e determined by: the g e n e t i c a l l y predetermined degree of r e s i s t a n c e of t h e companion s p e c i e s (Dochinger e t al . , 1965; Rohmeder e t a l . , 1965), the modifying in f luence of en-vironmental cond i t ions of r e s i s t a n c e , and t h e changes i n i n t r a - and i n t e r s p e c i f i c r e l a t i o n s caused by p o l l u t a n t s .

Populat ions of c e r t a i n p l a n t spec ies , va-r i e t i e s , and c lones , a s we l l a s ind iv idua l s w i t h i n the r e s p e c t i v e populations s tud ied , r e a c t t o a given a i r p o l l u t i o n s t r e s s wi th varying degrees of s e n s i t i v i t y . I n c o n t r a s t t o c e r t a i n phytopathogenic organisms (Baumann, 1951; Grossmann~ 1970), t h e r e i s no abso lu te r e s i s t a n c e , a s demonstrated by t h e ex i s tence of v e g e t a t i o n - f r e e zones. The schematic diagram (Figure 1 ) i s an a t tempt t o demonstrate which f a c t o r s in f luence the response t o a i r p o l l u t i o n s t r e s s .

Ind iv idua l and Species S p e c i f i c Responses

According t o L e v i t t (1972), two mechanisms determine a p l a n t ' s r e s i s t a n c e t o s t r e s s : s t r e s s avoidance and s t r e s s to le rance . I n the f i r s t c a s e t h e s t r e s s , caused here by a s p e c i f i c p o l l u t a n t dose, i s prevented from taking e f f e c t - - i t i s excluded. A mul t i tude of f a c t o r s determines the r e s i s t a n c e of a p l a n t organism t o t h e e n t r y of p o l l u t a n t s i n t o the c e l l . Morphological p r o p e r t i e s such a s

shape and sur face s t r u c t u r e including wax l a y e r s (Rentschler , 1973; Shr ine r , 1980) a s we l l a s the number, d i s t r i b u t i o n , and a p e r t u r e of the stoma (Meidner and Mansfield, 1968) must be mentioned. According t o Taylor (1978), whose d e f i n i t i o n was taken i n t o cons ide ra t ion i n the corresponding s e c t i o n of Figure 1, s t r e s s to le rance presupposes the e n t r y of the r e s p e c t i v e p o l l u t a n t i n t o the c e l l . As long a s the en te r ing substance i s t o l e r a t e d , a s -s imi la ted o r buf fe red , and consequently no morphological o r phys io log ica l change t akes p lace , one speaks of " s t r a i n avoidance." Above c e r t a i n i n t r a c e l l u l a r concen t ra t ions , f o r example, a f t e r c e r t a i n biochemical threshold va lues have been exceeded, i n j u r y occurs which i s e i t h e r r e v e r s i b l e ( e l a s t i c s t r a i n ) , such a s s u b t l e changes i n photosynthet ic performance ( S i j and Swanson, l974) , o r i r r e v e r s i b l e (p las - t i c s t r a i n ) , such a s i n j u r y t o leaves i n t h e form of nec ros i s .

Thus, t h e biochemical threshold va lues , which c h a r a c t e r i z e t h e t r a n s i t i o n s from s t r a i n avoidance t o s t r a i n to le rance a s we l l a s from e l a s t i c s t r a i n t o p l a s t i c s t r a i n , determine the to le rance of a p l a n t . It follows t h a t the ind iv idua l response can manifes t i t s e l f i n terms of ind i f fe rence , modif icat ion o r dea th of the a f f e c t e d p l a n t depending on the l e v e l of ambient s t r e s s , and t h e r e s p e c t i v e r e s i s t a n c e .

As i s apparent from F igure 1, a mul t i tude of organismal and environmental f a c t o r s be fore , dur ing, and a f t e r the p o l l u t a n t impact i s r e -sponsible f o r the sometimes ve ry g r e a t d i f - f e rences i n t h e " res i s t ance s e r i e s " o r "re-s i s t a n c e groups" of va r ious au thors (Stoklasa , 1923; Bredemann, 1956; Thomas, 1961; Garber, 1967; Mooi, 1974; Davis and Wilhour, 1976; Guderian, 1977). A l l c l i m a t i c f a c t o r s , f o r example, t h a t r e g u l a t e t h e number, s i z e and a p e r t u r e of the stomata (Bronte and Conguet, 1975; Ha l l and Kaufmann, 1975), such a s l i g h t , optimal water supply, h igh r e l a t i v e humidity o r adequate temperature, determine the r a t e a t which p o l l u t a n t s a r e absorbed (Guderian, 1970; Jones and Mansfeld, 1970; McLean and Schneider, 1971).

The in f luence of edaphic f a c t o r s is demon-s t r a t e d with two examples: Copper-beech (Fagus s i l v a t i c a ) i s considerably more r e s i s t a n t on s o i l s wi th high lime con ten t than on sandy s o i l low i n n u t r i e n t s ; elm (Ulmus campestr is ) proved t o be one of the most r e s i s t a n t spec ies i n a l l u v i a l f o r e s t s , bu t i n l e s s s u i t a b l e h a b i t a t s i t was one of the most vu lnerab le of a l l the deciduous spec ies (Wentzel, 1968). This shows t h e d i f f i c u l t y i n s e t t i n g up gener- a l l y accepted r e s i s t a n c e s e r i e s , a s r e c e n t s t u d i e s wi th va r ious soybean c u l t i v a r s under changing environmental cond i t ions have c l e a r l y shown (Heagle, 1979a, b ) .

The l a rch serves a s a t y p i c a l example f o r changes i n r e s i s t a n c e i n r e l a t i o n t o l e v e l s of concen t ra t ion (Guderian and Stratmann, 1962; Wentzel, 1963). Under high, acu te SO2 con- c e n t r a t i o n s , both Lar ix europea and Lar ix l e p t o l e p i s show s i g n s of n e c r o s i s before spruce

momentary dosage momentary..-low intermediate high I-air oollution stress

momentary momentary

succession interspecific

relationshipareal and areal and abundance. alteration alteration

low dosage response intermediate dosage response high dosage response no significant first alterations in extensive simplification

alteration of structure and compositions up to total destruction

plant communities of plant communities of plant communities

Figure 1: Effect-determining-factors'for various responses of plants on individual-,

species- and community-levels.

(Picea ab ies ) and p ine (Pinus s i l v e s t r i s ) . On the o t h e r hand, t h e l a r c h i s among the most r e s i s t a n t c o n i f e r s under continuous low l e v e l s of concen t ra t ion (Wentzel, 1963), and i t i s widely used t o r e e s t a b l i s h t r e e populat ions a f t e r t h e degradat ion of spruce and p ine f o r - e s t s i n reg ions of chronic s t r e s s .

Regarding organismal f a c t o r s , t h e s i g n i f i - cance of age f o r s e n s i t i v i t y should be s t r e s s e d . According t o observat ion i n t h e f i e l d , c o n i f e r s such a s Picea a b i e s and Pinus s i l v e s t r i s r e - main p a r t i c u l a r l y s u s c e p t i b l e from the l a t e po le t imber s t a g e ( a t t h e time of accumulating growth) through t o t h e t r e e timber s t age . Dur-i n g these per iods of development, e s p e c i a l l y s t rong reduc t ions i n growth and t h e widespread degradat ion of e n t i r e s t ands occur (Wentzel, 1962; Materna e t a l . , 1969), whi le deciduous populat ions respond i n a much weaker form. I n p l a n t i n g s , however, under mostly chronic SO2 concen t ra t ions , t h e c o n i f e r s mentioned and the copper-beech (Fagus s i l v a t i c a ) and pedunculate oak (Quercus pedunculata) exh ib i t ed near ly equal r e s i s t a n c e (Guderian and Stratmann, 1968).

One aspec t no t o f t e n taken i n t o account when judging the r e s i s t a n c e of p l a n t s , bes ides en-vironmental, p o l l u t a n t , and organic in f luences , i s t h e c r i t e r i a used t o i n t e r p r e t t h e e f f e c t . Various deciduous t r e e spec ies , such a s l inden ( T i l i a corda ta an& T i l i a p l a t y p h l l o s ) and beech (Fagus s i l v a t i c a ) respond t o a c u t e SO2 con- c e n t r a t i o n s wi th l e a f n e c r o s i s e a r l i e r than spruce (Picea ab ies ) o r Sco t s p ine (Pinus sil-v e s t r i s ) . Never theless t h e deciduous spec ies can s t i l l grow i n p o l l u t e d reg ions where spruce and Sco t s p ine d i e out (Wentzel, 1968). Thus r e s i s t a n c e must f i r s t of a l l be charac te r i zed by t h e d i f f e r e n c e s i n t h e reduc t ion of growth and y i e l d of the s p e c i f i c spec ies . The func- t i o n s of t h e p l a n t spec ies being considered he re determine t h e c r i t e r i a used t o eva lua te the e f f e c t s (Guderian, 1977). Through t h e s h o r t d e s c r i p t i o n of f a c t o r s determining the r e s i s t a n c e of an ind iv idua l o r a spec ies i t can be seen what degrees of v a r i a t i o n must be expected i n t h e responses. The use of these r e s u l t s t o f o r e c a s t t h e behavior of s i n g l e spec ies under a i r p o l l u t i o n s t r e s s i s necessar- i l y ve ry d i f f i c u l t , e s p e c i a l l y when s tudying p l a n t communities.

I n the following model, supported by experimental r e s u l t s , an a t tempt is made t o i l l u s - t r a t e t h e p o s s i b l e responses of two p l a n t spec ies t o inc reas ing a i r p o l l u t i o n s t r e s s (Fig. 2 ) . A s p e c i f i c response of two p l a n t spec ies (A and B) i s shown i n pe rcen t of con-t r o l . Up t o a s p e c i f i c concen t ra t ion labeled A 1 and B3 no s i g n i f i c a n t dev ia t ion i n t h e re - sponses of t h e exposed p l a n t s and t h e c o n t r o l p l a n t s could be de tec ted . Important q u a l i t a - t i v e d i f f e r e n c e s i n response between t h e two spec ies e x i s t above concen t ra t ion A1 . With Species A, t h e s p e c i f i c response i s i n i t i a l l y s t imulated by sulphur dioxide; a reduct ion of performance only occurs a t a h igher concentra-t i o n , whi le t h i s Species B lacks s t imula t ing e f f e c t . The f u r t h e r s lope of t h e curve shows

the degree of reduct ion i n response. The concentra t ion A 4 / ~ 4 should be emphasized, a s he re the r e s i s t a n c e r e l a t i o n s h i p of the two spec ies changes (Wentzel, 1963). I n t h e con- c e n t r a t i o n range A1 t o A 4 / ~ 4 spec ies A would have an advantage over spec ies B, even under p o l l u t a n t concen t ra t ions which do not y e t have an adverse e f f e c t on spec ies B. Accord-i n g l y , changes i n t h e composition of p l a n t communities must be expected even i f SO2 con- c e n t r a t i o n s a r e so low t h a t they do not y e t have a d i r e c t harmful e f f e c t . This i s a s i g n i f i c a n t a spec t f o r eco log ica l research.

Community Spec i f i c Responses

The previously demonstrated r e l a t i o n s h i p s between h e r e d i t y , environment and r e s i s t a n c e i n ind iv idua l s o r homotypical populat ions a r e n a t u r a l l y a l s o v a l i d f o r p l a n t communities. Community s p e c i f i c a spec t s must be given ad- d i t i o n a l cons ide ra t ion when a s c e r t a i n i n g pol- l u t a n t e f f e c t s . The importance of the r e -l a t i o n s h i p between two o r more populat ions shown i n Fig . 1 i s underlined by t h e few ex- i s t i n g r e s u l t s from experiments on t h e i n f l u - ence of a i r p o l l u t a n t s t o p l a n t communities. Thus, according t o experimental a n a l y s i s of pure and mixed seedings, c o n s i s t i n g of r y e g r a s s (Lolium multiflorum) h a i r y vetch (Vicia v i l l o g a ) and crimson c lover (Tr i fol ium incar - natum) s h i f t s i n the composition of p l a n t com-muni t ies cannot be explained exc lus ive ly through t h e d i r e c t e f f e c t of p o l l u t a n t s on va r ious spec ies of d i f f e r e n t s e n s i t i v i t y (Guderian, 1966, 1977). Under SO2 the inf luence of i n t e r -s p e c i f i c competit ion was a l t e r e d . As a r e s u l t , t h e primary e f f e c t on the more suscep t ib le mem-b e r s was magnified t o such a degree t h a t they could no longer compete e f f e c t i v e l y f o r v i t a l growth-determining f a c t o r s . As a r e s u l t of changed competit ion i n the community, t h e d e c l i n e of t h e more s e n s i t i v e members allowed improved growth of t h e more r e s i s t a n t spec ies . The t o t a l community y i e l d decreased l e s s than would have been expected from the l o s s of t h e more suscep t ib le spec ies . Similar r e s u l t s were found under the in f luence of ozone (Bennett and Runeckles, 1977), u l t r a v i o l e t r a d i a t i o n (Fox and Caldwell , 1978) and ion iz ing r a d i a t i o n (McCormick, 1963). The l a s t of these s t u d i e s shows the importance of s t r e s s dur ing t h e seed- l i n g and sprout s t ages .

The ex ten t of s h i f t s i n p l a n t communities a s a r e a c t i o n t o a given load i s a l s o dependent t o a l a r g e degree on the cond i t ion of the com-munity i t s e l f . The importance of t h e bu i ld ing of s t r a t a , of morphological s t r u c t u r e s , a s w e l l a s r e l i e f and uniformity of the vege ta t ion cover were a l ready pointed out a s was the in tercon- nect ion between s tages of succession and system responses. The s t a b i l i t y of a community g rea t - l y inf luences the response of i t s ind iv idua l members a s we l l a s the whole t o a given po l lu - t a n t load. I n the presence of small d i s tu rbances , h igh ly productive, complex systems can usua l ly

Special responses of plant species A and B control = 100%

Typical reactions of two plant species depending on t h e su l fur dioxide content of a i r

rega in t h e i r s t a t e of balance quickly because of t h e i r complex feedback systems. Under heav ie r loads on the o t h e r hand, d r a s t i c changes must be expet ted p a r t i c u l a r l y i f c e r t a i n key spec ies a r e ve ry s e n s i t i v e t o the r e - spec t ive a i r p o l l u t a n t . But even very low p o l l u t a n t concen t ra t ions can produce q u i t e cons ide rab le e f f e c t s i n p l a n t communities, e s p e c i a l l y i f synecological amplitudes of the n a t u r a l community spec ies a r e f a r a p a r t . Ad-d i t i o n a l s t r e s s through p o l l u t a n t s of lower dosage can lead t o d r a s t i c reduct ion i n v i - t a l i t y of p l a n t s a l ready l i v i n g o u t s i d e t h e i r eco log ic optimum. The r e l a t i v e l y high sus-c e p t i b i l i t y of spruce (Picea a b i e s ) i n the Erz mountains (Materna, 1972) and i n the b o r e a l con i fe rous f o r e s t s i n Finland (Huttunen, 1979) might w e l l be caused by t h e i r unsu i t ab le hab- i t a t s . Keeping t h i s i n mind, i t seems prob- lemat ic t o t r a n s f e r those dose -e f fec t r e -l a t i o n s h i p s determined from "production eco-systems1'--in which t h e food p l a n t s genera l ly encounter f avorab le cond i t ions - - to n a t u r a l ecosystems.

The r e l a t i o n s h i p s enumerated up t o t h i s p o i n t show c l e a r l y why emissions induce degradat ion i n p l a n t communities. On t h e o t h e r hand spontaneous adap ta t ion t o a i r p o l l u t i o n s t r e s s may be observed--adaptation which does no t ensure t h e s u r v i v a l of t h e s p e c i e s through s t u n t i n g , b u t r a t h e r seems t o have gene t i c o r i g i n s . When Marchantia polymorpha (Briggs , 1972) was exposed t o l ead , and var ious g r a s s spec ies (Bradshaw, 1971, 1972, 1976) were a f -f e c t e d by copper and z i n c , more t o l e r a n t pop- u l a t i o n s developed i n a s h o r t time through d i r e c t e d s e l e c t i o n . B e l l and Clough (1973), B e l l and Mudd (1976), and Horsman and Wellburn (1977) mention s i m i l a r processes wi th Lolium perenne and Rumex o b t u s i f o l i u s subjected t o decades of SO2 loading. F i n a l l y , t h e r e s u l t s of long-term fumigation of n a t i v e g rass land (Pres ton and B u l l e t t , 1978) a l s o p o i n t t o the f a c t t h a t under anything l e s s than acu te con- c e n t r a t i o n s spontaneous adap ta t ion may occur i n t h e course of t h e formation of a new sec-ondary equ i l ib r ium, which may a l s o i n t e r r u p t p o s s i b l e long-term i n j u r y (Pres ton, l979a).

Accordingly, t h e dose and i t s r a t e of change should be ad jus ted over the long-term such t h a t p l a n t communities r e t a i n t h e i r c a p a b i l i t y - - even by t h e evo lu t ionary method mentioned a-bove--to f u l f i l l t h e i r func t ion i n n a t u r a l and a g r a r i a n ecosystems t o t h e f u l l e s t (Guderian and Kueppers, 1979).

The g e n e t i c a l l y f ixed v a r i a t i o n i n popu- l a t i o n s which i s expressed i n the descr ibed spontaneous adap ta t ion , provides the b a s i s f o r breeding of p o l l u t a n t r e s i s t a n t p l a n t s through s e l e c t i o n and reproduct ion of r e l a - t i v e l y r e s i s t a n t i n d i v i d u a l s (Bialobok, 1979).

The responses of i n d i v i d u a l s and homotypic popu la t ions t ak ing i n t o account i n t e r s p e c i f i c r e l a t i o n s d i scussed i n t h i s s e c t i o n , lead t o t h e community s p e c i f i c responses shown i n Fig . 1 which range from i n s i g n i f i c a n t changes t o the t o t a l d e s t r u c t i o n of p l a n t communities.

CONCLUSIONS

Contamination of ex tens ive a r e a s due t o inc reas ing emissions and c o n t r o l s t r a t e g i e s us ing t a l l s t acks f o r d i l u t i o n has made the s tudy of p l a n t communities and ecosystems e s p e c i a l l y necessary. To a i d i n recogn i t ion of p o s s i b l e r i s k s and i n making dec i s ions r e -garding c o n t r o l measures a t the source and i n the a f f e c t e d a r e a , t h e fol lowing p o i n t s must be c l a r i f i e d :

1. Under which doses do changes occur i n s t r u c t u r e and func t ion of p l a n t communities of d i f f e r e n t complexity?

2. To what e x t e n t do p l a n t communities show more s e n s i t i v e responses than the in - d i v i d u a l spec ies composing them?

3. What a r e the mechanisms of these changes? - P o i n t s of impact f o r a i r p o l l u t a n t s

i n the ecosystem. - Location of p o l l u t a n t s i n the eco-

system (ass imi la t ion , accumulation, break down).

- Direc t s t imula to ry o r i n j u r i o u s e f f e c t s on t h e ind iv idua l spec ies of t h e community.

- Causes and mechanisms of changes i n competit ion equi l ibr ium.

- Secondary succession with p a r t i c u l a r a t t e n t i o n t o adap ta t ion and compen- s a t i o n .

4. How a r e r i s k s determined f o r p l a n t communities?

- Development of experimental des igns and i n t e n s i f i c a t i o n s of epidemio-l o g i c a l s t u d i e s f o r t h e determinat ion of e f f e c t s t o h igh ly s t r u c t u r e d systems.

- Establishment of permanent s tudy a r e a s t o i n v e s t i g a t e succession.

- Use of model p l a n t communities a s i n d i c a t o r s i n eco- toxicological t e s t s . - Analysis of the cond i t ion of ecosys-tems before and a f t e r s t a r t - u p of a p o l l u t a n t source.

5. What measures a r e necessary f o r the p r o t e c t i o n of vege ta t ion?

- Determination of dose-response r e -l a t i o n s f o r p l a n t communities a s a b a s i s f o r r i s k p r e d i c t i o n s and the es tabl ishment of s tandards f o r eco-systems.

- Col lec t ion of gene t i c resources i n n a t u r a l r e se rves and i n gene banks.

- P r o t e c t i o n of endangered p l a n t com-muni t i e s , e s p e c i a l l y i n e x i s t i n g n a t u r a l r e se rves , from e f f e c t s of' a i r p o l l u t a n t s .

- Development and maintenance of a i r p o l l u t a n t c o n t r o l s t r a t e g i e s allowing p o l l u t a n t dose and i t s r a t e of change be so c o n t r o l l e d t h a t the s t r u c t u r a l d i v e r s i t y , and the eco-l o g i c and economic func t ions of the vege ta t ion , a s w e l l a s i t s funct ion a s a gene pool, a r e f u l l y p ro tec ted .

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ACKNOWLEDGMENT

Appreciation i s expressed t o Walter Jansen f o r t r a n s l a t i n g t h i s manuscript from t h e o r i g i n a l German.

Forecasting Effects of SO2 Pollution on Growth and Succession in a Western

Conifer Forest 2J.R. Kercher, M.C. Axelrod, and G.E. Bingham

Abstract: A simulator has been developed for the mixed conifer forest type of the Sierra Nevada, California to forecast the effects of SO2 on forest growth and succession. The model simulates recruitment, growth, and death of each tree and is based on a northeastern USA simulator with extensive modifications. These modifications include the introduction of fire ecology, temporal seed crop patterns unique to the Sierra, and water stress. Pollutant stress is modeled as an effect on tree growth. The model simulates the shift from the ponderosa pine dominated forest type to the white fir dominated mixed conifer type as elevation increases from 5000 to 6000 ft. It also simulates the fire-suppression of white fir and the fire-climax of ponderosa pine. For a 10% growth reduction of ponderosa pine from pollutant stress and with growth reductions in other species as determined by their relative sensitivities, standing crops of ponderosa pine were reduced and white fir increased.

It is anticipated that extensive fossil fuel energy development will occur in the United States over the next several decades with increased emissions of phytoactive effluents. It has long been recognized that many of these pollutants have deleterious effects on the growth and behavior of vegetative communities. The effects of SO2 in particular have been extensively studied and occur at all levels of resolution from the metabolic process level to the ecosystem level. In the work reported on here, we wanted to predict the effects at the population and community levels given the results of the effects at the whole plant level. We have developed other models to forecast effects at the process level (Kercher 1977; Kercher 1978). The model, SILVA, uses an empirical dose-response relationship for the effects of pollutants at the tree-level. By virtue of the ecological interactions contained in the model, the effects at the tree level are translated into effects at the community level.

We have followed the modeling approach developed by Botkin and others (1972) who developed


~nvironmental Scientist; Electrical Engineer; and Environmental Scientist, Lawrence Livermore Natl. Laboratory (LLNL), Livermore, Calif. operated by the University of California for the Dept. of Energy under contract number W-7405.

JABOWA, a simulator of forests of the northeastern USA. For a case study, SILVA has been applied to the ponderosa pine and mixed conifer forest types of the Sierra Nevada, California, USA. The associated species in these forests are ponderosa pine (Pinus ponderosa), white fir (Abies concolor), Douglas-fir (Pseudotsuga menziesii), sugar pine (Pinus lambertiana), incense-cedar (Libocedrus or Calocedrus decurrens), California black oak (Quercus kelloggii), and Jeffrey pine (Pinus Jeffrey!).

MODEL DESCRIPTION

SILVA calculates environmental parameters of the stand and initializes number and sizes of the trees from environmental and control data respectively. A table of good and bad seed crop years and a list of fire years is generated. The effect of pollution on trees is calculated. The number of new seedlings for that year, the growth of each tree,, and mortality are then determined for each year. Growth is modeled as a difference equation in the tree dbh and as a function of environmental variables. The killing is done sto- chastically depending on the probability of death as determined by ecological risk, lack of growth, and fire damage. The dynamics of fuel accumulation (litter and brush) are also modeled.

Temporal Seed Crop Patterns--For the conifers of the Sierra Nevada, there can be significant temporal variations in the annual cone production. We modeled the phenomenon of high and low yield seed years as .a Bernoulli random process with blocking. If the species is in an unblocked state, the probability of a good crop is p and of a poor crop is (1-p). If a good seed crop occurs, the

the process is assumed to be blocked for r-1 years. The parameters p and r were taken from cone crop data.

Fire Ecology--Fire is a critical factor in the population dynamics of western forests. The most important aspect of fire is fire-induced mortality. The occurrence of fire was also modeled as a Bernoulli random process with blocking and p and r are based on fire incidence data. The blocking in this case arises from the time required for fuel to build back up to levels capable of supporting fire propagation. Fire kills by raising the temperature inside the tree and by damaging the crown. Fire intensity is calculated in kilo- watts/meter of fireline length using FIREMOD (Albini 1976) and probability of death is determined as a function of dbh, bark thickness, and scorch height. Scorch height is calculated from fire intensity, ambient temperature, and windspeed.

Moisture Stress--The effects of moisture stress are modeled by multiplying the difference equation for growth by a moisture stress factor. Parame-ters for this function are taken from published ranges of tolerance data. The moisture stress factor is a function of the ratio of actual evapotranspiration to potential evapotranspiration.

MODELING SO2-POLLUTANT EFFECTS

It has long been held that chronic injury results from sulfate accumulation in plant tissues. Guderian (1977) has suggested that in most cases involving a single point source, chronic injury results from the "short-term action of relatively high concentration peaks". Thus the long-term average air concentration can be quite low due to the large number of pollution-free time periods. Because two different perspectives exist, i.e., (1) measuring average annual concentration or accumulated dose or (2) regarding injury as aris- ing from episodes and making detailed measurements of episode parameters, we have two different pollutant-ef fects submodels.

Seasonal Average Submodel--This approach assumes that growth reduction is a simple function of the SO2 concentration averaged over the growing season, or equivalently, of the integral of SO2 concentration over time. We use a dose-response function in which growth decreases linearly with increasing accumulated dose based on the preliminary study of the tree-ring data of Lathe and McCallum (1939) for ponderosa pine grown near the smelter at Trail, B.C.

Successive Episode Model--An alternative approach is to calculate the accumulated damage caused by successive short episodes separated by time intervals with no or negligible pollution. One method to implement this approach would be to use a process model (Kercher 1978). The method used here is an empirical dose-response where the dose is that accumulated from successive episodes (Kercher and Axelrod 1980). We use the empirical dose-response of Larson and Heck (1976) which mo-

dels the probit of the effect being proportional to the log of the generalized dose.

SIMULATION RESULTS

Fire Ecology--Figure 1 shows the response of ponderosa pine and white fir with fire occurring at the natural frequency and with complete fire suppression. Ponderosa pine is well adapted to fire and dominates where undergrowth is thinned by fire. The model reproduces this result and indicates white fir would eventually outcompete ponderosa pine in the absence of fire. The model suggests that a significant factor in the fire adaptation of ponderosa pine is its growth rate and growth form which allow it to evade fire by minimizing the time that the crown is exposed to fire. The effects of fire on tree mortality is shown in figure 2a. Note the shift in age of death to the lower ages in the presence of fire.

Pollution Simulations--As an example of effects of pollution, consider the minimally significant case of 10% growth reduction in ponderosa pine. We scaled the response of the remaining species according to their published relative sensitivities. These calculations used the seasonal aver-age model. The results for ponderosa pine and- white fir (fig. 3) indicate that while white fir undergoes a nominal growth reduction of about 1 to 2% per tree with pollution, total basal area actually shows a dramatic increase. This is due to the much greater growth retardation that the dominant species experiences. Tree mortality of ponderosa pine (fig. 2b) indicates the trees are at higher risk at higher ages under pollution. The older, slower growing, pollution-stressed trees have size-dependent risks comparable to those of the younger unstressed trees. We can summarize (fig. 4) the results for ponderosa pine,

4 0 , 1 , 1 , I ' -35

30 -25 -

Without fire -I- 10 - 1 -

.cE 5

-S o L ~ l l l l t l ~

14 Without fire

12

10

4 With fire

2

0 100 200 300 400 500 Time from clearcut (yr)

Figure I--Average of basal area from 25 simulations showing effects of fire. (a) Ponderosa pine (b) White fir.

,,,--

0.080

0.070 Ponderom Pine Ponderom Pine NO SO,

0.060 With SO,EÃ‘Ã‘

0-

Figure 2--Fraction of trees which died in simulations of figure 1 plotted against age at death. (a) With and without fire. (b) With and without pollution.

l ' l r l T l ' - White Fir

-

1 , l ~ I ~ l ~ 0 100 200 300 400 500

Time from clearcut lyr)

Figure 3--Basal area growth with and without pollution for (a) pine and (b) fir.

white fir, and Douglas-fir by using boxplots of the distributions of the 500 annual data points of each species fraction of the total basal area. Note the decrease in pine and the increase in fir with pollution. The basal area of Douglas-fir is extremely reduced. The environmental conditions were poor for Douglas-fir even in the absence of SO?. The competitive disadvantage for Douglas-fir is made worse by pollution because Douglas-fir is sensitive to SO-> and carries its needles longer than ponderosa pine. Thus the growth reduction for an individual tree (greater than that for ponderosa pine) translates into a much larger effect on basal area.

LITERATURE CITED

Albini, F.A. 1976. Computer-based models of wildland fire behavior: a user's manual. 68 p. USDA For. Serv., Intermt. For. and Range Stn., Ogden, Utah.

Ponderosa Pine White Fir Douglas Fir

Figure 4--Boxplots of polluted and unpolluted cases. Median is line at notches. Top of box is 75th percentile; bottom of box is 25th. Range is vertical line. Non-overlapping notches indicate significance at 95% level.

Botkin, D.B., J.F. Janak, and J.R. Wallis. 1972. Some ecological consequences of a computer model of forest growth. J. Ecol. 60: 849-872.

Guderian R. 1977. Air pollution. 127 p. Springer-Verlag, New York.

Kercher, J.R. 1977. GROW1: A crop growth model for assessing impacts of gaseous pollutants from geothermal technologies. UCRL-52247, 33 p. Lawrence Livermore Natl. Laboratory, Livennore, Calif.

Kercher, J.R. ,

1978. A model of leaf photosynthesis and the effects of simple gaseous sulfur compounds (H2S and SO2). UCRL-52643, 37 p. Lawrence Livennore Natl. Laboratory, Livermore, Calif.

Kercher, J.R. and M.C. Axelrod. 1980a. A model for forecasting the effects of SO2 pollution on succession in a western coniferous forest: Interim Report. UCID-18537. 58 p. Lawrence Livennore Natl. Labora- tory, Livermore, Calif.

Kercher, J.R. and M.C. Axelrod. 1980b. SILVA: a model for forecasting the effects of SO2 pollution on growth and succession in a western coniferous forest: Final report. UCID (to be published). Law-rence Livermore Natl. Laboratory, Livennore, Calif.

Larson, R.I. and W.W. Heck. 1976. An air quality data analysis system for interrelating effects, standards, and needed source reductions: Part 3. Vegetation injury. J. Air Poll. Control Assoc. 26:325-333.

Lathe, F.E. and A.W. McCallum 1939. The effect of sulphur dioxide on the diameter increment of conifers. 3 Effect of sulphur dioxide on vegetation. National Re- search Council of Canada. p. 174-206. N.R.C. No. 815. Ottawa, Canada.

Forest Models: Their Development and Potential Applications for Air Pollution

Effects Research1

H. H. Shugart, S. B. McLaughlin, and D. C. west2

Abstract: As research tools for evaluating the effects of chronic a i r pollution stress, forest simulation models offer one means of i ntegrati ng forest growth and develop-ment data with generalized indices of pollution stress. This approach permits consideration of both the competitive interactions of trees in the forest stand and the influ-ences of the stage of stand development on sensit ivity of component species. A review of forest growth models, including tree, stand, and gap models, i s provided as a means of evaluating re1 ati ve strengths, weaknesses, and 1 imi t s of appl i cabi 1 i ty of representati ve examples of each type. Data from recent simulations with a gap model of eastern deciduous forest responses to a i r pol 1 uti on stress are presented to emphasize the potential importance of competition in modifying individual species' responses in a forest stand. Recent developments in dendroecology are discussed as a potential mechanism for model validation and extended appl i cati on.

Atmospheric emissions from widespread indus- the future i s a challenge made comsiderably more t r i a l and urban sources have now significantly dif f icul t by the complex nature of forest eco-a1 tered the a i r qua1 i ty of extensive forested systems. The perennial growth habit of forest regions of the world. Wolak (1971) described trees and the nature of their competitive inter-the influence of industrial emissions on actions in a forest community make diff icul t the forested areas of Poland as an abiotic para- evaluation of chronic exposures of forests t o natural ecological factor. He viewed the atmospheric pol 1 utants. Treshow (1970) pointed results of these emissions on forest succession out that terres t r i a1 ecosystems are del i cately as the establishment of a new final sera1 stage balanced with a structure that may depend on a termed the industrio-climax. Assessing the few cr i t ical species. He indicated the response impacts of these changes and those which may of vegetation may be slow, b u t once natural ensue as we rely increasingly on fossil fuels in balances are sufficiently disrupted, subsequent.

alterations may occur much more rapidly because of irreversible a1 terat i ons of essenti a1 system

'presented a t the Symposium on Effects of Air functions or species interactions. Pollutants on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, Califor- Traditionally, studies of responses of forest nia, U.S.A. trees to a i r pollution stress have focused pri-

marily on species level responses, seedlings, a Z~esearch Staff Members of the few selected physiological processes, and gen-

Environmental Sciences Division, Oak Ridge eral ly simp1 i s t i c exposure regimes. While valu- National Laboratory, Oak Ridge. Research able informati on has been gained on specific supported by the National Science Foundation's pl ant-pol lutant interactions, we s t i 11 know very Ecosystem Stud i es Program under Interagency 1i t t l e about the potenti a1 effects of pollutants Agreement No. DEB77-25781 with the U.S. on forest communities. For instance, how are Department of Energy under contract W-7405-eng-26 individual species effects integrated over space with Union Carbide Corporation. Publication No. and time into responses of the forest community? 1545, Environmental Sciences Division, ORNL. What are the probable limits of impacts on

forests based on our current knowledge of sensi t iv i ty of individual species responses?

To address these questions necessitates that we combi ne both autecologi cal and synecologicalapproaches. The former we can derive in large part from dose-response data for individual species. In the l a t t e r task, we can derive from the experiences of two decades of experimenta-tion with mathematical simulation of the growth and development of forest communi t i es (Rei chl e and others 1973, Munro 1974, Shugart and West 1980). The purpose of th i s paper i s to review the basic components of these models with a view toward understanding their strengths and weak-nesses and their potential u t i l i t y as tools for studying comnunity-1 eve1 responses to a i r pol 1u- tion stress.

Computer Models of Forest Dynamics

In the mid-19601s, foresters and ecologists independently began to develop extremely detailed computer models of forest growth and development. Foresters realized that certain changes in fores t practice (e.g., change in trees due to genetic improvement, use of fer-t i l i z e r in fores ts) would render less useful the stand yield tables that had been laboriously developed over the prior several decades. Some foresters began to develop models of forest growth and yield that could be calibrated on the extant, stand-table data se ts and could also be used to incorporate some of the changes in forestry practice ( f ig . 1). A t the same time, ecologists became dissatisfied with the s t a t i c notion of forest typology and developed inten-s i ve investigations (e.g., the International Biological Program) of the dynamic aspects of ecosystems. This increased interest in eco-system dynamics led naturally to the development of fores t models. By the mid-1970's (f ig. I ) , three approaches evolved to modeling the long-term dynamics of fores ts ( table 1). We will discuss the u t i l i t y of each of these approaches in terms of i t s applicability to assessing the consequences of a i r pollution effects over long time scales. The approaches are:

(1) Forest models consider the forest as the focal point of the simulation model. For-es t ry yield tables constitute a highly data-dependent subset of these fores t model s.

( 2 ) Tree models take the individual t ree as the basic unit of a fores t simulator. The degree of complexity ranges from simp1 e tabu1 ati on of the probabi 1 i t i es of an individual t ree of one kind being replaced by an individual of another kind to extremely detailed models that include 3-dimensional geometry of different species at different sizes.

( 3 ) Gap models dynamically simulate particu- l a r at tr ibutes of each individual tree on a prescribed spatial unit of relatively small

ORNL DWG 80 H U B ESD

COMMUNITYM I D 1960's TABLES CLASSIFICATION1 1

FORESTERS RECOGNIZE ECOLOGISTS BECAME THE POSSIBILITY OF CHANGE INCREASINGLY AWARE OF ECOSYSTEM LATE 1960's IN TREE GENETICS AND FORESTRY FOREST DYNAMICS AND OF

PRACTICE USE OF COMPUTERS

MID- 1970's MODELS MODELS MODELS

WORK "I

PROPOSED * * 4 PUBLISHED4 2

LATE 1970 '1 APPLICATION OF DEVELOPED MODELS TO NEW PROBLEMS INCLUDING POLLUTION EFFECTS

Figure I--Recent historical origins of computer models used for pollution effects assessment a t the forest ecosystem level.

size. The spatial unit i s usually either a gap in the forest canopy or a sample quadrat.

In general, the model type used i s based on the problem considered, the data available, and the desire to develop a flexible model. The t ree and forest model categories correspond to the t ree and stand model categories used in a recent review of forestry models (Munro 1974). In the present review, gap models (which might be considered a special case of three models) are recognized as a category developed exclu-sively for use in studying ecological succession.

Forest Models

Yield tables used in forestry management are, in fac t , empirical models of expected responses of an even-aged forest of (usually) a single species. In th i s context, a forest i s taken as a larger spatial dimension than either single t ree or gap models considered explicitly.

Comparable succession models have been developed using a variety of mathematical approaches. Most of these models consider the landscape to be composed of a number of mosaic elements that chanae in response to success.iona1 processes. These changes may be viewed as proba--a---l i s t i t5 (e.g., Wilkins 1977, Hool 1966) or continuous (Shugart and others 1973), depending on modeling assumptions relating to the actual size of the landscape considered. Forest models tend to be data-dependent concerning changing rates of the mosaic elements assumed to comprise the forests, and the actual mechanisms that cause the changes in the forests do not appear explicit ly in the models. All of the forest models l isted (table 1) require l i t t l e computer time and can be solved analytically in many

Table 1. C l a s s i f i c a t i o n and c h a r a c t e r i z a t i o n o f f o r e s t s imu la t ion models as t o o l s f o r eva lua t ing s t r e s s e f f e c t s .

Model 1 1 Assessment p o t e n t i a1 Age-st ructure Space Examples

categor

Fores t Even ( u s u a l l y ) Nonspat ia l Most y i e l d t a b l e s i n use i n f o r e s t r y today

Mixed Nonspati a1 ~ 0 0 1 1966 Olson and C h r i s t o f o l i n i 1966 Moser and H a l l 1969 Shugart and o thers 1973 Johnson and Sharpe 1976 W i 1 k i n s 1977

Newnham 1964 Lee 1967 M i t c h e l l 1969 L i n 1970 B e l l a 1971

Tree Even Hatch 1971 Hegyi 1974 L i n 1974

Nonspati a1 C l u t t e r 1963 C u r t i s 1967 Dress 1970 Goulding 1972 S u l l i v a n and C l u t t e r 1972 Burkhar t and Strub 1974 Solomon 1974 C l u t t e r 1974 E l f v i n g 1974

Spa t i a1 Adlard 1974 Arney 1974

Mixed Ek and Monserud 1974 M i t c h e l l 1975

Nonspati a1 Leak 1970 Bosch 1971 Namkoong and Roberts 1974 F o r c i e r 1975 Suzuki and Umemura 1974 Horn 1976 Noble and S l a t y e r 1978 Waggoner and Stephens 1970

Gap Mixed V e r t i c a l B o t k i n and o thers 1972 Shugart and West 1977 Mie lke and o thers 1978 Tharp 1978 Shugart and Noble 1980 Shugart and others 1980 Doyle and o thers 1980

cases. All of these models could be used for assessing the consequences of some inferred pollution effect on a region's forests assuming that the primary problem of estimating the for-es t stand response could be overcome.

Spati a1 ly Explicit Tree Models

Two categories of models in table 1 (even-aged or mixed age) are used almost exclusively in sophisticated evaluations of planting,

L i m i t a t i o n s Advantages

Usual 1y c a l i b r a t e d on High degree o f long-term data se ts on r e a l ism because o f many d i f f e r e n t s i t e s . da ta inpu t . Slow t o develop.

F a m i l i a r t o t h e f o r e s t r y indus t ry .

U s u a l l y r e q u i r e s data Provide a r e g i o n a l o r i n s i g h t s t h a t are i n v e n t o r y o f e f f e c t s . c o l l e c t e d over a long t i m e per iod. Mathemat ica l l y

s imple and cou ld be coupld w i t h economic models.

Require ext remely Tremendous d e t a i l . d e t a i l e d growth data and o ther d e t a i l e d Economic v a r i ao les parameters. (e.g., board f e e t ,

products) s imulated C m e r c i a l f o r e s t s o n l y d i r e c t l y . are considered.

Establ ishment may n o t be considered.

Require ext remely Economic v a r i a b l e s d e t a i l e d growth data. (e. g., board f e e t )

s imulated d i r e c t l y . Commercial f o r e s t s o n l y are considered. Fas t computat ional ly ;

cou ld be i n t e r f a c e d Establ ishment may n o t w i t h economic models. be considered.

D e t a i l e d da ta Tremendous d e t a i l . requirement.

Have been proposed Computat ional ly slow. f o r use i n long- term

p o l l u t i o n assessment.

Lack o f d e t a i l i n Models nave oeen output . exp lo red f o r t h e i r

t n e o r e t i c a l aspects. Require c l e v e r va1 i- Level o f a b s t r a c t i o n d a t i on procedures. i s bo th an advantage

and disadvantage.

S p a t i a l i n t h e v e r t i c a l Have been used i n dimension only. 1 ong-term p o l 1 u t i on

assessment. Require c l e v e r v a l i-d a t i o n procedures. Complex parameters

can be i n f e r r e d f rom e c o l o g i c a l p r i n c i p l e s .

spacing, and harvesting schemes in commercial forests. These models produce information used primarily by 1 arge governmental or industri a1 land managers which i s as a consequence, nor-mally communicated by direct means that do not necessarily involve the sc ient i f ic l i tera ture e .g . , internal reports). The models we l is ted i n these categories ( table 1) are probably only a subsample of such models that are actually in use.

These models function by incrementing indi-vi dual trees (usually tree diameter, crown volume, and various form and shape parameters) periodically and are usually solved in 1- to 5-year time steps. To i l lus t ra te the degree of detail used in such models, Mitchell's (1969) model of white spruce (Picea glauca) uses branch-pruning of trees that overlap to deter-mine competition interaction.

The models explicit ly consider the crowding of trees and can be easily adapted to either even- or mixed-age stands. In fac t , Hegyi's (1974) even-aged model i s derived from Arney's(1974) mixed-age model, and Mitchell Is (1969,1975) models are derived in the converse man-ner. The models are designed for commercial fores t ry operations and do not include phenomena that ecologists would expect in a succession simulator. They generally ignore establishment of invading seedlings and often use functions for geometry of trees that could only be expected to hold in young, vigorously growing trees. The models sometimes use thinning or harvest as a surrogate for mortality. Because of the level of detail needed, these models synthesize great amounts of autecological data that are usually only available for commercial species and are di f f icul t to extend to mixed-species forests. Nonetheless, the FOREST model ( E k and Monserud 1974) does simulate mixed-species, mixed-age northern hardwood forest in Wisconsin. This model i s also being considered for use in a pollution effects assessment pro-blem (f ig . 1). There i s also a potential to apply the other models of the commercial speciesthat should be expl ored.

Even-aged, Nonspatial Tree Models

Even-aged, nonspati a1 models have been used in commercial forestry also and are logical non-spatial a1 ternatives to models in the previous category. Nonspatial models have been used almost exclusively in pine (Pinus spp.) planta-tions and are usually in the form of differen-t i a l equations with basal area, stockingdensity, and volume (biomass) of a forest stand changing with respect to time. Because these relationships are functions of the size of the average tree, the models contain parametersderived from the expected growth of trees. The even- aged, mono-speci es character of the simu-lated forests allows the assumption that mathe-matical functions for the expected response of an average or typical t ree are sufficient to express these re1 a t i onships among volume, stock-ing, and basal area. These models work best if the trees tend to be the same size, which helps to explain the use of these models in the more genetically optimized, short-rotation, crop-likePi nus plantations. The underlying assumptions of these models 1 imit their applications to even-aged stands, and the development of mixed-aged models using th i s approach i s d i f f icul t . Unlike the spati a1 mono-species models we dis-cussed previously, these models can, in some

cases, be solved analytically and, in a l l cases, require only a moderate amount of computer time.

Mixed-age, Nonspatial Tree Models

These models simulate ecological succession in naturally regenerated forests. Their empha-s i s i s on birth/death processes affecting indi-vidual trees, and the importance of tree growth and form i s greatly deemphasized. They are not particularly complex (i .e. , birth and death of trees might be treated as simple stochastic processes; rep1 acement of trees as a f irst-order Markov process), b u t frequently i t i s the stated objective of the authors to attempt to capturethe salient aspects of succession with a minimal model representation. In th is objective, the models are actually explorations into the con-sequences of theories and assumptions on the nature of ecological succession based on the attr ibutes of the species involved (Gleason 1926, Drury and Nesbit 1973).

The models can provide considerable insightinto patterns of ecosystem dynamics and can be solved analytically without resorting to digitalcomputation. An example of th i s modelingapproach (Noble and Slatyer 1978) uses the vital at tr ibutes of species to determine the expected patterns of community successions generated bycompetition among the species. Vital at tr ibutes considered are the modes that a species uses to persist at a s i t e , the modes for establishment, the avail abi 1 i t y of a method or persistence (e.g., seeds, vegetative sprouts) at different l i f e stages of the plants (propagule, juvenile, mature, ext inct) , and longevity of individuals. Using these species attr ibutes, they construct schematic diagrams of changes that can be com-pared with observational data from a given area.

Gap Models

Gap models simulate year-to-year changes in diameters of each t ree on a plot of known area. These models do not account for the exact loca-tion of each tree b u t use tree diameters to determine tree height and then use simulated leaf area profiles to devise competition rela-tionships due to shading. These models are spatial in the vertical b u t not the horizontal dimension. This simp1 i f ication greatly reduces the cost of running these models and also elimi- nates the consideration of complex spatial pat-terns of trees, should th i s be important in a given application. The vertical gap models are probably best used in studies of successional dynamics of natural forests considered over longtime spans. Gap models have a1 so been the f i r s t detailed succession simulators applied to a i r pollution effects research.

Current Model Applications

Most models buil t s t r i c t l y for forestry use are usually intended as applications in a restricted set of specified circumstances.

Given the great specificity of the models, they s t i 11 simul ate cornnerci a1 ly important forest types, and i t is unfortunate that they have yet to be used in any pollution effects studies. Several of the succession models presented in table 1 have been used in evaluating environ-mental impacts on naturally occurring forests. Botkin (1973, 1977) considered the effects of CO2 enrichment on plant growth and subsequent effects on forest dynamics. He found t h a t an arbi t rar i ly assumed percentage change in rate of photosynthate production at the individual plant level in CO2-enriched atmospheres was not manifested directly as a change in forest growth. Other effects such as plant competition and shading tended to 1 ower the magnitude of the system response. McLaughl i n and others (1978) and West and other (1980) performed model experiments on chronic a i r pollution stress expressed as a change in growth rates of poll uti on-sensi t i ve trees. They noted that the response of growth over the long term and in natural forests might vary in direction as well as in magnitude from what one might predict from 1 aboratory or greenhouse studies. Kickert ( th i s symposium) and Kercher ( th i s symposium) have also used these gap models of western forests to investigate 1 ong-term pollutant effects. All of these studies identify a common problem; namely, in natural forests where trees vary in spacing, size, and competitive responses, one cannot extrapol ate directly from 1 aboratory studies to f i e ld conditions. Forest succession models can provide and have provided a necessary adjunct t o 1 abor atory-based assessments of environmental effects. We will provide a detailed example of such an application in the following section.

Gap Model Application

As used in the following example, the model (the FORET model, Shugart and West 1977) con-siders 33 forest tree species native to the southern Appal achi an region and simul ates growth of individual trees on a circular 1112-ha plot. The growth of each tree on a plot is incremented yearly as a function of (1) total annual growing degree days (5.6OC base), ( 2 ) the total leaf area of t a l l e r trees on the plot, ( 3 ) total num-ber of trees on the plot, and (4) the size of the tree. A typical simulation is i l lustrated in figure 2.

The selection of a species for the plot and subsequent ini t ia t ion and growth of the tree are based on si lvicul tural characteristics of each species. These characteristics include: (1) s i t e requirements for germination, ( 2 ) pal atabi 1 i ty of seedlings for browsers, (3) sprouting potential, (4) shade tolerance, (5) germi nati on and growth temperature require-ments, ( 6 ) inherent growth potenti a1 , (7) longevity, and (8) sensit ivity to crowding stress ( f ig . 2). The in i t i a l trees established on a plot with bare soil are those having shade- intolerant growth requirements and germination a f f in i t i es for mineral soil. As the simulation

ORNL-OWG 7 8 - 6 4 8 8 R A R

YELLOW POPLAR ( I 1 BLACK OAK (I)

v

WHITE OAK ( R l BLACK CHERRY ( S )

OTHER SPECIES TOTAL BIOMASS 1 0 0

5 0 p'Y

. '& ---0

2 0 0 4 0 0 T I M E ( y r )

Figure 2--Species and stand dynamics of a forest with and without continuous exposure to a i r pollution stress (- unaffected; -----affected).

proceeds, trees that have the abi l i ty t o germinate in leaf l i t t e r and grow under shaded conditions are selected by the model. Leaf l i t t e r is assumed to have accumulated to a level commensurate with the total tree biomass for the plot. The amount of shade cast by each tree i s a function of leaf area of the tree and i s cal-cul ated allometrical ly from i t s diameter by totaling the leaf area of all t a l l e r trees on the plot. Under optimal conditions, tree growth i s assumed to occur at a rate that will produce an individual of maximum recorded size ( d b h ) for that species during the period of maximum recorded age and i s based on a curci linear func-tion that grows a tree to two-thirds i t s maximum dbh at one-half i t s age. Modifications reducing this optimal growth are imposed on each tree by some additive combination of shading and crowd-ing from other trees on the plot and the sto-chastic variation from optimum climate. Optimum climate i s defined as the means of the minimum and maximum growing degree-days within an indi-vidual species range. Death is a stochastic process with the probabi 1 i t y of dying inversely related to the yearly growth increment. Total

stand density characteristics are calculated from dbh. Ingrowth occurs by germination of seeds and sprouting, and simulation may be ini-tiated either from a bare plot or an existing stand of a predetermined composition and structure.

Validation of the FORET model was accom-pl ished by simul ati ng a deciduous forest stand with and without American chestnut as a viable species (Shugart and West 1977). Simulations with chestnut removed produced forests of simi-1 ar composition to the contemporary, post-chestnut blight forest . With chestnut included, the model produced a forest similar (Spearman rank correlation - r = 0.83, see Siege1 1956) in composition to the re1 ati vely undistrubed south-ern Appalachian forest which existed around 1890 to 1910. All simulations were typically repeated for a large number of plots (2loo) ,and interpretations were based on average bi o- mass of individual species and the forest stand determined from the mu1 t i p l e runs.

By uti l izing this type model, we investigated the results of the interaction of forest t ree competition and a i r pollution stress. In doing th i s , the f 011 owing re1 evant questions concern-ing the response of forests to a pollutant were considered:

(1) What level of a i r pollution s t ress would be required to significantly a1 t e r fores t growth and development?

( 2 ) How are s t ress effects integrated over time?

(3) How important i s competition i n moder-ating or enhancing induced stresses on indi-vidual species?

(4) How are species responses integrated into the response of fores t systems?

Application of the model to the study of the effects of a i r pollution stress on growth and development of eastern forests necessitated (1) developing a ra t i onale for cl assifyi ng species in terms of their relative sensi t iv i ty to th is stress and ( 2 ) i ncorporati ng growth reductions into the model which reflected species' sensi-t i v i t y ranking and a range of impacts which might be expected under f i e ld conditions.

Addressing the f i r s t task assumes that spe-cies vary measurably in their growth responses to chronic a i r pollution stress. Such a conclu-sion i s intuit ively obvious from a wealth of data from controlled laboratory and f ie ld studies where obvious differences in sensi t iv i tyof foliage to visible injury from a i r pollution have been demonstrated. Data on relative sensi- t i v i t y of fores t trees to growth reduction from chronic a i r pollution s t ress are limited, how-ever. In th is application, we made the assump-tion that trees most sensitive to fo l i a r injury

would also be most sensitive to growth inhibi-tion. We group the 32 species into 3 sensitiv- i t y classes (resistant, intermediate, and sensit ive), based on their relative sensi t iv i ty to visible injury. The sensit ivity classifica-tion was based on 10 years of f i e ld survey data of vegetation near a coal-fired e lect r ic plant (McLaughlin and Lee 1974) and an extensive sunmary of f ie ld and laboratory data on sus-cept ibi l i ty of woody plants to SO2 and photo-chemical oxidants reported by Davis and Wilhour (1976). This classification then formed a framework for addressing the second task, determining appropriate levels of growth reduc-tion to introduce into the modeled forest . For eastern forests, th is task must also rely on the rather 1 imi ted data currently available from the 1 i terature. However, one advantage of mathe-matical models i s that a range of s t ress levels may be simulated. While not providing exact quantitative answers, such an approach does permit one to bracket the range of l ikely responses based on the best available data.

In the FORET approach, both the influence of varying stress levels and the stage of fores t maturity at which stress was init iated were examined. Results of a typical simulation a r e presented in figure 2. Here, responses of selected species are shown from a simulation in which annual growth inhibitions of 20, 10, and 0 percent were imposed on seedlings in sensitive, intermediate, and resistant sensit ivity classes, respectively. Increases in biomass of 4 major species [yell ow popl ar (intermediate), white oak ( res i s tan t ) , black oak (intermediate), and black cherry (sensitive)] , the coll ecti ve "other" species category, and total stand biomass were com-pared with and without simulated a i r pollution stress as the forest developed over time.

The results indicated that competition within the forest stand may greatly modify responses predicted from individual species' sensi t iv i ty to stress. Both enhanced growth suppression (black oak and black cherry) and reduced sup-pressi on (ye1 1 ow popl a r ) were demonstrated. These responses were attributed to sh i f t s in the competitive potenti a1 of these species induced by differential stress applied within the fores t stand. An examination of total biomass of a l l species indicated that suppression could be greater than (as high as 20 percent) or less than ( < 5 percent) that of the weighted average suppression (7 percent) imposed in the simula-tion.

Another useful capability inherent in sim-ulation approaches i s that variations in stand age and, relatedly, stand composition may be introduced for the time of s t ress init iat ion. In the FORET t e s t , stage of stand development was also identified as an important modifier as shown in figures 3 and 4. Yellow poplar, a f ast-growing, shade-intolerant species which showed growth stimulation when the seedling forest was stressed ( ini t ia t ion time - year O),

0

ORNL-DWG 7 8 - M 0 9 R ORNL- DWG 78-49608R

LIRIODENDRON TULIPIFERA if0 1

40 % STRESS

BEGIN YEAR 0 ----- BEGIN YEAR 50 ......... BEGIN YEAR 400

50 400 450 200 250 309 350 400 450 500 YEARS

Figure 3--Response of ye1 1 ow pop1 a r (Li r i oden- dron t u l i p i f e r a ) t o a 10% reduction in growth. Growth reducing s t r e s s i s applied a t year 0, year 50 or year 400.

showed growth reduction in the more mature f o r e s t ( i n i t i a t i on time - year 50) where other species compete more favorably in the closing f o r e s t canopy. Black oak, on the other hand, when stressed in the seedling fo re s t showed a grea t ly enhanced growth reduction. When. s t r e s s was i n i t i a t e d a t year 50, however, the response was qrea t ly delayed unt i l other more r e s i s t a n t speci-es suih as Ghite oak began t o dominate (see f i g . 2) .

The e f f ec t s of d i f fe ren t ia1 levels of sen-s i t i v i t y on growth and competition of f o r e s t t r e e s which we have shown in f igure 2 are sup-ported by the f i e l d responses of deciduous t r e e s measured by Brandt and Rhodes (1972, 1973). In t h e i r s tudies of the e f f ec t s of 25 years of limestone dust deposition on a deciduous fo re s t , they found changes i n composition, w i t h increased dominance of ye1 1 ow pop1 ar , white oak, and red oak a t the s i t e of heavy dust accumula-t ion . Reduced l a t e r a l growth ( 218 percent) of s ens i t i ve species such as red maple, chestnut oak, and red oak was accompanied by a 76 percent increase i n l a t e r a l growth of yellow poplar a t t he t e s t s i t e near the limestone quarry (Brandt and Rhodes 1973). Evidence of the amplification of e f f ec t s of ab io t i c s t r e s s by both in te r - and in t ra -spec i f ic competition has a l so been

QUERCUS VELUTINA

40 % STRESS BEGIN YEAR 0

----- BEGIN YEAR 505 ........ BEGIN YEAR 400

0

0 50 400 150 200 250 300 350 400 450 500 YEARS

Figure 4--Response of black oak (Quercus velut ina) t o a 10% reduction in growth. Growth reducing s t r e s s i s applied a t year 0, year 50 or year 400.

demonstrated by Fox and Caldwell (1978) in s tudies with UV-B radiat ion. In s i t ua t ions of severe mutual is t ic competition, some species showed improved growth under the UV-B treatment, a response a t t r ibu ted t o improved competitive s ta tus . Other examples of changes in p lan t competition under a i r pol 1 ution s t r e s s were reviewed by Guderian and Kuppers (1980) in t h e preceding paper in t h i s session.

Validation of Forest Community Response t o S t r e s s

While the va l id i t y of model r e su l t s may be readi ly checked against actual growth and devel-opment pat terns of "normal" fo re s t s of a region, evaluation of responses of disturbed f o r e s t s becomes a much more d i f f i c u l t task. I t implies developing a capabi l i ty t o c l ea r ly dis t inguish differences among measured values of parameters of stand growth and composition and those which would have occurred in the absence of pol lutant s t r e s s . Accomplishing t h i s necessi tates e i t h e r obtaining measurements on comparable stands over a var ie ty of s t r e s s leve ls or documenting the growth cha rac t e r i s t i c s of the stand in question before the s t r e s s was i n i t i a t ed . In e i t h e r case, the invest igator i s faced with measuring pol lutant e f f ec t s in the face of the wide vari-e t y of b io t i c and ab io t ic variables control 1 ing

growth of individual trees and forest comnun i t i es.

Historicallyy documentation of forest responses to rather high levels of gaseous pol-lutantsÂ primarily SO2 and HFy from smelting processes was f aci 1 itated by the typical occur-rence of we11 -defined gradients of stress with distance from the sowce. Gordon and Gorham (1963)Â for instance, were able to measure i ncreased numbers of higher p1 ant species a1 ong a 63-km gradient from the smelters at Sudburyy Ontario. These changes followed a generalized pattern of rep1 acement of more highly evolved species of 1 ater successional stages by the more broadly adaptedy stress-tolerant genera1 i s t s which Woodwell (1970) reported following point- source radiation s t ress of a deciduous forest comnun ity.

Present-day a i r pollution stress regimes can generally be characterized as induced by gen-eral ly lower levels of pollutants contributed by mu1 t ip le sources. High-level point sources have been largely replaced by area sources where 1 ocal topography and meteor01 ogy combine to concentrate mu1 t i point eff 1 uents. C1 assic examples are the Los Angeles Basin in the West and numerous industri a1 corri dors a1 ong river valleys in the East. These areas provide good possibil i t ies for examining species and commu-n i ty responses to chronic and occasionally acute stress regimes.

Commun it.y-1 eve1 effects of oxi dants on forests of the San Bernardino Mountains near Los Angeles were described originally by Miller (1973) and have formed a basis for a broadly based study of a variety of ecosystem processes at th i s s i t e . Kickert and Gimnel (1980) used these data in parameterizing a forest simulation model to describe these changes. In the Easty McCl enahen (1978) examined 7 deciduous forest stands located along a gradient of chronic a i r pollution stress on a 50-km portion of the heavi 1y industri a1 ized Ohio River Valley. Species richness evennessy and Shannon diver-s i t y index were genera1 ly depressed for both overstory and understory layers in the forest as proximity to industrial a i r pollution sources increased. Stem density in the overstory decreasedy while lower s t ra ta showed increased abundance of species along this same gradient. Shifts in re1 a t i ve species' importance were a1 so noted.

Studies of the l a t t e r type provide very valuable data for describing the types of changes that may x c u r under moderate pollution s t ressy b u t are limited in their u t i l i t y for predicting rates of change over time or at varying stress levels. Information of th is type may be con-tained in the chronology of t ree growth at that and other s i t e s however. Recent developments in tree-ring analysis provide a potentially powerful tool for analyzing both the rate and direction of within-community changes.

Dendroecology i s a discipline of dendrochro-no1 ogyy the science of dating annual growth rings of woody plants (F r i t t s 1971). I t can be considered a companion tool with dendroclima-tology to examine changes in tree growth in re1 ation to local and regional environment. The basic conceptsy applications, and limitations of dendroecol ogy have been discussed by Fri t t s (1971). In generaly i t re l ies on multivariate s ta t i s t i ca l analysis to identify principal variables influencing tree growth. Resultant equations are in themselves models of individual tree growth over time. As a tool for studying a i r pollution effects, dendroecology permits separation of effects of tree age and local cl imate from those induced by a i r pollution (Nash and others 1975). Phillips and others (1977ayb) have used th i s approach to correlate growth reductions in stands of lob1 01 1y and white pine with production levels near an army munitions plant. More relevant to the chal-lenges of providing reliable predictions of species and community-level changes i s the potential u t i l i t y of th i s technique for detect-ing growth responses in our eastern regional environment. Measurements of growth reductions of white oak in apparent response to chronic s t ress of th i s type have been reported near LaPorte, Indianay by Ashby and F r i t t s (1972). In th is casey the decade during which anomalous growth reductions occurred was associated with a heavy incidence of smoke and haze in that region.

Documentation of pollutant histories in the broader regional context represents a more dif f icul t task b u t one of great importance to efforts to eventually develop a predictive potential. A greatly expanded network of a i r quality trends; howevery data for the past 40 yearsy during which emissions i n the Eastern United States increased sharply, are lacking. One potentially useful tool for obtaining his-tor ies of exposure to genera1 a i r pollution s t ress i s heavy metal analysis in the individual rings (Lepp 1977). This approach has been used in Sweden (Symeonides 1979) to construct his-tories of heavy metal pollutiony a1 though Ti an and Lepp (1975) caution that factors such as radial transport and soil uptake must be fu l ly understood to use th is technique accurately. In the Swedish study, both lead and copper showed l i t t l e lateral movement and were useful in con-structing a decade-level history of metal pollu-tion at the study s i t e . Recent developments coupling x-ray emission spectroscopy (Val kovic and other 1979) with growth-ring analysis show promise for using a variety of trace elements for historical analyses. As these techniques are developed furthery they may provide useful data for constructing historical indices of regional-scale chronic stress.

The tools for validating or modifying fores t simulators as predictive tools appear to be either available now or close at hand. We feel that dendroecol ogi ca1 approaches have tremendous potential for unlocking a wide variety of

species/comunity/environment interact ions which will make t h i s task ul t imately possible. Pro-bablyÂ the grea tes t value of the f o r e s t simula- t o r s i s in predict ing the consequences of s e t s of I'most 1 ogical I' assumptions regarding poll u-t ion e f f ec t s on t rees . Other assumed relat ion-ships can be tested e a s i l y y and new information may be added as i t i s developed (Kozlowski 1980). The mode1 i s merely a tool t o be used in t h i s synthesis and ref ining process.

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Poster Summaries

Effects of Oxidant Air Pollutants on Pine Litter-fall and the Forest Floor 2

Rodney J. Arkley and Rudolph Glauser

Oxidant i n j u r y t o western yellow p ines (Pinus ponderosa and P. Jeffrey!) i n t h e San Bernardino Mountains r e s u l t s i n need le i n j u r y followed by inc reased f a s c i c l e m o r t a l i t y and a b s c i s s i o n , decreased needle l e n g t h , branch m o r t a l i t y and f i n a l l y t r e e m o r t a l i t y . The degree of i n j u r y has been es t ima ted each year f o r 6 yea r s by a scor ing system based on obse rva t ion of a l l of these f a c t o r s w i t h b inocu la r s and combining them i n t o a s i n g l e oxidant i n j u r y s c o r e (01s). Fol iage d e n s i t y i s d i r e c t l y p r o p o r t i o n a l t o OIS a s expected. The number of annual needle-whorls r e t a i n e d (W) i s r e l a t e d t o t h e s c o r e by W = 0.171 x OIS wi th r = .75** and t h e grams of need les pe r twig by F = 2.71 x OIS wi th r = .62*. Note t h a t OIS dec reases w i t h i n c r e a s i n g i n j u r y and a score of 0 i n d i c a t e s a dead t r e e . Scores g r e a t e r than 35 i n d i c a t e no obvious i n j u r y .

EFFECT ON NEEDLE-FALL The oven-dry weight of need les c o l l e c t e d on

0.209 m2 s c r e e n s placed under p i n e s of varying OIS is shown i n Figure 1. The average annual need le f a l l i n c r e a s e s from 131 gm/m2 under h e a l t h y t r e e s t o 357 gm/m2 wi th OIS of 9 t o 14, and dec reases a s t h e t r e e n e a r s dea th ,

The weight pe r need le f a s c i c l e i n t h e l i t t e r - f a l l dec reases p rogress ive ly wi th i n c r e a s i n g i n j u r y a s shown a l s o i n Figure 1. (Sig. < .001).

The inc reased l i t t e r - f a l l (170 pe rcen t ) can be expected t o i n c r e a s e t h e t h i c k n e s s of loose d ry l i t t e r on t h e f o r e s t f l o o r wi th consequent inc reased f i r e hazard and decreased seed l ing germination.

P l a n t Nut r i en t Content L i t t e r - f a l l samples were analyzed t o determine

t h e e f f e c t of oxidant i n j u r y on t h e p l a n t n u t r i e n t of t h e l i t t e r . The r e s u l t s a r e shown i n Figure 2. The s c a t t e r of p o i n t s (not shown) represented by t h e r e g r e s s i o n l i n e s is wide, bu t 187 samples were analyzed and t h e t r e n d s ind ica ted a r e c l e a r l y r e a l , s i n c e they a r e h i g h l y s i g n i f i c a n t (P = < .001). Magnesium was a l s o analyzed b u t

p r e s e n t a t t h e Symposium on E f f e c t s of Ai r P o l l u t a n t s on Mediterranean and Temperate Fores t Ecosystems, June 22-27, 1980, R ive r s ide , C a l i f o r n i a , U.S.A.

2 ~ o i lMorphologist and S t a f f Research Associa te , r e s p e c t i v e l y , Dept. of S o i l s and P l a n t N u t r i t i o n , Unive r s i ty of C a l i f o r n i a , Berkeley, C a l i f .

showed no t r end whatsoever. The response of t h e s e elements i s perhaps due

t o d e c l i n i n g c e l l w a l l th i ckness wi th i t s calcium p e c t a t e and an i n v e r s e d i l u t i o n e f f e c t on N, P, and K.

The d a t a f o r t h e r e g r e s s i o n l i n e s shown i n Figure 2 a r e a s fo l lows:

N(pct) - ,598 - .00255 QIS, r = -.264, n = 187 P(pc t ) = .0707 - .00034 OIS, r = -.28, n = 185 K(pct) = .346 - .00331 OIS, r = -.37, n = 187

Ca(pct) = .303 + .00431 OIS, r = .58, n = 147

0 MEAN 1

"I - RANGE n

I 0* \- 5 NI

/ -\+I \ - .2S'Si

Â

1 I ' Â-./ b - .20 2

Ã1 NEEDLE SIZE - .IS ZI

Oxidont Injury Score Dead 4 Heolthy

Fig. 1. E f f e c t of oxidant i n j u r y on p ine need le f a l l and need le s i z e .

3 I 1 I I 1 1z 01 10 20 3 0 40 50

Oxidant Injury Score Dead < Healthy

Fig. 2. Needle-fall con ten t of p l a n t n u t r i e n t s .

Regional Air Pollution Impacts on Forest Growth

Thomas V. Armentano, Orie L. Loucks, and Wayne T. wi l l iams2

Recent s t u d i e s underway i n t h e Ohio River Basin Energy Study (Loucks 1980) have shown t h a t chronic a i r p o l l u t i o n l e v e l s may b e reducing r e g i o n a l growth over much of e a s t e r n North America. During June through August, 1977, monitoring s t a t i o n s r e p r e s e n t a t i v e of f o r e s t a r e a s recorded hour ly maxima > 0.10 ppm on 14 t o 27 percent of t h e days, and maxima > 0.05 ppm on 70 t o 93 percent of t h e days.

A survey of e a s t e r n whi te p ine (Pinus s t r o b u s L.) s t a n d s i n r u r a l and urban l o c a t i o n s throughout c e n t r a l and sou the rn Indiana showed widespread ozone damage symptoms: c h l o r o t i c mot t l ing , c h l o r o t i c dwarfing and premature need le senescence, on a s c a l e from moderate t o severe . Sycamore (Plantanus o c c i d e n t a l i s L . ) , s i l v e r m a p l e (& saccharinum L . ) , yellow poplar (Lireodendron t u l i p i f e r a L. ) , and t h e black oak group (Quercus spp. ) a l s o a r e somewhat s e n s i t i v e . The 37.3 x l o 6 a c r e s of f o r e s t s i n t h e Ohio Basin y i e l d about 40 f t 3 / a c r e 1 of wood an-n u a l l y , bu t an es t ima ted 25 pe rcen t of t h e f o r e s t c o n s i s t s of 03-sens i t ive s p e c i e s , i n d i c a t i n g a y i e l d r educ t ion from oxidant e f f e c t s (and i n t e r a c - t i o n s w i t h o t h e r gases and pathogens), ranging from 3 t o 6 pe rcen t annual ly (Table 1 ) .

Table I--Total l o s s i n wood product ion i n Ohio River Basin f o r e s t s e s t ima ted t o r e s u l t from d i r e c t and i n d i r e c t a i r p o l l u t a n t e f f e c t s upon f o r e s t growth and m o r t a l i t y r a t e s . To ta l normal wood y i e l d f o r t h e r eg ion i n 1970 was 1 . 5 x 10' f t 3 . Data expressed i n m i l l i o n s of cub ic f e e t .

Wood Annual Product ion M o r t a l i t y

Loss 1 Loss T o t a l Loss 1(pe t . ) 1 ( lobf t3 ) I ( P C ~ . )( 1 0 b f t 3 ) (pe t . )

Independent s t u d i e s i n d i c a t e 03 l e v e l s w i l l in-c r e a s e i n t h e Ohio River Basin over t h e next 20 y e a r s , depending on i n c r e a s e s i n u t i l i t y NOx emis-s i o n s . A conse rva t ive energy development scenar io

'presented a t t h e Symposium on E f f e c t s of Air P o l l u t a n t s on Mediterranean and Temperate Fores t Ecosystems, June 22-27, 1980, R ive r s ide , C a l i f o r n i a , U.S.A.

r e s e a r c h S c i e n t i s t , Science D i r e c t o r , and Research S c i e n t i s t , r e s p e c t i v e l y , The I n s t i t u t e of Ecology (TIE), Ind ianapo l i s , Indiana.

suggests t h a t O 3 l e v e l s w i l l cont inue upward a t l e a s t through 1985. A t t h e c u r r e n t r a t e of 03 in - c rease , 0.02 ppm per decade, wood l o s s e s could reach 166 x l o 6 f t 3 , twice t h e c u r r e n t es t imated l o s s e s (Table 1 ) .

A p a t t e r n of inc reas ing t r e e m o r t a l i t y i n t h e r e l a t i v e l y young e a s t e r n f o r e s t s (30 percent mor-t a l i t y inc rease i n t h e Northeas t , and 10 pe rcen t i n t h e South from 1962 t o 1970) has been repor ted dur ing a per iod of s i g n i f i c a n t a i r p o l l u t i o n in-c reases i n t h e Northeas t (U.S. Fores t Se rv ice 1978). This m o r t a l i t y may be a t t r i b u t a b l e , a t l e a s t i n p a r t , t o degradat ion of a i r q u a l i t y . This hypothesis i s supported by n e a r l y cons tan t m o r t a l i t y i n western f o r e s t s where a i r p o l l u t i o n i s g e n e r a l l y low, d e s p i t e overmatur i ty i n these f o r e s t s . I f mor-t a l i t y l o s s e s i n t h e Ohio Basin were in te rmedia te between those of t h e Northeast and South from 1962 t o 1970, t h e l o s s of wood would be 4.08 f t 3 / a c r e / y r l . Propor t iona te ly g r e a t e r l o s s e s a r e i n d i c a t e d f o r 1985 and 2000 (Table 1 ) .

Other s t u d i e s underway i n d i c a t e t h e s e f o r e s t l o s s e s could be s i g n i f i c a n t f o r t h e g l o b a l C02 balance (Armentano and Rals ton 1980). Because of a f avorab le s t a n d age d i s t r i b u t i o n brought on by p a s t ha rves t p a t t e r n s , temperate zone f o r e s t s now s t o r e around 10' tons of carbon annual ly i n long- l i v e d t r e e components, 20 percent a s much a s t h e carbon r e l e a s e d from f o s s i l - f u e l combustion. This s t o r a g e could cont inue f o r t h e next two decades, bu t increased h a r v e s t , f o r e s t maturat ion, and a i r pol lu- t i o n e f f e c t s can reduce carbon seques te r ing and wood product ion r a t e s . Thus, only management of f o r e s t s focused on a balance between wood product ion and wood accumulation can provide optimum economic and eco log ica l b e n e f i t s . I f p resen t a i r p o l l u t i o n t r ends cont inue, and i f r e l a t i o n s h i p s t o f o r e s t growth suggested i n t h i s paper a r e s u b s t a n t i a t e d by f u r t h e r r e sea rch , t h e long-term p r o d u c t i v i t y of f o r -e s t s w i l l be th rea tened i n s e v e r a l r eg ions of t h e United S t a t e s .

LITERATURE CITED

Armentano, T.V. , and C.W. Rals ton. 1980. The r o l e of temperate zone f o r e s t s i n t h e g loba l carbon cycle . Can. J. For. Res. 10:53-60.

Loucks, O.L. (ed.) . 1980. Crop and Fores t Losses Due t o Current and Pro jec ted Emissions from Coal- f i red Power P l a n t s i n t h e Ohio River Basin. TIE Report i n review. Ind ianapo l i s .

U.S. Fores t Service . 1978. Fores t S t a t i s t i c s of t h e U.S. 1977. De-partment of Agricul ture .

Canopy Analysis of Pollutant Injured Ponderosa Pine in the San Bernardino National Forest l 3

M.C. Axelrod, P.I. Coyne, G.E. Bingham, J.R. Kercher, P.R. Miller, and R.C. ~ u n ~ ~

Nine trees were selected from a ponderosa pine (Pinus ponderosa Laws.! stand which was established after a fire in the mid-1950's. These trees were classified into three injury groups, [(I) slight, (2) moderate, and (3) severe injury] in accordance with a scoring devised by P.R. Miller. During the summers of 1978 and 1979, a detailed inventory was made of the canopy on each tree. The lengths of all main stem internodes

.were measured along with the number of primary branches radiating from each of these internodes. At roughly every other main stem internode, sev-eral of the primary branches received a detailed inventory. The length of the primary branch and the number of internodes were recorded. This inventory was carried on through to the secondary, tertiary, and quarternary branch levels. The compass angle of each of the inventoried primary branches was also recorded. Whenever needles were found on an internode, the following information was recorded: (1) needle age, (2) needle condition on a scale of 0-4, (3) the number of fascicles, (4) the average needle length, (5) the average needle chord width, and (6) the length of the internode bearing the needles. Note that while not all the primary branches at a selected main stem internode were inventoried, the ones selected did receive a complete inventory.

A preliminary analysis of the 1978 canopy data has been completed, characterizing the distribution of needle surface area for each tree. The total needle surface area for each inventoried primary branch was computed separately for each needle age. In order to determine the distribution of needle surface area for a whole tree, we estimated the needle area at the main stem internodes where no data was taken. The curve repre- senting needle area as a function of height is approximately bell-shaped. We have developed an algorithm designed to yield estimates of the missing points and a smooth curve. The algorithm is iterative and uses linear interpolation be-


~lectrical Engineer, Lawrence Livermore Natl. Laboratory (LLNL), Livermore, Calif.; Plant Phys- iologist, Southern Plains Range Research Station, uSDA/SEA/AR, Woodward, Okla.; Environmental Scien- tists, LLNL; Research Plant Pathologist, Pacific Southwest For. and Range Exp. Stn., Riverside, Calif.; and Environmental Scientist, LLNL.

work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore Natl. Laboratory under contract number W-7405- ENG- 48.

tween known points to produce a set of initial estimates. The algorithm first computes the cumulative needle surface area as a function of height, then a linearizing transformation is made. Linear interpolation is carried out on this new curve. The transformation is then inverted and first differences taken, resulting in a reproduction of the original data and a new set of estimates for the missing data. The new estimates are used as initial values each iteration. A weighted average of the needle conditions for each primary branch was also computed. These averages are then combined to yield an index of the condition of the needles on the whole tree.

In table 1A, we see the total leaf area index for each needle age class, with the trees grouped into injury classifications. We can see the leaf area indices decrease across injury classes within age groups. There is a pronounced decrease in the retained leaf area with needle age even in the slightly injured group; the severely injured group has essentially no needle area except in the 1 year age category. Table 1B shows the (weighted) average needle condition for the inventoried trees and presents further evidence that ozone injury is dose accumulative with young needles being less affected by ozone than older needles. Since the current year needles were still growing at the time the initial inventory was taken, they were inventoried separately the following year. This data is still being processed and is not yet available, but is expected to add proportionately to the numbers presented here. The trend in leaf area decline indicates the competitive disadvantage of an injured tree.

Table I--Needle properties by needle age for nine trees under pollution stress. -

(A) Leaf Area Index Injury Class 1 Year 2 Year 3 Year

Slight 9.53 4.13 0.70 Moderate 5.23 0.73 0.00 Severe 3.55 0.03 0.00

(B) Average Needle condition2 of Canopy

Slight 0.96 1.31 1.28 Moderate 2.18 2.42 NA Severe 2.63 NA NA

"~oes not include data for current year needles. Averages for 3 trees in each injury class.

~ e e d l e condition scale: 0 = green; 2 = chlorotic mottle. 4 = uniform yellow with necrosis.

Photosynthesis and Stomatal Behavior in Ponderosa Pine Subjected to Oxidant Stress: Water Stress Response 1 1 2

Gail E. Bingham and Patrick I. coyne3

Light response curves for net and/or gross photosynthesis, stomatal conductance, and needle xylem potential of ponderosa pine (Pinus ponderosa Laws.) subjected to water and/or ozone stress were studied in the field and laboratory. In the field, measurements were made on a stand of ponderosa pine in the San Bernardino National Forest, which has experienced long-term oxidant fumigations from the south coast air basin since their establishment following fire in the mid-1950's. These trees were stratified for comparative studies into three groups (slight injury, moderate injury, and severe injury) having similar oxidant symptoms, on the basis of the scoring system of P.R. Miller.

Controlled studies using ten healthy, uniform, Oregon-grown, six-year-old saplings growing in 55 1 containers were conducted to elucidate specific field responses. These trees were approximately 2 m tall, and were randomly allocated to positions in two naturally-lighted, mylar- covered, air and humidity conditioned exposure chambers. One chamber was supplied charcoal filtered air and the other with air containing 0.01 ppm ozone for six hours/day during the midday period.

Measurements were made at regular intervals from May through October at the forest site and during the fumigation and water stress cycles in the laboratory. During the laboratory study, net photosynthesis (Pn) and stomatal conductance (Cs) measurements were made at constant humidity and temperature using the LLNL developed minicuvette system, with only the fascicle being measured and a few surrounding needles exposed to light. The rest of the tree was surrounded with heavy black cloth from before dawn until after light response curves had been measured on three fascicles.

The relationship between needle xylem potential and maximum stomatal conductance (Cmax) was not single valued, and depended on predawn

"presented at the Symposium on Effects of Air Pollutants on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, California, U.S.A.

'work performed under the auspices of the U. S. Dept. of Energy by the Lawrence Livennore National Laboratory under contract number W-7405-ENG-48.

3~nvironmental Scientist , Lawrence Livermore National Laboratory, Livermore, Calif.; Plant Physiologist, Southern Plains Range Research Station, USDA/SEA/AR, Woodward, Okla.

qX. When predawn ifiv was in the range from -3 to -5 bars, Cs (and Pn) decreased only slightly during the normal daily decrease in ifiv due to changes in the diurnal course of irradiance. Minimum iy under these conditions seldom exceeded -14 bars. However, when $x was forced below -15 to -17 bars (by severing the fascicle from the branch) a sharp decrease in Cs occurred, with complete stomatal closure (Cs<O.O1 cm/s) in the range of -36 to -40 bars. When predawn started in the -5 to -8 bar range, however, a bilevel relationship between Cg and iy was observed, with Cmax reaching an initial full light value, followed at some later time by a step decrease to a lower value. Conductance and Pn remained at this significantly lower level throughout most of the day, with an accelerated closing trend toward the late afternoon. Late afternoon values were usually only 60 to 70 percent of their light corrected morning opening value.

Care had to be taken when interpreting pre-dawn $x measurements in the field. It was often observed that at 'a predawn ifiv of -3 to -7 bars, the stomata would partially open in the predawn hours, resulting in Cs values approaching one-tenth of their full light value. Under these conditions, sufficient transpiration occurred to make predawn qX very sensitive to wind speed. Differences between predawn $x on calm and windy mornings as large as 3 bars were observed.

The second factor depended solely on the predawn xylem potential and controlled the maximum stomatal conductance (Cmax) observed during the diurnal cycle. This relationship could not be adequately examined in the forest due to untimely late season rains during the three years that field studies were conducted, and was investigated using potted trees. As predawn $x decreased below -7 bars in control trees and about -10 bars in fumigated trees, a drastic reduction in Cmax and Pn was observed. In trees kept in filtered air, Cmax was decreased from 0.36 to 0.036 cm/s by the decrease of predawn $x from -5 to -15 bars. Since the majority of the tree was kept in the dark during the measurement, the relationship between Cs and $x at QX values greater than can normally be observed in nature (due to root and xylem resistance) were examined. Conductance and Pn of fumigated trees in this region was not significantly higher than that observed at potentials associated with full illumination. Reductions in GaXof 25, 31, and 44 percent were measured for slight, moderate, and severely injured needles. Net photosynthesis for the same needle injury classes was reduced by 38, 54, and 69 percent from the 12.9 mgco2/dir -h rate measured in trees which had not been exposed to ozone.

Oxidant Impact on Ponderosa and Jeffrey Pine Foliage Decomposition1

2J. N. Bruhn, J. R. Parmeter, Jr., and F. W. Cobb, Jr.

Litter decomposition was studied on four plots located along the oxidant dosage gradient in the San Bernardino Mountains (SBNF). Precipitation decreased with decreasing oxidant dosage along this gradient, while forest floor-level solar radiation and temperature ir .eased. Ponderosa (Pinus ponderosa Dougl.) a1.d Jeffrey pine (Pinus Jeffrey! Grev. & Balf.) dominated the most and least severely impacted sites, respectively. Nylon mesh envelopes of fresh-fallen litter were exchanged among healthy and sick trees on the four study sites. Decomposition was measured as percents overall and nutrient (N, P, K. Ca and Mg) weight loss.

During the first two years of decomposition, its rate at each site was directly related to precipitation and oxidant dose. While site moisture apparently dominates litter decomposition, evidence suggests that oxidant injury to live needles is directly related to the rate at which they decompose. One year weight loss of ponderosa pine litter was negatively correlated (P .05) with the oxidant injury scores (O.I.S.)(Miller 1973) of litter source trees. One year weight loss by litter of both species was negatively correlated (P .05) with the O.I.S. of litter destination trees.

Live needle internal microflora may be initiated in the foliar bud and can be thought of as pioneers in a succession of microorganisms re-sponsible for litter decomposition. Microbial populations involved in foliage decomposition were studied via incubation of surface-sterilized live and litter needles on water agar. Eight trees from each of two central Sierra Nevada sites, Stanislaus National Forest (SNF) and Blodgett Experimental Forest (BEF), were included for comparison with the 15 SBNF study trees. Both taxonomic richness and population density increased with needle age. Both parameters increased similarly with age on all four SBNF sites. However, both parameters increased faster on the somewhat less oxidant-impacted BEF, and both parameters developed fastest on the least oxidant-impacted site (SNF).


2~nstructor of Forest Pathology, Michigan Technological University, Houghton, Mich.; Pro- fessor and Associate Professor of Plant Pathology, respectively, University of California, Berkeley, Calif.

Because not all fungi recorded in incub ation studies were identified, they are individually referred to as categories rather than species. Live SNF foliage yielded approximately twice as many fungus categories (60) as foliage from any other site. The two BEF plots harbored a few more categories (29 and 32) than did HV (27), the healthiest SBNF site. HV, in turn, provided more categories than any other SBNF site (15 to 20). Similar effects were not evident in forest floor litter. Oxidants apparently affect live needle microflora in two ways. By reducing needle longevity, internal microflora development is prematurely truncated. It also seems likely that oxidants further reduce the variety of fungi coloniz- ing live pine foliage by eliminating susceptible species. Insofar as community functional properties are stabilized by a combination of species adaptability and community diversity, reduction of live foliage microfloral diversity by oxidants is viewed as weakening the functional stability of these communities. The significance of such weakening is unknown.

In a growth chamber experiment, propylene oxide- sterilized pine needles were incubated on moist forest floor organic matter from either Che SNF or one of the SBNF sites. No meaningful differences in weight loss developed between treatments over 22 weeks, showing that oxidants to date had not significantly impaired the abilities of study-site microflora to cause litter weight loss. In a sec-cond growth chamber experiment, propylene oxide- sterilized pine needles were incubated on a uniform moist forest floor organic matter mixture in either filtered air or filtered air enriched with 20pphm ozone 8 hours daily for 14 weeks. The weight loss difference between treatments did not reach significance ( .05 P .01). Any effect in the field would be slight and probably limited to surface litter during moderate to severe oxidant episodes.

Acknowledgments: This project was funded in part with federal funds from the Environmental Protection Agency (E. P. A.) under contract number 68-03-0273.

LITERATURE CITED

Miller, P. R. 1973. Oxidant-induced community change in a mixed conifer forest. In Air pollution damage to vegetation. p. 101-117. Advances in Chemistry Series, Number 122. American Chemical Society.

Integrated Lake-Watershed Acidification Study

Carl W. Chen and Robert A. olds stein'

OBJECTIVES

The Integrated Lake-Watershed Acidification Study (ILWAS) was designed to determine the ecological effects of acid rain under natural conditions (EPRI, 1979, Goldstein et al., 1980). Since the most widely reported effect of acid rain has been the acidification of lake water leading to elimination of fish, it is of interest to learn how and why the ecosystem becomes acidified by acid rain.

Three forested watersheds (Panther, Woods, and Sagamore) within 15 km of each other in the Adirondack Park region of New York were selected for investigation. Each watershed has different configurations and characteristics. Principle hypothesis of the study is that these differences may lend to different pH dynamics, i-e., Panther Lake alkaline, Woods Lake acidic, and Sagamore Lake in-between.

This research will produce a comprehensive data base for the three watersheds covering a period of almost 4 years, a series of interpretive reports, and a calibrated and verified mathematical model. The wealth of understanding gained and the mathematical model developed will be readily applicable to other lake basins.

APPROACH

ILWAS couples field investigation with theoretical modeling. The interactions between the model and the field research are practiced in an interactive manner, each influencing and strengthening the other. Other research findings on mechanisms and rates of acidification processes are integrated into the model formulations.

FIELD PROGRAM

The watershed ecosystem is envisioned to comprise a cascade of basic compartments: atmosphere, canopy, snowpack, catchment, soil layers, bogs, stream segment and lake. These are the compartments that the acid rain must pass through before it reaches lake outlet. As it passes through each compartment, biogeochemical processes acting in


2~ice-~resident,Tetra Tech, Inc. , Lafayette, California; Program Manager, Electric Power Research Institute, Palo Alto, California

series and in parallel will produce or consume acids and will release chemicals that shift the pH and other chemical equilibrium.

-Meteorology1 -Air duality

Rain Quality

-Throughfall Chemistry

-Hydraulics -Geochemistry - Microbial Processes (& Lab)

Hydrology-Aquatic Chemistry

Hydrology

-Aquatic Chemistry

- Paleoecology

Hydrology

Figure 1--Field Program Components

Field surveys are being conducted to characterize the properties of the basic ecosystem compartments in each watershed. At selected locations, measurements are made for ambient air quality, the quantity and quality of waters that move through the system from tree top to lake outlet (see fig. 1). Data are collected monthly, weekly, synoptic, and once only, depending on the parameters and their temporal variability. The field program began in 1977 and will be completed in 1981.

MODELING

The model organizes the data into an integrated theoretical framework (Goldstein et al., 1980). The model also serves as a vehicle to check the consistency of theory and data from rainfall quantity to lake outlet quality. Eventually, the model may provide scientific answers to such management questions as: What will and will not happen if a certain air quality standard is imposed, and if the acidity of precipitation is increased or decreased.

The model flowchart shows the computation se-quence (fig. 2 ) . The model calculates dry deposition as a function of ambient air quality and simulates the quantity and quality of water in throughfall, soil horizons, bogs, stream, lake, and lake outlet (Chen et al., 1978). All important acidification processes are included in the model.

Ambient air quality

Basin properties

Dry deposition Exudate

Calculate Throughfall chemistry

Snow accumulation Snowmelt Ion-teaching

Calculate . Soil moisture Vertical infiltration Lateral outflow

+ Organic decomposition Nutrient uptake

.Weathering Cation exchange Equilibration (At-sys, etc.)

Quantity and quality of H20 through stream

Figure 2--Model Flowchart

The model uses a network of compartments to account for spatial variability of ecosystem. It updates meteorological conditions daily and ambient air quality weekly. The calculations are performed on a daily time step to simulate the dynamic responses of ecosystem throughout years. Graphic outputs are provided to facilitate interpretation.

PRELIMINARY FINDINGS

Data indicate that the H+ deposition rates are seasonal and are approximately the same for all three watersheds (Johannes and Altwicker, 1980). The seasonal pattern of H+ deposition seems to follow that of SO4 deposition (Johannes, 1980). The deposition rates of various ions in acid rain as measured at seven ILWAS stations correlate well with those measured at the nearby MAP3S stations. This is significant because it suggests that acid rain data from regional monitoring stations may be used to perform preliminary calculation of acid rain effect for a new site.

The pH at Panther Lake inlet is normally 7.3 to 7.5 throughout the year. The pH at the outlet is similar except during the snowmelt periods. Dur- ing that period, pH drops to as low as 5.0. Some- thing must have happened in the lake. Alterna- tively, it was argued that the inlet was only a small spring, not representative of all inflows.

The pH profiles measured in the lake show that only surface water is acidified during the period of snowmelt (Hendrey et al., 1980). What is the source of H+ ions that acidify the lake surface?

To resolve the puzzle, the model was used to help trace the source of water at the outlet. The model was first calibrated to the Panther Lake basin (Chen and Goldstein, 1980). After that, precipitation falling directly on lake surface is set to zero. This allows estimation of the contributions of this input to the total observed outflow. Approximately two-fifths of the peak flow can be accounted for by the direct precipitation to the lake surface. During that period, lake water is inversely stratified with respect to temperature. Direct precipitation which has a pH of 3.8 to 4.2 quite possibly is deposited right on the surface to acidify the lake surface water (pH 5.0). Another possible explanation is surface runoff resulting from snowmelt which has a high acidity (Galloway et al., 1980).

The significance of the capability to manipu- late the model to examine the effect of a single process on the integrated response of the ecosystem should not be overlooked.

LITERATURE CITED

Chen, C.W., S.A. Gherini, and R.A. Goldstein. 1978. Modeling the Lake Acidification Process. In Ecological Effects of Acid Precipitation, - Report of a Workshop, Galloway, United King- dom, September 4-8, 1978, ed. M.G. Wood, Electric Power Research Institute, Palo Alto, CA, U.S.A., EA-79-6-LD.

Chen, C.W., and R.A. Goldstein. 1980. "Techniques for Assessing Ecosystem Im- pacts of Air Pollutants." & Proc. Inter- national Conference Air Pollutants and their Effect on the Terrestrial Ecosystem [May 10- 17, 1980, Banff, Alberta, Canada].

EPRI Technical Work Statement for the Integrated Lake-Watershed Acidification Study RP 1109. 1979. Electric Power Research Institute, Palo Alto, California.

Galloway, J.N., C.L. Schofield, G.R. Hendrey, and A.J. Johannes. 1980. "Sources of Acidity in Three Lakes Acid- ified During Snowmelt." In Proc. of Inter- national Conference on the Ecological Impact of Acid Precipitation, [March 11-14, 1980, Sandefjord, Norway].

Goldstein, R.A., C.W. Chen, S.A. Gherini, and J.D. Dean. 1980. A Framework for the Integrated Lake- Watershed Acidification Study. & Proc. of International Conference on the Ecological Impact of Acid Precipitation, [March 11-14, 1980, Sandefjord, Norway].

Hendrey, G.R., J.H. Galloway, and C.L. Schofield. 1980. "Temporal and Spatial Trends in the Chem- istry on the Ecological Impact of Acid Pre-

cipitation." Proc. of International Con- ference on the Ecological Impact of Acid Precipitation, [March 11-14, 1980, Sandef jord, Norway] .

Johannes, A.H., and E.R. Altwicker. 1980. "Atmosphere Imputs to Three Adirondack Lake Watersheds." 3 Proc. of International Conference on the Ecological Impact of Acid Precipitation, [March 11-14, 1980, Sandefjord, Norway] .

Photosynthesis and Stomatal Response to Light and Temperature in Ponderosa Pine Exposed to Long-Term Oxidant Stress1

P a t r i c k I.Coyne and Gai l E. ~ i n ~ h a m *

Seasonal courses (May t o October 1977) o f gross photosynthes is ( c a l c u l a t e d from CO2 uptake) and stomatal conductance were charac te r i zed as a f u n c t i o n o f l i g h t and gross and n e t photosynthes is were charac te r i zed as a f u n c t i o n o f temperature (May and J u l y 1978) i n a s tand o f ponderosa p i n e (Pinus ponderosa m.)i n t h e San Bernardino Na t iona l Forest . The CO2 d i f f u s i o n pathway was p a r t i t i o n e d i n t o i t s stomatal and r e s i d u a l (mesophyll , carboxy la t i on , e x c i t a t i o n ) res i s tance components f o r c o n d i t i o n s o f l i g h t s a t u r a t i o n and 20 C. These t r e e s have exper i - enced l o n g term o x i d a n t fumigat ions f rom C a l i f o r - n i a ' s South Coast A i r Basin s ince t h e i r e s t a b l i s h ment f o l l o w i n g f i r e i n t h e mid-1950's. Nine trees were s t r a t i f i e d f o r comparative s tud ies i n t o three ch ron ic i n j u r y c lasses ( I - s l i g h t i n j u r y , I 1 -moderate, I 1 1 - severe) hav ing s i m i l a r ox idan t i n j u r y symptoms based on t h e sco r ing system o f P. R. M i l l e r .

Maximum o r l i g h t sa tu ra ted gross photosyn- t h e t i c r a t e s (Pmax) and photochemical conversion e f f i c i e n c i e s (dP/dI ) I=o were h ighes t i n t h e cur - r e n t needles and decreased w i t h i nc reas ing nee- d l e age and w i t h season. D i f fe rences among nee- d l e age c lasses w i t h i n an i n j u r y c l a s s d iverged as t h e season progressed i n d i c a t i n g an acce le r - a t i o n o f senescence b y ozone. Maximum stomatal conductances (Cmax) and stomatal s e n s i t i v i t y t o i nc reas ing 1 i g h t (dC/dI) I=o d u r i n g opening f o l - lowed a s i m i l a r t r e n d t o Pmax and dP/dI except i n t h e c u r r e n t needles i n which Cmax and dC/dI were h i g h e s t i n t h e severe ly i n j u r e d t rees . Th is suggests a p o s s i b l e f a c t o r c o n t r i b u t i n g t o d i f - f e r e n t i a l ozone s e n s i t i v i t y i n t h i s stand. The r a t i o o f t h e stomatal r e s i s t a n c e f o r CO2 ( r l ) t o t h e t o t a l r e s i s t a n c e (r', s tomata l+res idua l ) decreased w i t h o x i d a n t i n j u r y , i nc reas ing 'need le age, and season suggest ing t h a t l o s s o f photo- s y n t h e t i c c a p a c i t y r e s u l t e d more from 1 i m i t a t i o n s a t t h e c h l o r o p l a s t s than from res i s tance t o CO2 d i f f u s i o n through t h e stomata.

Temperature optima (Top ) f o r photosynthesis were s i m i l a r i n a l l i n j u r y c lasses and averaged

'presented a t t h e Symposium on E f f e c t s o f A i r P o l l u t a n t s on Mediterranean and Temperate Fores t Ecosystems, June 22-27, 1980, R ivers ide, C a l i f o r n i a , U.S.A.

2 ~ 1 a n t P h y s i o l o g i s t , Southern P l a i n s Range Research S ta t i on , USDA/SEA/AR, Woodward, Okla.; and Environmental S c i e n t i s t , Lawrence Livermore Laboratory , Livermore, Cal i f .

^h is work was supported by a U.S. Dept. o f Energy c o n t r a c t (W-7405-ENG-48) w i t h Lawrence Livermore Laboratory .

about 20Â° i n May and 25OC i n J u l y . L i g h t r e s p i - r a t i o n (es t imated as Pgross-Pnet) was h i g h e s t i n hea l thy younq needles and increased w i t h tempera- t u r e from 5Â° t o To t and then l e v e l e d o f f between Topt and 35OC. ~lthough l i g h t r e s p i r a t i o n was i n v e r s e l y r e l a t e d t o ox idan t i n j u r y , t h e r a t i o o f Pnet/P ss tended t o decrease w i t h o x i d a n t injury. ~ ~ ~ a r e n t ? ~ox idan t s t ressed t r e e s n o t o n l y had reduced r a t e s o f CO2 f i x a t i o n , b u t r e t a i n e d a smal l e r p r o p o r t i o n o f a s s i m i l a t e d carbon a f t e r r e s p i r a t i o n losses. Summary data f o r s e l e c t parameters are compared i n Table 1.

Table 1--Comparison o f s e l e c t parameters normal- i z e d by d i v i d i n g each mean by t h e maximum mean va lue i n each column.

I n j u r y Needle 1977 Means Class Age Pmax ] Cmax lr;/r1

I 0 1.00 0.89 1.00 1 0.61 0.84 0.80 2 0.32 0.62 0.59

II 0 0.92 0.92 0.82 1 0.53 0.75 0.71 2 0.17 0.38 0.40

III 0 '0.79 1.00 0.59 1 0.35 0.57 0.45

Max. value1 8.30 0.24 0.29

J u l y 1978 Pgross-Pnet

1.00 0.60 0.35 0.95 0.51 0.18 0.94 0.35 2.46

^ p a r meters d e f i n e i n t e x t . Un i t s : P, mg CO2 g -7t-1-1; C, cm s-y ; r, s cm-1; age i n years.

The d i f f e r e n t i a l response i n photosynthes is and stomatal conductance among these f i e ld -g rown ponderosa p ine t r e e s growing i n a common env i ronment i n d i c a t e d t h e presence o f eco typ ic v a r i a t i o n i n ozone s e n s i t i v i t y . The d i f f e r e n c e s among i n j u r y c lasses were man i fes t as an a c c e l e r a t i o n o f t h e normal d e c l i n e i n CO2 f i x a t i o n and stomatal conductance assoc ia ted w i t h needle aging. Par t i c -u l a r l y ev iden t were t h e premature senescence and absc iss ion o f needles o c c u r r i n g a t about t h e t ime gross CO2 uptake dropped t o 10 percent o f t h e p o t e n t i a l f o r c l a s s I c u r r e n t needles w i t h o u t f o l i a r i n j u r y symptoms. T h i s occurred a t i n t e -gra ted i n c i d e n t ozone doses as low as 450 ppm-h i n severe ly i n j u r e d t r e e s ( c l a s s 111) o r as h i g h as 800 ppm-h i n s l i g h t l y i n j u r e d t r e e s ( c l a s s I ) .

A probable scener io f o r ox idan t e f f e c t s can be descr ibed. As f o l i a r i n j u r y symptoms increase, photosynthet ic capac i t y and n e t carbon accumula- t i o n pe r u n i t l e a f mass o r area, mass and area per needle, needle mass per u n i t area, and number o f needle whor ls r e t a i n e d pe r t r e e dec l i ne . These f a c t o r s c o n t r i b u t e t o t h e steady l o s s o f t r e e v igo r , weakening them t o t h e p o i n t o f v u l - n e r a b i l i t y t o pathogenic organisms such as r o o t r o t t i n g f u n g i and bark beet les .

----- --

The Effect of Air Pollution on Western Larch as Detected by Tree-Ring Analysis1

Car l A . Fox and Thomas H. Nash 1112

The number of p u b l i c a t i o n s i n r e c e n t y e a r s d e a l i n g w i t h t h e e f f e c t s o f a i r p o l l u t i o n on p l a n t s has been voluminous. A v a s t m a j o r i t y of t h e s e have d e a l t wi th t h e e f f e c t s of shor t - te rm (hours o r days) fumiga t ions on p l a n t response. I n con-t r a s t t o t h e s e s t u d i e s , t h e r e i s r e l a -t i v e l y l i t t l e i n f o r m a t i o n on t h e l ong -term, cumulat ive e f f e c t s o f a i r p o l l u t i o n over decades. To examine t h e s e long-term e f f e c t s , a dend roeco log ica l ( t r e e - r i n g ) a n a l y s i s was employed t o a s s e s s t h e growth r e s p o n s e o f w e s t e r n l a r c h ( L a r i x o c c i d e n t a l i s N u t t . ) t o s u l f u r d i o x i d e . U t i l i z a t i o n of dend roeco log ica l t echni -ques provided a means f o r q u a n t i t a t i v e l y removing t h e e f f e c t o f c l i m a t e on t h e g r o w t h r e s p o n s e o f l a r c h a n d , t h u s , pe rmi t t ed a n examinat ion of t h e r e s i d u a l g r o w t h r e s p o n s e i n t e r m s o f l o c a l s i t e f a c t o r s , s p e c i f i c a l l y s u l f u r d i o x i d e .

F i v e wes te rn l a r c h s tudy s i t e s were l o c a t e d i n t h e Columbia River Val ley n e a r t h e lead-z inc s m e l t e r a t T r a i l , B r i t i s h C o l u m b i a . T h i s p a r t i c u l a r l o c a t i o n r e p r e s e n t s a unique s tudy a r e a i n t h a t t h e s u l f u r d i o x i d e g r a d i e n t h a s been w e l l documented , b o t h o v e r s p a c e and t i m e , s i n c e s m e l t i n g a c t i v i t y began i n 1896 .

S u l f u r e m i s s i o n s f rom t h e s m e l t e r i n c r e a s e d i n t h e e a r l y 19001s , reached a maximum i n 1930, and r e s u l t e d i n a con-commitant dec rease i n annual t r e e growth. A f t e r 1930 , s u l f u r e m i s s i o n s d e c r e a s e d d r a m a t i c a l l y w i th t h e implementat ion of p o l l u t i o n abatement measures. However, t h e growth response of wes te rn l a r c h t o t h e d e c r e a s e d s u l f u r e m i s s i o n s was n o t immediate, and r e f l e c t e d t h e low frequency n a t u r e o f t h e v a r i a n c e o f t h e s u l f u r d i o x i d e e f f e c t on t r e e growth.

p r e s e n t e d a t t h e Symposium on E f f e c t s of A i r P o l l u t a n t s on Mediterranean and Temperate F o r e s t Ecosystems, June 2 2 - 2 7 , 1980, R i v e r s i d e , C a l i f o r n i a , U.S.A.

^ ~ e s e a r c hS c i e n t i s t , Southern C a l i f o r n i a Edison Company, Rosemead, C a l i f o r n i a ; Assoc i a t e P r o f e s s o r of Botany, Arizona S t a t e U n i v e r s i t y , Tempe, Arizona.

C o r r e l a t i o n and r e g r e s s i o n a n a l y s e s were u t i l i z e d t o d e v e l o p m u l t i v a r i a t e models f o r t h e l a r c h s tudy s i t e s sampled a t v a r y i n g d i s t a n c e s f r o m t h e T r a i l sme l t e r . Cl imat ic models developed f o r t h e c o n t r o l s i t e ( t r e e - r i n g ) chronology were app l i ed t o s i t e chronologies l o c a t e d w i t h i n t h e s u l f u r d iox ide a f f e c t e d a r e a t o remove t h e e f f e c t s o f c l i m a t e on t r e e growth and examine t h e r e s i d u a l response of t h e system. The p a t t e r n of t h e r e s i -d u a l s c l o s e l y resembled t h e s u l f u r emis-s i o n s f r o m t h e s m e l t e r w i t h t h e m o s t n e g a t i v e r e s i d u a l s o c c u r r i n g when s u l f u r emiss ions were g r e a t e s t .

F u r t h e r r e g r e s s i o n modeling i d e n t i -f i e d t h e r e l a t i v e i m p o r t a n c e o f s u l f u r emiss ions , p r i o r y e a r ' s growth, tempera-t u r e , and p r e c i p i t a t i o n t o a n n u a l f r e e g rowth . I n t h o s e s i t e s c l o s e s t t o t h e s m e l t e r , s u l f u r emiss ions accounted f o r t h e g r e a t e s t p ropor t i on of t h e v a r i a n c e c a l i b r a t e d b y t h e r e g r e s s i o n models. A s d i s t a n c e from t h e s m e l t e r i n c r e a s e d , t h e va r i ance a t t r i b u t a b l e t o s u l f u r emiss ions decreased i n each s i t e model. I n a l l of t h e s i t e models, t empera ture , p a r t i c u l a r l y summer t e m p e r a t u r e , a p p e a r e d t o b e a primary l i m i t i n g c l i m a t i c f a c t o r . P r i o r g rowth a l s o a c c o u n t e d f o r c o n s i d e r a b l e va r i ance i n t h e models wi th p r e c i p i t a t i o n v a r i a b l e s a p p e a r i n g t o be o f l e s s e r importance i n e x p l a i n i n g t h e v a r i a n c e of t h e s i t e chronologies .

The r e s u l t s of t h i s s t u d y demon-s t r a t e t h e a p p l i c a b i l i t y of t r e e - r i n g a n a l y s i s i n i d e n t i f y i n g and q u a n t i f y i n g t h e long-term e f f e c t s of a i r p o l l u t i o n on f o r e s t communities. It a l s o p rov ides a b a s i s f o r examining t h e i n t e r r e l a t i o n s h i p s between a i r p o l l u t i o n , c l i m a t e , and t r e e growth.

Acid Rain: Threshold of Leaf Damage in Eight Species from a Forest Succession1

2B.L. Haines, M. S te fan i , and F. Hendrix

Eight p l a n t spec ies were subjected t o a r t i - f i c i a l a c i d r a i n s of pH 2.5, 2.0, 1.5, 1.0, and 0.5 i n order t o determine t h e threshold f o r and symptoms of damage. I n a previous study a r t i - f i c i a l ac id r a i n s of pH 5.5, 4.5, 3.5, and 2.5 f a i l e d t o produce symptoms of damage. The pre- s e n t s tudy was designed t o extend t h e pH range. The p l a n t s were E r e c h t i t e s , Robinia, Pinus, Quercus, Carya, Liriodendron, &, and Cornus from t h e Fores t s e r v i c e ' s owee eta ~ ~ d r o l o ~ i c -Laboratory near Frankl in , North Carolina. Du-p l i c a t e 0.01 m l drops of each of t h e 5 simulated ac id r a i n s o l u t i o n s were appl ied t o a s i n g l e mature l ea f on each of two p l a n t s of seven spe- c i e s . The e n t i r e experiment was performed twice. I n Pinus needle t i p s were immersed i n t h e solu- t ions . The s i z e s of n e c r o t i c spo ts a r e shown i n Fig. 1. Droplets of pH 2.0 produced brown nec- r o t i c s p o t s on a l l spec ies except Pinus whi le d r o p l e t s of pH 1.0 produced necroses on leaves of a l l spec ies examined. Pinus needles were dam-aged a t pH values between 1.0 and 0.5. Damage was confined t o younger needles and was evidenced by browning and col lapse. For angiosperms t h e s i z e s of n e c r o t i c s p o t s increased with decreasing pH. This suggests t h a t t h e l e a f has some buf fe r ing capaci ty which was p rogress ive ly overcome by increas ing d r o p l e t a c i d i t y . Comparison of re-s u l t s wi th l i t e r a t u r e suggests t h a t developing leaves a r e more e a s i l y damaged than a r e mature leaves used i n t h i s study. No successional t r ends i n s u s c e p t i b i l i t y were observed.

p r e s e n t e d a t t h e Symposium on E f f e c t s of A i r P o l l u t a n t s on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Rivers ide, Ca l i fo rn ia , U.S.A.

' ~ s s i s t a n t Professor of Botany, Department of Botany, Univers i ty of Georgia, Athens, GA 30602; Graduate Research Ass i s tan t i n P lan t Pathology, and Prof. of P lan t Pathology, Dept. of P lan t Pathology and Genetics, Univers i ty of Georgia, Athens, Georgia 30602. Research supported by U.S. EPA Grant R80530510 and NSF g r a n t s DEB 7619930, DEB 7705324A01 and DEB 7904537 t o t h e Univers i ty of Georgia.

The volume weighted average r a i n f a l l pH f o r Coweeta i s 4.6 with observat ions ranging from 3.2 t o 5.9. Because t h e pH s c a l e i s logar i thmic with a decrease i n 1 pH u ?it corresponding t o a 10-fold inc rease i n t h e H concentrat ion, i t i s apparent t h a t a 100-fold inc rease i n t h e volume weighted average concentrat ion of H a t Coweeta would change t h e pH from 4.6 t o 2.6 which is near t h e threshold of damage. However, t h e extremes may be f a r more c r i t i c a l than t h e volume weighted average. With t h e lowest pH va lue recorded f o r Coweeta being pH 3.2, merely a 10-fo ld inc rease i n a c i d i t y t o pH 2.2 i n a s i n g l e spr ing o r summer storm seems l i k e l y t o b r ing damage o r death t o mature leaves of t h e flowering p l a n t s a t Coweeta.

PLANT SPECIES MD L I F E FORM pH OF DROPLETS APPLIED

0 . 5

ERECHTIKS HlEMClFOLIA(L) RAF. HERBACEOUS W E D (N - 6)

P U U S STROBUS L. TREE ( N - 8 )

ROBIHIA PSEUDO-ACACIA La SHRUB TO TREE ( N - 6 )

ACER RUBRUH L. THE ( N = 0

1 . 0 1 . 5 2 .0 2.5

Figure 1. Average diameter i n mm of n e c r o t i c s p o t s on leaves subjected t o d r o p l e t s of 5 pH l e v e l s . (*) Spot diameters no t measured on needles, s e e t e x t f o r desc r ip t ion of damage.

Prioritization of Research on Air Quality Related Resources of the National Parks1

E. A. Howard, L. If. Boyd, W. M. Brock, D. W. Morse, S. S. Shin and K. L. steel-sabo2

The National Park Service (NPS) has the legal responsibility and authority to preserve and protect the resources of lands under its jurisdiction. Air pollution has been recognized as a significant threat to the parks and the 1977 Amendments to the Clean Air Act provided the Service the authority and responsibility to protect resources that are air quality related. The NPS Air Quality Office intends to conduct research programs to determine air pollution effects, to emphasize the use of sensitive receptors to detect effects, as well as to ensure that scientific evidence is readily a- vailable when NPS must make determinations of adverse effects. These efforts are subject to time and funding limitations and therefore guide- lines on setting research priorities are being developed.

The first step in establishing cause and effect relationships is to identify the pollutants that may. affect park resources (fig. 1). Pollutants from existing or planned sources may be identified by monitoring or estimated from permit requirements. If sources are not known, pollutants must be identified through some early warning process or on the basis of the potential development of regional natural resources. Existing sources of air pollutants that may affect the natural or cultural resources of park units must be ranked according to pollutant type, concentration, frequency, and duration of exposure of the resource. The rankine must also incorporate the estimated lead time before new pollutant sources begin operation. The identification and ranking of pollutant sources is necessary to economize the search for potential effects.

The identified pollutants are then used as a basis of comparison between the list of resources present on a park unit and the literature or current research information on resource susceptibility (fig. 1). The presence or absence of information on park resources must be incorporated into the setting of priorities. If these data are unavail- able, obtaining information on air quality related resources may be the most pressing need. If the resource inventories are available, then the information from these inventories is used in the comparison between resources present and those


2~hysical Scientist and Environmental Protec- tion Specialists, Denver Service Center, National Park Service, U.S. Department of Interior, Denver, Colorado.

that are susceptible to the effects of air pollution. The availability of current research information or literature on susceptibility must be similarly considered in establishing research priorities. Time constraints on recovering information or research results on air quality effects on natural ecosystems has prompted the development of a quick access annotated bibliography that uses a codin8 system based specifically on natural and cultural resources of NPS units. The bibliography has been used on several occasions to provide lists of references in support of litigation and testimony for hearings.

Setting priorities for research on air quality effects is altered by other influences and constraints (fig. 1). Funding and time limitations must be incorporated into the prioritization. In- sufficient funding may cause postponement of the highest priority research until these requirements can be integrated into the budget cycle. Time constraints also have considerable influence on priority setting. Substantive scientific data on air quality effects cannot be produced within the short time schedules of hearings or litigation. The timing of the budget cycle creates difficulty in obtaining sustained funding for long-term effects research. Political requirements at the Washington level may override the regional prioritization. The setting of priorities must be continually updated in conjunction with any change imposed by these influences or constraints.

POLLUTANT SOURCES RANKED ACCORDING TO IMMINENCE AND DAMAGE

POTENTIAL

LISTS OF RESOURCES LITERATURE AND FOR PARKS OF THE RESEARCH INFOFNA-

REGION TION ON RESOURCE SUSCEPTIBILITY

OTHER INFLUENCES OR CONSTRAINTS

PRIORITIZE RESEARCH NEEDS

Figure I--Considerations in setting research priorities for air quality related resources.

Estimation of Adverse Effects of Air Pollution on Danish Forests1

2I b Johnsen

E f f e c t s o f air p o l l u t i o n on Danish f o r e s t s do probably on ly occur under cond i t ions , where SO2, NO,, and/or 03 a r e p r e s e n t t o g e t h e r , t h u s r e s u l t - i ng in s y n e r g i s t i c a c t i o n on t h e l eaves . The maximum observed monthly average urban immission of NOx and SO2 a r e w i t h i n t h e range f o r syner- g i s t i c a c t i o n he reof . I n r u r a l r e g i o n s on ly t h e most s e n s i t i v e s p e c i e s may be a f f e c t e d by combi- n a t i o n s of S02, NOx and 03. Oxidants, and 0 3 i n p a r t i c u l a r , probably p l a y a s t r o n g e r r o l e in r u r a l a r e a s s i t u a t e d in t h e o u t e r pe r iphe ry of c i t i e s . Here l e v e l s exceeding t h e v a l u e s a t which e f f e c t s on r a t h e r s e n s i t i v e s p e c i e s occa- s i o n a l l y occur dur ing summer time. Unstable s u p e r a d i a b a t i c c o n d i t i o n s combined wi th h igh i n s o l a t i o n l e a d t o h i g h 03 formation r a t e s , and h igh ground l e v e l S O ~ / N O ~l e v e l s a r e observed when h igh s t a c k emiss ions a r e t r a n s p o r t e d t o t h e ground r e l a t i v e l y c l o s e t o t h e source .

F l u o r i d e s a r e on ly o f importance in ve ry re-s t r i c t e d a r e a s around b r i c k f a c t o r i e s , f e r t i l -i z e r i n d u s t r i e s e t c . , and of minor s i g n i f i c a n c e i n r e l a t i o n t o Danish f o r e s t r y .

Heavy me ta l s and hydrogen i o n s r e s u l t i n i n d i r e c t e f f e c t s a s adver se e f f e c t s on t h e n u t r i - e n t s t a t u s of t h e s o i l and t h e s o i l mic rob ia l p rocesses . The map shows a r e a s of Denmark (shaded a r e a s ) where t h e s o i l i s be l i eved t o be most v u l n e r a b l e t o a c i d p r e c i p i t a t i o n ; it is reasonab le t o b e l i e v e t h a t t h e s e a r e a s a r e co- i n c i d e n t wi th those expected t o b e most a f f e c t e d by i n c r e a s i n g heavy me ta l l e v e l s in top s o i l due t o a tmospher ic f a l l o u t . The most v u l n e r a b l e s o i l s a r e i n t e r m e d i a t e between t h e ve ry pod- z o l i s e d s o i l s of t h e a l l u v i a l p l a i n s (Western J u t l a n d ) and brown e a r t h s / c l a y i s h s o i l s w i t h high b u f f e r c a p a c i t y , and are c h a r a c t e r i z e d by t h e i r h igh c o n t e n t of moraine sand.

p r e s e n t e d a t t h e Symposium on E f f e c t s of A i r P o l l u t a n t s on Mediterranean and Temperate F o r e s t Ecosystems, June 22-27, 1980, R ive r s ide , C a l i f o r n i a , U.S.A.

Assoc ia t e P r o f e s s o r of P l a n t Ecology, U n i v e r s i t y of Copenhagen, Denmark.

Areas of woodland in Denmark r e l a t e d t o s p e c i e s . 1976. - ( Numbers in 1000 ha. ) -Fagus s i l v a t i c a - 75 Res. Quercus robur 25 Res. Fraxinus e x c e l s i o r 9 Sens. Acer psuedoplatanus 5 Res. Other deciduous spp. 24 Deciduous t o t a l 138

P i c e a a b i e s Sens. P icea s i t c h e n s i s 173 sens . Abies spp . 2 7 Sens. Pinus mugo 3 0 Res. Other con i fe rous spp. 46 Coniferous t o t a l 276

Woodland t o t a l 4 14

Immission l e v e l s and th resho ld v a l u e s

-F

O3 -3(ugm , d i u r n a l means)

Urban 40-100. 50-100 25-50 0.5-5 Rural 10-40 5-20 25-200 0.2-0.5

S ing le 250 500 100 1 100 5 0

Comb. 50 5 0 100 50

F igure I--Areas of Denmark (shaded a r e a s ) dominated by moraine sand d e p o s i t s .

1

Changes in Southern Wisconsin White Pine Stands Related to Air Pollution Sensitivity1

David F. ~ a r n o s k y ~

Fif teen eastern white pine (Pinus strobus L. ) sample p lo t s consist ing of a t o t a l of 1523 t r e e s were establ ished within a 13 km radius of t h e coal-burning 1054 MW Columbia Generating Stat ion, located 40 km north of Madison, Wisconsin. The sample p lo t s were establ ished i n 1971 and observed frequently during t h e growing season for 4 years and then annually a t t h e end of each growing season fo r t h e next 5 years. These p lo t s consisted of plantat ions with t r e e s having uniform ages within each plantat ion but with t r e e s ranging i n age from 10 t o 40 years old across t he 15 p lo ts . Baseline study during the 4 years 'before the plant began operation i n 1975 showed t h a t some 10 percent of t h e white pine t r e e s were sens i t ive i n some degree t o ambient a i r pol lut ion a s determined by the presence of needle t i p h r n and/or chlorot ic dwarf symptoms i n one or more years. The sens i t ive t r e e s occurred randomly i n the p lo ts .

The most common type of a i r pol lut ion symptom found i n t h e 'baseline study was tipburn consist ing of reddish brown dieback (0.1 t o 3 cm i n length) on f i r s t -year needle t i p s . The sever i ty of symp-toms varied from t r e e t o t r e e and from year t o year. The most severely affected t r e e s had stunted tops , short needles, poor needle re ten t ion , and were cha rac t e r i s t i c of an a i r pollution-induced syndrome ca l led t h e chlorot ic dwarf disease. However, ch loro t ic mottling of new needles, com-mon t o t h e chloro t ic dwarf disease., did not occur. Tipburn symptom development usual ly began during t h e ear ly summer when t h e new needles were elon-gating. Thus, t r e e s 'began showing symptoms i n ear ly t o mid June, and symptoms developed throughout t h e growing season.

Continuous a i r monitoring for su l fur dioxide ('SO2) and ozone to3), 'begun i n 1973 and continued t o t h e present time, revealed the common occurrence of SO2 and O-; concentrations i n t h e range of 0.4 t o 5.0 pphm fo r 1t o 3 hours during t h e summer months. Maximum one-hour averages recorded during t h e study were 11pphm SO2 and 13 pphm 03. These l eve l s , while low i n terms of a i r qual i ty standards, have "been shown t o be within the range of concentrations of these pol lu tants reported t o i n ju re genetical ly sens i t ive eastern white pine t r e e s i n control led fumigations.

p re sen ted a t the Symposium on Effects of A i r Pol lutants on Mediterranean and Temperate Forest Ecosystems, June 22-27, 2980, Riverside, California, U.S.A.

o ore st Geneticis t , New York Botanical Garden Cary Arboretum, Millbrook, N.Y.

During the 5 years since the power plant began operation, there have been no detectable d i f fer - ences i n t he occurrence o r sever i ty of symptoms. With only a few exceptions, t he same t r e e s have shown symptoms a f t e r t h e plant began operation a s before it s ta r ted . However, mortal i ty has reduced intermediate genotypes (those injured i n 1 or 2 years of t he 9 year study) by 4.7 percent and the sens i t ive genotypes (those injured i n 3 o r more years ) by 10.4 percent (Table 1). In comparison, only 2.0 percent of t h e to lerant t r e e s have died during the course of t he study. Most of t h e mor- t a l i t y of t h e sens i t ive genotypes was apparently due t o t h e i r being slower growing and thus unable t o compete fo r l i g h t , water, and nut r ien ts with t h e i r neighboring t r ees . As a r e s u l t , t h e white pine stands studied a re undergoing a gradual t ran- s i t i o n towards having air-pollut ion to l e ran t genotypes dominate.

Acknowledgments: This study was supported i n part by Grant R803971, Environmental Protection Agency, and by the Wisconsin Pi-iblic Service Corp., t he Madison Gas and Elec t r ic Co., t he W i s -consin Power and Light Co., and t h e College of Agricul tural and Life Sciences, University of Wisconsin.

Table I ~ M o r t a l i t y over a 9-year period of eas t -ern white pine t r e e s d i f fer ing i n a i r pol lu t ion sens i t i v i ty .

A i r Pollution sens i t iv i ty1 If Trees Died Mortal i ty

Tolerant Intermediate Sensitive

Totals :

l ~ h esens i t i v i ty rankings were based on t h e following: to lerant t r e e s did not have a i r - pollution-induced t ipburn symptoms during the course of t he study; intermediate t r e e s had symptoms for 1or 2 years; and sens i t ive t r e e s had symptoms for 3 or more years.

Effect of Os and Os + NO2on Growth of Tree Seedlings1

Lance W. ~ r e s s ~

Seedlings of 10 eastern forest tree species were exposed to 0.05, 0.10, or 0.15 pprn 0 and seedlings of 7 tree species were exposed to 0.10 pprn 0

3 and/or

0.10 pprn NO 2 in 6 hr/day exposures for 28 consecu-

tive days. The exposures were performed when the seedlings were 2-4wk-old in indoor exposure chambers of the CSTR design.

The Environmental Protection Agency has determined that the threshold for significant growth effects due to extended 0

3 exposures (7 hr daily

avg. for 2 no) for sensitxve vegetation is between 0.06 and 0.10 ppm. Three species in this study exhibited a threshold for significant suppressions in that range, while three other species exhibited a threshold for significant effects between 0.10 and 0.15 pprn (Table 1). However, two species exhibited a threshold for significant growth suppressions at or below 0.05 ppm. Those two species, loblolly pine and American sycamore, are probably the most important of the species tested to the forest industry. The significant effects at 0.05 pprn 0 were not

3accompanied by foliar injury.

In previous studies there have been indications that low concentrations of NO

2 might be stimulatory

to plant growth or alleviate 0 phytotoxicity.3Similar indications were noted for some of the tree species in this study. Two species (white ash and green ash) exhibited greater growth in the NO

2treatment than the control, and the only significant interactive effects were significantly less than additive (sweetgum and white ash).

Stimulations of growth at low 0 concentrations3

have been noted in the past, and some species exhibited growth stimulations in this study (Table 1). However, apparent growth stimulations appear to be dependent in part on the plant species and the parameter being evaluated.

The relationship that these data have to field conditions is not clear. This study demonstrates the potential for adverse effects at pollutant concentrations below the current NAAQS, but future research will have to determine whether such effects can be detected in the field.


'~esearch Associate of Plant Pathology, Vir- ginia Tech., Blacksburg, Va. Currently Assistant Ecologist, Argonne National Laboratory, Argonne, 111.

Table 1. Height growth and dry weight expressed as percent of control for seedlings of 10 tree species exposed to 0.05, 0.10, or 0.15 pprn 0 for 6 hr/day

3for 28 consecutive days.

Percent of control

Species

Loblolly Pine '100a looa lOOa (Pinus taeda L.) 82 b 85ab 90ab

73 b 79 b 72 bc 59 c 74 b 64 c

Pitch Pine lOOa lOOa lOOa rigida Mill. )(P.- 96ab

87 b 94a 83a

84ab 77ab

74 c 78a 68 b Virginia Pine lOOa lOOa lOOa

(Lvirginiana Mill. )

95a 89a

98a 97a

120a 93a

86a 87a 86a Sweet gum lOOa lOOa l60a (Liauidambar 109a 9lab 88ab styraciflua L.) 71 b 76ab 65 bc

55 b 60 b 52 c Sycamore lOOa lOOa lOOa (Platanus 104a 84a 57 b occidentalis L.) 73 b 43 b 27 b

79 b 36 b 19 b Green Ash lOOa lOOa lOOa

(Lpennsylvanica Marsh.)

98ab 76 bc

86ab 7lab

86a 75a

70 c 64 b 75a White Ash lOOa 100 b lOOab {Fraxinus 112a 125a 11 la americana L.) 91a 92 b 87 b

85a 83 b 81 b Willow Oak lOOa lOOa 1OOa (Quercus phellos 99a 99a 94a L.) 96a 92a 83a

81 b 89a 83a Sugar Maple 100 b lOOa 1 OOab

(& saccharum 95 b 88a 161a L.) 108a 90a 116ab

88 c 5 8 b 69 b Yellow Poplar 100 b 100 b 1 OOa (Liriodendron 160a 147a 133a tulipifera L.1 108 b 11lab 96a

Values for each column/species followed by the same letter are not different at p = 0.05 according to the ~uncan's New Multiple Range Test.

Impact of Oxidant Air Pollution on Ponderosa and Jeffrey Pine Cone Production1

Robert F.

Cone product ion by ponderosa and J e f f r e y p i n e t r e e s 10 cm o r more i n dbh was assessed on 19 p l o t s l o c a t e d i n t h e San Bernardino Mountains of sou the rn C a l i f o r n i a . These p l o t s were e s t ab -l i s h e d a long a g r a d i e n t o f oxidant a i r p o l l u t i o n . Each t r e e was r a t e d annua l ly us ing an oxidant a i r p o l l u t i o n index based upon t h e number o f yea r c l a s s e s o f need les r e t a i n e d , t h e i r c h l o r o t i c con-d i t i o n , t h e i r l eng th and t h e amount o f branch m o r t a l i t y p r e s e n t . Th i s r a t i n g was made independent ly i n t h e upper and lower crown f o r each t r e e . Other t r e e c h a r a c t e r i s t i c s , e . g . , age, dbh, h e i g h t , were a l s o measured once dur ing t h e course o f t h e 6 yea r s tudy. Cones were v i s u a l l y counted w i t h i n t h e crown o f each t r e e each September and October.

Although seve re oxidant a i r p o l l u t i o n i n j u r y was a s s o c i a t e d wi th reduced cone product ion, t h e most impor tant c o r r e l a t e wi th cone product ion was crown c l a s s , i . e . , t h e p o s i t i o n of a t r e e ' s crown r e l a t i v e t o t h o s e o f i t s neighbors . Dom-i n a n t t r e e s bo re t h e g r e a t e s t p ropor t ion o f cones. I n ponderosa p i n e dominant t r e e s com-p r i s e d 32 pe rcen t o f t h o s e p resen t on t h e 19 p l o t s bu t bo re 80 pe rcen t o f t h e cones. When t h e dominant and codominant crown c l a s s e s were com-bined t h e y comprised 58 pe rcen t of t h e ponderosa p i n e s bu t bo re 96 pe rcen t o f t h e cones. J e f f r e y p i n e showed a similar p a t t e r n . I n both J e f f r e y and ponderosa p i n e , cone product ion inc reased s i g n i f i c a n t l y wi th age (Ho:b=O: ponderosa p ine ; dominant: 7 = -92.33 + 1.86 (Age), r2 = 0.811**; codominant: 7 = -74.48 + 1.077 (Age), r2 = 0.4216*: J e f f r e y p ine ; dominant: 7 = 4.74 + 0.434 (Age), r2 = 0.765**; codominant: 7 = -8.28. + 0.243 (Age), r2 = 0.7456**).

Three p a t t e r n s were observed: (1) I n dominant J e f f r e y p i n e s 130 y e a r s o r o l d e r fewer s e v e r e l y i n j u r e d t r e e s bore cones t h a n un in ju red ones ( l b F ( 4 , 25) = 11.98, p < 0.05) ; (2) i n dominant ponderosa p i n e s 130 yea r s o r o l d e r s e v e r e l y in - ju red t r e e s bore fewer c o n e s / t r e e than un in ju red ones (2a x2

f4l = 21.07, p < 0.005) ; and (3) i n

both dominant and codominant J e f f r e y and ponderosa p i n e s s e v e r e l y i n j u r e d t r e e s bore s i g n i f i - c a n t l y fewer cone crops t h a n un in ju red ones dur-ing t h e 6 y e a r s of t h e s tudy ( x 2 ' s va lues < 0.01 i n 5 c a s e s , < 0.05 i n 1 c a s e ) .

-

' p resented a t t h e Symposium on E f f e c t s of A i r P o l l u t a n t s on Medi ter ranean and Temperate F o r e s t Ecosystems, June 22-27, 1980, R ive r s ide , C a l i f o r n i a , U.S.A.

a s s o c i a t e P ro fesso r of Entomology. Divis ion o f B io log ica l Con t ro l , Un ive r s i ty o f C a l i f o r n i a , R ive r s ide , C a l i f .

~ u c k ~

PONDEROSA PINE100

80z-6 0

w 3 4 0

a 0 2o w a Or z

C Â ¥ O 0-1 2 3 4 5

JEFFREY PINE

Â ¤ 80 M CK * 6 00 a a -I 0 U 4 0 0" Q_ 20

0 1 2 3 4 5

100 8 o PONDEROSA PINE

100 JEFFREY PINE

SLIGHT SEVERE

SMOG INDEX

Fig. 1. Propor t ion o f t r e e s producing cones i n a given smog c l a s s . (a) Ponderosa p ine ; (b) J e f f r e y p ine .

Fig . 2. Propor t ion o f c o n e s / t r e e borne by t r e e belonging t o a given smog c l a s s . (a) Ponder-o s a p ine; (b) J e f f r e y p ine .

-- - -

Lichens as Air Quality Monitors1

P.D. Lulman R .J. Fessende9S.A. McKinnon

The Athabasca t a r sands , l o c a t e d i n a remote region i n nor theas te rn Alber ta , i n t h e boreal f o r e s t region o f Canada, con ta in v a s t r e se rves (approx. 600 b i l l i o n b a r r e l s ) o f bitumen. A t t h e p resen t time t h e r e a r e only 2 companies opera t ing i n t h e region, producing s y n t h e t i c crude o i l from t h i s bitumen, Suncor Inc . and Syncrude Canada Ltd. Suncor, which began production i n 1967, emits approximately 200-300 tonnes of SO2 per day. Syncr-ide, which began production i n 1978 and which i s l o c a t e d only 10 km from Suncor, has been emi t t ing about 50-100 tonnes per day. I n t h e next 10-20 years t h e r e is a good p o s s i b i l i t y t h a t many more companies w i l l begin opera t ing i n t h e region a s we l l . This has l e a d t o a concern about t h e e f f e c t s o f changes i n a i r q u a l i t y on t h e vege ta t ion o f t h e region. S ince l i c h e n s a r e known t o be more s e n s i t i v e t o a i r p o l l u t a n t s , p a r t i c u l a r l y SO2, than most h igher vege ta t ion , i t was decided t o monitor changes i n l i c h e n growth a s an e a r l y warning of t h e impact o f p o l l u t a n t s on a l l components o f t h e vege ta t ion .

I n 1976, Syncrude Canada Ltd. i n s t a l l e d a network o f 56 permanent p l o t s i n a r a d i a t i n g p a t t e r n centered on t h e 2 opera t ions and a t d i s t ances o f up t o 47 km. Within each p l o t 20, 200 cm perma-nent a u a d r a t s con ta in ina t h a l l i o f Parmelia s u l - -cats o r Hypogymnia physodes, 2 abundant bark- -l i c h e n s , were e s t a b l i s h e d and photographed. Most of t h e &adra t s were e s t a b l i s h e d o n w h i t e spruce (P icea e lauca . a 1 thouah a smal le r number wire e s t a b l i s h e d on' balsam f i r (Abies balsamea) and whi te b i r c h (Be tu la p a p y r i f e r a ) . ? photographs-were p ro jec ted an s u r f a c e a r e a s of s e l e c t e d l i c h e n t h a l l i were measured. I n 1979, a l l o f t h e quadra t s i n 12 s e l e c t e d p l o t s were rephotographed and t h e photographs analyzed a s before . The ob- j e c t i v e s o f t h i s p a r t i a l resurvey were ( a ) t o measure changes i n t h e s u r f a c e a r e a o f t h a l l i of P. s u l c a t a , t h e dominant l i c h e n s p e c i e s , i n t h e 3 year per iod 1976-1979, ( b ) t o t e s t t h e s i g n i f i - cance o f these changes a s a func t ion o f d i s t ance

P r e s e n t e d a t t h e Symposium on E f f e c t s of A i r P o l l u t a n t s on Mediterranean and Temperate Fores t Ecosystems, June 22-27, 1980, Rivers ide , C a l i f o r n i a , U.S.A.

~ n v i r o n m e n t a l i s t , Calgary Power L td . , Calgary, Alber ta , Canada, formerly, Research Associa te , LGL Ltd . , Environmental Research Associa tes , Edmonton, Alber ta , Canada; Head, T e r r e s t r i a l Environment Sec t ion and Research A s s i s t a n t , Environmental A f f a i r s Dept., Syncrude Canada Ltd. , Edmonton, Alber ta , Canada.

and/or d i r e c t i o n from t h e emission sources , and ( c ) t o a s s e s s t h e p r a c t i c a b i l i t y of t h e l i c h e n network a s a long term monitoring system f o r d e t e c t i n g a i r q u a l i t y impacts on vege ta t ion .

There was a s i g n i f i c a n t i n c r e a s e i n p ro jec ted t h a l l u s s u r f a c e a r e a i n 6 p l o t s , a s i g n i f i c a n t decrease i n 2 p l o t s , and no s i g n i f i c a n t change i n 4 p l o t s . I n most cases t h e n e t change i n l i c h e n s u r f a c e a r e a dur ing t h e 3 year per iod was l e s s than 10%. However, wi thin-plot v a r i a b i l i t y was very l a r g e wi th c o e f f i c i e n t s of v a r i a t i o n common- l y between 300-400%. The changes i n p ro jec ted t h a l l u s s u r f a c e a r e a were s i g n i f i c a n t l y but weakly, r e l a t e d t o d i s t ance ; t h e t h a l l i c l o s e s t t o t h e emission sources i n c r e a s i n g more i n a r e a than those a t a d i s t ance , where i n f a c t t h e r e was a n e t decrease i n s u r f a c e a r e a on t h e average.- F i e l d observat ions i n d i c a t e d t h a t t h e r e was no r e l a t i o n s h i p between l i c h e n c o l o r and/or v igor and d i s t a n c e and/or d i r e c t i o n from t h e emission source . It was evident i n a comparison o f t h e 1976 and 1 9 7 9 p a i r e d photographs t h a t t h e r e was a s i g n i f i c a n t l o s s o f whole t h a l l i and p o r t i o n s o f t h a l l i from most of t h e quadrats . It was n o t unusual f o r 10-20% o f t h e t h a l l i p resen t i n 1976 t o be miss ing i n 1979. This appeared t o be p r i - mari ly r e l a t e d t o t h e n a t u r a l process o f bark e x f o l i a t i o n , although animal a c t i v i t y and i n s e c t g raz ing a r e a l s o suspected causes .

This technique i s capable o f d e t e c t i n g s i g n i - f i c a n t changes i n t h e s u r f a c e a r e a of P. s u l c a t a t h a l l i over a 3 year per iod, however, i t r e q u i r e s c a r e f u l s t andard iza t ion and a l a r g e number o f samples due t o t h e l a r g e wi thin-plot v a r i a b i l i t y i n t h i s c h a r a c t e r i s t i c . The high v a r i a b i l i t y is r e l a t e d t o t h e r a t h e r non-uniform arowth o f t h e P. s u l c a t a t h a l l u s a s wel l a s t h e v a r i e t y o f n a t u r a l processes causing l o s s e s o f p o r t i o n s o f t h e t h a l l u s . Perhaps o t h e r a t t r i b u t e s o f t h e t h a l l u s would make b e t t e r i n d i c e s o f growth ( o r l ack o f growth), however, none were i n v e s t i g a t e d . The ex tens ive l o s s e s of whole t h a l l i r a i s e ques-t i o n s about t h e permanence o f t h i s system and hence its value a s a long term monitoring system. Because t h e predominant reason f o r t h a l l u s l o s s is bark e x f o l i a t i o n , t h i s problem is very much r e l a t e d t o t r e e spec ies . Spruce a r e p a r t i c u l a r l y bad i n t h i s regard. There was very l i t t l e t h a l l - u s l o s s from b i rch o r f i r . Notwithstanding t h e above d i f f i c u l t i e s , i t was concluded t h a t t h e r e was no a i r q u a l i t y caused damage t o P. s u l c a t a between 1976 and 1979 a s i n f e r r e d from t h e rela-t ionsh ips between t h e n e t change i n t h a l l i sur- f a c e a r e a and d i s t a n c e and/or d i r e c t i o n from t h e e m i s s i o n sources . This conclusion i s supported by f i e l d observat ions of l i c h e n co lo r and v i g o r . -

Acid Precipitation in California and Some Ecological Effects1

John G. McColl and Mary K. Firestone 2

Wet and d r y p r e c i p i t a t i o n s were monitored on an event bas is i n 1978-9 a t Berkeley and San Jose ( p o l l u t i o n source areas i n the San Francisco Bay area) , Davis and Par1 i e r ( i n the cen t ra l a g r i c u l -t u r a l and rangelands) , Chal lenqe ( lower S ie r ran f o r e s t ) , and Tahoe C i t y (on t he shore o f Lake Tahoe) . Concentrations o f t h i r t e e n i o n i c species and s p e c i f i c conductance and volume were measured (Table 1 ) .

Ac id r a i n (pH < 5.6) was common a t a l l e i g h t s i t e s . Mean pH o f storms var ied from 4.24 a t San Jose t o 5.20 a t Davis, and the lowest pH o f any storm was 3.71 a t San Jose. The pr imary cause o f the a c i d i t y was probably the a i r p o l l u t a n t NOxy f o l l o w i n g i t s d i s s o l u t i o n i n wet p r e c i p i t a t i o n . NO? was t he anion most c l o s e l y co r re l a t ed w i t h H', and NO3 genera l l y occurred i n greater concen-t r a t i o n than SO$-.

Tota l d r y deposi t ions o f chemical cons t i tuen ts between rainstorms were o f the same order as t o t a l wet deposi t ions du r i ng storms. Dry deposi t ion dur inq summer would g r e a t l y increase the amounts recorded i n t h i s study which was conducted i n the wet season on ly . However, more research i s needed i n procedures f o r quan t i f y i ng d r y atmospheric deposi t ion.

' A1 though NOS concentrat ion (pg/1) and a c i d i t y (H" concentrat ion, p g / l ) of wet p r e c i p i t a t i o n were g rea tes t i n p o l l u t i o n source areas, t o t a l depo-s i t i o n (kg lha) o f NO3 and H+ were g rea tes t i n the non-urban recep to r areas o f Napa and Chal lenqe; t h i s was l a r g e l y a f unc t i on o f t he g rea te r p rec i - p i t a t i o n volumes a t these two s i t e s (Table 1 ) . Thus eco log ica l e f f e c t s may be expected i n the coast ranges and S ie r ras w i t h i n the genera l east- to-west "wash-out fan" o f wet p r e c i p i t a t i o n , as we l l as w i t h i n p o l l ut ion-source areas.

E f f ec t s o f these ac i d inpu ts t o C a l i f o r n i a s o i l s are c u r r e n t l y be ing assessed. These inves- t i g a t i o n s on s o i l e f fects inc lude research on both the inorganic phase o f s o i l and on the o rqan ic l - b i o l oq ica l components.

p r e s e n t e d a t t he Symposium on Effects of A i r Po l l u t an t s on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Rivers ide, Ca l i fo rn ia , U.S.A.

~ s s o c i a t e Professor of S o i l Science and Associate S p e c i a l i s t i n So i l Microbiology, respec t i ve ly , Un i ve r s i t y o f Ca l i f o rn i a , Berkeley, Ca l i f o rn i a , U.S.A.

Table 1 --Mean i o n i c concentrat ions o f wet p rec i p i -t a t i o n dur ing the study per iod i n 1978-9 (peqI1).

H' (Lab.) 22.1 6.8 10.9 13.0 38.0 7.9 6.3 14.6 ~ a + 36.9 11.8 15.3 12.8 33.1 14.5 15.1 22.0 K+ 1.5 0.6 1.4 2.1 1.5 1.1 1.1 1.4 ~ a 2 + 6.0 4.3 8.0 10.9 12.6 3.3 5.6 4.6 kJ2+ 9.6 1.7 3.6 7.0 9.7 3.8 5.7 5.3 ~e3+ 0.3 0.0 0.6 0.4 0.8 0.2 0.4 0.4 ~n2+ 0.1 0.0 0.1 0.6 3.1 0.1 0.1 0.1 cu2+ 0.1 0.1 0.1 0.2 0.3 0.1 0.2 0.7 zn2+ 0.3 0.1 0.2 0.2 0.6 0.1 0.1 0.2

NH; 8.0 4.1 40.0 11.9 19.1 9.7 35.5 12.1

NO;C l -

13.7 40.1

6.7 3.7

43.4 11.2

19.9 7.7

16.4 38.9

11.1 14.2

22.6 16.4 14.0 -23.1

SO:- 10.2 13.3 13.8 8.6 10.0 6.2 19.0 11 .7

Cond . (pmho/cm) pH (Lab.)

13.9 4.7

.3.9 5.2

17.4 4.7

10.6 4.9

16.2 4.4

6.4 5.1

9.6 5.2

10.7 4.8

Vol. (cm) 52.7 78.0 19.7 110.7 21.0 64.9 39.7 62.0

'BE Berkeley, TC Tahoe C i t y , KE Kearny ( f i e l d s t a t i o n a t par1 ier) , CH Challenge, SJ San Jose, HO Hop1 and, DA Davis , and NA Napa .

I n the inorganic s o i l -chemical s tud ies, s o i l s cover ing a wide range o f parent mate r ia l s and age are be ina t rea ted w i t h ac i d inputs , and the subsequent leaching pat terns o f ions ( i n c l ud i ng ~ l + 3 , H+, Nat, K+, Mg++, Ca^) are be ing determined.

The b i o l o g i c a l i n ves t i ga t i ons inc lude assessment o f poss ib le e f f e c t s on the s o i l - p l a n t n u t r i e n t system. The f i r s t 10-week p o t - t r i a l , using a Yolo se r ies s o i l and qrowina ba r l ey and c lover , has j u s t been completed. Prel iminary r e s u l t s i nd i ca te marked qrowth increases i n t r e a t - ments where the p lan ts were sprayed w i t h so lu t ions o f pH 2.0 and 3.0. This r e s u l t i s a t t r i b u t e d t o greater add i t i ons o f SO^- and NO?, and/or t o increased ava i l a b i l it y of s o i l n u t r i e n t s i n these lower-pH treatments. However, spo t t i ng o r leaves by ac i d d rop le ts a lso occurred i n the pH 2.0 treatments. N i t r i f i c a t i o n , deni t r i f i c a t i o n and n i t rogen f i x a t i o n a c t i v i t i e s are be ing measured i n both the rhizosphere and non-rhi zosphere s o i l .

Leaf Litter Decomposition in the Vicinity of a Zinc Refinery

Emmissions from a large zinc refinery in northern Ontario have been monitored for 10 years and an accumulation of zinc, copper, cadmium, arsenic and lead in the soil and vegetation surrounding the refinery complex has been documented. It was considered that decomposition of leaf litter as a part of the nutrient cycling process might be a convenient method to monitor the initial impact of these metals on the environment. This investigation was undertaken in the fall of 1977. Ny-lon mesh bags containing 10 q (oven-dry weight) of trembling aspen (Populus tremuloides) were set out at several locations around the refinery. Two sources of aspen foliage were utilized including foliage from a control location and contaminated foliage collected near the refinery. The exposure locations for the litter bags included three sites in close proximity to the refinery, (Plot A, B, C) one site 2.2 km from the refinery (Plot D) and one at a control location (80 km southwest of the refinery) (Plot E) .

The litter bags were allowed to over-winter and triplicate bags of each litter type were collected in May, June and August of 1978 and in May, July and August in 1979. Microarthropods were extracted from the bags in modified Tulgren funnels in the laboratory. The litter was then dried to determine the leaf weight loss and processed for chemical analysis.


plant Pathologist, Ministry of the Environment, 199 Larch Street, Sudbury, Ontario, P3E 5P9.

It was found that the rate of decomposition of the leaf litter was lower at sites nearest to the refinery and that contaminated foliage decomposed more slowly than control foliage at all sites. The microarthropod population was dominated by mites and springtails. The number of microarthropods was generally lower at the sites nearest to the refinery and was also lower in the litter baqs containing the contaminated foliage. The numbers of microarthropods appeared to fluc- tuate with moisture content of the litter. It was found that the concentrations of zinc, copper, cadmium, lead, arsenic, iron, sulphur and selenium in the leaf litter increased with time at the sites nearest to the zinc refinery but only a slight increase was noted at the more distant sites.

z PLOT NO - A' I-

60" CONTAMINATED LITTER ..*-*. m CONTROL LITTER -g 45-0 a

30-I-

;z 15-u n

NOV MAY JUN AUG MAY JUL AUG 1977 1978 1979

Figure 1. Pattern of decomposition of two types of leaf litter at two sites.

NOV MAY JUN AUG MAY JUL AUG 1977 1978 1979

Figure 2. Zinc accumulation is typical of metal accumulation in leaf litter.

Effects of Chronic Air Pollution Stress on Allocation of Photosynthate by White Pine

S. B. McLaughlin, R. K. McConathy, and D. Duvick2

A1 location of ^c-photosynthate by in s i tu branches of nine field-grown white pine trees was studied to determine whether distribution patterns differed between trees with apparent differences in sensi t iv i ty to a i r pollution stress. Three trees were selected in each of three sensit ivity classes which were differentiated on the basis of needle length, mottling, and duration of reten-tion. Previous studies (Mann e t a1. 1980) indicated that photosynthetic potential of foliage from trees in these three classes was not significantly different. Growth ring analysis of increment cores indicated that average annual increment of intermediate and sensitive trees was 98% and 47%, respectively, of that attained by the tolerant trees (7.8 mm y r - l ) over the past 18 years (Fig. 1 ). Sensitive trees showed a marked decline in annual growth during the past 10 years.

Foliage was labelled with ^COz four times during the growing season (June, July, August and November). Of the paired branches from each tree labelled on each date, one was harvested a f te r seven days and the remainder in November a t the end of the growing season. Photosynthate allocation patterns were compared by determining levels of f o l i a r retention and allocation to nearby branches. In June when elongating needles were approximately 50% of their final length, ^ C movement patterns in needles of three age classes (Fig. 2 ) indicated that contribution of ^C-photosynthate by old needles to new needle growth was occurring. This process was most rapid in tolerant trees which retained needles from two prior years and leas t significant in sensi t jve trees. Lower levels of incorporation of photosynthate into fo l i a r tissues occurred subsequently (X = 35% in June, 27% in July, and 5% in August a f t e r seven days). There were no dis t inct differences in f o l i a r retention of 1 4 C between the three sensi t iv i ty classes which could be associated w i t h the distribution of high levels of ozone (1h avg > 0.08 ppm) near the study area. ~ i g n if ican t 2-year-old needle retention on tolerant trees did not extend beyond July.

Presented a t the Symposium on Effects of Air Pollutants on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, California, U.S.A.

%search Staff llember, Research Associate, and Technician, respectively, Terrestrial Ecology Section, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A.

Generally higher levels of transfer of 14c from foliacje into branches were noted in the tolerant trees throughout the growin season. Higher levels of trans1 ocation of ^C-photosynthate out of 1 -year-01 d need1 es than current-year needles were also found for a l l sensit ivity classes. Enhanced current needle elongation (+25% sensi- t ive, +lo% intermediate, and +3% tolerant) compared to the previous year was associated with lower than average ozone levels and higher than average rainfall during the growing season. Data support the hypothesis that growth limitations in sensitive trees are a function of stress-induced reductions in photosynthate availabil i ty which result from reduced needle length (a function of decreased availabil i ty of carbohydrates for needle growth) and premature needle senes-cence. The resulting chronic decline of sensitive trees i s likely a result of interactions between a i r pollution stress and s i t e factors which may include secondary belowground pathogens.

Acknowledgments: Research sponsored by the U . S. Environmental Protection Agency under Inter- agency AgreementNo. 40-740-78 and the U.S. Department of Energy under Contract W-7405-eng-26 with Union Carbide Corporation.

Literature Cited

Mann, L. K., S. B. McLaughlin, and D. S. Shri ner. 1980. Seasonal physiological responses of white

pine under chronic a i r pollution stress. Env. Exp. Bot. (in press).

240 1

1960'62 'â‚ '66 '68 '70 '72 '74 '76 '78 1980 0 24

YEAR TIRE SINCE LABtLLIHt (m)

F i g u r e I ( l e f t ) - - A v e r a g e annual d iameter growth o f 3 t r e e s i n each o f 3 s e n s i t i v i t y c l asses .

F i g u r e 2 ( r i g h t ) - - D i s t r i b u t i o n o f ^C pho tosyn tha te i n f o l i a g e 0, I , and 7 days a f t e r ^cog uptake i n June.

168

Effects of SO2 and Ozone on Photosynthesis and Leaf Growth in Hybrid Poplar

Reginald D. Noble and

Keith F. ~ e n s e n 2

Plants i n the na tura l environment a re often si-multaneously exposed t o a combination of many atmospheric pol lu tan ts . Thus it is of i n t e r e s t t o as-ce r t a in the nature of in te rac t ion of these pollu- t a n t s on p lan t development and metabolism. Two pol- l u t an t s commonly encountered i n the atmosphere which a r e pa r t i cu l a r ly tox ic t o p l an t s and would appear t o o f f e r po t en t i a l f o r in te rac t ion a r e SO2 and 03.

METHODS

Plants of hybrid poplar #207 (Populus del toides Bartr. X P. trichocarpa Torr. & Gray) were grown from cut t ings under greenhouse conditions. Six week old p l an t s were fumigated i n control led environment chambers f o r 12 hours per day f o r 24 con-secut ive days. Four s e t s of p lan ts were used a s follows : Set 1-Controls (no fumigation) ; Set 2-Fu- migated with SO2 a t 0.5 ppm; Set 3-Fumigated with 03 a t 0.25 ppm; Set 4-Fumigated with SO2 a t 0.5 pprn p lus O3 a t 0.25 ppm. A t the end of the 24-day fumigation period, number of leaves per p l an t , l eaf f resh and dry weight and leaf area were determined. During the l a t e r s tages of the fumigation, photosyn- t h e s i s measurements were determined f o r s ing le a t - tached leaves from p lan t s fumigated with SO2 and those fumigated with s02+03. Photosynthetic mea-surements were made a t ambient C02 leve ls (300 pprn C02) and a t 1000 pprn C02.

RESULTS

Plants fumigated with SO2 showed l i t t l e v i s ib l e evidence of in jury while those fumigated with O3 o r a combination of the two began t o develop t i n y ne- c r o t i c spots a f t e r 5 t o 7 days of exposure. Soon a f t e r lower leaves began t o abscise and by 14 days extensive in jury was apparent on leaves below the 7th node from the apex. Both O3 and S02+03 t r ea t - ments caused a reduction i n the number of leaves per p lan t ; however, the r a t e of leaf formation was not affected f o r the four groups. The number of leaves per p l an t was lower i n the O3 treatment group than i n the S02+03 group, suggesting an antagonist ic

_L Presented a t the Symposium on Effects of A i r

Po l lu tan ts on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, Cal ifornia, U.S.A.

p r o f e s s o r of Biological Sciences, Bowling Green S t a t e University, Bowling Green, Ohio; Research Sc i en t i s t , U.S. Department of Agriculture, Forest Service, Delaware, Ohio.

relat ionship. Fumigation tended t o cause a decrease i n leaf area, l eaf dry weight and leaf f r e sh weight. This was increasingly t rue a s the dis tance from the p lan t apex increased. Pol lutant in te rac t ion evaluations revealed an antagonist ic re la t ionship between the responses t o O3 and SO2. Ozone which re-tarded growth most had l i t t l e o r no e f f e c t on a rea , dry o r f resh weight of leaves above node 5; however, these parameters were reduced by 25 t o 40 percent i n leaves fumigated with O3 a t node 9. These and re la ted observations demonstrate t h a t O3 r e t a rds growth of leaves i n t h i s p lan t only during the l a t - e r stages of t h e i r development. Ozone fumigated leaves with v i s i b l e in jury comparable t o those fumigated with both SO2 and O3 contained l e s s dry matter per un i t area.

Photosynthetic measurements on controls a s w e l l a s p lan ts fumigated with SO2 and S02+03 revealed

l i t t l e difference i n r a t e of C02 assimilat ion a t 300 pprn COT Even i n leaves of S02+03 fumigated p lan ts where v i s ib l e in jury was extensive the photosynthetic r a t e was reduced by only 10 t o 20 percent. When the C02 concentration was elevated t o 1000 pprn C02 photosynthetic r a t e s f o r cont ro ls , SO2 fumigated and S02+03 fumigated leaves (with no v i s i b l e injury) were elevated three-fold t o approximately 35 mg C02 dm'-hr-l. In leaves i n which in jury was apparent the photosynthetic r a t e increas-e s were usual ly l e s s than two-fold, t o a l eve l of approximately 18 mg C02 dm-2hr-1 (whether the injury was severe or barely discernable).

DISCUSSION

Ozone, and O3 i n combination with SO2 hasten senescence and promote r a t e of leaf drop t o the ex ten t t h a t control p lan ts have approximately 50 percent more leaves than fumigated ones. Fumiga-t i on with SO2 causes no such e f f ec t . Analysis of attached leaves f o r treatment e f f e c t s c l ea r ly shows an O3 e f f e c t but l i t t l e o r no SO2 e f f ec t . In com-bination these pol lu tan ts a t t h i s concentration in t e r ac t i n an antagonist ic manner i n r e l a t i on t o growth parameters.

Measurements of e f f e c t s of fumigation on photosynthesis indicate t h a t leaf photosynthesis i s not d ra s t i ca l l y reduced even i n the presence of con-siderable injury. It appears t h a t in jury tends t o reduce leaf po t en t i a l t o respond t o enhancement conditions more so than the a b i l i t y t o f i x C02 under conditions where C02 may be l imit ing.

Behavior of Airborne Fluorides in Soils'

Janina Polomski, Hannes Flfihler, and Peter laserâ

Accumulation of airborne f luor ides i n s o i l s i s sa id t o be a s ide e f f e c t of minor importance i f it i s compared w i t h the phytotoxici ty of man-made gaseous f luoride. When s o i l f luor ide was consid-ered i n t he pas t , F-uptake of p lan ts , l e a f in jury o r y i e ld reduction was of prime concern. Not much i s known about the f a t e of F-pollutants a f t e r being deposited onto the s o i l surface o r incorporated i n the p l an t l i t t e r layer . Our study aims a t providing experimental t oo l s and data fo r a b e t t e r understanding of long-termed e f f ec t s . The object ive is t o pin down the most s ign i f i can t , cont ro l l ing mechanisms of the F-mobility i n s o i l s .

Field experiments: In t he v i c in i ty of a 30000 t Aluminum smelter, b u i l t 1908, we ob-served t h a t F ac tua l ly accumulates i n the s o i l (Table). The s o i l s sampled a t various d is - tances d i f f e r i n many respect but a r e a l l calcareous. The F-contents do depend upon distance from the emission source.

distance from total F watersoluble F dissolved F F-content of Al-smelter 1 %-year old

(pg F per ml pine needles (km) 1 (pg F per gram soil) soil solution) ( P P ~

In s o i l s , f luor ide coexists i n many d i f f e r en t forms which makes the t o t a l F-content t o be a hardly in te rpre tab le s o i l cha rac t e r i s t i c s .

In a pine stand, located 1.8 km from the smelter t h e magnitude of the annual F-input and leaching losses were determined (kg F per y and ha) : 1-3 kg within dead p l an t mater ia l , 6-10 kg atmospheric washout, 40-80 kg adsorption and sedimentation. The leaching losses out of the root zone were estimated t o be some 80-100 kg.

Under pine canopies the F-contents i n the surface layer (humus) a r e systematical ly higher than i n the subsoi l (mineral horizon) whereas i n uncult ivated open land under grass cover f luor ide accumulates i n the subsoi l .

p r e s e n t e d a t the Symposium on Effec ts of A i r Po l lu tan ts on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, Cal ifornia, U.S.A.

~ g r o n o m i s t , s o i l phys ic i s t and chemist, respect ively, Swiss Forestry Research I n s t i t u t e , Binnensdorf, Switzerland.

Laboratory experiments : What controls the f luor ide t ranspor t i n s o i l s ? In case of a non-calcareous s o i l (pH 5.2) the amount of f luor ide adsorbed within a mixture of s o i l and NaF- solut ion being equi l ibra ted on a shaker (3340 \lg ~ / g ) s o i l equals approximately the F-adsorption i n the course of a percolat ion through a s o i l s l ab (Fig.)

Breakthrough-Curves of S i b Clay Soil with and without CaCO,

Cumulated Outflow [Number of Pore Voluminal

The close agreement between the two experiments ind ica tes t h a t adsorption and prec ip i ta - t i on a r e f a s t react ions as compared with the veloci ty of the percolat ing s o i l solut ion. In calcareous s o i l s , however, the exchange k ine t i c s between the l i qu id and so l id phase controls t he extent of accumulation and depletion. The exchange proceeds too slow t o keep up with the pace of the moving water. This explains the amazingly high F-mobility observed i n case of the F-contaminated calcareous s o i l s .

In the course of the percolat ion experiments the leachates from the s o i l columns contain appreciable amounts of so lubi l ized organic matter and aluminum. For a given s o i l type the leaching losses depend i n the f i r s t place upon the F-content of the i n f i l - t r a t i n g solut ion and fur ther upon s o i l type and the F-compounds used t o make up the percolat ing solut ion. Under f i e l d conditions with 8-10 ppm F i n the s o i l so lu t ion such phenomena may a l s o occur. A s i gn i f i can t amount of soluble organic material can be l o s t which may represent an energy subs t ra te shortage fo r the microorganisms, and furthermore t he Al-concentrations possibly reach phytotoxic leve ls . A t t h i s point the experimental evidence r a the r backs up questions than provides d e f i n i t e answers.

Multiple Pollutant Fumigations Under Near Ambient Environmental Conditions Using a Linear Gradient Technique1

2P.B. Reich, R.G. Amundson, and J.P. Lassoie

I n v e s t i g a t i o n s of t h e impact of atmospheric p o l l u t a n t s on p l a n t s normally involve a r t i f i c i a l - l y r a i s i n g t h e concen t ra t ion of c e r t a i n gases a- round s tudy p l a n t s . Such experiments t y p i c a l l y u t i l i z e enc losures which g r e a t l y modify o t h e r environmental f a c t o r s . Hence, t h e s e experiments may no t a c c u r a t e l y t e s t p l a n t responses under ambient cond i t ions . The development of open-top, f i e l d fumigat ion chambers (Mandl and o t h e r s 1973) and a new l i n e a r g rad ien t exposure system (Shinn and o t h e r s 1977) have been a t t empts t o s o l v e t h i s problem.

I n 1979 we cons t ruc ted a modified l i n e a r gra- d i e n t system and 6 open-top chambers. The gra- d i e n t system enabled t h e simultaneous exposure of numerous s tudy p l a n t s t o a concen t ra t ion g rad ien t of SO2 and 03. S ince t h e system does n o t use enc losures , p l a n t s a r e e a s i l y accessed and ex-pe r i ence near-ambient environmental cond i t ions . A p l o t of soybeans (Glycine s.v a r . Hark) i n I t h a c a , NY was used i n an a t tempt t o answer t h e fol lowing ques t ions .

1 ) Can t h e g rad ien t system be used t o expose p l a n t s i n t h e f i e l d t o c o n t r o l l e d l e v e l s of a i r p o l l u t a n t s wi thout s i g n i f i c a n t l y a l t e r i n g t h e i r environments?

2) Is p l a n t growth s i g n i f i c a n t l y d i f f e r e n t i n open-top chambers ve r sus i n a l i n e a r g rad ien t system?

3) What r educ t ions i n soybean seed y i e l d w i l l r e s u l t from exposure t o moderate l e v e l s of SO2 and 03 dur ing t h e seed maturat ion pe r iod?

During t h e seed maturat ion pe r iod , t h e p l a n t s were exposed t o SO2 and O3 f o r about 55 h over a 20-day per iod. On a l l occas ions , a l i n e a r con-c e n t r a t i o n g r a d i e n t was c r e a t e d by the system. Mean concen t ra t ions of SO2 and O3 a t t h e "high" end of t h e g r a d i e n t were 0.16 and 0.06 ppm, re-s p e c t i v e l y , whi l e ambient concen t ra t ions of both p o l l u t a n t s were about 0.02 ppm. Maximum hour ly means a t t h e "high" end of t h e g rad ien t were0.50 and 0.17 ppm SO2and 03, r e s p e c t i v e l y . By moni- t o r i n g t h e p l o t i n a g r i d des ign, we were a b l e t o account f o r t h e e f f e c t s of wind on p o l l u t a n t l e v e l s . I n t h e open-top chambers, p l a n t s were

p r e s e n t e d a t t h e Symposium on E f f e c t s of A i r P o l l u t a n t s on Mediterranean and Temperate Fores t Ecosystems, June 22-27, 1980, R ive r s ide , C a l i f o r n i a , U.S.A.

~ r a d u a t e s tuden t of Fores t Science, Cornel l Unive r s i ty , I t h a c a , NY; Post Doctoral Associa te , Boyce Thompson I n s t i t u t e , I t h a c a , NY; and A s s i s -t a n t P ro fessor of Fores t Science, Cornel l Unive r s i ty , I t h a c a , NY.

exposed t o 0.30, 0.10, and 0.02 (ambient) ppm SO2 f o r 72 h , over a 30-day pe r iod , dur ing t h e pod- f i l l i n g s t age .

Comparisons of t r ea tment s revealed t h a t t h e g rad ien t fumigations reduced t o t a l bean y i e l d pe r p l a n t and d ry mass per bean by a s much a s 39 and 14 pe rcen t , r e s p e c t i v e l y . I n t h e open-top cham-b e r s , t o t a l bean y i e l d per p l a n t and dry mass per bean were reduced by a s much a s 10 and 7 pe rcen t , r e s p e c t i v e l y . It i s of i n t e r e s t t o n o t e t h a t both t h e "high" and "medium" (mean SO2-0.09 ppm, mean 03-0.04 ppm) t reatments i n t h e g r a d i e n t system caused much g r e a t e r r educ t ions i n y i e l d than did t h e 0.30 ppm SO2 t reatment i n t h e open-top chamber. I n i n t e r p r e t i n g these d a t a , one must remember t h a t t h e p l a n t s i n t h e g rad ien t system did exper ience short-term peaks much h igher than t h e i r mean concen t ra t ion exposures.

I n any case , 03, a l though p resen t a t moderate- l y low l e v e l s , was (a lone o r s y n e r g i s t i c a l l y w i t h SO2) probably respons ib le f o r t h e g r e a t e s t r e -duc t ions i n seed s i z e and y i e l d .

I n open-topchambers, one can a c c u r a t e l y con-t r o l p o l l u t a n t l e v e l s . I n c o n t r a s t , t h e l i n e a r g rad ien t system al lows fumigat ions which va ry wi th time and wind, a s under ambient cond i t ions . The l i n e a r g rad ien t system proved t o be an e f -f e c t i v e means of fumigating p l a n t s w i t h m u l t i p l e p o l l u t a n t s under ambient environmental condi- t i o n s . Another modi f i ca t ion of t h e g rad ien t sys-tem i s c u r r e n t l y underway s o a s t o a l low f o r a n a l y s i s of t h e i n t e r a c t i o n s between SO2 and 03, and the e f f e c t s of such on va r ious hardwood t r e e seed l ings .

This s tudy was supported i n p a r t by t h e North- e a s t e r n F o r e s t Experiment S t a t i o n , F o r e s t Se rv ice , U.S. Department of Agr icu l tu re , through t h e Con- sor t ium f o r Environmental F o r e s t r y S tud ies (For-e s t Se rv ice Grant 23-169) and by t h e Cornel l Unive r s i ty A g r i c u l t u r a l Experiment S t a t i o n (McIntire-Stennis P r o j e c t NY(C)-147556).

LITERATURE CITED

Nandl, R.H. , L.H. Weinstein, D.C. McCune, and M. Keveny . 1973. A c y l i n d r i c a l , open-top chamber f o r t h e

exposure of p l a n t s t o a i r p o l l u t a n t s i n t h e f i e l d . J. Environ. Qual. 2:371-376.

Shinn, J . H . , B.R. Clegg, and I1.L. S t u a r t . 1977. A l inea r -g rad ien t chamber f o r exposing

f i e l d p l a n t s t o cons tan t l e v e l s of a i r p o l l u t a n t s . DOE-Preprint UCKL-80411.

Changes in Plant Communities with Distance from an SO2 Source

Paul R. scale2

Investigations were carried out to assess the effects on plant community composition of sulphur dioxide (SO2) emitted from an iron sintering plant in Wawa, Ontario, Canada. Diversity indices and the ordination techniques of Correspondence Analysis (C.A.) and Principal Component Analysis (P.C.A.) were used to discern community level changes. Of special interest were the subtle changes in areas noted to be only slightly affected by SO2 emissions. Over 60 upland birch stands were accessed along a north-easterly transect away from the source at distances of 12 to 55 km. Species specific data was collected on the tree, shrub and ground flora.

Changes in species composition are dramatic as the 30 year SO2 source is approached. The total percent cover of the dominant, predominantly boreal, ground flora species are shown in Figure 1. They reflect the complex pattern of species abundance which occurs along the transect. Characteristic is the transitory increase in abundance which occurs in most species. What is particularly evident is the ability of many species to take advantage of the increasing damage caused first to the tree canopy and subsequently to the shrub layer. This

Figure 1--Changes in ground flora species abundance with distance using a running average of percent cover: Am, Aster macrophyllus; An, Aralia nudicaulis; Df, Deschampsia flexuosa; Dl, Diervilla lonicera; Me, Maianthemum canadense; Va, Vaccinium angustifolium.


~raduate Student, Institute for Environmental Studies, University of Toronto, Toronto, Ontario, Canada.

occurs despite their own greater exposure to S O . The low-bush blueberry (Vaccinium angustifoliumL Ait.) for example, becomes very abundant at distances of 20 to 30 tan yet shows considerable SO2 damage in that area. The first substantial change in species abundance occurs at a distance of 40 km where beaked hazel (Corylus cornuta Marsh.) becomes very abundant before a very rapid decline. This undoubtedly contributes to the drop in the abundance of the large leaved aster (Aster macrophyllus L.) at that distance.

Dealing collectively with all species of a community to discern changes caused by a pollutant is, for theoretical reasons and from experience, a more satisfactory approach than changes in individual species abundance. Diversity indices have been used extensively for this purpose. However, the data from Wawa indicates that although diversity indices can deal with spatial/structural changes in the community, they do not adequately reflect the subtler changes in species composition. Ordination techniques, such as C.A. and P.C.A., are better suited for this purpose. For example, the Shannon-Weiner Diversity index has a transitory increase between 20 and 30 km before declining at distances below 20 km. In contrast, the first axis of C.A. using ground flora data shows a simple, linear change from 12 to 33 km (Figure 2). C.A. is most effective in reflecting overall trends whereas P.C.A. is particularly useful in discerning differences in stands of very similar composition. On the basis of P.C.A. using shrub density data, the separation of sites in intermediate areas from controls can be achieved. The boundary between the two groups in Figure 2 corresponds well with the line designated in 1973 and 1974 as separating areas which do and do not show visible leaf damage.

Figure 2~Distance vs Axis 1 of ground flora (percent cover) and shrub density (number of stems under 5 cm diameter at breast height) data using C.A. and P.C.A., respectively.

Lichens as Ecological Indicators of Photochemical Oxidant Air Pollution1

Lorene L. S i g a l and Thomas H. Nash 111~

From t h e l a t e 1960 's t o t h e p resen t , both t h e concentrat ion and dose of photochemical oxidant a i r p o l l u t a n t s (ozone and peroxyacetyl n i t r a t e o r PAN) have continued t o inc rease i n t h e mountainous a r e a s surrounding t h e Los Angeles Basin. Since 1972, a mul t i -d i sc ip l ina ry team of e c o l o g i s t s has monitored and analyzed t h e eco log ica l consequences of t h i s p o l l u t i o n i n t h e con i fe r f o r e s t ecosystem of t h e San Bernardino Mountains. Our l i c h e n study paral-l e l s and expands t h e parameters of t h e aforemen-t ioned s tudy and al lows a comparison of t h e r e l -a t i v e s e n s i t i v i t y of l i chens versus higher p l a n t s t o oxidants .

H i s t o r i c a l l y , l i chens have been demonstrated t o be s e n s i t i v e i n d i c a t o r s of a i r p o l l u t a n t s such a s s u l f u r dioxide. More recen t ly , t h e r e i s s t rong evidence t h a t l i c h e n s a r e a l s o s e n s i t i v e t o hy-drogen f l u o r i d e and heavy metals . The present s tudy documents f o r t h e f i r s t time t h a t l i c h e n s a r e a l s o s e n s i t i v e t o ozone and peroxyacetyl n i t r a t e .

F i e l d i n v e s t i g a t i o n s were conducted i n four mountain ranges surrounding t h e Los Angeles Basin. A f i f t h s i t e i n Cuyamaca Rancho S t a t e Park, e a s t of San Diego, was chosen a s t h e con t ro l a rea . Resul ts of sampling l i c h e n s on Quercus k e l l o g g i i Newb. and c o n i f e r s showed o v e r a l l spec ies r i chness decreased by 38 percent i n t h e highly impacted San Bernardino Mountains. Cover va lues f o r spec ies on Q. kellog-

decreased by 16 percen t ; f o r l i chens on con-i f e r s t h e decrease was 78 percent . The l a t t e r de-crease i s l a r g e due to t h e f a c t t h a t the "sen-s i t i v e " f r u t i c o s e l i c h e n spec ies a r e found mainly on c o n i f e r s . There was an inverse r e l a t i o n s h i p between t h e cover of l i chens a t b r e a s t height on c o n i f e r s and t h e oxidant dose es t imates a t s i t e s i n t h e San Bernardino Mountains ( f i g . 1 ) . A threshold is seen a t 180 ppm-hrs above which t h e l i chens a r e almost absent .

Fumigation s t u d i e s i n t h e l abora to ry provided a d e f i n i t i v e way of t e s t i n g t h e response of f i e l d s e n s i t i v e and f i e l d t o l e r a n t spec ies t o con t ro l l ed concen t ra t ions of ozone and PAN s i m i l a r t o those

p r e s e n t e d a t t h e Symposium on E f f e c t s of A i r P o l l u t a n t s on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Rivers ide, C a l i f o r n i a , U.S.A.

2 Research Associate , Oak Ridge National Lab-

o r a t o r y , Environmental Sciences Division, P.O. Box X, Oak Ridge, Tenn. 37830. Operated by Union Carbide Corporation under con t rac t W-7405-eng-26 with t h e U.S. Department of Energy; and Associate Professor of Ecology and Lichenology, Arizona S t a t e Univers i ty , Tempe, Ariz. 85281.

occurr ing i n t h e f i e l d . In ju ry was documented a s a s i g n i f i c a n t reduct ion i n g ross photosynthesis. Parmelia s u l c a t a Tayl. exh ib i ted g r e a t e r s e n s i t i v -i t y t o ozone and PAN than Hypogymnia enteromorpha (Ach.) Nyl. These r e s u l t s were c o n s i s t e n t wi th f i e l d observat ions .

A s a r e s u l t of c o l l e c t i o n s made by H. E . Hasse and t h e subsequent pub l ica t ion of h i s "Lichen F lora of Southern Cal i fornia" i n 1913, t h e present d i s t r i b u t i o n and v i t a l i t y of a number of l i c h e n s was compared t o t h e i r d i s t r i b u t i o n a t t h e t u r n of the century. There was a 50 percent decrease i n spec ies r ichness . I n add i t ion , marked morpho-l o g i c a l d e t e r i o r a t i o n was seen i n t h e t h a l l i of e x i s t i n g f o l o s e spec ies such a s Hypogymnia enter-omorpha. Forty-two percent of t h e t h a l l i c o l l e c t e d i n t h e San Bernardinos were bleached and 44 percent were convoluted i n c o n t r a s t t o no bleaching o r con-volut ion i n c o l l e c t i o n s made i n t h e Cuymacas. Thal lus dimensions were decreased by approximately 50 percent i n t h e San Bernardino c o l l e c t i o n s .

The importance of l i chen s t u d i e s l i e s i n t h e i r s e n s i t i v i t y t o a i r p o l l u t i o n and t h e i r p o t e n t i a l use a s bioind-icators . By monitoring t h e abundance and d i s t r i b u t i o n of s e n s i t i v e l i c h e n s , i t i s pos-s i b l e t o e s t i n a t e the magnitude of a i r po l lu t ion . use of l i chens i n t h i s mat ter may be f e a s i b l e no t only a s c u r r e n t l y appl ied i n nor thern Europe with s u l f u r dioxide a i r p o l l u t i o n , bu t a l s o over l a r g e geographical a r e a s impacted by photochemical oxidant a i r po l lu t ion .

Acknowledgment: This s tudy was supported by National Science Foundation Grant DEB-7610244 t o D r . Thomas H. Nash 111, Dept. of Botany/Micro-biology, Arizona S t a t e Univers i ty , Tempe, Arizona 85281.

- ORNL- DWG 80 - 7556 ESD f 3 0 0 I i r r 1

Figure 1--Percent l i n e a r cover a t b r e a s t he igh t of Le thar ia vulpina (1.) Hue and Hypop-ymnia enteromorpha (Ach.) Nyl. a s a func t ion of t h e oxidant dose es t imates (ppm - h r s . = t h e mean oxidant concentrat ion i n ppm mul t ip l i ed by t h e time of exposure) a t s i t e s i n t h e San Bernardino Mountains.

Y p 2 2 0 'nw

w in 180 0n

1 4 0

0 1 0 0

-CAMP PAIVIKA - -

BARTON FLATS -

SKY FOREST ,GREEN VALLEY CREEK - -

DEERLICK^ 1 O f 2 3 4 5 6 7 1. COVER OF LETHARIA VULPINA AND

HYPOGYMNIA ENTEROMORPHA

The Effects of Air Pollutants on Forest Ecosystems in S.R. Slovenia1

Marjan Solar

INTRODUCTORY DATA

Slovenia w i t h i t s surface o f 20,251 km2 represents 8% o f the t e r r i t o r y o f Yugoslavia (255,804 km2). It i s s i t ua ted i n the extreme northwestern p a r t o f the s t a t e between the Alps, the Pannonian p l a i n , the A d r i a t i c sea and the D ina r i c orographic system. Ha l f o f the surface i s covered by f o res t s (1,000,000 ha), 2/3 o f which a re p r i v a t e l y owned. The p o r t i o n o f con i f e r s amounts t o 56%, the average wood mass i s near l y 200 m3/ ha. The t o t a l increment per year i s 4,000,000 m3, the c u t t i n g 3,000,000 m3. Two-thirds o f the wood harvest possess a technica l value. The p o r t i o n o f f o r e s t r y w i t h i n the na t iona l income i s 4% and ind ica tes we l l the l eve l o f the i n d u s t r i a l development o f Slovenia.

Slovenia i s d iv ided up i n t o 15 f o r e s t management areas and each o f those i n t o the s o c i a l l y and p r i -v a t e l y owned sectors. The p r i n c i p l e s o f management are u n i f i e d . The bas ic p r i n c i p l e i s t o manage as much p rona tu ra l l y as poss ib le t o secure the perma-nency o f y i e l d and func t ions o f the f o res t . The f o r -es t se rv ice enjoys i n some places a 200-year t r a d i t i o n .

The study o f e f f e c t s o f a i r po l l u t an t s on the f o res t s goes back t o the year 1926, and systematic i n ves t i ga t i ons were s t a r t ed i n 1969.

OBJECTIVES OF INVESTIGATION

We wish t o determine the parameters, i n t e n s i t y and perspect ives o f the e f f e c t s o f a i r p o l l u t i o n on the f o res t s i n Slovenia, w i t h the aim t o secure r e l i a b l e foundat ions f o r the p lanning o f the indus-t r i a l development running p a r a l l e l l y w i t h the pre-serva t ion o f the mu l t i f unc t i ona l f o res t , f o r the r egu la t i on o f indemnit ies and the e labora t ion o f co r rec t normative concerning the maximum to l e rab l e concentrat ions va luable f o r t h i s s p e c i f i c f o r e s t area.

PRELIMINARY FOUNDATIONS REQUIRED

Ecology (geology, so i 1 s , phytocoenology , c l imate) as bases f o r the determinat ion o f f o r e s t ecosystems not stressed by emission, f o r e s t inventory as a ba-s i s f o r the determinat ion o f the normal management

P resen ted a t the Symposium on E f f ec t s o f A i r Po l l u t an t s on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, Ca l i f o rn i a , U.S.A.

~ r a d u a t e f o r e s t engineer, h igher research cooperator o f the I n s t i t u t e f o r the Forest and Wood Economy a t the Biotechnica 1 Facul ty i n L jub l jana , Yugoslavia.

s i t u a t i o n o f the f o res t s and a r e g i s t e r o f em i t t e r s .

METHODS OF ASSESSING THE EFFECTS OF POLLUTED AIR ON FORESTS

Symptomatics, chemical analyses, increment anal - yses, b io ind ica to rs , presence o f d i f f e r e n t l y aged needles, presence o f secondary pests, i n f r a c o l o r -aerophotographs.

SPECIFIC FEATURES OF THE TERRITORY OF SLOVENIA

Accentuated ~ o n f i g u r a t i o n ~ i n d u s t r yo f t e n located i n narrow va l leys , temperature invers ion, extremely h igh emission values (shocks), h igh p ropor t ion of suscept ib le con i fe rs , e rod i b l e s o i l s , predominancy o f SO2 and HF.

RESULTS OF INVESTIGATION

The t o t a l surface o f v i s i b l y damaged f o res t s i n S.R. Slovenia amounts t o 22,000 ha i .e . 2.2% o f the t o t a l f o r e s t area ( s i t u a t i o n i n 1977). The i n t e rna l d i v i s i o n o f damaged f o res t s i s the fo l low ing : Group A-the narrower emission area- the f o r e s t des-troyed and e x i s t e n s i a l l y threatened, o r surfaces under the impact o f c r i t i c a l emission cond i t i ons e n t a i l i n g the t o t a l des t r uc t i on o f a11 f o r e s t funct ions-dest ruct ion o f the f o r e s t ecosystem. Surface 4,000 ha. Group B-the wider emission area- forest under per-manent emission impact, ye t the ex is tence o f the f o r e s t i s not threatened, i t s funct ions are however reduced, o r surfaces under t o heavy emission con-d i t i o n s t o a l l ow a normal t h r i v i n g o f the f o res t . The emission causes an i n s t a b i l i t y o f f o r e s t eco-systems. Surface 16,000 ha. Group C-Periodic emission area-per iod ic occurrence o f damages, poss ib ly acute ones, but between i n d i v i d -ua l emission in f luences i n every case longer normal s i t u a t i o n s are in te rca la ted dur ing which the f o r -e s t can recover. Surface 2,000 ha.

Based on the chemical analyses o f Spruce needles as t o the increased content o f sulphur and f l u o r i d e , the surface o f f o res t s w i t h hidden i n j u r i e s i s es-t imated t o 25,000 ha. Survey and de ta i l ed maps of i n j u red f o r e s t have been made f o r a11 b igger emis-sions areas. On the basis o f r e l a t i v e res is tance capaci ty o f f o r e s t t rees and o f t h e i r p ropor t iona l presence i n the f o r e s t vegetat ion communities a ca tegor i za t ion o f f o res t s w i t h respect t o t h e i r s u s c e p t i b i l i t y t o a i r p o l l u t i o n has been c a r r i e d ou t .

The process o f a f u r t h e r improvement o f the emission damages i n the f o res t s observed dur ing the l a s t three years i s not l i k e l y t o proceed because o f the increase o f consumption o f coal possessing h igh contents o f combustible sulphur.

CONCLUSIONS

On the bas is o f i nves t iga t ions ca r r i ed ou t i n the t o t a l f o r e s t area o f Slovenia inf luenced by emission, o f knowledge concerning the ecology o f t h i s t e r r i t o r y and the p a r t i c u l a r i t i e s o f e f f e c t s o f the po l l u t ed a i r , we are ab le t o p red i c t exact-l y the fu tu re o f a c e r t a i n f o r e s t under c e r t a i n emission in f luence.

The s tandpoint o f f o res te r s i s always the f o l -lowing: Wherever the f o r e s t has been destroyed o r i s on the way o f des t ruc t ion , the a i r i s 10-c a l l y oo l l u t ed t o a r e l a t i v e l y c r i t i c a l extent . The a i r p o l l u t i o n i s too h igh a l so i n places where the f o r e s t i s hampered i n i t s development. Appealing t o the normatives f i x e d by law and concerning the maximum emission values allowed

means noth ing but t ha t the normatives are se t too h igh and t ha t the f o res te r s a re bound t o lower them.

o fThe Resolut ion issued on the xth ~ e e t i n ~ the IUFRO Group 2.09-Air Po l l u t i on , L jub l jana 1978 i s proposing the normatives insur ing the normal t h r i v i n g o f a11 k ind o f f o res t s on average and extreme s i t es . The values f o r SOi a re f o l l ow ing ( i n pg/m3/air) : 50 as year l y average, 100 as 24 h average, 150 as & h value, and f o r HF ( i n ug/m3/air) 0.3 as year l y average and 0.9 as & h value. For extreme s i t e s the normatives a re tw ice as sharp.

I f we compare the normatives f i x e d by Resolu-t i o n t o those f i x e d by law i n d i f f e r e n t coun t r ies we r e a l i s e the l a s t ones a re much too h igh.

Population Differences in Response to Sulfur Dioxide: a Physiological Analysis1

G. E. Taylor, Jr. and D. T. Tingey2

The environment e x e r t s a profound i n f l u e n c e on a p l a n t ' s a b i l i t y t o s u r v i v e and reproduce, and consequently v e g e t a t i o n i n a g iven a r e a w i l l possess a s e t of morphological and p h y s i o l o g i c a l t r a i t s t h a t enhance f i t n e s s . A t t h e l e v e l of popu la t ions , t h e s e s i t e - s p e c i f i c a t t r i b u t e s a r i s e through e i t h e r a modi f i ca t ion of t h e phenotype (phenotypic p l a s t i c i t y ) o r a change i n t h e gene pool (ecogenet ic a d a p t a t i o n ) . Both responses a r e common s t r a t e g i e s among n a t u r a l popu la t ions exper- i enc ing d i s p a r a t e c l i m a t i c , edaphic and b i o t i c s t r e s s e s . It is hypothes ized t h a t e l eva ted l e v e l s of a tmospher ic p o l l u t a n t s have e l i c i t e d i n a com-p a r a b l e manner a v a r i e t y of t r a i t s t h a t enhance s u r v i v a l and rep roduc t ion i n n a t i v e p l a n t s inhab- i t i n g p o l l u t i o n - s t r e s s e d a r e a s .

One example of ecogene t i c a d a p t a t i o n i n response t o a i r p o l l u t i o n i s t h e evo lu t ion of s u l f u r d i o x i d e r e s i s t a n c e w i t h i n popu la t ions of Geranium carol in ianum, a n herbaceous w i n t e r annual common i n d i s t u r b e d h a b i t a t s i n t h e Sou theas te rn United S t a t e s . I n comparison wi th t h e i r counter- p a r t s from p o l l u t i o n - f r e e r eg ions , popu la t ions sampled from a r e a s exper i enc ing v a r i a b l e SO2 s t r e s s f o r 3 1 y e a r s were c o n s i s t e n t l y more r e s i s -t a n t t o SO2 under c o n t r o l l e d exposure cond i t ions . This i n f r a s p e c i f i c v a r i a t i o n i s g e n e t i c a l l y de te r - mined and q u a n t i t a t i v e l y c o n t r o l l e d . P l a n t s of c o n t r a s t i n g SO2 r e s i s t a n c e were used t o invest!+ g a t e t h e p h y s i o l o g i c a l b a s i s of t h i s adap ta t ion . I n d i v i d u a l p l a n t s were p laced i n a whole-plant gaseous exchange system i n which concurrent s t e a d y s t a t e measures of l e a f r e s i s t a n c e t o water vapor e f f l u x and SO2 i n f l u x were monitored i n t h e da rk and l i g h t a t p o l l u t a n t concen t ra t ions of 0.4, 0.6, and 0.8 u l 1-l. For r e s i s t a n t and s e n s i t i v e p l a n t s a t each concen t ra t ion , e s t i m a t e s of t o t a l SO2 f l u x (pg c m 2 h r l ) a s a f u n c t i o n of l e a f r e s i s t a n c e t o Hz0 e f f l u x were modeled us ing l i n e a r r e g r e s s i o n techniques . From e s t i m a t i o n procedures , t o t a l f l u x was p a r t i t i o n e d i n t o l e a f s u r f a c e and i n t e r n a l f r a c t i o n s .

T o t a l SO2 f l u x v a r i e d a s a f u n c t i o n of l e a f r e s i s t a n c e and d i d n o t d i f f e r among r e s i s t a n t and s e n s i t i v e p l a n t s a t 0.4 and 0.6 u l l 1SOz. Con-v e r s e l y , a t t h e h i g h e s t concen t ra t ion t o t a l SO2 f l u x was n o t t h e same f o r t h e 2 p l a n t groups a s a consequence of d i s p a r a t e s l o p e parameters. I r r e -s p e c t i v e of concen t ra t ion t h e l e a f s u r f a c e and i n t e r i o r were major s i n k s f o r SO2 (Fig. 1 ) . Each f r a c t i o n inc reased l i n e a r l y wi th concen t ra t ion ,

'presented a t t h e Symposium on E f f e c t s of A i r P o l l u t a n t s on Medi ter ranean and Temperate F o r e s t Ecosystems, June 22-27, 1980, R ive r s ide , C a l i f o r n i a , U.S.A.

2 ~ o s t d o c t o r a l Assoc ia t e and P l a n t P h y s i o l o g i s t , T e r r e s t r i a l Divis ion, U.S. Environmental Protec- t i o n Agency-Corvallis Environmental Research Laboratory, C o r v a l l i s , Oregon, U.S.A.

however t h e r a t i o of i n t e r n a l t o t o t a l f l u x decreased s t e a d i l y . The a b s o l u t e v a l u e s f o r i n t e r - n a l SO2 f l u x were s t r i k i n g l y s i m i l a r f o r bo th p l a n t groups a t each concen t ra t ion . Therefore , i n s p i t e of t h e v a r i a t i o n i n t o t a l SO2 f l u x t o t h e p l a n t , t h e r a t e of SO2 absorbed i n t o t h e l e a f i n t e r i o r was equ iva len t f o r r e s i s t a n t and s e n s i - t i v e p l a n t s . S ince l e a f r e s i s t a n c e t o wa te r vapor e f f l u x i s t h e same f o r a l l p l a n t s i n both ambient and S02-polluted atmospheres, o v e r t p lant - to-plant d i f f e r e n c e s i n t h e i r response t o SO2 r e f l e c t d i s p a r a t e i n t e r n a l biochemical p rocesses a f f e c t i n g po l lu t a f i t t o x i c i t y , p e r t u r b a t i o n o r c e l l u l a r r e p a i r .

The f a c t t h a t p l a n t d i f f e r e n c e s i n response t o SO2 a r e g e n e t i c a l l y c o n t r o l l e d and n o t a r e s u l t of p o l l u t a n t exc lus ion i s r e l e v a n t t o an unders tanding of t h e r a p i d evo lu t ion of popula t ion r e s i s t a n c e i n

-G. carolinianum. This s p e c i e s i s an annual t h a t t h r i v e s f o r s i x months a s a win te r r o s e t t e du r ing which new l e a f growth i s minimal and y e t t r ans -p i r a t i o n remains a c t i v e . This h a b i t coupled w i t h t h e p l a n t ' s i n a b i l i t y t o t r a c k and exclude e l e - va ted l e v e l s of SO2 may p red i spose t h i s s p e c i e s t o accumulate more SO2 d e r i v a t i v e s than o t h e r co-occurring s p e c i e s t h a t a r e e i t h e r more ephemeral o r capable of avoiding SO2 uptake i n c r e a s i n g s tomata1 r e s i s t a n c e . These s p e c i e s ' a t t r i b u t e s may e x p l a i n t h e c o n s i s t e n t f i e l d obse rva t ions t h a t show c. carolinianum t o be a s e n s i t i v e b i o l o g i c a l i n d i c a t o r of e l eva ted SO2 l e v e l s .

Acknowledgments: Research sponsored by t h e Nat ional Academy of Sciences-National Research Council through a Pos tdoc to ra l Research Associa te- s h i p t o t h e s e n i o r author . Senior au thor acknow- l edges suppor t f o r manuscript p r e p a r a t i o n under Contrac t W-7405-eng-26 by t h e Department of Energy wi th Union Carbide Corporation, a t Oak Ridge Nat ional Laboratory, Oak Ridge, Tennessee.

6.0 , t r

- RESISTANT PLANTS SENSITIVE PLANTS-

SULFUR DIOXIDE CONCENTRATION ( p l I"')

Figure I--Absolute v a l u e s f o r t o t a l , s u r f a c e and i n t e r n a l l e a f f l u x of SO2 a s a func t ion of p o l l u t a n t concen t ra t ion i n r e s i s t a n t and' s e n s i t i v e p l a n t s .

1

Ozone Injury to Pines in the Southern Sierra Nevada of California1

2Det lev R. Vogler and John Pronos

The Forest Serv ice began eva lua t ing the impact o f ozone on S ie r r a Nevada f o res t s i n 1974. Eval-ua t ion e f f o r t s were expanded and i n t e n s i f i e d i n 1977, and s ince then t he pr imary methods o f assessment have included, (1) moni tor ing ambient ozone levels, and (2) r a t i n g i n j u r y t o p ine f o l - iage i n permanent t r end p l o t s .

A i r p o l l u t i o n i n j u r y t o commercial p ine stands located between 4000 and 8000 f e e t e l eva t i on occurs q u i t e un i fo rm ly along most o f the southern S ie r ra Nevada f r o n t range adjacent t o the San Joaquin Va l ley and up i n t o t he major r i v e r dra in- ages. Symptoms a re n o t conf ined t o loca l i zed areas downwind from major p o l l u t a n t sources. Rather, ozone i s c a r r i e d down the e n t i r e San Joaqu in A i r Basin and eastward i n t o t he Sier ra . MetropoI i t a n areas c o n t r i b u t i n g t o the ozone dose inc Iude Stockton, Modesto, Merced, Fresno, Visa1 i a Bakersf ie ld , and perhaps even Sacramento and the San Francisco Bay Area.

OZONE MONITORING

F i ve fo res ted loca t ions i n t he southern S ie r r a were moni+ored f o r season-long ozone dosages between 1977 and 1979. One s i t e -- Whitaker Fores t -- was monitored cont inuously dur ing t h i s 3-year per iod. The s i t e s ranged i n e l eva t i on from 5400 f e e t t o 7540 feet , and a l l were a t l e a s t 50 m i l es from suspected met ropo l i tan sources o f a i r p o l l u t i o n .

Ozone l eve l s a t each s i t e exceeded both t h e Federal (0.12 ppm) and S ta te (0.10 ppm) Standards each year they were recorded. Based on t he num-ber o f hours exceeding t he Standards, 1977 was t h e wors t year f o r ozone, wh i l e l e ve l s dec l ined s t e a d i l y i n 1978 and 1979. During t he summer o f each year d a i l y peak ozone values commonly ranged between 0.10 ppm and 0.14 ppm. These values can be compared t o those i n t he San Bernardino Moun- t a i n s o f southern Ca l i f o rn i a , where maximum d a i l y ozone leve ls f requen t l y range from 0.20 t o 0.33 ppm, and where i n j u r y t o p ine f o res t s i s correspondingly more severe.

TREND PLOTS

Presented a t t he Symposium on E f f ec t s o f A i r Po l l u t an t s on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, Ca l i f o rn i a , U.S.A.

'plant Patho loq is ts , P a c i f i c Southwest Region, Fores t Service, Ui s . ~epartment of Agr icu ture, San Francisco, Ca I i f o r nia.

Trend p l o t data were co I lected f o r t h ree con- secut ive years beginning i n 1977. I n 1977 and 1978 ozone i n j u r y r a t i n g s o f p l o t s scat tered throughout a sampl ing area o f over 1 m i I l ion acres ranged between no i n j u r y and moderate i n j u r y . A l -though t he ma jo r i t y o f 1978 p l o t s showed more ox i - dant symptoms than 1977 p lo ts , t he re was no sta- t i s t i c a l l y s i g n i f i c a n t t rend evident. The change between 1977 and 1979, however, was more dramatic. Nineteen o f 27 p l o t s evaluated i n 1979 showed add i t i ona l i n j u r y over 1977 levels, and seven o f these p l o t d i f fe rences were s t a t i s t i c a l l y s i g n i f i - can t (P = 0.05). I n 1979, f o r t h e f i r s t time, several p l o t s f e l I i n t o t he severe i n j u r y category. The t r ees i n these p l o t s averaged 2 years o f needle r e t en t i on w i t h ozone symptoms on Z-year- ol'd needles.

Th is obvious increase i n i n j u r y was n o t expected because measured ozone l eve l s i n 1979 were genera l l y lower than i n e i t h e r 1978 o r 1977. Considerable phys io log ica l s t ress from a 2-year drought (1976-1977) could account f o r p a r t o f t he observed increase i n f o l i a r i n j u r y . One v i s i b l e response o f pines t o t he drought was a dramatic decrease i n needle re tent ion, which tended t o produce more severe ozone i n j u r y ra t ings . Future recovery o f t r ees from drought stress, i n t h e form o f increased needle re tent ion, may r e s u l t i n a r e l a t i v e reduct ion o f measureable a i r p o l l u t i o n i n j u r y dur ing t h e nex t few years.

CONCLUSIONS

The ove ra l l leve l o f forest-wide i n j u r y i n t h e south'ern S ie r ra Nevada can be termed s l ight, w i t h some loca l populat ions o f suscep t ib le pines showing moderate o r worse i n j u r y . Unexpectedly h igh amounts o f i n j u r y detected i n c e r t a i n areas i n 1979 placed some p l o t s i n t o t h e severe category. I t i s p resen t l y unc lear whether t h i s i s a perma-nent t rend of increasing impact, o r j u s t a short-term r e s u l t o f drought stress.

With on ly 3 years o f moni tor ing data, t rends i n annual ozone dose a re d i f f i c u l t t o assess. Ozone leve ls seemed t o decrease s l i g h t l y each year between 1977 and 1979, even though v i s i b l e i n j u r y t o pines increased. Measured va r i a t i ons i n seasonal ozone dose may be associated more w i t h weather pa t te rns than w i t h decreased pol Iu tan ts a t t he source. Maximum d a i l y ozone values i n t h e S ie r r a s t i l l remain about 1/2 o r less of those occur r ing i n southern Ca l i f o rn i a . As ozone con- t i nues t o be t ranspor ted i n t o t he western slopes o f t he S ie r r a Nevada, s e n s i t i v e pines w i l I con-t i n u e t o show add i t i ona l i n j u r y and w i l I s low ly decl lne.

Modifications of Chemical Contents of Precipitation by Passage through Oak Forests1

George T. Weaver and Jon D. ones^

Bulk precipitation monitored within oak forests in the Ozark Physiographic Province in Illinois was strongly acidic (pH<4.5) throughout most of

. 1978. Exceptions occurred during late summer and early autumn when pH rose to 5.8. This pattern with similar pH values reoccurred during the autumn and winter of 1979-80 and differs from seasonal trends usually reported from the northeastern United States where periods of greatest and least acidity are summer and winter, respectively. During the 1979-80 period, the highest concentrations of ~ 0 ~ ~ - occurred durin~ autumn, and on an equivalence basis, exceeded H concentrations by a factor of 10. Concentrations of ~ a , ~ g and, K+ were also high during autumn. It is hypothesized that considerable neutralization of strong acids occurred in the atmosphere due to the presence of airborne dust which normally exists during autumn.

Additional neutralization occurred as precipitation passed through the forest canopy, especial-ly during autumnal leaf senescence. At this time canopy drip pH exceeded bulk precipitation

2qH by up to 0.7 units. The concentrations of Ca , in canopy drip increased Mg2, K', 804 and ~ 0 ~ ~ -

markedly compared to bulk precipitation, particu-larly during autumn. During the winter, canopy drip pH decreased to values as low as 3.8 and differed little from bulk precipitation pH. In 1978, 68 percent of the precipitation reaching the forest floor as canopy drip was acidic (pH<5.6). The removal of nutrient ions from the canopy also de-


~ssociate Professor of Forestry, Southern Illinois University, Carbondale, 111.; Forestry Aide, Baruch Science Institute, Georgetown, S.C.

creased during winter. In the spring of 1980 maximum bulk precipitation pH was 6.6 but passage through the canopy caused a decrease in pH as great as 0.8 units. Soluble organic compounds, apparently leached from some oaks, were present in sufficient quantities to impart a dark stain to canopy drip during this period and may be associated with the reversal in H exchange in the canopy.

The concentrations of ions in soil water fonn- ed three distinct patterns relative to concentrations in bulk precipitation and canopy drip. Hy-drogen ion concentration was decreased markedly by passage through these ecosystems and the quantity remaining in soil water was only about 10 percent as great as in bulk preci itation. The concentrations of four ions - So:-, m3-, ca2+- and W2+- increased as water passed through these ecosystems. The levels of these ions in soil wa-ter were as great as 37 times and 9 times the levels in bulk precipitation and canopy drip, respectively, although major differences occurred among seasons and between ions. The contents of K+ and ~ 0 ~ - in bulk precipitation also were increased by up to 25 times by passage through the forest canopy. However, concentrations of these particular ions either decreased or remained similar to concentrations in canopy drip after passage through the soil.

Between October 1979 and April 1980, ca2+ and sod2-were the predominant ions (equivalence basis) associated with meteorologic and hydrologic processes in these ecosystems. The importance of Ca 2+ in these ecosystems was anticipated since it is selectively accumulated by some species of oaks in these forests. It is also apparent that elevated levels of H' are being deposited in association with in these ecosystems, but the impacts remain undetermined.

2

Seasonal Variation of Inorganic and Organic Sulfur in Coniferous Needles Intensified by SO2 Pollution '

2Karl Friedrich Wentzel und SUnther Gasch

Method:-Needles front 50 - 70 year o ld Norway spruce from 1. gardens and

parks of Wiesbaden town (s l ight damage), 2. and Wiesbaden forests

(no v is ib le injury) were used as bioindicators fo r $0.-uptake.

I n octobre we picked 0.5, 1.5 and 2.5 year old needles, i n m y

we picked 1, 2 and 3 year o ld needles fro@the tops of the sam

trees. Inorganic and organic sulfur was determined according t o

JSger und Steubing (1970).

Results:-1. Air pol lut ion measuremnt 1976 - 1979. Datas i n microgram

SO per cbw air. 11= annual average, 12 = 95 percentile of

30 win. values:

Zone II 1 2

Industr ia l Area 120 - 140 400 - 500

Town 7 0 - 90 200-300

Forests <50 <120

2. Total sulfur content increases with needle age as shown i n

fig. 1 :Map of Wiesoaden/FRG

Fig. 2. I n town the S contents d the needles are 100 - 200 ppm

higher than those froa the forests.

3. The inorganic f ract ion of a l l needle samples surmounts the

organic fraction. The difference i s greater i n autumn than i n

spring and more apparent i n town than i n the forests.

4. The va l id i ty of using coniferous needles as indicator of a i r

pol lut ion effects i s best when octobre datas of inorganic S are

used.

5. Organic sul fur content decreases during the vegetation period

while the inorganic f ract ion increases. During winter time the

opposite occurs (Fig. 3). From th i s i t i s suggested that i n

spring t i ne a part of the organic sulfur d m n d i s covered by

remvinq the inorganic amount, which par t ia l l y i s of air-borne

origin.

1 Presented a t the In ternat iona l Symposium on E f f ec t s o f A i r Po l lu tan ts on Mediterranean and Temperate Forese Ecosystems, June 22-27, 1980, Riverside, Ca l i fo rn ia , U.S.A.

2 Forest Ecologist and chemist, respect ively, Hessische Landesanstalt f u r Umwelt, Wiesbaden, West Germany

500. - Wiesbaden Town

-- - -- Wiesbaden Forest 300

0.5 1.0 1.5 2.0 25 3D Needle4 e

Fig. 2 :Sulfur content ( p p of dr. wt.) i n spruce needles from Wiesbaden town (means of 39 tree samples) and forests (mans of 16 tree samples).

Oclobre- deltas

. . . . May -deltas

1 A Decrease of inoro.S

I -Wiesbaden Town 39 trees in casualorder

Fig. 3 :Seasonal alteration of inorganic and organic S i n spruce needles frw Wiesbaden town (mans of 6 semi-annual needle sets).

Sulfur Dioxide and Oxidant Effects on Californian Coastal Sage Scrub1

W.E. Westman and K.P. pres tonz

Two f i e l d s t u d i e s have r e l a t e d o x i d a n t and f r e e upwind s t t e s . I n j u r y t o i n d i v i d u a l S a l v i a s u l f u r d i o x i d e p o l l u t i o n t o a d e t e r i o r a t i o n i n shrubs and changes i n community s t r u c t u r e and t h e s t r u c t u r e and f u n c t i o n o f southern C a l i f o r - f l o r i s t i c compos i t ion were recorded. Stomata1 n i a ' s drought-deciduous shrublands ( coas ta l sage r e s i s t a n c e was found t o be s i g n i f i c a n t l y lower scrub) . I n a s tudy o f 67 s i t e s (0.63ha) f rom on t h e p o l l u t e d s i t e s w i t h a concomitant 35 pe r - San Franc isco t o E l Rosar io (Ba ja C a l i f o r n i a ) , cen t i nc rease i n mean t r a n s p i r a t i o n r a t e s o f da ta were c o l l e c t e d on spec ies cover and 43 Sa lv ia . F lower ing capac i t y o f S a l v i a , measured h a b i t a t v a r i a b l e s d e s c r i b i n g topography, s o i 1 , by the number o f f l o w e r whor l s p e r f l o w e r sp i ke , c l i m a t e , v e g e t a t i o n s t r u c t u r e , age s i n c e f i r e , was a l s o s i g n i f i c a n t l y reduced. S i g n i f i c a n t g r a z i n g i n t e n s i t y , and a i r p o l l u t i o n o f s i t e s . decreases i n t h e h e i g h t / w i d t h r a t i o o f S a l v i a The v a r i a b l e which showed t h e h i g h e s t s i q n i f i - were hypothes ized t o be caused by s u l f i t e - c a n t c o r r e l a t i o n w i t h pe rcen t f o l i a r cover o f mediated d e s t r u c t i o n o f i n d o l e a c e t i c a c i d (Yang n a t i v e species was t h e mean annual o x i d a n t and Saleh, 1973) and p o s s i b l e i n h i b i t i o n o f concen t ra t i on (r=-.58, P<.001). E l e v a t i o n and a p i c a l dominance. S i g n i f i c a n t reduc t i ons i n mean maximum temperature o f t h e warmest month photos.ynthetica11.y a c t i v e t i s s u e o f S a l v i a a l s o showed h i g h l y s i g n i f i c a n t c o r r e l a t i o n s r e s u l t e d f rom increased d e f o l i a t i o n and r e d u c t i o n ( r=- .52) . The p a r t i a l c o r r e l a t i o n c o e f f i c i e n t s i n l e a f s i z e assoc ia ted w i t h SO2 s t r e s s . The o f ox idan ts w i t h pe rcen t cover remained h i g h evidence i n d i c a t e s t h a t these f a c t o r s decreased when c o v a r i a t i o n s w i t h e l e v a t i o n , mean maximum t h e shrubs ' a b i l i t y t o compete w i t h t h e more r-temperature o f t h e warmest month ,and d i s t a n c e s e l e c t e d annuals. As such, t h e number o f f rom t h e coas t were e x t r a c t e d ( r= - .41,- .35,- .42 species, p r i m a r i l y annuals, increased cons ider - r e s p e c t i v e l y ) . The i n t e r r e l a t i o n s h i p s o f these a b l y i n t h e most o o l l u t e d s i t e s (X=27 v. 7=18.on v a r i a b l e s were i n v e s t i g a t e d f u r t h e r by means o f c o n t r o l s i t e s ) . These SO2 -assoc ia ted changes pa th a n a l y s i s . A p a t h model (ch i -square probab i - i n community s t r u c t u r e and f l o r i s t i c compos i t ion l i t y = .87) r e l a t e d environmental f a c t o r s t o a suggest t h a t r e t r o g r e s s i o n i s occu r r i ng , caus ing r e d u c t i o n i n t h e pe rcen t cover o f n a t i v e species. t h e 26-year o l d s tand t o resemble a 7-year o l d The p a t h model suggested t h a t o t h e r f a c t o r s co r - p o s t - f i r e sera1 's tage. Resu l ts a re r e p o r t e d r e 1 a ted w i t h dec l in i ng cover were a c t i n g p r i m a r i - more f u l l y i n Pres ton (1 980). Laboratory s t u d i e s 1y through t h e i r i n f l u e n c e on o x i d a n t concentra- a re i n progress t o assess s e n s i t i v i t y o f sage t i o n i n p r e d i c t i n g t h e d e c l i n e i n cover o f n a t i v e scrub species t o SO2 i n j u r y . scrub species.

I n c r e a s i n g concen t ra t i ons o f ox idan ts were a l s o assoc ia ted w i t h a d e c l i n e i n species r i c h -ness (r=-.23; P<.05) and i nc rease i n e q u i t a - b i l i t y ( W h i t t a k e r ' s Ec index; r=.24; P<.05). D i v e r s i t y i n f l o r i s t i c a l l y s i m i l a r s i t e s o f h i g h and low annual o x i d a n t concen t ra t i ons was compared. H i g h l y p o l 1 u ted s i t e s have fewer species p e r abundance c l a s s and a l ower t o t a l species r i chness ("7=18 v . T=29 a t l e s s p o l l u t e d s i t e s ) . Concent ra t ion of dominance increases i n t h e more p o l l u t e d s i t e s . Major r e s u l t s have been r e p o r t e d i n Wes tman ( 1 979).

I n a second f i e l d study, t h e e f f e c t s o f s u l f u r Preston, K.P.d i o x i d e emissions (up t o 0.13 ppm f o r a p e r i o d o f 1980. E f f e c t s o f s u l f u r d i o x i d e p o l l u t i o n on25 y e a r s ) from an o i l r e f i n e r y were s t u d i e d near coas ta l sage scrub. M.A. Thesis. DepartmentSanta Maria, on t h e r u r a l c e n t r a l coas t o f C a l i - o f Geography, U n i v e r s i t y o f C a l i f o r n i a , Losf o r n i a . Stands o f coas ta l sage scrub w i t h b l a c k Angel es . sage (Sal v i a me1 1 if e r a ) downwind o f t h e r e f i n e r y were compared w i t h stands i n r e l a t i v e l y p o l l u t i o n - Westman, W.E.

1979. Ox idant e f f e c t s on C a l i f o r n i a n coas ta l sage scrub. Science 205:1001-1003.

Â¥'Â¥presenta t t h e Symposium on E f f e c t s o f A i r Whi t t a k e r , R.H. P o l l u t a n t s on Medi terranean and Temperate Fo res t 1972. E v o l u t i o n and measurement o f species Ecosystems, June 22-27, 1980, R ive rs ide , d i v e r s i t y . Taxon 21 :213-251. C a l i f o r n i a , U.S.A.

Yang, S.F. and S.A. Saleh. ' ~ s s o c i a t e P ro fesso r o f Geography and graduate 1973. D e s t r u c t i o n o f i ndo le -3 -ace t i c a c i d

s tudent , r e s p e c t i v e l y , U n i v e r s i t y o f C a l i f o r n i a , d u r i n g t h e ae rob ic o x i d a t i o n o f s u l fit e . Los Angeles, Cal i f o r n i a. Phytochemistry 12:1463-1466.

Miller, Paul R., technical coordinator. I

1980. Proceedings of the symposium on effects of air pollutants on Mediterranean and temperate forest ecosystems, June 22-27, 1980, Riverside, California, I U.S.A. Gen. Tech. Rep. PSW-43,256 p. Pacific Southwest Forest and Range Exp. 1 Stn., Forest Sew., U.S. Dep. Agric., Berkeley, Calif. 1

I II

These proceedings papers and poster summaries discuss the influence of air pollution on

relationships; interactions of producers, consumers, and decomposers under pollutant II terrestrial and related aquatic ecosystems. They describe single species-single pollutant

I

I stress; and the use of ecological systems models for interpreting and predicting pollutant Ieffects.

I Retrieval Terms: air pollution injury, acidic precipitation, pollutant stress, terrestrial I I habitats, species-pollutant relationship. mathematical models. I

Synthesis Session

Opening Remarks and Summary of

Walter E. westman*

Abs t rac t : I n t h e opening remarks by W. E. Westman, t h r e e ma- j o r ques t ions were r a i s e d : (1) How can r e s i l i e n c e of ecosys-tems t o a i r p o l l u t i o n damage be p red ic t ed? Models cons t ruc ted from key physiognomic, phys io log ica l o r l i f e - h i s t o r y a t t r i b u t e s of dominants w i t h i n a community could form t h e b a s i s Of a n a u t - e c o l o g i c a l approach. Using a syneco log ica l approach, a t l e a s t fou r d i s t i n c t components can be recognized ( e l a s t i c i t y , ampli- t ude , h y s t e r e s i s , m a l l e a b i l i t y ) which r e f l e c t d i f f e r e n t a s p e c t s of t h e recovery process . These could be measured i n t h e f i e l d o r de r ived from modeling, us ing such community-level a t t r i - b u t e s a s components of d i v e r s i t y , f o l i a r cove r , and s i m i l a r - i t i e s i n composit ion. ( 2 ) What i n d i c a t o r s of e f f e c t s of a i r p o l l u t i o n on ecosystem n u t r i e n t c y c l i n g a r e most r e l i a b l e ? Observing changes i n t h e mine ra l composit ion of f r e s h l i t t e r - f a l l du r ing peak l i t t e r f a l l pe r iods may be p r e f e r a b l e t o mea- s u r i n g f o l i a r n u t r i e n t concen t ra t ions i n r e l a t i v e l y smal l sam-p l e s of f o r e s t s p e c i e s . ( 3 ) What i s t h e r o l e of c u l t u r a l va lues i n a i r p o l l u t i o n r e sea rch? What a r e t h e s o c i a l r e s p o n s i b i l i t i e s of s c i e n t i s t s , and how can they be d ischarged? Examples were g iven of t h e r o l e of c u l t u r a l va lues and pe rcep t ions i n t h e con- duc t of a i r p o l l u t i o n r e s e a r c h and i n t e r p r e t a t i o n of i t s r e -s u l t s . S c i e n t i s t s may a s s i s t decision-makers i n i n t e r p r e t i n g t h e s i g n i f i c a n c e of r e s u l t s of a i r p o l l u t i o n e f f e c t s on f o r e s t s by i l l u s t r a t i n g t h e e x t e r n a l c o s t s genera ted i n t h e economy by l o s s of ecosystem f u n c t i o n s , a s w e l l a s s t r u c t u r e , due t o a i r p o l l u t i o n damage. I n t h e open d i s c u s s i o n t h a t fo l lowed, p a r t i - c i p a n t s d i scussed t h e u s e of a i r p o l l u t i o n s imula t ion models i n making d e c i s i o n s about land use. Modelers i n d i c a t e d t h a t r e -pa ramete r i za t ion of e x i s t i n g v e g e t a t i o n models t o l o c a l condi- t i o n s could provide an e f f i c i e n t means of app ly ing e x i s t i n g mo- d e l s t o l o c a l s i t i n g d e c i s i o n s . F i e l d b i o l o g i s t s and managers expressed some r e s e r v a t i o n s about t h e l e v e l of p r e c i s i o n t o be achieved from such a procedure. Some a t t r i b u t e s of t h e f o r e s t ecosystem which a r e most i n d i c a t i v e of p o l l u t i o n s t r e s s , and hence most u s e f u l l y incorpora ted i n such models, were d e t a i l e d , i n c l u d i n g physiognomic a t t r i b u t e s , v i s i b l e f o l i a r i n j u r y symptoms, wood growth r a t e s and l i c h e n composit ion. A t l e a s t n i n e a r e a s i n which r e s e a r c h i s needed on t h e e f f e c t s of a i r pol - l u t a n t s on f o r e s t s were suggested .

p r e s e n t e d at t h e Symposium on E f f e c t s of A i r OPENING REMARKS

P o l l u t a n t s on Medi ter ranean and Temperate F o r e s t Ecosystems, June 22-27, 1980, R ive r s ide , The purpose of t h i s f i n a l d i s c u s s i o n s e s s i o n

C a l i f o r n i a , U.S.A. i s t o i d e n t i f y ecosystem-level concepts p e r t i - nen t t o t h e s tudy of a i r p o l l u t a n t e f f e c t s of

^ ~ s s o c i a t e P ro fesso r of Geography, Un ive r s i ty f o r e s t s , and t o provide a n oppor tun i ty f o r d i s - of C a l i f o r n i a , Los Angeles, C a l i f o r n i a cuss ion between p a r t i c i p a n t s a t t h e Symposium

regarding key ques t ions a r i s i n g from t h e Sympo- sium proceedings. To a s s i s t i n t h i s e f f o r t , Symposium s e s s i o n chairmen ( P a t r i c k Coyne, Joe McBride, Samuel McLaughlin, J r . , Joseph Shinn, William H. Smith, and David Tingey) w i l l s e rve a s a panel t o f i e l d d i scuss ion ques t ions from t h e audience. I have been asked t o open t h e s e s s i o n with some "provocative" quest ions r e -garding ecosystem-level s t u d i e s of a i r p o l l u t i o n e f f e c t s , a r i s i n g from t h e Symposium presenta- t i o n s and f i e l d t r i p s of t h e l a s t four days. I cannot guarantee t h a t anything more than my g a r i s h red t i e w i l l be provocat ive , but I would l i k e t o pose t h r e e ques t ions f o r your consider- a t i o n .

HOW CAN RESILIENCE O F ECOSYSTEMS TO A I R POLLUTION DAMAGE BE PREDICTED?

The term " r e s i l i e n c e " has been used t o r e f e r t o t h e degree, manner and pace of r e s t o r a t i o n of i n i t i a l s t r u c t u r e and func t ion i n an ecosystem a f t e r d i s tu rbance (Westman, 1978). Most of t h e papers i n t h i s Symposium have discussed n o t r e s i l i e n c e , bu t what has been termed eco-system " i n e r t i a " (Orians, 1975; Westman, 1978). ' I n e r t i a " is t h e a b i l i t y of an ecosystem t o r e - s i s t displacement i n s t r u c t u r e o r func t ion when sub jec ted t o a d i s t u r b i n g fo rce . I n t h e case of a i r p o l l u t i o n , i n e r t i a can be measured by d e t e r - mining t h e minimum concen t ra t ion of a p o l l u t a n t a t which impact t o an ecosystem occurs . We have cons ide rab le information on t h e l e v e l s of chronic o r a c u t e a i r p o l l u t i o n t h a t w i l l i n i t i a t e i n - jury t o i n d i v i d u a l spec ies , and a l e s s ample body of evidence regard ing t h e l e v e l s of pol- l u t a n t s necessary t o i n i t i a t e community-level changes.

Ecosystem models, once e f f e c t i v e l y v a l i d a t e d , can p o t e n t i a l l y s e r v e a s t o o l s f o r t h e p red ic - t i o n of r e s i l i e n c e . Since it is imprac t i ca l t o model a l l f e a t u r e s of an ecosystem, however, mod-e l e r s need t o know which a t t r i b u t e s of a spec ies make t h e organism most vu lnerab le t o p o l l u t i o n i n j u r y . Thus, t o be of maximum a s s i s t a n c e t o modelers, exper imenta l i s t s need t o determine which physiognomic and/or phys io log ica l a t t r i - butes of a spec ies ( o r spec ies a s s o c i a t i o n ) a r e most u s e f u l i n d i c a t o r s of t h e i n e r t i a and r e - s i l i e n c e of spec ies . Noble and S l a t y e r (1976) and Grime (1979) have made progress r e c e n t l y i n i d e n t i f y i n g a t t r i b u t e s of spec ies which may be u s e f u l i n p r e d i c t i n g t h e i r a b i l i t y t o r e - co lon ize burned o r c lea red s i t e s .

We might be a b l e t o speed t h e bu i ld ing of e f f i c i e n t models of a i r p o l l u t i o n e f f e c t s on ecosystems by examining spec ies f o r those a t - t r i b u t e s which a r e most vu lnerab le t o p o l l u t i o n damage, o r which enhance recovery fol lowing damage. During t h i s symposium, we heard t h a t li-chens and mosses tend t o be more vulnerable t o a i r p o l l u t a n t s because of t h e i r l a c k of waxy c u t i c l e s . Beyond t h i s , it would be u s e f u l t o know more about t h e r e l a t i v e e f f e c t s of such l e a f a t t r i b u t e s a s mesophylly, sc le rophyl ly and succulence i n providing r e s i s t a n c e t o ab-

s o r p t i o n of p o l l u t a n t s . What i s t h e p r e d i c t i v e value of phenological a t t r i b u t e s , such a s ever-greenness vs. deciduousness, o r l i f e - c y c l e a t t r i b u t e s such a s annual vs. pe renn ia l reproduc t ive cyc les? What a r e t h e e f f e c t s of crown-sprou t ing a b i l i t y , o r l ack t h e r e o f , on eco-system recovery following a i r p o l l u t i o n damage?

These quest ions form p a r t of what might be c a l l e d the"autecologica1 approach" t o ecosystem r e s i l i e n c e , s i n c e they focus on spec ies a t t r i b u t e s which, when incorporated i n a n ecosystem model, can be used t o syn thes ize key p r o p e r t i e s of ecosystems.

It is poss ib le , however, t h a t progress may be made more quickly by a t tempting genera l i za - t i o n s of ecosystem r e s i l i e n c e by s tudying community-level processes of recovery i n p a r t i c - u l a r biomes. I n order t o organize a s tudy of community-level response t o d i s tu rbance it i s u s e f u l t o recognize a t l e a s t four d i s t i n c t components of r e s i l i e n c e (Westman, 1978) :

The r a p i d i t y of r e s t o r a t i o n of a s t a b l e s t a t e following dis turbance. To use t h e analogy of a meta l c o i l , e l a s t i c i t y of t h e c o i l i s t h e time requ i red t o s p r i n g back t o i n i t i a l s i z e a f t e r s t r e t c h i n g a c e r t a i n d i s t ance .

Amplitude

The zone from which t h e ecosystem w i l l r e -t u r n t o a s t a b l e s t a t e . By analogy, amplitude is t h e d i s t a n c e beyond which a c o i l cannot be s t r e t c h e d without being permanently deformed.

Hys te res i s

The degree t o which t h e path of r e s t o r a -t i o n (success ion) i s a n exac t r e v e r s a l of t h e path of degradat ion ( r e t r o g r e s s i o n ) . By ana-logy, h y s t e r e s i s is the degree t o which t h e reg ion temporar i ly occupied by a c o i l i n sp r ing ing back d i f f e r s from t h e reg ion through which t h e c o i l moved when i n i t i a l l y s t r e t c h e d .

M a l l e a b i l i t y

The degree t o which t h e s t a b l e s t a t e es tab- l i s h e d a f t e r d i s tu rbance d i f f e r s from t h e o r i g i n a l s teady s t a t e . S imi la r ly , m a l l e a b i l - i t y is the degree t o which a s t r e t c h e d c o i l remains s t r e t c h e d a f t e r t h e deforming f o r c e is removed.

These components of r e s i l i e n c e a r e s u b j e c t t o measurement (Westman, 1978). I n t h e case of t h e s tudy of oxidant e f f e c t s on p ines i n t h e San Bernardino Mountains, i n e r t i a was d e t e r -mined by observing t h e l e v e l s of oxidants a t which damage t o pines f i r s t appeared. Amp-l i t u d e might be e s t a b l i s h e d by i d e n t i f y i n g t h e sample p l o t s , among the s e v e r a l used, a t which pines a r e no longer rep lac ing themselves ( i f these a r e taken t o be climax spec ies f o r t h e reg ion) , and determining t h e lowest mean and

peak concentrations of oxidants a t which t h i s threshhold e f f e c t i s observed. E l a s t i c i t y could be measured a s t he time necessary f o r recovery of such a s i t e once po l lu tan t s t r e s s i s r e -moved. Mal leab i l i ty could be measured, using a percentage s i m i l a r i t y index, by comparing the community composition of t he new steady s t a t e which was establ ished following pol lu t ion s t r e s s t o t he pre-s t ress composition. I n ex-amining hys t e r e s i s , one would ask whether the f i r s t species t o disappear from the ecosystem were t he l a s t t o re turn , using, f o r example, a rank co r r e l a t i on coe f f i c i en t .

It i s obvious t h a t i n many s i t ua t i ons re -covery cannot be observed because the chronic s t r e s s continues (as is the case i n the San Bernardino Mountains). Further , the pos t - s t ress recovery period may be on t he order of centur-i e s , i n which case ecosystem models using autec-o logica l approaches must be r e l i e d upon fo r quicker predict ions. Nevertheless, there a r e s i t u a t i o n s i n which a po l lu t ing source has been removed o r reduced, and recovery can be observed. I n these s i t ua t i ons , compilation of t he components of r e s i l i e n c e fo r a pa r t i cu l a r p lan t formation may a id us i n general iz ing about the impact of new pol lu t ion sources on a s ye t un-impacted a r ea s of vegetat ion of s imi la r type.

Thus i n considering the pred ic t ion of eco-system r e s i l i e n c e , we may be wise t o focus both on s ens i t i ve a t t r i b u t e s of individual species or species assoc ia t ions , and of community-level changes i n species r ichness , -composition, fo-l i a r cover, e t c . which can form the bases f o r observing community-level components of r e s i l -ience.

WHAT INDICATORS OF EFFECTS OF A I R POLLUTION ON ECOSYSTEM NUTRIENT CYCLING ARE MOST RELIABLE?

The nu t r i en t budget of an e n t i r e ecosystem represen ts one ecosystem l eve l a t t r i b u t e t h a t can revea l much about growth-potential and func-t ion ing a t the supraorganismal leve l . Deter-mining the n u t r i e n t budget f o r even a small por- t i on of t he landscape, however, is a very cos t -l y and time-consuming process. Hence some speakers (Bruce Wiersma and K. W. Brown, Allen Legge) described at tempts t o determine e f f e c t s of a i r po l lu tan ts on nu t r i en t cycl ing by mea-surement of concentrat ions of mineral elements i n fo l iage , a s poss ib le bioindicators of pol-lution-induced ecosystem-level damage. Paul Zinke described some of t he many ecosystem compartments which must be considered i n concep- t ua l i z ing ecosystem n u t r i e n t cycl ing.

I would l i k e t o i s sue a caut ion aga ins t t he use of f o l i a r nu t r i en t concentrat ions, i n the absence of considerable context , f o r the study of po l lu t ion s t r e s s . So i l s c i e n t i s t s have long recognized t h a t f o l i a r nu t r i en t concentrations a r e dependent on s o i l nu t r i en t concentrations, and have used t he fo l iage analyses a s ind ica tors of "available" concentrations of t he elements i n the s o i l i n a number of instances. Thus i t

becomes very important f o r t he a i r po l lu t ion researcher t o charac te r ize s o i l he te rogene i t ies i n h i s or her study. Secondly, eco logis t s know t h a t f o l i a r nu t r i en t concentrations vary temp-o ra l l y a s the leaf passes from ear ly growth s tages t o senescence and leaf f a l l . The changes a r e due t o t he change i n t i s s u e and c e l l u l a r component r a t i o s with age, t o t he changing r a - t i o of photosynthate t o mineral elements, and t o withdrawal of more mobile nu t r i en t s i n t o stems before leaf f a l l . Thus t he harvest of leaves a t d i f f e r en t times of year makes nu-t r i e n t analyses of these leaves inappropriate f o r use a s samples from a s i ng l e population. Furthermore, species d i f f e r i n t h e i r a b i l i t i e s t o ass imi la te , r e t a i n or accumulate t o luxury leve ls , pa r t i cu l a r mineral elements. The a b i l - i t y of some species t o accumulate c e r t a i n heavy metals, f o r example, i s the bas i s f o r biogeochemical prospecting. Luxury accumulation of potassium by many species is well known. Cal-cium, being immobile, tends t o increase i n con-cent ra t ion i n leaves with age, but the i n i t i a l a b i l i t y t o ass imi la te calcium d i f f e r s from spe- c i e s t o species . Thus t he ana lys i s of f o l i a r nu t r i en t concentrations without regard t o species or ecotype i s t o be avoided.

The mul t ip le axes of va r i a t i on presented by. differences i n species , mineral p roper t ies , time of year and s o i l concentrations implies t h a t a much more massive sampling program must be un-dertaken t o observe meaningful t rends from f o l i a r analyses than has character ized some of t he a i r po l lu t ion s tud ies reported.

Short of a f u l l nu t r i en t budget ana lys i s , changes i n the mineral composition of f resh l i t t e r f a l l during peak l i t t e r f a l l periods may provide a more su i t ab l e ind ica tor of nu t r i en t changes due t o po l lu t ion s t r e s s , a s t h i s com-ponent is standardized i n time, and weighted t o the f o l i a r biomass composition of the fo r e s t . Even so, l a rge sample-sizes a r e needed, and much caut ion i n extrapolat ion of r e s u l t s w i l l s t i l l be necessary.

WHAT IS THE ROLE OF CULTURAL VALUES I N A I R POLLUTION RESEARCH?

WHAT ARE THE SOCIAL RESPONSIBILITIES OF SCIENTISTS, AND HOW CAM THEY BE DISCHARGED?

As na tura l s c i e n t i s t s , we tend t o r e l ega t e the soc i a l context of our research t o other segments of society. We do so a t r i s k , however, because there a r e both soc i a l i s sues upon which we a r e most qua l i f ied t o comment, and socio-p o l i t i c a l forces which a f f e c t t he choice and conduct of our research problems. In t he course of the present Symposium, I was amused t o note the va r i a t i on i n perception of t he a i r qua l i t y i n Riverside during the period, by various pa r t i - c ipants . Some thought the smog l i g h t , o thers oppressively heavy. The smog concentrat ion was a constant; c u l t u r a l values were a t work i n influencing perceptions. As a second example,

some speakers emphasized t h e r o l e of a c i d r a i n a s a f e r t i l i z e r , whi le o t h e r s emphasized i t s t o x i c p roper t i e s . Of course , whether any pol- l u t a n t w i l l e x e r c i s e i t s t o x i c p r o p e r t i e s w i l l depend upon r a t e and dura t ion of a p p l i c a t i o n , and concen t ra t ion , a s w e l l a s upon t h e physio- l o g i c a l s t a t e of t h e recep to r organism and i ts ecosystem. I n t h e c a s e of c h a r a c t e r i z i n g t h e p r o p e r t i e s of a c i d r a i n , however, t h e a t t r i b u t e s chosen f o r emphasis were chosen f o r reasons having t o do with t h e c u l t u r a l a t t i t u d e s and values of t h e speakers , and n o t because of d i s -agreement over empi r i ca l observat ions . A s a t h i r d example, we heard from one Fores t Service r e p r e s e n t a t i v e dur ing t h e f i e l d t r i p t h a t t h e damaged por t ions of t h e San Bernardino National Fores t were n o t exper iencing d i f f i c u l t y i n r e -product ion. But, the E.P.A. sponsored, Univ-e r s i t y of Ca l i fo rn ia -Fores t Service resea rch team provided evidence t o t h e con t ra ry . Were these two p a r t i e s d i sagree ing over empir ical obse rva t ions , o r was t h e i r d i f f e r e n c e one of c u l t u r a l values and percept ions app l ied i n eva l - u a t i n g t h e s i g n i f i c a n c e of t h e same body of d a t a ? A s a f o u r t h example, r e c a l l t h a t about 50% of t h e a d u l t American populat ion smokes, thereby b r ing ing i n t o t h e i r lungs s e v e r a l times t h e ambient l e v e l s of p a r t i c u l a t e s and t o x i c gases p resen t i n po l lu ted urban a i r . W i l l t h e s e people pe rce ive the human h e a l t h hazards of outdoor a i r i n t h e same way a s nonsmokers? W i l l they a s s i g n t h e same weights t o t h e i r im-portance?

A t t h e very l e a s t , s c i e n t i s t s have a r e -s p o n s i b i l i t y t o d i f f e r e n t i a t e c l e a r l y between empi r i ca l observat ions and normative (va lue ) judgments. But does our r e s p o n s i b i l i t y t o decision-makers and t h e pub l ic s t o p the re? Much has been s a i d regard ing t h e appropr ia te - ness of s c i e n t i s t s i n o f f e r i n g va lue judgments t o s o c i e t y , and I w i l l no t e n t e r the debate here . I would, however, l i k e t o suggest a way i n which s c i e n t i s t s can h e l p t o c l a r i f y i n socia l ly-meaningful terms t h e s o c i a l c o s t s .of a i r p o l l u t i o n damage.

I b e l i e v e decision-makers would prof it from a f u l l e r understanding of t h e e f f e c t s of a i r p o l l u t i o n n o t only on t h e marketable a s p e c t s of ecosystem s t r u c t u r e ( s t and ing t imber, crop y i e l d , t o u r i s t revenue) , but a l s o on those a s - pec t s of ecosystem func t ion ing which c r e a t e h id - den c o s t s i n t h e market p lace . To t ake an example from t h e San Bernardino Nat ional Fores t oxidant s tudy which I have previously discussed (Westman, 1977), consider t h e d o l l a r c o s t s t o s o c i e t y of t h e l o s s of t h e s o i l binding func t ion from a i r p o l l u t i o n damage t o pines i n t h i s f o r - e s t . A s of 1972, 57% of t h e t r e e s over a 4000 h e c t a r e a r e a w i l l be replaced by a r e t r o g r e s -s i v e vege ta t ion of fo rbs and g rasses , and t h a t e ros ion l o s s e s from t h e l a t t e r w i l l i nc rease i n t h e p ropor t ion observed when chapar ra l was converted t o g rass land by t h e U.S. Fores t Ser-v i c e a t San Dimas i n t h e neighboring San Gabrie l Mountains, it is p o s s i b l e t o es t imate e ros ion l o s s e s from t h e s t r e s s e d f o r e s t . A t c u r r e n t r a t e s of cleanup of sediment from s t r e e t s , sew-

e r s and d e b r i s bas ins , t h e c o s t of damage from l o s s of the s o i l binding funct ion of t h e San Bernardino Mountain pines is $27 m i l l i o n per year . These c o s t s a r e being absorbed c u r r e n t l y by the general pub l ic not only a s d i r e c t t a x c o l l e c t i o n t o l o c a l governments c lean ing up t h e sediment, a s only a por t ion of t h e sediment i s being recovered i n t h i s way. The c o s t s a r e being absorbed a l s o i n terms of l o s s e s t o f i s h - e r i e s i n c o a s t a l waters where spawning a r e a s a r e smothered by sediments, by pub l ic works a l l o c a t i o n s f o r new dams, by flood damage f o l - lowing storms i n s i l t e d f lood channels. Rarely i f ever a r e these c o s t s a t t r i b u t e d t o smog and considered i n t h e c o s t - b e n e f i t a n a l y s i s of pro-posals t o i n s t a l l emission c o n t r o l devices . Fur the r , s o i l binding is only one of t h e func- t i o n s destroyed through death of t h e pines . Loss of the funct ions of n u t r i e n t cap tu re and r e - t e n t i o n , p o l l u t i o n absorpt ion, c l i m a t i c reg- u l a t i o n and energy f i x a t i o n a l l have t h e i r so-c i a l c o s t s , capable of a t l e a s t p a r t i a l enumer-a t i o n and eva lua t ion (Westman, 1978).

Complex a s t h i s process of s o c i a l c o s t i d e n t i -f i c a t i o n is, I suggest t h a t i t i s a t o p i c i n which s c i e n t i s t s can play a l a r g e r r o l e than we have t o d a t e , and a t o p i c t o which, it may be argued, we have a r e s p o n s i b i l i t y t o contribute-.

SUMMARY OF AUDIENCE PANEL DISCUSSION

Use of a i r p o l l u t i o n s imulat ion models i n dec i s ion-making

Discussion ensued on t h e c u r r e n t a p p l i c a b i l - i t y of computer models t o such immediate ques- t i o n s a s how t o s i t e power p l a n t s t o minimize damage t o vegeta t ion. Those with experience i n bu i ld ing models expressed cons ide rab le con- f idence t h a t these could be used, upon repara - mete r iza t ion , t o h e l p reso lve such ques t ions i n a number of p a r t s of t h e country. Experi-mental b i o l o g i s t s and land managers expressed concern t h a t t h e models were s t i l l too broadly conceived t o provide a c c u r a t e es t imates of d i f -ferences between s i t e s i n a s i n g l e vege ta t ion type. A number of t h e s p e c i f i c i s s u e s t h a t were broached a s p a r t of t h i s d i scuss ion a r e a s f o l -lows :

T r a n s f e r a b i l i t y of models between vege ta t ion types

What l e v e l of r e s o l u t i o n of a model is needed i n order t o provide a c c u r a t e p r e d i c t i o n s of p o l l u t i o n e f f e c t s on vege ta t ion , of use t o land managers? Are s i n g l e genera l models f o r each biome s u f f i c i e n t , o r do we need a model f o r each of 400 o r 500 American vege ta t ion types? How should a model be cons t ruc ted t o maximize i t s t r a n s f e r a b i l i t y between regions? Several suggested responses were o f fe red :

-1. The work of e c o l o g i s t s , a i r p o l l u t i o n resea rch s c i e n t i s t s and modelers could be

coordinated i n a nationwide resea rch l abora to ry consortium t o c o n s t r u c t working models of a i r p o l l u t i o n e f f e c t s on vege ta t ion f o r t h e major r e g i o n a l p l a n t formations. Land managers con-cerned with p a r t i c u l a r s i t i n g o r f o r e s t r y ques- t i o n s i n a reg ion of t h e country could submit a r e q u e s t t o t h e consortium f o r adap ta t ion of a r e g i o n a l model t o h i s o r he r p a r t i c u l a r problem. One advantage of t h i s approach i s t h a t b i o l o g i s t s and modelers who a r e most f a m i l i a r wi th t h e assumptions i n t h e model would be a v a i l a b l e t o opera te t h e model. Repe t i t ious resea rch e f f o r t s could be avoided, and experience accumulated from var ious r e g i o n a l e f f o r t s .

2 . Models which incorpora te t h e mechanis t ic b a s i s f o r a i r p o l l u t i o n e f f e c t s on vege ta t ion may be most e a s i l y adapted t o new vege ta t ion types wi th accuracy. "Mechanistic" bases may c o n s i s t of phys io log ica l models of t h e e f f e c t s of p o l l u t a n t s , temperature and mois ture on n u t r i e n t a s s i m i l a t i o n and photosynthesis , or they may c o n s i s t of ecosystem-level models i n which s e n s i t i v e a t t r i b u t e s of t h e ecosystem ( l i t t e r f a l l , evergreenness vs. deciduousness, spec ies longev i ty ) a r e modeled.

3 . The Nat ional Power P l a n t Team of t h e United S t a t e s F i sh and W i l d l i f e Serv ice has a v a i l a b l e a power p l a n t s i t i n g model which, although con-s i d e r i n g va r ious c o n s t r a i n t s , does n o t incorpora te a model of a i r p o l l u t i o n e f f e c t s on vege- t a t i o n i n d e t a i l . They have r e c e n t l y obtained, however, a copy of Kercher 's (Lawrence Liver- more Laboratory) f o r e s t growth model, and p lan t o make t h i s a v a i l a b l e f o r pub l ic use, and perhaps u l t i m a t e l y l i n k it t o t h e i r e x i s t i n g s i t i n g model.

4. A f o r e s t growth model f o r a p a r t i c u l a r ve-g e t a t i o n type appears t o r e q u i r e 1 - 2 person-years of e f f o r t t o c o n s t r u c t from sc ra tch . Re-paramete r iza t ion of an e x i s t i n g model is r e -garded a s a l e s s c o s t l y and time-consuming way t o provide a model f o r a new vege ta t ion type. An important l i m i t i n g f a c t o r t o t h i s e f f o r t i s t h e pauc i ty of f i e l d and l abora to ry fumi- g a t i o n da ta on e f f e c t s of a i r p o l l u t a n t s , a lone and i n combination, on s p e c i e s , e s p e c i a l l y over extended per iods . I n t h e absence of such f i e l d d a t a , s e n s i t i v i t y a n a l y s i s of t h e computer model may be used t o e s t a b l i s h t h e l i k e l y components of t h e ecosystem which w i l l be most adversely a f f e c t e d by a p a r t i c u l a r s t r e s s , and t o produce q u a l i t a t i v e scenar ios of worst case events .

5. Ex i s t ing models f o r many vege ta t ion types do n o t incorpora te long-term c y c l i c a l events such a s f i r e s , seed c y c l e s , e t c . However, mo-d e l s such a s those of Kercher do incorpora te these e f f e c t s . The f o r e s t growth model a v a i l - a b l e through Oak Ridge Nat ional Laboratory i s considered capable of a p p l i c a t i o n t o a l l e a s t e r n U. S. f o r e s t types except Southern p ine f o r e s t s .

Ecosystem-level i n d i c a t o r s of p o l l u t i o n s t r e s s

What a t t r i b u t e s of spec ies o r of ecosystems can be used by f i e l d e c o l o g i s t s and modelers a s s e n s i t i v e i n d i c a t o r s of l i k e l y po l lu t ion- induced changes?

1. Physiognomic a t t r i b u t e s ( l e a f c u t i c l e th ick- ness and chemist ry) , phenologic a t t r i b u t e s (age t o reproduct ion, dura t ion of f o l i a g e ) , and l i f e h i s r o r y a t t r i b u t e s (annual vs. per-e n n i a l na tu re , longevi ty of genera t ions ) a r e seen a s community-level i n d i c a t o r s . L i t t e r -f a l l may be a use fu l i n d i c a t o r of n u t r i e n t budget processes.

2. Growth r i n g s (dendrochronology) may be used a s a long-term record of f o r e s t growth responses. I n Pennsylvania, f o r example, t r e e r i n g a n a l y s i s i n f o r e s t i n t h e v i c i n i t y of pow- e r p l a n t s has been conducted.

3 . V i s i b l e i n j u r y symptoms, such a s t h e f o l i a r i n j u r y index used by Paul M i l l e r and co-work- e r s , may be use fu l . The Tennessee Valley Auth- o r i t y has recorded v i s u a l i n j u r y symptoms on t r e e s surrounding a number of i t s power p l a n t s .

4 . The use of p a r t i c u l a r l y s e n s i t i v e s p e c i e s , such a s l i c h e n s , was i l l u s t r a t e d e a r l i e r i n t h e Symposium.

Use of models i n s e t t i n g a i r p o l l u t i o n s t andards

Can a i r p o l l u t i o n models be used by agen- c i e s concerned wi th e s t a b l i s h i n g minimum con- c e n t r a t i o n s of ambient exposure t h a t w i l l cause damage t o vegeta t ion?

1. To t h e e x t e n t t h a t s t andards incorpora te s o c i a l values a s w e l l a s s c i e n t i f i c c r i t e r i a , a computer model of t h e type being discussed cannot be used t o s e t a s tandard.

2. On t h e o the r hand, computer models have been used t o determine l e v e l s of f o r e s t growth reduc t ion from p a r t i c u l a r l e v e l s of p o l l u t a n t s . This information a lone , o r converted t o econom- i c l o s s f i g u r e s , can be u s e f u l a s informat ion f o r c r i t e r i a documents used i n s tandard s e t t i n g .

3 . Models have been used t o c a l c u l a t e r a - d i a t i o n dose t o people i n t h e v i c i n i t y of nuclear power p l a n t s . The Indian Po in t power p l a n t was modified t o reduce damage of e f f l u -e n t t o f i s h l i f e , based on information obtained through a computer model.

4. Models of f o r e s t growth have i l l u s t r a t e d t h a t even a 5-10% decrement i n t r e e growth due t o a i r p o l l u t i o n can have severe long- term e f f e c t s on f o r e s t growth and composition. This is a p r e d i c t i o n t h a t would have been d i f - f i c u l t t o make with p r e c i s i o n i n t h e absence of a computer model.

A Research Agenda

During t he course of the synthesis session severa l suggestions were made regarding a reas i n which important information i s pa r t i cu l a r l y lacking. These research top ics a r e l i s t e d below.

Pa t te rns of Recovery i n Stressed Vegetation-- While many ecosystem s tud ies have documented t he ' i n e r t i a ' of the systems, fewer have observed t he recovery process. The emission source a t T r a i l , B r i t i sh Columbia, is an example of a point source whose emissions decreased dramatical ly i n t he l a t e 1930's. Studies of subsequent recovery of damaged vege ta t ion could t e l l us much about r e s i l i e n c e of t h a t f o r e s t ecosystem.

P r ec ip i t a t i on Chemistry--Much needs t o be known about t h e chemical transformations i n r a i n and snow a s they pass over t he surfaces of vegetat ion and s o i l , and how these i n tu rn a f f e c t t he f l ux of nu t r i en t s i n the ecosystem.

Mechanistic Models For Pa r t i cu l a t e ( i n -cluding heavy metal) Pollutants--Models f o r t he in jury t o p lan ts from tox ic gases a r e more advanced than those fo r pa r t i cu l a t e s . How do pa r t i cu l a t e s en te r p lan ts and a t what r a t e s ? How a r e t h e i r e f f e c t s r eg i s t e r ed? How can they be modeled?

Synergisms--Much i s unknown about the in- t e r ac t i ve e f f e c t s of severa l a i r po l lu tan ts on ind iv idua l species and on ecosystems. Fu-migation s t ud i e s should incorporate po l lu tan t combinations a s wel l a s t e s t the e f f e c t s of s i ng l e po l lu tan ts .

Long-term Effec t s of Po l lu tan t Exposure-- There i s a need f o r laboratory s t ud i e s of long-term exposures (g rea te r than one month) of a i r po l lu tan ts t o species. I n t h e f i e l d , exposures t o f o r e s t species occur over many years . It i s d i f f i c u l t t o understand long-term e f f e c t s on reproduction and growth i n t he absence of chronic exposure s tud ies .

Monitoring Data For Ambient Po l lu tan t Con- centrations--More of these data a r e needed f o r a l l p a r t s of t he United S t a t e s i f use of computer models with r e a l i s t i c ambient a i r concentrat ions is t o be achieved. The same data a r e needed f o r i n t e rp r e t a t i on of f i e l d observations.

I n t e r ac t i on of A i r Po l lu t ion S t resses With Management Practices--How does t he e f f e c t of an a i r po l lu tan t on a f o r e s t d i f f e r under d i f - f e r en t thinning regimes? This question may be examined i n t he next phase of research i n the San Bernardino Mountain pine fo r e s t s .

Carbon Dioxide Enrichment i n the Atmosphere-- Rising ambient CO2 l eve l s a r e a f f ec t i ng f o r e s t

growth. How do these e f f e c t s i n t e r a c t with ambient a i r po l lu t ion levels? How w i l l t he a f f e c t of C02 on global c l imate f u r t he r a f - f e c t po l lu t ion response of fo res t s?

Funding of Research on Forest Growth Models Spec i f ica l ly B u i l t t o Incorporate A i r Pol-l u t i on Effects--Most ex i s t i ng models sim- u l a t e f o r e s t growth i n the absence of pollu- t i o n e f f e c t s , and were funded by agencies other than those concerned with a i r po l lu t ion .

REFERENCES

Grime, J. P. 1979. Plant s t r a t e g i e s and vegetation pro-

cesses . 222 p. John Wiley and Sons, New York.

Noble, I. R., and R. 0. Slatyer . 1976. Pos t - f i re succession of p lan ts i n

Mediterranean ecosystems. 2 Proc. Symp. Environmental Consequences of F i r e and Fuel Management i n Mediterranean Ecosys- tems. H. A. Mooney and C. E. Conrad, eds p. 27-36. Forest Service, U. S. Dept. Agric., Washington, D. C.

Orians, G. H. 1975. Diversi ty , s t a b i l i t y and maturi ty i n

na tura l ecosystems. &I Unifying Concepts i n Ecology. W. H. van Dobben and R. H. Lowe-McConnel, eds. p. 64-65. Junk, The Hague.

Westman, W. E. 1977. How much a r e Nature's se rv ices worth?

Science 197: 960-964.

Westman, W. E. 1978. Measuring t he i n e r t i a and r e s i l i e n c e

of ecosystems. BioScience 28: 705-710.

Integration: a Role for Adaptive Environmental Assessment and

Management '

Nicholas C. Sonntag, Robert R. Everitt, Michael J. StaleyL

Abstract: Adaptive Environmental Assessment and Management (AEAM) is a proven methodology for integration and analysis of environmental research and management. Simulation modelling workshops are an essential part of the process. They act as a catalyst to focus analysis, stimulate discussion and foster communication amongst managers, planners and scientific disciplinarians.

Some of the philosophy and methodology are described along with a case study example on the Alberta Oil Sands Environmental Research Program (AOSERP). The emphasis is on how AEAM can help foster integration and communication of scientific information.

Over the last decade we have seen phenomenal growth of environmental science. It has spawned a proliferation of public and private institutions dedicated to environmental research and protection. Environmental research and management have become highly skilled, influential, and more often than not, respected professions. Governments have created such well meaning provisions as the National Environmental Policy Act (NEPA), the Clean Air Act and the Water Quality Act in the United States, and the Environmental Assessment and Review Process (EARP) in Canada.

These gallant efforts to research and protect the environment have over the years generated voluminous amounts of information; information intended ultimately to provide knowledge to help mankind better manage the world's environment and resources.

The challenge today is to analyze and make sease of the vast amount of data and knowledge. Unfortunately most research has been disciplinary

presented at the Symposium on Effects of Air Pollutants on Mediterranean and Temperate Forest Ecosystems, June 22-27, 1980, Riverside, California.

"ESSA Environmental and Social Systems Analysts Ltd., respectively, Vancouver, British Columbia.

based, and inspite of a desire for interdisciplis- ary coordination most large research programs have failed to integrate their results. One reason for this is the lack of a proper forum for communication amongst scientific specialists; another is the absence of a systematic framework for synthesizing results. While some programs have been successful at pulling the individual studies together few have been able to make the results relevant to environmental management. Many argue that this can be remedied by raising the quality of environmental research. Unfortunately there is a dichotomy between environmental research and environmental management. Research science cannot effectively guide managers because scientists do not readily comprehend management concerns; management cannot adequately direct research science since managers often do not have scientific knowledge or the breadth of understanding such knowledge provides. .This inability of scientists and managers to interact effectively has been a major stumbling block in developing progressive policies and attitudes towards the environment both in the public and private sector.

Adaptive Environmental Assessment and Management (AEAM), well documented in (tolling (19781, has evolved over the last ten years into a proven methodology for integrating environmental research while linking research and management. AEAM uses computer simulation modelling in a unique and novel way. Within a structured modelling workshop, the

task of constructing a simulation model acts as a catalyst to focus analysis, stimulate discussion and foster communication amongst managers, plan-ners, and scientific disciplinarians.

BIASES OF AEAM

Ecologist's understanding of ecosystem structure and behaviour have come from four basic properties which determine how ecological systems respond to change (Holling, 1978).

1. The parts of an ecological system are connected to each other in a selective way (this has implications for what should be measured).

2. Events are not uniform over space. (This has implications for how intense impacts will be and where they will occur.)

3. Sharp shifts in behaviour are natural for many ecosystems. (Traditional methods of monitoring or assessment can misinterpret these and make them seem unexpected or perverse.)

4. Variability, not constancy, is a feature of ecological systems that contributes to their persistence and to their self monitoring and self correcting capabilities.

Underlying each of these properties is the fact that environmental systems are characterized by overwhelming uncertainty. Man's understanding of the underlying biological, social and physical processes and interactions is minimal, and will remain so for the forseeable future. The complex and pervasive nature of environmental and social issues guarantees our ignorance will always exceed our knowledge.

The many sources of error in environmental sys-tems ensure that no matter how broad or deep an analysis inevitably something outside will influence the results and violate the predictions. The conclusion is that environmental and social systems are fundamentally unpredictable. If you accept this hypothesis then, how can environmental science produce effective research and management.

First and foremost we must never promote research and analysis as the panacea for prediction of the fate of society and its environment. Second, we must recognize that decisions are always made under uncertainty, and ignorance. Realizing this we must capitalize on methods that help focus ideas and information, integrate concepts, and guide decision making. Better decisions will usually be made with a clear picture of both knowledge and ignorance, and a broad appreciation of the consequences of action.

The key tool of AEAM is the computer modelling workshops. These short intense meetings circum- vent the natural scientific tendency for reduction- ism and the eternal cry for more studies. Parti-cipants in these workshops are forced to recognize that all components of natural resource systems

are not of equal importance and judgment is the toolof management not exhaustive research.

MODELLING WORKSHOPS: THE CORE OF AEAM

A modelling workshop is a 3 to 5 day meeting of a group of scientists, planners, and managers involved in the design and execution of an environmental study. No papers are presented, there is no keynote speaker, there are simply 3 to 5 days of focussed activity on the problems at hand. The development of a computer simulation model of the physical, biological, and social aspects of the problem serves as the focus for the workshop.

Participants in the workshop do need any knowledge of computers or modelling to contribute to the workshop and to gain from its results. Workshop facilitators translate participant input into quantitative relationships that can be pro- grammed into the simulation model. The facilitators can be viewed as information translators for it is the participants who conceptualize the model. Therefore the model that evolves from a workshop is as much a product of the ideas and concerns of people unfamiliar with modelling as it is a product of those familiar with simulation techniques.'

The obvious objective of a modelling workshop is to build and run a computer simulation model of the bio-physical system of interest. However, the resultant model is not an end in itself. Usually its predictions are not very precise and it often lacks obvious features of the actual system. Rather, the model is a focus for communication promoting objectivity and honesty. Building the model forces the participants to formalize their understanding of the system components and interactions. This facilitates easier evaluation of the importance of interactions to the system and the workshop objectives. Often favoured factors turn out to be irrelevant for predictions, therefore requiring less future effort both in model development and data-gathering programs.

As with many modelling studies, a workshop generated model confers the ability to test hypotheses, research plans and different management policies without risk. However, that is where the similarity usually ends. Since a workshop model is designed and built by all the participants its structure and resultant dynamics are "transparent" to the user. The model is comprehensible. This inspires trust and increases insight thereby promoting generalization of the model projections. It also facilitates easier evaluation of those factors left out of the model.

The modelling workshop style prevents the building of a sophisticated state of the art simulation model. The workshop model is invariably simple in structure and inefficient in operation. Further by striving to simplify the problem the need for sophisticated tools such as complex implicit (or explicit) finite difference methods for approximat- ing differential equations are usually avoided.

Although the precision of the model's predictions may suffer simplification does not deter from the objectives of participant involvement, communication and understanding. People are the key components in the modelling workshop not the model. This does not have to be the case after the workshop. Often the model structure established serves as an excellent guide for future modelling efforts when more consideration can be given to the "art" of simulation modelling.

By definition any simulation model is "wrong" since it must be a simplification of reality. However, complex models do not necessarily make better predictions. As the number of variables increases, so does the number of assumptions about how they are related and the chances of making a critically wrong assumption rises rapidly. There-fore parsimony is the underlying workshop modelling theme. Interactions and relations should make sense when interpreted in terms of physics and biology. Logical consistency and clarity are stressed in the building of the workshop model and go far in maintaining its "transparency" to the participants.

The incorporation of modelling workshops in the AEAM process is designed to be iterative. By locating them between sequential field programs the researchers and managers have the opportunity to adapt research plans and management policies in light of new insights emerging from the modelling workshop exercise. The AEAM process, and specifically modelling workshops, can be success- fully implemented at any point in a study, right up to the end. The integration and coordination aspects of modelling workshops provide a useful vehicle for communication among those responsible for preparing environmental overviews and assessments. This ensures they are pertinent, credible, and address the questions being asked. Further the resultant model (after some refinement) provides a very effective device for summarizing and presenting the results of a study to policy makers, administrators and/or funding agencies. A workshop held in 1979 on the Alberta Oil Sands, is a good example of such an application.

ASSESSMENT OF THE ENVIRONMENTAL EFFECTS OF ALBERTA OIL SANDS DEVELOPMENT

Setting

'The development of the Athabasca Deposit, one of several oil sands deposits in Alberta, has been the subject of intense interest for several decades. The Athabasca Deposit contains more than 600x10" barrels of bitumen reserves, and constitutes about 88 percent of known oil sands in Alberta. Consequently its potential to augment the oil supply of Canada has been a driving force in present development, and will continue to generate pressure for further development . . .

. . .The Government of Alberta has an established policy of environmental legislation which allows for the orderly development of resources with

a minimum of environmental damage. This policy resulted in particular attention being paid by regulatory agencies to the need for development of an environmental research program for the Athabasca Oil Sands region. Consequently, late in 1973, officials of Alberta Environment (Research Secre- tariat) and Environment Canada (Environmental Management Service) separately produced internal reports recommending a comprehensive environmental research program. Projections in each of the reports favoured an environmental research program lasting 10 years, with total costs estimated in the range of $30 million to $40 million." (Smith 1979) .

The Alberta Oil Sands Environmental Research Program (AOSERP) began in April, 1975. Early investigations were used primarily to establish large data bases. The data bases were intended to facilitate the construction of models to aid in predicting physical, chemical, biological, and social impacts of Oil Sands development.

In the fall of 1979, AOSERP sponsored an AEAM modelling workshop. By this time the program had been organized into four systems: Air, Land, Water and Human. The objectives of the workshop were: (1) to construct a simulation model that would provide a mechanism of integration of the plethora of AOSERP data and information; (2) to delineate the interrelationship between the systems (Air, Land, Water, Human) that are basic to a general understanding; (3) to identify and evaluate data gaps and uncertainties about system function; and (4) to evaluate and recommend approaches to environmental management in the oil sands areas, including mechanisms for technology transfer from AOSERP to Alberta Environment regulatory branches (Staley and others 1979). The participants in the workshop included the director of AOSERP, the heads of the Air, Water, Land and Human systems, the chairman of the Research Secre- tariat of Alberta Environment, as well as numerous government scientists and planners, and private consultants.

Simulation Model

During the bounding exercise, the workshop decided to consider the entire AOSERP study area which comprises approximately 2.86xlo4 square kilometers of northeastern Alberta, Canada with the spatial resolution based on the area's 13 water drainage units. To assess impacts over a meaningful period, a thirty year time horizon with a yearly time step was used. Important system phenomena operating on a shorter time scale were represented implicitly within the one year step. The simulation model was divided into four interrelated submodels: human, physical transport, aquatic biology, and terrestrial.

The human submodel consisted of three components:

1. An industrial component that generated a number of different development scenarios.

2. A population component t h a t estimated the population based on background growth and development r e l a t ed growth scenarios .

3 . A land component t h a t calculated the land requirements f o r urban, i ndus t r i a l and t ransporta- t i o n needs.

The t ranspor t submodel was concerned with the physical t ranspor t of water, a i r , and associated po l lu t an t s throughout t he AOSERP area . The water component was a simple hydrological model of the flow within t he 13 water drainage u n i t s . Relevant water po l l u t an t s were se lec ted as water qua l i t y ind ica tors and t h e i r concentrations were ca l cu l a t -ed f o r each water drainage u n i t .

The aquat ic biology submodel was concerned with t he impacts of commercial and recrea t iona l f i she r -men, instream flows, and instream pol lu tan ts on four common f i s h species .

The t e r r e s t r i a l submodel was responsible fo r represent ing t h e vegetat ion and w i ld l i f e dynamics. The model concentrated on t he economically impor- t a n t species moose and beaver and t h e i r hab i t a t .

RESULTS

A de ta i led descr ip t ion of the simulation model and i t s r e s u l t s a r e found in Staley e t a l . (1979). However, t h e r e s u l t s of applying t he AEAM process a r e f a r more important than the o u t p u t o f the model. Each submodel made e x p l i c i t a number of da ta and information gaps. A t t he conclusion of the workshop it was apparent t h a t many of the da ta gaps revealed by the simulation modelling exercise could be f i l l e d by appropriate reorgani- zat ion of t he AOSERP data base. However, it a l s o became c l e a r t h a t a f u r the r conceptual understanding of the environmental system under study was needed before a de t a i l ed ana lys i s of the e f f e c t s of o i l sands development could be made. This has important implicat ions for f u tu r e research s ince the da ta basel ine has been establ ished. Further research should concentrate on understanding the dynamics of t h e system. In other words the focus needs t o be on those things t h a t cause va r i a t i on and change i n t he system, and not on t h e cur ren t s t a t e of t h e system.

The simulation model i t s e l f provided a vehicle f o r in tegra t ion of f i ve years of environmental research. The process of bui lding the model i n the workshop revealed a number of important r e l a t i on - ships between the (Air, Water, Land, Human) systems t h a t a r e bas ic t o an overa l l understanding.

The appl ica t ion of the AEAM process t o AOSERP is not complete. The next phase which should be completed i n t he f a l l of 1980 w i l l concentrate on developing the model a s a t oo l t o a i d environmental management i n t he o i l sands a r ea . The many conceptual weaknesses and bad data i n the simulation model w i l l be remedied through a s e r i e s

of technical meetings t o be held with the s t a f f of each of the Human, Land, Water and A i r systems. The r e s u l t s of these meetings w i l l guide model refinement. The f i n a l model w i l l be put together i n an in tegra t ion workshop where the pa r t i c ipan t s of the or ig ina l workshop and the technical meetings w i l l i n t e r ac t i ve ly game with the model. Once t he model goes through t h i s " t r i a l by f i r e u before i t s c rea tors t he model w i l l be used t o evaluate a number of environmental management s t r a t e g i e s . This w i l l be done i n an one day pol icy workshop focussed on t he evaluation of the model's p ro jec t ions . I t i s the r e s u l t s of t h i s l a t t e r s tage t h a t w i l l measure the degree of success of t h i s appl ica t ion of AEAM.

CONCLUSIONS

The AEAM process represents the combined learning of a number of in te rna t iona l s c i e n t i s t s and p rac t i t i one r s and is i n a s t a t e of "dynamic equ i l i - brium", cont inual ly adapting i n l i g h t of new experience. But the term "adaptivew s t r e s s e s a more important lesson, the need fo r research and management t o be open t o change and t o be adapt i n both s t y l e and content when new information becomes ava i lab le . While AEAM i t s e l f i s i n a cont inual s t a t e of change, i t s two underlying -themes, expect the unexpected, and learn t o plan and plan t o learn , never change.

Ut i l i z ing the modelling workshop provides many benef i t s t o the success of the AEAM exerc i se . I t forces pa r t i c ipan t s t o focus on the re levant i s sues , promotes i n t e rd i s c ip l i na ry communication, i d e n t i f i e s information needs, provides a framework fo r evaluation of ex is t ing information and management ac t ions , and i s a guide fo r environmental pol icy design.

AEAM through i t s use of simulation i n t he workshop s e t t i n g provides a mechanism fo r in tegra t ing information and f a c i l i t a t i n g the ana lys i s of impacts r a the r than massaging basel ine da ta . I t i s through thoughtful synthesis , ana lys i s and e f f ec t i ve communication of environmental information t h a t environmental managers and researchers w i l l make e f f ec t i ve use of t h e i r resources: time, money and exper t i se .

LITERATURE CITED

Holling, C.S. ( ed i t o r ) . 1978. Adaptive Environ- mental Assessment and Management. 377 p .

Wiley Inter-Science, Chichester.

Smith, S.B. ( ed i t o r ) . 1979. Alberta O i l Sands Environmental Research Program Interim Report

covering period April 1975 t o November 1978. Prepared by A.S. Mann, R . H . Hursey, R.T. Seidner, and B. Kasinska-Banas. Edmonton, Alberta.

Staley, M . J . , and o thers . 1979. Report of a s i m -u l a t i on modelling workshop on t he environmental e f f ec t s of Alberta O i l Sands development. 73 pp.

Documents

Effects of air pollutants on Mediterranean and temperate forest ecosystems