Range of Natural Variability

Pete FuléNorthern Arizona University

• What is RNV?• RNV relates to … Ecosystem

Management … Ecological Restoration … Conservation Biology

• Historical forest structure and function in the Southwest

What is RNV?• “A science of land health needs, first

of all, a base datum of normality, a picture of how healthy land maintains itself as an organism.” Aldo Leopold (1941)

• What is the “base datum”?

• Terms: range of natural variability, historical variability, reference conditions

“We define natural variability as the ecological conditions, and the spatial and temporal variation in these conditions, that are relatively unaffected by people, within a period of time and geographical area …”

(Landres et al. (1999): Ecol. App. 9:1279-1288)

• “The (dynamic) conditions that would exist if the dominant Euro-American culture had never arrived, but Native Americans had continued to use the landscape.”

(Stephenson (1999): Ecol. App. 9:1253-1265)

Why care?• Modern human impacts may diminish

species viability.• Coarse-filter management strategy

conserves even poorly understood species.• Fewer external subsidies when manage

within bounds of system.• Useful reference point for human-caused

impacts.• Analysis at long time frames & large scales.• Recognizes importance of disturbance.• Spatial heterogeneity important for

resilience.Landres et al. 1999

RNV and Ecosystem Management

• Conservation of ecosystem structure, composition, and function across the full range of spatial and temporal scales:

– Think long term– Save all the pieces– Save all the processes– Assure sustainability

Kaufmann et al. (1994)Gen. Tech. Rep. RM-246

EcologicalPrinciples Applied at

AppropriateSpatial

And TemporalThemes

Ecosystem Needs Assessment

Kaufmann et al. 1994, Gen. Tech. Rep. RM-246

Analysis Area

Reference Conditions

Coarse FilterAnalysis

Ecosystem Needs& Capabilities

Fine FilterAnalysis

ExistingConditions

Analysis Area

Reference Conditions

Coarse FilterAnalysis

Ecosystem Needs& Capabilities

Fine FilterAnalysis

ExistingConditions

• Air Quality• Water Quality• Weather• Hydrology• Aquatic Systems• Geomorphic

Processes• Fire/Fuels Regime

• Corridors• Travel Linkages• Species Viability• Fragmentation• Habitat Relationships• Insects & Pathogens• Nutrient/Soil

Productivity• Succession &

Community

Ecoregion Subregion Landscape Watershed/Land Unit

RNV and Ecosystem Management

• EM (and other management approaches) are not “science-based” but “science-informed.”

• RNV is fundamental to EM but is not necessarily the goal.

• In Ecological Restoration, the RNV can become the goal or target of a management action.

• But ER is a subset of EM (“tool in the toolbox”…).

• Ultimately our objective is not to pick some perfect management paradigm, but to continually improve and adapt management in an evolving relationship between ecological and social constraints and capabilities.

RNV and Ecological Restoration

•Ecological restoration is the process of assisting the recovery and management of ecological integrity. Ecological integrity includes a critical range of variability in biodiversity, ecological processes and structures, regional and historical context, and sustainable cultural practices” (Society for Ecological Restoration 1998).

•“Ecological restoration is the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed” (SER 2002).

Restoration shares many values with sustainable resource management, conservation biology, and land reclamation. Two distinguishing characteristics are:

(1) The use of intact, indigenous ecosystems as the point of reference;

(2) A focus usually at the scale of entire ecosystems.

Southwestern forest restoration traces its lineage to Aldo Leopold. Key studies were done by Harold Weaver (1940’s-50’s) and Charles Cooper (1950’s-60’s), as well as many other scientists and resource managers.

Reference Conditions: Leopold’s “base datum”

1. Reconstruct past conditions through dendroecological, paleoecological, or other historical ecology techniques.

2. Measure relatively undisturbed contemporary sites to compare to reconstructed data and to explore the effects of altered modern conditions such as high CO2 levels.

3. Draw inferences from ecological relationships observed in disturbed sites.

4. Restore ecological conditions as a modern model for observing ecosystem function.

Information on RNV: Multiple Lines of Evidence

• Information on RNV is often fragmentary, limited, incomplete.

• Make use of multiple lines of evidence.

• Always recognize limitations of the data.

Swetnam et al. 1999, Ecol. App. 9:1189-1206

Historical Ecology Methods: Written & Oral Histories

• Written documents include historic forest inventories, scientific/military expeditions, colonial records, land surveys, diaries, missionaries.

• Photographs and maps.• Oral histories may be available or

you may develop an oral history to capture local knowledge.

Written Histories & Photographs

• Goals and cultural filter of the historian.

• Propaganda and advertisement.

• Biases in scientific studies.

• Biases in forest inventories.

• Practical biases (selection of trees in land survey).

• All these factors also apply to maps and photographs. Photo G. Pearson 1909, Grandview (Grand Can.)

Courtesy Rocky Mountain Research Station

Mt. Trumbull, Arizona: 1870Moore et al. (1999), Ecol. App. 9:1266-1277.

Mt. Trumbull, Arizona: 1995Moore et al. (1999), Ecol. App. 9:1266-1277.

Logging near Cloudcroft from 1903, courtesy of the Rick Miller collection of historic photos. There are historic Mixed Conifer plots in "Cox Canyon" (south of Cloudcroft) and Douglas-Fir plots near (what is now) Pine Campground.

Andrew Sanchez Meador

Detail of a forest plot mapped in 1915 by G. Pearson and T. Woolsey, Fort Valley Experimental Forest, AZ

Check mark on Woolsey map represents a ponderosa pine seedling over 12“; X with a line under it is a cut yellow pine stump.

Andrew J. Meador

Taos: several Woolsey plots around Taos, but most have not been found. Amole,Gallegos, Cienaga, Osha Canyon, Rio Pueblo, La Junta, and numerous plots inAngostura. This is a pine plot at Amole.

Andrew Sanchez Meador

Cienaga post-fire ingrowth.

Andrew Sanchez Meador

Written and Oral Histories Include Traditional Knowledge

• Native American sources– Kat Anderson, California tribes– Thom Alcoze, Kaibab Paiute & Cherokee

• Anthropological sources– Ranching, farming, logging practices

• Relationship between historical sources and archeological evidence

• Relationship between historical sources and ecological evidence– Population and fire in Mexico– Apache presence/cambial scars/fire in New Mexico

Historical Ecology Methods:Dendroecology

• Application of dendrochronology (crossdating tree rings) to ecological questions.

• Dendrochronology invented in Flagstaff!

• Basics of dendrochronology• Climate example• Forest structure example

Laboratory of Tree-Ring Research, University of Arizona

Woodhouse & Bauer: World Data Center A

Woodhouse & Bauer: World Data Center A

Reconstructing Forest Structure with Dendrochronology: Gus Pearson Natural Area

• Dendrochronology for tree age• 100% sampling of dead trees

– Test of reconstruction methods– Test of accuracy of restoration silviculture

• Mapping of all tree positions• Age structure: RNV & target for

restoration• Age structure of groups: regeneration

and fire patterns

GPNA 1992

0

2000

4000

6000

1545

1585

1625

1665

1705

1745

1785

1825

1865

1905

1945

1985

0

10

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1545

1615

1685

1755

1825

1895

# T

rees

Mast et al (1999)Ecol. App. 9:228-239

Assessing Age Structure for Ecological Restoration

Mast et al. 1999, Ecol. App. 9:228-239

0

0.2

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1.2

0 30 60 90 120

150

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Tree Age

Fre

qu

ency

1992 Age Frequency 1994 Age Frequency 1876 Age Frequency

Restoring Spatial Structure of the Forest

Covington et al. (1997)Journal of Forestry 95:23-29

1876

1992

After Full Restoration

Changes in forest structure since 1876 at the Gus Pearson Natural Area ecological restoration site

Restoration Techniques

• Overstory trees: thinning, species composition, spatial pattern, old-growth.

• Understory herbs and shrubs: natural regeneration, seeding, planting.

• Fuels: accumulated fuels, canopy fuels, dead biomass as nutrient sources and habitat.

• Fire: re-introducing fire, unique initial burn conditions, smoke.

• Monitoring and adapting: evaluating results and making changes.

Covington, W.W., P.Z. Fulé, M.M. Moore, S.C. Hart, T.E. Kolb, J.N. Mast, S.S. Sackett, and M.R. Wagner. 1997. Restoration of ecosystem health in southwestern ponderosa pine forests. Journal of Forestry 95(4):23-29.