Managing Organic Debris for Forest HealthReconciling fire hazard, bark beetles,wildlife, and forest nutrition needs

Chris Schnepf, Russell T. Graham, Sandy Kegley, and Theresa B. Jain

PNW 609 A Pacific Northwest Extension PublicationUniversity of Idaho Oregon State University Washington State University

Managing Organic Debris for Forest HealthReconciling fire hazard, bark beetles, wildlife, and forest nutrition needs

Chris Schnepf, Russell T. Graham, Sandy Kegley, and Theresa B. Jain

A Pacific Northwest Extension PublicationUniversity of Idaho

Oregon State UniversityWashington State University

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THE AUTHORSCHRIS SCHNEPF is an Extension Foresterfor the University of Idaho based inCoeur d’Alene. He provides educationalprograms for forest owners, loggers, andothers interested in applied forestecology and silviculture.

DR. RUSSELL T. GRAHAM is a researchforester and silviculturist with the USDAForest Service Rocky Mountain ResearchStation in Moscow, Idaho. His researchfocuses on landscape processes and long-term forest productivity concentrated onmanagement of forest organic materials.

SANDY KEGLEY is a forest entomologistwith the USDA Forest Service, NorthernRegion, Coeur d'Alene Field Office. Sandyis involved in survey, detection, evaluation,prevention, and suppression of bark beetlesand other major forest insects in northernIdaho and western Montana.

DR. THERESA B. JAIN is a research foresterand silviculturist with the USDA ForestService Rocky Mountain Research Stationin Moscow, Idaho.

PUBLICATION ORDERINGCopies of this publication may beobtained from:

UNIVERSITY OF IDAHO – EducationalCommunications, P.O. Box 442240, Moscow,ID 83844-2240; tel: (208)885-7982; e-mail: calspubs@uidaho.edu

OREGON STATE UNIVERSITY – PublicationOrders, Extension and Station Communica-tions, 422 Kerr Administration, Corvallis,OR 97331-2119; tel: 541-737-2513 ortoll free: (800) 561-6719;e-mail: puborders@oregonstate.edu

WASHINGTON STATE UNIVERSITY –Extension Publications, Cooper PublicationsBuilding, P.O. Box 645912, Pullman, WA99164-5912; tel: (509) 335-2857 ortoll free: (800) 723-1763;e-mail: ext.pubs@wsu.edu

COVER PHOTOForest organic debris is important for soilhealth. The main photo shows a log in theprocess of decomposing and addingstructure to the soil. Thumbnail photosshow organisms that will thrive in an areawith healthy forest soil and coarse woodydebris: chanterelle mushroom, pileatedwoodpecker, and fisher.

FUNDINGPartial funding for this publication wasprovided by the USDA Forest Service,Northern Region State and Private Forestry.

ACKNOWLEDGMENTSThanks to the following people whoreviewed this publication and providedmany constructive comments:

Matt Abram, Logger, Hayden, Idaho

Janean Creighton, Washington StateUniversity, Spokane

Renee d’Aoust, forest owner, Clark Fork, Idaho

Debbie Page-Dumroese, USFS RockyMountain Research Station, Moscow, Idaho

Steve Fitzgerald, Oregon State University

Steve Funk, Forest Owner, Coeur d’Alene, Idaho

Don Hull, Logging Safety Advisor, IdahoLogging Safety Bureau, Coeur d’Alene, Idaho

Bill Lukens, Forest Owner, Sandpoint, Idaho

Ron Mahoney, University of Idaho, Moscow

Ron Reuter, Oregon State University, Bend

Terry Shaw, Intermountain Forest TreeNutrition Cooperative, Moscow, Idaho

© 2009 by University of Idaho. All rights reserved. Published 2009

CONTENTS

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

INLAND NORTHWEST FOREST SOILS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Influence of fire on organic debris . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Organic debris & nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Organic debris & soil moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Organic debris & soil structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Organic debris, roots, & mycorrhizal fungi . . . . . . . . . . . . . . . . . . . . . . . .9

MANAGEMENT OBJECTIVES FOR ORGANIC DEBRIS . . . . . . . . . . . . . . . . . . .15Fine organic debris (FOD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Coarse woody debris (CWD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

STRATEGIES FOR MANAGING FIRE AND ORGANIC DEBRIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Fire hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Methods to reduce fire hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

STRATEGIES FOR MANAGING BARK BEETLES AND ORGANIC DEBRIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

Pine engraver beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35Douglas-fir beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37Spruce beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37Fir engraver beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39Generalizations about bark beetles and organic debris . . . . . . . . . . . . . . .39

STRATEGIES FOR MANAGING WILDLIFE AND ORGANIC DEBRIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

Snags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43Coarse woody debris size and characteristics . . . . . . . . . . . . . . . . . . . . . .45Coarse woody debris arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47How much coarse woody debris for wildlife? . . . . . . . . . . . . . . . . . . . . . .47

CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48

APPENDIX: ORGANIC DEBRIS ESTIMATES . . . . . . . . . . . . . . . . . . . . . . . . .50Photo series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50Measuring Organic Debris . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58

PHOTO AND ILLUSTRATION CREDITS . . . . . . . . . . . . . . . . . . . . . . . . . . . .60

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Figure 1. Removing organic debris is criticalwithin 100 feet of homes and structures.

Figure 2. Poor soil means poor trees.

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INTRODUCTION

Forest organic debris includestree limbs, boles (trunks), needles,leaves, snags, and other deadorganic materials. It ranges inamount and composition dependingon a forest’s history, tree species,condition, and age. In the InlandNorthwest (Idaho, westernMontana, eastern Oregon, andeastern Washington) there is a lotof discussion and concern aboutremoving organic debris fromforests.

Common reasons for removingorganic debris include reducingbark beetle hazard, preparing a sitefor tree planting, harvesting forestbiomass for energy, and reducingfire risk. For example, it is criticalto remove organic debris within 100feet around homes and structuresto reduce fire risk (fig. 1). And somepeople simply like the aestheticsof a forest with less organic debris-- loggers often speak with prideor admiration of “a good cleanlogging job.”

All these issues are important.But leaves, needles, and woodydebris left in a forest are not neces-sarily wasted. A growing body ofresearch supports leaving someorganic debris in forests (fig. 2).Organic debris left distributedacross the forest floor acts much

like mulch in a garden. It protectssoil from excessive moisture loss,recycles nutrients for trees andother forest plants, adds structureand organic matter to the soil,reduces soil erosion, and providesfood and habitat for a wide varietyof wildlife.

Many landowners are unclear onhow to reconcile the potentiallyconflicting objectives related toforest organic debris. As a result,some landowners tend to removeall organic debris while others maytreat as little as possible, to savemoney and time.

This publication outlines the roleof forest organic debris in InlandNorthwest forests and provides gen-eral management recommendationsto maintain forest soil productivityand improve wildlife habitat, whilesimultaneously reducing wildfireand insect hazards.

Many people refer to all branchesand tops accumulated from loggingor a storm as “slash.” But differenttypes of organic debris have differ-ent functions and differentmanagement challenges. To thatend, this publication differentiatesbetween two broad categories offorest organic debris: fine organicdebris (FOD - material smaller than3 inches in diameter) and coarsewoody debris (CWD - material 3inches in diameter and larger).

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Figure 3. Forest soils are a living growthmedium for trees and other organisms.

Figure 5. In frequently burnedforests, organic layers can be thin.

Figure 4. Surface organic layers cancommonly be 1-2 inches deep onmoist or cold forests.

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INLAND NORTHWESTFOREST SOILS

Soils are the foundation of forestgrowth and health. They providestructural support, nutrients, andwater storage for trees and otherforest plants and fungi. Soil quality,rainfall and temperatures determinehow a forest regenerates, develops,and functions. Over thousands ofyears, climate and vegetation breakdown or “weather” parent materials(the bedrock and/or sedimentsunderlying a forest soil) into a uniquemineral soil for a given forest site.

Many Inland Northwest forestsoils have also been significantlyinfluenced by wind-blown depositsof soil and volcanic ash. In additionto mineral contents, a large portionof a soil’s volume is made up of porespace, which helps a soil retain andstore moisture and allows foroxygen and carbon dioxideexchange around roots.

Organic materials from plants,animals, and fungi are also integralparts of a forest soil. These livingand dead organic componentsinfluence critical forest soil func-tions such as water holding, nutrientstorage and release, aeration,nitrogen fixation, bacterial andfungal habitat, and protection fromcompaction and erosion (fig. 3).The contribution of organic debristo forests is as variable as theforests where it occurs. InlandNorthwest forests range from moistcedar-hemlock forests to cold lodge-

pole pine-subalpine forests to dryponderosa pine forests.

The most noticeable organiccomponent of forest soils are thesurface organic layers. These “duff”layers usually consist of freshlyfallen twigs, leaves, and needles.In the middle of the surface layers,there is usually a layer where plantand tree materials are beingdecomposed by insects, worms,fungi, bacteria, and other organisms.Below this, plant parts havedecomposed to where they are notdistinguishable.

These surface organic layers arehighly visible in a soil profile ofmoist forests and cold forests—often one or two inches deep(fig. 4). In dry forests and otherfrequently burned forests, theselayers can be very thin or evennonexistent (fig. 5). However, wherefire has been excluded from dryforests, large amounts of organicmaterials can accumulate due tovery slow decomposition. This ismost apparent around the basesof mature ponderosa pines thatcontinually slough off bark andshed heavy amounts of needles.

Varying amounts of wood fromdecaying tree limbs and stems (alsocalled boles, trunks, or logs) areoften mixed in the surface organiclayers of forest soils (fig. 6). Rottenwood (often brown and cubical) isthe most noticeable and longest-lived organic material in forest soils,lasting up to centuries. Rotting

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Figure 7. Rotting wood canalso be found deeper in the soilprofile.

Figure 6. Wood is often found mixed in organiclayers.

Figure 8. Stand replacing fires often left agreat deal of coarse woody debris.

Figure 9. Roughly half of aconifer’s above-ground nutrientsare stored in the needles andbranches.

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wood can also be found deeper inthe soil. It can be created bydecaying tree roots or by logsburied under sediment by soilerosion after wildfires, or other soilmovement processes. In some coldand moist forests, up to 40% of thetop 12 inches of a forest soil can becomposed of this buried rottenwood (fig. 7).

Influence of fire on organic debrisHistorically, wildfire helped

determine the amount of fine andcoarse woody debris in forests.Wildfires can be separated into twobroad classes. Stand replacing fires

killed nearly all of the trees. Surface

fires killed small trees andvegetation in the understory but leftoverstory trees alive. Many individ-ual fire events were a mixture ofthese two types of fire (sometimescalled mixed severity fires).

Stand replacing fires did notusually completely consume allwood on the site, particularly ifintervening surface fires reducedunderstory vegetation and fine fuels.Stand replacing fires typicallymoved through a site fairly quickly,burning up the needles and finebranches and leaving a charred seaof standing and fallen dead trees intheir wake (fig. 8). Even wherethese sites burned again, somecoarse woody debris remained.

Dry forests had frequent surfacefires (every 7 to 30 years), andtended to have less large wood.Each fire would consume woody

debris, but it would also kill sometrees, which would create snags thatwould fall to the ground and replen-ish some of the wood consumed inprevious fires.

In addition to fire, forest soilorganic material can also comefrom trees killed or damaged byinsects, disease, or winter snowand ice storms, and from residuesof forest management activitiessuch as thinning.

Organic debris & nutrientsRoughly half of a conifer’s

above-ground nutrients, such asnitrogen and potassium, are storedin the needles, twigs, and smallbranches of the tree (fig. 9).Needles, limbs, and branches cycleorganic materials to the forest floor.Deciduous trees and shrubs alsocycle large amounts of nutrientseach year.

Moisture is the most limitingfactor to tree growth in most InlandNorthwest forests. But inadequatenutrients limit growth as well.Adding nutrients through fertiliza-tion increases tree growth on mostInland Northwest forests. Fertilizerscontaining nitrogen, potassium, sul-fur and boron especially promotetree growth, though the size of theresponse from different fertilizermixes varies considerably by site.

Repeatedly removing nutrientsfrom forests in the form of trees andgreen slash could theoreticallyreduce tree growth through nutrientdeficiencies. How much of a nutri-

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Table 1. Biomass and selected critical above-ground nutrients in trees (lbs/acre) in stand-ing mixed conifer forest before harvest

Nutrient Total Crown Merchantable Bark Merchantable Wood

Biomass 22,205.8 20,062.7 57,462.6

Nitrogen 121.521 54.593 24.448

Potassium 101.183 56.766 79.378

Sulfur 9.365 4.964 6.169

Boron 0.383 0.179 0.263

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ent reduction has not been studiedthoroughly, and would likely vary bysite, intensity and frequency ofremovals, and the time frame beingconsidered.1 But one way of lookingat it is to study the nutrient contentof slash.

A recent case study by theIntermountain Forest Tree NutritionCooperative estimated the nutrientcontent of trees in a fully stocked80-year-old mixed conifer stand innortheastern Oregon, with basaltparent material (table 1). In thegreen crowns of this stand, therewere an estimated 122 pounds ofnitrogen per acre and 101 poundsof potassium per acre. A harvest ofall the merchantable logs wouldremove an additional 79 pounds ofnitrogen per acre and 136 poundsof potassium per acre.

Most harvests and thinnings donot currently remove or immediatelyburn all this material. A lot of nitro-gen and other nutrients are alsostored in the surface organic layers.The amount of nutrients containedthere varies with climate and amountof disturbance. But since most ofour forests respond positively tocorrectly balanced mixes offertilizers, carefully consideringpossible nutrient implications offorest activities and adjusting themwhere possible could benefit forestgrowth and health.

Nitrogen naturally re-accumulatesin forests from atmospheric deposi-

tion and from nitrogen-fixing plantsand microbes, but this occursslowly. A recent study on a westernred cedar site in northern Idahofound that nitrogen re-accumulatedat a rate of roughly 4 pounds peracre per year.

Potassium and other nutrientsalso re-accumulate, but even moreslowly, mostly from parent materialweathering and in minisculeamounts from atmosphericprecipitation. The same study foundpotassium re-accumulating atroughly 2.5 pounds per acre peryear. The amounts vary by site, butpotassium and other nutrient losseswould be even more important onsoils with parent materials that werelower in these nutrients and slowerto decompose.

Allowing rain and snow-meltwater to leach water-solublenutrients from fresh slash downinto the soil retains more of thosenutrients for forest growth andhealth. The amount and rate ofnutrient leaching depends on thetree species and the climate.Warmer, wetter climates promotefaster leaching. The amount of thoseleached nutrients a site can captureand retain depends on the soiltexture and organic matter.

Even though fine organic debriscontains and recycles the majorityof a tree’s nutrients, coarse woodydebris (CWD) also provides somenitrogen, since some of the organ-

1 One set of studies (see Powers et al., 2005) found no growth reductions for the first ten yearsafter forest biomass removals, but the researchers cautioned that their findings did not necessarilyforecast long-term trends.

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Figure 10. Decayed logs serve as moisturereservoirs where conifers multiply roots.

Figure 11. The angular texture of some organicdebris decay products helps improve soil structure.

Figure 12. Most of a tree’s small feeding roots areconcentrated in the soil’s upper layers.

Figure 13. Ground fires can belethal to trees with many feederroots grown into excessively thickduff accumulations.

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isms that break it down fix nitrogenfrom the air. Depending on foresttype, bacteria in coarse woodydebris (CWD) can fix nearly 1/2

pound of nitrogen per acre everyyear. This amount, though relativelysmall, can be important, especiallywhen the site has few nitrogenfixing plants such as ceanothus oralder. Organic debris also helps soilsretain nutrients so they will laterbe available for forest plants.

Organic debris and soil moistureOrganic matter, as any experi-

enced gardener can attest, helpsretain soil moisture longer into thegrowing season by shading soils andstoring moisture. As organic debrisdecays and is incorporated into thesoil (fig. 10), conifers, grasses, forbs,and shrubs multiply their roots inthese zones to take advantage ofthat moisture. These moist soilzones help keep forests resilient inthe face of warmer, drier summers.Moist, decaying logs often persistafter wildfires.

Organic debris and soil structureSoil structure is the physical

combination or arrangement of soilparticles into larger particles orclumps, and the spaces betweenthem. Organic debris improves soilstructure as it is incorporated intothe soil. Leaves, stems and othersmall plant material are importantsources of organic materials in allsoils, but large woody debris can bea particularly significant and unique

contributor of organic matter forforest soils. As organic materialdecays and is integrated into the soilover hundreds of years, it helps soilsmaintain aeration (spaces betweenparticles), resist compaction, bufferagainst erosion, and improve waterfiltration (fig. 11).

Organic debris, roots, andmycorrhizal fungiWhere are the roots?

Regardless of species, most ofthe small roots and root hairs atree uses to take up nutrients andwater are concentrated near the soilsurface and surface organic layersof the soil (fig. 12). In surfaceorganic layers made deep by fireexclusion, trees often grow moreroots up into this material, to takeadvantage of the nutrients andmoisture there (fig. 13). When theselayers and the roots within them aredestroyed mechanically or throughfire, even the largest tree can bestressed and made more susceptibleto death by bark beetles or disease.

Forest soil flora and faunaIn addition to roots, forest soils

are alive with a variety of fungi,bacteria, worms, insects, andburrowing mammals such aspocket gophers. Different fungi usedifferent combinations of deadand living organic matter for theirsurvival. Many forest owners areaware of root diseases, stem decays,and other fungi that can kill trees orreduce the value of their wood. But

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Figure 14. Mycorrhizal fungi form a mutually beneficial relationship with trees.

Figure 15. Ectomycorrhizaecover the outsides of rootlets,just penetrating their outercells.

Figure 16. The tree seedling on theleft was innoculated with mycorrhizalfungi.

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most forest fungi do not kill trees.There are hundreds if not thousandsof lesser-known microbes and fungispecies that help forests function byrecycling forest nutrients, decompos-ing slash, and improving soil physicalproperties. Even native tree-killingfungi may be performing a positiverole by removing trees that arepoorly adapted to a forest site.

Mycorrhiza = “fungus root”One of the groups of fungi that

most directly benefit tree growthis called mycorrhizal fungi.“Mycorrhiza” is translated fromLatin as “fungus root.” Thesefungi infect the roots of trees andother plants and form a symbioticrelationship (a relationship inwhich both the plant and the fungibenefit). Mycorrhizal fungi getphotosynthate (the product ofphotosynthesis - carbon) from trees;and the trees get a larger effectiveroot surface to absorb more nutri-ents and moisture from the hyphae(the fungus equivalent of roots) andmycelia (matted hyphae) of mycor-rhizal fungi (fig. 14). In addition toimproving rooting surface area andabsorption, mycorrhizae can also:

• capture and retain nutrients thatmight otherwise be leachedfrom the soil;

• physically block pathogenicfungi access to tree roots;

• exude antibiotic substances thatdeter root pathogens;

• help “unlock” soil nutrients(convert them into forms that

can be used by plants);• exude or decay into substances

that act as “organic glues,” help-ing to aggregate soil particlesand improve soil structure;

• move nutrients and even photo-synthate (carbon) between trees-- even between differentspecies of trees and shrubs; and

• provide food for “fungivores” --insects, birds, squirrels, deerand many other organisms thatfeed on forest fungi.

Mycorrhizae are essential forgood growth of many tree species,particularly on nutrient-poor ordroughty sites.

Identifying mycorrhizaeMycorrhizal fungi form relation-

ships with over 95% of the plants onearth, and there are many differentspecies. Over 2,000 fungi have beenreported to form mycorrhizal rela-tionships with Douglas-fir alone. Ifyou dig up seedlings in the forest,you may notice that the root hairslook a little thicker than others youhave seen. That is because they arecovered by mycorrhizal fungi(figs. 15 and 16).

Mycorrhizal fungi producemany different kinds of fruitingbodies. Some are above-groundmushrooms, such as goldenchanterelles (Cantharellus

cibarius) (fig. 17). Other fruitingbodies are underground, such astruffles.

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Figure 17. Chanterelles, a popular edible forestmushroom, are the fruiting body of a mycorrhizalfungus.

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Helping mycorrhizaeMycorrhizae presence and

development on tree roots dependson organic matter. For example, inone study of a Douglas-fir forest,77% of the mycorrhizal root tipswere found in the surface organiclayers. Coarse woody debris, as itis integrated into the soil, eventuallybenefits mycorrhizae, becausecoarse woody debris helps soilsretain moisture as it decays.Minimizing compaction of the

mineral soil and minimizingexcessive soil disturbance alsobenefit mycorrhizae.

There is usually no need to addmycorrhizae to well-establishedforests. As with most fungi,mycorrhizae spores are abundantin native forests. However, treesplanted in non-forested areas suchas agricultural fields, or dramati-cally altered sites such as areclaimed mining area, may benefitfrom mycorrhizal inoculation.

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Figure 20. Past harvests left a lot of coarse woodydebris.

Figure 18. Fine organic debris is smallerthan 3 inches in diameter.

Figure 19. Coarse woody debris is largerthan 3 inches in diameter.

Figure 21. In some cases, CWDneeds can be met by not haulingcull logs to a landing.

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MANAGEMENT OBJECTIVES FORORGANIC DEBRIS

Organic materials play a large rolein forest soils and forest health. Thequantity and quality of forestorganic materials is directly andindirectly impacted by our forestmanagement activities. Fine organicdebris (materials less than 3 inchesin diameter) and coarse woodydebris (materials 3 inches indiameter and greater) have differentfunctions in a forest, different issuesassociated with them relative to fireand bark beetles, and different man-agement objectives and strategies.

Fine organic debris (FOD)Fine organic debris consists of

small branches, limbs, treetops andsimilar materials less than 3 inchesin diameter (fig. 18). FOD is quicklyincorporated into the forest floor,its nutrients are readily leached, andit is relatively short-lived – less than20 years depending on the foresttype. FOD can be a large firehazard if it is not carefully managedbecause it can quickly combust andcarry a fire.

Leaving FOD distributed acrossthe forest floor over winter andlonger if possible encourages itsdecomposition and nutrient leach-ing. The objective in managing fineorganic debris is to recycle the mostnutrients from it while minimizingthe fire hazard.

Coarse woody debris (CWD)In general, coarse woody debris

(logs and other woody pieces 3inches in diameter and larger) ismore durable than fine organicdebris (fig. 19). Depending on theforest type and its inherent distur-bances, 25% to 50% of the organicmaterial found in and on a forestsoil can be attributed to CWD.Coarse woody debris’s contributionto forest soils is not immediatebut long-term – from decades tocenturies depending on size, decayrate, and the forest’s fire frequency.

Historical timber harvests tendedto leave more coarse woody debris(fig. 20). Much of the old growthtimber had a lot of decay, and millsdidn’t take material below 8 inchesin diameter. Young forests tend tohave much less CWD than olderforests or those that haveexperienced insect, disease, fire,or weather damage.

Many second growth stands donot have as much malformed wood,due to management activities thatthinned poorly formed trees out.Trees are also harvested at youngerages, before stem decays develop asfully. Mills now take logs down tosmaller top diameters (for example,down to a 4-inch top rather than an8-inch top). All these factors meanless coarse woody debris is left onsite after logging jobs now than inpast timber harvests.

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Figure 22. Wood decay from “white rot”(top) vs. “brown rot” (bottom).

Figure 23. Removing logs with stem decaywill not reduce future stem decay on thatsite.

Table 2. Coarse woody debris recommendations for maintaining long-term forest growth

Climax species1 Target tons per acrefor site of coarse woody debris

Warmer Drier Ponderosa pine 3 -13 tons/acre Forests Douglas-fir 7-14 tons/acre

Grand fir 7-14 tons/acre Western Red Cedar 16-33 tons/acre

Cooler Moister Subalpine fir, western Forests hemlock, spruce 16-33 tons/acre

Note: These are approximate recommendations. For specific recommendations forindividual habitat types, see Graham et al. (1994) in the reference section.1Climax species are the tree species that would dominate a site after a long period offorest succession (100-400 years) with little or no disturbance. On most forested sites,the climax species will be the most shade-tolerant conifer you can find growing in theunderstory at a rate of 10 or more trees per acre.

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Researchers from the USFSRocky Mountain Research Stationused mycorrhizae as a “bio-indica-tor” to determine how much coarsewoody debris was optimal forRocky Mountain forest soils.They looked at many forest sitesand found points of diminishingreturns for coarse woody debris,where mycorrhizal activity leveledout above certain amounts of CWD.Above the upper limit (table 2),additional CWD did not increasemycorrhizal levels.

For the Inland Northwest, thatresearch recommended leavingamounts of CWD ranging fromthree tons per acre in drierponderosa pine forests to 33 tonsper acre in more moist westernhemlock forests. These CWDrecommendations assume stumpsare not removed.

At a minimum, pay closerattention to leaving low value(“cull”) pieces of stem wood in theforest rather than hauling them allto a central location, including themin slash piles, or worse yet, haulingthem to a mill that won’t pay for

them (fig. 21). Measuring howmuch CWD there is on site beforea logging job will provide someguide to how much additional CWDshould be left. See Appendix forinformation on measuring coarsewoody debris tonnage.

Leaving larger logs (24 inches indiameter and larger) is oftenpreferable because they decayslowly, are more likely to surviverepeated fires, and can providehabitat to a wider variety of wildlifespecies than smaller material.Ideally, the material should bedistributed across a site.

Douglas-fir, larch, western redcedar, and pine CWD decay into“red” or “brown” rotted materialwhich provides the longest lastingbenefit (hundreds of years). By con-trast, CWD from grand fir, hemlock,and hardwood species is moreshort-lived because it is decayed by“white rots” (fig. 22). You mayfind stem decay in logs left after aharvest, but removing those logswill not reduce future stem decayin the stand (fig. 23).

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Figure 24. Fire risk from CWD, while minimal, may be reduced by cutting the branchesfrom logs so they lay flat on the ground.

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STRATEGIES FOR MANAGING FIREAND ORGANIC DEBRIS

Fire hazardFine organic debris poses the

greatest fire hazard because it driesrapidly, ignites readily, and burnsquickly and intensely, making firesrunning through it hard to control.Fire risk assessment is based prima-rily on the amount, arrangement, anddepth of fine organic debris createdby a timber harvest or thinning.

Coarse woody debris is not asmuch of a fire risk and in someareas, you can legally leave as muchof it as you like. However, very heavycoarse woody debris loads (morethan 40 tons/acre) may impede firesuppression. Fire risk from CWDmay be further reduced by cuttinglogs’ branches so they lay flat on theground, where they can soak upmore moisture and decompose moreeasily (fig. 24).

Most western states have fire orslash rules that require a landowneror operator to modify or reduceslash to an acceptable level.Landowners who have more slashthan is acceptable may be liable forany forest fires that start on or movethrough the property. These rulesvary from state to state and are oftenstructured differently for slashfrom logging versus slash frompre-commercial thinning or otheractivities. Check with your localstate forestry office for moreinformation on these rules.

The ultimate goal of slashtreatment is not to remove all slash,but to reduce fire hazard. Therefore,the first step in planning slashtreatments is to determine thedegree of slash hazard. The mostcommon measure of fire hazard istons of slash per acre, but slashhazard is more than weight. Otherfactors that determine fire hazardfrom slash include:

• number, size and species of

trees to be cut and resulting

slash load in tons per acre

(a few large pieces present asmaller hazard than many smallpieces even if the tons/acre arethe same);

• depth of the slash (deeper slashhas more fire hazard);

• size of unit (smaller treatmentunits have less fire hazard);

• slope and aspect (steep southor southwest facing slopes aremore hazardous because theydry out sooner and fires onslopes burn with greaterintensity);

• forest structure (for example,the distance from the ground tothe base of the tree crowns);

• condition of the unit and

adjoining areas prior to

activity;• location of the unit relative to

other slash accumulations or

other fuels;• accessibility of the unit --

whether there are campgrounds

20

Figure 26. Your local state forest fireofficials can help you evaluate firehazard and how to reduce it whileretaining nutrients.

Figure 28. Heavy winter snows maycompress slash considerably.

Figure 27. Fire hazard can be reduced bylopping slash into smaller pieces – making itless than 24 inches deep.

Figure 25. Limiting access is one of many waysto reduce fire risk.

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or roads close to the site thatallow more opportunities forhuman ignition (fig. 25);

• proximity to structures such

as homes;• presence of snags and cull trees

(snags ignite easily and can castsparks and fire brands that helpfire spread);

• deterioration rate of slash

(slash close to the soil’s surfacedecomposes more easily andloses its needles or leaves morequickly, making it less of a firehazard than loosely compactedfine fuels with lots of brownneedles); and

• time of year activity takes

place. Fine fuels generated inthe late winter and early springcreate a greater fire hazard thanslash created in the late sum-mer, fall, or early winter. Latewinter and spring fuels can dryand be highly combustible in thesummer and early fall whenthe fire danger is highest.

Before deciding on a slashreduction strategy, contact yourlocal state forest fire official todetermine how much of a firehazard you have, or are likely tohave, from a harvest or thinning(fig. 26). If there is or will be enoughslash to warrant further treatment,there are many methods to reduceslash to acceptable levels. The fol-lowing methods may be used aloneor in combination.

Methods to reduce fire hazardLop and scatter

Relatively small amounts of slashcan be cut into smaller pieces (2 to8 feet in length depending on theirdiameter and limbiness) andscattered so they lay flatter to theground, have more contact with theforest floor, are less than 24 inchesdeep, and are discontinuous so theywould be less likely to carry asurface fire (fig. 27).

This method, commonly referredto as “lop and scatter,” is fairlystandard with pre-commercialthinning slash, but it can also beused for logging slash. Its effective-ness in reducing fire hazard is verysite- and slash-specific, dependingon tree species, amount, location,and piece size.

For the first few months to yearsafter the treatment, there is someelevated fire risk, depending on theforest type, amount of fuels, and theintensity of the treatment. It maynot be too visually appealing tosome landowners either. But afterone winter’s snow, the material isoften compressed, needles fall off,and it is more out of sight (fig. 28).Lopped and scattered slash decom-poses more quickly on moist sitesthan on dry sites.

Pile and burnFor heavier slash loads, lop and

scatter is usually inadequate byitself. The most common approach

22

Figure 29. Piling and burning is themost common approach to reduceslash on family forests.

Figure 30. Dirty piles such as this are difficultto burn.

Figure 31. Leave CWD out of slash pileif possible.

Figure 32. Excavators can separatefine from coarse woody debris moreeasily.

Figure 33. Trees can be injured ifpiles are burned too close to them.

Figure 34. A piece of plastic or roofing paperplaced on top of a pile keeps a portion of it dryfor easier ignition.

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to reduce slash hazard on InlandNorthwest forests is to pile it andburn it (fig. 29). Piles can be createdby hand or by using a dozer or othermachinery. Hand piling is veryappropriate for small areas aroundhomes and other buildings; whereslash loads are light; wheremachines would have difficultyworking because of residual treedensity or steepness of slope; orwhere risk of soil compactionand/or displacement is high.

Slash can be piled with dozers ortractors with rakes (brush blades),but if they are not used carefully,these machines can displace largeamounts of topsoil and forest floormaterial, and leave a lot of soil inslash piles. Piles with a lot of soil inthem (fig. 30) are difficult to burnand can smolder for days and evenmonths after they are ignited. Theymay even provide an ignition sourceinto the next fire season. Dozersalso have difficulty separating fineorganic debris from coarse woodydebris. Tree limbs and boles mayhave to be cut into pieces to facili-tate hand or dozer piling.

Slash can also be piled usingexcavators and other machines witha grapple. Because these machinescan select individual pieces of slashto lift, separate, and pile, they candivide CWD from FOD (fig. 31).Because these machines lift mate-rial, piles have less soil, so they burnmore completely and there is lessrisk of “hold-over fires” (fig. 32).

Pile location is critical so burning

piles do not scorch or damageadjacent homes, buildings, or valuedtrees (fig. 33). Covering a portion ofslash piles with plastic sheeting,roofing paper, or other waterproofmaterial will ensure some drymaterial for easier ignition (fig. 34).Some states have laws regarding thetypes of plastic that can be used forthis purpose and whether it can beburned. Check with your local stateforestry office for applicableregulations. Piles are usually burnedduring the winter or after fall rains,to lessen the chance of firesescaping the piles.

Piling and burning reduces firehazard, but it does have somedownsides. First, it costs time andmoney (especially hand piling),though these costs are usuallyfigured into a logging job thatremoves sawlogs. Second, there issome risk associated with burningpiles, both to trees on the site and tosurrounding forests and buildings,if they are not burned carefully.

Also, depending on the soil typeand its moisture content and pilesize, the soil under the pile can beseverely damaged by heat from thefire. These severely burned areasare often invaded by noxiousweeds such as thistles or spottedknapweed. However, a very smallpercentage of the site is usuallydamaged by pile burning, especiallyif old burning sites are re-used.

Finally, immediately piling freshslash concentrates nutrients in afew piles. Burning those piles

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Figure 35. Letting slash sit one winterbefore treating it retains more nutrients onthe site.

Figure 36. Chipping reduces slash risk butcan be expensive.

25

typically removes much of thosenutrients and organic matterbenefits from the site in the form ofsmoke.

One way to reduce nutrient loss isto let the slash sit one winter beforepiling and burning, to allow morenutrients to leach to the soil(fig. 35). Most states allow someleeway or extensions in which totreat slash before a landowner isheld liable for any fire that movesfrom or through the property. Insome cases, you may also be able toget an extension of this time periodfrom your state forestry office. Besure to ask them about it beforelogging is completed. There will besome extra expense, compared topiling immediately after logging, ifyou have to move equipment backto the site to pile slash.

ChippingChipping involves placing forest

debris by hand or by a mechanicalarm into a chute leading to spinningknives that reduce material topieces 2 square inches or smaller.Chippers are most often pulledbehind a truck or tractor (fig. 36).

Chipping has rarely been used forslash treatment because it is laborintensive and costly. However,there has been renewed interestin chipping, grinding and similartechnologies as a way of creatingbiomass fuel, mulch, or feedstockfor petroleum alternatives.

Chip specifications for these mar-kets can be very stringent as to chip

size, cleanliness, and species. Besure to check with buyers regardingtheir specifications before chipping.Factors such as the quantity andquality of the chips, transportationcosts to the site that uses the chips,and alternative fuel prices also playinto whether removing the chips iseconomically viable. As with burn-ing, there is also potential for somenutrient loss, if chipped fresh fineorganic debris, including greenneedles, is immediately removedfrom the site.

Even if you do not sell the chips,you may still prefer to chip yourslash and leave it on site. Manypeople like the way chipping looks.Local air quality ordinances alsosometimes forbid burning, andchipping on site may be cheaperthan hauling slash to a dump.

Wood chips such as those createdby a chipper do not normally occurin nature. Wood chips dry and weteasily, making it more difficult forfungi and other organisms todecompose them. When chips arepiled or layered, they may retainmoisture and decompose poorlybecause of poor air circulation.These conditions are very familiarto ranchers if they bale or stack wethay and it molds or develops heat(spontaneous combustion), or whensomeone finds mold under their wetcarpet. Fires moving through a layerof chips can produce large amountsof heat, potentially damaging thesoil and any residual vegetation.

26

Figure 37. Keep chipped slash less than 1inch deep.

Figure 38. Leave chips in a mosaic, sothere are areas with no chips. This reducespotential soil impact.

Figure 39. Mechanical slashreduction typically involves sometype of attachment to an excava-tor, a bobcat, caterpillar, or simi-lar machine.

Figure 40. Fine organicdebris can be treatedmechanically, but coarsewoody debris should beleft alone if possible.

27

Layers of chips can also insulatethe forest floor and mineral soil,disrupting heating and coolingcycles, water infiltration, anddecomposition. Avoid burying ormixing the chips in with the soil,because fungi and other organismscompete for and tie up nitrogendirectly from the soil as theydecompose fresh buried chips.

Because chips can act as a mulchand be a poor seedbed, they can beused to suppress unwantedvegetation such as noxious weedsand unwanted shrubs and grasses,or to favor valued vegetation, suchas tree seedlings, deer and elkbrowse, or bird habitat. However,their effect is short lived (from afew months to a couple of years).Chips can also be used on pathsand trails. Chips are not appropriatewithin 100 feet of buildings due tofire risk.

If slash is chipped and left on site,try to keep chips less than 1 inchdeep and distribute them discontin-uously across the site, leaving someareas with no chips, to decreasepotential impacts (figs. 37 and 38).Avoid chipping coarse woodydebris. The fire risk from CWD isrelatively low, and chips do notprovide the same value to forestsoils and wildlife as CWD.

Busting/crushing/shredding/mulching/masticating/grinding/chunking

Many terms are used to describedifferent practices that usemachines to reduce the size andstature of slash, small trees, and

brush so they lay flatter on theground in contact with the soil.Most of the machines used for thishave a rotary or drum power headattached to an excavator, a bobcat,dozer, backhoe, skid-steer tractor,or similar machine (fig. 39). Thecondition of the material aftertreatment depends on the type ofhead used, skill of the operator, andthe amount of time spent in an areaor on a piece of slash.

All of these machines vary in theirmaneuverability in tight stands(some can be used on sites withtrees spaced as close as 12-15 feet),ability to work on slopes, degree ofsoil compaction, and the amount ofsoil they displace. Small machinesand those with the cutting head onthe end of a boom can work close tobuildings and in and among closelyspaced trees.

Most forest owners will hire acontractor to do this work, but somemay be interested in purchasing amachine, particularly machines thatcan do multiple tasks, such asmove snow, skid logs, and digditches. For more information, see“Small Area Forestry Equipment”in the reference section.

These machines can increase theamount of slash less than 3 inchesin diameter, but fire hazard will bereduced if the material is distributedin a patchy pattern across the forestfloor and in direct contact with soil.Avoid breaking up CWD (fig. 40),since this may turn it from low tohigh fire hazard material. If you

28

Figure 42. Using smaller equipment isone way to reduce soil compaction.

Figure 41. Minimizingcompaction preserves soil porespace and ultimately forest growth.

Figure 43. Limit soil displacementwhen treating slash.

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must break up CWD, attempt toleave it in softball- to football-sizedchunks. Also focus on slash thatwas created in the most recententry. Older slash is not counted insome state slash inspectors’ assess-ments, but if breaking up old slashmakes it countable as new slash, thesite may not pass slash treatmentstandards.

Soil compaction and displacementOne of the most important quali-

ties of healthy forest soil is adequatepore space -- the part of the soiloccupied by air and water. Porespace is necessary for tree rootgrowth and feeding, and for benefi-cial fungi and other soil organisms(fig. 41). Pore space is reducedwhen soil is compacted. Piling andburning, slash busting, or chippingmay require moving heavy equip-ment across the site. Covering a lotof ground with repeated trips byheavy equipment risks more soilcompaction.

Potential soil compaction variesby the type of soil and other factors.Ash-cap soils are very susceptibleto compaction, whereas gravelly orsandy soils can be less vulnerableto compaction. Soils with extramoisture may compact more easily.The type of equipment, and thecarefulness of the operator usingthe equipment, can also affectcompaction. Compaction can bereduced by:

• using equipment with lowerground pressure, such assmaller dozers, and tracksinstead of tires (fig. 42);

• working during drier seasonsor on snow or frozen ground;

• limiting traffic by cabling orcarrying slash to the machine;

• using machines mounted on anexcavator arm; and

• operating equipment over slashmats (layers of slash laid downspecifically to drive on).

For more information, see“Soil Compaction on WoodlandProperties,” listed in the referencesection.

Soil displacement is also apotential issue with machines,particularly on very thin soils orsoils with a unique layer, such asvolcanic ash, that is critical to soilfunctioning. Soil displacementoccurs most often when machinesturn and/or twist, pushing the forestfloor and surface mineral layers intofurrows and/or mounds with theirtires or tracks (fig. 43).

Blades, rakes, plows, or otherimplements attached to tractorsused for logging and/or slashtreatments can also displace soils.The more extensive the soil dis-placement, the greater the potentialforest productivity loss. Limit soildisplacement by minimizing bladeor rake use, and operating loggingand slash treatment machines care-fully, especially on steep slopes.

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Figure 44. Broadcast burn Figure 45. Underburn

Figure 46. Burning when the lowerduff layers are moist helps retainnutrients.

Figure 47. Charred CWD will stilldecompose and help soil.

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Prescribed fireFires that are ignited purposely to

treat the forest floor, logging slash,and even standing trees are termed“prescribed fires.” They are ignitedunder “prescribed” fuel and weatherconditions to produce desiredoutcomes. There are many types ofprescribed fires. For example, aftera clearcut, slash is typically broad-cast burned (fig. 44) to consumefiner fuels and char coarse woodydebris, reduce the fire hazard, killunwanted vegetation, create sitesfor seed germination and/or treeplanting, and improve tree planteraccess.

A prescribed underburn takesplace under a canopy of trees andburns up needles, limbs, and othermaterials on the forest floor withoutkilling overstory trees. This reducesfuels or creates bare mineral soil forconifer seed germination (fig. 45).These kinds of low intensityprescribed fires mimic the effectsof surface fires that historically keptfire risk lower and recycled somenutrients.

Prescribed burning alwaysbalances between choosingconditions that allow safe burning(such as time of the year, fuelmoisture, air temperature, windspeed, humidity, expected rainand/or snow) versus conditionsthat are dry enough to get a burnthat meets management objectives.Air quality and atmospheric condi-

tions favorable for smoke dispersalalso determine burn timing.

The science and application ofprescribed fire have dramaticallyimproved. Ideally, prescribed firesburn in a way that protects thenutrient-rich forest floor, leavesthe desired amount of CWD, andminimizes the risk of escape.

“Cool” burns—prescribed burnswhere the temperature is highenough to reduce slash but not hotenough to volatilize all the nutrients—are desirable. When the moisturecontent of the surface organic layersis high, fires do not usually consumethese layers entirely and tempera-tures there don’t exceed 400oC(fig. 46). Above that temperature,nitrogen and other nutrients arevolatilized.

These forest floor and fine slashmoisture levels can occur through-out the year, but they are most likelyduring spring and shortly after fallrains. CWD is not usually consumedunder these moist conditions. It maybe charred, but charred logs haveplenty of cracks, checks, and otheropenings, allowing decaying organ-isms to colonize the wood (fig. 47).

Prescribed fire can effectivelyreduce wildfire hazard, but it canalso damage residual trees andcoarse woody debris. It can alsodamage the forest floor’s nutritionaland biological values, and evenmineral soil, if it is not used care-fully. This is particularly the case in

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Figure 48. Prescribed burning should be implemented by trained professionals.

33

forests that have been without firefor many decades, and deep layersof duff have often developed, espe-cially around the bases of large, oldtrees. Before raking these layersaway from a tree or burning underit, dig into the duff to see if roots arepresent. If they are, be careful withfire and other treatments, as treescould be damaged.

Obviously, prescribed burninghas large risks. If a fire escapes, alandowner can be held legallyresponsible for damage to others’properties and the cost of suppress-ing the escaped fire. Forest ownerswho are considering prescribed fireon their forests should consult withprofessional foresters and firemanagers who are trained andexperienced in assessing the risksassociated with prescribed fireand implementing appropriatesafeguards (fig. 48).

Other methods to help reduce fire riskAll of the fire risk reduction

strategies referred to thus far areways of directly reducing or modify-ing fuels. Other ways to reduce fire

risk that can be used together withthese methods include:

• making water available; • limiting access by gating or clos-

ing roads to reduce the chanceof human ignitions;

• creating fuel breaks, fire trails,or fire lines to limit and isolateslash and pre-existing organicdebris into smaller subunits andbreak up the fuel continuity; and

• creating fuel break buffers alongtravel routes (removing all slashwithin 66 feet of roads).

No strategy will eliminate firerisk completely, especially when firedanger is extreme. But healthy treesand forests are more resistant andresilient to fire, insects, and disease.Evaluate a combination of differentactions and develop a strategythat best fits your site and yourobjectives, to balance betweenreducing fire risk and meeting otherobjectives such as care of forestsoils and wildlife habitat. For on-sitehelp in devising a strategy to reducefire hazards from slash, check withyour local state forest fire official.

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Figure 50. Pine engravers attackponderosa & lodgepole pines.

Figure 51. Pine engraver beetlesleave piles of orange boring dust ingreen boles of ponderosa or lodgepolepine on the ground.

Figure 52. “Y”or “H” shaped galleriesin the cambium confirm the presenceof pine engraver beetles.

Figure 49. Bark beetles from left toright: Douglas-fir beetle, sprucebeetle, pine engraver beetle, and firengraver beetle.

35

STRATEGIES FOR MANAGINGBARK BEETLES AND ORGANICDEBRIS

Some landowners believe theyshould remove all organic debris toreduce problems with bark beetles.Such a preventative mindset iscommendable, but there are manyspecies of bark beetles and only ahandful of them kill trees (fig. 49).Of the tree killers, only a fewspecies breed in fresh slash ordowned trees. Forest ownersshould consider:

• species of trees on the site,and whether a bark beetle thatbreeds in the coarse woodydebris can attack the standinggreen trees;

• the size of the coarse woodydebris and whether bark beetlescan breed in it, successfullycomplete their development,emerge, and attack standingtrees; and

• whether the slash is fresh whenthe bark beetles are looking forhabitat in which to breed.

Pine engraver beetlePine engraver beetle (Ips pini)

(also referred to by its genus name“Ips”) is the most common culpritwhen insects emerge from downedtrees or larger diameter slash toattack and kill standing green treesin the Inland Northwest. Pineengraver beetles and their larvaefeed on lodgepole and ponderosa

pines (fig. 50). They usually focuson sapling to pole sized trees (3- to-8-inch stem diameter) or tops oflarger trees. In the InlandNorthwest, they can produce 2or more generations per year.

Pine engravers usually attack andkill trees within a ½ mile of whereslash with green stemwood hasbeen created from logging or winterstorms. When green pine topslarger than 3 inches in diameter arecreated and left on site betweenNovember and June, Ips beetles willattack that material in the springand breed there. Their progenyemerge later in the summer toattack standing green pines. Piles oforange-red boring dust on the boleson the ground (fig. 51) indicate theirpresence. Peeling away the bark willreveal “Y” or “H” shaped galleriesfrom Ips feeding in the cambium(fig. 52).

To minimize risk from Ips beetles,avoid creating and leaving freshpine tops or bole wood fromNovember through June. One optionis to log on those sites from Julyto October. Usually slash createdduring this time dries out suffi-ciently to be unsuitable for beetledevelopment the following spring,or is colonized by secondary(non-tree-killing) beetles during thesummer.

If you create green slash largerthan 3 inches in diameter fromNovember to June, debark it to

36

Figure 55. Galleries 8-10 inches long,parallel to wood grain, with eggs laidalternately, confirm Douglas-firbeetles.

Figure 54. Douglas-fir beetle is most commonlya problem from large diameter Douglas-fir treesfallen in winter storms.

Figure 53. Debarking green logs will prevent bark beetles from successfullyreproducing in them.

37

remove beetles’ food (fig. 53), burnit, or remove it from the site. Greenstemwood created during winterand spring is often difficult to burn,but to reduce bark beetle hazard,the bark and underlying tissue onlyneed to be scorched to make itunsuitable for beetle development.

Ips prefers slash to standing trees.If you will be logging on a sitethrough the summer, and providingfresh tops through July, the beetleswill move from slash to slash, andeventually overwinter in the slashor forest floor, without getting tostanding trees. This is called leavinga “green chain” for the beetles. Thefollowing spring they will disperseto search out additional freshdowned material and do not usuallyconcentrate attacks in standinggreen trees unless those trees areespecially stressed.

You may see evidence of Ips orother bark beetles in material thatis smaller than 3 inches in diameter.This material usually dries out toosoon for any Ips brood to mature toadulthood, so it is not a bark beetlehazard for the standing trees.

Douglas-fir beetleAs the name implies, the

Douglas-fir beetle (Dendroctonus

pseudotsugae) is a bark beetle thatfeeds predominantly on Douglas-fir(it rarely attacks larch). Douglas-firbeetles attack large diameter stand-ing trees (larger than 12 inches), andgreen debris larger than 8 inches, so

they are usually less of a problem intimber harvests, since trees this sizeare usually taken to a mill shortlyafter they are cut.

Douglas-fir beetle is mostcommonly a problem from treesthat have fallen in winter storms(fig. 54). Beetles will attack thesetrees the following spring, and theirprogeny will emerge a year later toattack standing green trees, mostoften groups of trees. During epi-demic years, larger groups of treesare attacked. The beetles produceone generation per year. Standinggreen trees do not usually turncolor until one year after attack.

If you have recently fallenDouglas-fir trees larger than 8inches in diameter that have beenon the ground less than 1 year,remove, burn, or debark them. Youcan also monitor them for beetleattack. If you see trees on theground this size, with red-orangeboring dust in bark crevices, andupon cutting away the bark findgalleries 8-10 inches long parallel tothe wood grain, with larval minesperpendicular to the main gallery inalternate patches (fig. 55), they havebeen attacked and should beremoved, burned, or debarked.

Spruce beetleSpruce beetle (Dendroctonus

rufipennis) feeds on all species ofspruce. Like Douglas-fir beetle, it ismainly a problem in standing treesand green debris that is larger than

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Figure 57. Fir engraver galleries are 2-4inches long and perpendicular to wood grain,with smaller larval galleries emanating fromthem parallel to the grain.

Figure 58. Wood borers such as flat-headed borers (top) and longhornedborers are often found in CWD butrarely move on to kill green trees.

Figure 56. Spruce beetle galleries run parallel to the wood grain but are generallyshorter and wider than Douglas-fir beetle galleries.

39

12 inches in diameter. Problemscommonly begin when there is alarge amount of wind-thrown greenspruce. Beetles attack the downedtrees and their brood emerge fromthis material 1 or 2 years later toattack standing trees.

Fallen spruce trees larger than12 inches in diameter should beremoved, burned, or debarkedto destroy beetle habitat.Beetle-attacked spruce trees havereddish-brown boring dustaccumulating in bark crevices andon the ground underneath infestedlogs. Spruce beetle galleries aresimilar to Douglas-fir beetlegalleries, but shorter (fig. 56).

Fir engraver beetleThe primary host for fir engraver

beetle (Scolytus ventralis) is grandfir. While this beetle is not com-monly as much of a problem withdowned trees as other beetlesdescribed here, fir engraver beetlesometimes breeds in wind-throwngrand fir and in the tops of grand fir(over 4 inches in diameter) left overfrom logging. Fir engraver beetlesproduce one generation per year,which attack trees from June toSeptember, most often duringperiods of drought.

Not all of the attacks of standingtrees are lethal. More commonly, firengraver beetles simply kill patchesof tree tissue, or kill tops. Outbreakshave never occurred due to popula-tion build-up in wind-thrown treesor logging slash. Outbreaks nor-

mally occur during periods ofdrought or following outbreaks ofdefoliating insects that stress andpredispose trees to fir engraverattacks. However, populations mayincrease enough in downed treesto kill patches of tree tissue ortreetops. Outbreaks can also occuramong root-diseased trees.

During droughty periods, if youhave green grand fir larger than 4inches in diameter on the ground,check under the bark for beetlegalleries. If you find main galleriesscoring the wood perpendicular tothe grain, and larvae galleriesemanating from them parallel to thegrain (fig. 57), remove or debark thestems to eliminate beetle habitat.

Generalizations about bark beetlesand organic debris

A few rules of thumb can bedrawn from the biology of the barkbeetles that breed in green coarsewoody debris:

Trees dead longer than one year

are not a bark beetle hazard. Evenif those trees were at one timeinfested with bark beetles, theirbrood has already left. You willoften find insects in them that aresuperficially similar to bark beetles,but they are not usually insects thatkill trees. The same goes with largelarvae of wood boring insects com-monly found working in dead treesor firewood (fig. 58). These insectsrarely kill trees. In fact, they arebeneficial to forests, because theyhasten the process of decomposing

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Table 3. Tree species, and recommended slash or downed tree treatments to prevent barkbeetle problems

Tree Species Bark beetle Material that must betreated, and how

Material that maybe left for forestsoils and wildlife

Ponderosa pine(Pinus ponderosa)and Lodgepolepine (Pinuscontorta)

Pine engraver(Ips pini)

Do not leave green pineslash larger than 3 inchesin diameter fromNovember to June.Otherwise burn, chip, ordozer-trample the slash.

Pine slash that issmaller than 3 inchesin diameter, createdJuly to October, orthat is more than1 year old.

Douglas-fir(Pseudotsugamenziesii)

Douglas-fir beetle(Dendroctonuspseudotsugae)

Remove or burn greenDouglas-fir slash ordowned trees larger than8 inches in diameterwithin 1 year of creation.Those downed from Mayto July should be takenout before the followingApril.

Douglas-fir stemsless than 8 inches indiameter or morethan 1 year old.

Engelman spruce(Picea engelman-nii)

Spruce beetle(Dendroctonusrufipennis)

Remove, burn, or debarkgreen spruce larger than12 inches in diameterwithin 1 year of creation

Spruce stems lessthan 12 inches indiameter or morethan 1 year old.

Grand fir (Abies grandis)

Fir engraver(Scolytusventralis)

Remove or burn greengrand-fir slash or blown-down trees larger than3 inches in diameter.

Grand fir stems lessthan 3 inches indiameter or morethan 1 year old.

Figure 59. Cutting green stemwood intofirewood-sized pieces does not eliminate itas bark beetle habitat.

41

the dead trees. They also providefood for a variety of wildlife species.

Organic debris less than three

inches in diameter is never a bark

beetle hazard. Occasionally Ips willattack smaller diameter materials,but the material usually dries out,starving the larvae before theydevelop fully.

CWD from some species is never

a bark beetle hazard. For example,there are bark beetles that breed inwoody debris from cedar, hemlock,and larch, but they do not emerge toattack standing trees.

Beyond these types of CWD,hazard from bark beetles dependson the species, the condition of thematerial left on the ground, and thesize and species of the trees in theimmediate area that might beattacked (table 3). For example,Douglas-fir organic debris may beof appropriate size and freshness inthe understory, but if the standinggreen trees left in the immediatearea are all too small or of a

different species (say, ponderosapine), you do not have a potentialbark beetle problem.

A final note: sometimes landown-ers see a green tree that has fallen intheir forest and decide to cut it intofirewood-sized pieces and stack itup in the woods to cure. Cuttinggreen stem wood into firewood-sized pieces has little effect on itssuitability as bark beetle habitat.Bark beetles that breed in downedstem wood will still do this success-fully in firewood-sized pieces (fig.59). If downed stem wood is a largeenough diameter and green enoughto be a bark beetle hazard, removeit or debark it.

For more information on barkbeetles and other forest insects, seethe publications cited at the endof this booklet. For technical assis-tance regarding whether you arelikely to have bark beetle problemsas a result of fallen or broken trees,contact your local state forestryoffice or a consulting forester.

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Figure 60. Pileated woodpeckers and fishers are among the many species thatuse coarse woody debris.

43

STRATEGIES FOR MANAGINGWILDLIFE AND ORGANIC DEBRIS

Plants, animals, insects, and fungihave evolved to take advantage offorest organic debris for food andhabitat. People value these speciesfor their own sake. But even wherethe primary focus is on growingwood fiber, some of the organismsthat benefit from woody debris areimportant for good tree health.Rodents transport mushrooms andspores of mycorrhizal fungi. Birds ofprey make their homes in snags, andthen hunt pocket gophers that mightotherwise kill planted trees.

Slash ultimately helps wildlife tothe extent it enriches forest soils,which in turn feed the plants, trees,and fungi that wildlife depend on.But for the most part, wildlife biolo-gists looking at organic debris focuson coarse woody debris, since it isoften limited in many forests. Inaddition, many species of wildliferely heavily on CWD for differentphases of their life cycles (fig. 60).For example:

• both birds and mammals useCWD as a place to forage forinsects or fungi;

• martens, fishers, bobcats, andblack bears use CWD for densand shelter;

• many small mammals use CWDfor hiding cover and protection;

• small mammals and amphibiansuse logs as protected runways;

• many amphibians benefit from

CWD because it provides acooler, moister habitat withmore stable temperatures forbreeding and other activities;

• birds use CWD for lookout postsand reproductive displays; and

• small-bodied carnivores such asmartens and weasels hunt forsmall mammals that overwinterunder CWD.

Managing CWD for wildlife can becomplicated. The size, distributionand orientation of logs are moreimportant than sheer quantity. Also,different wildlife species have differ-ent habitat needs, some of whichmay conflict. For example, heavylog concentrations may be good forsmall mammals but may limit elkmovement.

Since many if not most wildlifespecies of interest cross propertyboundaries, you also have to factorin what needs are being met, or notbeing met, on adjacent forests. Moreresearch is needed, but three gen-eral strategies related to managingCWD for wildlife are often dis-cussed: snags, log sizes andcharacteristics, and arrangement.

SnagsGreen trees are sometimes blown

down by the wind and immediatelyprovide CWD, but more commonly,dead trees remain standing fordecades, depending on theirspecies, size, cause of death, andtheir local environment. Deadstanding trees are called snags.

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Figure 61. Trees heavilyaffected by insects and diseaseare good snag candidates.

Figure 62. Leaving snags inclumps of trees reduces theirsafety risk.

Figure 64. Hollow logs are particularlyuseful to many wildlife species.

Figures 63. A single- ordouble-grip harvester canbe used to create a snag andstill harvest wood higher inthe tree.

Figure 65.Snags andcoarse woodydebris providethe widestvariety ofhabitat ifthe bark isattached.

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Snags are valuable for a whole hostof wildlife species, and their qualityand quantity are often the firstthings that biologists look for whenevaluating forest wildlife habitatquality.

A hard snag has intact bark andfirm wood. A soft snag has somebark remaining, and wood that isbeginning to decay and soften.Green trees with stem decay alsoprovide habitat for many of thesame cavity-nesting species thatuse snags. Leave some hard snags,soft snags, and green trees that willbe “future snags” (generally thebigger the better), distributed overthe unit. If possible, leave snagsfrom a diversity of tree species.

Many landowners and loggersprefer to leave the least valuabletrees as snags, especially if theyalready show signs of animal use,such as woodpecker activity orcavities. Trees that are alreadyaffected by certain insects anddisease are good candidates forsnags (fig. 61), especially if they areof little value for wood and will notharm adjacent trees.

Snags can be a safety issue forloggers and others who work, play,or otherwise spend time in thewoods, so it is important to beflexible to allow loggers to leavesnags in locations that do notthreaten safety. One way of safelyleaving snags is to leave them inclumps of trees (fig. 62). Anothertechnique, if a site is logged with a

single- or double-grip harvester, isto clip some trees 10-20 feet abovethe ground (fig. 63). This createssnag habitat while reducing loggers’safety risk. If a tree has stem decay,the worst decay is usually in thebottom of the stem. Clipping the topof such a tree may allow the harvestof one or more viable logs from thetop part of the tree.

Coarse woody debris sizeand characteristics

Larger pieces of organic debrisbenefit a wider range of wildlifespecies. For example, a black bearcan den in the hollow stump of alarge, wind-thrown tree. The largerthe log, the longer it will persist,providing habitat for a longerperiod. However, small logs stillbenefit other species. For example,smaller logs often provide foragingopportunities for many wildlifespecies, including bears.

Longer pieces of CWD are alsopreferred because they provide awider range of diameters, in turnbenefiting a wider range of wildlifespecies. Hollow logs, created bydecay from Indian paint fungus, redring rot, and other stem decays, areparticularly useful to many wildlifespecies, such as the pine marten(fig. 64).

Snags and downed logs providethe widest variety of habitat if thebark is attached, since some wildlifespecies will live in the spacebetween the wood and the bark(fig. 65). Take care not to roughen

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Figure 67. Logs lying parallel to slopecontours may be used more by wildlife. Suchlogs will also trap eroding soil on the uphillside.

Figure 66. Log piles provide a complex of snow-free spaces and runways for wildlifeprotection and foraging.

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up snags and CWD during loggingoperations any more than necessary.

Coarse woody debris arrangementThe arrangement of fallen logs

is an issue for some species,particularly small mammals andtheir predators. For example,martens and fishers like logs thatare “jack-strawed” or loosely piledup across the forest floor. When logpiles are covered by snow, theycreate a complex of snow-freespaces and runways that providehabitat for rodents and foragingopportunities for predators (fig. 66).

Log orientation matters too. Logslying parallel to slope contours maybe used more by wildlife than logsoriented up- and downhill, espe-cially on steep slopes (fig. 67).Arranging logs this way also allowssoil and fine organic matter toaccumulate on the uphill side,which traps moisture, hastensdecay, and reduces fire risk.

How much coarse woody debrisfor wildlife?

The amount of CWD to leavedepends on your overall forestmanagement objectives, but wildlifebiologists rarely talk about a sitehaving too much CWD. Someresearchers have suggested that 5-7tons of CWD per acre for ponderosapine forests and 10-15 tons per acreof CWD in mixed conifer andspruce/fir forests will help a widevariety of wildlife species. Otherexperts recommend leaving three tofive logs 12 inches in diameter andat least 8 feet long per acre. Thebest strategy may be to leave avariety of species in various decaystages to benefit a broad range ofspecies. The publications listed inthe reference section of this publica-tion provide more details onmanaging snags and coarse woodydebris for different wildlife species.

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CONCLUSION

Fine and coarse organic debrisare important parts of a healthyforest. Forest and site conditionsvary widely across the InlandNorthwest. Forest owner valuesand goals also vary widely.Therefore, the application of theinformation within this bookletmust be customized for eachunique site and landowner.

For some sites, implementingthe strategies described here mayrequire only slight, inexpensiveadjustments to forest practices.For example, coarse woody debrisobjectives on some sites can be metby simply leaving larger diameterslash pieces and cull log piecesscattered across the site rather thanhauling them all to a slash pile.

On other sites and for otherobjectives, decisions abouttreating organic debris are lessstraightforward, particularly asrelated to fire risk and fine organicdebris. Landowners should balancecarefully between their acceptablerisk, costs, and potential benefitsto plan the best treatment strategyfor each site.

The information in this publica-tion should provide a starting pointto help forest owners and thosewho work with them ask the rightquestions to make decisionstowards keeping forests and wildlifemore healthy and sustainable, whilekeeping risk from fire and insectswithin acceptable limits. For moreinformation on the topics discussedin this publication, see the refer-ences listed on pages 58-59.

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A harvester leaving a snag and removing the merchantablepart of the tree.

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APPENDIX: ORGANIC DEBRISESTIMATES

State forest fire officials andforesters commonly talk about theamount of slash or coarse woodydebris in terms of “tons” or “tons peracre.” Many forest owners are notsure what a ton of slash or coarsewoody debris looks like. Learninghow to measure organic debris cangive you a feel for different debrisamounts. Once you measure it a fewtimes, you may not need to measureas much in the future, especially forCWD, where a fairly wide range ofmaterial is targeted. There are twocommon ways of measuring organicdebris: photo series estimation andtransect sampling.

Photo seriesState forest fire officials and

others who inspect woody debrisand slash loading commonly usephoto series to guide their esti-mates. These are photographs ofa variety of sites with differingamounts, configurations, andcompositions of slash, which arethen measured for their fine organicdebris and coarse woody debrisamounts. With this method, you sim-ply find the photo that most closelymatches what you see on your siteand estimate accordingly. Someseries also rate the fire potential ofthe material shown in each photo(such as rate of spread, intensity,

torching, crowning, and resistanceto control) (fig. 68). These photoseries may be available throughstate forestry departments.

Measuring organic debrisIf you would prefer to measurecoarse woody debris or fine organicdebris directly, you can use theplanar intersect technique (fig. 69).For coarse woody debris, that in-volves counting sound and rottenpieces of wood (above ground) thatintersect 50 or 100 foot transects.

• Logs are rotten if they can bekicked apart. Rotten logs arecounted, but for fewer pointsbecause they weigh less.

• The transect must intersect thecentral axis of the log to countthat log — the transect can’t justcatch the log’s corner (fig. 70).

• Splintered logs are mentallymolded together to estimatediameter (fig. 71).

• If the same piece crosses thetransect more than once it iscounted each time (fig. 72).

• Look above your head forsuspended CWD (fig. 73).

• Snags and stumps are notcounted.

Different weights per acre arethen assigned to each piece of woodaccording to its diameter andsoundness or rottenness, anddepending on whether you do 100

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Figure 68. Photo series are commonly used to estimate slash loads.

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foot or 50 foot transects. Addingthose weights together estimatesthe tons of coarse woody debrisper acre for that transect. Anywherefrom 1-3 randomly placed transectsper acre are then averaged togetherto estimate tons of debris per acrefor the site. Tables 4 and 5 areblank, so you can photcopy and usethem for your estimates. Figure 74shows an example of 3 transects.These log diameters are entered ontable 6.

To be precise, these numbersmust also include a slope correc-tion, but as long as the slope isn’tmore than 50%, it won’t increase theestimate by more than 12%. A highdegree of precision isn’t usuallynecessary for general managementpurposes, because we are typicallylooking at a fairly broad range of

targeted tons per acre of coarsewoody debris.

This method does not countsnags. If your tons per acre seemlow, but you have a lot of snags onthe site, you may be fine, sincesnags will eventually fall and addcoarse woody debris to the site.

Fine organic debris can also bemeasured along these transects, butthe method is tedious. Pieces arecounted in three diameter classes(less than .25 inch, .25 to 1 inch, & 1inch to 3 inches) in the first 6 feet ofthe transect, and added in a similarmanner to the large pieces, toestimate tons of slash per acre.

The planar transect method forslash is used primarily in research.In day-to-day forest practice, photosare most often used to estimateslash.

Figure 69. CWD can bemeasured using transects.

Figures 70. The tape must cross the whole log (left),not just a corner (right) to be counted in a transect.

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Figures 71. Splintered logs are mentally molded together to estimatediameter – this piece would be roughly 5 inches.

Figure 72. If the same piece crossesthe transect more than once it iscounted each time.

Figure 73. CWD that is suspended isalso counted in planar intersects.

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Table 4. Coarse Woody Debris Estimation – 100’ Transects.

Transect #1 Transect #2 Transect #3

Diameter and soundness/rottenness

Tons per acreper piecea

# Pieces Tons per acre

# Pieces Tons per acre

# Pieces Tons per acre

3” sound .4

3” rotten .3

4” sound .7

4” rotten .6

5” sound 1.2

5” rotten .9

6” sound 1.7

6” rotten 1.3

7” sound 2.3

7” rotten 1.7

8” sound 3

8” rotten 2.2

9” sound 3.8

9” rotten 2.8

10” sound 4.7

10” rotten 3.5

12” sound 6.7

12” rotten 5

14” sound 9.1

14” rotten 6.8

16” sound 11.9

16” rotten 8.9

18” sound 15.1

18” rotten 11.3

20” sound 18.6

20” rotten 14

22” sound 22.5

22” rotten 16.9

24” sound 26.8

24” rotten 20.1

26” sound 31.5

26” rotten 23.6

Total tons per acre:

Total tons per acre:

Total tons per acre:

Average tons per acre:

a Values derived from Brown, 1974. Values are for tons/acre on a 0% slope.

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Table 5. Coarse Woody Debris Estimation – 50’ Transects.

Transect #1 Transect #2 Transect #3

Diameter and soundness/rottenness

Tons per acreper piecea

# Pieces Tons per acre

# Pieces Tons per acre

# Pieces Tons per acre

3” sound .8

3” rotten .6

4” sound 1.5

4” rotten 1.1

5” sound 2.3

5” rotten 1.7

6” sound 3.4

6” rotten 2.5

7” sound 4.6

7” rotten 3.4

8” sound 6

8” rotten 4.5

9” sound 7.5

9” rotten 5.7

10” sound 9.3

10” rotten 7

12” sound 13.4

12” rotten 10.1

14” sound 18.3

14” rotten 13.7

16” sound 23.8

16” rotten 17.9

18” sound 30.2

18” rotten 22.6

20” sound 37.2

20” rotten 27.9

22” sound 45.1

22” rotten 33.8

24” sound 53.6

24” rotten 40.2

26” sound 62.9

26” rotten 47.2

Total tons per acre:

Total tons per acre:

Total tons per acre:

Average tons per acre:

aValues derived from Brown, 1974. Values are for tons/acre on a 0% slope.

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Figure 74. Three 100-foot transects.

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Table 6. Coarse Woody Debris Estimation – 100’ Transects.

Transect #1 Transect #2 Transect #3

Diameter and soundness/rottenness

Tons per acreper piecea

# Pieces Tons per acre

# Pieces Tons per acre

# Pieces Tons per acre

3” sound .4 1 .4

3” rotten .3

4” sound .7 1 .7

4” rotten .6

5” sound 1.2

5” rotten .9

6” sound 1.7

6” rotten 1.3

7” sound 2.3 1 2.3

7” rotten 1.7

8” sound 3 2 6.0

8” rotten 2.2 1 2.2

9” sound 3.8

9” rotten 2.8

10” sound 4.7 1 4.7

10” rotten 3.5

12” sound 6.7

12” rotten 5

14” sound 9.1

14” rotten 6.8

16” sound 11.9

16” rotten 8.9

18” sound 15.1

18” rotten 11.3

20” sound 18.6

20” rotten 14

22” sound 22.5

22” rotten 16.9

24” sound 26.8

24” rotten 20.1

26” sound 31.5

26” rotten 23.6

Total tons per acre: 4.7

Total tons peracre: 8.2

Total tons per acre: 3.4

Average tons per acre: 5.4 tons/acre

aValues derived from Brown, 1974. Values are for tons/acre on a 0% slope.

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REFERENCES

For more information on the topicsdiscussed here, please see the referenceslisted below. Most of these are availableonline, and some should be availablethrough your local extension office.

Adams, P.W. 1998. Soil compaction onwoodland properties. Extension Circular1109. Oregon State University ExtensionService, 7 pp. Available online at:http://extension.oregonstate.edu/catalog/pdf/ec/ec1109.pdf

Beckley, B. and K. Windell. 1999. Smallarea forestry equipment. USDA Forest Serv-ice Technical Report 9924-2820-MTDC, 40pp. Available online at:http://www.fs.fed.us/eng/pubs/pdfpubs/pdf99242820/pdf99242820pt01.pdf

Bennett, M. and S. Fitzgerald. 2008. Reduc-ing hazardous fuels on woodland property:disposing of woody material. ExtensionBulletin 1574-E, 5 pp. Oregon State Univer-sity Extension Service. Available online at:http://www.cof.orst.edu/cof/extended/extserv/wildlandfire/DispWoodyMaterialLR.pdf

Brown, J.K. 1974. Handbook for inventory-ing downed woody material. General Tech-nical Report INT-16. USDA Forest ServiceIntermountain Forest and Range Experi-ment Station, 25 pp. Available online at:http://www.fs.fed.us/rm/pubs_int/int_gtr016.pdf

Bull, E.L., C.G. Parks, and T.R. Torgersen.1997. Field guide for the identification ofsnags and logs in the Interior ColumbiaRiver Basin. USDA Forest Service PNW-GTR-390, 55 pp. Available online at:http://www.treesearch.fs.fed.us/pubs/5303

Bull, E.L., C.G. Parks, and T.R., Torgersen.1997. Trees and logs important to wildlifein the Interior Columbia River Basin. USDAForest Service PNW-GTR-391, 40 pp.Available online at:http://www.treesearch.fs.fed.us/pubs/3051

Creighton, J. C. and J. Bottorff. 2000.Habitat management for bats on smallwoodlands. Woodland Fish & Wildlife.Washington State University ExtensionMisc. 0226. 12 pp. Available online at:http://www.woodlandfishandwildlife.org/pubs/bats.pdf

DeCalesta, D. and M. Deusen. 1988. Isthere a place for fish and wildlife in yourwoodland? Woodland Fish & Wildlife.Washington State University ExtensionMisc. 0132. 12 pp. Available online at:http://www.woodlandfishandwildlife.org/pubs/isthereaplace.pdf

Ferrell, G.T. 1986. Fir Engraver. USDA ForestService Forest Insect & Disease Leaflet 13,8 pp. Available online at:http://www.treesearch.fs.fed.us/pubs/11016

Graham, R., A. M. Harvey, M. Jurgensen,T. Jain, J. Tonn, and D. S. Page-Dumroese.1994. Managing coarse woody debris inforests of the Rocky Mountains. ResearchPaper INT-RP-477, 12 pp. USDA ForestService Intermountain Research Station.Available online at:http://www.treesearch.fs.fed.us/pubs/24829

Harvey, A.E., M.F. Jurgenson, M. Larsen,& R.T. Graham. 1987. Decaying organicmaterials and soil quality in the InlandNorthwest: A management opportunity.USDA Forest Service IntermountainResearch Station General Technical ReportINT-225, 15 pp.

Hatz, R. and J. Bottorff. 1991. Managingponderosa pine woodlands for fish andwildlife. Woodland Fish & Wildlife.Washington State University ExtensionMisc. 0158. 12 pp. Available online at:http://www.woodlandfishandwildlife.org/pubs/wfw_ponderosa.pdf

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Helgerson, O.T. & R.E. Miller. 2008. Keepingyour forest soils healthy and productive.Extension Bulletin 2019. Washington StateUniversity Extension, 34 pp. Availableonline at: http://cru.cahe.wsu.edu/CEPublications/eb2019/eb2019.pdf

Holsten, E.H., R.W. Their, and J.M.Schmidt, 1999. The spruce beetle. USDAForest Service Forest Insect & DiseaseLeaflet 127, 12 pp. Available online at:http://www.treesearch.fs.fed.us/pubs/10967

Kegley, S.J., R.L. Livingston, and K.E.Gibson. 1997. Pine engraver, Ips pini(Say), in the Western United States. USDAForest Service Forest Insect & DiseaseLeaflet 122, 8 pp. Available online at:http://www.treesearch.fs.fed.us/pubs/11026

Laudenslayer, W.F., P.J. Shea, B.E.Valentine, C.P. Weatherspoon, and T.E. Lisle(technical coordinators). 1999. Proceedingsof the symposium on the ecology andmanagement of dead wood in westernforests. USDA Forest Service PSW-GTR-181,433 pp. Available online at:http://www.treesearch.fs.fed.us/pubs/6718

Livingston, R. L. 2008. Pine Engraver.Idaho Department of Lands, Insect andDisease No. 1, July 2008. Available onlineat: http://www.idl.idaho.gov/bureau/ForestAssist/foresterforum/jul08/ID_No1.pdf

Morgan, P. & B. Shiplett. 1989.Photographic series: appraising slashhazard in Idaho. Idaho Department ofLands, Boise. 117 pp.

Pederson, R. 1991. Managing small wood-lands for cavity nesting birds. WoodlandFish & Wildlife. Washington StateUniversity Extension Misc. 0160. 5 pp.Available online at: http://www.woodlandfishandwildlife.org/pubs/cavitynestingbirds.pdf

Powers, F.P., D.A. Scott, F.G. Sanchez, R.A.Voldseth, D. Page-Dumroese, J.D. Elioff,and D. M. Stone. 2005. The North Americanlong-term soil productivity experiment;findings from the first decade of research.Forest Ecology and Management. 220, 31-50. Available online at:http://www.treesearch.fs.fed.us/pubs/25278

Schmitz, R.E and Gibson, K.E. 1996. Dou-glas-fir beetle. USDA Forest Service ForestInsect & Disease Leaflet 5; 8 pp. Availableonline at: http://www.forestpests.org/acrobat/fidl5.pdf

Town, P. and R.L. Mahoney. 1996. Evaluat-ing Wildlife Habitat for Managing PrivateForest Ecosystems in the Inland Northwest.University of Idaho Experimental StationBulletin No. 60. 16 pp.

Windell, K. and S. Bradshaw. 2000. Under-story Biomass Reduction Methods andEquipment Catalog. 0051 2826. Missoula,MT: U.S. Department of Agriculture, ForestService, Missoula Technology and Develop-ment Center. 156 pp. Available onlinehttp://www.fs.fed.us/eng/pubs/pdfpubs/pdf00512826/pdf00512826.pdf

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Photo and Illustration Credits

All photos by the authors except:

Mike Amaranthus, MycorrhizalApplications, Inc.: figure 16

Renee Boyles and Sandy Goodson:figure 68. Originally printed inPhotographic Series: Appraising Slash FireHazard in Idaho, by Penelope Morgan andBrian Shiplett. Boise, ID: Idaho Departmentof Lands, 1989, pp. 110-111.

Steve Fitzgerald, Oregon State University:figure 27 (right)

Idaho Fish & Game (© IDFG – Gary Will2005 ): figure 60 (bottom)

Noah Kroese, illustrator:figures 1, 3, 14, 41, 74

R. Ladd Livingston, Idaho Department ofLands (retired): figures 13, 54

Randy Molina, USDA Forest Service(retired): figure 15

Penny Morgan, University of Idaho: figures45, 48.

David Pilz. USDA Forest Service(retired): figure 17

Potlatch Corporation: figure 20

USDA Forest Service Files: figures 8,50-52, 55, 57

Forest organic debris includes tree limbs, boles (trunks), needles, leaves, snags, andother dead organic materials. Common reasons for removing organic debris includereducing fire risk, harvesting forest biomass for energy, reducing bark beetle hazard,preparing a site for tree planting, and aesthetics.

All these issues are important. But forest organic debris left on-site is not necessarilywasted. Organic debris protects soil from excessive moisture loss, recycles nutrientsfor trees and other forest plants, adds structure and organic matter to the soil,reduces soil erosion, and provides food and habitat for a wide variety of wildlife.

Forest and site conditions vary widely across the Inland Northwest. Forest ownervalues and goals also vary widely. Many forest owners are unclear on how to reconcilethe potentially conflicting objectives related to forest organic debris.

This publication outlines the role of forest organic debris in Inland Northwest forestsand provides general management strategies. It will help forest owners and those whowork with them ask better questions to plan the best treatment strategy for each sitein order to keep forests and wildlife more healthy and sustainable, while keeping riskfrom fire and insects within acceptable limits.

Pacific Northwest extension publications are produced cooperatively by the three Pacific Northwest land-grantuniversities: University of Idaho, Washington State University, and Oregon State University. Similar crops,climate, and topography create a natural geographic unit that crosses state lines. Since 1949, the PNW programhas published more than 550 titles, preventing duplication of effort, broadening the availability of facultyspecialists, and substantially reducing costs for the participating states.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by University ofIdaho Extension, the Oregon State University Extension Service, Washington State University Extension, and theU.S. Department of Agriculture cooperating.

The three participating extension services offer educational programs, activities, and materials without regardto race, color, national origin, religion, sex, sexual orientation, age, disability, or status as a disabled veteranor Vietnam-era veteran, as required by state and federal laws. University of Idaho Extension, Oregon StateUniversity Extension Service, and Washington State University Extension are Equal Opportunity Employers.

Published March 2009 $7.00

Managing Organic Debris for Forest HealthReconciling fire hazard, bark beetles,wildlife, and forest nutrition needs