Forest Service 

Pacific Northwest to Wildlife in the Interior Research Station 

General Technical 

Report 

PNW-GTR-391 Columbia River Basin 

May 1997 

Evelyn L. Bull, Catherine G. Parks, and 

Torolf R. Torgersen 
AUTHORS

EVELYN L. BULL is a research wildlife biologist, CATHERINE G. PARKS is a research plant pathologist, and TOROLF R.

TORGERSEN is a research entomologist, Pacific Northwest Research Station, Forestry and Range Sciences Laboratory, 1401

Gekeler Lane, La Grande, Oregon 97850-3399.
c1.

Trees and Logs Important

to Wildlife in the Interior

Columbia River Basin

Evelyn L. Bull, Catherine G. Parks, and Torolf R. Torgersen

Companion to General Technical Report

PNW-GTR-390

Published by:

U.S. Department of Agriculture, Forest Service

Pacific Northwest Research Station

General Technical Report PNW-GTR-391

May 1997
ABSTRACT

Bull, Evelyn L.; Parks, Catherine G.; Torgersen, Torolf R. 1997. Trees and logs important to wildlife in the interior

Columbia River basin. Gen. Tech. Rep. PNW-GTR-391. Portland, OR: U.S. Department of Agriculture, Forest Service,

Pacific Northwest Research Station. 55 p.

This publication provides qualitative and quantitative information on five distinct structures: living trees with decayed parts,

trees with hollow chambers, trees with brooms, dead trees, and logs. Information is provided on the value of these structures to

wildlife, the decay or infection processes involved in the formation of these structures, and the principles to consider for

selecting the best structures to retain.

Keywords: Broom rust, cavity nesters, decay fungi, dwarf mistletoe, Elytroderma, forest management, habitat monitoring,

hollow trees, interior Columbia River basin, logs, old-growth forests, snags, wildlife, wood decay.
CONTENTS

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INTRODUCTION

LIVING TREES WITH DECAY

Ecological Processes and Functions

Decay Process

Selecting Trees

Review

HOLLOW TREES

Ecological Processes and Functions

Decay Process

Selecting Hollow Trees

Review

BROOMED TREES

Dwarf Mistletoes

Broom Rusts

Elytroderma Disease

Review

DEAD TREES

Ecological Processes and Functions

Decay Process

Selecting Snags

Snag Longevity

Sampling Techniques

Creating Wildlife Trees

Review

LOGS

Ecological Processes and Functions

Decay Process

The Log Resource

Review

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Appendix A: Data Form for Monitoring Created Snags

Appendix B: Data Form for Surveying Logs

Appendix C: Methods for Log Inventories
This page left blank intentionally
INTRODUCTION 

More than 80 species of birds, mammals, reptiles, and 

amphibians use living trees with decay, trees with brooms, 

hollow trees, snags, and logs in the interior Columbia River 

basin. Animals use these structures for foraging, nesting, 

denning, roosting, and resting. Most notable of these woodusing wildlife species are the primary cavity nesters, the 

woodpeckers and nuthatches, that excavate nest cavities in 

decayed wood in standing trees. Their vacated cavities are 

subsequently used by many other birds and mammals. 

About 25 percent of the bird species nesting in the northern 

Rocky Mountain forests are cavity nesters (McClelland and 

others 1979). Many of the primary and secondary cavitynesting birds eat forest insects and thus play an important 

role in regulating their populations. Machmer and Steeger 

(1995) provide a thorough review of the effect these birds 

have in reducing numbers of tree-feeding insects. 

Tree decay is an important ecological process affecting 

wildlife habitat. Once begun, the decay process can take 

hundreds of years as a tree dies, falls to the ground, and 

decomposes into the forest floor. As it decays, the tree 

supports many different wildlife groups that use it for 

foraging substrate, for nesting, and for shelter. The group of 

wood decomposers is diverse. It includes many arthropods, 

but in this publication, we focus on decay fungi as the 

primary organisms in decay. Decay fungi are an essential 

resource to forest ecosystems in storing and retaining 

nutrients and in soil development. 

This publication provides managers with a description of 

the ecological processes that create wildlife trees, snags, and 

logs. It provides qualitative and quantitative information on 

five distinct structures: living trees with decay (such as 

internal decay), hollow trees, trees with brooms (misshapen 

branches), dead trees (snags), and down woody material 

(logs). We describe the value of these structures to wildlife, 

the decay or infection processes that produce each type of 

structure, principles to help in selecting the best structures to 

retain, and management implications. Although this document cannot prescribe the amount of landscape to manage 

for a particular species or a specific, desired population size, 

it does present information managers can use to make 

informed decisions regarding the conservation and enhancement of dead wood structures most valuable to wildlife. 

Forest management practices that fail to properly manage 

wood components may adversely affect wildlife, soil and 

stream quality, and forest ecosystem functions. 

The information included here applies to coniferous 

forest lands in the interior Columbia River basin: the area 

east of the crest of the Cascade Range in Oregon and 

Washington, all of Idaho, and a portion of western Montana 

(fig. 1). Tree species characteristic of high-elevation forests, 

(such as whitebark pine [Pinus albicaulis], alpine larch 

[Larix lyallii], mountain hemlock [Tsugu mertensiunu], and 

Pacific silver fir [Abies umubilis]) are excluded because they 

typically grow where active management for wildlife trees is 

seldom needed; these areas are seldom logged. Most of the 

tree species we deal with here are conifers, although black 

cottonwood (Populus trichocurpu), quaking aspen (Populus 

tremuloides), and paper birch (Betulu pupyrzfjkru) are 

--- 

I 

Figure l-The interior Columbia River basin. 

1 
included because they commonly occur in managed conifer

forests.

Additional information on how to distinguish among

different species of snags and logs is provided in a companion document (Parks and others, in press) specifically

designed to be used in the field.

2
LIVING 

WITH 

TREES 

DECAY 

Ecological Processes and Functions 

Although dead, standing trees (snags) are important to 

many wildlife species, living trees may contain decayed 

wood that allows them to function as snags. Living trees 

with an internal core or pockets of decay, top dieback, 

broken tops, or wounds all can serve as wildlife habitat (fig. 

2). Living trees with dead portions typically stand longer 

than snags do, but the portion of the tree suitable for use by 

snag-dependent wildlife may be smaller than in a snag of the 

same size. Although hollow trees are alive, but with 

advanced internal decay, we treat them separately because 

they offer unique structural features and provide for specialized wildlife use. 

Some woodpeckers select living trees with decayed 

heartwood because they can penetrate through the sound layer 

of sapwood and excavate the nest chamber in the softened 

heartwood (fig. 3) (McClelland and others 1979, Parks and 

others 1996a). Typically, the sapwood remains relatively intact 

for a long time, forming a shell surrounding the decaying 

heartwood, so the excavated interior may retain a desirable 

shape for nesting for many years. Woodpeckers commonly 

nesting in decayed wood in living trees in northeastern Oregon 

include the Williamson’s (Sphyrapicus thyroideus) and rednaped sapsuckers (S. nuchalis) and black-backed woodpeckers 

(Picoides arcticus) (Bull 1986). Living trees with heart rot are 

a required habitat component for the red-cockaded woodpecker 

(I? borealis), a widely known and rare species from the 

Southern United States. This woodpecker selects pines older 

than 80 years that are infected with the heart-rot fungus 

Phellinuspini to excavate its cavities (Conner and Locke 1982, 

Hooper and others 199 1). 

Trees with large dead branches or dead tops (fig. 4) 

provide a distinctive habitat in the living forest canopy 

(Parks and Shaw 1996). Cavity nesters such as the whiteheaded woodpeckers (Picoides albolarvatus) commonly 

roost in dead tops of living trees (Dixon 1995). Dead tops 

provide good resonating towers from which drumming 

woodpeckers proclaim their territorial boundaries and 

provide hunting perches for raptors. Living trees with 

broken tops also may provide nesting platforms for raptors. 

Any wounding or scarring of the living tree can result in 

localized dead, decaying wood (fig. 5). Decaying wood, 

particularly at the base of the living tree, is often colonized 

by ants. Pileated woodpeckers (Dyocopus pileatus) forage 

3 
Figure 3-Longitudinal section of a nest cavity excavated m a lodgepole pine hy a hlackbacked woodpecker. Heartwood is softened by heart-rot fungi. 

Figure 2-Woodpecker nest cavities are often in brokentopped living trees that contain decayed wood near the break. 

Figure &Woodpecker nest cavity excavated m the dead top of a 

living ponderosa pine. 

Figure 5Scars caused by lightning or other injuries are frequently 

used by woodpeckers for foraging. 

4 
on ants at these sites, as documented in a study that found 18 

percent of foraging by these birds is in living trees (Bull and 

Holthausen 1993). 

Decay Process 

Wood decay is caused by fungi that decompose the cell 

wall. Wood decayers can be separated based on whether a 

fungus survives primarily in the heartwood of living trees or 

primarily in dead trees or in logs. Generally, the decay fungi 

in upper stems of living trees are heart-rot fungi (Manion 

198 1). The decay fungi of dead trees and logs are 

saprophytic fungi. Although every tree species is susceptible 

to at least one heart-rot fungus, few fungi can cause heart-rot 

in living trees. Conversely, many decay fungi can survive on 

dead branches of living trees, or inhabit a tree once it dies. 

Heart-rot fungi are spread by airborne spores produced by 

fruiting bodies--either conks or mushrooms. The spores 

colonize freshly exposed wood at wounds or dead branch 

stubs. Although spores of heart-rot fungi are abundant in 

forest stands of all ages, old-growth stands have a much 

higher incidence of heart rot than do young stands (Manion 

1981). The amount of heartwood is age related; older trees 

have a higher ratio of heartwood to sapwood than do 

younger trees (Gartner 1995). Decay in the heartwood may 

continue to increase in diameter as the trees grow and new 

layers of heartwood are added (Rayner and Boddy 1988). 

Internal decayEvery living tree is composed of tissues 

that perform specific functions; decay in stems of living trees 

is closely linked to wood anatomy (fig. 6). The sapwood and 

heartwood offer different microhabitats and nutritional 

substrates for decomposer organisms. Typical heartwood has 

no living cells, is nonconductive, and develops in the oldest 

wood; sapwood has some living cells, is conductive, and 

occupies the outer sheath of wood around the stem, or the 

entire wood cylinder of a younger tree (Sperry 1995). In 

contrast to dead sapwood, which decays readily, live sapwood generally is resistant to decay partly because of its 

high moisture content and reduced aeration. Live sapwood 

may remain free of infection for many years, even when 

neighboring sapwood or heartwood is extensively decayed 

(Shain 1995). 

The decay process of dead tops and other dead wood in 

the living tree, typically associated with dieback or wounding, is the same as in dead trees, described later in this report. 

Selecting Trees 

Decay in living trees is not always apparent, but certain 

characteristics can indicate its presence. Conks (fungal 

fruiting bodies) are evidence of heartwood decay, although 

fruiting bodies may not always be present in trees decayed 

by heart-rot fungi. Some fungi tend to fruit only on fallen or 

cut trees and produce fruiting bodies on living trees only 

rarely. Generally, fruiting bodies of heart-rot fungi are found 

close to branch stubs or living branches and are few compared to the numbers of fruiting bodies of sapwood-decaying 

or saprophytic fungi, which may be found in groups over the 

whole stem surface of dead trees and logs. 

Most tree species are susceptible to only a few heart-rot 

fungi. Ponderosa pine (Pinus ponderosa) is commonly 

associated with red ring rot caused by Phellinus pini (fig. 7). 

This fungus also may be found fruiting on lodgepole pine 

(Pinus contorta), western white pine (I? monticola), western 

larch (Lark occidentalis), and Douglas-fir (Pseudotsuga 

menziesii) in some areas. Internal decay in grand fir (Abies 

grandis), subalpine fir (A. Zasiocarpa), and mountain 

hemlock often is indicated by conks of the Indian paint 

fungus (Echinodontium tinctorium) (figs. 8 and 9). Indian 

paint fungus causes a characteristic stringy decay that can 

involve the entire tree trunk (fig. 10). Internal decay of 

western larch and occasionally ponderosa pine is indicated 

by the fruiting body of the brown trunk rot caused by 

Fomitopsis ofjcinalis (fig. 11). Internal decay in quaking 

aspen and paper birch is most often associated with Phellinus 

tremulae (fig. 12) and P igniarius, respectively. Depending 

on climate, elevation, and other local conditions, fruiting 

bodies may be occasional or abundant. Hepting (1971) 

provides a complete list of the decay fungi associated with 

forest trees in the United States. 

In the absence of fruiting bodies, obvious wounds are the 

next best indicators of internal decay in living trees. Wounding is fundamental to decay because germinating fungal 

spores cannot penetrate intact bark or living sapwood. 

Spores usually must land on exposed dead wood directly 

connected with the heartwood for decay to result (Boyce 

1938). Broken tops, fire or lightning scars, or mechanical 

damage from harvest activities all may be good indicators of 

incipient or advanced internal decay. Sixty-two percent of 

133 woodpecker nests in living trees had broken tops, and 17 

percent had dead tops (McClelland and others 1979). All 

nests were associated with internal decay. Forty-four percent 

of the paper birch and 22 percent of the quaking aspen with 

nest cavities had fruiting bodies (McClelland 1977). 

Cambium 

BarkJ-Heartwooc 

Figure 6-Wood anatomy showing the relation of sapwood and heartwood, 

each of which provides specialized substrates used by different microorganisms (modified from Brown and others 1949). 

5 
Review 

l A living tree may contain decayed wood that provides 

special wildlife use. 

l Dead tops, large dead branches, broken tops, and 

wounded areas provide useful habitat in living trees. 

l Living trees containing a decayed column of heartwood 

may stand longer than dead trees and can provide habitat 

for cavity nesters. 

l Fungi that are specialized decomposers and decay the 

heartwood of living trees are heart-rot fungi. Fungi that 

are generalist decomposers are usually found only on dead 

parts of trees, snags, or logs and are saprophytic fungi. 

l Conks indicate decay within the tree. Heart-rot fungi can 

be distinguished from saprophytic fungi by the appearance 

of their conks. In the absence of conks, broken tops, 

wounds, and scars also are indicators of decay in living 

trees. 

Figure 7-Fruiting bodies of red ring rot are hoof-shaped or flat on bark, 

dark brown on the upper surface, and cinnamon to tan on the lower surface 

and in the interior. This conk indicates internal decay, which is stringy with 

pronounced white pockets. Infected trees may have punk knots on the stem. 

Figure s-Fruiting bodies of Indian paint fungus are hoof-shaped and 

commonly located under a branch or branch stub. 

6 
Figure 94onks of Indian paint fungus have a brown woody upper surface 

with teeth projecting downward on the lower surface. The interior is 

orange. 

Figure ll-Frmtmg bodies of brown trunk rot are hoof-shaped or cylmdric 

with a chalky consisiency. The upper surface is yellow, white, or cream, and 

the under surface is yellow or white with a pored texture. The ftmgus causes a 

brown cubical decay. White felts may be found in shrinkage cracks of decayed 

wood. 

Figure l&The decay caused by Indian paint fungus is restricted to the 

heartwood of the tree, and older trees often become hollow. Advanced decay 

is stringy and reddish brown to yellow. 

Figure 12-Fruiting body of Phellinus rremulae on quaking aspen 

7 
8
HOLLOW TREES 

Ecological Processes and Functions 

We define a hollow tree as a tree having decay in the 

heartwood so advanced that it leaves a hollow core. Largediameter trees, those more than 20 inches in diameter at 

breast height (d.b.h.), form hollow chambers most useful to 

wildlife. 

The importance of hollow trees to wildlife has only 

recently been recognized. Hollow trees with broken tops are 

used by black bears (&us americanus) for den sites 

(Akenson and Henjum 1994, Hamilton and Marchinton 

1980, Noble and others 1990, Parks 1996a). These arboreal 

dens provide females and subadults with sites that are safe 

from predaceous, large, male bears. Hollow chambers at the 

bases of some trees also are used as den sites (fig. 13). 

Pileated woodpeckers use hollow trees for roosting at 

night (Bull and others 1992); they excavate their own 

entrance holes to the hollow chambers and do not depend on 

broken tops for access. Entrance holes excavated by the 

woodpeckers allow other species to enter, such as flying 

squirrels (Glaucomys sabrinus), bushy-tailed woodrats 

(Neotoma cinerea) (fig. 14), bats (Nagorsen and Brigham 

1993) American martens (Murtes americana), northern 

flickers (Coluptes uurutus), and Vaux’s swifts (Chueturu 

vuuxi) . 

Martens frequently use hollow trees for derming, as well as 

for resting and hunting (Bull 1995) (fig. 15). Use of such trees 

provides dry rest sites during inclement weather. Vaux’s swifts 

must have hollow trees for both nesting and roosting in forests 

(Bull and Collins 1993) (fig. 16). Swifts readily enter these 

trees, either through an open top or through an entrance hole 

excavated by a pileated woodpecker. 

Decay Process 

A hollow tree is created when heart-rot fungi invade the 

heartwood of a living tree, and decay progresses to the point 

that the cylinder of decayed heartwood eventually detaches 

from the sapwood and slumps downward, leaving a hollow 

chamber. This process begins only in a living tree and can take 

many decades to produce a chamber large enough for wildlife to 

use. Because this particular decay process is dependent on 

living trees, the only way to obtain a hollow dead tree or log is 

to start with a living tree hollowed out by decay. 

9 
Heart-rot fungi do not typically kill trees, but trees with

advanced heart rot often have broken tops because the

hollow interior weakens the bole. Because the trees are

living, a bayonet top may form where new leaders grow

around and over the broken top forming an umbrella of

foliage (figs. 17 and 18). Hollow trees provide valuable

wildlife habitat for decades before they eventually die and

become hollow snags (fig. 19) or fall over as hollow logs

(fig. 20).

Selecting Hollow Trees

No artificial means to create or encourage the formation

of a hollow tree structure has been found, so retaining such

trees in managed stands is essential to providing habitat for

the species that depend on them. Large-diameter trees that

show some evidence of being hollow are of the greatest

value. In the absence of apparently hollow trees, large trees

of the species most commonly producing this structural

feature, such as grand fir and western larch, should be

conserved.

A large-diameter tree is vital because the chamber

typically consists only of the former heartwood. To be most

useful, the chamber must be large enough for a swift to fly

up and down, for a pileated woodpecker to enter; or for a

bear to occupy. All of these wildlife species typically use

entrances from 30 to 80 feet off the ground, where the

heartwood cylinder needs to be large enough to provide a

chamber of suitable size. The average size of 21 trees used

by swifts for nesting was 27 inches d.b.h. and 85 feet in

height in northeastern Oregon (Bull and Collins 1993). Bear

dens’in hollow trees with top entries averaged over 43 inches

d.b.h. and 57 feet tall in northeastern Oregon (Akenson and

Henjum 1994). Pileated woodpeckers roosted in hollow

trees that averaged 28 inches d.b.h. and 74 feet tall in

northeastern Oregon (Bull and others 1992).

Evidence that large-diameter trees have hollow interiors

includes the following:

l A broken bole with a bayonet top formed over the break

(figs. 17 and 18)

l More than one pileated woodpecker entrance hole

l Fruiting bodies of Indian paint fungus (fig. 8)

l An old injury or bend along the bole where a new leader

formed a new trunk many years ago.

In northeastern Oregon, grand fir and western larch make

up most of the hollow trees used by wildlife. All 56 nest and

roost trees used by swifts were grand fir (Bull 1996a). Sixtyone percent of 123 pileated woodpecker roost trees (Bull and

others 1992), and 8 of 10 arboreal bear dens were in grand

fir as well (Akenson and Henjum 1994). The remainder of

hollow trees used by pileated woodpeckers or black bears

were primarily western larch and a few ponderosa pine. We

suspect hollow chambers may be common in old western

redcedar (Tsuga plicata) in the interior Columbia River

basin, because hollows caused by heart rot in old western

redcedar trees are used by pileated woodpeckers for roosting

in western Washington (Parks and others 1997) and in the

Oregon Coast Range (Mellen 1987).

Although lodgepole pine, Douglas-fir, subalpine fir,

Engelmann spruce (Picea engelmannii), and western white

pine are subject to heart rot, they seldom form a hollow

chamber. These species should not be retained with the

expectation that they might produce hollow trees.

Information on the number of hollow trees to retain for

wildlife use is limited. Bull and others (1992) suggest

leaving 44 grand fir roost trees (0.07 per acre) known to be

hollow or 880 grand fir trees (1.47 per acre) suspected of

being hollow in each 600-acre pileated woodpecker management area to provide trees for roosting. No models have

been developed to predict the portion of hollow stem, based

on the presence of conks alone, in large-diameter, living

grand fir.

Large, hollow trees are uncommon in managed landscapes and typically are found only in late- and old-seral

stands of grand fir and western redcedar. Although isolated

hollow trees in young stands have significant value to

wildlife, these young stands cannot reproduce this type of

structure for at least 150 to 200 years. The late-seral,

multilayer stands that produce hollow trees comprise less

than 3 percent of the forested landscape in the interior

Columbia River basin (Hann and others, in press). Retaining

all hollow trees in managed landscapes can be justified in

most areas because so little of the landscape has them, they

have little commercial value, and they are of great value to

wildlife. Rarely, where large blocks (in excess of 600 acres)

of this habitat have many hollow trees (in excess of 10 per

acre), does the number of hollow trees probably exceed the

wildlife need for habitat.

Review

l A hollow tree is created by heart-rot fungi. This kind of

decay initiates only in a living tree.

l Evidence that a tree has a hollow interior includes a

broken bole with a bayonet top, more than one pileated

woodpecker cavity, fruiting bodies of Indian paint fungus,

or an old injury or bend along the bole where a new leader

formed a new trunk many years ago.

l Hollow trees are known to be used by pileated woodpeckers, northern flickers, Vaux’s swifts, American martens,

flying squirrels, black bears, bats, bushy-tailed woodrats,

and other small mammals as dens, roosts, nests, forage

sites, and shelter.

l Large-diameter hollow trees provide the best wildlife

habitat; the mean d.b.h. of hollow trees used by black

bears was 43 inches; by pileated woodpeckers, 28 inches;

and by Vaux’s swifts, 27 inches.

l Tree species that most commonly form hollow interiors

are grand fir, western larch, and western redcedar.

l Retaining all hollow trees in managed landscapes can be

justified in most areas because these trees are uncommon,

occur on less than 3 percent of the landscape, have little

commercial value, and have great wildlife value.

10

i
Figure 13-Black bear sow and cub m a wmter den In the base of a livmg 

grand fir. 

Figure l&Entrance holes are excavated by ptleated woodpeckers Into 

hollow trees, allowing access by bushy-tailed woodrats and other wildlife. 

Figure 15-American martens use hollow trees for denning and shelter Figure 1 &-Vaux’s swifts both nest and roost in hollow trees. 

11 
Figure 17-Broken tops are common in hollow living trees. One or more 

bayonet tops often form over the break. 

Figure 18-A 350-year-old hollow grand fir used as an arboreal den site 

by black bears. The bayonet top is more than 80 years old. 

Figure 2&Hollow logs originate only from living trees that were colomzed by heart-rot 

fungi. 

Figure W-Hollow dead trees originate only from living trees in 

which the heartwocd chamber has been decayed by heart-rot fungi. 

12 
BROOMED ‘REES 

The dense misshapen branches of witches’ brooms 

sometimes found in conifers, provide unique wildlife habitat 

in interior Columbia River basin forests. Brooming is most 

often caused by the dwarf mistletoes (Arceuthobium spp.), 

rust fungi (Chrysomyxa spp. or Melampsorella spp.), or a 

needle cast fungus (Elytroderma deformans). These three 

groups of organisms will be discussed separately. 

Dwarf Mistletoes 

Ecologicalprocesses and functions-Dwarf mistletoes 

are perennial parasitic plants that derive water and nutrition 

from their hosts (figs. 21-26). Most dwarfmistletoes are 

host-specific, but trees of all ages can be infected. Dwarf 

mistletoes typically produce spindle-shaped branch swellings 

at the point of infection. A few years after infection, dwarf 

mistletoes produce distinctive shoots on swollen branches 

that become witches’ brooms after several years. Over many 

years, infection will increase on individual trees and within 

stands. Heavily infected trees grow more slowly in diameter 

and height than do lightly infected or uninfected trees. 

Heavily infected trees produce fewer cones and seeds and 

often develop spike tops. Eventually, heavily infected trees 

die. The most commonly affected tree species in interior 

Columbia River basin forests are Douglas-fir, lodgepole 

pine, ponderosa pine, and western larch (Hawksworth and 

Wiens 1996). 

Trees infected with dwarf mistletoes can be directly or 

indirectly beneficial to wildlife. Wildlife species consume 

mistletoe shoots and fruits, forage for insects in mistletoe 

plants and brooms, and use witches’ brooms for cover and as 

nesting sites (Hawksworth and Wiens 1996, Mathiasen 

1996). Dwarfmistletoes cause openings and changes in 

stand structure by killing trees (Nicholls and others 1984). 

The shape, size, and position in the tree of dwarf mistletoe brooms differ considerably and influence their potential 

wildlife use. The characteristic shape and size of brooms 

depend on where and how they form along the bole. Three 

types of brooms are recognized (Tinnin and Knutson 1982, 

1985). 

Brooms that form platforms are best suited to raptors for 

nesting. Brooms are habitual nest sites for northern spotted 

owls (Strix occident&is) (Forsman and others 1984, Martin 

and others 1992), long-eared owls (Asio otus) (Bull and 

others 1989), goshawks (Accipiter gentilis), and Cooper’s 

13 
klgure ?I-Douglas-11r dwarl ml5tlctoe may form large, drooping 

brooms. Brooms are generally more abundant m the lower crown. 

Figure 23-Dwarf mistletoe brooms on lodgepole pine 

Figure 22-The aerlai shoots o! Douglas-fir debar! mlsllc~oc: ale 

smaller than the host needles (0.5 to 0.75 Inches) and may not 

always be present on broom branches. 

Figure 2LCOpen brooms and distorted branching caused by dwarf 

mistletoe on ponderosa pine. 

14 
Figure 25-Aerial shoots of dwarf mistletoe often are present on infected 

ponderosa pine. 

hawks (Accipiter cooperii) (Reynolds and others 1982). 

Some song birds also nest in witches’ brooms (Hawksworth 

and Wiens 1996). 

Long-eared owls nest on platforms of Douglas-fir dwarf 

mistletoe (Arceuthobium doughsii) brooms that average, 14 

by 19 inches in diameter, with an average depth of 9 inches 

(Bull and others 1989). Douglas-fir brooms used by great 

horned (Bubo virginianus) and great gray owls (&-ix 

nebulosa) exceed 3 feet in diameter (Bull 1996b). Brooms 

selected by northern spotted owls are usually the larger and 

denser brooms located away from the stand edge (Martin and 

others 1992). The specific structural characteristics of 

brooms associated with nests of other wildlife species have 

not been documented and warrant further investigation. 

Witches’ brooms caused by Douglas-fir dwarf mistletoe 

commonly are used by blue grouse (Dendragapus obscurus) 

for roosting cover (Martinka 1972, Stauffer and Peterson 

1986), and they eat mistletoe seeds (Seversen 1986). 

The shoots of ponderosa pine dwarf mistletoe (A. 

campylopodum) are an important fall and winter food for 

porcupines (Erethizon dorsatum) (Hooven 197 1, Lawrence 

1957). Chipmunks (Tumius spp.) commonly eat mistletoe 

seeds (Broadbooks 1958, Nicholls and others 1984). Squirrels and porcupines feed selectively on mistletoe-infected 

twigs in preference to uninfected twigs (Johnson and Carey 

1979, Wood and others 1985) and use the brooms as winter 

resting cover (Smith 1982). American martens use brooms 

in lodgepole pine (Burnett 198 1, Buskirk and others 1987, 

Figure 26Western larch wth dwarf mistletoe brooms prowde 

good nesting platforms that raptors use. 

Campbell 1979, Spencer 1987) Douglas-fir, and western 

larch (Bull 1995) for resting sites. 

Although these plants have a high nutritive value (Umess 

1969), they are usually too high in the trees to be accessible 

to deer and elk, which eat shoots that fall to the ground, 

however. Mistletoe shoots are a regular component in mule 

deer diets (Leach and Hiele 1957, Wright and Arrington 

1950) and can provide a high-protein winter food for elk 

(Craighead and others 1973). Clary and Larson (1971) 

found that in certain years, ponderosa pine stands with dwarf 

mistletoe sheltered significantly more deer than stands 

without dwarf mistletoe. 

Dwarfmistletoes are a natural part of the Northwest 

forest ecosystems; they have coevolved with their hosts for 

millions of years (Hawksworth and Wiens 1996). Dwarf 

mistletoes should be valued and recognized as a functional 

and beneficial wildlife resource. Bennetts and others (1996) 

found a direct positive correlation among the intensity of 

dwarf mistletoe and the diversity and total number of birds in 

ponderosa pine stands. They also demonstrated a positive 

correlation between numbers of snags and intensity of dwarf 

mistletoe infection. Nearly three times as many cavitynesting birds were found in heavily infested stands as in 

comparable uninfested stands. 

Infection process-Dwarf mistletoes spread from tree to 

tree by way of an explosive fruit mechanism. Fruits produced on female plants contain one seed that is forcibly 

expelled during late summer or fall. Seeds are coated with a 

15 
sticky substance that allows them to adhere to objects they

strike. Seeds that land on susceptible trees can cause new

infections. Seeds usually land within 20 feet from their

origin, as a consequence, the spread of dwarf mistletoes is

relatively slow (only 1 to 2 feet per year). Spread from tree

to tree and spread in individual trees is more rapid in forests

with multistoried structures (Parmeter 1978).

Birds and mammals can pick up the sticky seeds on their

bodies and transport them to new infection sites

(Hawksworth and others 1987, Lemons 1978). Spreading by

birds is considered important in introducing initial infection

into uninfected stands.

Because dwarf mistletoes only grow and reproduce on

living trees, any ecological process or management option

that kills the host will eliminate dwarf mistletoes. Wildfire is

believed to have historically kept populations of dwarf

mistletoe in check (Alexander and Hawksworth 1975). The

dwarf mistletoe population is reduced immediately after a

burn, but as a new stand develops, dwarf mistletoe populations increase from seeds cast down from surviving trees.

These overstory trees infect the developing young trees, or

mistletoe is reintroduced into the new stand from adjoining

infested stands.

Management implications-Managing stands to retain

mistletoe-infected trees has both benefits and drawbacks.

Careful selection of infected trees will benefit wildlife;

however, heavy mistletoe infection of a stand may adversely

affect some wildlife. Trees that are heavily infected produce

fewer, smaller cones of poorer quality (Hawksworth and

Shaw 1984). This reduction in cones can affect both tree

regeneration and cone-feeding wildlife. Although small

patches of dead trees provide diversity, extensive tree

mortality may cause loss of canopy cover that protects

wildlife from extreme weather and predation.

Martinka (1972) found heavy use by blue grouse in the

most severely infested Douglas-fir stands. He suggests

curtailing the thinning of overstocked stands and destroying

infected Douglas-fir in areas important for blue grouse

breeding. These thickets are often in areas where the trees

are ill-adapted to the site. To assure that adequate wildlife

habitat is maintained in managed forests, mistletoe-infected

portions of stands identified as being important for blue

grouse breeding and resting should be retained.

Reynolds and others (1992) suggest that although brooms

are beneficial as nesting habitat for goshawks, changes in

stand structure caused by dwarf mistletoes can be detrimental

to some goshawk prey species. For example, ponderosa pine

stands heavily infested with southwestern dwarf mistletoe (A.

vaginatum subsp. cryptopodum) become stagnated and may

not develop beyond the young-forest stage or may revert,

because of high mortality, to the grass-forb-shrub stage.

Management recommendations for developing the desired

forest conditions could include thinnings, with removal of

trees with brooms high in the crown to reduce the detrimental effects of mistletoe in the goshawk postfledgling family

and foraging areas. Selecting reserve trees free of, or only

lightly infected with, dwarf mistletoe may be desirable.

High dwarf mistletoe populations may put the stand at

risk to stand-replacing wildfire. Dwarf mistletoes were

restricted by fire in pre-European forests; frequent fires were

the rule in the drier communities, where dwarf mistletoe is

most prevalent (Hessburg and others 1994). Fire tended to

reduce infection of mistletoe in stands by removing a higher

proportion of trees with heavy infection (Alexander and

Hawksworth 1975). Low-hanging brooms and broken

brooms around the bases of infected trees allowed higher

burning temperatures and greater flame lengths (Wicker and

Leaphart 1974), thereby making the stand more susceptible

to crown fire. Stands recently invaded by Douglas-fir after

fire exclusion may have a steadily increasing risk of crown

fires where infection centers develop.

Although dwarf mistletoes are a native component of the

interior Columbia River basin forests, the effects that these

parasites have on tree growth and survival is an important

forest management issue, not only for timber production, but

also for wildlife and other resources. Because they are

obligate parasites, dwarf mistletoes can be effectively

reduced to meet management objectives by using silvicultural treatments that emphasize the removal of infected trees.

Selecting trees-When selecting infected tree species for

wildlife use, we believe that choosing groups of lightly

infected trees, where the brooms appear large and dense

enough to furnish a nesting platform, will provide the most

benefits to wildlife. Infected trees left in groups rather than

as individual trees throughout the stand can be effectively

isolated from the rest of the stand by maintaining a buffer of

nonhosts or an unstacked area. The buffer or unstacked area

needed to limit spread into the stand is 30 feet for mistletoeinfected Douglas-fir and 100 feet for infected ponderosa pine

(Scott and Schmitt 1996).

Reserving older, infected western larch may be critically

important in some stands to provide nest platforms for

raptors and long-lasting, high-quality cavity-nester habitat.

When selecting overstory western larch as wildlife trees,

select those trees most heavily affected by mistletoe and with

obvious platforms. Most mistletoe-caused larch mortality is

the result of heavy infestations that lead to progressive loss

of broomed branches and degradation of the whole crown.

Such trees are most likely to produce a high-quality snag, but

the infection potential is low because the diminutive crown

supports fewer mistletoe plants. If management of understory western larch is an objective, leaving wildlife trees that

will produce the fewest mistletoe seeds to infect the understory would be best. Lightly infected larch have been

traditionally left as “crop” or “seed-trees,” but they could

produce more dwarf mistletoe seeds because of their larger,

more vigorous crowns.

When selecting infected tree species other than western

larch for wildlife use, leaving a patch of trees that contains

some trees with brooms in the mid-crown that are large and

dense enough to furnish a nesting platform will provide the

most benefit. These trees will have a moderate infection

rating and will be growing slower than uninfected trees, but

they provide good habitat. Trees with brooms in the top

third of the crown can be removed to improve stand productivity with limited loss to wildlife.

16

I
Broom Rusts Elytroderma Disease

:

Ecological processes and functions--Like dwarf mistletoes, broom rusts cause witches’ brooms on their coniferous

hosts. Unlike dwarf mistletoes, which are parasitic plants,

broom rusts are pathogenic fungi. These fungi require an

alternate herbaceous host for completion of their life cycle

but can spread in primary host branches without further

infection (Ziller 1974).

Little information is published on wildlife uses of brooms

Ecological processes and functions--Elytroderma disease

of pines is caused by the needle cast fungus Elytroderma

deformans. It is most prominent in ponderosa pine in the

interior Columbia River basin but is occasionally found on

lodgepole pine (Childs and others 1971). Heavily infected

trees are defoliated because of “cast” or dropping of infected

needles. Brooms formed by this fungus (fig. 30) can

resemble the brooms formed by dwarf mistletoes.

caused by broom rusts. American martens in northeastern

Oregon commonly use rust brooms for rest sites (fig. 27)

(Bull 1995). Thirty-four of 56 flying squirrel dens were in

rust brooms in interior Alaska (Mowrey and Zasada 1984).

Frank Hawksworth speculated that several reports of wildlife

use of mistletoe witches’ brooms documented by wildlife

biologists are actually rust brooms. This speculation is based

on the reports of unlikely hosts for dwarf mistletoes or

geographical locations out of range for a particular hostmistletoe relation (Hawksworth 1992). Nonetheless, rust

brooms probably serve the same functions as dwarf mistletoe

brooms. Broom rusts are not as prevalent in interior Columbia River basin forests as dwarf mistletoes are, and because

of differences in infection biology, care should be taken to

differentiate them from dwarf mistletoes in selecting wildlife

trees.

Little wildlife use of brooms formed by Elytroderma has

been documented, because the brooms are not commonly

distinguished from those formed by dwarf mistletoes. Great

homed owls have been observed nesting in Elytroderma

brooms (Bull 1996b) (fig. 31). Presumably, other raptors

that nest in brooms formed by dwarf mistletoes also would

nest in brooms formed by this fungus.

Infection process-Spruce broom rust (Chrysomyxa

actosathyli) infects Engelmann spruce (figs. 28 and 29). The

herbaceous alternate host is kinnikinnick (Arctostaphylos

uva-ursi). Fir broom rust (Melampsorella

caryophyllacearum) infects grand and subalpine firs. The

herbaceous alternate hosts are chickweeds (Stellaria spp. and

Cerastium spp.). The conspicuous orange-yellow brooms on

their coniferous hosts are apparent, especially in the summer

when affected needles are covered with blisters filled with

yellow or orange spores. The discolored needles are cast in

fall, and a new flush of needles appears the next spring.

Brooms grow perennially and may be older than 30 years.

Broom rusts often are associated with spiketops, dead

branches, stem deformities, and breakage, but host mortality

is rare.

Infection process-Spores of the causal fungus are

released in late spring and early summer from tiny fruiting

bodies borne on infected needles (fig. 32). Under conditions

of rain or free moisture, the airborne spores germinate and

infect the young needles of a susceptible host. The fungus

spreads throughout the needles and into the twigs. The

infection within the twigs spreads into the growing tips and

buds, where it causes brooming and deforms future growth.

Needles infected the previous year are cast after turning

bright red and then fading to straw color. Severe infection

will produce thin, ragged crowns and growth reduction of the

tree. Tree mortality occasionally results from heavy defoliation. Light infection of 25 percent or less of the crown

causes little reduction in tree growth or survival.

Selecting trees-In ponderosa pine, Elytroderma brooms

may be distinguished from mistletoe brooms by the presence

of fruiting bodies on the needles of the broom, by the

accumulation of dead needles in the broom structure, and by

the absence of the dwarf mistletoe plants usually associated

with dwarf mistletoe-caused brooms. Infected needles lose

their bright red-brown color gradually through summer in

Elytroderma brooms. The brooms tend to be more compact

and spherical than those caused by dwarf mistletoes, and the

ends of twigs turn up.

Selecting trees-Because of the difference in the infection process, retention of trees with broom rusts does not

have the potential negative management implications

associated with unlimited retention of dwarf mistletoes.

Trees with the largest brooms are immediately suitable for

wildlife use. Because small brooms often will continue to

grow, trees with all sizes of brooms may be retained for

future use. Retaining infected trees is advisable whenever

possible because broom rusts are uncommon.

Management implications-When selecting broomed

trees in stands for retention where ponderosa pine regeneration is a management objective, selecting Elytrodermainfected trees may be preferable to selecting dwarf mistletoeinfected trees, when they are available. Elytroderma may be

less debilitating to the host tree, and its dense brooms may

sometimes be more valuable to wildlife than are the more

open brooms of dwarf mistletoes. When Elytrodermainfected trees are available, select trees that have 25 percent

or less crown infection.

17
Review

l Brooms serve as food and hiding and nesting habitat for

both invertebrates and vertebrates. Brooming is most often

caused by dwarf mistletoes, rust fungi, or Elytroderma

disease.

l Dwarfmistletoe brooms are most useful to some wildlife if

they form a platform, although the shoots and seeds of the

dwarf mistletoe plant also are eaten by wildlife.

l Dwarf mistletoes can spread to the point that they adversely affect wildlife habitat by limiting tree growth,

causing extensive tree mortality, and increasing risk of

crown fire. To limit spread, dwarf mistletoe-infected

trees reserved for wildlife can be grouped and surrounded

by a buffer of trees that are nonhosts or by a treeless buffer.

Buffers slow the spread into the surrounding stand.

l Brooms caused by rusts offer useful nesting and resting

habitat. These brooms are most commonly found on

Engelmann spruce and subalpine fir.

l Reserving trees with brooms caused by rusts or

Elytroderma disease may provide broom habitat without

the same concerns of spread associated with reserving

dwarf mistletoe-infected trees.

18
Figure 27-American marten using a broom rust in Engelmann spruce as a resting site 

Figure 29-Brooms caused by spruce broom rust are most conspicuous durmg the 

summer when yellow-brown spores are present. 

Figure 28Spruce broom rust on Engelmann spruce. 

19 
Flgure 30-Broom formed by Ely~roderma deformans on ponderosa pine 

Figure 3 lPElytroderma broom used by great horned owls for nesting 

Flgure 32-Discolored needles wth narrow black frwtlng bodler are found in 

Elytroderma brooms. 

20 
DEAD TREES 

Ecological Processes and Functions 

Snags, or standing dead trees, are an essential component in 

forests, and many wildlife species depend on them for survival. 

Patches or even entire stands of trees have died across the 

landscape throughout the evolutionary history of forest 

ecosystems. The events and decay processes that create these 

dead trees maintain the snag resource through time. 

Several factors or combinations of factors can be responsible for tree mortality, including insect outbreaks, diseases, 

tire, drought, and flooding. How the tree dies can determine 

its use by wildlife. Any snag can be used as a perch site, but 

for a snag to be a suitable site for a cavity, the wood typically must be softened by decay (fig. 33). Some sources of 

tree mortality are more conducive to the introduction of 

decay than others. For example, fire can case-harden snags 

and make them resistant to decay. 

Specific types of mortality agents, such as fire, disease, 

or insects, may target different tree species and age classes; 

thus a mix of snag species and sizes occurs across the 

landscape. Although each wildlife species usually has a tree 

species preference for foraging or nesting, it often uses a 

variety of tree species. The wildlife not adapted to using a 

variety of snag species are also those that are most restricted 

in range and in the greatest danger of extirpation. 

Many wildlife species depend on dead trees for nesting, 

roosting, denning, foraging, resting, or shelter. Woodpeckers 

and nuthatches, known as primary cavity nesters, have the 

ability to excavate cavities in snags where they nest and 

roost (figs. 34 and 35). Because woodpeckers usually 

excavate a new nest cavity each year, old nest cavities are 

available for many secondary cavity users. Secondary cavity 

users, which include many species of birds and mammals, 

cannot excavate a cavity but use existing ones for nesting, 

denning, or shelter. Thomas and others (1979) list species 

that use snags and logs in the Blue Mountains in northeastern 

Oregon. 

The space behind loose bark on snags also provides nest 

sites for brown creepers (Certhia americana) and roost sites 

for bats. Brown creepers wedge a nest of grass and twigs in 

the space between the bole and its loose bark. Loose bark 

also provides bats with a dry, sheltered roosting place (fig. 

36). Although bats roost under loose bark, recent studies 

have shown that a high percentage of bat roosts are in 

woodpecker cavities. Steeger and Machmer (1996) found 

that 54 percent of 28 bat roosts were in vacated woodpecker 

cavities, 32 percent in natural cavities, 11 percent in cracks, 

and the remainder under loose bark. 

21 
Ftgure 33-A woodpecker nest cavtty excavated III the decayed sapwood of 

a ponderosa pine snag; the heartwood can be too sound for excavatton. 

Most other tree species have sapwood that is too thin to accommodate a 

nest, so nests are usually excavated in the decayed heartwood. 

Figure 3&Woodpeckers, including this white-headed woodpecker, 

typically excavate nest cavities in dead trees. 

Frgure 35-The red-breasted nuthatch (Sitta canadens~s) requtres 

extensively decayed wood for cavity excavation. 

Figure 36Bats often roost under loose bark and in woodpecker cavities. 

22 
Because owls do not build nests, the smaller owls use

existing cavities (fig. 37), and the larger forest owls use

platforms. Snags with broken tops often provide nest platforms

for great gray (fig. 38) great horned, and barred (Strix varia)

owls.

Snags are used by some woodpeckers for foraging.

Pileated woodpeckers forage extensively in the interior wood

of snags in search of carpenter ants (Camponotus spp.) (fig.

39). Hairy (Picoides villosus), black-backed, three-toed (P.

tridactylus), and white-headed woodpeckers all forage

extensively on dead trees, particularly on insects in the bark,

cambium, and sapwood (fig. 40).

Decay Process

Tree species, size, and percentage of sapwood influence

the rate of decay, as do environmental factors such as

climate, elevation, and aspect. The group of decay fungi that

colonize the sapwood of newly dead trees usually cause

rapid decay. Trees killed by root disease, mistletoe infection,

insect defoliation, drought, or flooding are likely to be

colonized by sapwood rotting fungi and infested by bark

beetles within 2 years after death. Trees killed by bark

beetles often have considerable sapwood decay within a few

years. Once the sapwood decay fungi (fig. 41) have decayed

the newly dead sapwood entirely, they often are replaced by

saprophytic fungi, a large group of general scavengers (figs.

42 and 43). The saprophytic fungi continue to decompose

the sapwood and then proceed at a slower rate into the

heartwood. Heart-rot fungi that may already be present in

the trees at the time of death usually are relatively inactive

and contribute little to the deterioration of the dead tree. The

thin layer of decayed sapwood in Douglas-fir (fig. 44)

contrasts with the thick layer of sapwood in ponderosa pine

(fig. 33). Cavity nesters readily excavate cavities in the thick

sapwood of ponderosa pine snags because it is softened by

decay.

Stain-causing fungi (that is, “blue stains”) often are

associated with beetle and woodborer infestation. The stain

fungi do not cause decay, or softening, of the wood. They

invade and use the cell contents, in contrast to the decay

fungi, which use the structural components of the cell wall.

Trees killed by root disease typically add to the snag

component for only a short time before they fall over. Root

disease is caused by a group of decay fungi that infect roots

and spread through root contact. Root disease pockets start

in a tree or stump and tend to spread outward in all directions

(Bega 1978). Typically, the tree dead for the longest time

will be in the center and fringed by dying or recently dead

trees on the outeredge (fig. 45). Although snags created by

root disease may not stand for a long time, the expansion of

the center provides a continuous supply.

The rate of decay in trees killed by fire is influenced by the

intensity of the fire, the rate of tree growth before the fire, the

tree species, and its size. The sapwood and heartwood of true

firs killed by fire deteriorates faster than in other species. The

thin layer of sapwood in fire-killed Douglas-fir deteriorates

rapidly, but the heartwood decays more slowly than in other

species. The extremely thick sapwood of ponderosa pine,

which ordinarily constitutes from 50 to 75 percent of the tree’s

volume, is more resistant to general deterioration than is the

sapwood of other species. The sapwood of fire-killed ponderosa pine begins to soften in the third year after death (Kimmey

1955).

Selecting Snags

Characteristics to consider when selecting snags for retention are tree species, diameter, height, structural class, and

proximity to other snags and live trees. The kind of snags

retained depends on management objectives and the snag

resource available. For example, if the objective is to leave rest

sites for martens, then hollow grand fir and western larch snags

would be retained. If the objective is to provide nesting habitat

for large forest owls, large-diameter snags with broken tops

would be retained. To provide habitat for all cavity nesters, a

variety of tree species would be retained for both foraging and

nesting.

Tree species-Retention of snag species depends on the

objective and the geographic area. In Montana, McClelland

and others (1979) found that western larch, ponderosa pine,

paper birch, and quaking aspen are preferred for nesting by

cavity-using birds. Douglas-fir was used for foraging rather

than nesting. Another study in Montana showed that rednaped sapsuckers used paper birch (5 1.6 percent of nest

trees), western larch (35.5 percent), quaking aspen (6.5

percent), and Douglas-fir (6.5 percent) for nest sites

(Tobalske 1992). In interior cedar-hemlock (Tsuga

heterophylla) stands in southern British Columbia, 85

percent of 237 nests of cavity-using birds, 14 cavity-using

mammals, and 31 bat nurseries were in Douglas-fir, quaking

aspen, paper birch, and western larch (Steeger and Machmer

1995). All nests excavated by black-backed (n = 35 nests)

and three-toed (n = 20) woodpeckers in a study in central

Oregon were in lodgepole pine (Goggans and others 1988).

In central Oregon, Bate (1995) reported that woodpeckers

prefer ponderosa pine snags over lodgepole pine snags for

nesting. Dixon (1995) also reported a nesting preference for

ponderosa pine snags by white-headed woodpeckers. In

northeastern Oregon, ponderosa pine and western larch were

favored as nest trees by pileated woodpeckers and Williamson’s

sapsuckers; most nest trees used by hairy and black-backed

woodpeckers and northern flickers were in ponderosa pine trees

(Bull 1986). In east-central Washington, woodpeckers selected

ponderosa pine and Douglas-fir for nest cavities and western

larch and Douglas-fir for feeding (Bevis 1996).

When retaining snags for cavity nesters, ponderosa pine,

western larch, quaking aspen, and paper birch are the

favored species in many localities. Suitability of other

species must be determined based on known wildlife use and

decay conditions characteristic of each tree species for each

locality. For hollow snags, grand fir is the best species to

retain in the interior Columbia River basin.

Tree size and height-Typically, large-diameter snags

(more than 20 inches d.b.h.) stand the longest, can accommodate nest cavities of any woodpecker species, and provide

23
Figure 37Small owls, like this saw-whet owl, require an 

existing cavity for nesting. 

Figure 38--Great gray owls, as well as some other large owls, 

may use the broken tops of snags for nesting. 

Figure 4&Hairy, black-backed, and three-toed woodpeckers 

forage for invertebrates in the bark of snags. 

Figure 39-Pileated woodpeckers, m search of carpenter ants and 

other invertebrates, excavate large rectangular cavities in the 

heartwood of some snags and logs. 

24 
Figure 41-The pouch fungus (Crypfoporus volvatus), a 

sapwood decay fungus, typtcally invades and fruits on trees soon 

after their death (up to, but not longer than 18 months). 

Figure 42-The red belt fungus (Fom~rops~spin~cola), a saprophyte, IS one 

of the most common fruitmg bodies found on snags and logs. 

Ftgure 43-Fruitmg bodtes of many other saprophytic fungi commonly are 

seen on logs, because the moisture conditions are conducive to decay and 

formation of fruiting bodies. 

Figure 4GA Douglas-fir killed by Insects, the sapwood is extensively 

decayed, and the heartwood is sound. 

25 
Figure 45-Root diseases start in a tree or stump and spread slowly outward in all directions. Disease 

Dockets tmically have the oldest snags in the center with a fringe of dying trees. Trees in root disease 

pockets &y no; stand long because of root decay. 

the most stable microclimate because of the wood thickness. 

Preference for large-diameter snags has been well documented for the pileated woodpecker, hairy woodpecker, 

northern flicker, and Williamson’s sapsucker in northeastern 

Oregon (Bull 1986); for the white-headed woodpecker in 

central Oregon (Dixon 1995); for woodpeckers in ponderosa 

pine forests in central Oregon (Bate 1995); for pileated 

woodpeckers in Montana (McClelland and others 1979); and 

for cavity nesters as a group in burned ponderosa pine forests 

of southwestern Idaho (Saab and Dudley 1997). 

Thickness of the wood surrounding a cavity is important 

for thermal regulation and protection from predators. 

Woodpeckers that nest or roost in small trees may have only 

a thin shell of sapwood or only bark surrounding their cavity, 

which provides minimal insulation and protection against 

predators. Black bears, martens, or raccoons (Procyon Z&or) 

can break into a nest cavity if the shell surrounding it is too 

thin. 

Although most cavity nesters select for the largest snags 

available, a few species seem to prefer smaller trees in some 

localities. Downy (P&ides pubescent) and three-toed woodpeckers prefer smaller trees for nesting in Montana (McClelland 

and others 1979). Black-backed woodpeckers use relatively 

small, hard snags in areas with stand-replacing fires in ponderosa pine/Douglas-fir stands in Idaho (Saab and Dudley 1997). 

Height is also important in selecting snags because 

different species of woodpeckers prefer to nest at specific 

heights (Thomas and others 1979). Pileated woodpeckers 

typically nest 30 to 50 feet above the ground. To have 

enough girth at these heights to accommodate cavities that 

are 8 to 10 inches wide and 24 inches deep takes a large tree. 

Although some woodpeckers will nest within 3 feet of the 

ground, these nests are more vulnerable to predators (Li and 

Martin 199 1) because they are easily detected. 

26 

In addition, the larger and taller snags have greater 

volume and are more likely to have the appropriate decay 

conditions at the preferred height than are smaller trees. 

Therefore, when possible, managers should retain the largest 

snags available. 

Snag structural classes-The physical appearance of snags 

is largely indicative of the condition of the wood, so appearance 

is the basis for snag selection. Thomas and others (1979) 

presented nine successional stages from the time of death to 

total decomposition of a tree. Here we present a simplification 

of the successional stages and classify all snags into three 

structural classes (figs. 46 and 47). When retaining snags, all 

structural classes should be represented across the landscape. 

Snag structural class 1 represents those snags that have 

recently died, typically have little decay, and retain their 

bark, branches, and top. These snags are used extensively by 

woodpeckers for foraging in and under the bark. 

Snag structural class 2 represents those snags that show 

some evidence of decay and have lost some bark and 

branches, and often a portion of the top. Most nesting by 

woodpeckers, as well as extensive foraging in and under the 

bark and in the interior of the wood, is in this structural class. 

Remaining bark that has loosened can provide nest sites for 

brown creepers or roost sites for bats. 

Snag structural class 3 represents those snags that have 

extensive decay, are missing the bark and most of the branches, 

and have a broken top. Structural classes for grand fn and 

Douglas-fn must be modified to some degree because they tend 

to retain their bark. Foraging in the interior wood is the primary 

activity in these extensively decayed snags. Secondary cavity 

users also may nest in existing cavities originally excavated by 

woodpeckers. Weaker excavators like northern flickers and 

Lewis’ woodpeckers (Melanerpes lewis) excavate nests in 

extensively decayed wood characteristic of this structural class. 
Figure 47-Three structural classes of dead trees. 

27 
Snag distribution -- Snags can either be left in clusters or

scattered across the landscape, although where to retain them

depends largely on where they currently are. Typically,

snags are in clumps naturally because the agents of disease,

insects, fire, or flooding that kill many trees act in a localized

area. Clusters of snags may be easier to protect during

management activities than snags evenly distributed across

the landscape. Worker safety is an issue when harvesting

adjacent to snags. Retaining snags in clusters, as well as the

live trees between the snags, keeps workers away from snags

and provides canopy cover for wildlife using the snags.

Two studies on woodpecker use of snag clusters reported

different results. No difference was found between woodpecker

use of snag clusters versus scattered snags in western Oregon

(Chambers 1997). In areas where stand-replacement fires had

burned in ponderosa pine/Douglas-fir stands in Idaho, Saab and

Dudley ( 1997) found that cavity nesters as a group select

clusters of snags for nest sites instead of evenly spaced trees.

Most studies recommend managing snags in every 5- to

25-acre patch (Bate 1995, Evans and Martens 1995).

Because woodpeckers are territorial, only one pair of each

species occupies the same territory; therefore, to attain the

maximum density of cavity nesters, snags need to be distributed across the landscape.

In addition, retaining snags on all aspects and on all positions of the slope ensures habitat availability for wildlife species

with different preferences. For example, pileated woodpeckers

tend to roost in draws during summer but roost higher on slopes

in winter (Bull and others 1992). Martens rest or travel in

riparian areas a third of the time in summer but only half that

often in winter; upper slopes ate used half the time in winter but

only a third of the time in summer (Bull 1995).

Retaining snags close to living trees provides cover for

cavity users. If snags are retained in the middle of a clearcut,

species like northern flickers, Lewis’ woodpeckers, bluebirds,

and American kestrels (Falco sparverius) will use them for

nesting, but most other woodpeckers will not nest in open areas.

In many areas, fuel-wood cutters are likely to remove

snags along roads. This potential problem can be remedied

by not leaving snags in areas that are accessible to fuel-wood

cutters or by not counting snags left adjacent to accessible

roads toward the number retained for a particular stand.

In summary, wherever the objective is to provide viable

populations of primary and secondary cavity nesters, prudent

managers will provide large-diameter snags when available,

snags in a variety of structural classes, snags in every 5- to 25-

acre stand and in clusters if available, and snags on all slope

aspects and positions of the slope, and adjacent to green trees.

Snag densities-Limited information is available on

numbers of snags to retain for wildlife species in the interior

Columbia River basin (Bate 1995, Bull and Holthausen

1993, Dixon 1995, Evans and Martens 1995) (table 1). The

guide most widely used in the past, Thomas and others

(1979), prescribed the number of nest and roost trees to leave

for specified woodpecker populations, but the number was

based on a hypothetical, untested model and did not include

any snags for foraging. Three studies (Bate 1995, Bull and

Holthausen 1993, Dixon 1995) conducted in eastern Oregon

have shown that retaining foraging structure is essential, in

addition to nest and roost trees in managed landscapes. The

Thomas model provided only two roost trees per pair per

year, yet research has shown that individual pairs of pileated

woodpeckers and white-headed woodpeckers use considerably more than two per year (Bull and others 1992, Dixon

1995). Radio-telemetry studies have shown that home range

sizes of pileated woodpeckers (Bull and Holthausen 1993),

white-headed woodpeckers (Dixon 1995), and three-toed and

black-backed woodpeckers (Goggans and others 1988) are

considerably larger than those used in the Thomas model.

Raphael and White (1984) found that the relation between

numbers of snags and cavity nesters is not linear, which was

assumed in the Thomas model. The substitution factor used

in the Thomas model is variable and largely a function of

snag density. Neitro and others (1985) thought allowing

substitution of snags that reduced the number retained was

not appropriate. The Thomas model did not take into

account the habitat needs of some of the secondary cavity

nesters, like bats and brown creepers, that use such snag

features as loose bark. In addition, Bull and Holthausen

(1993) found lower densities of pileated woodpeckers in nine

study areas than predicted by Thomas and others (1979)

based on the number of snags present. The above studies

present new data suggesting that some of the assumptions

and data used in the Thomas model are not valid, and that the

prescribed snag densities need to be revised upward.

We know of only three studies in the interior Columbia

River basin that have calculated both the density of snags and

woodpeckers in managed and unmanaged landscapes. Bate

(1995) used six study areas in ponderosa pine stands and found

woodpecker abundance was best predicted by hard snag density,

large green tree density, canopy height, and number of canopy

layers. Of the nine study areas, only one represented a relatively unmanaged forest with the number of snags that probably

approximated historical ones. In this stand, Bate found 3.8

snags greater than 10 inches d.b.h., and 60 percent were larger

than 20 inches d.b.h. These snag numbers supported 32.3

woodpeckers per 247 acres and represented the study area that

most likely supported viable populations of cavity nesters.

Dixon (1995) found similar results in some of the same study

areas Bate used.

Another study relating woodpecker density to snag density

was conducted in northeastern Oregon (Bull and Holthausen

1993). The two study areas that contained viable populations of

pileated woodpeckers had an average of 4.2 and 3.8 snags (10

inches or larger d.b.h.) per acre and 0.5 and 0.4 nesting pairs per

247 acres, respectively. The two study areas were in lightly

managed landscapes predominated by mixed-coniferous stands

with a high density of logs.

Evans and Martens (1995) recommended densities of

snags for retention on the Payette National Forest based on

their ecological value, encompassing soil health, seedling

regeneration, moisture retention, nutrient recycling, and

wildlife use (table 1). The numbers that they recommended

were derived from actual snag numbers identified during

28
timber inventory and vegetation plots but were scaled down

to the lower ranges of the snag numbers for the recommendations and include snags 10 inches d.b.h. and larger.

Ideally, data would be available on the exact number of

snags required to support specific populations of primary and

secondary cavity nesters. Unfortunately, this kind of

information is not available. We do know, however, that the

snag numbers presented by Thomas and others ( 1979) are

not adequate to support the populations intended because of

a lack of foraging strata and invalid assumptions used in the

model. If management agencies have an objective to manage

for viable populations of woodpeckers, providing numbers of

snags that have been shown to support viable populations in

the recent studies would be prudent.

Although snags are the key structure typically focused on for

cavity nesters, realizing the importance of the forest surrounding

the snags also is essential. Some species like the pileated and

white-headed woodpeckers and American martens are associated with older forests. For white-headed woodpeckers, the

snags must be in association with large-diameter ponderosa

pines. For pileated woodpeckers and martens, logs, largediameter green trees, and a dense canopy are needed. Leaving

large-diameter snags or green trees in younger forests, also has

value as providing biological legacies.

Snag retention in burns-The above management implications apply to healthy green stands. With vast areas of Oregon,

Washington, and Idaho burned by wildfires in the 199Os, there

is much interest in determining numbers of snags to retain in

burned areas after harvesting. Saab and Dudley (1997) reported

that woodpeckers selected nest sites with snag densities greater

than those measured at random sites in ponderosa pine/Douglasfir forests with stand-replacing fires. From 10 to 14 snags per

acre were retained in burned stands that were harvested; about

38 to 42 snags per acre were in the unharvested burned stands.

Seven species of cavity nesters using the burned stands selected

nest sites with more than 20 snags per acre, where snags were

distributed in clumps. Lewis’ and white-headed woodpeckers,

and American kestrels selected the largest, most heavily

decayed snags available for nesting. Evans and Martens (1995)

presented recommendations for numbers of snags to leave in

burned stands.

Green tree replacements-Snags are a dynamic resource;

old snags fall and living trees die to become new snags.

Snag-dependent wildlife need a continuous supply of snags

over time. To provide a continuum of snag habitat, future

snags must be planned for by leaving green trees to eventually become snags in managed stands. To determine the

number of green tree replacements, information on fall rate

of standing snags, snag density, live stem density, and

mortality rate of live stems is required. Various models have

been developed to calculate the number of green trees to

provide for recruitment when specific stand inventory

information is available (Bull and others 1980, Cimon 1983,

Schommer and others 1993). If snags are to be created by

killing green trees when the stand becomes snag deficient,

the number of green trees required is less because the

manager does not have to rely on natural mortality to replace

those snags that fall. Creating snags is costly, however, and

stands are seldom monitored to determine when trees need to

be killed.

Snag Longevity

Snag longevity, or the amount of time a snag stands, is

essential information for managing the snag resource. The

length of time snags stand is a primary factor in determining the

number of green tree replacements needed to maintain a specific

snag density over time. Snag longevity is a function of many

factors including species, diameter and height, percentage of

heartwood, cause of death, soil type and moisture, forest type,

and prevalence of windstorms. Because so many factors

influence how long a snag stands, fall rates should be determined by species and size class on each management area.

Listed below are studies that report snag fall rates. When

possible, the amount of time when 50 percent of snags in a

particular study have fallen will be reported.

Several studies have reported fall rates of beetle-killed

ponderosa pine. Keen (1955) reported that 50 percent of the

ponderosa pines in southern Oregon and northeastern

California fell 9 to 10 years after death on pumice soils and 6

to 7 years after death on loam soils. The percentages of

snags that fell after 7 years by diameter class, are presented

in the following tabulation:

Diameter class (inches) Percentage

l0-18 75

20-28 65

30-38 50

40-48 35

> 50 30

Most of the beetle-killed ponderosa pines in Colorado fall

between 7 and 10 years after infestation (Schmid and others

1985). Trees were 7 to 22 inches d.b.h.

In northeastern Oregon, half the ponderosa pines less

than 10 inches d.b.h. fell 7 to 8 years after death and half

those 10 to 19 inches d.b.h. fell after 8 to 9 years (Bull

1983). Beetle-killed lodgepole pines have similar fall rates,

with half of those less than 10 inches d.b.h. falling within 6

to 7 years and half of those 10 inches and larger falling after

7 to 8 years (Bull 1983). In a second study in northeastern

Oregon (Bull and Partridge 1986), half of the ponderosa pine

snags less than 20 inches d.b.h. fell after 6 years; half of the

ponderosa pine snags 20 inches and larger fell after 9 years.

Beetle-killed spruce in Colorado stood much longer than

ponderosa pines reported in the studies above. Mielke (1950)

found that 84 percent of beetle-killed spruce remain standing

after 25 years. Hinds and others (1965) found that 72 percent of

beetle-killed spruce remain standing after 20 years.

Fire-killed snags may or may not stand longer than

beetle-killed snags, depending on the area. Dahms (1949)

reported that a little over half the ponderosa pine snags are

down 10 years after a fire in central Oregon. In Montana,

nearly half of all lodgepole pine snags fall by the fifth season

(Lyon 1977). In California, Kimmey (1955) described the

29
breakup of a fire-killed stand, although specific fall rates

were not presented. In the fourth and fifth year after the fire,

many ponderosa and Jeffrey pine (Pinus jeffreyi) broke off at

the ground or up to 50 feet above the ground. By the fifth

year, the general breakup continued until only scattered

barkless snags and stubs remain.

In northeastern Oregon, different methods of killing

ponderosa pines were investigated (Bull 1996c, Bull and

Partridge 1986). Trees that had been topped stand the

longest; half of those less than 20 inches d.b.h. are down

after 10 to 12 years; half of those 20 inches or larger are

down after 12 to 17 years. Half the trees injected with a

silvicide are down 7 years after treatment. Half the girdled

trees are down 9 years after treatment.

Fall rates of snags that have been created differ. Ponderosa pines infected with dwarf mistletoe were frilled and

poisoned with an herbicide in the Southwest; after 10 years,

95 percent of those trees are down (Fairweather 1995).

All of these studies suggest that most ponderosa pine and

lodgepole pine that died from fire or beetles in the interior

Columbia River basin have fall rates of less than 10 years.

Small-diameter snags fall sooner than do larger ones.

Sampling Techniques

Knowledge of snag density is essential for managing

forest stands effectively, as well as for complying with

standards and guidelines. Various methods have been used

to determine snag densities: area-wide counts, fixed-radius

circular plots, variable-radius plots using prisms (Bull and

others 1990), and variable-strip transects (Bate and others, in

press). Total counts of snags over large areas are very timeconsuming but yield the most accurate density information.

Fixed-radius plots typically need to be at least 1 acre because

snags are usually scarce and variance is high. Many plots

are usually required to accurately estimate snag density.

Bate and others (in preparation) have developed a more

efficient method of sampling snags than either area-wide

counts or fixed-radius plots: data are collected from a pilot

sample transect and used in a computer program. The

program determines the optimal length and width of a strip

transect within a given area; the optimal size is that which

minimizes the cost and variance. The program then provides

the necessary sample size to obtain a snag density within the

desired statistical bounds. Transect lengths are either 164 or

328 feet; transect widths range from 33 to 131 feet. The

Table l-Density of snags reported or recommended in four areas;

numbers are snags per acre larger than 10 inches d.b.h. (unless

otherwise stated), and the percentages represent snags larger than 20

inches d.b.h.

Locality

Forest type

Western Central

Idahoa Oregonb

Northeast

Oregonc

North-central

Idahod

Ponderosa pine:

Open canopye

Closed canopyf

Mixed conifer:

Open canopy

Closed canopy

Lodgepole pine:

Open canopy

Closed canopy

Spruce/fir

1.6(75%)

4.8(44%) 4(60%)

2.5(72%)

9.0(39%)

4.5

7.7

9.5(21%)

3.8(29%) 10-48

a

 Recommendations for snag densities selected from the lower ranges of snag

numbers on timber inventory plots and fixed-radius plots on the Payette National

Forest; different snag levels recommended for burned and unburned stands (Evans

and Martens 1995).

b

 Snag numbers based on variable-width transects conducted in an unmanaged stand

of old growth in central Oregon where woodcutting was prohibited (Bate 1995).

c

 Numbers based on density of snags in two 4,000-acre study areas in northeastern

Oregon that supported viable numbers of pileated woodpeckers; areas had some

timber harvest but no woodcutting (Bull and Holthausen 1993).

d

 Densities based on timber inventory plots in unmanaged stands of large saw timber.

The snag density varied depending on what snags were included in the count. The 10

snags per acre included only snags 15 inches d.b.h. or larger and 50 feet or taller.

The 48 snags per acre included all snags 15 inches d.b.h. or larger of any height.

Western white pine snags were not counted (Craig 1995).

e

 Stands with less than 30 percent canopy closure.

f

 Stands with more than 30 percent canopy closure.

30
program also provides a “distribution index,” which is an

estimate of the percentage of the sampled landscape supporting target snags or trees.

Creating Wildlife Trees

In managed stands, retaining existing snags is the most

ecologically sound and economical approach to providing

wildlife trees. If stands are devoid of snags, however, an

option is to alter or kill living trees. Depending on the method

used, killing trees can be costly and may not produce the

desired decay conditions. Years may pass before the decay is

sufficiently advanced to promote cavity-nester excavations.

Bull and Partridge (1986) investigated six methods of

killing ponderosa pine. They determined that topping trees

with either a chainsaw or explosives produced snags that

stood the longest and received the greatest nest use by

woodpeckers (figs. 48 and 49). In this study, girdling, fungal

inoculation, and beetles attracted by pheromones did not

consistently kill the tree. Trees killed by girdling or silvicides

fell over too quickly to provide wildlife nest trees.

In a study in New Mexico, all of the ponderosa pines

killed by girdling were used for foraging by woodpeckers.

Most of the trees greater than 16 inches d.b.h. were standing

after 7 years, and about 30 percent contained woodpecker nest

sites (Parks 1996b). Because the climate in the New Mexico

sites is drier than in the Oregon study area used by Bull and

Partridge (1986), basal decay of killed trees may have been

less, so the trees stood longer.

Recent work by Parks and others (1996a, 1996b) documents a new method of inoculating live trees with decay

fungi. Six years after inoculation of 60 living western larch,

14 percent contained woodpecker cavities near the point of

inoculation. These trees may remain alive for decades with a

pocket of decay that woodpeckers can use for nesting. Trees

may be logged next to these trees without safety concerns, and

live trees are less likely than dead trees to be lost to fuel-wood

cutters. These preliminary results for western larch suggest

that inoculation produces desirable wildlife trees at a lesser

cost than killing trees to create snags.

A variety of wildlife tree structures can be created with a

chainsaw in standing, living trees. Trees can be topped

leaving a horizontal branch structure on which ospreys

(Pandion haliaetus) can build nests (fig. 50). A depression

can be cut into the top of a tree that has been topped to

produce a nest site for great gray owls (fig. 51). Artificial

cavities and hollows can be cut into standing and downed

trees (figs. 52, 53, and 54). Slits can be cut into trees to create

roosting habitat for bats (fig. 55). These techniques and

others are described by Brown (1996).

Three primary considerations in creating wildlife trees are

the target wildlife species for which the structure is being

created; the tree species, size of tree, and habitat locality most

likely to be used by the targeted wildlife species; and the

method of altering or killing trees that is most likely to

produce long-standing trees in a given geographic area.

Rainfall, snowfall, incidence of windstorms, and prevalent

decay organisms all must be considered.

Thousands of trees have been killed to create snags in the

interior Columbia River basin in the last 15 years. Few of

them have been monitored, however, to determine whether

long-lasting, quality snags were actually produced. Because

climate and decay organisms differ with area, results of

management activities, such as snag creation, must be

monitored to ensure that results warrant the cost of these

treatments. We include a data form to monitor wildlife use of

created snags in appendix A.

Review

l Ponderosa pine, western larch, quaking aspen, and paper

birch are favored tree species for nest sites of woodpeckers

in many areas in the interior Columbia River basin.

l Large-diameter snags provide nest habitat for the greatest

variety of cavity nesters and stand longer than smaller

snags.

l Snags can be classed into three structural classes that are a

simplified version of past decay class categories.

l Snags should be provided in every 5- to 25-acre stand, in

clusters if available, on all slope aspects and positions of

the slope, and adjacent to green trees.

l Recent studies have shown that the snag model developed

by Thomas and others (1979) did not accurately predict

woodpecker abundance based on snag abundance. New

information suggests that foraging strata (snags and other

structures) must be incorporated into any snag model, and

that snag numbers need to be revised upward.

l Published data suggest that populations of cavity nesters ,

were viable in stands of ponderosa pine and mixed-conifer

forests that contained about four snags per acre, a large

component of old-growth stands, and abundant logs.

l Snags can be retained over time by using models for green

tree replacements.

l Snag longevity depends on cause of death, tree species,

diameter, height, amount of heartwood, geographic area,

and site conditions.

l Creating snags and other wildlife structures can mitigate

the loss of natural habitat, but retaining existing structures

is most cost effective and ecologically sound.

31
Figure 4CPonderosa pine snags created by topping received the greatest 

amount of woodpecker nest use in eastern Oregon. 

Figure 50-Topped trees with a platform provide nest sites for ospreys. 

Figure 49-A ponderosa pine bein g topped to create a sna& 

Figure 5 I-This nest site for great gray owls was created by topping a tree 

and cutting a depression in the top of it. 

32 
Figure 52-Thts artlficlal cavity was made by removing a block of wood 

and fashioning a face piece with an entrance hole. 

Figure Sehainsaws can be used to create hollow chambers in logs. 

Figure 534utting a hole mto a hollow western redcedar log 

allows access by wtldlife. 

Figure 55-Slits cut mto trees provldc roost sltev for hats 

33 

LOGS 

Ecological Processes and Functions and animals, down wood in all its forms represents a rich 

The natural fate of all living trees is to become part of the substrate on which they feed and live. 

down-wood component on the forest floor. Characteristics of We use the term “logs” for down woody material such as 

the living and dead standing component in a stand determine trees, branches, or tops that have fallen to the forest floor. 

the species and physical attributes of the material that falls to The minimum piece-size to qualify as a log has a large-end 

the ground. Late-successional stands typically have large- diameter of 6 or more inches and a length of 8 or more feet. 

diameter logs on the forest floor recruited from the wood A leaning snag that forms less than a 45” angle with the 

resources in the standing trees through a variety of natural ground is considered a log. Most logs touch the forest floor, 

processes such as breakage; falling trees; and transport caused but sometimes they fall like jackstraws and are supported 

by snow-loading, windstorms, avalanches, debris flows, fires, above ground by other logs (fig. 56). 

and floods. Other natural processes such as the activity of Logs can be considered as either places animals forage or 

insects and diseases that kill or physically weaken trees places that afford them protection. Insect-eating, hmguslikewise contribute dead wood to the forest floor. All these eating, wood-eating, and predaceous animals find rich and 

factors can directly or indirectly result in death and falling of varied sources of food in and associated with logs. Besides 

individual branches, tops, or whole trees. Stands or patches hiding cover and protection, logs provide physically complex 

of trees and landscape-scale tree mortality are common events structures where animals find stable temperatures and 

in the history of forest ecosystems. All of these mortality and moisture for nesting, denning, feeding, and food storage. 

decay processes are natural and necessary; they contribute to Logs also serve as places for sunning and as lookout posts. 

the nutrient reserves and physical and chemical characteristics Spruce grouse (Dendragapus canadensis) regularly sit on 

of soils in healthy forests. Thus, dead wood in all its forms is logs sites where they are apparently better able to avoid 

a fundamental feature of healthy forests. predation. In spring, males use these elevated sites as 

The “life” or persistence through time of dead trees, walkways for their displays (Harrison 1996). 

especially large ones, can last several decades. Over a period Small mammals use logs extensively as runways. This 

of possibly a century, logs serve as a source of organic and association between log structure and small mammals was 

inorganic nutrients and chemical components in soil develop- apparent in studies of radio-tagged great gray owls. Nearly 

ment. The constituents contributed by logs enrich the soil and 80 percent of the time, down wood was within 3 feet of 

improve its structural properties, allowing plant growth. Logs where great gray owls captured or attempted to capture prey 

contribute to the water economy of a site and provide micro- (fig. 57) (Bull and Henjum 1990). Maser and others (1979) 

habitats that protect wood-dwelling organisms with moist, described wildlife uses of logs in relation to log decomposithermally stable, predator-protected niches in which to live. tion class, size, age, log species, and distribution. They 

Logs in or near streams, ponds, or lakes provide structure for described processes that lead to increased and more varied 

amphibians, beaver, mink, otter, and birds (Lofroth, in press; uses of logs by wildlife, plants, and invertebrates as logs 

Maser and Trappe 1984). decompose. Lofroth (in press) reviewed literature that 

Organisms representing a broad array of plants, inverte- further describes wildlife uses of logs, including log habitats 

brates, and vertebrates use log habitats in forests. From under snow. 

microscopic protozoa and fungi to wildlife and roots of large The size, distribution, and orientation of logs are more 

trees, down wood teems with life. Many of these organisms important to wildlife than are the tonnage or volume, as used 

are connected by functional pathways that are partially or in characterizing woody fuels (Maxwell and Ward 1980). In 

completely unknown. For both simple and complex plants general, specific wildlife uses are correlated with log size. 

35 
The smaller logs benefit small mammals, amphibians, and

reptiles, for which they function primarily as escape cover and

shelter when the animal can get inside or under the log (fig.

58). Large-diameter logs, especially hollow ones, also benefit

a variety of other vertebrates like martens, minks, coyotes,

bobcats, cougars, and black bears (Lofroth 1993; Lofroth, in

press; Maser and Trappe 1984) (fig. 59). Hollow logs are

used by black bears for winter dens in some parts of their

range. During late summer and fall, bears forage for invertebrates in logs (fig. 60). What percentage of their diet depends

on this resource is not known, although it seems to be substantial based on current studies in northeastern Oregon

(Henjum and Akenson 1996). Research on fishers (Martes

pennanti) suggests that up to three dens may be used in

rearing a litter. Although most dens are in cavities high in

large (36-inch d.b.h.) living or dead trees, large logs also are

used. In California and Montana study sites, one den was in a

36-foot log that was large enough to provide a convoluted 12-

inch diameter cavity through its length; another den was in a

59-inch log of white fir (Abies concolor) (Powell and

Zielinski 1994).

Lynx (Lynx canadensis) select dense, mature forested

habitats that contain large logs and upturned stumps to

provide security and thermal cover for kittens. In northcentral Washington, lynx den in Engehnann spruce/subalpine

fir/lodgepole pine stands with high densities of downed trees

supported 12 to 48 inches above the ground, which provide

structure and diversity for denning and hunting (Koehler and

Aubry 1994).

Distribution of logs influences wildlife use. Trees sometimes die in clumps or patches from diseases, insect activity,

or fire. Mortality of this kind ultimately results in aggregations of logs. Within relatively continuous forested stands,

however, logs appear fairly regularly. In late- and oldstructure mixed-conifer stands in northeastern Oregon, we

found that densities of logs fell within relatively close ranges;

that is, standard errors were 8 to 18 percent of the means.

These stands were not randomly selected stands, however, but

were associated with pileated woodpecker home ranges (Bull

and Holthausen 1993, Torgersen and Bull 1995).

Amounts and distribution of logs in managed landscapes

have varied effects on wildlife and management strategies.

Too many logs may impede travel by deer, elk, and cattle;

they also may present increased fire hazard (fig. 56). Large

numbers of logs afford excellent cover habitat for small

vertebrates (fig. 56). Heavy accumulations of down woody

debris can increase seed losses and damage to tree seedlings

by squirrels, chipmunks, and mice, but these accumulations

do not necessarily result in such damage. Research suggests

that seedlings may actually be protected from grazing and

scorching by the physical barrier and shading provided by

down logs. Such protection often outweighs the negative

effects of increased habitat for rodents and problems associated with them (Dimock 1974, Maser and others 1979).

Orientation of logs can influence wildlife use. Logs that lie

along the contours of a slope may be used more by wildlife

than logs oriented across contours, especially on steep slopes.

Soil and organic debris that accumulate along the upslope side

of a log encourage seedlings to establish and grow, which in

turn attract invertebrates and small vertebrates that find more

diverse structure and niches for activity (Maser and Trappe

1984).

Large numbers of down trees can form a maze of logs,

many of which may be supported 2 or more feet above the

ground by other logs. Patches of these jackstrawed logs often

are found in late- or old-structured stands of lodgepole pine,

Engelmann spruce, subalpine fir, and grand fir. Although

such conditions may represent a significant fire hazard, they

also provide critical structures for some animals. Marten,

mink, and cougar hunt in them; when snow covers the logs, a

complex array of snow-free spaces and runways provide

important habitat for protection and foraging by martens,

fishers, and small mammals under the snow. Tree squirrels

also spend much of the winter in this environment, where they

feed on seeds from cached cones.

Slash piles remaining after harvest can benefit some

wildlife like rodents, hares, and rabbits (fig. 61). Increased

commercial markets for chips and firewood have increased

demand on this component of wildlife habitat. No completely

researched guidelines exist for distributing logs and woody

debris in managed stands. Although quantitative, spatial, and

functional relations are still poorly understood, that does not

make any single component or feature of distribution any less

important (Bartels and others 1985, Maser and others 1979).

Decay Process

The decay of logs is continuous; some decay may begin

even before a tree dies. The rate and patterns of decay and the

decay organisms depend on many dynamic factors. Did the

down log derive from a fallen snag or a living tree? If the log

came from a snag, what killed the tree? How big is the log?

Is it a long, small-diameter log or a short, large-diameter log?

Every living tree is composed of tissues that perform

specific functions and have different structures to accomplish

these functions. These tissue-substrates continue to provide

different environments in logs over many years for a host of

microbes, higher plants, and invertebrates. The succession of

decay-related organisms in turn produces a continuum of

decayed wood with many different structural and textural

characteristics.

Hollow logs are an example of a particularly important

structural category. Logs do not become hollow on the

ground; they are hollow because of the action of heart-rot

fungi that occurred when the tree was alive. Such hollow

trees ultimately die and fall to the forest floor (fig. 59).

The physical setting in which the log resides also affects

the decay process. Slope, aspect, exposure to sunlight,

elevation, and the degree to which the log is in contact with

the ground all influence the characteristics of decay. Even

orientation of the log can influence decay: logs that are

oriented along the contours of a slope accumulate soil and

debris against the uphill side, which holds moisture and

hastens some decay processes. Charring of logs can hamper

excavation by some invertebrates and vertebrates for many

36
Ftgure 5bAccumulattons of logs provrde cover for small mammals but Figure 57-Prey captured by great gray owls is often associated with down 

may Impede movement by deer and elk. woody material. 

Ftgure 5X-Rubber boas (Channa borne), other reptrles, and amphtbrans 

may burrow into decayed logs. 

Figure 59-Hollow logs are used by martens, black bears, and smaller 

mammals for den sites and shelter. 

Figure 6@-Black bears forage extensively on carpenter ants and beetle 

larvae in logs during late summer and fall. 

Figure 6lSlash piles provide cover for wtldlife. 

37 
years, thus diminishing their wildlife habitat values even if

such logs are well distributed and of large size (Maser and

others 1979). The works of Maser and Trappe (1984) and

Lofroth (in press) are excellent sources for more information

on the dead wood cycle and terrestrial and aquatic life

processes in logs.

The Log Resource

Size, species, and-number of fogs-These factors may be

the most basic ones in describing the log resource in terms of

its use by wildlife. Little information exists on the significant descriptive features for log resources. Appendix B

provides a sample data form for inventories of the down log

resource. Even determining the species of a decayed down

log can be challenging, especially when some or all of the

branches, cones, and bark are missing. Parks and others (in

press) have prepared a field guide as an aid to identifying

species of snags and logs of the interior Columbia River

basin.

Bull and Holthausen (1993) found that in 38 percent of their

observations of foraging pileated woodpeckers, the birds used

Douglas-fir and western larch logs in mixed-conifer stands.

Moreover, these birds favored logs that were 15 inches or

greater in large-end diameter and in advanced stages of decomposition. A companion study to determine log characteristics

that influenced the ant prey of woodpeckers showed the same

pattern in occupation of logs by carpenter ants (Torgersen and

Bull 1995), the primary prey of pileated woodpeckers

(Beckwith and Bull 1985).

Determining whether wildlife use of particular logs is related

to the species or to the size of the log is difficult. In studies by

Torgersen and Bull (1995) lodgepole pine, which had the

smallest mean diameters of logs, rarely supported populations of

the wood-dwelling ants used as food by pileated woodpeckers.

Conversely, western larch, Douglas-fir, and grand fir, which had

the largest mean diameters, commonly supported these ant

colonies. More specifically, the study determined that western

larch logs were preferred for pileated woodpecker foraging and

for colonization by wood-dwelling ants. Larch also had the

greatest mean large-end diameters ( 13 inches) and represented

about 14 percent of the logs, but their proportional use was far

greater. Douglas-fir, grand fir, and ponderosa pine logs had

mean diameters of about 12 inches and represented about 58

percent of the logs in the mixed-conifer study stands. Their use

by ants and foraging woodpeckers approximated their representation in the total log resource. Lodgepole pine logs, however,

which averaged only 9 inches in large-end diameter and

represented 18 percent of the logs, were used much less than

their representation among all logs. From the standpoint of ant

colonization and woodpecker foraging, log size may be more

important than species (Bull and Holthausen 1993, Torgersen

and Bull 1995).

Another characteristic describing log resources is the length

of logs. This is expressed as mean length of logs or total linear

length of logs per acre. Data on lengths of logs in late- and oldstructure mixed-conifer stands in northeastern Oregon indicate

that for all species 6 inches or larger in large-end diameter, logs

averaged 34 feet. Mean length for logs 15 inches or larger in

large-end diameter was 47 feet. Among species for all diameter

classes, ponderosa pine averaged the shortest (23 feet) and

lodgepole pine the longest (45 feet). In these same stands,

overall length of logs 6 inches or greater in large-end diameter

was 2,064 to 4,928 linear feet per acre. Of this total, there were

175 to 602 linear feet of logs per acre 12 inches or greater in

diameter. Logs in this latter size range are the stated size of logs

for wildlife habitat in the Regional Forester’s Decision Notice to

adopt Eastside Forest Plan Amendment No. 2 (U.S. Department

of Agriculture 1995). For mixed-conifer stands east of the

Cascade Range, this Plan Amendment stipulates 15 to 20 logs

per acre, 6 or more feet long, with a total linear length of 100 to

140 feet of logs 12 inches or greater in small-end diameter. The

above limited data suggest that the target linear length stipulated

in the Plan Amendment is considerably less than observed in 15

study stands (Torgersen 1997).

Studies by Bull and Holthausen (1993) and Torgersen and

Bull (1995) reported about 117 logs per acre in 12 latestructure mixed-conifer stands. In these studies, all logs that

had at least 6 feet of their length in the 0.1 -acre plots were

tallied. This criterion resulted in a misleading density of logs

per acre. Further interpretation of only logs whose mid

lengths fell within the 0.l-acre plots indicated that the actual

number of logs per acre was 24 percent less than the total

number of logs entering the plots. Thus, an average number

of 88.8 logs per acre (standard error [SE] = 6.9) more

accurately describes the true density of logs in the 12 home

ranges of pileated woodpeckers in that study. Using the

mean length of 34 feet per log translates to 3,026 linear feet

of logs per acre in these home ranges.

Additional research in six stands of old-growth mixed

conifers in northeastern Oregon showed an average of 92.9

logs per acre (SE = 11.9). Inventories in four stands of lateseral mixed conifers in northeastern Oregon showed an

average of 88.5 logs per acre (SE = 14.5). The similarity in

log densities among 27 widely distributed stands in four

counties in northeastern Oregon suggest that log resources

may be quite similar, about 90 logs per acre, in late- and oldseral stands of mixed conifers there (Torgersen 1996).

Inventories of logs in four ponderosa pine stands in

northeastern Oregon that were selectively logged for the

largest trees about 40 years ago show an average density of

45.5 logs per acre (SE = 8.3) (Torgersen 1996).

Studies conducted in coastal Douglas-fir forests west of

the Cascade Range have used percentage of ground covered

by logs as a feature against which to relate abundance of

some small vertebrates and their food, particularly hypogeous fungi (truffles and trufflelike fungi) (Amaranthus and

others 1994, Carey and Johnson 1995). Percentage of

ground covered by logs has not been a habitat feature used to

relate to wildlife in the interior Columbia River basin. We

suggest that this feature may be a good one to include in

assessments of down wood resources. Percentage of ground

covered by logs can be calculated from the data we propose

be collected in the log sampling form in appendix B.

38
Log structural classes-Logs may be in various stages of

decomposition, from sound, newly dead trees, to logs that

have deteriorated to the point of having nearly blended into

the forest floor. Exterior appearance and interior structure

differ among logs of various ages just as they do in living

trees and snags. Maser and others (1979) classified logs by

exterior appearance into log decomposition classes. In

contrast, the physical properties of internal structure and

wood soundness are here called “wood condition”--the

extent to which the wood has become soft, friable, spongy, or

pitted as a result of attack by decay-causing organisms and

channeling by invertebrates (Torgersen and Bull 1995).

The five log decomposition classes of Maser and others

(1979) describe the physical appearance of deteriorating

down trees. They characterized the classes by the presence

or absence of bark and small twigs, the texture and color of

the wood, the shape or amount of decomposition of the log,

and the amount of contact of the log with the forest floor.

Unless evidence suggests otherwise, we suggest that three

log decomposition classes are sufficient to classify the extent

of degradation of fallen trees relative to most wildlife use.

Thus we propose three log structural classes (figs. 62 and

63): log decomposition classes 1 and 2 of Maser and others

(1979) are incorporated into log structural class 1, decomposition class 3 becomes structural class 2, and decomposition

classes 4 and 5 become structural class 3.

Wood condition-Any examination of logs will show a

range of external and internal wood conditions. Some logs

may be almost uniformly sound or uniformly rotten; others

may have sound heartwood but sapwood that has become

Class 1

Class 2

Class 3

Figure 62-Three structural classes of logs.

crumbly as a result of colonization by fungi, beetle larvae, or

ants. In northeastern Oregon sites, Torgersen and Bull

(1995) used three wood condition classes (sound, moderately

decayed, and advanced decay) to describe logs. Discriminant analysis suggested that this variable was only rarely

related to either signs of foraging by pileated woodpeckers

or presence of ants. Carpenter ants, the dominant prey of

pileated woodpeckers, tended to be associated with sound 1

wood, and more specifically with sound, large-diameter

western larch.

Assessing wood condition is highly subjective but may be

estimated by using a hatchet to chop into the log at intervals

along its length. The butt end of a log may be much softer

than portions toward the small-diameter end. Because wood

conditions vary in a log and because the sampling procedure

is subjective, the relevance of wood condition to wildlife use

is unclear. Nonetheless, we have included this variable on

the sample data form for characterizing down log resources

(appendix B). The decision to record wood condition is left

to the user.

Hollow logs-Because of the exceptional values of this

structural component to wildlife, we propose that this feature

be specifically recorded in describing the character of log

resources (appendix B).

Inventory of logs-Much study has been devoted to

portraying amounts of down material as fire fuels (Fischer

1981a, 1981b, 1981c; Koski and Fischer 1979; Maxwell and

Ward 1976, 1980). The breakdown into tonnages or volumes

and the photo series for classifying forest residues, however,

are of limited utility to biologists who want to describe log

resources in ways that are relevant to use by wildlife.

Management agencies already need estimates of log resources in stands to assure compliance with stated management goals in planning documents.

A survey of logs along transects and in fixed-size plots

can be used to estimate numbers of logs per acre, species

composition, and proportion of logs by diameter-class in

selected stands (appendix C). The line transect method for

assessing log resources was adapted from sampling techniques used to determine volume and tonnage of down

woody fuels (Brown 1974, Brown and others 1982). A

modification of this method uses 18 clusters of three 75-foot

transects to characterize log populations in stands up to about

30 acres (Ottmar 1996). The fixed-plot method uses 18-20

circular or square 1/40th-acre plots to determine log populations in a 30-acre stand. See appendix C for detailed

descriptions of these sampling schemes.

Information on numbers, sizes, and other characteristics

of logs that produce suitable habitat for wildlife is scanty.

The information given here is based on our research, which

is limited to mixed-conifer stands in known pileated woodpecker home ranges (Bull and Holthausen 1993, Torgersen

and Bull 1995) or data from other selected stands in the Blue

Mountains of northeastern Oregon (Torgersen 1996). The

management options offered above are based on preliminary

information, and we anticipate that management will adopt

different options as new information becomes available.

39
Review

l Size, species, and number of logs per acre are fundamental descriptors of the suitability of log resources for

wildlife.

l Logs 15 inches or greater in large-end diameter are

particularly important for species such as pileated woodpeckers.

l In mixed-conifer stands, logs of western larch, Douglasfir, and grand fir were favored for foraging by pileated

woodpeckers in northeastern Oregon.

l Late- and old-seral stands of mixed conifers have about 90

logs per acre in northeastern Oregon.

l Logs averaged 34 feet long in mixed-conifer stands in

northeastern Oregon, but logs should be as long as

possible to offer the greatest range in diameters.

l Hollow logs of any species and size class are important

structural components to favor.
Figure 63-Three structural classes of logs. 

41 
PN
This document presents new information on the retention 

and selection of trees and logs most valuable to wildlife. 

This new information may be useful in the forest planning 

process. As additional information becomes available, 

agencies can incorporate it into their management guidelines. 

Current direction for providing wildlife habitat on public 

forest lands does not reflect this new information. Since the 

publication of Thomas and others (1979), new research suggests 

that to fully meet the needs of wildlife, additional snags and 

habitat are required for foraging, demring, nesting, and roosting. 

Although we do not suggest specific numbers of snags to retain 

by forest type, two recent studies indicate that viable woodpecker populations occurred in areas with about four snags per 

acre pull and Holthausen 1993, Dixon 1995). 

We suggest that the next step in snag management should 

involve creating a model that incorporates the new information on woodpecker foraging substrates (live trees, snags, 

and logs), home range sizes, number and characteristics of 

roost trees, multiple occupancy of snags, and needs for other 

habitat structures. Once this information is incorporated, the 

model may suggest changes to guidelines that specify 

numbers of snags and other habitat features by forest type 

and geographic area. Additional information on fall rates of 

snags, foraging needs of black-backed and three-toed 

woodpeckers, relation of the density of woodpeckers to that 

of secondary cavity nesters, and relation of snag density to 

woodpecker density would greatly improve the model. 

Although hollow trees provide benefits to many wildlife 

species, no framework regarding their management exists. 

Additional research is needed to clarify how and when heartrot decay is initiated, and how long hollow trees persist. 

Management actions that foster the development and 

retention of hollow trees need to be developed. 

In spite of the value of dwarf mistletoe brooms to 

wildlife, many managers are still reluctant to retain such 

structures in stands. With creative management, selected 

areas can be identified in which to retain trees with dwarf 

mistletoe brooms but still minimize the risk of spread of 

dwarf mistletoe to the rest of the stand. Information presented here suggests that retaining trees with brooms caused 

by broom rusts or Elytroderma offers little risk of tree 

mortality within a stand. 

We are just beginning to recognize the importance of logs 

in wildlife management. Inventories in 22 areas in northeastern Oregon showed that late- and old-seral stands of mixed 

conifers contained about 90 logs per acre. These inventories 

raise questions regarding current guidelines that call for only 

6 to 20 logs per acre. Logs are important not just for wildlife 

but for maintenance of nutrient recycling, water economy, 

and structural properties for plant growth and soil development that logs provide. 

For any management plan to be effective, a reasonable 

estimate of existing conditions is essential. To obtain this 

information, inventories of snags, logs, hollow trees, and 

trees with brooms can be done by using techniques recommended in this text. For down logs, the minimum information needed for wildlife purposes are large-end diameters of 

logs, lengths, and numbers per acre. Fuel inventories do not 

provide this information. Once existing conditions are 

known, management direction can dictate the number and 

type of structures to retain and the number that can be 

removed without jeopardizing wildlife objectives. 

We hope that this document will provide some 

new and utilitarian information for land managers 

and planners with which to better manage for 

wildlife. All of these structures provide 

diversity in the forest ecosystem that in turn 

provides diversity in wildlife. 

43 
ACKNOWLEDGMENTS

Additional information was provided by Lisa Bate,

Michelle Craig, Rita Dixon, Diane Evans, Riley McClelland,

and Victoria Saab. Drawings were provided by Janet

Hohmann and Susan Lindstedt. The following people

reviewed all or portions of the text:

Thomas Atzet, USDA Forest Service, Grants Pass, OR;

Stan Barras, USDA Forest Service, Washington, DC; Lisa

Bate, Moscow, ID; Jerry Beatty, USDA Forest Service,

Sandy, OR; Martha Brookes, Pacific Northwest Research

Station, Corvallis, OR, Diane Evans, Pacific Northwest

Research Station, Olympia, WA; Mary Lou Fairweather,

USDA Forest Service, Flagstaff, AZ; Gregory Filip, Oregon

State University, Corvallis, OR; Russell Graham, Intermountain Research Station, Moscow, ID; Brian Geils, Rocky

Mountain Research Station, Flagstaff, AZ; Scott Harrison,

British Columbia Ministry of Forests, Prince Rupert, British

Columbia; Diane Hildebrand, USDA Forest Service,

Portland, OR; Richard Holthausen, USDA Forest Service,

Flagstaff, AZ; Philip Jahns, USDA Forest Service, Klamath

Falls, OR, Susan Johnson, USDA Forest Service, Paulina,

OR; Helen Maffei, USDA Forest Service, Bend, OR; Robert

Mathiasen, Idaho Department of Lands, Couer d’Alene, ID;

James McIver, Blue Mounains Natural Resources Institute.

La Grande, OR; Kim Mellen, USDA Forest Service,

Gresham, OR; Mark Penninger, USDA Forest Service, La

Grande, OR, Mary Rowland, La Grande, OR; Victoria Saab,

Intermountain Research Station, Boise, ID; Craig Schmitt,

USDA Forest Service, La Grande, OR; Karen Shimamoto,

USDA Forest Service, Sisters, OR; Lynn Starr, Pacific

Northwest Research Station, La Grande, OR; James Stone,

USDA Forest Service, Crescent, OR; John Teply, USDA

Forest Service, Portland, OR; Robert Tinnin, Portland State

University, Portland, OR; Michael Wisdom, USDA Forest

Service, La Grande, OR; Shelly Witt, USDA Forest Service,

Logan, UT

44
REFERENCES

Akenson, James J.; Henjum, Mark G. 1994. Black bear

den site selection in the Starkey study area. Natural

Resource News. La Grande, OR: Blue Mountains Natural

Resources Institute. 4(2): l-2.

Alexander, Martin E.; Hawksworth, Frank G. 1975.

Wildland fires and dwarf mistletoes: a literature review of

ecology and prescribed burning. Gen. Tech. Rep. RM-14.

Fort Collins, CO: U.S. Department of Agriculture, Forest

Service, Rocky Mountain Forest and Range Experiment

Station. 12 p.

Amaranthus, Michael; Trappe, James M.; Bednar,

Larry; Arthur, David. 1994. Hypogeous fungal

production in mature Douglas-fir forest fragments and

surrounding plantations and its relation to coarse woody

debris and animal mycophagy. Canadian Journal of Forest

Research. 24(11): 2157-2165.

Bartels, Ronald; Dell, John D.; Knight, Richard L.;

Schaefer, Gail. 1985. Dead and down woody material.

In: Brown, E. Reade, tech. ed. Management of wildlife

and fish habitats in forests of western Oregon and

Washington. Part 1: Chapter narratives. Portland, OR:

U.S. Department of Agriculture, Forest Service, Pacific

Northwest Region: 171 - 186.

Bate, Lisa Jean. 1995. Monitoring woodpecker abundance

and habitat in the central Oregon Cascades. Moscow, ID:

University of Idaho. 116 p. M.S. thesis.

Bate, Lisa J.; Garton, Edward 0.; Wisdom, Michael J.

[In preparation]. Estimating snag and large tree densities and distributions on a landscape for woodpecker

management. Gen. Tech. Rep. Portland, OR: U.S.

Department of Agriculture, Forest Service, Pacific

Northwest Research Station.

Beckwith, Roy C.; Bull, Evelyn L. 1985. Scat analysis of

the arthropod component of pileated woodpecker diet.

Murrelet. 66: 90-92.

Bega, Robert V., tech. coord. 1978. Diseases of Pacific

Coast conifers. Agric. Handb. 521. Washington, DC: U.S.

Department of Agriculture. 199 p.

Bennetts, Robert E.; White, Gary C.; Hawksworth,

Frank G.; Severs, Scott E. 1996. The influence of

dwarf mistletoe on bird communities in Colorado

ponderosa pine forests. Ecological Applications. 6: 899-

909.

Bevis, Kenneth R. 1996. Primary cavity excavators in grand

fir forests of Washington’s east Cascades and forestry on

the Yakama Indian Nation, Washington. In: Bradford,

Peter; Manning, Todd; l’Anson, Bill, eds. Wildlife tree/

stand-level biodiversity workshop proceedings; 1995

October 17-18; Victoria, BC. Victoria, BC: British

Columbia Environment: 77-86.

Boyce, John Shaw. 1938. Forest pathology in forest practice. New York: John Wiley and Sons, Inc. 600 p.

Broadbooks, H.E. 1958. Life history and ecology of the

chipmunk, Eutamias amoenus, in eastern Washington.

Misc. Publ. 103. Ann Arbor, MI: University of Michigan,

Museum of Zoology. 42 p.

Brown, H.P.; Panshin, A.J.; Forsaith, C.C. 1949. Textbook

of wood technology. Volume 1: Structure, identification,

defects, and uses of the commercial woods of the United

States. New York: McGraw-Hill. 34 p.

Brown, James K. 1974. Handbook for inventorying downed

woody material. Gen. Tech. Rep. INT-16. Ogden, UT:

U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 24 p.

Brown, James K.; Oberheu, Rick D.; Johnson,

Cameron M. 1982. Handbook for inventorying surface

fuels and biomass in the Interior West. Gen. Tech. Rep.

INT-129. Ogden, UT: U.S. Department of Agriculture,

Forest Service, Intermountain Forest and Range

Experiment Station. 48 p.

Brown, Timothy K. 1996. Snags and wildlife tree preservation and enhancement. In: Bradford, Peter; Manning,

Todd; l’Anson, Bill, eds. Wildlife tree/stand-level

biodiversity workshop proceedings; 1995 October 17-18;

/

Victoria, BC. Victoria, BC: British Columbia Environment: 71-75.

Bull, Evelyn L. 1983. Longevity of snags and their use by

woodpeckers. In: Snag habitat management: Proceedings

of a symposium; 1983 June 7-9; Flagstaff, AZ. Gen.

Tech. Rep. RM-99. Fort Collins, CO: U.S. Department of

Agriculture, Forest Service, Rocky Mountain Forest and

Range Experiment Station: 64-67.

Bull, Evelyn L. 1986. Resource partitioning among woodpeckers in northeastern Oregon. Moscow, ID: University

of Idaho. 109 p. Ph.D. dissertation.

45
Bull, Evelyn L. 1995. Progress report on American marten

home range and habitat use. Portland, OR: U.S. Department

of Agriculture, Forest Service, Pacific Northwest Research

Station. 21 p. Unpublished report. On file with: Pacific

Northwest Research Station, Forestry and Range Sciences

Laboratory, 1401 Gekeler Lane, La Grande, OR 97850.

Bull, Evelyn L. 1996a. Use of hollow trees by Vaux’s swifts.

Portland, OR: U.S. Department of Agriculture, Forest

Service, Pacific Northwest Research Station. 2 p. Unpublished data. On file with: Pacific Northwest Research

Station, Forestry and Range Sciences Laboratory, 1401

Gekeler Lane, La Grande, OR 97850.

Bull, Evelyn L. 1996b. Owl nests in brooms caused by

dwarf mistletoe and Elytroderma disease. Portland, OR:

U.S. Department of Agriculture, Forest Service, Pacific

Northwest Research Station. 4 p. Unpublished data. On

file with: Pacific Northwest Research Station, Forestry

and Range Sciences Laboratory, 1401 Gekeler Lane, La

Grande, OR 97850.

Bull, Evelyn L. 1996c. Longevity of created snags. Portland,

OR: U.S. Department of Agriculture, Forest Service,

Pacific Northwest Research Station. 25 p. Unpublished

data. On file with: Pacific Northwest Research Station,

Forestry and Range Sciences Laboratory, 1401 Gekeler

Lane, La Grande, OR 97850.

Bull, Evelyn L.; Collins, Charles T. 1993. Vaux’s swift

(Chaetura vanxi). In: Poole, A.; Gill, E., eds. The birds of

North America, No. 77. Philadelphia, PA: The Academy

of Natural Sciences; Washington, DC: The American

Ornithologists’ Union. 12 p.

Bull, Evelyn L.; Henjum, Mark G. 1990. Ecology of the

great gray owl. Gen. Tech. Rep. PNW-265. Portland, OR:

U.S. Department of Agriculture, Forest Service, Pacific

Northwest Research Station. 39 p.

Bull, Evelyn L.; Holthausen, Richard S. 1993. Habitat use

and management of pileated woodpeckers in northeastern

Oregon. Journal of Wildlife Management. 57: 335-345.

Bull, Evelyn L.; Holthausen, Richard S.; Henjum,

Mark G. 1992. Roost trees used by pileated woodpeckers in northeastern Oregon. Journal of Wildlife

Management. 56: 786-793.

Bull, Evelyn L.; Holthausen, Richard S.; Marx, David B.

1990. How to determine snag density. Western Journal of

Applied Forestry. 5: 56-58.

Bull, Evelyn L.; Partridge, Arthur D. 1986. Methods of

killing trees for use by cavity nesters. Wildlife Society

Bulletin. 14: 142-146.

Bull, Evelyn L.; Twombly, Asa D.; Quigley, Thomas M.

1980. Perpetuating snags in managed mixed conifer

forests of the Blue Mountains, Oregon. In: Management

of western forests and grasslands for nongame birds,

workshop proceedings; 1980 February 11-14; Salt Lake

City, UT. Gen. Tech. Rep. INT-86. Ogden, UT: U.S.

Department of Agriculture, Forest Service, Intermountain

Forest and Range Experiment Station: 325-336.

Bull, Evelyn L.; Wright, Anthony L.; Henjum, Mark G.

1989. Nesting and diet of long-eared owls in conifer

forests, Oregon. Condor. 91: 908-912.

Burnett, Gary W. 1981. Movements and habitat use of

American marten in Glacier National Park, Montana.

Missoula, MT: University of Montana. 130 p. M.S. thesis.

Buskirk, Steven W.; Harlow, Henry J.; Forrest, Steven C.

1987. Studies on the resting site ecology of marten in the

central Rocky Mountains. In: Troendle, Charles A.;

Kaufmann, Merrill R.; Hamre, R.H.; Winokur, R.P., tech.

coords. Management of subalpine forests: building on 50

years of research: Proceedings of a technical conference;

1987 July 6-9; Silver Creek, CO. Gen. Tech. Rep. RM149. Fort Collins, CO: U.S. Department of Agriculture,

Forest Service, Rocky Mountain Forest and Range

Experiment Station: 150-153.

Campbell, Thomas M., III. 1979. Short-term effects of

timber harvests on pine marten ecology. Fort Collins, CO:

Colorado State University. 71 p. M.S. thesis.

Carey, Andrew B.; Johnson, Murray L. 1995. Small

mammals in managed, naturally young, and old-growth

forests. Ecological Applications. 5(2): 336-352.

Chambers, Carol. 1997. Personal communication, associate

professor. Northern Arizona University, Department of

Ecosystem Management, Box 15018, Flagstaff, AZ 86001.

Childs, T.W.; Shea, Keith R.; Stewart, James L. 1971.

Elytroderma disease of ponderosa pine. [Leaflet 42.]

[Portland, OR]: U.S. Department of Agriculture, Forest

Service, Forest Insect and Disease. 6 p.

Cimon, Norm. 1983. A simple model to predict snag levels

in managed forests. In: Snag habitat management:

Proceedings of a symposium; 1983 June 7-9; Flagstaff,

AZ. Fort Collins, CO: U.S. Department of Agriculture,

Forest Service, Rocky Mountain Forest and Range

Experiment Station: 200-204.

Clary, Warren P.; Larson, Fredrick R. 1971. Elk and deer

use are related to food sources in Arizona ponderosa pine.

Res. Note 202. Fort Collins, CO: U.S. Department of

Agriculture, Forest Service, Rocky Mountain Forest and

Range Experiment Station. 4 p.

46
Conner, Richard N.; Locke, Brian A. 1982. Fungi and redcockaded woodpecker cavity trees. Wilson Bulletin. 94:

64-70.

Craig, Michelle FIury. 1995. Pierce District cumulative effects

analysis process for snag habitat. Kamiah, ID: U.S. Department of Agriculture, Forest Service, Pierce Ranger District.

5 p. Unpublished report. On file with: Pierce Ranger

District, Route 2, Box 191, Kamiah, ID 83536.

Craighead, John J.; Craighead, Frank C.; Roff, Robert L.;

O’Gara, Bart W. 1973. Home ranges and activity patterns

of nonmigratory elk of the Madison Drainage herd as

determined by biotelemetry. Wildlife Monograph. 33: l-50.

Dahms, Walter G. 1949. How long do ponderosa pine snags

stand? Res. Note 57. Portland, OR: U.S. Department of

Agriculture, Forest Service, Pacific Northwest Forest and

Range Experiment Station. 3 p.

De Vries, P.G. 1973. A general theory on line intersect

sampling with application to logging residue inventory.

Wageningen, The Netherlands: Mededelingen

Landbouwhogeschool 73-11. 23 p.

Dimock, Edward J., II. 1974. Animal populations and

damage. In: Environmental effects of forest residues

management in the Pacific Northwest: a state-of-knowledge

compendium. Gen. Tech. Rep. PNW-24. Portland, OR: U.S.

Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station: l-28.

Dixon, Rita Dianne. 1995. Ecology of white-headed

woodpeckers in the central Oregon Cascades. Moscow,

ID: University of Idaho. 148 p. M.S. thesis.

Evans, Diane; Martens, Dean. 1995. Snag and coarse

woody debris guidelines for timber harvest projects.

McCall, ID: Payette National Forest. 24 p.

Fairweather, Mary Lou. 1995. Post-treatment biological

evaluation of the 1981 Tusayan dwarf mistletoe (DM)

control project. Albuquerque, NM: U.S. Department of

Agriculture, Forest Service, Southwestern Region. 8 p.

Fischer, William C. 1981a. Photo guide for appraising

downed woody fuels in Montana forests: grand fir-larchDouglas-fir, western hemlock, western hemlock-western

redcedar, and western redcedar cover types. Gen. Tech.

Rep. INT-96. Odgen, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range

Experiment Station. 53 p.

Fischer, William C. 1981b. Photo guide for appraising

downed woody fuels in Montana forests: interior ponderosa pine, ponderosa pine-larch-Douglas-fir, larchDouglas-fir, and interior Douglas-fir cover types. Gen.

Tech. Rep. INT-97. Odgen, UT: U.S. Department of

Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station. 133 p.

Fischer, William C. 1981c. Photo guide for appraising

downed woody fuels in Montana forests: lodgepole pine,

and Engelmann spruce-subalpine fir cover types. Gen.

Tech. Rep. INT-98. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station. 143 p.

Forsman, Eric D.; Meslow, E. Charles; Wight, Howard M.

1984. Distribution and biology of the spotted owl in Oregon.

Wildlife Monograph. 87: l-64.

Gartner, Barbara L. 1995. Patterns of xylem variation

within a tree. In: Gartner, Barbara L., ed. Plant stems:

physiology and functional morphology. New York:

Academic Press: 125-145.

Goggans, Rebecca; Dixon, Rita; Seminara, L. Claire. 1988.

Habitat use by three-toed and black-backed woodpeckers,

Deschutes National Forest, Oregon. Nongame Rep. 87-3-02.

[Portland, OR]: Oregon Department of Fish and Game. 49 p.

Hamilton, R.J.; Marchinton, R.L. 1980. Denning and

related activities of black bears in the coastal plain of

North Carolina. International Conference of Bear Research and Management. 4: 121-126.

Hann, Wendel J.; Jones, Jeffrey L.; Karl, Michael G.

[and others]. [In press]. Landscape dynamics of the

basin. In: Quigley, Thomas M.; Arbelbide, S.J., tech. eds.

An assessment of ecosystem components in the interior

Columbia basin and portions of the Klamath and Great

Basins. Gen. Tech. Rep. Portland, OR: U.S. Department

of Agriculture, Forest Service, Pacific Northwest Research Station. Chapter 3. (Quigley, Thomas M., ed.

Interior Columbia Basin Ecosystem Management Project:

scientific assessment).

Harmon, Mark E.; Franklin, Jerry F.; Swanson,

Fredrick J. [and others]. 1986. Ecology of coarse

woody debris in temperate ecosystems. In:

MacFadyen, A; Ford, E.D., eds. Advances in

ecological research. Orlando, FL: Academic Press,

Inc. 15: 133-302.

Harrison, Scott. 1996. Personal communication, wildlife

habitat ecologist. British Columbia Ministry of Forests,

Research Section, 1011 4th Avenue, Prince George, BC.

Canada V2L 3H9.

Hawksworth, Frank G. 1992. Personal communication,

research forest pathologist (deceased). Rocky Mountain

Forest and Range Experiment Station, 240 W. Prospect

Rd., Fort Collins, CO 80526-2098.

47
Hawksworth, Frank G.; Nicholls, Thomas H.; Merrill,

Laura M. 1987. Long-distance dispersal of lodgepole

pine dwarf mistletoe. In: Troendle, Charles A.;

Kauhnann, Merrill R.; Hamre, R.H.; Winokur, R.P., tech.

coords. Management of sublpine forests: building on 50

years of research: Proceedings of a conference; 1987 July

6-9; Silver Creek, CO. Gen. Tech. Rep. RM-149. Fort

Collins, CO: U.S. Department of Agriculture, Forest

Service, Rocky Mountain Forest and Range Experiment

Station: 220-226.

Hawksworth, Frank G.; Shaw, Charles G., III. 1984.

Damage and loss caused by dwarf mistletoes in coniferous forests of western North America. In: Wood, R.K.S.;

Jellis, G.J., eds. Plant diseases: infection, damage and

loss. Oxford: Blackwell Scientific Publications: 285-297.

Hawksworth, Frank G.; Wiens, Delbert. 1996. Dwarf

mistletoes: biology, pathology, and systematics. Geils, B.;

Nisley, R., eds. Agric. Handb. 709. Washington, DC: U.S.

Department of Agriculture. 410 p.

Henjum, Mark; Akenson, James. 1996. Personal communication, wildlife biologists, Oregon Department of Fish

and Wildlife, 107 20th Street, La Grande, OR 97850.

Hepting, George H. 1971. Diseases of forest and shade trees

of the United States. Agric. Handb. 386. Washington,

DC: U.S. Department of Agriculture. 658 p.

Hessburg, Paul F.; Mitchell, Russel G.; Filip, Gregory M.

1994. Historical and current roles of insects and pathogens in eastern Oregon and Washington forested landscapes. Gen. Tech. Rep. PNW-327. Portland, OR: U.S.

Department of Agriculture, Forest Service, Pacific

Northwest Research Station. 72 p.

Hinds, Thomas E.; Hawksworth, Frank G.; Davidson,

Ross W. 1965. Beetle-killed Engelmann spruce--its

deterioration in Colorado. Journal of Forestry. 63: 536-

542.

Hooper, Robert G.; Lennartz, Michael R.; Muse, H.

David. 1991. Heart rot and cavity tree selection by redcockaded woodpeckers. Journal of Wildlife Management.

55: 323-327.

Hooven, Edward F. 1971. The porcupine in Oregon: its life

history and control. Res. Publ. 10. Corvallis, OR: Oregon

State University, Forest Research Laboratory. 22 p.

Johnson, Mark K.; Carey, Andrew B. 1979. Porcupine

pellet pH, color, and composition. Southwestern Naturalist. 24: 544-545.

Keen, F.P. 1955. The rate of natural falling of beetle-killed

ponderosa pine snags. Journal of Forestry. 53: 720-723.

48

Kimmey, James W. 1955. Rate of deterioration of fire-killed

timber in California. Circular 962. Washington, DC: U.S.

Department of Agriculture. 22 p.

Koehler, Gary M.; Aubry, Keith B. 1994. Lynx. In:

Ruggiero, Leonard F.; Aubry, Keith B. [and others], tech.

eds. The scientific basis for conserving forest carnivores.

Gen. Tech. Rep. RM-254. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain

Forest and Range Experiment Station: 74-98.

Koski, Wayne H.; Fischer, William C. 1979. Photo series

for appraising thinning slash in northern Idaho: western

hemlock, grand fir, and western redcedar timber types.

Gen. Tech. Rep. INT-46. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station. 50 p.

Lawrence, William H. 1957. Porcupine control: a problem

analysis. Forestry Research Notes. Centralia, WA:

Weyerhaeuser Timber Company. 43 p.

Leach, Howard R; Hiele, Jack L. 1957. Food habits of the

Tehama deer herd. California Fish and Game. 43: 161-178.

Lemons, Daniel Eugene. 1978. Small mammal dissemination of dwarf mistletoe seeds. Portland, OR: Portland

State University. 38 p. M.S. thesis.

Li, P.; Martin, T.E. 1991. Nest-site selection and nesting

success of cavity-nesting birds in high elevation forest

drainages. Auk. 108: 405-418.

Lofroth, Eric C. 1993. Scale dependent analyses of habitat

selection by marten in the sub-boreal spruce

biogeoclimatic zone, British Columbia. Burnaby, BC:

Simon Fraser University. 109 p. M.S. thesis.

Lofroth, Eric C. [In press]. The dead wood cycle. In Voller,

Joan; Harrison, Scott, eds. Conservation biology principles

for forested landscapes. Vancouver, BC: University of

British Columbia Press. [Pages unknown]. Chapter 8.

Lyon, Jack L. 1977. Attrition of lodgepole pine snags on

the Sleeping Child Bum, Montana. Res. Note INT-219.

Ogden, UT: U.S. Department of Agriculture, Forest

Service, Intermountain Forest and Range Experiment

Station. 4 p.

Machmer, Marlene M.; Steeger, Christoph. 1995. The

ecological roles of wildlife tree users in forest ecosystems.

Victoria, BC: British Columbia Ministry of Forests. 54 p.

Manion, Paul D. 1981. Tree disease concepts. Englewood

Cliffs, NJ: Prentice-Hall, Inc. 399 p.
Martin, Sandra K.; Beatty, Jerome S.; Hawksworth,

Frank G. 1992. Douglas-fir dwarf mistletoe brooms and

spotted owl nesting habitat, eastern Cascade Range,

Washington. In: Frankel, Susan, comp. Proceedings, 40th

annual western international forest disease work conference; 1992 July 13-17; Durango, CO. San Francisco, CA:

U.S. Department of Agriculture, Forest Service, Forest

Pest Management: 77-79.

Martinka, Robert R. 1972. Structural characteristics of blue

grouse territories in southwestern Montana. Journal of

Wildlife Management. 36: 498-5 10.

Maser, Chris; Anderson, Ralph G.; Cromack, Kermit, Jr.

[and others]. 1979. Dead and down woody material. In:

Thomas, Jack Ward, tech. ed. Wildlife habitats in managed forests: the Blue Mountains of Oregon and Washington. Agric. Handb. 553. Washington, DC: U.S.

Department of Agriculture: 78-95.

Maser, Chris; Trappe, James M., tech. eds. 1984. The seen

and unseen world of the fallen tree. Gen. Tech. Rep.

PNW-164. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.

56 p.

Mathiasen, Robert L. 1996. Dwarf mistletoes in forest

canopies. Northwest Science. 70: 61-71.

Maxwell, Wayne G.; Ward, Franklin R. 1976. Photo series

for quantifying forest residues in the: ponderosa pine type,

ponderosa pine and associated species type, lodgepole pine

type. Gen. Tech. Rep. PNW-52. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest

Forest and Range Experiment Station. 73 p.

Maxwell, Wayne G.; Ward, Franklin R. 1980. Photo series

for quantifying natural forest residues in common

vegetation types of the Pacific Northwest. Gen. Tech.

Rep. PNW-105. Portland, OR: U.S. Department of

Agriculture, Forest Service, Pacific Northwest Research

Station. 230 p.

McClelland, Bernard Riley. 1977. Relationships between

hole-nesting birds, forest snags, and decay in western

larch-Douglas-fir forests of the northern Rocky Mountains. Missoula, MT: University of Montana. 483 p. Ph.D.

dissertation.

McClelland, B. Riley; Frissell, Sidney S.; Fischer, William C.;

Halvorson, Curtis H. 1979. Habitat management for hole

nesting birds in forests of western larch and Douglas-fir Journal

of Forestry. 77: 480-483.

Mellen, Teresa Kim. 1987. Home range and habitat use of

pileated woodpeckers, western Oregon. Corvallis, OR:

Oregon State University. 96 p. M.S. thesis.

Mielke, James L. 1950. Rate of deterioration of beetle-killed

Engehnann spruce. Journal of Forestry. 48: 882-888.

Mowrey, Robert A.; Zasada, J.C. 1984. Den tree use and

movements of northern flying squirrels in interior Alaska

and implications for forest managers. In: Meehan,

William R.; Merrell, T.R.; Hanley, Thomas A., eds. Fish

and wildlife relationships in old-growth forests: Proceedings of a symposium; 1982 April 12-15; Juneau, AK.

Morehead City, NC: American Institute of Fishery

Research Biologists: 351-356.

Nagorsen, David W.; Brigham, R. Mark. 1993. Bats of

British Columbia. Volume 1: The mammals of British

Columbia. Royal British Columbia Museum Handbook.

Vancouver, BC: University of British Columbia Press.

Nicholls, Thomas H.; Hawksworth, Frank G.; Merrill,

Laura M. 1984. Animal vectors of dwarf mistletoe, with

special reference to Arceuthobium americanurn on

lodgepole pine. In: Hawksworth, F.G.; Scharpf, R.F., eds.

Biology of dwarf mistletoes: Proceedings of a symposium; 1984 August 8; Fort Collins, CO. Gen. Tech. Rep.

RM- 111. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range

Experiment Station: 102- 11O.

Neitro, William A.; Binkley, Virgil W.; Cline, Steven P. [and

others]. 1985. Snags (wildlife trees). In Brown E. Reade,

tech. ed. Management of wildlife and fish habitats in forests

of western Oregon and Washington. Part 1: Chapter

narratives. Portland, OR U.S. Department of Agriculture,

Forest Service, Pacific Northwest Region: 129- 169.

Noble, William 0.; Meslow, E. Charles; Pope, Michael D.

1990. Denning habits of black bears in the central Coast

Range of Oregon. Corvallis, OR: Oregon State University, Department of Fisheries and Wildlife. [Pages

unknown].

Ottmar, Roger. 1996. Personal communication, research

forester, Pacific Northwest Research Station, Forestry

Sciences Laboratory, 4043 Roosevelt Way NE, Seattle,

WA 98105-6497.

Parks, Catherine G. 1996a. Bear trees--an eastern Oregon

landscape legacy. [Brochure]. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest

Research Station. [Not paged].

Parks, Catherine G. 1996b. Woodpecker use and longevity

of snags created by killing ponderosa pine infected with

dwarf mistletoe. Portland, OR: U.S. Department of

Agriculture, Forest Service, Pacific Northwest Research

Station. 5 p. Unpublished report. On file with: Pacific

Northwest Research Station, Forestry and Range Sciences

Laboratory, 1401 Gekeler Lane, La Grande, OR 97850.

49
Parks, Catherine G.; Bull, Evelyn L.; Filip, Gregory M.

1996a. Using artificially inoculated decay fungi to create

wildlife habitat. In: Bradford, Peter; Manning, Todd;

l’Anson, Bill, eds. Wildlife tree/stand-level biodiversity

workshop proceedings; 1995 October 17-18; Victoria,

BC. Victoria, BC: British Columbia Environment: 87-89.

Parks, Catherine G.; Bull, Evelyn L.; Filip, Gregory M.;

Gilbertson, R.L. 1996b. Wood decay fungi associated

with woodpecker nest cavities in living western larch.

Plant Disease. 80: 959.

Parks, Catherine G.; Bull, Evelyn L.; Torgersen, Torolf

R. [In press]. Field guide to the identification of snags

and logs in the interior Columbia River basin. Gen. Tech.

Rep. PNW-390. Portland, OR: U.S. Department of

Agriculture, Forest Service, Pacific Northwest Research

Station. 41 p.

Parks, C.G.; Raley, CM.; Aubry, K.B.; Gilbertson, R.L.

1997. Wood decay associated with pileated woodpecker

roosts in western redcedar. Plant Disease 81:551.

Parks, Catherine G.; Shaw, David C. 1996. death and

decay: a vital part of living canopies. Northwest Science.

70: 46-53.

Parmeter, J.R. 1978. Forest stand dynamics and ecological

factors in relation to dwarf mistletoe spread, impact, and

control. In: Proceedings of the symposium on dwarf

mistletoe control through forest management. Gen. Tech.

Rep. PSW-31: Berkeley, CA: U.S. Department of

Agriculture, Forest Service, Pacific Southwest Forest and

Range Experiment Station: 16-30.

Pickford, Stewart G.; Hazard, John W. 1978. Simulation

studies on line transect sampling of forest residue. Forest

Science. 4: 469-483.

Powell, Roger A.; Ziellnski, William J. 1994. Fisher. In:

Ruggiero, Leonard F.; Aubry, Keith B. [and others], tech.

eds. The scientific basis for conserving forest carnivores.

Gen. Tech. Rep. RM-254. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain

Forest and Range Experiment Station: 38-73.

Raphael, Martin G.; White, M. 1984. Use of snags by

cavity-nesting birds in the Sierra Nevada. Wildlife

Monograph. 86: l-66.

Rayner, A.D.M.; Boddy, Lynne. 1988. Fungal decomposition of wood--its biology and ecology. New York: John

Wiley and Sons. 587 p.

Reynolds, Richard T.; Graham, Russell T.; Reiser, M.

Hildegard. 1992. Management recommendations for the

northern goshawk in the Southwestern United States.

Gen. Tech. Rep. RM-217. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain

Forest and Range Experiment Station. 90 p.

Reynolds, Richard T.; Meslow, E. Charles; Wight,

Howard M. 1982. Nesting habitat of coexisting accipiters

in Oregon. Journal of Wildlife Management. 46: 124- 138.

Saab, Victoria A.; Dudley, Jonathan. 1997. Responses by

cavity-nesting birds to high-intensity wildfire and postfire salvage logging in ponderosa pine/Douglas-fir forests

of southwestern Idaho. Boise, ID: U.S. Department of

Agriculture, Forest Service, Intermountain Research

Station; progress report. 34 p.

Schmid, J.M.; Mata, S.A.; McCambridge, W.F. 1985.

Natural falling of beetle-killed ponderosa pine. Res. Note

RM-454. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range

Experiment Station. 4 p.

Schommer, Tim; Collard, Ernie; Widenmann, Kurt.

1993. Wallowa-Whitman National Forest green tree snag

replacement guidelines. Baker, OR: U.S. Department of

Agriculture, Forest Service, Pacific Northwest Region,

Wallowa-Whitman National Forest. 14 p.

Scott, Donald W.; Schmitt, Craig L. 1996. Report on forest

health on National Forest lands in the Blue Mountains,

1990-1996: insects and diseases. Portland, OR: U.S.

Department of Agriculture, Forest Service, Pacific

Northwest Region. [Pages unknown]. Administrative

report BMZ-96-12. On file with: Blue Mountains Pest

Management Zone, 1401 Gekeler Lane, La Grande, OR

97850.

Severson, K.E. 1986. Spring and early summer habitats and

foods of male blue grouse in Arizona. Journal of the

Arizona-Nevada Academy of Science. 21: 13-18.

Shain, Louis. 1995. Stem defense against pathogens. In:

Gartner, B., ed. Plant stems--physiology and functional

morphology. San Diego, CA: Academic Press: 383-401.

Smith, Graham W. 1982. Habitat use by porcupines in a

ponderosa pine/Douglas-fir forest in northeastern Oregon.

Northwest Science. 56: 236-240.

Spencer, Wayne D. 1987. Seasonal rest-site preferences of

pine martens in the northern Sierra Nevada. Journal of

Wildlife Management. 51: 616-621.

Sperry, John S. 1995. Limitations on stem water transport

and their consequences. In: Gartner, B., ed. Plant stems--

physiology and functional morphology. San Diego, CA:

Academic Press: 105-120.

50
Stauffer, Dean F.; Peterson, Steven R. 1986. Seasonal

microhabitat relationships of blue grouse in southeastern

Idaho. Great Basin Naturalist. 46: 117-122.

Steeger, Christoph; Machmer, Marlene. 1995. Wildlife

trees and their use by cavity nesters in selected stands of

the Nelson Forest Region. Tech. Rep. 010. Nelson, BC:

Canada Ministry of Forests. 28 p.

Steeger, Christoph; Machmer, Marlene. 1996. Use of trees

by cavity nesters in managed and unmanaged interior

cedar-hemlock stands of southern British Columbia. In:

Bradford, Peter; Manning, Todd; 1’Anson, Bill, eds.

Wildlife tree/stand-level biodiversity workshop proceedings; 1995 October 17-18; Victoria, BC. Victoria, BC:

British Columbia Environment: 45-54.

Thomas, Jack Ward; Anderson, Ralph G.; Maser, Chris;

Bull, Evelyn L. 1979. Snags. In: Thomas, Jack Ward, ed.

Wildlife habitats in managed forests: the Blue Mountains

of Oregon and Washington. Agric. Handb. 553. Washington, DC: U.S. Department of Agriculture, Forest Service:

60-77.

Tinnin, Robert 0.; Knutson, Donald M. 1982. Witches’

broom formation in conifers infected by Arceuthobium

spp: an example of parasitic impact upon community

dynamics. American Midland Botanist. 107: 35l-359.

Tinnin, Robert 0.; Knutson, Donald M. 1985. How to

identify brooms in Douglas-fir caused by dwarf mistletoe.

Res. Note PNW-426. Portland, OR: U.S. Department of

Agriculture, Forest Service, Pacific Northwest Research

Station. 8 p.

Tobalske, Bret W. 1992. Evaluating habitat suitability using

relative abundance and fledging success of red-naped

sapsuckers. Condor. 94: 550-553.

Torgersen, Torolf R. 1997. Log resources and wildlife

relationships. Portland,OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.

25 p. Unpublished data. On file with: Pacific Northwest

Research Station, Forestry and Range Sciences Laboratory, 1401 Gekeler Lane, La Grande, OR 97850.

Torgersen, Torolf R.; Bull, Evelyn L. 1995. Down logs as

habitat for forest-dwelling ants--the primary prey of

pileated woodpeckers in northeastern Oregon. Northwest

Science. 69: 294-303.

Urness, P.J. 1969. Nutritional analysis and in vitro digestibility of mistletoes browsed by deer in Arizona. Journal

of Wildlife Management. 33: 499-505.

U.S. Department of Agriculture, Forest Service. 1995.

Decision notice for the revised continuation of interim

management direction establishing riparian, ecosystem

and wildlife standards for timber sales. Portland, OR:

U.S. Department of Agriculture, Forest Service, Pacific

Northwest Region. 13 p.

U.S. Department of Agriculture, Forest Service. 1997.

Current vegetation survey. Version 2.0. Portland, OR:

U.S. Department of Agriculture, Forest Service, Pacific

Northwest Region, Natural Resource Inventory. 115 p.

Wenger, Karl F., ed. 1984. Forestry handbook. 2d ed. New

York: John Wiley and Sons. 1335 p.

Wicker, Edward F.; Leaphart, C.D. 1974. Fire and dwarf

mistletoe (Arceuthobium spp.) relationships in the

northern Rocky Mountains. In: Proceedings, tall timbers

fire ecology conference; tire and land management

symposium; 1974 October 8-10; Missoula, MT. Tallahassee, FL: Tall Timbers Research Station: 279-298.

Wood, C.S.; Van Sickle, G.A.; Shore, T.L. 1985. Forest

insect and disease conditions, British Columbia. Info.

Rep. BC-X-259. Victoria, BC: Canada Forestry Service,

Pacific Forest Research Centre. 32 p.

Wright, J.T.; Arrington, O.N. 1950. The cooperative

Kaibab North livestock-deer forage relationship study.

Phoenix, AZ: Arizona Game and Fish Department;

Federal aid completion report project W-27-R-1,2, and 3.

223 p.

Ziller, Wolf G. 1974. The tree rusts of western Canada.

Canadian Forestry Service Publ. 1329. Victoria, BC:

Department of the Environment. 272 p.

51
52
MONITORING CREATED WILDLIFE TREES 

Forest or Location: 

Contact Person: 

Date of Treatment: 

Monitoring Crew: 

Date of Remeasurement: 

Stand or Area: - 

TREATMENT DATA 

TlWStJ9,@ 

1 =Pondmoapine 

2-w.whttedne 

3=Dwglar-iir e-~n 

4=GratuWhiteRr 10..Cottonwwd 

5-w.taJdl ll=Bifdl 

s--m 12-other 

7-w.hemtock 

5=w.radmdar 

1 = Dynamite top 

2=samtcp 

3 - lnoou!ate 

.l Fungus 

.2 FunQua 

4 = Girdle 

5=.suvldde 

B=cther 

. . Tree Congdgn 

l=Llve 

2-Cead 

3 - Broken 

4=Cown 

IMEASUREMENT DATA 

8. 

me Ed. 

Tree %Lhw Foraga Nest COmnlente 

Crown use use 

1. :j. 

Wkm use 

O-NC 

1 -Yes 
Appendix B Data Form for Inventorying Down Logs 

Log Inventory 

Forest or Location: 

Monitoring Crew: 

Stand or Area: 

Date: Contact Person: 

Stand History (burned, harvested, firewood cutting, insect/disease activity): 

Lw Lou Soecies I 00 Structural Code 

1 -Natural log 

P=Cut log 

3=Natural log 

4=&t Stump 

l=Ponderosa pine 

2=W. white pine 

3=Douglas-flr 

4=Grand/White fir 

5=W. larch 

6=Lodgepole pine 

7=W. hemlock 

6=W. red cedar 

S=Aspen 

1 O=Cottonwood 

1 l=Birch 

12=Other 

I-3; PNW GTR 

391, Figure 56 & 57 

or 

1-5; Maser and 

others (1979) 

[circle one] 

*Large diameter of log 

is taken just above 

eg;well at “stump” 

l Use “length” column 

to record height of 

stump. 

* Use “large diameter’ 

column to record 

stump diameter. 

Wildlife Use 

O=No 

1 =Yes 

O=No excavations 

1 .O” or larger in 

diameter 

1 =Woodpecker 

foraging 

&w-d) 

P=Woodpecker 

Foraging 

(heartwood) 

3-Bear foraging 

&Bear den 

5=Squirrel cache 

6-Other 

54 
Appendix C

Methods for Log Inventories

Line-transect method --The line-transect method is

especially well adapted to sampling large areas or stands

with varying topography and plant communities. For sample

areas up to 30 acres, 18 plots each containing three 75footlong transects (fig. 64A) will characterize log density within

about 20 percent of the mean density of logs per acre. Such

an array would contain a total of 4,500 linear feet of transect

(three 75-foot transects by 18 plots). Transects totalling

4,500 to 6,000 linear feet can be used to characterize a 30-

acre stand (Ottmar 1996). Larger areas might use proportionately longer totals for linear feet of transect.

Depending on the number of plots chosen, they may be

placed at 66- to 198-foot intervals (1 to 3 chains) or more

along a course in the sample area. The azimuths of the lines

composing the course are chosen to ensure that plot centers

fall at least one and one-half tree lengths within the margins

of the stand. At each plot center, three radiating transects,

120o apart, are established. For each plot, the azimuth of the

first transect is selected from a random-number table or

wristwatch (multiply seconds by 6 to get azimuth of first

transect). Each succeeding transect is 120o

 from the preceding one. The 75-foot transects are measured and marked by

with a measuring tape. Crossing of transects from adjacent

plots can be minimized by increasing the spacing between

plot centers to more than 112 feet (2 chains).

An alternative method for laying out transects for log

inventories is described in the Forest Service manual for

Current Vegetation Survey (CVS). The layout for CVS

incorporates five 51. l-foot radii of subplots within the

sample unit design (U.S. Department of Agriculture 1997).

All logs with a large-end diameter of 6 or more inches are

tallied, without regard to what portion of the log is intercepted by the transect. A break-point diameter greater than

the above 6-inch limit may be chosen depending on sizes of

logs present, or specific purpose of the log inventory. This

streamlines the sampling but will yield less information

Number of logs per acre may be calculated by substituting total transect length and log lengths in equation 1

adapted from De Vries (1973) and Pickford and Hazard

(1978), and applying constants to obtain pieces per acre

where lengths of transects and logs are in feet:

N = ((43,560 x 3.1416) / (2 x L)) x (l/a1+l/a2,...+l/a3), (1)

where

N = number of logs per acre,

L = length of transect in feet, and

a = length of each log in feet.

Fixed-area plots-Circular or square plots of 1/40th-acre

are a manageable size to sample. Areas of 20 to 30 acres can

be characterized with 10 to 18 plots. Plots are established

along sampling courses as described above for line transects.

At each sample point, a random azimuth of 75-foot length is

selected as above. The sample plot is laid out at the end of

the transect. The end of the transect may be the center of a

circular plot or a corner of a square plot (fig. 64B). Each log

whose midlength falls within the boundaries of the plot is

tallied. Log parameters as described for the line-transect

method are recorded. Log density is calculated based on the

1/40th-acre plot size, that is:

Logs per acre = logs per plot x 40. (2)

With both line-transect and fixed-area plots, measures of

variance may be obtained by using densities of logs for

individual clusters of transects or plots to obtain SE’s for

mean densities over the sample area. Because larger logs

generally provide better wildlife habitat, densities of logs by

selected large-end-diameter classes and lengths may be more

meaningful than density of logs per acre alone.

relevant to wildlife habitat.

Minimum data needed for each intercepted log are large-end diameter just

beyond the butt swell, small-end diameter,

and total length of log in feet. These

measurements will permit computation of

per-acre values for number of logs, volume,

percentage of ground covered by logs, and

linear feet of logs. One method for computing log volume is to use Smalian’s formula

(Wenger 1984) and to convert to cunits

(CCFs). Other useful variables that may be

recorded for each log are shown in the log

inventory form (appendix B). Figure 64-4ampling schemes for logs using clusters of line-transects (A) or fixed plots (B).

55
Bull, Evelyn L.; Parks, Catherine G.; Torgersen, Torolf R. 1997. Trees and

logs important to wildlife in the interior Columbia River basin. Gen. Tech.

Rep. PNW-GTR-391. Portland, OR: U.S. Department of Agriculture,

Forest Service, Pacific Northwest Research Station. 55 p.

This publication provides qualitative and quantitative information on five

distinct structures: living trees with decayed parts, trees with hollow chambers,

trees with brooms, dead trees, and logs. Information is provided on the value

of these structures to wildlife, the decay or infection processes involved in the

formation of these structures, and the principles to consider for selecting the

best structures to retain.

Keywords: Broom rust, cavity nesters, decay fungi, dwarf mistletoe,

Elytroderma, forest management, habitat monitoring, hollow trees, interior

Columbia River basin, logs, old-growth forests, snags, wildlife, wood decay.

The Forest Service of the U.S. Department of

Agriculture is dedicated to the principle of multiple

use management of the Nation’s forest resources for

sustained yields of wood, water, forage, wildlife, and

recreation. Through forestry research, cooperation

with the States and private forest owners, and management of the National Forests and National Grasslands,

it strives--as directed by Congress-to provide

increasingly greater service to a growing Nation.

The United States Department of Agriculture (USDA)

prohibits discrimination in its programs on the basis of

race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status. (Not

all prohibited bases apply to all programs.) Persons

with disabilities who require alternative means of

communication of program information (Braille, large

print, audiotape, etc.) should contact the USDA Office

of Communications at (202) 720-2791 (voice), or

(800) 855-1234 (TDD).

To tile a complaint, write the Secretary of Agriculture,

U.S. Department of Agriculture, Washington, DC

20250, or call (800) 245-6340 (voice), or (800) 855-

1234 (TDD). USDA is an equal employment opportunity employer.

Pacific Northwest Research Station

333 S.W. First Avenue

P.O. Box 3890

Portland, Oregon 97208-3890

h U.S. GOVERNMENT PRINTING OFFICE: 1996491-962
U.S. Department of Agriculture

Pacific Northwest Research Station

333 S.W. First Avenue

P.O. Box 3890

Portland, OR 97208-3890

Official Business

Penalty for Private Use, $300

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