Biodiversity and 

Coarse woody Debris 

in Southern Forests 

Proceedings of the Workshop on Coarse 

Woody Debris in Southern Forests: 

Effects on Biodiversity 

Athens, GA - October 18-20,1993 

Biodiversity and Coarse Woody Debris 

in Southern Forests 

Proceedings of the Workhop on Coarse Woody Debris 

in Southern Forests: Effects on Biodiversity 

Athens, GA 

October 18-20,1993 

Editors: 

James W. McMinn, USDA Forest Service, 

Southern Research Station, Forestry Sciences Laboratory, Athens, GA, 

and D.A. Crossley, Jr., University of Georgia, Athens, GA 

Sponsored by: 

U.S. Department of Energy, Savannah River Site, 

and the USDA Forest Service, Savannah River Forest Station, 

Biodiversity Program, Aiken, SC 

Conducted by: 

USDA Forest Service, Southem Research Station, Asheville, NC, 

and University of Georgia, Institute of Ecology, Athens, GA 

Preface 

James W. McMinn and D. A. Crossley, Jr. 

Conservation of biodiversity is emerging as a major goal in 

the management of forest ecosystems. The implied 

objective is the conservation of a full complement of native 

species and communities within the forest ecosystem. 

Effective implementation of conservation measures will 

require a broader knowledge of the dimensions of 

biodiversity, the contributions of various ecosystem 

components to those dimensions, and the impact of 

management practices. 

In a workshop held in Athens, GA, October 18-20, 1993, 

we focused on an ecosystem component, coarse woody 

debris (CWD), and its impact on the biodiversity of 

organisms in southern forests. Coarse woody debris is one 

ecosystem element readily amenable to management. The 

generation of CWD, its accumulation on forest floors, and 

its distribution are functions of stand age and management 

in the South. In contrast to other regions, comparatively 

little is known about the importance of CWD in southern 

forests. Harmon and others (1986) addressed CWD 

dynamics, input, distribution, and importance for forested 

ecosystems in general and North America in particular. In 

that review the dearth of information on CWD in southern 

forests, especially southern pine forests, was evident. 

Conclusions about the impacts and of CWD based on 

experience in the pacific Northwest are unlikely to be 

appropriate for southern forests, because climate, growth 

responses, CWD production and decomposition, and 

management practices are dissimilar. 

Biodiversity is a multidimensional concept for which many 

definitions have been proposed. Concepts include some 

aspect of preservation of diversity at the species level, 

while acknowledging the need for preserving intraspecific 

genetic diversity (Faulk 1990). Wilson (1988) eloquently 

presented the need to preserve species richness, while 

documenting the worldwide decline in numbers of species. 

Ehrlich (1988) and Franklin (1988) have argued for habitat 

preservation in contrast to the individual endangered 

species approach. Solbrig (1991) introduced a hierarchical 

view of biodiversity, ranging from molecular to genetic 

components and species, to communities, to ecosystems. 

The effects of CWD on biodiversity depend upon 

harvesting variables, distribution, and dynamics. This 

proceedings addresses the current state of knowledge about 

the influences of CWD on the biodiversity of various 

groups of biota. Research priorities are identified for future 

studies that should provide a basis for the conservation of 

biodiversity when interacting with appropriate management 

techniques. 

We thank John Blake, USDA Forest Service, Savannah 

River Forest Station, for encouragement and support 

throughout the workshop process. The success of the 

workshop is due in large part to the meticulous attention 

provided by Janice Sand, Institute of Ecology, University of 

Georgia, Athens, GA. 

Literature Cited 

Ehrlich, Paul R. 1988. The loss of diversity: causes and consequences. 

In: Wilson, E.O., ed. Biodiversity. Washington, DC: National 

Academy Press: 2 1-27. 

Faulk, Donald. 1990. The theory of integrated conservation strategies 

for biological diversity. In: Mitchell, Richard S.; Sheviak, Charles J.; 

Leopold, Donald J., eds. Ecosystem management: rare species and 

significant habitats. Bulletin 47 1. Albany, NY: New York State 

Museum: 5- 10. 

Franklin, Jerry. 1988. Structural and functional diversity in temperate 

forests. In: Wilson, E.O., ed. Biodiversity. Washington, DC: National 

Academy Press: 166- 1 75. 

Harmon, M.E.; Franklin, J.F.; Swanson, F.J. [and others]. 1986. 

Ecology of coarse woody debris in temperate ecosystems. Advances in 

Ecological Research. 15: 133-302. 

Solbrig, Otto T., ed. 1991. From genes to ecosystems: research agenda 

for biodiversity. Paris: International Union of Biological Sciences. 123 p. 

Wilson, E. 0. 1988. The current state of biodiversity. In: Wilson, 

E.O., ed. Bidiversity. Washington, DC: National Academy Press: 3-20. 

Project Leader, U.S. Department of Agriculture, Forest Service, Southern 

Research Station, Forestry Sciences Laboratory, 320 Green Street, 

Athens, GA 30602-2044, and Research Professor of Ecology, Institute of 

Ecology, University of Georgia, Athens, GA 30502-2602, respectively. 
Contents 

Preface '.. James W McMinn and D.A. Crosslq, Jr. ............................................................ 111 

Accumulations of Coarse Woody Debris in Southern Forests 

James W McMinn and Richard A. Hardt ............................................................ I 

Dynamics of Coarse Woody Debris in Southern Forest Ecosystems 

DavidH.VanLear ........................................ 

Dynamics of Coarse Woody Debris-A Simulation Study for Two 

Southeastern Forest Ecosystems 

ThomasA.Wizldrop ............................................................................ 18 

Coarse Woody Debris in Forest Ecosystems: An Overview of 

Biodiversity Issues and Concepts 

C.RonaldCarrol1 ............................................................................. 25 

Coarse Woody Debris and Woody Seedling Recruitment in 

Southeastern Forests 

RebeccaR.Sharitz ................................................................... 

Diversity of Lignicolous Basidiomycetes in Coarse Woody Debris 

KarenK.Nakasone ............................................................................. 35 

Earthworms, Biodiversity, and Coarse Woody Debris in 

Forest Ekosystems of the Southeastern U.S. A. 

PaulEHendrix ................................................................................ 43 

Macroinvertebrates and their Relationship to Coarse Woody 

Debris: With Special Reference to Land Snails 

RonaldS.Caldwel1 ............................................................................ 49 

Relationship of Wood-Feeding Insects and Coarse Woody Debris I 

JamesL.Hanula .............................................................................. 55 

The Significance of Coarse Woody Debris for the Diversity 

of Soil Mites 

John h4 Johnston and D.A. Crossley, JE ............................................................ 82 

Collembolans and Coarse Woody Debris in Southern Forests: 

Effects on Biodiversity 

RichardJ.Snider .............................................................................. 88 

Importance of Coarse Woody Debris to Southern Forest 

Herpetofauna 

Matt R. Whiles and Jack W Grubaugh .............................................................. 94 
Influences of Coarse Woody Debris on Birds in Southern Forests 

J. Drew Lanham and David C. Guyntz, Jr: .......................................................... 101 

The Role of Coarse Woody Debris in the Ecology 

of Southeastern Mammals 

SusanC. beb ................................................................................ 108 

Influences of Coarse Woody Debris on Stream Habitats and 

Invertebrate Biodiversity 

J. Bruce Wallace, Jack W Grubaugh, and Matt R. Whiles ............................................... 1 19 

Large Woody Debris, Fish Habitat, and Historical Land Use 

C.AndrewDollojS" ............................................................................. 130 

Models and Management Implications 

of Coarse Woody Debris Impacts on Biodiversity 

MichaelA.Huston ............................................................................. 139 

Workshop Summary and Recommendations 

James ;/V: McMinn and D.A. Crossley, Jr: ........................................................... 144 

Accumulations of Coarse Woody Debris in Southern Forests 

James W McMinn and Richard A. Hardt 

Abstract 

Accumulations of coarse woody debris (CWD) were estimated from 

Forest Inventory and Analysis information for Georgia and South 

Carolina and from the literature covering detailed studies. Mean 

accumulations by broad ownership class and forest type for Georgia and 

South Carolina ranged from 2.2 to 10.7 mega grams per hectare (Mglha). 

Accumulations in individual studies ranged from 0.4 Mglha in mature 

pitch pine on poor sites to 91.2 Mgka in young cove hardwoods 

regenerated by clearcutting. The information presented in this review 

suggests that attempts to quantify CWD accumulations should account 

for physiography, ownership, forest type, stand age, stand origin 

(artificial vs. natural), and disturbance. 

Introduction 

In this paper are presented estimates of the accumulations 

of coarse woody debris (CWD) in southern forests from 

two perspectives. The first, a broad overview is derived 

from information in Forest Inventory and Analysis (HA) 

publications. The second is from the literature covering 

more detailed studies of CWD on a small scale. 

The Broad Perspective 

Coarse woody debris as such is not inventoried in the 

periodic surveys conducted by USDA Forest Service FIA 

(formerly known as "Forest Survey") units. However, in 

each survey, mortality is estimated for trees that are at least 

12.7 cm in diameter at breast height (d.b.h.). The mortality 

is reported as annual volume by various strata. 

Publications with compatible information for estimating 

recruitment and standing crop were limited to Georgia and 

South Carolina. Compatible volume and area information 

was available for three broad ownership classes and five 

broad forest types in those two States (Anderson and others 

1990; Brantley and others 1993; Tansey 1987; Thompson 

1989). Ownership classes were public, nonindustrial 

private forest lands (NIPF), and forest industry. Broad 

forest types (called "broad management classes" in FIA 

publications) were pine plantation, natural pine, oak-pine, 

upland hardwood, and lowland hardwood. The published 

data consisted of total volumes for all species within each 

combination of ownership class and forest type. 

Volumes were converted to mass using an overall average 

(0.525) of wood-specific gravities reported for Southern 

species (Koch 1972, 1985). Standing crop mass was 

derived using the single exponential decay model with a 

k-value of 0.075; this value was derived from loblolly pine 

data in the Piedmont of South Carolina (Barber and Van 

Lear 1984). (This was the only exponential decay model 

found in the literature for the geographic area of interest.) 

Based on the descriptions by Barber and Van Lear (1984) 

and HA personnel,' standing crop volume was assumed to 

be 15 times the annual recruitment. However, all values 

were considered low because all age classes with trees 

meeting the minimum diameter limit were included in these 

average estimates. 

Mean CWD accumulations by ownership and state ranged 

from 4.1 mega grams per hectare (Mgha) on forest 

industry land in South Carolina to 7.7 Mgha on public 

lands in South Carolina (table 1). Accumulations were 

lower on forest industry land than on public or nonindustrial 

private lands, and higher in South Carolina than in Georgia 

on public and NIPF. Lower mortality would generally be 

expected on forest industry land because the average stand 

age is lower and the proportion of pine plantations is higher. 

(The latter generally exhibit lower mortality from 

intraspecific competition because initial density is 

controlled.) This explanation is supported by the relatively 

low accumulations for pine plantations (2.3 Mgha and 3.5 

Mgha in Georgia and South Carolina, respectively) 

compared to other forest types when averaged over all 

ownerships (table 2). Natural pine and lowland hardwood 

types exhibited the highest accumulations (> 8 Mglha), 

while the oak-pine and upland hardwood types exhibited 

intermediate accumulations. 

Relative accumulations among the forest types were similar 

for the two States when averaged over all ownerships, but 

were dissimilar when broken out by ownership class. On 

Project Leader, USDA Forest Service, Southern Research Station, Athens, 

GA 30602; and Research Assistant, University of Georgia, Daniel B. 

Warnell School of Forest Resources, Athens, GA 30602, respectively. 

' Personal communication. 1993. Noel Cost, Project Leader, Southeastern 

Forest Experiment Station, P.O. Box 2680, Asheville, NC 28802. 
Table 1-Estimated mass and volume of coarse woody Table 2-Estimated mass and volume of coarse woody 

debris over all forest management classes by ownership debris over all ownerships by broad forest management 

and State class and State 

Mass Volume Mass Volume 

Annual Standing Annual Standing Annual Standing Annual Standing 

Ownership input crop input crop Forest type input crop input crop 

Public 

NIPF* 

Forest 

industry 

Public 

NIPF* 

Forest 

industry 

Georgia 

0.410 5.667 0.781 11.715 

0.478 6.607 0.91 1 13.665 

0.327 4.520 0.622 9.330 

South Carolina 

0.555 7.672 1.057 15.855 

0.551 7.616 1.050 15.750 

0.300 4.147 0.570 8.550 

"Nonindustrial private forest land. 

public lands in Georgia, the upland hardwood type 

exhibited the lowest accumulations at 2.2 Mglha; pine 

plantation and oak-pine accumulations were somewhat 

higher; and natural pine and lowland hardwood 

accumulations were quite high (> 9 Mglha). In South 

Carolina, only the pine plantation type exhibited low 

accumulations while all other forest types had relatively 

high accumulations; lowland hardwood exhibited the 

highest accumulation at 10.7 Mglha (table 3). All data 

were collected prior to Hurricane Hugo. Patterns among 

types were more similar for the two States on NIPF, except 

for pine plantations in South Carolina where 5.7 Mgfha 

accumulations were unusually high for the forest type 

(table 4). On forest industry lands, the relative pattern 

among types was generally similar for the two States; 

however, higher accumulations in the natural pine, oakpine, and upland hardwood types were exhibited in 

Georgia than in South Carolina (table 5). 

Several parallels can be found between these values and 

those in a more rigorous study designed to estimate snag 

Pine 

plantation 

Natural pine 

Oak-pine 

Upland 

hardwood 

Lowland 

hardwood 

Pine 

plantation 

Natural pine 

Oak-pine 

Upland 

hardwood 

Lowland 

hardwood 

Georgia 

South Carolina 

densities from FIA data in FTorida (McComb and others 

1986). In that study, snags (12.7-cm d.b.h. and 1.3-m tall) 

were more abundant (1) in oak-hickory and oak-tupelobaldcypress than in longleaf or slash pine; (2) in natural 

stands than in pine plantations; (3) on public than on 

private lands; and (4) on stream margins and in deep 

swamps than on flatwoods, rolling uplands, and sandhills. 

Detailed Studies 

The more detailed studies define the CWD accumulations 

expected under different conditions at various stages of 

stand development. Accumulations of GWD-snags and 

logs-are quantified in the scientific literature by mass, 

volume, or the number of pieces per unit area. Commonly, 

accumulations have been reported by mass (Mgha) or 

volume (m31ha), and snags have been reported by number 

(no ./ha). 
Table 3-Estimated mass and volume of coarse woody 

debris on public land by broad forest management class and 

State 

Mass Volume 

Annual Standing Annual Standing 

Forest type input crop input crop 

Table &Estimated mass and volume of coarse woody 

debris on nonindustrial private land by broad forest type 

and State 

Mass Volume 

Annual Standing Annual Standing 

Forest type input crop input crop 

Pine 

plantation 

Natural pine 

Oak-pine 

Upland 

hardwood 

Lowland 

hardwood 

Pine 

plantation 

Natural pine 

Oak-pine 

Upland 

hardwood 

Lowland 

hardwood 

---- Mgha - - - - - - rn3ha - - - 

Georgia 

0.275 3.801 0.524 7.860 

0.670 9.261 1.275 19.125 

0.263 3.635 0.502 7.530 

0.160 2.212 0.306 4.590 

0.665 9.192 1.267 19.005 

South Carolina 

0.177 2.447 0.337 5.055 

0.617 8.529 1.176 17.640 

0.629 8.695 1.197 17.955 

0.575 7.948 1.096 16.440 

0.773 10.685 1.057 15.855 

Pine 

plantation 

Natural pine 

Oak-pine 

Upland 

hard wood 

Lowland 

hardwood 

Pine 

plantation 

Natural pine 

Oak-pine 

Upland 

hardwood 

Lowland 

hardwood 

---- Mg/ha - - - - - - rn3/ha - - - 

Georgia 

0.162 2.239 0.309 4.635 

0.648 8.957 1.234 18.510 

0.372 5.142 0.708 10.620 

0.413 5.709 0.787 11.805 

0.646 8.930 1.231 18.465 

South Carolina 

0.412 5.695 0.784 11.760 

0.647 8.943 1.232 18.480 

0.464 6.414 0.884 13.260 

0.448 6.193 0.854 12.810 

0.656 9.068 1.250 18.750 

Harmon and others (1986) and Spies and others (1988) 

have postulated a U-shaped temporal pattern for logs 

following disturbance. High log inputs produced by 

disturbances, such as logging, fire, or insect attack, may 

result in a large accumulation in the subsequent young 

stand (Harmon 1980; Mattson and others 1987; Nicholas 

and White 1984; Smith 199 1). This accumulation largely 

decays before inputs return to predisturbance levels, 

resulting in low densities of logs in maturing secondgrowth. Log accumulations slowly build with increasing 

inputs, eventually reaching moderate to high levels in oldgrowth stands (Harmon and others 1986; Hardt 1993; 

Muller and Liu 1991). However, log accumulations in 

young stands, dependent on the type of disturbance and 

stand history, are highly variable (Hardt 1993; Harmon and 

others 1986; Spies and others 1988). For example, shortrotation harvesting can result in low accumulations of 

CWD after several rotations (Gore and Patterson 1985; Spies 

and Cline 1988; Spies and others 1988). 

Accumulations of logs in southern forests vary widely with 

forest type, stand age, and disturbance history (table 6). 

The greatest accumulations of logs (> 90 Mgha) are 

reported from stands immediately following disturbance 

(Mattson and others 1987; Smith 1991). The smallest 

accumulations of logs (as low as 0.4 Mglha) have been 

reported from maturing stands on low productivity sites 

(Harmon and others 1986; Smith 199 1). Log masses 

reported for old-growth stands in the Southern 

Appalachians are generally higher than for younger stands, 

ranging from 17 Mgha for a beech stand in Kentucky 

(Muller and Liu 1991) to 29 Mgha for a beech-birch stand 

in Tennessee (Harmon and others 1986). These 
Table 5-Estimated mass and volume of coarse woody 

debris on forest industry land by broad forest management 

class and State 

Mass Vblume 

Annual Standing Annual Standing 

Forest type input crop input crop 

Pine 

plantation 

Natural pine 

Oak-pine 

Upland 

hardwood 

Lowland 

hardwood 

Pine 

plantation 

Natural pine 

Oak- pine 

Upland 

hardwood 

Low land 

hardwood 

---- Mgha - - - - - - rn3/ha - - - 

Georgia 

South Carolina 

accumulations are comparable to masses reported from 

other Eastern old-growth stands (Gore 1986; Lang and 

Forman 1978; MacMillan 198 1 ; Tyrrell 199 l), but are an 

order of magnitude lower than log masses reported for the 

Douglas-fir region of the Pacific Northwest (Harmon and 

others 1986). In a review of log accumulations in 

temperate deciduous old-growth forests, Muller and Liu 

(1991) found higher accumulations in cool forests and 

speculated that higher accumulations resulted from slower 

decomposition rates. In contrast, Mattson and others 

(1 987) found no significant relationship between elevation 

and log decay; however, the range in elevation may have 

been too small to substantially influence temperature. 

Snag accumulations are presented in table 7. Snags are 

commonly reported by the number per unit area, in part 

because most snag studies are primarily related to animal 

habitat (Conner 1978; Harlow and Guynn 1983; McComb 

and Muller 1983; McComb and others 1986). 

Accumulations of snags may also follow the same Ushaped temporal pattern as logs where extremely high 

accumulations follow types of disturbance. However, the 

episodic nature of snag production may confound patterns 

of snag accumulations that are associated with forest type 

or stand condition. The effects of natural disturbances on 

snag production are highly variable. For example, insects 

and diseases that kill trees aboveground, such as southern 

pine beetle, balsam woolly adelgid, Dutch elm disease, and 

chestnut blight, produce high accumulations of snags 

(Harmon and others 1986; Smith 199 1). On the other hand, 

diseases that attack trees at the base or belowground, such 

as root and heart rots, are more likely to create logs directly 

when weakened trees are windthrown (Harmon and others 

1986; Matlack and others 1993). 

Timber harvests generally leave stands with few snags 

(Carmichael and Guynn 1983; Dickson and others 1983; 

McComb and others 1986), but timber stand improvement 

that includes girdling may increase snag accumulations 

(Moriarty and McComb 1983). Regenerating stands may 

have high accumulations of small snags, a result of densitydependent tree mortality, but as the stands become older the 

accumulation of larger snags increases. Total snag 

densities may not differ between second-growth and oldgrowth stands, but the size distribution will shift. McCornb 

and Muller (1983) reported no significant difference 

between the densities of snags in Appalachian old-growth 

and second-growth stands. However, in a survey of snag 

densities in the pine, pine-hardwood, and hardwood stands 

in Florida, McComb and others (1986) found that the 

density of snags (> 12.7-cm d.b.h.) increased as stand age 

increased. In the Southern Appalachians, Rosenberg and 

others (1988) found a greater density, basal area, and mean 

diameter of snags in old stands than in younger stands. 

Hardt (1993), also working in the Southern Appalachians, 

found significantly higher densities of large snags (>25-cm 

d.b.h.) in old-growth than in second-growth stands. 

Conclusions 

Accumulations of CWD in individual stands are quite 

variable and, in this review, range from 0.4 Mgha in 

mature pitch pine on poor sites to 91.2 Mgha in young 

cove hardwoods regenerated by clearcutting. However, the 

influence of some factors associated with ownership and 

forest type in Georgia and South Carolina is so strong that 

relatively large differences (2.2 to 10.7 Mgha) exist in 

mean accumulations. Generally, the information derived 
Table &Log accumulations in some southern forest stands 

Lower 

diameter Log Log 

Stand Age limit mass volume Source 

Years 

Cove hardwoods, mixed oak, 

oak-pine; North Carolina 0" 

1" 

2" 

9 1.2 - Mattson and others 1987 

74.8 - 

53.1 - 

Onega and Eickmeier 199 1 

Harmon 1980, as cited in 

Harmon and others 1986 

Harmon and others 1986 

Harmon and others 1986 

Harmon 1980, as cited in 

Harmon and others 1986 

Smith 1991 

Sugar maple; Tennessee 

Chestnut oak; Tennessee 

Tulip-poplar; Tennessee 

Pine; Tennessee 

Pitch pine; North Carolina 

Mixed oak; North Carolina Petranka and others 

(unpublished manuscript)" 

Tulip-poplar; North 

Carolina - 22.40 Hardt 1993 

- 9 1.55 

Cove hardwoods, mixed 

oak; North Carolina - 45 .OO Hardt 1993 

- 83.32 

White pine-white oak; 

South Carolina 

Sugar Maple; North Carolina 

Beech-birch; Tennessee 

Mixed-oak; Tennessee 

Chestnut oak; Tennessee 

Beech; Kentucky 

Sugar maple; Kentucky 

Chestnut oak-red maple; 

Kentucky 

- 65.64 Hardt 1993 

- 86.17 Hardt 1993 

29 82 Harmon and others 1986 

24 94 Harmon and others 1986 

2 1 132 Harmon and others 1986 

17.0 54.8 Muller and Liu 199 1 

27.1 63.8 Muller and Liu 199 1 

27.1 78.9 Muller and Liu 199 1 

a Following clearcut harvest. 

Following southern pine beetle attack. 

Petranka, J.W. (and others). Effects of timber harvesting on low elevation populations of Southern Appalachian 

salamanders (unpublished manuscript). 
Table 7-Snag accumulations in some southern forest stands 

Lower 

d.b.h. Snag Snag Snag 

Stand Age limit density mass volume Source 

Years No.ha Mgha 

Pine; Florida McComb and others 1986 

Pine-hardwood; 

Florida McComb and others 1986 

Hardwood; Florida McComb and others 1986 

Bottomland hardwoods; 

South Carolina 

Longleaf-loblolly pine; 

South Carolina 

Harlow and Guynn 1983 

Harlow and Guynn 1983 

Pine plantation; 

South Carolina 1 -40+ 

Pine-hardwoods; 

South Carolina 20+ 

Cove hardwoods; 

South Carolina 40+ 

Upland hardwoods; 

South Carolina 40+ 

Bottomland hardwoods; 

Louisiana 45 

80 

Pine-hardwoods; 

Mississippi 85 

Carrnichael and Guynn 1983 

Carmichael and Guynn 1983 

Carrnichael and Guynn 1983 

Carmichael and Guynn 1983 

McComb 1979, as cited in 

McComb and others 1986 

McComb 1979, as cited in 

McComb and others 1986 

Mixed mesophytic; 

Kentucky 60 

60" 

Pitch pine; 

North Carolina - 100 

3b 

8 

1 lb 

1 6b 

Moriaty and McComb 1983 

Smith 1991 

continued 
Table 7-Snag accumulations in some southem forest stands (continued) 

Lower 

dbh Snag Snag Snag 

Stand Age limit density mass volume Source 

Years 

Sugar maple; 

Tennessee 

Chestnut oak, 

Oak Hickory; 

Virginia 

1.92 - Onega and Eickmeier 199 1 

- - Rosenberg and others 

1988 - - 

Mixed mesophytic; 

Kentucky - - McComb and Muller 1983 

- - 

Mixed mesophytic; 

Kentucky 

Tulip-poplar; North 

Carolina 

5.2 12.0 Muller and Liu 199 1 

- - Hardt 1993 

- - 

Cove hardwoods, 

mixed oak; 

North Carolina - - Hardt 1993 

- - 

White pine-white oak; 

South Carolina 

Sugar maple; 

North Carolina 

- - Hardt 1993 

- - Hardt 1993 

a Following timber stand improvement. 

Following southern pine beetle attack. 

" Snags greater than 10-em d.b.h. 
from inventory data and more detailed research suggests 

that future studies of GWD accumulations should take into 

account physiography, ownership, forest type, stand age, 

stand origin (artificial vs. natural), and disturbance. 

Acknowledgment 

This work was supported in part by the Savannah River 

Operations Office, U.S. Department of Energy, through a 

cooperative arrangement with the USDA Forest Service, 

Southern Region, Savannah River Forest Station. 

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woody debris in a regenerating, clearcut forest in the Southern 

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McComb, W.C.; Muiler, R.N. 1983. Snag densities in old-growth and 

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[and others]. 1986. Snag resources in Florida-are they sufficient for 

average populations of primary cavity-nesters? Wildlife Society 

Bulletin. 14:40-48. 

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dissertation. 
Dynamics of Coarse Woody Debris 

in Southern Forest Ecosystems 

David ICE. Van Lear 

Abstract 

Coarse woody debris (GWD)-standing dead trees, fallen trees, and 

decomposing large roots-serves a number of ecological functions. 

CWD loadings are dynamic in response to inputs from tree breakage and 

mortality and to losses from decomposition and fire. Two very different 

natural processes, gap-phase dynamics and major episodic disturbances, 

contribute to inputs, as well as forest management activities. Decay and 

combustion, if complete, yield both CO, and H,O. However, neither is 

usually complete, and the combustion process leaves some rapidly altered 

CWD, whereas decay results in the gradual formation of humic 

substances. Current forest management practices often contribute to low 

loadings of CWD in southern forests. Although some data provide the 

basis for very general estimates, there is a paucity of knowledge in the 

South on almost every aspect of CWD dynamics and loading. 

a measured size-class of forest fuels in a number of cited 

studies in the South. For obvious reasons, the dynamics of 

root biomass of dead trees has received little study. 

The objectives of this paper are to describe the processes 

that affect loadings of CWD within the terrestrial 

ecosystems of southern forests and to identify gaps in our 

knowledge of CWD dynamics. Because of the paucity of 

information on loadings and dynamics of dead roots, that 

topic will not be discussed. Suffice it to say that the below 

ground dynamics of large dead roots represents a major gap 

in our knowledge of CWD. 

Introduction 

Organic material in the form of standing dead trees (snags), 

fallen trees, and decomposing large roots, all of which are 

components of coarse woody debris (CWD), influences the 

ecology of a site for decades or even centuries (Franklin 

and Waring 1980). CWD functions as seed germination 

sites, as reservoirs of moisture during droughts, as sites of 

nutrient exchange for plant uptake, and as critical habitat 

for forest organisms. During later stages of decomposition, 

it promotes favorable soil structure (Harmon 1982; Harmon 

and others 1986; Maser and others 1988). Dead root 

systems have been neglected as a component of CWD. 

However, decomposing roots contribute to the 

heterogeneity of the soil, provide increased infiltration and 

percolation of soil water, enhance gas diffusion throughout 

the rooting zone, and provide habitat for soil-dwelling 

organisms (Lutz and Chandler 1955). 

Loadings of GWD are dynamic, i,e,, constantly changing in 

response to inputs from tree breakage and morlality and to 

losses from decomposition and fire. This dynamic nature is 

reflected in gradual or episodic changes in mass, density, 

and volume of standing dead and fallen trees. 

The term "coarse woody debris," as used in this paper, 

refers to any dead standing or fallen tree stem (or dead 

root) at least '7.6 cm in diameter. This minimum dimeter 

was arbitrarily chosen, primarily because it corresponded to 

Inputs of Coarse Woody Debris 

The flow of aboveground CWD within terrestrial 

ecosystems is summarized in diagrammatic form (fig. l), as 

adapted from Harmon and others (1986). Within terrestrial 

ecosystems, mortality and breakage of living trees add 

CWD, while decay and fire remove or transform CWD 

(Harmon and others 1986; Maser and others 1988). The 

balance between inputs and losses of CWD within the 

forest ecosystem represents the standing crop, or loading, 

of CWD. 

Inputs of CWD occur when living trees are killed by fire, 

wind, lightning, insects, disease, ice storms, competition, or 

humans. Disturbances may kill scattered individual trees, 

DECAY 

FIRE 

Bowen Professor, Department of Forest Resources, Clemson University, Figure 1-Flow diagram of the dynamics of CWD in terrestrial 

Clemson, SC 29643- 1003. ecosystems. 
groups of trees, entire stands, or even entire landscapes and 

are now widely recognized as a natural part of the ecology 

of the southern forest (Christensen 1991; Sharitz and others 

1992; Skeen and others 1993). Major disturbances 

contribute large quantities of CWD, which are added to 

predisturbance CWD already accumulated in the stand, For 

this reason, loadings of CWD are often highest soon after 

major forest disturbances. 

Gradual Inputs of Coarse Woody Debris 

by Gap-Phase Dynamics 

CWD inputs in southern forests from gradual gap-phase 

dynamics, i.e., from the occasional death of individual trees 

or groups of trees within the forest, are not well 

documented. Large canopy gaps can contribute substantial 

quantities of CWD. For example, Smith (1991) estimated 

that canopy gaps created in pitch pine stands by pine 

beetles in the Southern Appalachians contained 35.6 tons 

per hectare (ha) of CWD. Loadings from insect damage in 

more productive forest types could be much higher. 

Some information on snag densities (numberslarea) and 

recruitment rates is available from the wildlife literature. 

Generalizations from published research include the 

following: 

(I) Snags are most common in hardwood stands and least 

common in pure pine stands (Harlow and Guynn 1983; 

McComb and others 1986b; Sabin 199 1). (2) Snags are 

more frequent in lowlands and riparian zones than on 

upland sites. (3) Unmanaged private land and national 

forests generally have higher densities of snags than lands 

manage,d intensively for wood production (McComb and 

others 1986a, 1986b). 

The length of time that snags remain standing varies with 

species and size, although most snags fall within a decade 

or less in southern forests (Dickenson and others 1983; 

McComb and Rumsey 1983; Sabin 1991). However, 

occasional American chestnut snags are still standing in 

Southern Appalachian forests 70 years after the chestnut 

blight. White pine and white oaks are generally longer 

standing than snags of other pine and oak species 

(Hassinger and Payne 1988). Large diameter snags stand 

longer than smaller ones (Bull 1983; Raphael and Momson 

1987). 

Snag densities in the relatively young forests of the South 

vary widely. fn the Appalxhian deciduous forest, Cmey 

(1 983) found snag densities ranging from 11 to 55 snags 

per ha, Sabin (1991) reported an overall snag density of 

28.1 snags per ha in relatively young (20 to 60+ yrs) forest 

types in the Piedmont and noted that snags were being lost 

at an average rate of 0.52 snags per ha per year. Relatively 

few areas and little acreage in the Southeast support overmature or old-growth forests where snag recruitment rates 

and densities are unknown. Such infomation is needed to 

serve as baseline data against which forests managed more 

intensively could be compared. 

Heavy Loading of Coarse Woody Debris 

by Major Episodic Disturbances 

In contrast to gap-phase disturbances, where natural 

succession proceeds at a relatively gradual rate, large-scale 

natural disturbances, such as catastrophic wildfires and 

hurricanes, are episodic in nature and may kill trees over 

large forest areas. As a result of these natural disturbances 

and timber harvesting, few forest ecosystems in the 

Southeastern United States succeed to a vegetative climax 

condition or even develop undisturbed for as long as a 

century. 

Forest fires affect the loading of CWD in two ways. They 

simultaneously add CWD by killing live trees and reduce 

CWD by consuming dead trees. Fire regimes in the South 

range from those where fire reoccurs infrequently (on the 

order of several decades to perhaps a century or more) and 

fuel loading is heavy, to those where fire occurs almost 

annually and fuels are light. Sand pine and table mountain 

pine regenerate after catastrophic stand-replacement fires, 

which function to open serotinous cones, kill hardwood 

understory competition, and prepare seedbeds (DellaBianca 1990; Outcalt and Balmer 19831, as well as 

contribute a large pulse of CWD. At the other extreme, in 

open longleaf pine-wiregrass stands, a regime of frequent 

fire would prevent the buildup of fuels to levels where high 

rates of fire-induced tree mortality would be expected. 

Boyer (1979) reported an annual mortality of only one tree 

per ha in mature longleaf pine stands throughout the 

longleaf region. 

Stand-replacement fires, which kill all aboveground 

biomass, obviously make heavy contributions to CWD. 

The author knows of no studies in the South where CWD 

inputs have been estimated following stand-replacement 

fires. However, estimates of aboveground living biomass 

are available for some forest types and site conditions and, 

when corrected for small branch and foliage components, 

provide a rough approximation of potential CWD inputs. 
About 70 to 80 percent of the aboveground biomass of 

these forest types is above the minimum size class of CWD. 

For loblolly pine, the most studied of the southern pines, 

aboveground biomass ranges from about 100 tons per 

hectare (tlha) in thinned 41 -year-old plantations on poor 

sites (Van Lear and others 1983) to approximately 156 tlha 

for unthinned 16-year-old plantations on good sites (Wells 

and Jorgensen 1975). Biomass of older pine stands on 

good to excellent sites would be even higher. Aboveground 

biomass of mixed hardwood stands averaged 178 and 175 

tlha at Coweeta Hydrologic Laboratory and Oak Ridge 

National Laboratory, respectively (Mann and others 1988), 

similar to the 164 tlha estimate from forest survey data for 

fully stocked stands of mature hardwoods in the Southeast 

(Phillips and Sheffield 1984). 

Hurricanes, tornadoes, and other strong winds are common 

in the Southeastern United States and strongly influence 

CWD dynamics. These strong winds create in a matter of 

hours loadings of CWD that would never be achieved 

during centuries of gap-phase natural succession (Hook and 

others 199 1). For example, Myers and others (1993) 

measured loadings, after limited salvage, of almost 90 t/ha 

of downed woody material and 16 t/ha of snags in mature, 

uneven-aged pine stands 2 years after Hurricane Hugo. 

Strong winds either snap stems of well-anchored species or 

uproot shallow-rooted species. Although catastrophic 

winds (probably category V-force winds) will destroy any 

stand, such winds normally occur over only a relatively 

small portion of the area affected by most hurricanes. 

Forest damage from hurricanes and tornados has increased 

in recent decades due to the regrowth of mature forests 

following the extensive harvest of old-growth forests that 

occurred between 1 885- 1 930 (Hooper and McAdie 1993). 

In addition to stand age, site (Crocker 1958; Foster 1988), 

community type (Duever and McCollum 1993; Sharitz and 

others 1993), species (Gresham and others 1991 ; Hook and 

others 1991; Sharitz and others 1993; Touliatos and Roth 

197 l), and tree morphology (Gratkowski 1956; Nix and 

Ruckelshaus 1991) markedly influence the damage (and 

CWD loadings) to forests by strong winds. 

Other environmental factors, e.g., insect and disease 

outbreaks, ice storms, and mass movement of soils, can 

dramatically increase loadings of CWD. Some native 

insects, the southern pine beetle, for example, periodically 

reach epidemic proportions and kill whole stands of various 

pine species across large portions of the landscape. 

Introduced insects like the gypsy moth continue to expand 

their range southward and devastate hardwood stands over 

extensive areas. Certain diseases, for example, fusiform 

rust, have become more prevalent in recent decades. Ice 

stoms periodically wreak havoc on forests in some 

portions of the South, e.g., in the Sandhills region. 

The quantity of CWD contributed to sites by all these 

factors is a function of the proportion of the stand killed 

(and consumed, in the case of fire) by these agents and the 

proportion of the trees above the minimum CWD size class. 

Contributions range from the mortality of scattered 

individual trees killed in nonepisodic events to the mass 

deaths of trees on thousands of hectares from major 

episodic events, during which the loading of CWD across 

the landscape is increased dramatically. Information on 

CWD inputs from all types of catastrophic events is needed 

to fully evaluate the environmental effects of these 

disturbances. 

Losses of Coarse Woody Debris 

Within terrestrial ecosystems, CWD is lost through decay 

and fire. Decay and combustion by fire are similar 

processes in some respects, but also have important 

differences. The relative importance of each process varies 

by site-decay dominates on mesic sites, while fire is more 

important on xeric sites (unless fire-suppression efforts are 

effective). Although its natural role as a major ecological 

factor has often been overlooked by ecologists and land 

managers, fire has been a dominant factor shaping the 

structure and composition of southern forest ecosystems for 

millennia. 

Decay 

Decay of CWD is initiated by an invasion of white, brown, 

and soft rot fungi, causing a loss of density (Kaarik 1974). 

Insects are known to be important inoculators of these 

decay microbes (Abbott and Crossley 1982). Toole (1965) 

described the deterioration of unlopped hardwood logging 

slash in Mississippi and found that, for most of the species 

studied, small branches had disintegrated after 6 years and 

only a small portion (< 15 percent) of the large branches 

and bole had not settled on the ground. Twigs and small 

branches decayed most readily, followed by the larger 

sapwood and finally the heartwood. Decay may be 

retarded when the bark sloughs off early, allowing the 

surface of the sapwood to dry quickly and become 

casehardened. Smith (1991) documented changes in 

decomposer communities of pitch pine CWD during 

decomposition. During early stages of decomposition, bark 

beetles and blue-stain fungi dominated, although neither 

had much effect on decomposition, i.e., wood density was 
not markedly reduced. White rots, brown rots, ants, and 

termites dominated later stages of decomposition. As the 

wood stnrcture is broken down, fragmentation becomes a 

major mechanism of decay. 

Fragmentation of CWD refers to a reduction of volume via 

physical and biological forces during the decay process 

(Harmon and others 1986; Maser and others 1988). 

Fragmentation is normally preceded by a lag period during 

which both density and mass of fresh CWD decrease but 

volume remains constant. Snags fragment when portions 

of the standing-dead tree or the entire tree break and fall to 

the ground. Biological fragmentation of snags and fallen 

logs is caused by both plants and animals. Invertebrates 

use the dead wood as a food source, creating galleries that 

serve as avenues for microbial colonization and further 

decay. Bears, birds, and other animals shred the rotting 

wood while foraging for insects. Plant roots grow into 

fallen trees after initial stages of decay have been 

completed and further fragment the partially decomposed 

materials. During the entire decay process, the physical 

forces of water and gravity relentlessly transport 

fragmented materials from snags and fallen logs to the 

forest floor, where they undergo further decomposition and 

are ultimately converted to CO, or decay-resistant humus. 

The final products of decay of CWD are fine woody debris, 

humus, and CO, (Harmon and others 1986; Maser and 

others 1979; Spies and Cline 1988). 

Although perhaps not as good an index of decay as volume 

diminution, changes in wood density have frequently been 

used to measure initial stages of physical decay. Following 

clearcutting of a mixed hardwood stand in the Southern 

Appalachians of North Carolina, wood-density decay 

coefficients varied widely, ranging from 0.18 per year for 

species such as dogwood and persimmon, to 0.03 per year 

for decay-resistant species like black locust and American 

chestnut (Mattson and others 1987). Little information is 

available regarding decay of pine CWD in the South. 

Barber and Van Lear (1984) calculated a wood-density 

decay coefficient of 0.075 per year for large loblolly pine 

slash (excluding bark) following clearcutting in the South 

Carolina Piedmont, while Smith (1991) found a decay 

constant of 0.048 per year for pitch-pine CWD in the 

Southern Appalachians. 

In addition to species differences, other factors affect the 

rate of decay of CWD (Barber and Van Lear 1984; Mattson 

and others 1987). Aspect of the site is important4WD 

decays faster on north and northeastern aspects, probably 

due to the generally greater availability of soil moisture. 

Relative position of the fallen tree affects decay ratesCWD in contact with the ground decays faster than aerially 

suspended CWD. Large woody debris decays slower than 

small woody debris. In streams, saturated CWD decays at 

extremely slow rates. Decomposition rates in the Southeast 

are generally higher than those reported for other regions, 

presumably because temperature and moisture conditions 

are more favorable for microbes and invertebrates involved 

in the decay process. 

The chemical nature of CWD changes during 

decomposition. Workers in the Pacific Northwest (Graham 

and Cromack 1982; Sollins and others 1980) and elsewhere 

have noted that the C/N ratio of CWD decreases, and the 

concentration of lignin increases as decay progresses. 

Concentrations of nitrogen and phosphorus increase in 

large logging slash following harvest of loblolly pine 

(Barber and Van Lear 1984) and in pitch pine CWD 

following pine beetle attack (Smith 1991). However, after 

initially being a sink for nutrients, CWD later becomes a 

source when fragmentation dominates the decay process. 

Long-term studies are underway that will better document 

decay rates of CWD. However, more information is 

needed concerning decay rates of different species under 

different site conditions and management regimes. What is 

the best method for measuring decay? Sampling wood 

density in various states of decay is frequently used, but the 

method becomes biased during mid to late stages of decay 

when only the most resistant pieces of wood remain. 

Adjustment of decay chronosequences for past 

fragmentation is necessary, but often difficult, if mass 

losses are to be estimated correctly (Harmon, personal 

communication'). When does decaying wood become a 

source, rather than a sink, for nutrients? What types of 

decay models best describe the decay process? These and 

many other questions reflect gaps in our knowledge of the 

decay process. 

Fire 

Fire and decay are similar processes in that both, if 

completed, are essentially oxidation reactions yielding as 

final products CO, and H,O (Brown and Davis 1973). 

However, fire is the rapid oxidation, or combustion, of 

fuels, while decay is a much more gradual oxidation of 

organic materials. In neither process is oxidation generally 

complete. In forest fires, complete combustion is obviously 

uncommon, as evidenced by dead snags and downed trees 

on burned sites. Decay is also generally incomplete, as 

'Personal communication. 1993. Mark Harmon, Professor, Department 

of Forest Science, Oregon State University. 
evidenced by the presence of residual CWD and the 

fomation of humus. 

Some of the effects of fire on CWD are similar to those of 

decay, i.e., fire fragments large pieces of wood and bark 

into smaller pieces and releases CO, and other gases into 

the atmosphere, However, the two processes obviously 

differ in reaction time and in the type of substrate produced 

(charred vs. uncharred). Also important is the fact that the 

decay process generally tends to mesify microsites because 

of incorporation of humified products into the soil, while 

fire tends to xerify microsites, at least in the short run, by 

oxidizing humus from the forest floor and exposing the soil 

surface to greater insolation. 

Many deficiencies exist in our knowledge of the role of fire 

in CWD losses. What is the effect of charring on decay? 

Under what conditions can fire be used to minimize CWD 

loss? Is fire compatible with management for snags? What 

burning regimes are appropriate to achieve and maintain 

desired loadings of CWD? This last deficiency assumes 

that we eventually will have some concept of what desired 

loadings are. Southern forests evolved in regimes of more 

or less frequent fire. A major gap in our understanding of 

CWD dynamics is the way this major environmental factor 

influenced CWD loadings on a landscape scale. 

Loadings of Coarse Woody Debris 

in Southern Forest Ecosystems 

Loadings of CWD at a given time reflect the balance 

between inputs and losses. Although general temporal 

patterns of loading may be apparent on some sites, e.g., 

gradually increasing CWD loadings on mesic sites as oldgrowth conditions are approached, within these general 

patterns are fluctuations of varying magnitude. On xeric 

sites, temporal patterns may be even more difficult to 

identify due to the chance occurrence of fire. 

In the absence of major disturbances, natural succession in 

forests may be dominated for extended periods by gapphase dynamics, during which CWD accumulates slowly. 

During the development of a new stand following a major 

disturbance, much of the predisturbance and disturbancecontributed debris decays. Loadings of CWD would be 

expected to decline during the early development and 

midsuccessional periods because young trees dying from 

competition are too small to contribute significantly to 

CWD and because mortality rates during the 

midsuccessional stage are low. As succession proceeds, 

mortality of scattered senescent trees occurs and CWD 

loadings would be expected to increase. In the later stages 

of succession and old growth, increased mortality of large 

overstory trees would add to the loading of CWD, 

especially if these stages were dominated by large, longlived individuals. 

This hypothetical pattern of CWD loading over time has 

received little study in terrestrial forest ecosystems in the 

South. However, Hedman (1992) has documented this Ushaped pattern in a 300-year sere in small streams in the 

Southern Appalachians (fig. 2). A similar scenario has 

been well documented for Douglas-fir ecosystems in the 

Pacific Northwest after catastrophic fires (Spies and others 

1988). Muller and Liu (1991) found that the volume and 

mass of CWD in an old-growth deciduous forest on the 

Cumberland Plateau averaged 66.3 m3 per ha and 2 1 t ha, 

respectively. Their work suggested that loadings of CWD 

in old-growth forests in warmer regions are lower than 

those in cooler regions. 

There is relatively little data in the South concerning 

loadings of CWD following major episodic disturbances or 

through various stages of succession. Studies are needed to 

more thoroughly characterize loadings of CWD in oldgrowth forests. How do loadings vary in response to 

different fire regimes? Are CWD loadings low for some 

forest types because of rapid decay rates, or because fire is 

a frequent visitor? How can management be modified to 

enhance CWD loadings on both stand and landscape 

scales? These types of questions must be answered so that 

Early Mid Late Ofd-groVah 

Seral Stage 

Figure 2--Coarse woody debris loadings, excluding American chestnut, 

in small Southern Appalachian streams. 
managers will have guidelines relative to loadings of CWD 

in managed stands versus those in stands that have not been 

manipulated. As research fuder demonstrates the 

ecological significance of CWD in southern forests, current 

management strategies may need to be altered to achieve 

certain levels of CWD. 

Effects of Management 

The effects of management on CWD have received little 

direct study in the Southeast. However, a number of studies 

have indirectly dealt with CWD, especially relative to site 

preparation techniques. Morris and others (1983) found 

that 14.1 t/ha of coarse woody logging slash were displaced 

into windrows during mechanical site preparation of a 

flatwoods site in norida. While this windrowed material is 

still on the site, its spatial distribution, and therefore its 

functional qualities, is certainly not natural. Windrowing as 

a method of forest site preparation is gradually being 

phased out of forest operations in the South for a variety of 

reasons. Other types of mechanical site preparation, while 

having less effect on CWD than windrowing, still may 

adversely affect the loading, distribution, and duration of 

CWD. 

The effects of broadcast burning or wildfire on CWD 

depend upon the conditions (fuel moisture, weather, and 

firing technique) under which the fire burns. Intense fires 

in periods of extended drought are very severe and may 

consume much of the CWD (Robichaud and Waldrop 

1992). However, consumption of fallen logs by intense fire 

is often minimal if the fire burns under conditions less 

conducive to complete combustion, e.g., higher moisture 

contents of large fuels. Sanders and Van Lear (1988) found 

that CWD volume was reduced under the latter conditions 

by less than 40 percent during intense broadcast fires in 

pine-hardwood logging slash in the Southern Appalachians 

following clearcutting. 

Intensive management practices associated with plantation 

forestry often result in decreases in CWD loading. Short 

rotations are commonly used for pulpwood production. 

Rotations of 30 years or less are too short to allow 

significant quantities of CWD to accumulate. Thinning is 

often used in longer rotations for sawtimber production, 

and this removes trees that are most likely to be CWD 

candidates. More complete utilization of harvested trees 

minimizes the amount of CWD left after harvest. Wholetree harvesting or harvesting techniques that remove most 

of the abovestump biomass from the site are now practiced 

in many locals throughout the South. 

Conclusions 

The ecological importance of CWD has only recently been 

appreciated by foresters and other land managers in the 

South. Based on the documented importance of CWD in 

the Pacific Northwest and other areas, as well as on the 

infomation presented at this workshop, it would be prudent 

for land managers in the Southeast to recognize CWD as an 

important structural and functional component of forest 

ecosystems rather than as a hindrance that must be removed 

at a high cost. 

Managing for CWD will certainly not be a primary 

objective on all forest lands in the South. The South is 

obviously an important timber producer for the Nation and 

the world, and many of the South's forests will be managed 

primarily for timber. However, managers should be aware 

of the important functions of CWD and should use this 

infomation as they strive to achieve balance between 

commodity production and environmental values across the 

landscape. 
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48 p. M.S. thesis. 
Dynamics of Coarse Woody Debris-A Simulation 

o Southeastern Forest Ecosystems 

Thomas A. Waldrop 

Abstract 

The FORCAT gap model was used to simulate formation and 

decomposition of coarse woody debris {CWD) for two forest ecosystems 

on the Cumberland Plateau in east Tennessee. Simulations were 

conducted for 200 years after clearcutting on a total of 100 plots, 1/12 ha 

in size. Model results showed a decrease in CWD loads in early years as 

logging slash decomposed. After year 32, GWD loads increased rapidly 

and peaked around year 90. Coarse woody debris loads in older stands 

gradually decreased through the remainder of the simulation period. The 

assumed decomposition rate strongly influenced CWD loading. Model 

results correspond closely to observed loadings in old-growth stands on 

the Cumberland Plateau. 

Introduction 

While exact efflects are not well documented, few doubt the 

ecological importance of coarse woody debris (CWD) in 

Southeastern ecosystems. Little is known, however, about 

the changes in CWD loads that might be expected over long 

periods, such as through succession. Most studies in the 

Southeast have provided short-term "snapshots" of CWD 

for specific successional stages and have looked at oldgrowth stands (MacMillan 1988; Muller and Liu 199 1; 

Smith and Boring 1990). 

Coarse woody debris dynamics are difficult to predict 

because inputs and losses are affected by many biotic and 

abiotic factors. Inputs are determined by species composition, site quality, and sizes and types of disturbance. 

Losses of CWD are affected by management strategies 

and decomposition rates. Several studies show that 

decomposition rates depend on multiple factors 

including species (Harmon 19821, climate (Muller and Liu 

1991), site (Abbott and Grossley 1982), size of material 

(Mattson and others 1987), and contact with the ground 

(Barber and Van Lear t 984). 

Van Lea (1996) discusses current research on CWD 

dynamics in the Southeast elsewhere in these proceedings, 

so I cite only a few studies here. A study conducted in 

western Oregon and Washington provides the most 

complete description of long-term CWD dynamics to date. 

Spies and others (1988) and Spies and Cline (1988) 

Reseivch Forester, USDA Forest Service, Southern Research Station, 239 

Lehotsky Hall, Clemson, SC 29634-1003. 

described CWD loading in 196 Douglas-fir, Pseudotsuga 

menziesii (Mirb.) Franco, stands across a chronosequence 

ranging from 40 to 900 years since disturbance. This work 

serves as a comparison for my simulation study, so I will 

provide its results in some detail. 

Loading of CWD over the 900-year chronosequence was 

described for five successional stages: stand initiation, stem 

exclusion, understory reinitiation, old growth, and climax. 

During the stand initiation stage (lasting 20 to 30 years), 

accumulation of CWD was slow (fig. I). Even though tree 

mortality was high during this period, most trees were too 

small to be considered CWD. Coarse woody debris inputs 

began during the stem exclusion period (lasting 10 to 30 

years) as the canopy closed and mortality of larger trees ; began. Input rates were relatively low during this period 

because many dying trees were small. Canopy dominance 

diminished during the understory reinitiation stage (lasting 

100 to 150 years), allowing understory herbs, shrubs, and 

trees to become established. Mortality of some large trees 

began during this period and CWD accumulated rapidly. 

I 

Coarse woody debris continued to accumulate rapidly 

during the old-growth stage (lasting 500 to 800 years) as 

natural disturbances such as windthrow, diseases, and 

insects increased mortality rates of large trees (fig. 1). 

Much of the mortality during this period was among 

dominant shade-intolerant species, which were replaced by 

shade-tolerant species. The shade-tolerant species were 

Figure I-Accumulation of coarse wdy debris across a 9W-year 

chronosequence for ecosystems of westem Oregon and Washington (Spres 

and Cline 1988). I 

I 
relatively long lived and contributed little CWD during 

the later years of the old-growth stage. Late in the oldgrowth stage, decomposition began to exceed inputs and 

CWD loading decreased. 

The climax stage was reached when all shade-intolerant 

species were replaced by shade-tolerant species (fig. 1). 

This stage had less CWD than the old-growth stage because 

it lacked the original overstory dominants. Coarse woody 

debris dynamics during this stage were difficult to describe 

because few of these stands existed. Usually, by this time, 

either natural or anthropogenic disturbance had reinitiated 

succession. 

A lack of similar information about long-term CWD 

dynamics in southeastern ecosystems prompted the 

simulation study described in this paper. I used a 

previously developed model of forest succession to simulate 

stand dynamics, and I estimated CWD loading from 

predicted tree mortality. My objectives were to provide 

basic information on long-term CWD dynamics in 

Southeastern ecosystems and to identify information gaps. 

Methods 

Description of the Model 

The model used for this study was FORCAT (FORests of 

the CAToosa Wildlife Management Area), which was 

developed for mixed-species forests on the Cumberland 

Plateau in east Tennessee (Waldrop and others 1986). 

Although the major reason for selecting FORCAT was my 

farniliarity with the model, it is one of only a few existing 

models capable of simulating long-term stand dynamics for 

managed, mixed-species stands (Waldrop and others 1989). 

FORCAT is a member of a family of models based on the 

widely used FORET model (Shugart and West 1977). 

FORET is described by Shugart (1984) as a spatial gap 

model that simulates stand dynamics for the forests of east 

Tennessee. Cap models are a special case of single-tree 

models and have demonstrated adaptability over a wide 

range of forest types. Simulated gaps range from 0.04 to 

0.08 ha in size (Shugm and West l979), approximating the 

area opened by the death or removal of an individual 

canopy tree (Shugart and West 1980). These models 

generally use simple equations, with parameters that are 

easily obtained, to approximate the mechanisms that cause a 

forest to change on a small plot of land. Such changes are 

simulated through the bir~h, growth, and death of individual 

trees as controlled by vakous measures of competition and 

other environmental stress factors. Variables used in gap 

models as environmental stress factors include shade, stand 

basal area, soil moisture, and ambient temperature. 

The FORCAT model was developed through numerous 

modifications to FORET, making it more specific to 

managed sites on the Cumberland Plateau (Waldrop and 

others 1986). The model simulates stand dynamics on a 

0.08-ha plot using 30 hardwood and 3 pine species 

commonly found in the region. Simulation begins with a 

mature stand, which is immediately clearcut. After 

clearcutting, sprouts and seedlings are stochastically added 

to simulated plots based on silvical characteristics of each 

species. Diameter and height growth are calculated each 

year for each tree as a function of site, species, competition, 

and environmental stress. Trees are killed stochastically 

each year based on age, species, and current growth rates. 

Some of the more significant changes to FORET that were 

included in FORCAT were: (1) beginning the simulation 

with natural regeneration found in clearcuts instead of bare 

ground, (2) basing growth rates on site quality and local 

climate, (3) basing seed availability and sprouting habit on 

species-specific characteristics, and (4) simulating periodic 

clearcutting and prescribed burning. FORCAT was 

developed and tested for a xeric hardwood site and 

validated with data from a nearby mesic oak site. 

Many of the growth and mortality equations used in 

FORCAT and FORET were adapted from the JABOWA 

model for northern hardwoods (Botkin and others 1972). 

Shugart and West (1977), Shugart (1984), and Botkin 

( 1993) described those equations in detail. Shugart (1 984) 

also discussed gap models at length. Waldrop (1983) and 

Waldrop and others (1986) described development and 

validation of FORCAT. 

Modeli~lg Caarse Woody Debris Dynamics 

Few changes to FORCAT were required to predict CWD 

loading. In FORCAT, the diameter at breast height (d.b.h.) 

of each tree on the simulated plot (up to 1,200 trees in 

young clearcuts) is updated each year according to growth 

calculations and then stored in an may. If a tree dies in 

any year, the d.b.h. of that tree is removed from the storage 

array. At that point, the dead tree was considered CWD and 

its biomass was estimated. Biomass was estimated for both 

stems and crowns using d.b.h. as the independent variable 

in regression equations given by Clark and others (1986). 

To account for limbs too small to be considered CWD 

(diameter less than l 0 cm), estimated crown biomass was 

reduced by 20 percent. 
The total biomass of dead stems and crowns on a plot was 

calculated for each year. This amount was added to the 

total CWD remaining from the previous year, and the new 

sum was reduced by a constant rate to allow for 

decomposition. Decomposition rates of 6 percent, 8 

percent, and 10 percent were used to examine the 

differences these rates caused in CWD accumulation. 

These decomposition rates roughly follow those reported 

by Harmon (1982) for hardwood species. 

Stand dynamics and CWD accumulation were simulated for 

the two site types (xeric and mesic) that were used to 

develop and validate FORCAT. The results of these 

simulations should give some insight into the effect of site 

productivity on CWD accumulation. Model input for the 

xeric site was data from a stand with a basal area of 19.3 

m21ha and dominated by post oak (Quercus stellata 

Wangenh.), southern red oak (Q. falcata Michx.), and 

scarlet oak (Q. coccinea Muenchh.) (table 1). The xeric 

site was characterized by thin, acidic soils and moderate 

topography. It had a site index of 18 m for upland oaks 

(base age SO). For the mesic site, basal area of commercialsized trees was 17.6 mz/ha and species composition was 

mostly chestnut oak (Prinus L.), white oak (Q. alba L.), 

northern red oak (Q. rubra L.), and yellow-poplar 

Table 1-Species composition for xeric and mesic sites 

used as input to FORCAT 

Species Xeric site Mesic site 

Black oak 

Chestnut oak 

Northern red oak 

Post oak 

Scarlet oak 

Southern red oak 

White oak 

Other oaks 

Hickories 

White ash 

Yellow-poplar 

Other hardwoods 

Virginia pine 

Total basal area (pct) 

(Liriodendron tulipifera L.). The mesic site had a northern 

aspect, moderate to steep slopes, and a site index of 3 1 m 

for yellow-poplar (base age 50). 

Simulations began with mature stands, which were 

immediately clearcut. No artificial regeneration or site 

preparation was allowed. A simulation period of 200 years 

after clearcutting was used for each of 100 simulated 111 2- 

ha plots. Due to the stochastic nature of the growth and 

mortality calculations, no two simulated plots were 

identical. Shugart and West (1979) suggested including 

100 plots in simulations to account for the variability found 

in most Southeastern forest types. 

Several limitations to this approach of modeling CWD 

accumulation are recognized. By defining CWD as dead 

trees, standing CWD cannot be distinguished from down 

CWD. Also, CWD estimates are likely to be low because 

inputs from limbs that die and fall to the ground are not 

included. Another limitation is that decomposition rates are 

assumed to be the same for all species and size classes of 

CWD and across all successional stages. Published 

decomposition rates were not available for the species and 

types of sites that FORCAT simulates. The simulations do 

not include CWD inputs from natural disturbances or from 

anthropogenic disturbances, other than the initial clearcut, 

Results and Discussion 

Coarse Woody Debris Dynamics After Clearcutting 

On the xeric site, simulated regeneration was dominated by 

sprouts of oak species (39 percent of all stems) that were 

abundant in the preharvest stand. Understory hardwoods 

that sprout prolifically, such as dogwood (CornusJlorida 

L.) and sourwood (Oxydendron arboreum L.), made up 

another 30 percent of the regeneration. Pine seedlings 

represented less than 1 percent of the regeneration. 

Throughout the simulation period, understory hardwoods 

gradually declined in importance while scarlet oak, post 

oak, and southern red oak eventually dominated the stand. 

For the mesic site, simulated regeneration was dominated 

by northern red oak, white oak, hickories (Carya sp.), white 

ash (Fraxinus americana L.), and blackgum (Njissa 

sylvatica Marsh.). No pine regeneration was predicted. By 

the end of the simulation, the stand was dominated by 

northern red oak, chestnut oak, white oak, and yellow-poplar. 

The patterns of CWD accumulation predicted by FORCN 

(fig. 2) for xeric and mesic sites (using a 6-percent 

decomposition rate for both sites) were similar to the curve 
proposed by Spies and Cline (1988) for western Oregon 

and Washington (fig. 1 ). In all three systems, this pattern 

resembled a bell-shaped curve that peaked during the first 

half of their respective periods (100 years for simulated 

xeric and mesic sites, 450 years for measured Douglas-fir 

stands). Later, CWD in each system gradually decreased 

until a point, late in succession, where an equilibrium 

between inputs and decomposition may have been reached. 

Coarse woody debris accumulation on both simulated sites 

remained low for 30 to 40 years as trees grew to the 

minimum size for CWD (10 em), even though there was 

significant mortality during this period (fig. 2). Between 

years 30 and 75 CWD increased rapidly for both simulated 

sites. FORCAT predicted decreases in stand basal area 

during this period as crown closure occurred and a few 

large trees began to die. On the xeric site, for example, 

predicted stand basal area decreased from 19.3 m2 per ha at 

year 50 to 15.9 m2 per ha at year 100. 

1 50 100 150 200 

Years 

Figure 2-Accumulation of coarse woody debris for xeric and mesic sites 

as predicted by FORCAT (ti-percent decomposition rate for both sites). 

The period of rapid CWD accumulation on the xeric site 

lasted until the stand was about 70 years old (fig. 2) when 

CWD was 30.6 Mega grams per hectare (Mgha). Coarse 

woody debris continued to accumulate, but at a slower rate, 

to a maximum of 32.5 Mgha at year 9 1. For the remainder 

of the 200-year simulation period, decomposition slightly 

exceeded inputs and CWD loads gradually decreased. 

Tree growth on the simulated mesic site exceeded that on 

the xeric site, producing a more rapid rate of CWD 

accumulation (fig. 2). On this site, CWD accumulated 

rapidly from years 30 through 75, reaching a total of 49.3 

Mglha. Maximum CWD loading during the simulation 

period was 5 1.4 Mgha in year 89. Between years 90 and 

200, CWD loading decreased much more rapidly than on 

the xeric site. Species on the mesic site were longer lived 

than those on the xeric site and the trees continued to grow. 

Mortality was higher on the xeric site during this period 

due to moisture stress. Therefore, CWD inputs were less 

on the mesic site than on the xeric site. 

FORCAT predictions for CWD accumulation in older 

stands were similar to the ranges observed by Muller and 

Liu (1991) for old-growth stands on the Cumberland 

Plateau. Between years 90 and 200 (roughly equivalent to 

the age of old-growth stands), CWD loads on the 

simulated xeric site ranged from 22.8 to 32.5 Mgha (fig. 

2). Muller and Liu (1991) reported accumulations ranging 

from 22 to 32 Mgha on dry sites including ridgetops, 

upper slopes, and south-facing and west-facing midslopes. 

Older stands on the simulated mesic site had CWD loads 

ranging from 30.0 (year 200) to 5 1.4 Mg/ha (year 90). 

Muller and Liu (1991) found CWD loads ranging from 34 

to 49 Mgha on moist rnidslopes with a north or east 

aspect. 

Even though FORCAT accurately predicted more CWD 

input on the mesic site than on the xeric site, the periods of 

accumulation (years 30 through 90) were nearly identical. 

This may indicate a failure of the model. I expected CWD 

loading to peak higher and later on the mesic site than on 

the xeric site because the species on the mesic site grow 

larger and are longer lived. A common problem among 

mixed-species models is an inability to simulate 

competition of different species across sites of varying 

quality. Since FORCAT development was based on 

xeric sites, its growth parameters for mesic sites may 

not be as accurate. 

Logging Debris 

An important, but so far neglected, component of CWD 

dynamics in managed stands is logging debris. For 

example, Sanders and Van Lear (1988) found that CWD 

after clearcutting in the Southern Appalachians can be as 

much as 90 Mgha. This debris provides regenerating 

stands with a structure that can be important habitat for 

small mmmals (Evans and others 199 1 ; Loeb 1996) as 

well as a source of nutrients (Mattson and others 1987). 

Logging slash was added to model projections of CWD 

inputs immediately after simulated clearcutting. Total 

CWD loading at that time was assumed to equal the 

biomass of crowns from harvested trees. Crown biomass 
was estimated by using the d.b.h. of each hmested tree 

(xeric and mesic sites) as the independent variable in 

regression equations given by Clark and others (1986). 

These estimates were reduced by 20 percent to account for 

the portions of crowns too small to be considered CWD 

(< 10 cm in diameter). 

The estimated CWD load immediately after clearcutting 

was 49 Mgfha on the xeric site and 69 Mgfha on the mesic 

site (fig, 3). On both sites, these levels were higher than at 

any other time during the 200-year simulation period. 

Figure 3 illustrates the importance of selecting sitepreparation techniques that leave some CWD. Logging 

debris decomposes rapidly in clearcuts, but it provides 

some CWD during a period when there is little input. In 

my model, decomposition exceeded inputs through year 32. 

At that time CWD, totaled 16.9 Mgha on the xeric site and 

18.3 Mgha on the mesic site (assuming a uniform 

decomposition rate of 6 percent). By year 32, all logging 

slash had decomposed. Therefore, after year 32 these 

curves were identical to those without logging slash (fig. 2). 

Variable Decomposition Rates 

An assumption used until now is that decomposition rates 

were uniform across site types. The work of Abbott and 

Crossley (1982) indicates that decomposition rates are 

higher on moist sites. By assuming a decomposition rate of 

8 percent on the mesic site and 6 percent on the xeric site, 

the difference in simulated CWD loads between sites was 

greatly reduced (fig. 4). Even though CWD loading was 

much higher on the mesic site in year 1, it decomposed to a 

smaller amount than the xeric site by year 32 (12.3 present 

vs. 16.9 Mgfha). By year 75, CWD was again greater on 

the mesic site. Beyond that point, however, the lines 

converged. During the last 50 years of the simulation, 

CWD loads on the two simulated sites were nearly 

identical. 

This comparison (fig. 4) illustrates the observation of 

Abbott and Crossley (1982) that differences in 

decomposition rates between sites can be more important 

than differences in sizes of CWD. Even though the mesic 

site produced far more CWD biomass than the xeric site, 

the relatively small difference in decomposition rates (8 vs. 

6 percent) produced similar CWD loading throughout the 

200-year simulation. If the difference in decomposition 

rate is larger (10 percent vs. 6 percent), CWD loading 

can be greater on the xeric site for most of the simulation 

period (table 2). 

Muller and Liu (1991) suggested that CWD loading was a 

function of regional temperature pattems. Their 

measurements on dry sites conelated well with published 

estimates from warm Temperate Zone deciduous forests. 

Likewise, their CWD rneasurements on moist sites 

correlated well with published estimates from cool forests. 

Muller and Liu (1991) observed higher CWD loads on cool 

(moist) sites than on warm (dry) sites, suggesting that 

decomposition rates were not higher on moist sites or that 

higher productivity on moist sites compensated for higher 

decomposition rates. Broad-scale relationships, such as 

this, are oversimplified because CWD decomposition on 

any given site is controlled by a combination of moisture, 

temperature, soil fertility, species, size, and any number of 

other factors. 

o'; a a a 

50 100 1 50 200 

Years I 

Figure 3-Dynamics of coarse woody debris after clearcutting xeric and 

mesic sites (predicted by FORCAT using a 6-percent decomposition rate 

for both sites). 

- Mesic - 8% Decomposition 

- Xeric - 6% Decomposition 

I 

0 r 

1 50 100 150 208 i 

Years I 

I 

Figure GFORCAT projections of coarse woody debris loads by site type 

and decomposition rate. 
Table 2Zoarse woody debris accumulation by site and 

decomposition rate as predicted by FORCAT 

Decomposition rate 

Site 6 pct 8 pet 10 pct 

Xeric 

Year 1 (after clearcutting) 49.0 49.0 49.0 

Year 32 (nninimum CWD load) 16.9 1 1.8 8.5 

Year 9 1 (maximum CWD load) 32.5 24.5 19.6 

Year 200 (end of simulation) 22.8 16.5 12.9 

Mesic 

Year 1 (after clearcutting) 68.9 68.9 68.9 

Year 32 (~nimum CWD load) 18.3 12.3 8.9 

Year 89 (maximum CWD load) 5 1.4 39.8 32.3 

Year 200 (end of simulation) 30.0 22.4 17.9 

Conclusions 

The FORCAT gap model worked well for this preliminary 

attempt to simulate CWD dynamics in two types of 

Southeastern ecosystems. Model results were similar to 

those of two field studies. The pattern of CWD 

accumulation predicted by FORCAT was similar to that 

observed in Western ecosystems (Spies and Cline 1988). 

Also, the predicted CWD loads were nearly equal to those 

reported by Muller and Liu (1991) for ecosystems similar 

to those simulated by FORCAT. 

Results of this study show general trends of CWD 

accumulation over seral stages for the two Southeastem 

forest ecosystems used in the study. The result of this study 

shows the importance of leaving CWD after harvesting and 

emphasize that differences in decomposition rates (possibly 

due to differences in site productivity) can significantly 

affect CWD loading. Due to a number of limitations, 

however, model projections should not be considered 

accurate predictions of CWD loading at any given age. 

natural and anthropogenic disturbance. Some of this 

missing infomation could be supplied by additional 

research and a broader modeling effort. For example, CWD 

dynamics after natural disturbances such as tornados or ice 

storms could be predicted by gap models if the return 

frequency of those disturbances was known. Also, CWD 

inputs from management activities such as thinning5 or 

selection harvests could be predicted. This effort would 

allow managers to use model projections to help determine 

how to alter the level or timing of their activities to better 

meet their goals for CWD. 

A major limitation found in this study was the lack of 

infomation on inputs and decomposition rates for different 

tree species, sizes of CWD, and types of sites. Other 

knowledge gaps were discussed by Van Lear (1995) at this 

workshop, including the relationship of CWD inputs to 
Literature Cited Shugart, H.H.; West, D.C. 1979. Size and pattern of simulated forest 

stands. Forest Sctence. 25: 120- 122. 

Abbott, D.T.; Crossley, D.A., Jr. 1982. Woody litter decomposition 

following clear-cutting. Ecology. 631 1):35-42. 

Barber, B.L.; Van Lear, D.H. 1984. Weight loss and nutrient dynamics 

in decomposing woody loblolly pine logging slash. Soil Science 

Society of America Journal. 48(4):906-910. 

Botkin, D.L.; Janak, J.F.; Wallis, J.R. 1972. Some ecological consequences of a computer model of forest growth. Journal of Ecology. 

60:849-872. 

Botkin, Daniel B. 1993. Forest dynamics: an ecological model. New 

York: Oxford University Press. 309 p. 

Clark, Alexander, 111; Phillips, Douglas R.; Frederick, Douglas J. 

1986. Weight, volume, and physical properties of major hardwood 

species in the Upland-South. Res. Pap. SE-257. Asheville, NC: U.S. 

Department of Agriculture, Forest Service, Southeastern Forest 

Experiment Station. 55 p. 

Evans, Timothy L.; Guynn, David C., Jr.; Waldrop, Thomas A. 199 1. 

Effects of fell-and-burn site preparation on wildlife habitat and small 

mammals in the Upper Southeastern Piedmont. In: Nodvin, Stephen 

C.; Waldrop, Thomas A., eds. Fire and the environment: ecological 

and cultural perspectives: Proceedings of an international symposium; 

1990 March 20-24; Knoxville, TN. Gen. Tech. Rep. SE-69. Asheville, 

NC: U.S. Department of Agriculture, Forest Service, Southeastern 

Forest Experiment Station: 160- 167. 

Harmon, Mark E. 1982. Decomposition of standing dead trees in the 

Southern Appalachian Mountains. Oecologia. 52:2 14-2 15. 

Loeb, Susan C. 1996. The role of coarse woody debris in the ecology of 

southeastern mammals. In: McMinn, James W.; Crossley, 

D. A., Jr., eds. Biodiversity and coarse woody debris in southern 

forests, proceedings of the workshop on coarse woody debris in 

southern forests: effects on biodiversity; 1993 October 18-20; Gen. 

Tech. Rep. SE-94. Asheville, NC: U.S. Department of Agriculture, 

Forest Service, Southern Research Station. 

MacMiIlan, Paul C. 1988. Decomposition of coarse woody debris in an 

old-growth Indiana forest. Canadian Journal of Forest Research. 

1%(11): 1353-1362. 

Mattson, Kim G.; Swank, Wayne T.; Waide, Jack B. 1987. Decomposition of woody debris in a regenerating, clear-cut forest in the Southern 

Appalachians. Canadian Journal of Forest Research. 17:7 12-72 1. 

Muller, Robert N.; Liu, Yan. 199 1. Coarse woody debris in an oldgrowth deciduous forest on the Cumberland Plateau, Southeastern 

Kentucky. Canadian Journal of Forest Research. 2 1 : 1567- 1572. 

Sanders, Bradford M.; Van Lear, David H. 1988. Photos for estimating 

residue loadings before and after burning in Southern Appalachian 

mixed pine-hardwood clearcuts. Gen. Tech. Rep. SE-49. Asheville, 

NC: U.S. Department of Agriculture, Forest Service, Southeastern 

Forest Experiment Station. 21 p. 

Shugart, Herman He 1984. A theory of forest dynamics: the ecological 

implications of forest succession models. New York: Springer-Verlag. 

278 p. 

Shugart, Herman H.; West, Darrell C. 1977. Development of an 

Appalachian deciduous forest succession model and its application to 

the assessment of the impact of the chestnut blight. Journal of 

Environmental Management. 5: 16 1- 179. 

Shugart, Herman H.; West, Darrell C. 1980. Forest succession models. 

Bioscience. 30:308-3 13. 

Smith, Robert N.; Boring, Lindsay R. 1990. Pinus rigida coarse woody 

debris inputs and decomposition in pine beetle gaps of the Southern 

Appalachians. Program and abstracts of the 75th annual Ecological 

Society of America meeting. 1990 July 29-August 2; Snowbird, UT. 

Tempe, AZ: Supplement to The Ecological Society of America 

Bulletin. 71 :2. 329. 

Spies, Thomas A.; Cline, Steven P. 1988. Coarse woody debris in forests 

and plantations of Cozstal Oregon. In: Maser, Chris; Tamant, Robert 

F.; Trappe, James M.; Franklin, Jerry F., tech. eds. From the forest to 

the sea: a story of fallen trees. Gen. Tech. Rep. PNW-229. Portland, 

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

Northwest Research Station: Chapter 2. 

Spies, Thomas A.; Franklin, Jerry F.; Thomas, Ted B. 1988. Coarse 

woody debris in Douglas-fir forests of western Oregon and Washington. Ecology. 69(6): 1689- 17 12. 

Van Lear, David H. 1996. Dynamics of coarse woody debris in southern 

forests. In: McMinn, James W.; Crossley D. A., Jr., eds. Biodiversity 

and coarse woody debris in southern forests, proceedings of the 

workshop on coarse woody debris in southern forests: effects on 

biodiversity; 1993 October 18-20; Gen. Tech. Rep. SE-94. Asheville, 

NC: U.S. Department of Agriculture, Forest Service, Southern 

Research Station. 

Waldrop, T.A.; Buckner, E.R.; Shugart, H.H., Jr.; McGee, C.E. 1986. 

FORCAT: A single tree model of stand development following 

clearcutting on the Cumberland Plateau. Forest Science. 

32(2):297-3 19. 

Waldrop, Thomas A, 1983, The development of FORCAT: a spatial gap 

model of stand dynamics for forests of the Catoosa Wildlife 

Management Area. Knoxville, TN: University of Tennessee, 

Knoxville, TN. 207 p. Ph. D. dissertation. 

Waldrop, Thomas A*; Lloyd, F. Thomas; Abercrombie, James A., Jr. 

1989. Fell and burn to regenerate mixed pine-hardwood stands: an 

overview of research on stand development. In: Waldrop, Thomas A., 

ed. Proceedings of pine-hardwood mixtures: a symposium on 

management and ecology of the type; 1989 April 18- 19; Atlanta, GA. 

Gen. Tech. Rep. SE-58. Asheville, NC: U.S. Department of 

Agriculture, Forest Service, Southeastern Forest Experiment Station: 

75-82. 
Coarse Woody Debris in Forest Ecosystems: 

An Overview of Biodiversity Issues and Concepts 

C. Ronald Carroll 

Abstract 

A central question is, "Why are there so many species?Xttempts to 

answer the question have generally followed the broad themes of (1) 

explaining via historical, biogeographical processes, and (2) examining 

local patterns of diversity in the context of random/stochastic events, 

primary productivity levels, competitive interactions, or processes that 

prevent equilibrium. Since general, implied hypotheses are difficult to 

formulate as testable null hypotheses, examinations of biodiversity 

processes have relied on several different measures of community 

structure. The coarse woody debris-biodiversity relationship is amenable 

to rigorous experimental approaches because coarse woody debris occurs 

in discrete, quantifiable units that can be easily manipulated. 

Introduction 

A central question that has preoccupied the thinking of 

ecologists is, "Why are there so many species?'In recent 

years, this biodiversity question has expanded to include 

both finer levels of resolution (genetic diversity) and higher 

patterns (beta and gamma diversity). Attempts to 

understand the factors that influence biodiversity have 

generally followed two broad themes: (1) Explanations for 

regional patterns of biodiversity rely on historical, 

biogeographic processes, (2) Explanations for local patterns 

of biodiversity most likely evoke some combination of 

random, stochastic events; levels of primary productivity; 

the outcome of equilibria1 competitive interactions; or, 

conversely, processes that prevent population densities from 

reaching equilibrium levels. The most common 

explanations for biodiversity patterns are presented, and 

briefly described, in table 1. For a more complete 

discussion of biodiversity concepts and patterns, see 

Orians (1994). 

To varying degrees, these hypotheses suffer from problems 

of validation. Although they are presented as hypotheses, 

they are extsemely difficult to formulate as testable null 

hypotheses that can, at least in principle, be rejected or 

accepted based on experimentation. The only recourse, in 

most cases, has been to search for patterns that are 

consistent with particular hypotheses. For example, in 

Associate Director and Senior Research Ecologist, Institute of Ecology, 

University of Georgia, Athens, GA 30602. 

animal communities little empirical evidence exists to 

support the hypothesis that environments with high primary 

productivity support more species than less productive 

environments. Indeed, some very productive environments, 

(e.g., estuaries and eutrophic lakes), are notably 

depauperate in animal species. Thus, the ascendancy of any 

particular hypothesis is strongly influenced by the weight of 

evidence favoring it rather than by the outcome of critical 

experiments or analysis. 

Because direct experimental examination has proven to be 

difficult, most attempts to examine biodiversity processes 

relied on indirect measures of community structure. Some 

common examples include the following: 

1. The existence of morphological character displacement 

where two species co-occur is used as presumptive 

evidence that competition was an important evolutionary 

factor in the community. 

2. Species-area relationships are sometimes used to draw 

inferences about the extent to which particular habitats have 

reached their equilibrium number of species or as estimates 

of the total number of species that are expected to be 

present. This approach is burdened by many assumptions 

that are generally not made explicit. Among those are 

responses of biodiversity to increases in sample area or to 

changes in some resource density or pattern. 

3. Habitats that can be arrayed by increased species 

diversity due to the addition of new species, rather than 

by replacement of species, are referred to as exhibiting 

nested subsets. It is unclear what ecological mechanisms 

are responsible for nested subset behavior, but two 

conclusions seem reasonable. First, nested subset behavior 

suggests that local biodiversity is not strongly influenced 

by species interactions. Second, the absenceof the nested 

subsets could be due to many factors. 

4. Recurrent groups are clusters of species that characterize 

a habitat type. Under particular circumstances, other 

species may be added, but the recurrent groups will be 

relatively constant. The concept was introduced by Fager 

(1957), who identified a central recurrent group of 23 

invertebrates in decaying oak wood with 10 smaller groups 

that occurred under particular circumstances. The extent to 
Table 1-A synoptic list of the more common hypotheses evoked to explain patterns of biodiversity 

Regional Biodiversity 

Biogeographic Constraints. Regional biotic patterns are determined by such geological processes as (1) the 

fomatioddisappearance of land bridges due to changes in sea level, and (2) the formation of mountains and other 

barriers and the isolation of continents through large tectonic plate movements. Global climate change can also isolate 

biotas through the creation of climatic barriers, e.g., isolating biota on mountain tops during periods of warming 

temperature. 

Stabiliq Ujlpothesis: Relatively constant environments permitjner evolutionary niche partitioning, more 

specialization, and hence, greater species packing in communities. This hypothesis has been evoked to explain the 

relatively rich diversity of deep marine benthic communities. 

Local Biodiversity 

Productiviq Hypothesis: Habitats with high-primary productivity support more species than habitats with lowprimary productivity. Clearly, very low productive environments, such as very arid deserts, have low species diversity; 

however, there seems to be no consistent relationship between primary productivity and local species diversity. An 

apparent exception is the general relationship between increasing levels of potential evapotranspiration and plant 

species diversity. 

Structural Hjrpothesis: Habitats that are structurally more complex support more species than habitats with simple 

structure. Physical complexity produces more potential microclimates, substrates, and refugia from predators; hence, 

more physical niches for species. For example, the addition of inert physical structures, such as glass plates, into 

experimental ponds provides more substrate for algae and diatoms, thereby increasing species diversity. 

Competitive/Predation Hypothesis: In ecological time, competitive displacement reduces species diversity while 

predation may either increase or decrease species diversity. The extent to which natural communities are structured by 

competition is still an open question despite decades of field and theoretical work premised on the importance of 

competition in nature. In competitively structured communities, predation on the competitively dominant species can 

prevent competitive displacement, thereby helping to maintain local diversity. The classic example is predation by 

starfish on competitively dorninant mussels in the Pacific Northwest, giving rise to the notion of "keystone predators'" 

(Paine 1966). Of course, predation can also simplify communities by exterminating prey species. 

Intermediate Disturbance Hypothesis: EIabituts with very low or very high levels of disturbance have fewer species 

than habitats with intemediate levels of disturbance. In very constant environments, populations reach densities at 

which competitive displacement removes species. Habitats Ihat undergo constant disturbance contain only species wifi 

high colonization abilities. This hypothesis emphasizes the importance of the interplay of equilibria1 (generally 

competition) and nonequilibrial (stochastic disturbances) processes to explain local patterns sf biodiversity. An 

example may be the role of treefall disturbances in tropical forests that maintain colonizing tree species and provide the 

light resources to pemit growtt? of young noncolonizing tree species. 

The Hypothesis: Species diversity increases over time. Some habitats are too new to have accumulated a full 

complement of species, e.g., land exposed by a retreating glacier, landslides, changes in river courses, etc. 
which recurrent groups exist is an empirical question that 

warrants additional fieldwork. But, when recurrent groups 

are found, what does it mean? Several explanations seem 

plausible. The presence of recurrent groups could simply 

indicate a cluster of particularly good colonizing species. 

Conversely, recurrent groups could represent species that 

are highly adapted to the particular habitat or resource. 

The latter seems far more likely and suggests that the 

existence of recurrent groups should be an important focus 

of research. 

5. Species do not seem to be added to habitats at random; 

rather, a sequence is followed, albeit very loosely in many 

cases. The extent to which such sequences can be predicted 

suggests that "assembly rules" are important for explaining 

succession or species richness. Most commonly, assembly 

rules are used to imply that the successful establishment of 

later species is dependent on the prior presence of 

particular earlier species. That is, the earlier species 

"condition" the habitat and influence subsequent patterns of 

species establishment. Assembly rules have most 

commonly been used to explain the temporal process of 

island colonization. 

Biodiversity Concepts: The Potential 

Contribution from Coarse Woody Debris 

Communities 

Biodiversity studies of coarse woody debris (CWD) 

communities have a number of advantages over other 

systems: 

0 CWD comes in discrete units (stems and logs). 

0 CWD can be experimentally manipulated (stems and 

logs can be moved). 

0 ChVD comes in diEerent volumes (sizes from small 

stems to large logs). 

a CWD comes in diEerent ages (freshly fallen to decayed). 

0 CWD comes in diEerent resource qualities (species and 

decomposition stage). 

Potential Manipulation Experiments 

Because CWD can be readily manipulated in field 

experimental designs, some biodiversity hypotheses can be 

tested in more rigorous ways. 

Productivity Hypothesis 

How are numbers of individuals or total species biomass 

related to diversity of CWD organisms? Does the form of 

the productivityldiversity relationship change as a function 

of CWD size or tree species? 

Structural Hypothesis 

Do mixed-sized classes of CWD support more species than 

patches made up of single-sized classes? Are large diameter 

logs more structurally diverse than smaller diameter logs? 

That is, at what diameter class do species begin to show 

physical niche separation in the log? How important is tree 

species diversity of CWD to the biodiversity of the CWD 

communities? What about topographic heterogeneity, e.g., 

do areas with both wet and dry sites support more CWD 

species than areas that are either generally dry or 

generally wet? 

Competition/Predation Hypothesis 

Do predators increase or decrease species diversity? Do 

larger logs provide more prey refugia? How do prey refugia 

change as a function of the stage of CWD decomposition? 

Intermediate Disturbance Hypothesis 

How do periodic fires influence the long-term average 

species diversity of CWD communities? 

Stability Hypothesis 

How is CWD half-life related to species richness? Is there a 

rate of CW decomposition that maximizes biodiversity? 

Over the entire process of decay, does CWL> with long 

half-times of decay support more or fewer species than 

CWD with short half-times? Are rates of decay and 

biodiversity influenced more by the temporal varian~e or 

the mean temperature or moisture? 

Stmcture of Biotic Co 

Although the most important feature of CWD is its 

suitability for experimentation, various indirect community 

structure questions can be addressed as well. 
Species "'Area" Relationship 

Is there a constant species-CWD volume relationship? 

Wow does the slope (57: value) of this function compare to 

the slopes found in historical studies of mainland or island 

communities? What deternines levels of beta-diversity in 

CWD organisms, e.g., is the value of beta greater in CWD 

patches made up of mixed tree species? Wow do the beta 

values for CWD organisms compare to aboveground 

vegetation beta values? 

Assembly Rules 

How important are early colonizing decay fungi to 

subsequent patterns of diversity and rates of species 

change? If the early colonizing fungi are white rot versus 

blue stain, does the difference influence subsequent 

diversity patterns and processes in more than the short 

tern? Do biogeographic faunal/fungal differences influence 

the patterns and processes of biodiversity in CWD? For 

example, does the absence of large passalid beetles in the 

Pacific Northwest influence CWD colonization by affecting 

the distribution of tunnel diameters? Does the absence of 

strong assembly rules suggest a large degree of functional 

redundancy in the CWD faunae? 

Nested Subsets 

Wow common are nested subset patterns in different CWD 

communities? What determines the addition of satellite 

groups? What do recurrent groups suggest about functional 

redundancy in CWD decay communities? If strong patterns 

of recurrent groups are found, should they be treated as a 

kind of aggregate "keystone species complex"? 

Some Concluding Thoughts 

The analysis of biodiversity in CWD communities should 

emphasize experimentation. In particular, a 'kommon 

garden" approach wherein CWD is translocated into 

different environments will be important. Such an approach 

would make it possible to sort out confounding factors such 

as differences in tree species, stand history, and local 

climate. For example, fallen logs of longleaf pine (Pinus 

palustris) appear to have relatively depauperate decay 

communities. Is this due to pbysical/chemical properties of 

this pine, such as its large amount of pitch resin, or, to the 

variable moisture levels in sandy coastal plain soils, or to 

the fact that high-fire frequency lowers CWD faunal 

diversity at the regional level? 

I 

There is also a need to consider landscape scale effects on 

biodiversity. For example, the extraction of turpentine, 

gums, and resins used to be a major forest industry in the 

southern pine region. During that period, the turpentine 

borer (Buprestis apricans) was the most serious pest, often 

limiting production and subjecting the tunnel-ridden trees 

to wind breakage (Baker 1972; Beal 1932). Because the 

beetle is strongly attracted to the slashes for resin extraction 

points and oviposits in these entry points, management 

practices for the extraction of naval stores clearly 

contributed to the enormous populations of this borer and, 

consequently, to large-scale patterns of CWD production. 

After World War 11, the industry declined and pine orchards 

managed for naval stores largely disappeared. 

Subsequently, the turpentine borer has greatly declined in 

abundance. The production practices for naval stores that 

occurred throughout the Southeastern pine lands greatly 

altered CWD production over vast areas. Similarly, other 

regionwide management practices such as prescribed 

burning, low-tree density plantations for timber versus 

higher tree-density plantations for pulp production, and 

mixed hardwoodlconifer production for wildlife will also 

have large-scale effects on CWD production and, hence, on 

its associated biodiversity. 

Literature Cited 

Baker, W.L. 1972. Eastern forest insects. Misc. Publ. 1175. Washington, 

DC: U.S. Department of Agriculture, Forest Service. 

Beal, J.A. 1932. Controls of the turpentine borer in the naval stores 

region. Circ. 226. Washington, DC: U. S. Department of Agriculture. 

Fager, E.W. 1957. Determination and analysis of recurrent groups. 

Ecology. 38:586-595. 

Orians, G.H. 1994. Global biodiversity I: Patterns and processes. In: 

Meffe,G.K.; Carroll, C.R., eds. Principles of conservation biology. 

Sunderland, MA: Sinauer Associates, inc. 

Paine, R.T. 1966. Food web complexity and species diversity. American 

NaturaIist. 100:65-75. 
Coarse Woody Debris and Woody Seedling Recruitment in 

Southeastern Forests 

Rebecca R. Sharitz 

Abstract 

Few studies have examined the role of coarse woody debris (CWD) in 

woody seedling recruitment in Southeastern forests. Elevated substrates 

formed by logs, stumps, and other CWD appear to provide sites for seed 

trapping, germination, and seedling establishment in wetland forests that 

are frequently flooded during all or a portion of the growing season. 

Although their importance to the regeneration of the canopy dominant 

species may be limited, they may enhance the diversity of these forest 

systems by enabling the establishment of a variety of woody species. The 

chief value of CWD to seedling recruitment may be in providing an array 

of microhabitats on the forest floor and increasing environmental 

heterogeneity, thus providing regeneration niches for a mixture of 

species. 

Introduction 

The ecological significance of coarse woody debris (CWD) 

in forests is becoming recognized, partly as a result of 

increased research in recent years (Harmon and others 

1986). Abundant in many natural forest ecosystems, CWD 

functions in energy flow and nutrient cycling, influences 

soil movement, and serves as habitat for numerous 

organisms. It includes a wide variety of types and sizes of 

decaying woody materials: standing snags, fallen logs and 

branches, and stumps. The input of this material to the 

forest floor-whether through small-scale events such as 

individual treefalls or through larger-scale phenomena such 

as wind storms that cause numerous tree blowdownsincreases the heterogeneity of substrates and results in a 

variety of microsites. The availability of a range of 

microsites creates numerous regeneration niches for 

seedlings of different species whose adults may be 

ecologically similar (Grubb 1977). 

Microsites are important to the biological diversity in 

forests. Species richness in plant communities may be 

maintained by a heterogeneous environment acting on a 

series of stages in the reproduction of plants (Grubb 1977). 

The stages include seed production, dispersal, germination, 

seedling establishment, and the survival and growth of 

juvenile plants to reproductive adults. The importance of 

microsites caused by treefalls as new colonization sites for 

tree seedlings in temperate forests has been shown (e.g., 

Collins 1990; Collins and Pickett 1982; Hutnik 1952; 

Schaetzl and others 1989; Webb 1988). Most studies, 

however, have examined seedling establishment on soil 

substrates such as pits and mounds associated with 

uprooted trees, rather than on the decaying woody material. 

Less information exists about the potential role of logs, 

stumps, or other woody debris in forest seedling 

recruitment. Nevertheless, several studies have specifically 

examined woody seedling establishment on decaying logs 

in forests of the United States. Growth of Picea 

Engelmannii and Abies lasiocarpa seedlings on rotting logs 

in a Colorado spruce-fir forest was described by 

McCullough (1 948). Christy and Mack (1 984) reported 

that 98 percent of the Tsuga heterophylla seedlings in an 

old-growth Pseudotsuga menziesii-Tsuga heterophylla 

forest in Oregon were rooted on rotten wood that covered 

only 6 percent of the forest floor. Similarly, in a Picea 

sitchensis-Tsuga heterophylla forest of the Northwest 

Coast, McKee and others (1982) found that 94 to 98 

percent of the tree seedlings were growing on CWD, which 

constituted 6 to 11 percent of the forest floor. In 

experimental studies, survival and growth of seedlings on 

decaying logs in this forest type increased as litter and 

humus accumulations increased (Harmon 1987). 

Harmon (1989) suggested that rotting wood may be more 

important as a seedbed in forests of the Pacific Northwest 

because it covers more of the forest floor there (6 to 25 

percent) than in other regions of the United States (1.6 to 4 

percent). Seedling survival in these forests is initially low 

on the forest floor because of severe competition with 

mosses and herbs, and "nurse logs" serve as safe sites for 

early establishment. He noted, however, that long-term 

seedling survival on nurse logs is often low because of 

competition among seedlings and fragmentation of the 

wood substrate (Harmon 1989). In addition, unless the 

surviving tree saplings send roots down into the mineral 

soil, they are prone to toppling from logs. 

Professor, Department of Botany and Savannah River Ecology 

Laboratory, Institute of Ecology, University of Georgia, Drawer E, Aiken, 

SC 29803. 
Southeastem Forests 

Few studies have focused on the importance of woody 

debris to seedling regeneration in the forests of the 

Southeastern United States. Most reports of seedling 

recruitment on nurse logs or stumps are anecdotal. In a 

study of large woody debris in riparian zones of Southern 

Appalachian forests, Hedman (1 992) used seedling ages to 

estimate the minimum residence time of nurse logs. Of the 

six seedling species, the most common were Betula lenta 

and B. alleghaniensis (64 percent), as well as Tsuga spp. 

(25 percent). Other species were Magnolia fraseri, 

Liriodendron tulipifera, and Quercus spp. He noted that 

the abundance of Betula seedlings on CWD was not 

unexpected since these species are often found in canopy 

gaps in riparian systems. The most common species of 

nurse logs were Castanea dentata (39 percent) and Tsuga 

spp., both of which are relatively resistant to decay and 

therefore remain in place for long periods of time. 

Several current studies are examining seedling recruitment 

in sites of abundant CWD input following major 

Southeas tern winds toms. Myers and others (1 993) have 

measured CWD and regeneration layer vegetation on Pinus 

spp.-hardwood plots on the Santee Experimental Forest in 

the South Carolina Coastal Plain following Hurricane 

Hugo. Imm and McLeodl are comparing seedling 

regeneration following a tornado on timber-salvaged and 

unsalvaged bottomland hardwood plots on the Savannah 

River Site in South Carolina. Conner (1993) has reported 

very little natural regeneration of woody species during the 

first two growing seasons following Hurricane Hugo in 

low-lying forest areas on Hobcaw Barony, SC. He did note 

occasional establishment of Persea borbonia, Myrica 

cerifera, Lyonia lucida, and Acer rubrum on old stumps, 

baldcypress buttresses and knees, and other areas raised 

above the water. 

Elevated microsites formed by CWD may allow growth of 

certain plants and may be important in maintaining species 

diversity in swamps and wetland forests where the soil 

substrate of the forest floor is covered with water during all 

or a portion of the growing season. Roating log and stump 

communities in the Blue Girth Swamp of Alabama were 

described by Hall and Penfound (1943), who noted that 

they contained wetland and terrestrial plant species not 

found on the forest floor. In a study of the Santee Swamp 

Imm, Donald W. [and others]. 1994. Manuscript: Tornado induced 

changes in composition and successive differences during recovery due to 

treatment effects. Savannah River Ecology Laboratory, Aiken, SC. 

of South Carolina, Dennis and Batson (1974) listed eight 

woody species (among 24 total species) that were abundant 

on stumps and floating logs, and Irwin (1975) described 

similar communities on stumps in the Savannah River 

floodplain; A, rubrum was the most common woody 

seedling in both cases. It should be noted that the wood of 

baldcypress, Taxodium distichum, a common canopy tree in 

these Southeastern swamp forests, is relatively resistant to 

decay. Thus, some CWD probably persists for long periods 

in these wetland systems, 

Seedling Recruitment on CWD in 

Floodplain Forests 

Studies of woody seedling recruitment in riverine swamp 

systems have shown that CWD and microtopography 

associated with CWD provide sites for early seedling 

establishment (fig. 1). In a Taxodium distichum-Nyssa 

aquatica swamp on the floodplain of the Savannah River in 

South Carolina, Huenneke and Sharitz (1986) examined the 

distribution of woody seedlings across 16 distinct types of 

microsites, including forms of woody debris (stumps, logs, 

branches, and twigs), living wood (tree and shrub bases, 

baldcypress knees, mats of fine roots), sediment adjacent to 

dead or living woody substrates, and open sediment at low 

and higher elevations. They found seedlings of six trees (T. 

distichum, N. aquatica, Planera aquatica, A. rubrum, 

Fraxinus caroliniana, and Quercus spp.), two shrubs (Itea 

virginica and Cephalanthus occidentalis), and five woody 

vines (Smilax laurifolia, Vitis spp., Ampelopsis arborea, 

Uvln Sdl Elevated tow WOO! Near SOH Soil 

wood 

Figure I-Distribution of microsites and woody seedlings in f oodplain 

swamps in South Carolina and Florida. Coarse woody debris = logs, 

stumps, branches, and twigs; living wood = tree and shrub bases, 

baldcypress knees, and fine root mats; soil near wood = soil within 5 cm 

of woody debris or living wood; elevated soil is typically not submerged 

during growing season; low soil is typically submerged (Huenneke and 

Sharitz 1986; Titus 1990). 
Rhrcs radicans, and Berchemia scandens) growing on 

microsites that were elevated above the level of the 

surrounding forest floor. Approximately 75 percent of the 

woody seedlings occurred on woody debris, living wood 

substrates (especially root mats), or in soil adjacent to 

woody microsites (fig. 1). Given the low abundance of 

CWD, these decomposing wood microsites support a 

disproportionally large percentage of seedlings. The 

canopy dominant species, 7: distichum and N. aquatica, 

constituted approximately 32 percent of all woody 

seedlings. 

Similarly, in the broadleaf deciduous forest of the Welaka 

swamp on the St. Johns River floodplain in Florida, Titus 

(1990) examined the distribution of woody seedlings in 

relation to different microtopographic features. He also 

found that most seedlings occurred on elevated substrates; 

however, in contrast to the Savannah River swamp, raised 

soil areas that were rarely submerged provided microsites 

for more than 57 percent of the seedling recruitment (fig. 

I). Approximately 31 percent of the woody seedlings in the 

Welaka swamp occurred on woody debris, living wood 

substrates, or in soil adjacent to wood. The canopy 

dominant species, E caroliniana and Nyssa sylvatica var. 

biflora, accounted for only 3 percent of the seedlings; 

common species on CWD substrates were A, rubrum, 

Persea palustris, Sabal palmetto, and Vaccinium elliotti. 

To compare seedling-microsite associations between 

locations, distribution indices (DI) were calculated to 

express a species' occurrence on a given microsite type, 

weighted by the abundance of that microsite (table 1). In 

general, larger or more stable forms of CWD (stumps and 

logs) supported proportionally greater numbers of 

seedlings (DI values greater than 1.0), whereas smaller 

debris (branches and twigs) supported proportionally fewer 

(DI less than 1.0). Woody seedlings in both swamps 

showed stronger association with stumps than with any 

other form of CWD. The higher DI values for woody 

species in general than for the canopy dominants on stumps 

and logs in the Savannah River swamp suggest that these 

CWD substrates may be important in maintaining species 

richness in this system. Interestingly, few seedlings of the 

canopy dominants grew on soil adjacent to large woody 

debris in the Savannah River swamp, although such 

microsites were far more significant for seedling 

Table 1 - Distribution index (DI*) values for selected tree species on coarse woody 

debris and related microsites in two Southeastern swamps 

Microsite All' Taxodium ' Nyssa ' Ace3 Quercus2 

species distichum aquatica rubrum laurifalia 

Coarse woody debris 

Stump 17.0 6.1 2.3 3.8 1.3 

Log 7.7 5.5 0.7 1.5 1 .O 

Branch 1.1 1.1 0.2 0.1 0.0 

Twig 0.0 0.2 0.1 0.1 1.8 

Soil near wood 

Near stump 0.5 0.0 0.8 2.7 0.0 

Near log 0.5 0.0 0.8 0.3 1.1 

Near branch 0.2 0.0 0.5 4.2 5.2 

Near tree 1.7 2.5 2.9 2.8 4.3 

Near knee 5.8 11.9 10.7 18.0 0.0 

* DI = (percent seedlings on a microsite)/(percent area covered by microsite). 

"avannah River swamp, SC (Huenneke and Sharitz 1986). 

Welaka swamp, FL (Titus 1990). 
recruitment in the Welaka swamp. In both systems, 

seedlings also were strongly associated with elevated soil 

surrounding clusters of baldcypress knees (highest DI 

values) and with soil adjacent to tree bases (table I). 

Elevation above the water and physical stability are two 

features of these microsites that are critical to their function 

as safe sites for seedling establishment. The Savannah 

River swamp is a deep-water system with high-energy 

floods typically occurring during winter months that may 

erode sediment adjacent to woody structures, whereas the 

Welaka swamp is a relatively low-energy, shallow-water 

system. Areas of unflooded soil are more common in the 

Welaka swamp and provide the most favorable substrate for 

seed germination and the rooting of seedlings; unflooded 

soil is not common during the growing season in the 

Savannah River swamp. 

Differences in seedling densities among microsite types in 

swamps may arise in several ways. First, different densities 

of seeds may be dispersed to or be trapped by different 

microsites. In swamps, the seeds of many species are 

dispersed by water (hydrochory) during periods of 

inundation, and the process of seed trapping and retention 

may be particularly important. Schneider and Sharitz 

(1988) found that seeds of I: distichum and fruits of N. 

aguatica were trapped chiefly by logs and knees (fig. 2); 

very few water-dispersed seeds remained in open areas not 

associated with emergent substrates. Similarly, seeds were 

retained and incorporated into the sediment (seed bank) 

primarily adjacent to logs, knees, and the bases of trees. 

Second, gemination percentages may differ in the 

environments of different substrates. For example, both I: 

distichum and N; aquatica are known to require aerated 

sites not covered by standing water for gemination 

(Demaree 1932; Shunk 1939). In a deep-water swamp, the 

importance of emergent microsites may lie chiefly in 

providing gemination and seedling establishment sites 

above summer water levels. Third, seedling survival and 

growth rates undoubtedly differ among microsites. Rotting 

wood has lower concentrations of the nutrients required for 

plant growth than most mineral and organic soils (Harmon 

and others 1986), thus growth can be slower on woody 

rnicrosites than on elevated soil microsites. Nevertheless, 

erosion may limit seedling survival on soil substrates, 

especially during high-energy floods. 

Stability of the rooting medium is a major component of 

microsite suitability for swamp tree seedlings. Huenneke 

and Sharitz (1990) examined the physical properties of 

several swamp substrate types and their influence on N. 

*Seed bank not sampled Microsites 

Seeds Trapped 

Seed Bank 

50 Seedlings 

Stum Log Branch Twi Tree Knee 

(+Ns~ (+NL) (+NB) (+N+W) (+NTr) (+NK) 

Figure 2-Distribution of Taxodium distichum and Nyssa aquatica seeds 

and seedlings on woody microsites (debris and living wood) in a 

floodplain swamp in South Carolina. Values for each woody microsite 

include seeds or seedlings in soil within 5 cm of the woody structure 

(e.g., +NS = near stump) (Schneider and Sharitz 1988). 

aquatica performance in the Savannah River floodplain. 

They focused on the stability of the rooting zone and the 

relative permanence of various substrate types over a winter 

flood period. No trees or live knees disappeared during the 

floods and only one dead stump (out of 22) was lost despite 

the small size and/or advanced state of decomposition of 

some stumps. Approximately 10 percent of the logs were 

completely lost from the study site, and 80 percent had 

moved downstream or showed signs of having moved or 

shifted position; small branches and twigs were quite 

impemanent. It is therefore not surprising that the highest 

numbers of N. aquatica seedlings occurred in association 

with the more permanent sites of knees and tree bases (fig. 

2) and stumps (table I). 

Emergent CWD microsites may play a role in maintaining 

woody species diversity in areas that typically are under 

water during all or a portion of the growing season. In the 

Congaree Swamp in South Carolina, Putz and Sharitz 

(199 1) observed that CWD microsites enabled less floodtolerant species such as Liquidambar styraciflua and A. 

rubrum to become established and persist in deep-water 

Taxodium-Nyssa sloughs, thus increasing the species 

richness of the forest. Similarly, Dennis and Batson (1974) 

noted the diversity of woody seedling species on stumps 

and floating logs in the Santee Swamp. The long-term 

importance of these sites to recruitment of canopy species 
is less certain. Most CWD may be poor substrates for longterm seedling survival and growth. Trees that show rooting 

patterns indicative of having become established on wood 

that later decayed are commonly seen in Southeastem 

swamp forests, but they account for a small percentage of 

the overall stems. Furthermore, such root systems may be 

less stable than nomally formed roots, and these trees may 

be more susceptible to uprooting. For example, following 

Hurricane Hugo, Putz and Sharitz (1991) noted that trees 

that had rooted on decaying stumps and logs in deep-water 

areas of the Congaree swamp were more likely to have 

been uprooted than were trees rooted directly in the 

sediment. 

Even in deep-water Taxodium-Nyssa forests, natural 

variations in water level, especially prolonged periods of 

low water during the growing season that expose the soil on 

the forest floor, appear to be required for successful 

regeneration of the forest canopy trees. In most mixed 

bottomland forests along river floodplains of the Southeast, 

seedlings and small saplings (advance regeneration) occur 

on the forest floor across a variety of microsites. In such 

forests that are not flooded for prolonged periods during the 

growing season, small differences in elevation may be 

correlated with germination and survival of different 

species (Jones and others 1994) and woody debris may be 

most important in contributing to the overall environmental 

heterogeneity of the site, rather than serving as an 

important substrate for recruitment. 

Conclusions 

The role of CWD in Southeastern forests may have 

received less attention than in other parts of the country for 

several reasons. Most of the original forests of the 

Southeast were logged in the 1700's and 1800's, and few 

natural stands of large trees remain today; this is especially 

true in the Piedmont. In the moist temperate climate of the 

Southeast, wood decomposition occurs rapidly and many of 

the native tree species are not especially decay-resistant. 

Furthermore, forest management techniques that have been 

used historically throughout this region have seldom 

resulted in significant amounts of CWD scattered across the 

forest floor. Although approaches to forest management 

that consider ecological principles are being adopted in the 

Southeast (Sharitz and others 1992), and awareness of the 

potential value of CWD is increasing, there may typically 

be less rotting wood in Southeastern forests than in forests 

elsewhere. 

The importance of woody debris to regeneration in 

Southeastern forests is not known, although studies have 

documented the occurrence of woody seedlings on CWD, 

especially in wetland forests. Woody debris may be 

important in building up structure and sediment to form 

microsites that are not flooded; this is especially likely in 

wetland systems with low-energy flood waters and less 

erosive force. The increased heterogeneity and availability 

of substrates on the forest floor, interacting with increased 

light in canopy gaps, no doubt provides an array of 

regeneration niches for different species and may increase 

the overall richness of the forest community. Even if 

seedlings are not rooted directly on the CWD, this material 

influences microenvironmental conditions such as light, 

moisture, and nutrient availability and results in a greater 

array of microsites. Further study of seedling 

establishment, survival, and growth to reproductive 

maturity in forests with woody debris left intact is needed 

to evaluate the ecological significance of CWD in the 

regeneration of Southeastern forests. 

Acknowledgments 

This work was supported by contract DE-AC09-76SR00- 

819 between the U.S. Department of Energy and the 

University of Georgia's Savannah River Ecology 

Laboratory. I thank L.L. Battaglia for valuable technical 

review of the manuscript. 
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Diversity of Lignicolous Basidiomycetes 

in Coarse Woody Debris 

Karen K. Nakasone 

Abstract 

Basidiomycetes are the most conspicuous fungi on wood and are the main 

decomposers. Lignicolous basidiomycetes include white-rotters that 

remove both lignin and cellulose, and brown-rotters that remove only the 

cellulose and hemicellulose. The South is a region of diverse Iignicolous 

basidiomycetes because it is the northern limit for many tropical and 

subtropical taxa and the southern limit for many north temperate taxa. 

Niches for various taxa are defined by host, substrate, size, and degree of 

decay. Hence, diversity of these fungi can be enhanced by a mixture 

of woody angiosperm and gymnosperm debris of different decay and 

size classes. 

Introduction 

Southern forests support a species-rich flora of lignicolous 

fungi. This diversity has its basis in the favorable climatic 

conditions of the region and the variety of woody plant 

hosts. The warm temperatures and abundant precipitation 

are ideal conditions for many species of fungi. Most 

filamentous fungi that inhabit woody debris are 

ascomycetes, deuteromycetes, and basidiomycetes. This 

discussion will be limited to basidiomycetes, which are the 

most conspicuous fungi on wood and are the major 

decomposers. 

Lignicolous basidiomycetes are divided into two groups 

based on the type of decay they cause. Fungi that remove 

both the lignin and cellulose from wood are called 

white-rotters. The decayed wood is often bleached, with a 

spongy or stringy texture. Most lignicolous basidiomycetes 

are associated with a white-rot decay. Fungi that selectively 

remove the cellulose and hemicellulose, leaving the lignin 

behind, are referred to as brown-rotters. The woody 

residues are characteristically dark brown and crumbly, and 

fall apart in cubes. Only about 6 percent of lignicolous 

basidiomycetes are known to be associated with brown-rot 

decay (Gilbertson 1980). There are at least 125 species of 

brown-rot basidiomycetes, which are classified in four 

orders: Aphyllophorales (Corticiaceae, Coniophoraceae, 

Fistulinaceae, Polyporaceae), Agaricales, Tremelldes, and 

Dacrymycetales. A majority of the brown-rot species (70 

percent) are members of the Polyporaceae (Gilbertson 

Botanist, Center for Mycology Research, Forest Products Laboratory, U.S. 

Department of Agriculture, Forest Service, One Gifford Pinchot Drive, 

Madison, VVS 53705-2398. 

198 1). About 85 percent of brown-rot fungi are associated 

with gymnospermous hosts (Gilbertson 1980; Nobles 

1958). In some regions, cubical brown-rot residues are the 

major component in the soils (Harvey and others 1976a; 

McFee and Stone 1966) and the primary site of 

ectomyconkzal root development (Harvey and others 1976b). 

The Southern United States hosts the most diverse mycota 

of lignicolous basidiomycetes in the country. This area is 

the northern limit for many tropical and subtropical 

lignicolous basidiomycetes such as Aleurodiscus mirabilis 

and Gloeodontia discolor. Similarly, many north temperate 

species have their most southern distribution in the 

southeast; Veluticeps ambigua and Phlebia acerina are 

examples. Other taxa, such as fnonotus lucEbviciaaus and 

Resinicium meridionalis are endemic to the Southern 

United States. In the last 13 years, a number of new species 

of lignicolous basidiomycetes have been described from 

this region (Adaskaveg and Gilbertson 1988; Burdsall and 

Nakasone 198 1, 1983; Burdsall and others 198 1 ; Gilbertson 

and Blackwell 1984, 1985, 1987, 1988; Larsen and 

Nakasone 1984; Nakasone 1983, 1984). Nevertheless, the 

lignicolous mycota of the Southern United States is still 

poorly known, and many new species are yet to be 

described. 

Host and substrate are important biotic factors that 

contribute to diversity of fungi on wood. Most species of 

lignicolous fungi are somewhat host specific. For example, 

Aleurodiscus mirabilis is found on branches of 

rhododendron, where as Phlebia hydnoidea typically occurs 

on American chestnut and occasionally on oak. Other 

species are found exclusively or preferentially on 

gymnospermous or angiospermous hosts. Auriculariopsis 

albomellea and most Resinicium species, for example, 

prefer gymnospermous hosts, whereas I! albida and most 

Stereurn species occur on woody angiosperms. Other 

species are omnivorous and have no host preference; 

Phanerochaete chrysorhizon and Subulicystidium 

longisporum are examples of these taxa. 

Fungi often display preferences in substrates. Some species 

colonize only live plants and may be pathogenic or 

nonpathogenic. Although species such as Amillaria 

tabeseens and Heterobasidion annosum are aggressive 

pathogens, many other species are nonpathogenic on living 

tissue. For example, nonpathogenic fungal endophytes that 
colonize living limbs are also the first ones to decay the 

dead limbs (Chapela 1989; Chapela and Boddy 1988). Most 

endophytes are ascomycetes or deuteromycetes. Some 

basidiomycetes, such as Dendrothele, fruit only on bark of 

living trees. Other species, such as A. mirabilis and 

Dendrophora versilfbrmis, fruit primarily on bark of dead 

branches. Decorticated wood is the preferred substrate for 

some taxa; however, most species are found on bark and 

woody tissue. Species of Resinicium fruit on decorticated 

wood, but Phlebiella vaga and Phlebia chrysocreas, 

common and widely distributed species, develop sporocarps 

on bark and wood. 

The size of the substrate is also important. Typically, large 

fruiting bodies are associated with logs, stumps, and snags. 

For example, Laetiporus sulphureus develops fruiting 

bodies on logs and stumps, and Armillaria tabescens is 

associated with stumps and roots of trees. Other species are 

specific to branches and twigs. Stereum striatum is 

frequently found on small-diameter twigs and branches of 

Carpinus. 

The degree of decay of the woody substrate can also 

influence fungal diversity. Some lignicolous fungi are 

associated only with well-rotted wood. These are often 

fragile or ephemereal species such as Trechispora 

farinacea. Amphinema byssoides and other mycorrhizal 

corticioid species also develop fruiting bodies on 

well-rotted wood. In contrast, Cryptoporus volvatus 

commonly fruits within a year after death of its conifer tree 

host before being replaced by other lignicolous fungi 

(Gilbertson and Ryvarden 1986). 

Some lignicolous fungi also prey on nematodes that inhabit 

wood. Because nitrogen is in limited supply in woody 

substrates, many species use nematodes and microbes as 

nitrogen sources. These fungi have developed several 

mechanisms to capture nematodes (Thorn and Bmon 

1984). Specialized cells called stephanocysts produced in 

some species of Hyphodem become attached to the 

nematodes and eventually invade the host (Liou and Tzean 

1992). Species of Hoehnbuehelia produce adhesive cells to 

catch their prey whereas Pleurotus ostreatus produces a 

toxin that inactivates nematodes. Pleurotus ostreatus and 

other species of lignicolous fungi also utilize bacteria as a 

nutrient source (Barron 1988; Blanchette and Shaw 1978). 

To examine the diversity of lignicolous fungi in more 

detail, species associated with sweetgum (Liquidambar 

styracipua L.) and loblolly pine (Pinus taeda L.) will be 

considered. A list of lignicolous basidiomycetes recorded 

on these hosts is shown in the appendix. Most records were 

taken from Fungi on Plants and Plant Products (Farr and 

others 1989); other records are from the Forest Products 

Laboratory. The list is not exhaustive. At least 73 species of 

lignicolous basidiomycetes are associated with loblolly 

pine and 120 species with sweetgum, compared to 228 

species reported for ponderosa pine (Gilbertson 1974) and 

260 for aspen (Lindsey and Gilbertson 1978). The taxa are 

distributed in five orders, with most species classified in the 

order Aphyllophordes (table 1). Within the Aphyllophordes, 

the majority of species are classified into two families: the 

Corticiaceae, which consist of many white-spored genera 

that have a primarily resupinate habit, and the Polyporaceae, 

which include most of the poroid genera. Fifty-two and 80 

genera have been reported on loblolly pine and sweetgum, 

respectively, representing a total of 103 different genera. A 

few genera are represented by four or more species: 

Pleurotus, Hyphoderma, Phanerochaete, Phlebia, 

Phellinus, and Stereum. 

Table 1-Distribution of lignicolous basidiomycetes on 

loblolly pine and sweetgum by order 

Order Loblolly pine S weetgum 

Agaricales 

Aphyllophorales 

Corticiaceae 

Hymenochaetaceae 

Lachnocladiaceae 

Polyporaceae 

S tereaceae 

All other families 

Auriculariales 

Dacrymycetales 

Tremellales 

Table 2-Lignicolous basidiomycetes common to both 

sweetgum and loblolly pine 

Amillaria tabescens 

Auricularia auricula 

Dacryopinax spathularia 

Diplomitoporus overholtsii 

Gloeophyllum sepiarium 

Hyphodema praetermissum 

Hyphodema puberum 

Hyphodema setigerum 

hitextum bicolor 

Nigroporus vinosus 

Phanerochaete burtii 

Phanerochaete chrysorhizon 

Phanerochaete Jlavido-alba 

Phlebiella vaga 

Schizophyllum commune 

Subulicystidium longisporum 
No representatives of the Stereaceae have been reported on 

loblolly pine. In North America, Stereum, a common and 

widespread genus, occurs primarily on angiospemous 

hosts; Stereum sanguinolentum is the only species that 

occurs on conifers, but it has not been recorded on loblolly 

pine. Similarly, most species in the Hymenochaetaceae and 

Lachnocladiaceae are associated with angiospermous hosts. 

Of the 193 taxa reported on both sweetgum and loblolly 

pine, only 16 species (9 percent) are common to both hosts 

(table 2). Most of these taxa are common and widely 

distributed throughout North America. Five species of 

brown-rot fungi have been reported on sweetgum compared 

to 14 species on loblolly pine (table 3). This represents 

Table 3-Brown-rot decay fungi on loblolly pine and 

sweetgum 

Loblolly pine Sweetgum 

Antrodia radiculosa Dacrymyces minor 

Antrodia serialis Dacryopinax spathula ria 

Antrodia xantha Fomitopsis spraguei 

Coniophora olivascens Gloeophyllum sepiarium 

Dacrymyces stillatus Gloeophyllum trabeum 

Dacryopinax spathularia 

Fomitopsis palustris 

Gloeophyllum carbonarium 

Gloeophyllum sepiarium 

Laetiporus persicinus 

Phaeolus schweinitzii 

Postia caesia 

Postia guttulata 

Wolfiporia COCOS 

Table &Sibling fungal species on loblolly pine and 

sweetgum 

Loblolly pine Sweetgum 

Dacrymyces stillatus 

Inonotus circinatus 

Ganodema meredithae 

Junghuhnia luteoalba 

Meruliopsis ambiguus 

Peniophora pini subsp. dup lex 

Perenniporia subacida 

Scytinostroma galactinum 

Dacrymyces minor 

Inotzotus ludovicianus 

Ganodema lucidum 

Junghuhnia nitida 

Meruliopsis corium 

Peniophora violaceolivida 

Perenniporia tenuis 

Scytinostroma protrusum 

about 4 percent and 19 percent, respectively, of all the fungi 

reported from these hosts. These values are similar to that 

found for other gymnospermous and angiospemous hosts 

(Gilbertson 1980, 1981). 

Several sibling species occur on loblolly pine and 

sweetgum (table 4). These species are morphologically 

similar and often share a similar habit, but one taxon occurs 

primarily or exclusively on angiospemous wood whereas 

the other prefers gymnospermous wood. For example, fruit 

bodies of Scytinostroma galactinum and S. protrusum are 

morphologically identical but can be distinguished by 

isozymes and cultural morphology (Nakasone and Micales 

1988). In addition, S. galactinum occurs exclusively on 

gymnosperms, whereas S. protrusum is known only on 

woody angiosperms. 

Accurate totals of species of lignicolous fungi have become 

available only recently. Ginns and Lefebvre (1993) 

included 1,163 species of lignicolous, corticioid 

basidiomycetes (including the jelly fungi) from Canada and 

the United States. Gilbertson and Ryvarden (1986-87) 

described 4 1 1 species of polypores from North America. 

Added to the approximately 620 species of Agaricales 

(Gilbertson 1980) that occur on wood, the total number of 

lignicolous basidiomycetes reported from North America is 

2,194. Therefore, the 177 unique species on sweetgum and 

loblolly pine represent 8.1 percent of the total mycota of 

lignicolous basidiomycetes from North America. 

As an example of the potential diversity in the Southern 

United States, we can examine the fungi reported from 

different habitats and hosts from this region. Jung (1987) 

described 130 species of wood-rotting Aphyllophorales 

from the spruce fir forest of the Southern Appalachians. 

Only 38 species (29 percent) are also reported on sweetgum 

and loblolly pine; 92 species (7 1 percent), representing 25 

genera, are not reported. Similarly, Gilbertson and 

Blackwell (1985, 1987) described 5 1 taxa of lignicolous 

fungi on juniper in the Gulf Coast region, of which 41 

species do not occur on loblolly pine or sweetgum, or in the 

spruce fir forest. 

These examples can be used to obtain a rough estimate of 

the number of species of lignicolous basidiomycetes that 

occur in the Southern United States. A total of 300 

different lignicolous species are reported on loblolly pine, 

sweetgum, and juniper, and from the spruce fir forest 

region. A conservative estimate for this region is 600 

species; an optimistic estimate is 1,000 species. It is 

important to remember that this entire discussion has 

focused on fungi that produce fruiting bodies. There are 
probably many species living in woody tissue that rarely or 

never produce fmiting bodies because the environmental 

conditions are not optimal. AIthough many of these species 

can be cultured, they often cannot be identified. Thus, by 

relying on sporocarps to evaluate fungal diversity, we are 

sampling just a part of the mycota. 

In summary, the diversity of lignicolous basidiomycetes in 

the southern forests is directly related to the quality and 

quantity of the coarse woody debris. Diversity of these 

fungi can be enhanced by a mixture of woody angiosperm 

and gymnosperm debris of different decay and size classes. 

Acknowledgments 

I gratefully acknowledge Drs. Robert Gilbertson and 

Harold Burdsall, Jr., who shared their extensive knowledge 

of the lignicolous basidiomycetes, and Dr. R. Greg Thorn, 

who generously loaned slides and provided helpful 

comments. 

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Appendix 

Basidiomycetes that decay loblolly pine and sweetguma 

Genera 

Order Family Loblolly pine Sweetgum 

Agaricales 

Aphyllophorales Auriscalpiaceae 

Clavariaceae 

Coniophoraceae 

Corticiaceae 

Amillaria tabescens 

Hohenbuehelia pinacearum 

Pholiota spumosa 

Phyllotopsis nidulans 

Tricholomopsis rutilans 

Coniophora olivascens 

* Amphinema byssoides 

* Chaetoporellus latitans 

* Confertobasidium olivaceo-album 

Grandinia arguta 

* Grandinia barbajovis 

* Grandinia pallidula 

* Hyphoderma pallidum 

* Hyphoderma praetemissum 

* Hyphoderma puberum 

* Hyphoderm sambuci 

Hyphodema setigerum 

Hyphodontia arguta 

* Hyphodontia barbajovis 

* Hyphodontia pallidula 

kitextum bicolor 

Meruliopsis ambiguus 

M'eruliopsis taxicola 

Peniophora pini subsp. duplex 

Phanerochaete burtii 

Phanerochaete chrysorhiza 

* Phanerochaete flavido-alba 

Amillaria mellea 

Amillaria tabescens 

Coprinus disseminatus 

Gymnophilus amillatus 

Gymnophilus praefloccosus 

Lentinellus ursinus 

Lentinus strigosus 

Lentinus tigrinus 

Oudemnsiella canarii 

Panellus pusillus 

* Pholiota limonella 

Pleurotus cystidiosus 

Pleurotus dryinus 

Pleurotus levis 

Pleurotus ostreatus 

Simocybe ataomacea 

Volvariella bombycina 

Gloeodontia discolor 

Clavicorona pyxidata 

* Botryobasidium vagum 

Candelabrochaete langlosii 

Cylindrobasidium laeve 

* Dendrophora versiformis 

Dendrothele microspora 

Dendrothele strumosa 

Gloeocystidiellum porosum 

Gloeocystidiellum turpe 

Gloeoporus dichrous 

Hyphodema mutatum 

* Hjiphoderma praetemissum 

* Hyphodema puberum 

Hyphoderma rimosum 

Hyphodema setigerum 

* Meruilopsis corium 

* Peniophora violaceo-livida 

Phanerochaete burtii 

Phanerochaete chvsorhiza 

Phanerochaete crassa 

Phanerochaete flavido-alba 

Phanerochaete velutina 
Basidiornycetes that decay loblolly pine and sweetguma (continued) 

Genera 

Order Family Loblolly pine Sweetgum 

* Phanerochaete gigantea 

Phanerochaete sordida 

Phlebiella vaga 

Pseudomerulius curtisii 

* Resinicium bicolor 

* Resinicium fufuraceum 

Resinicium meridionale 

Scytinostromella fallax 

* Subulicystidium longisporum 

Ganodermataceae Ganoderma meredithad 

Hericiaceae 

Hydnaceae Mycorrhaphium adustum 

Hyrnenochaetaceae Hymenochaete pinnatiJida 

Inonotus circinatus 

Phellinus pini 

Phellinus viticola 

Lachnocladiaceae Dichostereum pallescens 

Scytinostroma galactinum 

Pol yporaceae * Antrodia radiculosa 

Antrodia serialis 

* Antrodia xantha 

* Ceriporia tar& 

Coriolopsis gallica 

Cryptoporus volvatus 

Dichomitus squalens 

* Diplomitoporus overholtsii 

Fomitopsis palustris 

* Gloeophyllum carbonarium 

Gloeophyllum sepiarium 

Heterobasidion annosum 

Junghuhnia luteoalba 

* hetiporus persicinus 

Phlebia chrysocreas 

Phlebia ludoviciana 

* Phlebia radiata 

Phlebia setulosa 

* Phlebiella vaga 

* Pulcherricium caeruleum 

* Schizopora Jlavipora 

* Schizopora paradoxa 

* Subulicystidium longisporum 

* Trechispora farinacea 

* Trechispora regularis 

* Xenasmatella tulasnelloidea 

Ganoderma lucidum 

Hericium erinaceus 

Laxitextum bicolor 

Climacodon pulcherrimus 

Climacodon septentrionalis 

Hymenochaete agglutinans 

Inonotus ludovicianus 

* Inonotus rickii 

Phellinus conchatus 

Phellinus ferruginosus 

Phellinus gilvus 

Phellinus laevigatus 

Phellinus melleoporus 

* Asterostroma cewicolor 

* Dichostereum sordulentum 

* Scytinostroma protrusum 

* Vararia sphaericospora 

Bjerkandera adusta 

Ceriporia xylostromatoides 

* Ceriporiopsis pannocincta 

Cerrena unicolor 

Coriolopsis rig ida 

Daedaleopsis confragosa 

* Diplomitoporus overholtsii 

Fomes fasciatus 

Fbmitella supiea 

Fomitopsis spraguei 

Gloeophyllum sepiarium 

Gloeophyllum trabeum 

* Heteropoms biennis 

Hexagonia hydnoides 
Basidiomycetes that decay loblolly pine and sweetguma (continued) 

Order Family 

Genera 

Loblolly pine S weetgum 

Meripilus sumstinei 

Nigroporus vinosus 

Perenniporia subacida 

Phaeolus schweinitzii 

Postia caesia 

Postia guttulata 

Skeletocutis amorpha 

Skeletocutis nivea 

Trichaptum abietinum 

Tyromyces chinoeus 

WolJiporia cocas 

Steccherinaceae 

Stereaceae 

Schizophyllaceae 

Thelephoraceae 

Auriculariales 

Dacry m ycetales 

Schizophyllum commune 

Tomentella ferruginea 

* Auricularia auricula 

* Cerinomyces pallidus 

Dacrymyces chrysospemus 

Dacrymyces stillatus 

Dacryopinax spathularia 

Junghuhnia nitida 

Lenzites betulina 

Nigroporus vinosus 

Oxyporus latemarginatus 

* Perenniporia compacta 

* Perenniporia tenuis 

Polyporus arcularius 

Pycnoporus cinnabarinus 

Pycnoporus sanguineus 

Rigidoporus lineatus 

Rigidoporus ulmarius 

Tinctoporellus epimiltinus 

Trametes hirsuta 

Trametes subectypus 

Trametes versicolor 

Trichaptum biforme 

Trichaptum sector 

* Tyromyces fissilis 

Tyromyces galactinus 

* Wrightoporia avellanea 

Steccherinum ochraceum 

* Steccherinum subrawakense 

Stereum hirsutum 

Stereum ochraceo-Pavum 

Stereum ostrea 

Stereum striatum 

Xjllobolus subpileatus 

Schizophyllum commune 

Auricularia auricula 

Auricula ria cornea 

* Dac~myces minor 

Dacryopinax spathula ria 

Exidia recisa 

* Heterochaete shearii 

Tremella mesenterica 

"Species listed in Farr and others (1989). Those with an asterisk (*) are from records in Center for Forest Mycology Research, 

Forest Products Laboratory. 

Obtained from Adaskaveg and Cilbertson (1988). I 
Earthworms, Biodiversity, and Coarse Woody Debris 

in Forest Ecosystems of the Southeastern U.S.A. 

Paul F. Hendrix 

Abstract Background 

Few studies have been conducted in the Southeast, or elsewhere, on 

earthworms and coarse woody debris (CWD). Species of potentiai 

importance to CWD in Southeastern forests include several native and 

introduced lumbricids and an introduced Asian megascolecid. 

Earthworms may use CWD as a refuge and a resource while enhancing 

decomposition, primarily at the secondary phase of colonization. After 

channelization by other organisms, earthworms may contribute to decay 

through transport of soil, nutrients, and microbes into wood. Selective 

feeding on fungal hyphae may also be important. Maximum earthworm 

diversity in CWD may occur during the secondary colonization and 

maceration phases of decomposition. Knowledge is lacking in 

systematics, processes, and the influence of management practices. 

Introduction 

Interest in biodiversity arises from several motivations. 

These include (1) a sense of intrinsic value in the existence 

of a variety of species, (2) known or expected practical 

values of species or products derived from them, and (3) 

knowledge or hypotheses that many species in an ecosystem 

participate in processes important to ecosystem function. 

This latter motivation is a central issue in modem ecology 

and is likely to be an important component of emerging 

ecosystem management strategies. The premise of this 

paper is that the diverse assemblages of earthworms present 

in many soils influence soil processes and, by extension, 

may also influence coarse woody debris (0) dynamics 

in forest ecosystems. 

Despite the voluminous literature on earthworm biology and 

ecology, surprisingly few studies have examined interactions between earthwoms and CWD. Few of these apply 

directly to the Southeast. This paper considers selected 

literature relevant to CW and earthworms, presents some 

intepretations and hypotheses about interactions between 

earthworms and CW, and identifies areas for further 

research. 

Asswiate Professor of Ecology and Crop and Soil Science, Institute of 

Ekology and Department of Crop and Soil Sciences, University of 

Georgia, Athens, GA 30602. 

Eafihworm Systematics and Biogeography 

Earthworms belong to the class Oligochaeta, which consists 

of some 20 families worldwide (Reynolds and Cook 1993). 

Three of these families include aquatic or semi-aquatic 

worms. Most of the other families consist of terrestrial 

forms, many of which are of possible significance in forest 

ecosystems. Two families (Kom~ekionidae and 

Lutodrilidae, both monotypic) and genera from three others 

(Lumbricidae, Sparganophilidae, and Megascolecidae) are 

native to North America (table 1). James (1995) suggests 

that endemic representatives of the Ocnerodrilidae may also 

inhabit isolated areas of the United States. 

Pleistocene glaciations, the most recent of which ended 

approximately 10,000 years BP, are thought to have 

eliminated the earthworm fauna from Canada and most of 

the northern portion of the Continental United States (Gates 

1970). Glacial refugia apparently remained in the Pacific 

Northwest, where a number of native genera in the family 

Megascolecidae now occur (Fender 1995; Fender and 

McKey-Fender 1990), and in the Southeastern United States 

where all of the other nearctic groups occur (Gates 1982; 

James 1995). As many as 100 species of earthworms may 

occur in the Southeast, with perhaps 10 or more associated 

with CVVD at some stage of decompsition (table 2). Thus, 

the Southeast has a rich and diverse earthworm fauna, 

probably reaching its highest biodiversity and greatest 

potential impacts on soil processes in forest ecosystems 

throughout the region (Dotson and Kalisz 1989; hndrix 

and others 1994; Reynolds 1972, 19476, 1995). 

In addition to the native fauna, species from several of the 

other earthworm families listed in table 1 have been 

introduced into North America over the past 500 years. 

Species of the Lumbricidae and Megascole~idae have been 

particularfy successful in the Southeast and can now be 

found in many areas affected by human habitation, 

agriculture, and fishing. 

Ecological Considerations 

Competitive exclusion of native earthworm by exotic 

earthworm species has been postulated, but little direct 

evidence of this can be found. Kalisz and Wood (1995) 

suggest four stages in the establishment of exotic earthworm 
Table 1-Partial listing of oligochaete classification and 

geographic origins of earthwom families (compiled from 

Bouche 1983; Reynolds and Cook 1993; Wallwork 1983) 

Phylum: Annelida 

Class: Oligochaeta 

Order: Haplotaxida 

Suborder: Lumbricina 

Family: Lumbricidae 

Komarekionidae 

Sparganophilidae 

Lutodrilidae 

Megascolecidae 

Glossoscolecidae 

Eudrilidae 

Acanthodrilidae 

Octochaetidae 

Ocnerodrilidae 

Ailoscolecidae 

Hormogastridae 

Kynotidae 

Microchaetidae 

Almidae 

NH-NA,EU 

NH-NA 

NH-NA,EU 

NH-NA 

NH,SHNA,OC,AS 

SH-SA 

SH-AF 

SH-AS 

SH4C 

SH-SA, 

AF,AS,MA 

NH-EU 

NH-ME 

SH-MA 

SH-AF 

SH-SA, 

AF,AS 

NH = northern hemisphere, SH = southern hemisphere, 

NA = North America, SA = South America, EU = Europe, 

OC = Oceania, AS = Asia, AF = Africa, 

ME = Mediteranean, MA = Madagascar. 

populations: (1) habitat disturbance, (2) extirpation or 

reduction of native populations, (3) introduction of exotic 

species, and (4) colonization of vacant niche space by exotic 

species. The principal mechanism of displacement of native 

populations thus appears to be habitat alteration rather than 

direct competition. All-native, all-exotic, and mixed 

comunities of earthworms can be found in forest 

ecosystems in the Southeast, depending on extent of habitat 

disturbance or human activity. For example, riparian forests 

are prime areas for establishment of exotics used as fish bait 

(Callaham and Hendrix, in press), while at least some 

remote or uncultivated areas still maintain pure native 

etlrthwom comunities (Dotson and Kalisz 1989; Hendrix 

and others 1994). 

Table 2-Some earthwom genera and species that may use 

coarse woody debris in southeastern forest ecosystems 1 

I 

I 

Species Reference 

I 

Bimastos parvus 

(Eisen, 1874) Boettcher and Kalisz (199 1) 

Bimastos zeteki 

(Smith & Gittins, 1915) Murchie (1960) 

Bimastos sp. Ausmus (1977) ! 

Eisenoides carolinensis 

(Michaelsen, 19 10) Boettcher and Kalisz (199 1) 

Dendrobaena octaedra 

(Savigny, 1826) Gates (1982) 

Dendrodrilus rubida 

(Savigny, 1826) Murchie ( 1960) 

Octolasion sp. Ausmus (1977) 

Lurnbricus rubellus 

(Hoffmeister 1845) Personal observation 

Amynthas spp. Personal observation 

Life history and adaptations of earthworm species present in 

a given area probably determine their influence on soil 

processes, including CWD dynamics. Several classification 

schemes for ecological strategies have been devised, based 

on earthworm feeding activities and mode of existence in 

the soil. The most widely used scheme (Bouch6 1977) 

recognizes (1) epigeic species, which inhabit surface litter 

and humus horizons; (2) endogeic species, which occupy 

and consume mineral soil; and (3) anecic species, which 

form vertical burrows in which they live and into which they 

pull surface litter for food. Some overlap among these 

categories appears to occur for some species. In any 

particular ecosystem, species representing all three 

ecological strategies may occur (Lee 1985). Epigeic and 

endogeic forms may be the most important at various stages 

in the decay of CWD. 

Species of potential importance to CVVD in southeastern 

forests include several native and introduced lumbricids and 

an introduced Asian megascolecid (table 2). Most of these 

earthworms have epigeic feeding strategies, are polyhumic 

and pigmented, and have been reported from logs, branches, 

andfor litter layers of forest soils. The exception, 

Octolasion sp., is endogeic but has been reported in rotting 

logs (Ausmus 1977). 
It might be argued that native species are better adapted to 

climate, soil, and vegetation in Southeastern forests and 

therefore may be more important to ecosystem processes 

than are exotics. Some evidence exists to support this 

hypothesis, from studies of mixed native and exotic 

earthworm communities in a tallgrass prairie. James (199 1) 

found that native Diplocardia spp. processed more soil 

nutrients than introduced European lumbricid species, even 

though the exotics were numerically more abundant. The 

native earthworms apparently more effectively exploited the 

soil volume and were able to function over a wider range of 

soil temperatures (i.e., for longer periods of the year). No 

similar studies were found for forest ecosystems, although 

data from Dotson and Kalisz (1989) suggest that native 

earthworm assemblages in forests of the Southern 

Appalachians are partitioned throughout the forest floor and 

soil volume. 

Earthworm Interactions With Coarse 

Woody Debris 

Earthworms may use CWD as both refuge and resource 

(i.e., as habitat and source of food), while simultaneously 

enhancing the process of decomposition. 

Effects of Earthworms on Wood Decomposition 

Table 3 presents the stages of decomposition of wood and 

the associated organisms at each stage, as summarized from 

Kak (1974) and Ausrnus (1977). Initial stages involve the 

colonization and conditioning of woody tissues by microbes 

and surface-dwelling invertebrates, followed by invasion of 

channelizing invertebrates. Although often considered 

detritivores, earthwoms appear to have only limited ability 

to digest plant residues such as cellulose or lignin; rather, 

microbial biomass that colonizes the detritus probably 

provides nutrition. Hence, earthworms probably do not play 

a substantial role in wood decomposition until the secondary 

colonization phase, although some epigeic species (e.g., 

Bimastos spp.) may explore woody surfaces and under bark, 

feeding on microbes and particulate organic matter. After 

channels are formed, earthworms may contribute to wood 

decay through a number of mechanisms (table 4), including 

transport of soil, nutrients, and microbes into the wood. 

Earthworm interactions with microbes, such as selective 

feeding on fungal hyphae, may also be important. As the 

wood becomes macerated and fragmented, epigeic and 

endogeic species may become more numerous and further 

enhance woody decomposition and incorporation into 

the soil. 

A hypothesized sequence of earthworn colonization of 

CWD is shown in figure 1. Epigeic forms are expected to 

track the proliferation of fungal hyphae, which may be an 

important component of the diet of many earthworm species 

(Lee 1985; Spiers and others 1986). Endogeic (polyhumic 

and geophagic) species are proposed to become more 

abundant later in the sequence. Maximum earthworm 

biodiversity in CWD may occur during the secondary 

colonization and maceration phases of decomposition (table 

3). Ultimately, as the decayed wood becomes a region of 

organically enriched soil, biodiversity should approach that 

of the ambient soil and organic horizons. 

Factors Affecting Earthworm-Coarse Woody Debris 

Interactions 

As already mentioned, earthworm species differ in life 

histories and ecological strategies, and these differences 

determine the extent to which species may interact with 

CWD. Truly endogeic forms (e.g., Diplocardia spp.) may 

incidentally encounter surface wood but show little 

preference for it. Conversely, some epigeic species (e.g., 

Bimastos parvus, the American bark worm) may 

preferentially use CWD. Almost no information is available 

on the relative abilities of native vs. exotic earthworms to 

exploit CWD. Natives might be better adapted over the 

range of climatic and soil conditions at many sites in the 

Southeast, but introduced species might effectively use 

woody substrates in disturbed ecosystems or where exotic 

woody species occur. 

Earthworm assemblages seem to be influenced by certain 

tree species, and by implication perhaps also by CWD. 

Boettcher and Kalisz (1991) found that where 

Time -+ 

Figure 1-Hypothesized changes in abundance of fungal hyphae and 

earthworms during decomposition of coarse woody debris. 
Table 3-Stages of log decay and decomposer activity (adapted from Kaarik 1974 and Ausmus 

1977) 

Decomposition stagelcondition Organisms involved 

Standing dead and sound logs: Bacteria, fungi (pathogens, saprobes) 

Colonizationlconditioning : 

Channelization: 

Successionlsecondary colonization: 

Maceration: 

Incorporation: 

Moulds, blue-stain fungi 

Bacteria (cell contents) 

Diplopods, other surface-dwelling invertebrates 

Soft-rot fungi (cell wall carbohydrates) 

Invertebrates (termites, carpenter ants, 

Passalid beetles) 

Brown-rot fungi (cell wall carbohydrates) 

Channelizing invertebrates 

Non-channelizing invertebrates 

(soil-inhabitants, predators, earthworms) 

Fecal material 

Mineral soil within channels 

White-rot fungi (cell wall carbohydrates 

and lignin) 

Fungal rhizomorphs, root invasion 

Channelizing and non-channelizing 

invertebrates 

Fecal material, mineral soil clogging 

channels 

Mass of mycelia, fibrous and woody roots 

Mineral soil mixed into wood 

Rhododendron mmimum L, was present in Southern 

Appalachian forests, the native earthworm B. pawus was 

dominant; in the absence of rhododendron under yellow 

poplar (Liriodendron tulipifera L.) or eastern hemlock 

(Tsuga canadensis L. Carr), several other native earthworm 

species were more abundant, including Eisenoides 

carolinensis. Use of CWD by these earthworms was not 

discussed, but B. pawus and E. carolinensis are both epigeic 

or epiendogeic and may utilize downed wood in their 

respective stand types. Based on personal observations 

(mostly in Georgia and Florida), it appears that coniferous 

logs are used little by earthworms either as refuges or food 

sources; much more thorough sampling will be needed to 

confirm this. 

Earthworm populations in the Southeast show distinct 

seasonality in their abundance and activity (fig. 2). Greatest 

activity is usually seen in spring, although the timing 

probably varies with latitude and altitude across the region. 

These seasonal cycles probably influence earthworn 

exploitation of CWD. Furthemore, if fallen logs provide 

favorable moisture and temperature conditions beyond those 

of ambient soil and litter, then earthworm activity within 

CWD may be extended. This effect may depend on the 

stage of decomposition, as discussed above. 

Finally, the history and nature of management at a site will 

certainly influence interactions between earthworms and 

CWD. Long-term agriculture typically reduces abundance 

and biodiversity of earthworms (Lee 1985). Reforested 
Table &Suggested influences of earthworms on coarse 

woody debris (after Ausmus 1977 and Swift 1977) 

- Translocation of nutrients and soil into decomposing wood 

- Translocation of microbes and inoculation of decomposing 

wood 

- Regulation of microbial succession 

- Regulation of microbial activity (catabolism, N,-fixation) 

- Enhancement of nutrient leaching from decomposing 

wood 

agricultural lands, therefore, may be depauperate in species 

capable of utilizing CWD, unless undisturbed forests are 

near enough to provide sources for the appropriate species. 

A useful ecosystem management strategy for maintaining 

biodiversity of earthworms and other soil biota might be to 

leave undisturbed source areas within managed forests. In 

logged but uncultivated areas, earthworm species diversity 

may remain relatively high as long as soil disturbance is not 

severe and CWD is left in place after tree harvest. 

Research Priorities 

Several areas are in need of further research relevant to 

earthworms, biodiversity, and CWD in Southeastern forest 

ecosystems: 

* Biotic survey and inventory 

Still undescribed earthworm species probably exist in the 

Southeast glacial refugium. Systematic surveys are needed 

throughout the region to catalog all species and to describe 

and quantify their habitat requirements. Museum 

collections in the region need to be updated with this 

infomation. Also, training of new specialists in earthworm 

systematics is urgently needed because of the age of 

scientists currently working in this area. 

* Process studies 

Little direct evidence is available concerning the effects of 

earthworms on CWD. Experimental manipulations of 

earthworm populations, CWD, and environmental 

Ill I I ',I I1 

NDJFMAMJJASO 

NDJ FMAMJJASO 

Figure 2-Earthworm density and biomass over an annual cycle in a 

mixed hardwood-coniferous riparian forest on the Georgia Piedmont 

(Callaham and Hendrix 1995). 

conditions such as water, temperature, or soil properties in 

the field could reveal conditions under which earthworms 

affect CWD dynamics. Ekosystem-specific (e.g., hardwood 

vs. coniferous) effects would be of particular interest. 

Mechanisms underlying these effects (e.g., earthwormmicrobe interactions) could be profitably investigated in 

short-term laboratory studies. 

Mmagement effect studies 

What management alternatives are currently available to 

maintain biodiversity, particularly of soil biota, in forest 

ecosystems? Field experiments are needed to identify the 

best practices for managing CWD and associated biota. 

Long-term studies should be initiated immediataly. Shortterm estimates might be derived from studies of historical 

management practices and chronosequences. National 

forests in the Southeast may prove to be unique resources 

for such studies. 

Acknowledgments 

The author is indebted to George Brown and Mac Callaham, 

Jr., for their unbounded enthusiasm for earthworm research 

and to D. A. Crossley, Jr., for his patience. 
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processing by earthworms in tallgrass prairie. Ecology. 72:2 10 1-2 109. 

Ausmus, B. S. 1977. Regulation of wood decomposition rates by 

arthropod and annelid populations. In: Lohm, U.; Persson, T., eds. Soil 

organisms as components of ecosystems. Stockholm, Sweden: 

Ecological Bulletin 25, Swedish Natural Science Research Council: 

180- 192. 

Boettcher, S.E.; Kalisz, P.J. 199 1. Single-tree influence on earthworms 

in forest soils in eastern Kentucky. Soil Science Society of America 

Journal. 552362-865. 

Bouch6, M.B. 1977. Strategies lombriciennes. In: Lohm, U.; Persson, T., 

eds. Soil organisms as components of ecosystems. Stockholm, 

Sweden: Ecological Bulletin 25, Swedish Natural Science Research 

Council: 122- 132. 

BouchC, M.B. 1983. The establishment of earthworm communities. In: 

Satchell, J.E., ed. Earthworm ecology from Darwin to vermiculture. 

London: Chapman and Hall: 431-448. 

Caliaham, M.A., Jr.; Hendrix, P.F. [in press]. Comparison of handdigging and formalin extraction as methods for the collection of 

earthworms (Lumbricidae and Megascolecidae) in forest soils on the 

Southern Appalachian Piedmont of Georgia. Soil Biology and 

Biochemistry. 

Dotson, D.B.; Kalisz, P.J. 1989. Characteristics and ecological 

relationships of earthworm assemblages in undisturbed forest soils in 

the Southern Appalachians of Kentucky, U.S.A. Pedobiologia. 33: 21 1- 

220. 

Fender, W.M. 1995. Native earthworms of the Pacific Northwest: an 

ecological overview. In: Hendrix, P. F., ed. Ecology and biogeography 

of earthworms in North America. Boca Raton, FL,: Lewis Publishers: 

53-66. 

Fender, W.M.; McKey-Fender, D. 1990. Oligochaeta: Megascolecidae 

and other earthworms from Western North America. In: Dindal, D., ed. 

Soil biology guide. New York: John Wiley & Sons: 357-378. 

Gates, G.E. 1970. Miscellanea megadrilogica VII. Megadrilogica. 

1:l-14. 

Gates, G.E. 1982. Farewell to North American megadriles. 

Megadrilogica. 4:9-77. 

Hendrix, P.F.; Callaham, M.A., Jr.; Kirn, L. 1994 Ecological studies 

of Neartic earthworms in the Southern U.S.A. 11. Effects of bait 

harvesting on Diplocardia populations in Apalachicola National Forest 

in north FIorida. Megadrilogica. 5:73-76. 

James, S.W. 1995. Systematic, biogeography and ecology of neartic 

earthworms from Eastern, Central and Southwestern United States. 

In: Hendrix, P.F., ed. Ecology and biogeography of earthworms in 

North America. Boca Raton. FL: Lewis Publishers: 29-52. 

Kaarik, A.A. 1974. Decomposition of wood. In Dickinson; C.H.; Pugh, 

G.J.F., eds. Biology of plant litter decomposition. New York: 

Academic Press: 129- 174. 

Kalisz, PJ.; Wood, H.B. 1995. Native and exotic earthworms in 

wildland ecosystems. In: Hendrix, P.F., ed. Ecology and biogeography 

of earthworms in North America, Boca Raton, FL: Lewis Publishers: 

117-126. 

Lee, K.E. 1985. Earthworms: their ecology and relationship with soils 

and land use. Sydney, Australia: Academic Press. 41 1 p. 

Reynolds, J.W. 1972. The activity and distribution of earthworms in tulip 

poplar stands in the Great Smoky Mountains National Park, Sevier 

County, Tennessee (Acanthodrilidae, Lumbricidae and 

Megascolecidae). Bulletin Tall Timbers Research Station. 1 1:41-54. 

Reynolds, J.W. 1976. A preliminary look at the earthworms in North 

American forests, their activity and distribution. Megadrilogica. 

2:l-11. 

Reynolds, J.W. 1995. Status of exotic earthworm systematics and 

biogeography in North America. In: Hendrix, P.F., ed. Ecology and 

biogeography of earthworms in North America. Boca Raton, FL: 

Lewis Publishers: 53-66. 

Reynolds, J.W.; Cook, D.G. 1993. Nomenclatura Oligochaetologica, 

Supplementum Tertium: A catalogue of names, descriptions and type 

specimens of the Oligochaeta. New Brunswick, Canada: New 

Brunswick Museum Monographic Series (Natural Science) No. 9. 

Spiers, G.A.; Gagnon, D.; Nason, T.E. [and others]. 1986. Effects and 

importance of indigenous earthworms on decomposition and nutrient 

cycling in coastal forest ecosystems. Canadian Journal of Forest 

Research. 16:983-989. 

Swift, MJ. 1977. The roles of fungi and animals in the immobilization 

and release of nutrient elements from decomposing branch-wood. In: 

Lohm, U.; Persson, T., eds. Soil organisms as components of 

ecosystems. Stockholm, Sweden: Ecological Bulletin 25, Swedish 

Natural Science Research Council: 193-202. 

Wallwork, J.A. 1983. Earthworm biology. London: Edward Arnold 

Publishers, Institute of Biology's Studies in Biology Number 161. 

296 p. 
Macroinvertebrates and Their Relationship to 

Coarse Woody Debris: With Special Reference to Land Snails 

Ronald S. Caldwell 

Abstract 

Macroinvertebrates are an integral part of the succession in natural 

communities of decomposing logs. Both millipedes and centipedes are 

reported to be associated with coarse woody debris (CWD), but a much 

larger literature exists relative to CWD and land snails. Relationships 

between CWD and land snails are probably similar for other 

macroinvertebrates. Among land snails, 98 species within 9 families are 

associated with log habitats specifically in the Southeast. They are 

involved in regulating decomposition through the dispersal and 

inoculation of microbes and fungi and in nutrient cycling, particularly 

calcium. Although snails are detritivores generally, a greater diversity 

probably occurs where CWD is present. 

Introduction 

One of the earliest references to the community of 

organisms in a fallen log is that of Graham (1925). He 

described the succession of organisms as the chemical and 

physical properties of the log change with its 

decomposition. Graham also referred to different 

microhabitats within the log as favoring certain organisms 

based upon factors such as food, moisture, and temperature. 

Fungi were also characteristic of certain parts of the 

decaying log due to the same factors. In another early 

report from the Southeast, Pearce (1946) described the 

microfauna at Duke Forest, Durham, NC. Pearce's research 

involved leaf litter, not coarse woody debris (CWD) 

specifically. 

Fager (1968) presented a successional picture of 

invertebrates attacking oak wood substrate at an Oxford 

University site. The order of succession in natural log 

communities, after mites and insects and in order of relative 

abundance, was Isopoda, Chilopoda, Oligochaeta, 

Diplopoda, and Gastropoda. Also, Oligochaeta, Isopoda, 

Chilopoda, and Gastropoda were more abundant after bore 

holes were established. 

Ausmus (1977) presented a chronology for organismal 

attack of fallen logs. Fungi attack pith, then attack bark 

Director, Cumberland Mountain Research Center, Lincoln Memorial 

University, Hanogate, TN 37752-2019. 

and surface wood. The result is increasing moisture 

content, nitrogen accumulation, and organic acid 

accumulation. Colonization by channelizing invertebrates 

follows this change in chemical and physical composition 

of the log. 

Table 1 lists millipedes found associated with log habitats 

in CWD in an Illinois woodland (O'Neill 1967). Table 2 

lists species of centipedes associated with log habitats in an 

Illinois woodland (Summers and Uetz 1979). No literature 

citations for these two groups in the Southeastern United 

States were found. No publications were found relative to 

isopods in Southeastern forests. Earthworms are 

considered elsewhere in this volume (Hendrix 1996). 

Hubricht (1985) presented a checklist and distribution maps 

for 523 species and subspecies of native land Mollusca of 

the Eastern United States. Annotated descriptions of the 

habitat are also given. If one discounts the subspecies, 98 

species contained within 9 families are found to be 

associated with log habitats specifically within the 

Southeastern United States. The number of species would 

increase if those associated with both logs and litter were 

counted. 

Food habits of land snails include fungivores, detritivores, 

herbivores, carnivores, and some that may change 

functional groups within a food web (Mason 1974). Mason 

(1970a) determined that the majority of woodland snails 

were feeding on litter. Mason (l970b) found that snails 

ingested 0.35 to 0.43 percent of the annual litter input in a 

beech forest in England. This rate was compared with 

other studies showing that diplopods and isopods ingested 3 

to 4 percent of the leaf litter, oribatid mites 1.8 percent, and 

millipedes 1.7 to 10 percent. He concluded that the chief 

importance of these groups may be to physically and 

chemically alter the litter and thereby promote fungal and 

microbial growth. It is interesting to note that, based on 

biomass comparisons to snails, he extrapolated that slugs 

may ingest as much as 16 percent of the annual litter. 

Many of the ecological functions carried out by land snails 

appear to be similar to those of other macroinvertebrate 

groups. Relationships that exist between land snails and 

CWD probably exist between other macroinvertebrates and 

CWD. 
Table 1-Percentage of millipedes associated with various woody debris habitats from an 

Illinois woodlanda 

Under Within Beneath Surface 

Millipede species Litter logs logs bark of log 

Abacion lacterium 47.4 

Cleidogonia 

caesioannularis 71.4 

Euryurus erythropygus 

Fbntaria virginiensis 2.9 

Narceus americanus 4.7 

Pseudopolydesmus serratus 

Scytonotus granulatus 33.4 

a Data from O'Neill 1967. 

Relationships of Land Snails to the 

Forest Floor 

Regulation of Wood Decomposition 

One important relationship of macroinvertebrates to the 

forest floor ecosystem is regulation of mineralization 

(Ausmus 1977). Bacterial, actinomycete, and fungal 

densities on sawdust substrates were greater in the presence 

of invertebrates in laboratory studies including millipedes 

Table 2-Species of centipedes associated with coarse 

woody debris from an Illinois woodland" 

Log species Log and litter species 

Sonibius politus Bothropolys multidentatus 

Geophilus vitattus Nadabius iowensis 

Nadabius amele 

"Data from Summers and Uetz 1979. 

and centipedes. Four mechanisms regulating wood 

decomposition by wood-inhabiting invertebrates were 

postulated: 

(1) Translocation and defecation increase nutrient input 

to, and the inoculum potential of, wood substrates; 

(2) Passive inoculation, as in the case of wood-surface 

colonizing invertebrates passively inoculating wood and 

predisposing wood substrates to fungal and subsequent 

channelizing invertebrate colonization; 

(3) Microbial succession and the rates of microbial 

catabolism as regulated by invertebrate dynmics, 

creating successive waves of distinct time periods when 

nitrogen is atmospherically fixed and carbon rapidly 

catabolized (these successional waves stabilize and 

increase microbial respiration and probably microbial 

catabolism rates); and 

(4) The creation of spatial heterogeneity within woody 

substrates and microsites of intense physical-chemicalbiological activity. 

Mason (1970a), studying seven species of woodland snails 

in England, found most to be feeding on higher plant 

material. However, one species, Discus rotundatus, had 

significantly greater mounts of fungal material. Table 3 

shows that three species of Discus are associated with log 

debris in the Southeastern United States. Fromming (1954) 
documented that some species of slugs specialize in feeding South Africa. One species of slug listed, Arion hortensis, 

on fungi. However, it can be assumed that if higher plants has been reported from Virginia (Beetle 1973). In marbng 

are the staple diet of many land snails (Crime and Blythe experiments at Coweeta Hydrologic Laboratory in North 

1969), the snails will secondarily ingest fungal spores and Carolina, Mesodon nomalis has been found to migrate 

still act as an inoculation source. Talbot ( 1952) lists fungal 16.6 meters in 2 days, suggesting the potential for snails as 

species transported by woodland invertebrates in a study in agents of nutrient or inoculum dispersal (Caldwell, 

Ronald S., unpublished data). 

Table 3-Number of species of land snails from the 

Southeastern United States that have been found to be 

associated with log debrisa 

Taxon No. of species 

Carychiidae 

Carychium 

Discidae 

Anguispira 

Discus 

Poly gyridae 

Mesodon 

Polygy ra 

Practicolella 

Stenotrema 

Triodopsisb 

Philomycidae 

Pallifera 

Phikomycus 

Punctidae 

Punctum 

Pupillidae 

Gastrocopta 

Vertigo 

Strobilopsidae 

Strobilops 

Zonitidae 

Gastrodonta 

Glyphyalinia 

Mtlsomp hix 

Paravitrea 

Ventridens 

Zonitoides 

Nutrient Cycling 

The role played by soil fauna in nutrient cycling has been 

well documented (Gist and Crossley 1975; McBrayer 1971, 

1977; Swift 1977). In an experimental microcosm, 

leaching was increased from leaves fed upon by millipedes 

(Patten and Witkarnp 1967). Seastedt and Tate (198 1) 

measured decomposition rates for dead millipedes. Shells 

of dead mollusks (mostly calcium) may also act as 

important reservoirs for that element (Mason 1974). 

Land snails can be viewed as a calcium compartment 

within ecosystems. Due to the storage of calcium in shell 

and soft tissues, they may have a significant effect on 

calcium release and cycling to the soil, and soil biota. Gist 

and Crossley (1975) reported density and biomass figures 

for Pulmonata at a North Carolina hardwood site. Foster 

(1 937), studying Neohelix albolabris, found 6.3 3 snails per 

square meter (m2) in a floodplain forest in Illinois. He 

estimated this to represent 3.16 g per m2 of calcium and 

15.8 g per m2 of living tissue. Actual contribution to the 

calcium cycle can be estimated by coupling these figures 

with data given by Reichle and others (1969). On a perweight basis, land snails would appear to tie up more 

calcium than other soil mesofauna. 

No studies exist showing the amount of essential cations 

processed by feral land snails of the Eastern United States. 

McBrayer (1977) concluded that invertebrates have no 

direct effect upon rates of release for essential cations, 

Snails have been shown to have large whole-body 

concentrations of calcium (Cromack and others 1977). 

Reichle and others (1969) present data on whole-tissue 

and shell levels of Mesomphix sp. in a Liriodendron 

tulipiyfera forest. Values given are 77,600 ppm and 

338,100 ppm, respectively, for the two snail species. 

Total 98 The contribution of land snails to the overall calcium 

budget of a forested ecosystem may be insignificant. 

However, as a calcium processor they may be important on 

a Data from Hubricht 1985. a community or microecosystem level, providing calcium 

Includes Neohelix, Webbhelix,and Xolotrema of carbonate, or converting compounds such as calcium 

Emberton 1988. oxalate to (CaCO,) (Cromack and others 1977). Snail 

shells may be an important calcium source for small 
vertebrates. The dependence of land snails on calcium is 

well documented (Baker 1958; Boycott 1934; Burch 1956, 

1957; Petranka 1982; Wareborn 1979). Most obvious of 

the calcium need is the external shell, the fornation of 

which starts in the embryo (Tompa 1980a). Sources for 

shell calcium include mantle, digestive gland, kidney, and 

blood (Wilbur 1964). Slugs (unshelled snails), with no 

external shell, do produce an internal plate of calcium in 

most species (Solem 1974). Other calcium needs in the life 

cycle of the snail are not so obvious. Many families of land 

snails have darts, which are structures composed of 

crystalline calcium that appear to function as Cupid's arrow 

(Tompa 1980b). Other calcium needs include production of 

an egg shell (Tompa 1980a), slime and epiphragm 

production (Fournie and Chetail 1984), and buffering of 

blood during times of aestivation (Baker 1958). Tompa 

(1976) has shown that as much as 10 to 25 mg of calcium 

are mobilized each day in Anguispira altemata during one 

oviposition. 

The major form of calcium available to land snails appears 

to be calcium salts (Wareborn 1969, 1970). Calcium inputs 

from the environment are from two main sources: 

percutaneous movement and dietary (Fournie and Chetail 

1984). The two most common salts are calcium citrate and 

calcium oxalate (Wareborn 1969, 1970). Wareborn (1 979) 

has demonstrated that land snail populations are most dense 

on substrates rich in calcium citrate-producing trees, such 

as elms and maples. Calcium oxalate-producing species, 

such as oak and beech, tend to have fewer species and 

numbers of land snails (Wareborn 1979). On a 

calcium-free substrate, land snails may fail to copulate 

(Voelker 1 959). 

Graustein and others (1977) found calcium oxalate to be a 

common secretory product of fungal hyphae. They 

postulate that calcium oxalate crystals secreted by fungal 

hyphae are a reactive calcium reservoir. Land snails, as 

forest floor grazers, would act as major calcium cyclers. 

Use of Coarse Woody Debris by Terrestrial Molllusca 

As demonstrated in tables 1 and 2, little infornation is 

available on millipedes and centipedes. Of the 

macroinvertebrates, more infomation is available on 

tenestrial Mollusca. Table 3, which shows a total of 98 

species of land Mollusca (snails and slugs). demonstrates 

the importance of CWD to these organisms. Of the 523 

species and subspecies listed by Hubricht (19&5), 401 occur 

in the Southeastern United States. This amounts to 24.4 

percent of the Southeastern terrestrial fauna dependent 

upon GWD. 

Shimek (1930), studying land snails of the Mississippi 

Valley fauna, found a very intimate relationship between 

forests and snails. He found that larger species, especially, 

inhabit woodlands. Table 3 lists three genera that contain 

59 species associated with log debris. Triodopsis, 

Stenotrema, and Mesodon contain some of the largest snails 

in Eastern North America. hhson (1974) also found land 

snails to be more abundant in woodlands, perhaps due to 

greater habitat diversity. Interestingly, he also reported 

slug densities in a European Fizgus woodland to be 14 

slugs per m2. 

Jacot (1935) found that the number of individuals or 

species of land snails was not correlated with the age of the 

forest on sites near Asheville, NC. However, the proximity 

of old-growth stands and the amount of shelter available 

influenced the repopulation of cut forests. 

Table 4 lists land snails that were significantly associated 

with log debris in the Hiwassee River Basin of Tennessee 

(Coney and others 1982). This is the only publication that 

analyzes land snail habitat statistically in the Southeastern 

United States. Further study would no doubt add to this list. 

The association between snails and logs may be 

comparatively long lived. Comfort (1957) presents data on 

life spans of mollusks. Species found in the Eastern United 

States have been known to live up to 9 years. Harmon and 

Hua (1991) point out that CWD may persist for centuries. 

Land snails may have adapted to these long-term cycles and 

perhaps successional species can be found. Land snails are 

capable of homing behavior (Edelstam and Palmer 1950) 

and show seasonal movement. This behavior would benefit 

feeding, overwintering, or aestivation. 

Conclusions and Recormmendations 

From the foregoing discussion, it can be seen that GWD is 

important to a large percentage of the land snail fauna of 

the Southeastern United States. Little data exist concerning 

other macroinvertebrate groups, which no doubt are equally 

dependent upon CWD. 

hfaser and others (1988) point out that future forests will 

have much less 0. If so, then biodiversity in some taxa 

of macroinvertebrates would be reduced. Studies are 

needed to deternine the nature of the dependence of the 

major invertebrate taxa on CWD. These studies should 

include the importance of invertebrates in successional 

stages of wood decomposition. 
Table &Snail species significantly associated with log 

debris by log taxa in the Wiwassee River Basin of 

Tennesseea 

Lc;)tidobalanus (white oak group) 

Gastrocopta contracta 

Gastrodonta interna 

Ijaplotrema concavum 

Helicodiscus notius 

Mesodon inflectus 

M. perigraptus 

Stenotrema stenotrema 

Zonitoides arboreus 

Eqthrobalanus (red oak group) 

Gastrocopta contracta 

Gastrodonta intema 

Hap totrema concavum 

Heticodiscus notius 

Mesodon inflectus 

M. perigraptus 

Stenotrema stenotrema 

Zonitoides arboreus 

Castanea dentata (American chestnut) 

Gastrocopta contracta 

Gastrodonta interna 

Haplotrema concavum 

Helicodiscus notius 

Mesodon inftectus 

Stenotrema stenotrema 

Carya spp. (hickories) 

Gastrodonta interna 

Mesodon inflectus 

Zonitoides arboreus 

Liriodendron tulipifera (tulip poplar) 

Gastrodonta interna 

Haplotrema concavum 

Zonitoides arboreus 

a Data from Coney and others 1982. 

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Relationship of Wood-Feeding Insects 

and Coarse Woody Debris 

James L. Hanula 

Abstract 

Wood-feeding insects serve as food for vertebrates and invertebrates, 

condition the habitat for later successional organisms, disperse a variety 

of organisms, and, in some cases, generate coarse woody debris (CWD). 

This discussion is limited to insects that actively bore into and derive 

nutrients from the phloem or xylem and are probably important to 

decomposition. The majority of these insects are in the order Coleoptera, 

but several other orders are represented. Although a large amount of 

literature exists, most of it focuses on relatively few, commercially 

important insects and provides little information about their role in CWD 

decomposition, nutrient cycling, and energy transfer. More is known 

about the influence of geographic area, tree species, type of tree tissue, 

moisture, temperature, size of woody material, and fungal communities 

on wood-feeding insects. 

Wood-feeding insects represent a large portion of the fauna 

that inhabit dead and dying trees. They provide food for 

vertebrates and invertebrates; alter the habitat, making it 

acceptable for subsequent inhabitants; serve as transport for 

a variety of organisms; and, in some cases, are responsible 

for generating coarse woody debris (CWD). 

In choosing the insects to include in this discussion, I 

needed to define wood-feeding insects and considered a 

number of questions. For example, are species that feed on 

phloem and obtain their nutrients from the cell contents, 

rather than cellulose, wood-feeders? Should insects that 

bore into wood but rely on externally growing symbiotic 

fungi for food be included? Should those species that ingest 

wood fibers but require nutrients or enzymes from ingested 

microorganisms to complete development be considered? 

Are insects that rely on gut-inhabiting symbiotic protozoa 

to digest cellulose wood-eaters? 

These questions point to the many ways insects have 

evolved to take advantage of the energy stored in trees. I 

chose a broad definition that is not based on where the 

microorganisms that aid in digesting the wood are located, 

because almost all wood-feeding species have some 

symbionts that help them use wood as a food source. 

However, I restricted the discussion to insects that actively 

bore into and derive nutrients from the phloem or xylem 

Research Entomologist, USDA Forest Service, Southern Research 

Station, Athens, GA 30602. 

(wood) of trees in terrestrial habitats and are likely to be 

important in the decomposition process. 

Wood-feeding insects occur in many orders of the class 

Insecta, from the primitive eusocial termites to the more 

highly evolved Hymenoptera; however, the majority are 

Coleoptera. Individual life histories and habits of the 

wood-feeding groups or species is beyond the scope of this 

paper. Readers can find this information elsewhere 

(Anderson 1960; Barbosa and Wagner 1989; Coulson and 

Witter 1984; Drooz 1985; Hickin 1976). In addition to the 

life history and habits of the economically important woodfeeding insects and their associates, some researchers have 

looked at the community and successional patterns of 

insects in woody debris (Blackman and Stage 19 18, 1924; 

Elton 1966; Fager 1968; Graham 1925; Howden and Vogt 

195 1; Savely 1939; Townsend 1886). Despite this large 

body of excellent work on a number of CWD inhabitants, 

little attention has been given to how insects affect 

decomposition, nutrient cycling, or energy flow in this 

habitat. 

The following discusses the principal groups of insects 

feeding on CWD in the South, their roles in CWD, and how 

CWD habitat affects insect communities and vice versa. 

Wood-Feeding Insects 

Most of the information on wood-feeding insects focuses 

on those species that cause economic injury to trees or 

damage wood products. As a result, literally thousands of 

publications have been written about termites and bark 

beetles, while little information is available on the woodeating Tenebrionidae, Elateridae, or Alleculidae, The 

appendix presents a partial listing of wood-feeding species 

in the South, their habits (phloem vs. xylem feeders, branch 

vs. bole inhabitants, etc.) and their host associations. 

Compiling the appendix was relatively easy for the 

economically important families. However, as Elton and 

Miller (1954) discovered 40 years ago, I found that an 

incredible number of species have been described 

taxonomically, but with no description of their "ecological 

setting and context." Therefore, the wood-feeding members 

of some of the largest families are not included because 

either larval host records are scattered or do not exist, or 

their function within the larval habitat has not been defined. 
Order Dictyoptera-Cockroaches 

Family Cryptocercidae. This family contains one species, 

Cq)ptocercus punctulatus, which occurs in moist rotted 

logs, particularly oak. Entomologists are interested in this 

reddish brown, wingless insect because it serves as a 

phylogenetic link between roaches and termites. Like 

termites, C. punctulatus harbors xylophagous protozoa that 

help with digestion of its wood fiber diet (Maittrick 1964, 

1965). Little is known about its relationship to CWD, 

although it is not likely to be important in decomposition. 

Order Isoptera-Termites 

Only 8 of the 2,100 species of termites are found in more 

than one or two Southern States, and only 4 species are 

common throughout the South. Despite the relatively small 

number of termite species, they are probably one of the 

dominant components of southern forest ecosystems that 

influence the decomposition of CWD. Termites are 

important to man throughout the world, and receive 

considerable attention and study as demonstrated by the 

extensive bibliographies compiled by Snyder (1949, 1961, 

1968) and Ernest (1986). This literature deals primarily 

with the biology and control of termites, while relatively 

little attention has been directed at their ecological role in 

the temperate forests of North America (Lee and Wood 

197 1 ; Lobry de Brun and Conacher 1990). 

Termites are social insects forming colonies usually 

produced by a single mated pair. Colonies may be 

composed of a king and queen (primary reproductives), 

supplementary reproductives, immatures, nymphs, soldiers, 

workers, and alates or winged reproductives (Weesner 

1965). Alates initiate new colonies following reproductive 

flights that occur during specific times of the year. The 

timing of these flights depends upon the species. Males 

and females pair during the flights, prepare copularia in 

suitable habitats, mate, and begin producing young. As the 

newly produced apterous nymphs mature, they form the 

worker caste of sterile terminal form (no longer molting) 

individuals that, along with the nymphs, undertake all 

aspects of colony care and construction. Soldiers are also 

sterile, mature individuals that must be fed by workers and, 

as their name implies, are responsible for colony defense. 

Supplementary reproductives either replace the queen when 

she dies, or, in some species, supplement the buildup of the 

colony population. Alates, or winged reproductives that are 

produced in large numbers during certain seasons, are not 

found in the colony at other times (Krishna and Weesner 

1969; Weesner 1965). 

Termites in the Southern United States primarily feed on 

cellulose from wood. Lower-order termites have flageIlate 

protozoans in their gut to aid in cellulose digestion, while 

the Termitidae rely on symbiotic bacteria (Wood 1978). 

The wood of most trees is acceptable food for termites 

(Wood 1978), so the appendix does not list hosts for the 

Isoptera. However, termite species show distinct 

preferences for specific woods (Smythe and Carter 1969) 

and in some cases prefer wood infected by specific fungi 

(Smythe and others 1971). The presence of other fungi 

may result in termite rejection of the wood as a food source 

or in poor termite survival (Becker 1969; Smythe and 

others 197 1). 

Wood density is also a factor in food preference. Soft fastgrowing springwood is usually preferred over denser 

latewood. This preference frequently results in thin layers 

of latewood remaining in logs where the more preferred 

earlywood has been excavated. 

Termites are a relatively small group with two families 

represented in the South (appendix). The drywood termites 

(Kalotermitidae) are predominately found in Florida, 

although several species are more widely distributed. The 

subterranean termites in the family Rhinotermitidae include 

the most common species, Reticulitermesflavipes and R. 

virginicus. A third subterranean species, the Formosan 

termite Coptotermes formusanus, was introduced into 

Louisiana and is now widely distributed in the South. This 

non-native species consumes wood at a faster rate and also 

infests wood of living trees. Its potential impact on the 

forested ecosystems of the South has not been investigated. 

Termites are a ubiquitous component of the decomposer 

community in the South, which has been studied 

extensively. Their ecosystem roles have been considered in 

other parts of the world as well (Wood 1976, 1978; Lee and 

Wood 1971; Gentry and Whitford 1982; Lobry de Brun and 

Conacher 1990). However, considering their potential 

importance in CWD and soil modification, the role of 

subterranean termites in these processes has been neglected 

in the Southern United States. 

Order Coleoptera-Beetles 

The order Coleoptera, the largest in the Class Insecta, has 

over 30,000 species in the United States (Borror and others 

1976). Twenty-four of the 110 families represented in the 

United States and described by Arnett (1968) include 

terrestrial wood-feeding species. However, only in the 
relatively small families (e.g., Platypodidae) are all 

members wood-feeders. The appendix contains a partial 

listing of the wood-feeding Coleoptera in the South. This 

list includes species that attack living and dead trees, those 

that feed on phloem or xylem tissue, and those that feed on 

wood in its last stages of decomposition. A large percentage 

of the xylophagous species rely on gut-inhabiting 

microfauna for the partial breakdown of cellulose. I have 

also included the ambrosia beetles; those species inoculate 

their galleries in wood with specific fungi on which the 

larvae feed. The inclusion of insects feeding in well-rotted 

logs is arbitrary, because many of these species derive part 

or all of their nutrition from fungi and other 

microorganisms that they ingest with the wood fibers. 

However, they are important in fragmentation of CWD 

(Ausmus 1977) and may contribute to incorporation of 

decomposed wood into the soil. 

A number of beetles attack living trees where they feed on 

xylem tissue. These insects play at least two roles relating 

to CWD. First, they weaken trees structurally, making 

them more susceptible to breakage and resulting in CWD 

input. Second, they contribute to the decomposition of 

CWD by opening the tree bole to invasion by fungi and 

other organisms before the tree dies, resulting in CWD that 

is well advanced in decomposition before it even enters the 

detritus food web. 

The appendix does not contain species lists for the families 

Elateridae, Tenebrionidae, Alleculidae, and Melandryidae, 

even though these families probably contain wood-feeders 

(Arnett 1968). Species descriptions in these families are 

frequently based on adult insects often caught by means 

that provide no information on the larval habits. Therefore, 

host records, if they exist, give no useful infomation in 

regard to CWD. 

Families Lucanidae, Passalidae, and Scarabaeidae. 

During the larval stage, the C-shaped white grubs of these 

families are similar in appearance. Richter (1966) provided 

keys to the larvae and brief descriptions of the biology of 

some of the common species. Lmae of all three families 

are found in well-rotted logs. Lucanids and scarabs are 

solitary, while the passalids form loose social groups in 

which the adults feed chewed wood mixed with saliva to 

the larvae (Gray 1946). Because they are large, these 

insects may be important in both direct and indirect CW 

fragmentation. 

Families Buprestidae and Gerambycidae, The flatheaded 

or metallic wood borers (Buprestidae) and the long-horned 

wood borers (Cerambycidae) are large, diverse families that 

contain some of the most common and important woodfeeding species. Franklin and Lund (1956) compiled the 

species of Buprestidae that occur in Georgia, which include 

the common Southern species. Linsley ( 196 1, 1962a, 

1962b, 1964) and Linsley and Chemsak (1972, 1976, 1984) 

revised most of the subfamilies of Cerambycidae and 

provided biological information on species when available. 

A number of species are common in recently killed trees, 

where they often feed initially on phloem and then enter the 

sapwood or heartwood to complete their development. 

Others feed exclusively on wood in conditions ranging 

from wood of live trees to wood in the final stages of 

decomposition. Some attack stumps and boles while others 

occupy only branches of certain size classes. Both families 

contain species that attack living trees, either weakening or 

killing them, while some species contribute to woody 

debris input by girdling or pruning twigs or branches. 

More detailed accounts of common injurious species are 

provided by Drooz (1985) or Coulson and Witter (19841, 

Families Elateridae, Tenebrionidae, Alleculidae, and 

Melandryidae. Little is known of the larval habits of these 

families, although adults and larvae of some species are 

found in CWD. Some of the elaterids or click beetles 

found in CWD are known predators, while others are 

probably wood-feeders (Amett 1968). 

Family Curculionidae. Despite the large size of this 

family, relatively few weevils can be classified as woodfeeders. However, several are commonly associated with 

CWD in the South. These include the Pales and pitcheating weevils, Hylobius pales and Pachylobius picovorus, 

and the deodar weevil, Pissodes nemorensis, which feed on 

the phloem of recently killed pine tree boles, stumps, and 

roots. The remaining species are also primarily phloem 

feeders on a variety of host species, although a few weevils 

feed on rotten wood and some bore into sound wood. 

Families Anobiidae, Lyctidae, and Bostrichidae. These 

families are grouped together because all the species found 

in CWD are xylophagous, and most are capable of feeding 

on, or prefer, relatively dry wood. Because the woodfeeding larvae of these three families pack their tunnels 

with a fine powderlike boring dust and frass, they are 

labeled '"oowder-post beetles," a name officially applied to 

the Lyctidae. These beetles are likely to occur where other 

wood-feeding species are rare, such as standing dead trees 

on xeric sites or dead limbs still attached to trees, because 

they are able to attack relatively dry wood. Some members 

of the family Curculionidae (subfamily Gossoninae) could 

also be included in this group. 
Families Seolytidae and Platypodidae. The bark beetles, 

or scolytids, contain a large number of the most important 

forest pests. They often arrive first at newly created CWD 

or, in some cases, they contribute significantly to CWD 

input. These insects are primarily phloem feeders that 

attack all parts of the tree. A number also bore into wood. 

Some feed in the lower bole while others feed only in 

branches of a particular size class. Some species of 

Scolytidae (tribe Xyleborini) and all of the Platypodidae are 

ambrosia beetles that feed larvae by inoculating adultconstructed galleries with a mold-type fungus (Graham 

1966; Norris 1979). Bark beetles have received 

considerable attention because they are economically 

important. In two excellent books, Wood (1982,1987) has 

revised the New World species and compiled the literature 

references on these beetles. 

Order Lepidoptera-Moths 

Families Noctuidae, Sesiidae, and Cossidae. Moth larvae 

or caterpillars that feed on wood in the South are found in 

these three families. Only one species of Noctuidae feeds 

on wood in the South: Scolecocampa liburna, a common 

species found in rotting logs. The remaining species, in the 

families Sessidae and Cossidae, are found in live trees, 

feeding primarily on wood, although a few are - 

phloeophagus. These species contribute to decomposition 

of wood before the tree dies, increasing tree susceptibility to 

wind breakage and disease. Drooz (1985) and Johnson and 

Lyon (1988) have reviewed the biologies of the important 

pest species in these families. 

Order Hymenoptera-Wasps and Bees 

Families Siricidae and Xiphydriidae. Both families in 

this order bore in wood and have similar habits. Morgan 

(1968) reviewed the literature on Siricidae, and Smith 

(1976) revised the literature on xiphydriids of North 

America with notes on hosts and biology. Although the 

woodwasps actively bore in wood of very weak or dead 

trees, they rely on symbiotic fungi inoculated into the tree 

during oviposition as an aid in digestion (Martin 1987) or 

possibly as a sole food source (Morgan 1968). 

Roles of Wood-Feeding Insects in 

Coarse Woody Debris 

Studies of wood-feeding insects in CWD have focused 

primarily on CVVD as a habitat and on the community 

structure and successional changes that occur as the wood 

decomposes (Townsend 1886; Blackman and Stage 19 18, 

1924; Graham 1925; Save1 y 1939; Howden and Vogt 195 1 ; 

Fager 1968; Elton 1966). Very little attention has been 

given to the effects of wood-feeding insects on the 

processes of energy flow and nutrient cycling. Despite this 

lack of study, Harmon and others (1 986) show that woodfeeding insects serve important functions in forest 

ecosystems. 

Coarse Woody Debris Input 

Insects are just one of many factors contributing CWD to 

forested ecosystems, where their relative importance in this 

role depends on forest type (Harmon and others 1986). In 

the South, pines are the dominant tree species in the 

Coastal Plain and Piedmont and, as a result of both natural 

and man-related activities, Pinus spp. represent one of the 

major sources of CWD in this region. Aside from man, the 

southern pine beetle (SPB) Dendroctonus frontalis is one of 

the primary factors influencing the spatial and temporal 

arrangement of CWD in southern forests. Price and others 

(1991) have compiled an excellent historical account of 

SPB outbreaks with detailed maps of outbreaks over a 30- 

year period. Their work demonstrates the spatial and 

temporal variability of CWD input in southern forests. 

Table 1 shows the temporal changes in CWD resulting from 

SPB activity across the South. Regional loss figures in 

table 1 were calculated from the State volume figures I 

provided by Price and others (199 1). The number of trees is 

estimated by calculating the volume of a tree 22-m tall, 50- 

cm diameter at the butt end, and tapering to a 10-cm 

diameter top. The volume figure for each year was then 

divided by the per-tree volume to determine the number of 1 

trees. Similarly, the number of hectares of trees killed was i 

estimated by assuming that each hectare contained 178 

trees. These data show the potential CWD input from SPB I 

activity, but timber salvage efforts reduced the actual input. 

For example, in 1980 SPB killed 8.6 million m3 of wood as 

the equivalent of 5.9 million large trees. However, the 

mount of wood not salvaged was only 4.0 million m3 or 

about 47 percent of the total mortality. Without SPB 

suppression efforts, the figures in table 1 would be much 

higher, as demonstrated in a potential wilderness area in 

Texas where SPB killed 1416 hectares of pine, equivalent 

to 94,400 m3 of wood, before control measures were 

initiated and the infestation was stopped (Billings 1992). 

The SPB is the only wood-feeding insect that causes largescale forest mortality in the South. However, other species 

may also be important. Populations of pine engravers (Ips 

spp.) frequently build up in logging slash, windthrown, or 

lightning-struck trees, and subsequent generations attack 

healthy trees. Quick decline of these populations usually I 
Table 1-Potential CWI volume input over an 18-year 

period resulting from southern pine beetle, f). frontalis, 

activity in the Southern United States, and estimates of 

the number of trees and hectares of forest affected" 

Year Volume (m3) No. of treesb Hectaresc 

millions- - - - - 

a Compiled from Price and others (1991). 

Estimates based on average tree 20-m tall, 

50-cm diameter at base, and 10-crn diameter 

at the top. 

Estimate based on each hectare containing 

178 trees. 

results in small groups of dead trees (Drooz 1985). 

Thatcher (1 960) reported that pine engraver activity 

resulted in a loss of 3.7 million m3 of timber in southern 

forests, while Baker (1972) reported 1.1 million m3 per year 

of pine mortality due to these beetles in Florida alone. Ips 

bark beetle may represent a major source of CWD in this 

region because infestations are usually small and scattered, 

and salvage is often not economically feasible. 

In southern hardwood forests, wood-feeding insects are 

probably a much less important source of tree mortality. 

The hickory bark beetle, Sccllytus guadrispinous, is capable 

of localized outbreaks that result in significant tree 

mortality (Beat and Massey 1945; Drooz 1985), and woodfeeding insects serve as vectors of several important and 

lethal hardwood tree diseases including oak wilt, 

Ceratocystisfagacearum (Rexrode 1968; Rexrode and 

Jones 1970),and Dutch elm disease, C. ulmi (Carter 1962). 

Borers that feed on the sapwood or heartwood of live trees 

contribute indirectly to CWD input in hardwood forests by 

weakening trees, making them susceptible to wind 

breakage or disease. Finally, twig and branch pruners and 

girdlers (table 1) can add small woody debris through their 

feeding and oviposition behavior. 

Vectors and Transport 

Wood-feeding insects carry a large array of pathogenic and 

saprophytic microorganisms as they move from tree to tree. 

Whitney (1982) provides an extensive list of symbiotes of 

conifer-killing bark beetles. The list includes 38 genera of 

fungi, 17 genera of bacteria, and 4 genera of protozoans. 

These numbers are remarkable only because the survey was 

limited to the more aggressive tree-killing species of four 

bark beetle genera. 

A number of wood-feeding insects, such as mbrosia 

beetles and woodwasps, have specific associations with 

fungi that they carry and use for food. Norris (1979) lists 

the ambrosia fungi of the Xyleborini beetles (Scolytidae) 

and the types of mycangia that have evolved in these 

beetles for carrying their symbiotic fungi. Woodwasps 

(Siricidae and Xiphydriidae) have similar associations. 

Morgan (1968) has reviewed the biology of siricids and 

their fungal symbiotes. Woodwasps use long ovipositors to 

drill holes 2-15 nun into the wood, where they deposit eggs 

and the symbiotic fungi upon which the young depend. 

Fungi associated with woodwasps probably affect C'WD 

decomposition more than those associated with 

ambrosia beetles. 

A number of mite species rely on wood-feeding insects for 

transport between habitats. Eighteen species of mites are 

recorded as phoretic on the SPB alone (Moser 1976). 

Moser and Roton (1971) found 96 species of mites 

associated with bark beetle-infested trees in Louisiana and 

listed the subcortical insects that served as phoretic hosts. 

The long list suggests that most wood-feeding insects carry 

mites between habitats. Soper and Olson (1963) reported 

13 genera of mites associated with lMonochamus spp. in 

Maine. The majority were thought to be phoretic. 

Nematodes are also carried by wood-feeding insects. 

Massey (1974) found 5 1 genera of nematodes that were 

parasitic on or associated with bark beetles in the United 

States. Parasitic species were carried internally to new bark 

beetle habitats, while most of the other species associated 
with bark beetles are probably phoretic. Dwinell and 

Nickle (1989) considered most of the 49 species of 

mycophagous Bursaphelenchus nematodes to be phoretic 

on wood-borers. 

These studies suggest that wood-feeding insects probably 

carry a much greater number and diversity of organisms 

than is currently known and, for those organisms, serve as a 

vital link between habitats . 

Exposure of Wood to Other Organisms 

Wood-feeding insects not only transport organisms to new 

CWD habitats, they also create openings and modify CWD 

so that other organisms can gain access or survive. Entry 

holes by bark beetles allow other organisms to enter the 

inner bark. For example, Dowding (1973) found that 

prevention of bark beetle attacks on Pinus sylvestris logs 

greatly reduced the numbers of Diptera found. A large 

number of the scavengers and predators associated with 

SPBs (Overgaard 1968) used openings created by bark 

beetles to enter the inner bark. For example, some of the 

96 species of mites associated with bark beetles in 

Louisiana entered through holes created by the bark beetles 

(Moser and Roton 197 1). Whitney and Cobb (1972) 

maintained that beetle tunnels are an important mode of 

entry for Basidiomycotina and other fungi in ponderosa 

pine. However, Dowding (1982) questioned the importance 

of beetle tunnels for fungal colonization by airborne spores, 

suggesting that other wound sites are more important. 

Swift and Boddy (1982) state that after ambrosia beetles 

vacate their galleries the tunnels provide infection courts 

for nonsymbiotic fungi. 

Channelization and Fragmentation 

Insects tunnel through CWD by chewing, digesting, and 

excreting both phloem and xylem. Some species (e.g., 

powderpost beetles) tightly pack the wood particles and 

excrement in the larval mines, while others (e.g., termites) 

clear their galleries. Phloeophagus insects mine the inner 

bark and cambium extensively and introduce fungi that, in 

combination with beetle tunneling, loosen the bark, which 

eventually sloughs off. 

Insect feeding in the wood is a direct form of 

fragmentation. In addition, the combination of insect 

feeding and fungal decomposition weakens the wood. 

making it more susceptible to accelerated fragmentation by 

woodpeckers (Kroll and others 1980) and other vertebrates 

in search of food (e.g., bears, skunks). 

MacMillan (1988) found that fragmentation was a major 

reason for the disappearance of oak, hickory, and beech 

CWD in Indiana although the organisms responsible were 

not identified. The principal channelizers in hardwood logs 

on mesic sites in Tennessee (termites, carpenter ants, and 

passalid beetles) regulate the rate of decomposition by 

altering the substrate and shifting the competitive 

advantage of microbial colonizers (Ausmus 1977). 

Most nutrients are probably transferred out of logs and 

snags through fragmentation (Harmon and others 1986). 

Channelization and fragmentation by wood-feeding insects 

have been implicated in the initiation and acceleration of 

nutrient loss from decaying branch wood (Swift 1977; 

Swift and Boddy 1982) and tree boles (Ausmus 1977). 

However, nutrient loss probably depends on the element 

involved. For example, nitrogen content is highest in the 

later stages of decay when CWD is more susceptible to 

fragmentation. Conversely, potassium content is low due to 

leaching (Swift 1977) and is less affected by fragmentation 

(Harmon and others 1986). Although wood-feeding insects 

play an important role in CWD decomposition and nutrient 

transfer, few quantitative data are available on their role in 

leaching or fragmentation losses. 

Energy Transfer 

The intricate food webs and succession of wood-feeding 

insects in CWD during decomposition are indicative of the 

energy release from this resource. I found no quantitative 

data on this subject, although it is likely that these data 

could be determined from the literature on bark beetle 

population dynamics at least for the major tree-killing 

species of bark beetles and possibly for their parasites and 

predators. However, similar data are not available for the 

large majority of the other wood-feeding insects. 

Coarse Woody Debris as a Habitat 

for Wood-Feeding Insects 

The wood-feeding insect community is affected by a wide 

range of factors from geographic location to microclimatic 

condition. Unlike the role of insects in decomposition 

processes, the heterogeneity of CWD and its impact on 

insect communities is understood better. This is 

particularly true for economically important species, such 

as bark beetles and termites. Much less is known about the 

myriad of other species that feed on wood. 
Wood-feeding insect communities vary across elevational 

and latitudinal gradients. A good example of latitudinal 

differences is termite diversity, which decreases as one 

moves south to north (Wood and Sands 1978). In the 

United States, 13 species occur in Florida, while only 1 

species has been reported in New Hampshire (Light 1934; 

Nickle and Collins 1989). Insect diversity also tends to 

decrease with increasing elevation (Wood and Sands 1978). 

However, in compiling table 1 it was clear that North 

Carolina has a number of wood-feeding insects associated 

with host-tree species unique to the upper elevations of the 

Southern Appalachian mountains, as well as a number of 

insects more typically found in northern regions. The 

higher elevation allows insects to extend their range farther 

south than is possible along the Coastal Plain. Therefore, 

oak trees of comparable size dying at the same time in 

south Georgia, in the upper elevations of North Carolina, 

and in New Hampshire are likely to have different woodfeeding insect communities. However, the similarity 

between the North Carolina and New Hampshire trees may 

be greater than one would predict based on changes in 

latitude alone. 

A number of other factors influence the insect community 

after a tree dies in a given region. The timing of CWD input 

influences insects. This is particularly true for the early 

successional community in phloem and for insects that have 

only one restricted flight period annually. Xylophagous 

insects may be less affected by timing because the wood 

deteriorates more slowly than the phloem. However, 

termites were found in SPB-killed trees 3 months after 

death (Barrone 1970). This rapid colonization by termites 

could exclude other wood-feeding insects that normally 

arrive later. 

One of the most obvious factors affecting insect 

communities in CWD is tree species. A quick glance at 

table 1 shows that many wood feeders are restricted to one 

or a few species of host trees, often within a single genus, 

while others have broad host ranges. In general, the more 

restricted host lists indicate those species that arrive during 

or soon after tree death, while the expanded host lists 

indicate species using later stages of decay. Those species 

that arrive early in the decomposition process are often 

more specialized because they must overcome the plant's 

secondary or defensive compounds (Kaarik 1974; Haack 

and Slansb 1987). Other insects are capable of utilizing a 

wide range of tree species but show preference for certain 

species. For example, temites show distinct preference for 

certain woods in laboratory bioassays (Sn~ythe and Carter 

1969, 1970); however, very little is known about their 

natural preferences under field conditions (Waller and 

LaFage 1987). 

In addition to differences among species, the resistance of 

wood to decomposers varies within species (Clark 1957), as 

well as within individual trees. For example, the sapwood 

of bald cypress, &odium distichurn, is readily consumed 

by the Formosan termite, Coptotemes formosanus, because 

it is unprotected by the allelochemicals found in the 

heartwood (Scheffrahn and others 1988). 

The position of CWD can also affect wood-feeding insects. 

Howden and Vogt (195 1) found considerable differences 

between the insect communities in standing dead pines 

compared to felled trees (Savely 1939). However, the 

differences noted could have resulted from other factors, 

such as temporal and spatial differences or tree species. 

The location of woody debris an rnesic or xeric sites 

(Abbott and Crossley 1982) or on slopes with different 

aspects can affect CWD moisture content and 

decomposition process (Mattson and others 1987) and 

probably the insect community as well. 

The moisture content of logs is a critical factor in shaping 

CWD communities, as Graham (1925) demonstrated for the 

cerambycids Asemum sp. and Monochamus sp. Likewise, 

the termite C. fomzosanus preferred wood with the highest 

initial moisture content (Delaplane and LaFage 1989). 

Other wood-feeding insects show a preference for, or an 

ability to use, dry wood (e.g., Lyctidae). 

Wood temperature may also affect insect community 

development in CWD. For example, Graham (1925) found 

that the buprestid Chrysobothris dentripes occurred on the 

tops of logs exposed to direct sunlight, and Savely (1939) 

demonstrated that a Chrysobothris sp. had a tolerance for 

high temperatures that excluded other species. Therefore, 

insect communities of logs or snags exposed to direct 

sunlight may differ from those in shaded areas or on northfacing slopes. 

The size of CWD can affect insect cornunity composition. 

Table 1 clearly demonstrates that some beetle species prefer 

small branches, while others attack only the base of trees 

(e.g., Dendroctonus terebrans or Platypus flavicomis). 

Some wood-feeding termites also prefer large logs while 

others feed on small branches (Wood 1976). 
Fungi play a key role in the use of CWD by certain insects. 

Some insects are dependent on fungi for food and have 

developed very specific associations, e.g., ambrosia beetles 

and woodwasps. In addition to species that rely on specific 

fungi, many wood-feeding insects are affected by the 

fungal community in CWD in a variety of ways. Swift and 

Boddy (1982) provide a detailed discussion of the 

interaction between fungi and insects. 

Fungi contribute to the nutritional ecology of wood-feeding 

insects in several ways. First, the fungi contribute nutrients 

for insect development not found in sufficient amounts in 

wood alone; in particular, nitrogen and other elements are 

concentrated in fungal mycelia (Swift 1977, 1978). 

Second, fungi partially break down or digest the wood, 

leaving behind a softer, more chewable resource that may 

be more readily assimilated (Swift and Boddy 1982). For 

example, Reticulitermesflavipes, a common subterranean 

termite species in the Eastern U.S., preferred and survived 

better on wood decayed by a number of brown-rot fungi 

(Srnythe and others 1971). Third, fungi increase the 

moisture content of decaying wood, which may alter its 

acceptability as a habitat and food source for some woodfeeding insects. Fourth, enzymes produced by fungi and 

ingested by insects with the wood they eat provide yet 

another benefit. Martin (1987) reviewed the literature on 

ingested fungal enzymes and suggested that ingested 

enzymes will prove to be responsible for cellulose digestion 

in the xylophagous members of the Cerambycidae, 

Buprestidae, and Anobiidae families. Finally, fungi are 

important in detoxifying wood that contains toxic or 

repellent allelochemicals. Swift and Boddy (1982) 

summarize several studies that demonstrated termites' use 

of wood when fungi reduced the quantity of 

allelochemicals present. 

Fungi can also have a negative effect on insects. Becker 

(1969) found that pine stumps decayed by white-rot fungi 

were usually free of termites, and Amburgey and Beal 

(1977) showed that the white-rot fungus Gumderma 

upplunutum inhibited feeding by Reticulitermes spp. on 

infected wooden stakes. Smythe and others (197 2) 

demonstrated reduced survival for R. Jlavipes on wood 

decayed by Poria cocos and I? munticola. 

It is evident from this brief discussion that wood-feeding 

insect communities in CWD are shaped by a number of 

factors; and, as a result, the composition of these 

communities may vary considerably depending upon the 

combination of conditions in which the CWD is produced 

and decomposes. 

Summary 

Wood-feeding insects are a major component of the 

diversity of organisms associated with CWD and southem 

forests. Their feeding activity alters the habitat, they carry 

with them a wide array of organisms from bacteria to mites 

that further influence the environment and decomposition 

process, and they provide openings and food for complexes 

of other organisms. As a result of these activities, woodfeeding insects have a significant impact on CWD 

decomposition and the communities of organisms involved. 

Conversely, the wood-feeding insects are affected by a 

number of physical and biological factors that determine 

their ability to use CWD. 

Despite the obvious activity and abundance of woodfeeding insects in CWD, few have been studied. Those 

studied extensively are predominantly pest species that 

occur early in community succession on CWD, attack 

living trees, or affect structural wood. These studies have 

focused on basic insect biology and control with little or no 

emphasis on the role insects play in the decomposition 

process. In general, studies on CWD decomposition have 

not considered the role of insects (Harmon and others 

1986). Those that have done so, have often dealt with small 

branch wood (e.g., Abbott and Crossley 1982; Swift and 

others 1976) or failed to identify the insect community 

structure or abundance. However, Ausmus (1977) 

considered insects in studies of large woody debris and 

concluded that they were a key component regulating 

decomposition. 

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Brigham Young University. 685 p. 

Wood, T.G. 1976. The role of termites (Isoptera) in decomposition 

processes. In: Anderson, J.M.; MacFadyen, A., eds. The role of 

terrestrial and aquatic organisms in decomposition processes. Oxford: 

Blackwell Science Publishers: 145- 168. 

Wood, T.G. 1978. Food and feeding habits of termites. In: Brain, M.V., 

ed. Production ecology of ants and termites. New York: Cambridge 

University Press: 55-80. 

Wood, T.G.; Sands, W.A. 1978. The role of termites in ecosystems. In: 

Brian, M.V., ed. Production ecology of ants and termites. New York: 

Cambridge University Press: 245-29 2. 

Thatcher, R.C. 1960. Bark beetles affecting southern pines: a review of 

current knowledge. New Orleans, LA: Occasional Paper No. 180. U.S. 

Department of Agriculture, Forest Service, Southern Forest 

Experiment Station. 25 p. 
Appendix 

A partial listing of the wood-feeding insects of the Southem United States with notes on their hosts and habits 

- 

Species Habits 

Order Isoptera: 

Kalotemitidae 

Kalotermes approximatus 

Neotermes jouteli 

N. luyktci 

N. castaneus 

Incisitermes snyderi 

I. milleri 

I. schwarzi 

Calcariternes nearcticus 

Cryptotermes brevis 

C, cavifrons 

Prorhontermes simplex 

Reticulitemes flavipes 

R. hageni 

R. virginicus 

R. tibialis 

Coptotermes fornosanus 

Order Coleoptera: 

~colytidae3 

Hylastes tenuis 

H. exilis 

H. salebrosus 

H. porculus 

Hylesinus pruinosus 

H. aculeatus 

H. fasciatus 

Hylurgopinus rufipes 

Bendroctonus frontalis 

D, terebraas 

I>. valens 

B. punctatus 

Cnesinus strigicollis 

Phloetribus Eiminaris 

I? frontalis 

I? dentifrons 

I? texanus 

Pinus spp. 

Pinus spp. 

Pinus spp. 

Pinus spp. 

Fraxinus spp. 

E americana 

Fraxinus spp. 

Ulmus spp. 

Pinus spp. 

Pinus spp. 

I? sstobus, I? rigida, I? echinata, 

I? virginiana, Picea rubens 

I? rubens 

Quercus spp., Liquidambar 

siryraciflua 

Prunus serotina 

Celtis occidentalis, Morus rubra 

C. occidentalis 

C. laevigata 

Drywood 

Drywood (Florida only) 

Drywood 

Drywood (Florida only) 

Drywood 

Drywood 

Drywood 

Drywood (Florida only) 

Drywood (Florida, Louisiana) 

Drywood (Florida only) 

Subterranean (Florida only) 

Subterranean 

Subterranean 

Subterranean 

Subterranean (Arkansas, Texas) 

Subterranean (introduced, 

widely established) 

Roots 

Stumps & roots 

Stumps & roots 

Stumps & roots 

Phloemletch wood 

Phloemfetch wood 

Phloemletch wood 

Phloemletch wood 

Phloem 

Phloem 

Phloem 

Phloem 

Outer xylem, small 

branches 

Phloemletch wood 

Phloemfetch wood 

Phloemfetch wood 

Phloemletch wood 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued). 

Species Hosts Habits 

Phloeosinus taxodii taodii 

R dentatus 

Chramesus subopacus 

C. hicoriae 

C, chapuisi 

Carphoboms bifircus 

Polygraphus rujpennis 

Scolytus rugulosus 

S. muticus 

S. fagi 

S. quadrispinosus 

S. multistriatus 

Pseudothysanoes lecontei 

I? dislocatus 

Thysanoes pallens 

I: bercherniae 

I: fimbricomis 

I: lobelli 

Micracis swdinei 

M suturalis 

Iijllocuris binodatus 

H. rudis 

H. torosus 

H. bicornus 

H hamedi 

H: spadix 

Hylocuris langstoni 

Pityogenes hopkini 

f? meridianus 

l? plagiatus 

Orthotowticus caelatus 

Ips avulsus 

I. pini 

I. calligraphus 

I. grandicollis 

Lymator decipiens 

Taxodium distichum 

Juniperus virg iniana 

Celtis sp. 

Carya spp. 

C. occidentalis, Robinia sp. 

I? echimta, R taeda, I? virginiana 

I? strobus, I? rubens, Abies fraseri 

Prunus spp,, Ulmus spp. 

C. occidentalis 

Fagus grandfolia, Celtis sg. 

Carya spp. 

Ulmus spp. 

Castanea dentata, Celtis sp., 

Quercus spp. 

Carya spp. 

Carya spp., Quercus spp. 

Quercus sp., Ulrnus sp. 

A. rubrum, Carya spp., Celtis sp., 

M. rubra, Quercus spp., Gleditsia 

tricanthos 

Carya sp., Quercus sp. 

Cercis cadensis, Populus sp., 

Salix spp. 

C. canadensis 

Carya sp. 

Carya spp., F: grand$olia, 

U. americana 

Carya sp., Celtis sp., Ace6 

C. Itentata 

Carya sp. 

Caqa sp. 

Carya spp. 

Celtis sp., Ulmus sp. 

f? strobus 

I? taeda 

f? echinata, l? virginiana 

Pinus spp., Picea spp. 

Pinus spp. 

14 strobus 

Pinus spp. 

Piplus spp, 

A, rubrum, A. sacchamm, 

Salix sp. 

Phloedetch wood 

Phloemletch wood 

Phloedetch wood larvae 

may enter wood completely 

Phloedetch wood larvae may 

feed on wood exclusively 

Phloedetch wood 

Phloem 

Phloem 

Phloedetch wood 

Phloedetch wood 

Phloedetch wood 

Phloedetch wood 

Phloedetch wood 

Phloem 

Phloem 

Wood of small branches 

Wood of small branches 

Wood of small branches 

Wood of small branches 

Wood of branches 

Wood (all areas of tree) 

Wood 

wood 

Wood 

wood 

Wd 

Wood 

Phloem 

Phloem 

Phloem 

PNoedetch wood 

Phloedetch wd 

Phloedetch wood 

Phloedetch wood 

Wood of dry branches 
A partial listing of the wood-feeding insects of the Southem United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Dryocoetes autographus 

D. betulae 

D. grandicollis 

D. afaber 

D. caryi 

Crypturgus alutaceus 

Xyloterinus politus 

Trypodendron scabricollis 

I: retusum 

liT lineatum 

Xylosandrus crassiusculus 

X. germanus 

Xyleborus obesus 

X. dispar 

X. sayi 

X. obliquus 

X. rubricollis 

X. lecontei 

X. tachygraphus 

X. afinis 

X. celsus 

X. viduus 

X. qlographus 

X. pubescens 

Cryphalus rubentis 

C, ru$collis fraseri 

li-ischidias atom 

l? strobus 

Betula spp., E grandifolia, 

L. styraciflua 

Picea spp. 

l? rubens, A. fraseri, 

I? strobus 

l? rubens 

l? echinata, 19 palustris, 

l? taeda 

Ace6 Betula, Carya, Castanea, 

Fagus, Fraxinus, Quercus, Ulmus 

l? echinata, l? taeda 

Populus deltoides 

Abies spp., Picea spp., Pinus spp., 

Thuja spp.,Tsuga spp. 

Prunus spp., L. styraciflua, 

many other hosts 

Acer sp., Carya sp., Cornusflorida, 

Fraxinus sp., Juglans sp., L. tulipifera, 

Pinus sp., Prunus sp., Quercus spp., 

Ulmus spp. 

F: grandifolia, Quercus sp. 

A, saccharum, C. dentata, 

Juglans sp., Prunus sp., 

Quercus spp., Salix sp. 

A. rubrum, Acer sp. Castanea spp., 

Nyssa sp., Sassafras albidium 

Betula sp., C. dentata 

Carya, Cornus, Prunus, Quercus spp. 

Carya sp. 

Betula sp., Carya sp., C. dentata, 

Juglans sp. 

248 host species 

Carya sp. 

Broadleaf trees 

Quercus spp. 

Pinus spp. l? echinata, l? palustris 

l? rubens 

A. fraseri 

A. rubrum, Carya spp., C. dentata, 

Salix sp., R. pseudoacacia, U. 

americana 

Phloem 

Phloem 

Phloem 

Phloem 

Phloem 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetle 

Ambrosia beetle in 

branches 3-5 cm 

Ambrosia beetle 

Ambrosia beetle 

Ambrosia bettles 

Ambrosia bettles 

Ambrosia beetle 

Phloem 

Phloem 

Phloem branches 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued). 

Species Hosts Habits 

Hypothenemus dissimilis 

H. rotundicollis 

H. interstitialis 

H. crudiae 

H seriatus 

H. eruditus 

If. columbi 

Pseudopityophthorus asperulus 

l? pubescens 

l? fagi 

l? minutissimus 

l? pruinosus 

Pityophthorus angustus 

l? cariniceps 

l? pulchellus 

l? con.sus 

l? annectens 

l? consimilis 

I! liquidamburus 

Pityoborus cornatus 

Gnathotrichus materiarius 

Monarthrum mali 

M. fasciatum 

Corthylus punctatissimus 

C. columbianus 

A. rubrum, Carya spp., C. canadensis, 

Quercus spp. 

C. canadensis, I;: grandifolia, 

Quercus sp. 

A. rubrum, Aesculus sp., Carya spp., 

C. canadensis, E grandifolia, L. 

styraciflua, M. rubra, Quercus spp. 

Betula sp., Carya spp., J. nigra, 

l? taeda, Quercus spp. 

Carya spp., J. nigra, L. styraciflua, 

l? spp., Quercus spp. 

Several hundred hosts 

Quercus spp., Salix sp. 

Quercus sp., Ostrya virginiana 

Quercus alba, Q. rubra, C. dentata 

E grandifolia 

Quercus spp. 

Quercus spp. 

I? rubens, l? strobus 

l? strobus 

l? palustris, l? strobus, l? virginiana 

l? echinata, l? taeda 

I! palustris, l? taeda, Pinus spp. 

Pinus spp., l? strobus, I? virginiana, 

Picea spp. 

Pinus spp. 

A. saccharurn, C. canadensis, Picea sp., 

l? strobus 

L. styraczpua 

Pinus spp. 

I! echinata, I! strobus, I! taeda 

A. rubrum, L. styraciflua, Njtassa sp., 

Quercus rubra, Elia sp. 

A. rubrum, Carya sp., C. dentata, L 

styraclgua, Pinus sp., Prunus sp., 

Quercus spp. 

A. saccharinurn, Sassafras sp. 

A. rubrum, A. saccharinum, C. dentata, 

L.tulipifera, Plantanus occidentalis, 

Q. alba, Ulmus sp. 

Wood of small branches 

Wood of small branches 

Wood of small branches 

Wood of small branches 

Wood of small branches 

Phloem or pith 

Wood of small branches 

Phloem, entire tree 

Phloem 

Phloem (?), rare species 

Phloem of limbs & branches 

Phloem of limbs & branches 

Phloem, small branches 

Phloem throughout tree 

primarily branches 

10-25 cm phloem 

Branches phloem 

Small branch 2 cm 

Stems 2-8 cm 

Stems 6-20 cm 

Phloem & etch wood branches 2-8 cm 

Ambrosia beetles throughout stem 

Ambrosia beetle in 2-10 cm diarn. 

Ambrosia beetle in branches 

> 10 crn 

Ambrosia beetle in stems 

Ambrosia beetle, attacks boles of 

living trees 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Parandra polita 

I? brunnea 

Stenodontes dasytomus 

dasytomus 

Derobrachus brevicollis 

Orthosoma brunneum 

Prionus pocularis 

l? laticollis 

I? imbricomis 

I? debilis 

Derancistrus taslei 

Spondylis upifomis 

Scaphinus muticus 

Arhopalus rusticus obseletus 

A. rusticus nubilus 

Asemum striatum 

A. australe 

Atimia confusa confusa 

iMichthisoma hetemdoxum 

Smodicum cucujifome 

Oeme rigida rigida 

Methia pusilla 

Achryson surinamum 

Gracilia minuta 

Eubaria distincta 

El. qdrigeminata 

E. taaldemani 

Tylonotus bimculatus 

Hesperophanes pubescem 

Purpuricenus aillaris 

l? hurneralis 

Fagus, Carya, Liriodendron 

Quercus, Populus, C. dentata, A, rubrum, 

lirilia, Liriodendron, U, americana 

Plantanus spp., Celtis spp., Quercus spp., 

Salix spp., L. styraciflua, Acer negundo 

Quercus spp. 

Juglans, Carya, Castenea, Quercus, Ace< 

Pinus, Tsuga 

Pinus spp. 

Populus spp., Quercus spp., Castanea, 

Tilia 

Quercus, Castanea, other hardwoods 

Quercus, Castanea, other hardwoods 

Quercus, Castanea, Fagus, Cercis 

Pinus, Abies 

Pinus spp. 

Pinus spp. 

Pinus spp. 

Picea spp., Pinus spp. 

? 

Juniperus spp., I: distichum, 

Thuja sp., Chamaecyparis 

Carya 

Robinia, Carya, Quercus, Fagus, 

Celtis, Salix, Populus 

I: distichum, J. virginiana 

T distichum 

C. laevigata, R. pseudoacacia 

Salix, Que~us, Aesculus, Betula 

? 

Fraxinus, Quercus, Carya, Robinia, 

Castanea, Ace< Gleditsia, Ulmus, 

Fagus, Prunus 

Salk, Ulmus 

Frainus spp., Betula, J, nigra, 

Cava, LiriocJendron, Ulmus 

? 

Carya spp., C. dentata, Quercus spp. 

Cay, Betula, Quercus, Castanea, 

M. rubra, R. pseudoacacia, C. 

canadensis? Acer 

3-4 yr. life cycle wood in 

contact with ground 

Heartwood of live & dead trees 

Wood dead several years in moist 

situations 

Dead pine logs 

Roots of living trees timber in 

contact with ground 

Roots of live trees 

Roots of live trees 

Breeds on dry, dead snag tops 

Probably on roots 

Habits unknown 

Bases & roots of dead pines 

Habits unknown 

Base of recently dead trees 

? 

Feed in phloem excavates wood to 

form pupal cell 

Sapwood & stumps 

Dry heartwood 

Phloem; mine pupal cell in wood 

Small branches 

Dead twigs & branches phloem 9 

Prefer dry, solid hemwood 

living or dead trees 

Under bark 

Beneath bark of living or dying 

trees, may enter wood 

Rare 

Girdle branches up to 5 crn 

Dead branches 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Knulliana cincta cincta 

K. cincta ochraesa 

Tragidion coquus 

Ba~le ignicollis australis 

Psyrassa unicolor 

I? pertenuis 

Stenosphenus pinorum 

S. notatus 

Enuphalodes hispicomis 

E. rufulus 

E. atomarius 

Elaphidion mucronaturn 

Elaphidionoides villosus 

E. parallelus 

Anelaphus pumilus 

A. inemis 

Heterachthes ebenus 

Ii, pallidus 

Curius dentatus 

Plectromems dentripes 

Obriums rufilum 

0. mculatum 

0. howdeni 

Plinthocoetium suaveolens 

suaveolens 

Dryobius sexnotatus 

Ornithia mexicana 

Pronocera collaris colaris 

Hylotrupes bajulus 

Semanotus litigiosus 

Semanotus ligneus ligneus 

Juglans, Carya spp., Castanea, 

Quercus spp., Celtis, Prunus, Salix 

Carya illinoensis, 0. virginiana 

Quercus spp. 

Pinus 

C. glabra, J. nigra, Quercus spp., 

Fagus sp., M rubra, C. canadensis, 

Prunus 

Carya, Prunus 

Carya spp. 

C. glabra, C. illinoensis, Celtis sp. 

Quercus spp. 

Quercus spp., Acer sp. 

Quercus spp., Castanea, Celtis, 

Juglans, Carya 

Quercus, Juglans, Cornus, Celtis, 

Morus, Ace6 Castanea, Populus, 

Liriodendron, Sassafras 

Many hardwoods Quercus, Carya, 

Castanea, Prunus, Gleditsia, Celtis, 

Ace6 Juglans, Ulmus, Cercis 

canadensis, Sassafras 

Carya, Juglans, Quercus, Prunus 

Quercus spp., Castanea, Carya, 

Ulmus, Elia 

Carya 

Pinus spp. 

Carya ovata, C. illinoensis, L. 

tulipifera 

Pinus spp., Taxodium distichum, 

Juniperus sp., Celtis 

Quercus sp., C. illinoensis 

fiminus 

Carya, Quercus, Celtis, Morus, Cercis 

? 

Morus sp. 

Ulmus, Acel; Fagus, K americana 

C. laevigata 

Picea spp., Pinus spp. 

Pinacecle 

Tsuga 

J. virginiana, Chamecyparis 

Dry wood of dead branches and 

limbs 

Dead branches 

Dead branches 

Twig pruner 

Twig pruner 

Habit unknown 

Phloem and etch wood of dead 

limbs, pupates in wood 

May kill trees, living trees 1st yr. in 

phloem; 2nd year in wood 

Phloem at base of dead trees, 

pupates in sapwood 

Phloem and xylem of dead 

branches 

Girdles branches up to 5 cm 

dim. 

Twig or branch pruners 

? 

Dead & dying branches 

Dead branches of pine 

Wood 

Phloedetch wood 

? 

Wood of dead & dying branches 

? 

Trunk & root borers 

? 

Under loose bark 

? 

Dry seasoned coniferous wood 

? 

? 

thyoides, Thuja occidentalis 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Callidium antennatum 

antennatum 

C. texanum 

C. frigidium 

Phymatodes varius 

P, testaceus 

P, aereus 

Physocnemum andeae 

P, brevilineum 

I! violaceipenne 

Ropalopus sanguinicollis 

Megacyllene robiniae 

M. caryae 

Calloides nobilis nobilis 

Sarosesthes fulminans 

Xylotrechus sagittatus 

sag ittatus 

X. colonus 

X. integer 

Neoclytus scutellaris 

N. mucronatus mucronatus 

N. acuminatus acuminatus 

N. fulguratus 

N. caprea 

Clytus ruricola 

C. marginicollis 

Clytolepus albofasiatus 

Cyrtophorus verrucosus 

Microclytus gazellula 

Pinus spp., Picea 

J. virginiana 

J. virginiana, I: occidentalis 

Quercus spp., Carya 

Quercus spp., Carya, Fagus, 

Salix, Castanea, Prunus 

Quercus spp. 

I: distichum 

Ulmus spp. 

Q. alba 

Prunus spp. 

R. pseudoacacia 

Carya spp., Juglans spp., 

M. rubra, C. occidentalis, 

Ulmus, Fraxinus 

Quercus spp., Fraxinus sp. 

Castanea spp., Quercus spp. 

Pinus spp., Abies, Picea 

Quercus spp., Acel; Carya, 

Catanea, Fagus, Juglans, Fraxinus, 

Ulmus, Tsuga canadensis 

I: canadensis 

Quercus alba, Carya, Ulmus 

Carya 

Frainus, Quercus, Carya, Celtis 

Quercus spp. 

Frainus spp., Carya, Quercus spp., 

Ulmus 

Acer spp., Carya spp., Betula, 0. 

virginiana, Fagus, Quercus, 

I: americana 

Pinus spp. 

Carya 

Hardwoods in general 

Carya glabra, Quercus sp. 

Phloem, enter heartwood to 

pupate 

Phloem, enter heartwood to 

pupate 

Phloem 

Phloem, pupate under bark 

Phloem, pupate under bark 

Phloem, pupate in sapwood 

Phloem, pupate under bark 

Dead branches 

Phloem of living trees, enter 

heartwood to pupate 

Phloem & wood of living trees, 

kills trees 

Fresh cut wood 

Phloem, stumps & base of 

recently dying or dead trees; 

require high moisture 

Phloem, half grown larvae 

enter wood 

Phloem, half grown larvae 

enter wood 

Phloem only 

Phloem & wood preferred 

Most all hardwoods, in 

unseasoned wood 

Dry oak saplings 

Infest newly dead or dying 

trees, enter sapwood 

In decaying wood 

Phloem and xylem of dead 

branches 

Solid dead trees 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Euderces picipes picipes 

Rhopalophora longipes 

longipes 

Anycylocera bicolor 

Neocydalis mellitus 

Centrodera decolorata 

Anthophilax hofiani 

A. viridis 

Gaurotes cyanipennis 

Rhagium lineatum 

Bellamira scalaris 

Typocerus zebra 

I: velutinus 

I: lunulatus 

Leptorhabdium pictum 

Stenocorus cylindicollis 

Evodinus monticola 

monticola 

Arthophylax ho~ni 

A. attenuatus 

A. cyaneus 

Gaurotes cyanipennis 

Acmeops proteus 

A. discoideus 

Gnathacmeops pratensis 

Metacmeops vittata 

Stranglia luteicornis 

S, occidentalis 

S. acuminata 

Bellamira scalaris 

Analeptura lineola 

Charisalia americana 

Grammoptera subargentata 

Judolia cordgera 

J. montivagans montivagans 

Carya spp., J. nigra, 

Quercus spp., Wmus, Celtis, 

Cercis, Robinia, Njissa, Cornus 

C. canadensis 

Carya, Quercus 

Quercus, Castanea 

Quercus, Castanea, Liriodendron 

Picea, Abies 

Fagus, Betula, Acer 

Quercus, Juglans, Prunus 

Nyssa, Cornus 

All conifers 

Fagus, Acer; Populus, Pinus, Tsuga 

Pinus 

Hardwood or conifer 

Pinus 

Betula, Castanea, Cornus, Quercus, 

Carya 

Carya 

Tsuga, Abies, Picea, Pinus 

Picea sp., A. fraseri 

A. saccharinum, E americana, 

Populus, Betula, Ostrya 

Betula, Fagus, Castanea, Acer 

Cornus, Prunus, Quercus, Juglans, 

Nyssa, Castanea, Betula 

Pinus, Picea, Tsuga, Abies 

Pinus spp. 

Picea spp., Pinus spp. 

Liriodendron, Castanea 

Fagus, Ulmus, Quercus 

Ace6 Quercus 

Carpinus, Ostrya 

Populus, Fagus, Carya, Salix, 

Acer; Betula, Liriodendron, Pinus 

Betula, Ostrya, Carpinus, Pinus 

Liriodendron, Nyssa 

Populus, Quercus 

Castanea 

Abies, Pinus, Picea, Populus, Salix 

Phloem, pupate in wood 

? 

Solid dead wood 

In wet decaying wood 

Decaying logs 

Decaying logs 

Phloem 

Phloem of recently 

killed trees 

'Well rotted logs in 

very moist situations 

Mine dead roots 

Decaying wood 

? 

Phloem 

Very moist decaying logs 

? 

Phloem, pupate in soil 

Phloem 

Phloem 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Leptura emarginata 

L. sublamata 

Leptura abdominalis 

Trachysida mutubilis 

Pidonia ruficollis 

Strangalepta vittata 

S. pubera 

Xestoleptura octonotata 

Lepturopsis biforis 

Trigonarthris minnesotana 

T. proxima 

Brachyleptura rubrica 

B. vagans 

B. circumdata 

Strophiona nitens 

Neoptychodes trilineatus 

Hebestola nobulosa 

Plectrodera scalator 

Monochamus scutellatus 

scutellatus 

M. marnorator 

M. carolinensis 

M. titillator 

M. notatus 

Microgoes oculatus 

Goes dibilis 

Goes tiqrinus 

G. pulcher 

6. tesselatus 

G. pulverulentus 

Castanea, &us, Fagus, Quercus, ? 

Betula, Acer, Nyssa, Liriodendron 

Tsuga, Pinus 

T distichum, Juniperus 

Hxdwoods Decaying 

Castanea, Prunus, Betula, Populus, Elia 

Abies, Pinus, Picea, Juniperus, 

Tsuga, Populus, Acer, Betula, Castanea 

Ulmus, Juglans, Pinus 

Quercus 

Castanea, Populus, Pinus, Tsuga 

Nyssa, Betula, Prunus, Ulmus, 

ifilia, Acer, Populus, Carya, 

Fagus, Pinus 

Ace6 Carya, Castansa, ?%acr, 

Nyssa 

Carya, Fagus, Quercus, Prunus, 

Platanus, Castanea 

Pinus, Tsuga, Betula, Carya, 

Juglans 

Picea 

Quercus, Castanea, Carya, 

Juglans, Fagus 

Salix spp. 

Quercus, Castanea 

Populus, Salix 

Pinus, Abies, Picea 

I? rubens, A. balsamea 

Pinus 

Pinus, Picea 

l? strobus, Abies, Picea 

Cercis, Cornus, Populus, 

Quercus, Tilia, Wus, 

Castanea, Cava, Acer 

Quercus, Ca~ya, Castanea 

Quercus, Juglans, Carya, U%mus 

Quercus, Carya, Ulmus 

Quercus, Castanea, Ulinus 

Quercus, Fagus, Carpinus, 

Ulmus, Prunus, &tula, Ostrya 

M. rubra 

Carya, Celtis, Elia, 

Ace& Juglans 

Morus 

Heartwood of dying trees 

Phloem of live trees, often 

kill them, enter wood before winter 

Phloem, enter sapwood 

Phloem, enter sapwood 

Phloem, enter sapwood 

Phloem, enter sapwood 

Phloem, enter sapwood 

Phloem 

Small living branches 

Live trees, in wood 

Live trees, in wood 

Base and roots of saplings 

Live trees, in wood 

Phloem of living branches 

Dead limbs 1 - 10 cm, phlmm & 

wood 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Ataxia crypta Quercus, Castanea, Acer, Celtis, Dead branches 

Salix, Prunus 

Eupogonius subarmatus Tilia, Ulmus, Fagus, Prunus 

E. tomentosus Pinus, Picea ? 

E. pauper Acer, Calpinus, Carya, Castanea, 

Cercis, Cornus, Fraxinus, Juglans, 

Morus, Prunus, Quercus, Tilia, Ulmus 

Psenocerus supernotatus Cornus, Quercus, Carya, Castanea, Dead branches 

Liquidambar, Ulmus, Liriodendron, Salix 

Ecyrus dasycerus Castanea, Celtis, Robinia, nlia, 

Morus, Ulmus, Carya, Quercus, Prunus 

Pogonocherus mixtus Pinus spp., Picea, Salix 

Aegomorp hus quadrig ibbus Castanea, Fagus, Itilia, Acer, Carya, Decaying wood 

Cercis, Ulmus, Quercus, Betula, 

Tilia, Celtis 

A. nzorrisi Njssa, Liriodendron 

A. modestus Most hardwoods Decaying wood 

Arrhenodes minutus Q. alba Bore in heartwood 

lschnocerus infuscatus 

Ormiscus saltator 

Steremnius shermani 

Heilipus apiatus 

Eudociminus mnnerheimi 

Pissodes similis 

l? approximatus 

l? nemorensis 

f? fraseri 

Magda lis pe florata 

M. barbita 

M. amicollis 

M. olyra 

M. pandura 

M. incospicua 

Acamptus rigidus 

Dryophthorus americanus 

Deciduous trees 

Picea 

Pinus sp. 

I: distichum 

A, balsamea, A, fraseri 

f? strobus, f? virginiana, 

£? echinata 

Pinus spp. 

A, fraseri 

l? strobus 

uzmus spp. 

Ulmus spp. 

Carya, Quercus 

J. nigra 

Carya 

Pinus sp. 

In wood 

Under bark 

Phloem of dead & dying trees 

Phloem 

Phloem 

Phloem 

Phloem of dying trees 

Phloem 

Phloem 

Phloem 

Phloem 

Phloem 

Phloem 

Red rotten wood 

Phloem? 
A partial listing of the wood-feeding insects of the Southem United States with notes on their hosts and habits 

(continued) 

Species 

Himatinum conicum l? strobus 

Cossonus concinnus Carya sp., I! occidentalis, 

other hardwoods 

C. corticola Pinus spp. 

Allominus dubius 

Phloeophagus minor Betula, Salix, Ulmus 

Tomlips quercicola Fag us, other hardwoods 

Pentarthrinus pawicollis Various trees 

Rhynocolus oregonensis Pinus sp. 

Stenoscelis brevis Most deciduous trees 

Dorcus parallelus Quercus, Tilia, Acer 

Lucanus placidus Quercus sp. 

Lucanus elaphus 

Platycerus virescens Quercus spp. 

Cloetus aphodioides 

Acanthocerus aeneus 

Pelidnota punctata 

Parastasia brevipes 

Trichiotinus afinis 

I: bibens 

T. piger 

Osmodema eremicola 

0. scabra 

Strategus julianus 

Dynastes tityus 

Phileurus didymus 

Quercus, Carya, Ulmus 

Acer; Quercus, Celtis, Ulmus 

Quercus, Platanus 

Quercus, Carya 

Quercus 

Hardwoods 

Hardwoods 

Hardwoods 

Popillius disjunctus Hardwood stumps & logs 

Lyctus brunneus Quercus, Ulmus 

L. cavicollis Hardwoods 

L linearis Quercus, Carya, Juglans, Fraxinus 

L. planicollis Quercus, Frainus, Carya, Platanus 

lFogoxylon parallelopipedum Carya, L). virginiana, Quercus 

76 

In assoc, with Tomicus pini 

Phloem 

Beneath bark 

Under bark of dead & 

decaying trees 

Decaying wood 

Rotting wood 

Dead wood 

Phloem 

Rotten wood 

Decaying roots & stumps 

Decaying logs 

Rotten wood 

Decaying wood 

Rotten logs & stumps 

Rotten wood 

Rotten wood 

Decayed wood 

Decayed wood 

Decayed wood 

Decayed wood 

Decayed wood 

Decaying wood 

Decaying wood 

Decaying wood 

Adults feed young wood pulp 

Sapwood 

Wood 

Wood 

Wood 

Wood 
A partial listing of the wood-feeding insects of the Southem United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Bos trichidae 10 

Prostephanus punctatus 

Stephanopachys rugosus 

S. substriatus 

S. cribratus 

S. hispidulus 

Lichenophanes bicornis 

L amiger 

L. truncaticollis 

Seobicia bidentata 

Xylobiops basilaris 

Micromathidae 1 1 

Micromalthus debilis 

Hylecoetus lugubris 

Melittoma sericeum 

Platypodidaes 

P1at)lpusflavicornis 

I? quadridentatus 

I? compositus 

l? parallelus 

Anobiidae 1 2 

Coelostethus notatus 

Xyletinus peltatus 

Eucrada humeralis 

Xestobium rufovillosum 

Emobius motlis 

E. filico rnis 

E. granulatus 

E. tenuicornis 

Carya, Quercus 

Pinus spp. 

?: canadensis, Pinus spp., 

Abies spp. 

?? taeda, I? strobus 

?? taeda, £? virginiana 

Celtis, Quercus, Carya, 

Fagus, Ulmus 

Quercus 

Carya 

Carya, C. dentata 

Quercus spp., Fraxinus sp. 

D. virginiana, Carya alba, 

U. americana, R. psuedoacacia 

Quercus, Castanea 

Hardwood 

Hardwood 

Pinus spp. 

Quercus spp., many 

other hardwoods 

Many hardwoods 

Hardwoods 

Quercus 

Quercus, Fagus 

Picea, Quercus, Pinus spp. 

Pinus spp. 

Pinus spp.? 

Pinus spp.? 

Pinus spp.? 

Dead roots & stumps 

Wood 

Wood 

Wood 

Wood 

Dead bark & wood 

Wood 

Wood 

Wood 

Wood 

Wood feeders, advanced decay 

Decaying wood 

Decaying wood 

Base of tree, ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles 

Ambrosia beetles restricted 

to Florida & Texas 

Branches 

Damp wood 

Phloem 

Dry wood 

Wood 

? 

? 

? 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Oligomerus sericans 

0. obtusus 

0, brevipilis 

0. alternans 

Trichodesm relagesi 

Anobium punctatum 

Platybregmus canadensis 

Hadrobregmus carinatus 

H. linearis 

H. pusillus 

H. umbrosus 

Trp'popirus sericeus 

Ptilinus ruficornis 

P. pruinosus 

Xanthochroa trinotata 

X. erythrocephala 

Nacerdes melanura 

Heliocis repanda 

Oxacis floridana 

Oxacis cana 

Oxacis taeniata 

Oxacis notoxoides 

0. thoracia 

0. suturalis 

0. mimetica 

0. recendita 

0. interrita 

Alloxacis pleuralis 

A. Joridana 

A. dorsalis 

A. ignota 

Asclera ruf-rcollis 

A. puncticollis 

Carya, Q. alba 

? 

? 

? 

Carya 

Many hosts 

Ace4 Tilia, Ulmus 

Ace4 Fagus 

Hardwoods 

Hardwoods 

Hardwoods 

Quercus, Prunus, Carya 

Hardwoods 

? 

Aemaeodera ornata Carya, Robinia 

A. pulchella 7: distichum 

A. tclbulus Carya, Q. alba, C. canadansis 

Ptosima gibbicollis C. canadensis 

Chalcophora virginiensis Pinus spp. 

C. georgiana Pinus spp. 

Wood 

? 

? 

? 

? 

Wood 

Wood 

Wood 

Wood 

Wood 

Wood 

Dead branches, wood 

Wood 

? 

? 

? 

Wood in water or subject 

to flooding 

? 

? 

? 

? 

? 

? 

? 

? 

? 

? 

? 

9 

Dirt & wood 

? 

9 

Heartwood of living trees 

Logs and stumps, wood 

Logs and stumps, wood 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued) 

- 

Species Hosts Habits 

Chalcophorella campestris 

Trachykele lecontei 

Dicercu divaricata 

D. punctulata 

D. obscura 

D. lurida 

0. lepida 

D. tenebrosa 

D. tuberculata 

D. americana 

Cinyra garclipes 

Buprestis striata 

B. aprican 

B. decora 

B. salisburyensis 

B. lineata 

B. maculipennis 

B. rufipes 

B. faciata 

Xenorhipis brendeli 

Malanophila aeneola 

M. obtusa 

M. notata 

M. opaca 

M. acuminata 

Anthia viridifrons 

A. viridicomis 

A. quercata 

Agrilaxia flavimana 

Chrysobothris chrysoela 

C. sexsignata 

C. scitula 

C. azurea 

C. texana 

C. pusilla 

C. dentipes 

C. floricola 

C. femorata 

Fagus, Salix, Plantanus, Elia 

I: distichum 

Prunus, Acer, Elia, 

Betula, Quercus, Ulmus 

Pinus spp. 

Carya, Ace6 Q. alba 

Carpinus sp. 

Ostrya spp. 

Pinus, Picea 

I: canadensis 

Pinus spp. 

Quercus, Fraxinus 

Pinus sp., Tsuga spp. 

Pinus spp. 

Pinus spp. 

I? rigida 

Pinus spp. 

Pinus, Tsuga, Taxodium 

Ulmus, Fagus, Carya, Quercus, 

Ace6 Castanea, Liriodendron 

Pinus spp. 

Quercus nigra 

Pinus spp. 

? 

? 

? 

Pinus, Picea, Abies 

U. americana, Carya 

Salix 

Cercis, R strobus, Castanea, 

Q. nigra 

Q. alba 

I: distichum 

Tsuga, Frminus alba, 

A, rubrum, J. nigra, 

Quercus spp., Fagus, Betula 

Quercus 

Carya, Ace4 Quercus, Pinus, 

C. florida, Tilia, Salix 

Pinus spp. 

Pinus spp. 

Pinus spp. 

Many hardwoods 

Moist decaying hardwood logs 

Sap and heartwood 

Wood of wounded trees 

Decaying wood 

Branches, heartwood 

Phloem & sapwood 

? 

? 

? 

Dead branches 

Dead & dying 

Sapwood & branches 

Sapwood 

Dead branches 

Cedar 

Sapwood 

Phloem 

Phloem feeder on damaged 

or scarred trees 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Chrysobothris. rugosiceps 

C. adelpha 

C. viridiceps 

C. harrisi 

Actenodes acornis 

A. auronotata 

Agrilus bilincatus 

Agrilus facipennis 

Agrilus masculinus 

A. defectus 

A. cephalicus 

A. fallax 

A. otiosus 

A. politus 

A. obsoletoguttatus 

A. lecontei 

A. celti 

A. quadriguttatus 

Mastogenius subcyaneus 

Order Lepidoptera: 

Noctuidae15 

Scolecocampa liburna 

Synanthedon scitula 

S. acerni 

S. pini 

S. gelifomis 

S. acerrubri 

S. castaneae 

S. rubrofascia 

S. sigmoidea 

S. proxima 

S. bolterd 

Sannina uroce rifrons 

Podosesia syringae 

I? aureocinta 

Paranthrene simulans 

R dollii 

I? tabaniformis 

Castanea, Q. alba 

Carya 

A. rubrum, Quercus, Prunus 

I? virginiana, I? strobus, 

I? rigida 

A. rubrum, Carya, Quercus, 

Fagus 

i? distichum 

All Quercus spp., C. dentata 

I? virginiana 

A. rubrum, A. negundo 

Q. alba 

C. flo rida 

R. pseudoacacia, C. occidentalis 

Carya spp., other hardwood 

Salix 

Fagus, Carpinus, Quercus, Carya 

C. florida, C. occidentalis 

C. occidentalis 

Salix 

Quercus spp. 

Deciduous hardwood trees 

Acer spp. 

Pinus strobus 

C, fEorida, C. illinoensis 

Acer spp. 

Castanea sp. 

L. tulipifera 

Salix spp. 

Salix spp. 

Salix spp. 

D. virginiana 

Fraxinus spp. 

Fraxinus spp. 

Quercus spp. 

Populus deltoides, Salix spp. 

R deltoides 

Heartwood dead trees 

Dead 

Phloem of living weakened trees 

Sapwood 

Dead branches 

Moist, decayed logs 

Wood of living trees 

Live trees 

Phloem & sapwood 

Bark borer 

Bark borer 

Wood borer 

Bark borer 

Wood 

Wood 

Wood 

Wood 

Wood 

Wood 

Wood 

Wood 

Wood of branches 
A partial listing of the wood-feeding insects of the Southern United States with notes on their hosts and habits 

(continued) 

Species Hosts Habits 

Acossus populi 

Prionoxystus robiniae 

R macmurtrei 

Hymenoptera: 

Siricidaes 

Sirex edwardsii 

S. nigricornis 

Urocerus cressoni 

U. taxadii 

Tremex columba 

Eriotremex fornosanus 

Xiphy driidae 1 7 

Xiphydria hicoriae 

X. mculata 

X. tibiatis 

X. mellipes 

X. scaga 

Populus sp. 

Quercus spp., R. psuedoacacia, 

Ulmus spp., Acer spp., Salix spp., 

Populus spp. 

Quercus spp. 

I? rigida 

I? echinata, I? strobus, 

l? virginiana 

Picea, Abies, Pinus 

I: distichum 

Hardwoods 

Hardwoods 

Carya, Ulmus 

Acer spp. 

Ulmus, Betula, Fagus, 

Quercus 

Betula spp. 

Carpinus americanus 

Wood 

Phloem & wood 

Wood 

Wood 

Wood 

Wood 

Dead or weakened trees, 

wood 

Dead wood introduced sp. 

Wood of branches, boles 

Wood of dead limbs 

Wood of boles, branches 

Dead, decaying logs 

Dead, dry stems 

1 Nickle and Collins 1989; 2 Light 1934; 3 Wood 1982; Linsley 196 1, 1962a, 1962b, 1963, 1964, Linsley and 

Chemsak 1972, 1976, 1984; 5 Drooz 1985; ti Blatchley and Leng 1916; Anderson 1952; 8 Richter 1966; 9 Gerberg 

1957; la Fisher 1950; 11 Arnett 1968; 12 White 1962, 1971; 13 Amett 1951; l4 Franklin and Lund 1956; 15 Peterson 

1962; 16 Duckworth and Eichlin 1977; 17 Smith 1976. 
The Significance of Coarse Woody Debris for 

the Diversity of Soil Mites 

John M. Johnston and D.A. Crossley, Jr. 

Abstract 

The community of mites inhabiting forest floors is rich in species but is 

poorly known both taxonomically and biologicalfy. Understanding the 

relationship of mite species diversity to ecosystem function depends upon 

better knowledge of habitat and substrate use. Coarse woody debris 

(CWD) is a significant habitat variable as well as a resource for mite 

communities. However, little information has been developed on the use 

of woody debris by mites in southern forests. As a habitat variable, CWD 

is a contributor to the microenvironmental gradients that affect soil-mite 

distribution and abundance. As a resource variable, the importance of 

CWD resides in its support of a varied fungal population and its nutrient 

reserves. Calcium, abundant in the bark of decaying boles and twigs, is 

particularly important for Oribatid mites. 

general predators, and Prostigmata as specialized predators. 

However, these generalizations may lead to erroneous 

conclusions due to inadequate infomation on feeding habits 

or the specialized nature of some predator-prey relationships 

(Walter 1987, 1988). As concerns about the loss of 

biodiversity continue (Wilson 1992), and the relationships of 

biodiversity to ecosystem function become better 

understood (Schultze and Mooney 1993), increased 

attention to taxonomy and diversity of soil mites is needed. 

A necessary concomitant is the analysis of habitat use by 

soil mites, so that the importance of habitat features, such as 

coarse woody debris (CWD), can be quantified. 

Introduction 

Soil-dwelling mites reach their greatest abundance in the 

forest floors of temperate regions (Swift and others 1979). 

Mites are major participants in belowground food webs. 

Some species feed directly upon decomposing plant 

materials; more species are fungivores. Others are predators 

on other small arthropods or their eggs, nematodes, or other 

small fauna. Many species appear to be omnivorous, or at 

least to have the capacity to switch food sources, depending 

upon availability. A large diversity of mite species is 

characteristic of most soil systems. Indeed, mites are the 

most species-rich group of the North American soil 

arthropod fauna (Behan-Pelletier and Bissett 1992). 

Almost one-half of the soil mite species are unnamed; 

perhaps as few as one-third of North American species of 

soil mites have been adequately described and illustrated 

(Behan-Pelletier and Bissett 1992). Furthermore, 

immature stages are poorly known. Food habits for many 

species remain obscure, and observations on feeding 

reported in the literature often prove to be unreliable (Walter 

1988). 

For ecological analyses, soil mites may be arrayed into 

functional groups (Moore and others 1988) of soil food 

webs. Oribatid mites are generally considered as a 

fungivore-detritivore functional group, Mesostigmata as 

Research Assistant and Research Professor of Ecology, respectively, 

Institute of Ecology, University of Georgia, Athens, GA 30602-2602. 

Only a few scattered references can be found on the use of 

woody debris by mites in southern forests. This is 

surprising, given the number of studies of forest floor 

arthropods done in areas ranging from upland southern pine 

forests to rich bottomland hardwood forests. In this paper, 

we offer a preliminary interpretation of the importance of 

CWD for soil mite diversity, some directions for future 

studies, and some tentative considerations for management 

practices. 

Factors Affecting Spatial Distribution 

of Soil Mites 

Mite species have clumped (contagious) distributions in 

forest floor habitats. It is not clear what factors affect the 

spatial distribution of soil mites. Even a seemingly uniform 

forest floor under a pine monoculture will contain more than 

50 species of oribatid mites, and perhaps as many as 100 

total mite species. Since different oribatids appear to feed on 

the same foods, fungi andlor decaying organic matter, the 

coexistence of so many similar species seems unusual. Two 

factors have been suggested to explain this coexistence of 

similar species. One is seasonal separation. Research using 

litterbag methods to sample soil arthropods reveals a 

succession of reproductive success by oribatids during the 

year. Thus, some species of mites may be geared to a 

seasonal pattern of fungal species. 

Microhabitat differentiation is the other factor proposed to 

explain soil mite community structure. The uniform 

appearance of the forest floor may be deceiving to the casual 

eye: distances from tree boles, presence of understory, root 
distributions (Fitter and others 1985), and similar habitat 

variables make for a sequence of more-or-less-distinct 

microhabitats. These factors, coupled with the highly 

contagious spatial distributions of most oribatid mite 

species, led Anderson (1977) to propose that mites exist in a 

set of "unit communities" in the forest floor. Most mite 

species appear to be distributed across a variety of forest 

floor habitats. The presence of microhabitats probably 

contributes to the abundance and persistence of mite 

species. 

Relationship of Soil Mite Biodiversity 

to Coarse Woody Debris 

Coarse woody debris is a major habitat variable on forest 

floors (Wallwork 1976). It contributes to the 

microenvironmental gradients that affect the distribution and 

abundance sf soil mite species. Coarse woody debris in 

mature forests provides a set of microsites that offer food 

and habitat resources for unit communities of soil mites. 

Coarse woody debris is part of a woody continuum, starting 

with fine twigs and ranging through larger twigs and 

branches to boles. Fallen logs vary by species and by mode 

of decay. Fallen hardwood logs that are hollow support a 

rich mite fauna, as do basal tree-holes (Park and Auerbach 

1954). Tree-holes contain several unique species of 

mites (Camin 1953). 

Decaying woody debris is a significant nutrient sink in 

southern forest floors (Cromack and Monk 1975). 

Accumulations of calcium in the bark of decaying wood 

may be particularly significant for Diplopoda (millipedes) 

and for oribatid mite species, which use calcium oxalate or 

calcium carbonate as cuticular hardening agents (Norton and 

Behan-Pelletier 1991). Oribatid mites accumulate calcium 

compounds from a fungal diet (Cromack and others 1977). 

The food base for most oribatid mites consists of fungal 

hyphae, although some species appear to use leaf litter or 

woody materials directly. This aspect of nutrition has been 

termed the "peanut butter sandwich" problem. Do you eat 

the entire sandwich just to get the peanut butter (the 

microbes) in the sandwich (the decaying substrate)? 

Effects of CWD on microclimate are important during 

drought conditions. Soil fauna are notoriously moisture 

dependent. Fallen logs offer protection from desiccation, 

since the soil beneath logs remains moist after the forest 

floor has dried. Accumulations of macrofauna and 

microarthropods under logs are commonly noted during 

droughts. Nocturnal macrofauna, that is, cryptozoa such as 

thysmurans and scorpions, use fallen logs or stumps as 

daytime refuges, but such behavior has not been recorded 

for mites in southern forests, 

Finally, CWD offers a somewhat distinct habitat feature on 

the forest floor. Fallen logs support lichen populations and 

fungal structures that are absent or not abundant in leaf 

litter. Mites, which can penetrate fallen logs either through 

openings made by insects or as phoretic passengers on 

insects, find a unique habitat. Some mite species are 

obligate members of the intra-log community. 

Use of Coarse Woody Debris 

by Soil Mites 

Given the importance of CWD as a habitat factor and a set 

of resources, it is not surprising that a large number of mite 

species use it (tables 1 and 2). Most of the oribatid mites 

that occur in the forest floor will, at some time, be found in 

decaying logs. Seastedt and others (1989) found that 

oribatid mites in forest floors in the Cascade Mountains of 

central Oregon used both decomposing wood and leaf litter, 

although mite species diversity in wood was much lower 

than in litter. Table 1 shows the presence of oribatid mites 

in soil cores, experimentally bagged leaf litter, and woody 

debris on the forested floors of hardwood watersheds at 

Coweeta Hydrologic Laboratory, Macon County, North 

Carolina. Despite the uneven sampling effort (5 to 6 times 

more woody samples examined than other types), it would 

appear that the majority of oribatid species living in the soil 

use both leaf litter (judging by the litterbags) and woody 

litter. A few abundant soil forms (e.g., Ceratozetes spp., 

Eremobodes sp., Oppia minus) appear to use neither recent 

leaf litter nor wood. Others (Oppiella nova, other species of 

Oppiidae, Suctobelbidae spp., Tectocepheus velatus, 

Trhypochtonius americanus) seem to be litter feeders. Data 

suggest that species such as Carabodes spp. and Eupelops 

sp. use both wood and leaf litter. Among this group of 73 

species only "IAtropacarus sp., Camisia spinger; 

Nanhemnnia sp., Ommatocepheuspcellatus, Oribatula 

sp., Oripoda sp., and Scheloribates pa llid&s-appear to use 

CWD as a preferred habitat. 

Other mite groups found beneath bark of decaying chestnut 

oak (Quercus prinus) logs (table 2) are also common soillitter forms, at least for the most part. Most of the 

Prostigmata listed are predators. Eupodids are fungal 

feeders in the laboratoq. The Tetranychidae (red spider 

mites) and Tenuipalpidae (false spider mites) feed on green 

vegetation: they probably had fallen from tree foliage and 
Table 1-Oribatid mite species in hardwood forest floor habitats at Coweeta Hydrologic Laboratory, North Carolinaa 

Soil Litter Woody Soil Litter Woody 

cores bags litter cores bags litter 

Oribatid species (N = 57) (N = 78) (N = 300) Oribatid species (N=57) (N=78) (N=300) 

Adoribella sp. 

Aeroppia sp. 

Allodameus sp. 

Allogalumna sp. 

Anachipteria sp. 

Atopochthonius sp. 

Atropacarus sp. 

Austrocarabodes sp. 

Belba sp. 

Brachychthonius sp. 

Cateremeus sp. 

Camisia spinifer 

Carabodes spp. 

Carabodoides sp. 

Cepheus cepheiformis 

Ceratoppia bipilis 

Ceratozetes spp. 

Cultroribula juncta 

Damaeus grossmani 

Eobrachychthonius sp. 

Gracilis eohypochthonius 

Cylindrica epilohmannia 

Epilohmnnoides sp. 

Eremaeus sp. 

Eremobelba s p. 

Eremobodes sp. 

Eremulus sp. 

Eupelops sp. 

Euphthiracarus sp. 

Ferolocella sp. 

Fossermaeus sp. 

Gymnodamaeus sp. 

Hemileius sp. 

Heminothrus sp. 

Hermaniella sp. 

Hypochthoniella sp. 

Rufulus hypochthonius 5 

Machuella sp. 10 

Malaconothrus sp. - 

Metrioppia sp. 0 

Microtritia sp. - 

Multioppia sp. 0 

Elegantula nanhemnnia 8 

Neoribates sp. 0 

Nothrus sylvestris 2 

Ocellatus ommatocepheus 0 

Qphidiotrichus sp. 0 

Oppia durhamensis 8 

Oppia minus 146 

Oppiella nova 402 

Oppiidae spp. 44 

Oribatella spp. 48 

Oribatula sp. 31 

Oribotritia sp. - Oripoda sp. 1 

Parachipteria sp. 17 

Peloptulus sp. 4 

Phthiracarus sp. - Peltifer platynothrus 7 

Dep ressa p rotohlumma 0 

Quadroppia sp. 19 

Rhysotritia sp. - 

Scapheremeus sp. 0 

Pallidulus scheloribates - Suctobelbidae spp. 286 

irectocepheus velatus 142 

Topobates 0 

Americanus trhypochthonius 14 

Trimalaconothrus sp. - 

Xenillus sp. 0 

Xylobates sp. 3 3 

&chvatkiniella sp. 1 

Zygoribatula sp. 0 

Variates = number of individuals; N = number of samples examined. 

a Data from Abbott 1980. 

bSpecies lumped into a higher taxonomic category during analysis of soil core and litterbag samples. 
Table 2-Mites in the suborders Prostigmata and food resource (the "peanut butter") is often fungal hyphae, 

Mesostigmata found beneath bark of decaying chestnut oak and these occur on a broad variety of decomposing 

(Quercus prinus) logs at Coweeta Hydrologic Laboratory, substrates. Furthermore, twig litter or other fine litter occurs 

North Carolina throughout the forest floor and may provide an adequate 

resource for microarthropods that can use it. In laboratory 

studies, Hartenstein (1962) found nine species of oribatid 

Prostigmata Mesostigmata mites that appeared to feed directly on wood (including 

Alycus sp. 

Bdella sp. 

Bimichaelia sp. 

Biscirus sp. 

Cunaxa sp. 

Cyta sp. 

Dactyloscirus sp. 

Eupodes spp. 

Eustigmeus sp. 

Labidostomma mamillata 

Lorryia sp. 

Mullederia sp. 

Paralorria sp. 

Pediculaster sp. 

Penthalodes sp. 

Protereunetes sp. 

Pyemotes sp. 

Scutacarus sp. 

Spinibdella sp. 

Tenuipalpidae 

Tetranychidae 

Thoribdella sp. 

Eutrombicula alfreddugesi 

Tydeus sp. 

Zetzellia sp. 

Amblyseius sp. 

Ameroseius sp. 

Asca aphidoides 

Asca gmanni 

Calholaspis berlesei 

Dendrolaelaps sp. 

Discourella sp. 

Eviphis sp. 

Holaspina sp. 

Haploseius sp. 

Hypoaspis sp. 

Ltrsioseius sp. 

Neoparholaspulus hurlbutti 

Parasitus sp. 

Podocinum sp. 

Rhodacarus sp. 

Uropodidae 

Veigaia sp. 

Zercon sp. 

Data from Abbott 1980 and Crossley unpublished. 

taken refuge under the bark. The Mesostigmata listed are 

also predators, some common in forest canopies and forest 

floors (i.e., Amblyseius sp., Asca aphidoides). The chigger 

mite Eutrombicula alfreddugesi, which occurred under the 

bark of fallen chestnut oak logs at Coweeta (table 2), was 

not found beneath the bark of fallen logs in the Georgia 

Piedmont (Mallow and others 1984). But adults occurred in 

soil beneath fallen pine logs, and questing larvae were found 

on the surface of those logs (see below). 

Such a broad distribution of soil mites across habitats has 

been noted by others. Anderson (197'7) suggested that the 

phenomenon, like the clumped or disjunct spatial 

distributions, may be one of scale. In particular, sampling 

methods may not be suited to microarthropods whose 

habitat scale is much smaller than the sampling tools. The 

Camisia spinifer; Ceratozetes gracilis, and Nanhermannia 

elegantula; see table 1). 

In contrast, certain soil mites use CWD as substrate or 

habitat in specific ways. The oribatid mite Ommatocepheus 

ocellatus, listed in table 1 as very abundant in chestnut oak 

logs, is arboreal as well. The fallen log habitat evidently is 

in some way similar to standing tree trunks. Another 

arboreal species, Humerobates-rostrolamellatus, occurs on 

tree trunks and fallen logs in southern pine forests. This 

species is viewed as a bioindicator of airborne pollution in 

European forests (Andre and others 1984). One genus of 

trombidiid mites ("velvet mites"), Neotrombidium, lives in 

cracks in the wood of standing snags or on the vertical walls 

of hollow logs. Trombiculid mites, the adult stages of 

"chigger" mites, use rotting hardwood logs, where they are 

predaceous on other small arthropods. Hollow hardwood 

logs are especially important as habitats for the adult stages 

of Eutrombicula species, our common pest chiggers. In 

south Georgia (Glynn County), fallen logs and tree stumps 

were the major habitat for Eutrombicula splendens. In 

Georgia Piedmont habitats, a notable association occurs 

between lizards (Sceloporus), chigger mites (E. 

alfreddugesi), and fallen pine logs. Adult mites are found 

in soil at the base of the logs. Larval stages seeking a host 

ascend to the top surfaces of the logs, where lizards sunning 

themselves are susceptible to parasitism (Mallow and others 

1984). 

Other mites may use hollow, rotten logs. The chigger mite 

Fonsecia gurneyi is a parasite of snakes (Elaphe spp., for 

example). Adult Fonsecia are predators; the larvae 

parasitize snakes that enter hollow logs. 

Mites may enter decaying CWD as phoretic forms-as 

inactive passengers on boring insects. Passalid beetles or 

"Bessy bugs," (Popilius dis~unctus) carry several species of 

mites with them. Colonies of mites then develop among the 

macerated wood and feces of these semisocial insects 

(Hunter arid Davis 1965). Wood feeding (or wood and fungus 

feeding) oribatid mites in the genus Mesoplophora are able to 

clasp the setae of passalid beetles and thus accompany them 

into decomposing logs (Norton 1980). 
Conclusions and Recommendations 

Coarse woady debris on forest floors has a significant 

impact on the distribution and abundance of soil mite 

species, Furthemore, some species of mites use CWD 

exclusively. However, the major importance of large 

branches and fallen logs in forest floor habitats appears to 

be that of a refuge for mite species normally occurring in 

litter or F layers. This importance likely increases in times 

of drought and perhaps under other conditions of stress. 

Harvesting and site preparation both have a profound effect 

on the distribution of woody debris. Often, slash piles are 

created that consist of a mixture of soil, humus, and woody 

material. Although these piles usually do not persist for 

more than a few years, they are nonetheless an overlooked 

and possibly important aspect of arthropod dispersal and 

survival. 

Fire, both natural and implemented as a management tool, 

also affects arthropod populations. Depending on the 

severity of the fire, varying amounts of the litter, 

fermentation, and humus layers are removed. Sites that are 

burned initially to control hardwood competition may be 

recolonized at a more rapid rate if woody debris serves as a 

refuge. Loblolly pine stands in the Coastal Plain often 

receive prescribed fuel-reduction burns every 3 to 5 years 

until the final harvest. Although CWD is largely absent from 

managed stands with a rotation age of 30 years, woody 

debris may yet play a key role in these frequently disturbed 

systems if it is introduced or purposely generated. 

The arthropod fauna of CWD in southern forests has 

virtually gone unstudied. Research efforts should be 

directed toward investigating this fauna, with an objective of 

determining whether unique species are associated with 

woody debris, especially in old-growth forests. Special 

attention should be directed toward older logs, hollow logs, 

and basal tree holes. These are most likely to shelter unique 

species of soil mites. 

Management practices aimed toward protecting the 

biodiversity of soil fauna should consider the placement of 

logs in even-aged pine stands. The geometry and relative 

distance of logs may be important considerations, since the 

scale of these organisms is a significant factor. Certainly 

hardwood logs that are undergoing decomposition should be 

protected. Hollow logs and trees containing basal tree-holes 

might be singled out for protection as well. 
Literature Cited 

Abbott, David Thomas. 1980. Wwdy litter decomposition at Coweeta 

Hydrologic Laboratory, North Carolina. Athens, CA: University of 

Georgia. 136 p. Ph.D. dissertation. 

Anderson, J.M. 1977. The organization of soil communities. In: Lohm, 

U.; Persson, T., eds. Soil organisms as components of ecosystems. 

Ekol. Bull. 25, Stockholm, Swedish Natural Science Research Council: 

15-23. 

Andre, H.M.; Lebrun, Ph.; Masson, M.; Sartor, F. 1984. On the use of 

Humerobates rostrolamellatus (Acari) as an air pollution bioassay 

monitor. The incidence of SO,-NO, synergism and of winter 

temperature. Science of the Total Environment. 39: 177- 187. 

Behan-Pelletier, V.M.; Bissett, B. 1992. Biodiversity of nearctic soil 

arthropods. Canadian Biodiversity. 2:5-14. 

Camin, J. H. 1953. Metagynellidae, a new family of uropodine mites 

with the description of Metagynetla parvula, a new species from tree 

holes. Bulletin of the Chicago Academy of Sciences. 9(18):391-409. 

Cromack, K., Jr.; Monk, C.D. 1975. Litter production and 

decomposition in a mixed hardwood watershed and a white pine 

plantation. In: HowelI, F.G.; Smith, M.H., eds. Mineral cycling in 

Southeastern ecosystems. Washington, DC: ERDA Symposium Series 

CONF-7405 13: 609-624. 

Cromack, K., Jr.; Sollins, P.; Todd, R.L. [and others]. 1977. Soil 

microorganism-arthropod interactions: Fungi as major calcium and 

sodium sources. In: Mattson, W.J., ed. The role of arthropods in forest 

ecosystems. New York: Springer-Verlag: 78-84. 

Fitter, A.D.; Atkinson, D.; Read, DJ.; Usher, M.B., eds. 1985. 

Ecological interactions in soil. Plants, microbes and animals. Oxford: 

Blackwell Science Publishers. 45 1 p. 

Hartenstein, R. 1962. Soil Oribatei. I: Feeding specificity among forest 

soil Oribatei (Acarina). Annals Entomological Society of America. 

55:202-206. 

Hunter, P.E.; Davis, R. 1965. Mites associated with the passaius beetle. 

111. Life stages and observations on the biology of Euzercon latus 

(Banks) (Acarina: Euzerconidae). Acarologia. 7(1):30-42. 

Mallow, D.; Ludwig, D.F.; Hayes, MJ,; Crossiey, D.A., Jr. 1984. 

Habitat selection of postlarval Eutrombicula a&eddugesi and 

Eutrombicula splendens from eight microhabitats in Georgia, U.S.A. 

(Trombiculidae: Acarina). Journal of the Georgia Entomological 

Society. 19543-548. 

Moore, J.C.; Walter, D.E.; Hunt, H.W. 1988. Arthropod regulation of 

mesobiota in below-ground detrital food webs. Annual Review of 

Entomology. 33:4 19-439. 

Norton, Roy A. 1980. Observations on phoresy by oribatid mites (Acari: 

Oribatei). International Journal of Acarology. 6: 12 1 - 130. 

Norton, Roy A,; Behan-Pelletier, Valerie M. 1991. Calcium carbonate 

and calcium oxalate as cuticular hardening agents in oribatid mites 

(Acari: Oribatei). Canadian Journal of Zoology. 69: 1504- 15 1 I. 

Park, Orlando; Auerbach, Stanley. 1954. Further study of the tree-hole 

complex with emphasis on quantitative aspects of the fauna. Ecology. 

35:208-222. 

Schultze, Ernst-Detlef; Mooney, Harold A., eds. 1993. Biodiversity 

and ecosystem function. Berlin: Springer-Verlag. 530 p. 

Seastedt, T.R.; Reddy, V.M.; Cline, S.P. 1989. Microarthropods in 

decaying wood from temperate coniferous forests. Pedobiologia. 

33:69-77, 

Swift, M J.; Heal, O.W.; Anderson, J.M. 1979. Decomposition in 

terrestrial ecosystems. Berkeley, CA: University of California Press. 

372 p. 

Wallwork, John A. 1976. The distribution and diversity of soil fauna. 

London: Academic Press. 355 p. 

Walter, D.E. 1987. Life history, trophic behavior and description of 

Gamasellodes vermivorax n. sp. (Mesostigmata: Ascidae), a predator 

of nematodes and arthropods in semiarid grassland soils. Canadian 

Journal of Zoology. 65: 1689- 1695. 

Walter, D.E. 1988. Predation and mycophagy by endeostigmatid mites 

(Acarifomes:Prostigmata). Experimental and Applied Acarology. 

4:159-166. 

Wilson, Edward 0. 1992. The diversity of life. Cambridge, MA: 

Belknap Press. 424 p. 
Collembolans and Coarse Woody Debris 

in Southern Forests: Effects on Biodiversity 

Richard J. Snider 

Abstract 

Knowledge of the Southern collembolan fauna is fragmentary and little is 

known of collembolan interaction with coarse woody debris (CWD). In 

successional colonization of CWD, collembolan are viewed as secondary 

invaders from the soil-litter subsystem. They have been found in both 

oak and pine subcortical zones during the first year of decay. Populations 

were higher in the first year, but species diversity was higher in the 

second and third years. Collembolans move between litter and woody 

debris, so it is difficult to separate litter forms from corticolous and 

lignicolous forms. Studies that include descriptive biology are necessary 

before we can assess the significance of woody debris for the community 

structure of collembolan populations. 

Introduction 

Between 92 and 99 percent of aboveground biomass in 

temperate and tropical forests is wood. This biomass may 

be in the form of aboveground wood and roots (Rodin and 

Basilevic 1967). A small part of the woody biomass is shed 

each year (Bray and Gorham 1964; Boddy and Swift 1983). 

Wood is, according to Swift and others (1979), a lowquality resource for organism metabolism. It has qualities 

that retard breakdown; i.e., extensive lignification and 

allelopathic compounds; it is protected by bark; and it is 

hard. Animals and microflora that exploit this resource are 

of necessity specific in their activity (Swift and Boddy 

1984). 

Kilbertus and Reisinger (1975) recognized a form of 

symbiosis between the microfauna and microflora. Swift 

and others (1976) reported that 60 to 75 percent of 

branchwood dry weight must be lost before wood-boring 

animals can invade. Fungi play an important role in this 

process. Two phases were proposed as models: Phase 1, 

fungal invasion (immobilization of nutrients), followed by 

Phase 11, animal invasion. Wallwork (1970) suggested that 

the microflora are affiliated with microfauna as: (I) gut 

symbionts, (2) a food source, and (3) competitive 

organisms seeking the same nutrients. 

Professor, Department of Zoology, Michigan State University, East 

Lansing, MI 48824. 

Recognition of the collembolan role in woody debris 

breakdown became clearer when Ausmus (1977) described 

four mechanisms that invertebrates may use for regulation 

of wood decomposition. These were: (I) translocation and 

defecation, (2) passive inoculation, (3) regulation of 

microbial succession and catabolic pathways, and (4) 

changes in microsite chemistry. In this scheme, he 

considered Collembola to be secondary invaders. Swift 

(1977) proposed the following model: 

Colonization-> Exploitation-> Invasion-> Post Invasion 

bacteria, beetles white & brown rots wood-borers soil fauna 

stain fungi, soft rots Collembola 

soft rots 

Here again, Collembola are viewed as secondary invaders, 

from the soil/litter subsystem. Lloyd (1963) drew attention 

to the movement of fauna between decaying branches and 

surrounding litter. When climatic conditions were 

unfavorable, the animals retreated to the litter. This critical 

interaction is the subject of a symposium publication by 

Anderson and others (1 984). 

Role of Collernbolans in Breakdown of 

Woody Debris 

The literature dealing with this subject is especially scant 

for forests in the Southern United States, where much of 

our information comes from studies that examined standing 

dead, stump, or log decay. Savely (1939), working in North 

Carolina's Duke Forest, studied the ecological succession 

of animals in pine and oak logs. He monitored logs from 

cutting to disintegration. He observed boring insects 

feeding in the phloem during the first year. They provided 

an entrance for fungi and eventually animals. He 

mentioned that the succession of wood-feeding animals 

may be controlled by fungi. During the first year of decay 

in both pine and oak, collembolans were found in the 

subcortical zone. Their species diversity was higher, while 

population nrtmbers were lower than in the second and third 

years. Species diversity decreased after the first year in 

both vegetation types. The common collernbolans found 

were four entomobryid, one isotomid, and one neanurid 

species. 
In contrast, Howden and Vogt (195 1) made no mention of 

collembolans in standing dead pine of approximately the 

same age as the logs used in Savely's (1939) study. Snow 

(1958), working in Alabama, examined the stratification of 

arthropods in a wet sweetgum (Liquidambar styraciflua L.) 

tree stump. He distinguished dry wall forms and moist wall 

forms among the arthropod inhabitants. In addition, four 

collembolan species were categorized as subcortical forms. 

His report showed that moist wall and subcortical forms 

were absent from dry wall situations. 

The only study dealing with Collembola and woody litter 

decomposition in a Southern United States forest was 

published by Abbott and Crossley (1982). The 

investigation was conducted at Coweeta Hydrologic 

Laboratory in North Carolina. One of their objectives in 

measuring the decomposition of chestnut oak (Quercus 

prinus L.) woody litter was to quantify microarthropod 

populations. They found that microarthropods, including 

oribatid mites and Collembola, were the dominant 

community on decaying wood. Abundance increased with 

time, and site condition was an important factor. While 

collembolans and mites were more abundant on smalldiameter twigs, the authors concluded that microarthropods 

were more effective on larger material. 

Southern United States Collembolan 

Diversity 

In general, the Aptergota fauna has received little attention 

from systematic zoologists in North America. Aside from 

Christiansen and Bellinger (1980-81) and Fjellberg (1985), 

very few authors have produced papers recently describing 

the collembolan fauna. The southern fauna in particular is 

poorly known. Until the 1980's, with few exceptions, 

checklists of southern species were so wanting that 

Zingmark (1978) wrote an annotated list for the Collembola 

of the coastal zone of South Carolina in which he recorded 

species that ought to be found there, based on North 

Carolina records. Knowledge of individual species 

distribution is sporadic. Regional, State, and local faunal 

studies are remarkably deficient. 

Some preliminary studies have resulted in checklists: 

Brimley (1938) for North Carolina, Copeland (1960) and 

Ford (1963) for Tennessee, Hepburn and Woodring (1963) 

for Louisiana, and Wray (1967) for North Carolina. Many 

of these lists contain distribution and site collection data 

useful to those interested in habitat and distribution 

information. They are helpful when attempting to assess 

species diversity, and provide clues for specific sampling 

designs. However, quantitative data and infomation on 

species associations are missing. 

Another source of collembolan biodiversity data in 

southern forests stems from decomposition studies. Forest 

floor litter and woody material (stumps, logs, and branches) 

are usually treated separately. Earlier in this paper it was 

shown, however, that the forest soilllitter collembolans 

were responsible for the secondary invasion of woody 

debris. Therefore, it is difficult to separate litter forms 

from corticolous and lignicolous forms. Pearse (1943) 

studied the effects of burning and raking off litter in the 

Duke Forest. He listed seven species of Collembola from 

the litter zone. Pearse (1946) did a more detailed study of 

the Duke Forest mesofauna and collected 44 collembolan 

species. He was able to show the effects of seasonal 

distribution, abundance, and food preferences. Knight and 

others (1963, 1966, 1967, 1969) in a series of papers 

demonstrated the effects of seasonality, pesticide effects, 

dietary requirements, and microstratification in beechmaple and loblolly pine forests in North Carolina. DuRant 

and Fox (1966) investigated the arthropod populations of 

pine and hardwood forests in the Piedmont region of South 

Carolina. They estimated that Collembola made up more 

than 80 percent of the insect fauna in either pine or 

hardwood forests. Their collections numbered 41 species, 

forming the basis of the current South Carolina species list. 

Metz and Dindal(1975) working in Santee Experimental 

Forest, South Carolina, reported the effects of prescribed 

burning on collembolan populations. They found that 

species diversity increased when periodic burning took 

place. Twenty-one species were reported out of 73 

collected in burned areas. It is unfortunate that the total list 

of Collembola was not published. Reynolds (1976) worked 

from November to April in the Coweeta Hydrologic 

Laboratory on litter decomposition as influenced by 

Collembola. He listed 17 species from a watershed 

dominated by deciduous trees. 

Oddly, a study conducted in Maryland (Howden and Vogt 

195 1) on standing dead trees did not reveal collembolans as 

species components. Closer to the soil, Snow (1958) 

examined the stratification of arthropods in a wet stump in 

Alabama. He listed eight collembolans and their location 

by moisture preference. Information about springtail 

diversity in logs was provided by Savely (1939). He 

compared pine and oak logs lying in contact with the soil. 

Working in the Duke Forest, he showed that the 

collembolan species diversity decreased as the logs 

decomposed. Subcortical collembolans were more 
Table 1~ollembolan species for the Southern United States 

State Author Publication Number 

North Carolina Brimley 

Savely 

Pearse 

Pearse 

Wray 

Wray 

Reynolds (unpublished) 

Graves and others 

Snider 

Christiansen & Bellinger 

Snider 

Tennessee 

Louisiana 

South Carolina 

Florida 

Virginia 

Alabama 

Copeland 

Ford 

Ford 

Snider 

Christiansen & Bellinger 

Hepburn & Woodring 

Hepburn 

Snider 

Christiansen & Bellinger 

DuRant & Fox 

Metz & Dindal 

Christiansen & Bellinger 

Snider 

Snider 

Snider 

Snider 

Snider 

Snider (unpublished) 

Snider 

Christiansen & Bellinger 

Snider 

Snider 

Snider 

Snider 

Christiansen & Bellinger 

Snow 

Christiansen & Bellinger 

Snider 

8 

26 

1 

(continued) 
Table 1-Collembolan species for the Southern United States (continued) 

State Author Publication Number 

Mississippi 

Georgia 

Arkansas 

Texas 

Snider 

Christiansen & Bellinger 

Christiansen & Bellinger 

Snider 

Snider 

Snider 

Snider 

Christiansen & Bellinger 

Tedder (unpublished) 

Snider 

Christiansen & Bellinger 

a Approximately 20 names have been invalidated. 

73 species were collected, only 2 1 species names were published. 

50 of these species are new to science. 

numerous in pine than in oak. He listed eight common 

species. Finally, an important paper by Graves and others 

(1977) lists 75 species from shelf fungi, moss, rhododendron litter, sawdust, and tree-hole debris. Only 12 

species were common in fungi, moss, and litter. Shelf 

fungi yielded 48 species; sawdust, only 1: Brachystometta 

stachi Mills. 

Systematic biologists interested in species diversity and 

distribution at the alpha taxonomic level have contributed 

their part to our knowledge of southern collembolan 

species. Wray (1945, 1946, 1949, 1950, 1953, 1959, 

1963a, 1963b, 1971) contributed greatly by describing 

many new species from the Carolinas and Tennessee. Ford 

(1962) described three new species from Tennessee. 

Nepbum (1964) described a new species from Louisiana. 

Tedder (1991) did a faunistic survey of collembolans found 

on Magazine Mountain, Logan County, Arkansas. She 

collected samples from deciduous duff, humus, and 

sphagnum moss over a 3-year period. Her inventory 

resulted in 74 species. Her data suggested that the Eastern 

North American fauna most influenced that observed in 

central Arkansas. Christiansen and Bellinger (1980-8 1) 

provided the current foundation for a new assessment of 

southern species diversity. Their new species descriptions, 

range extensions, and corrections of identifications have 

expanded the numbers greatly. Since their publication, 

Snider (198 la, 198 1 b, 198 lc, 1982a, 1982b, 1985a, 1985b, 

1985c, 19854, 1988, 1989,1990) and Snider and Loring 

(1982) were able to add many new species to the faunal 

lists. Snider' has conducted studies on the collernbolms at 

the Savannah River Site in South Carolina since 1980. The 

number of species presently stands at 160,50 of which are 

new. Original plans were to record only the Savannah 

River Site; however, samples have been taken to include 

South Carolina, Georgia, Horida, Alabama, and Tennessee. 

Table 1 shows the known sources of collembolan species 

lists for the southern United States. 

' Richard J. Snider, unpublished data. 
Conclusion Ford, Floyd M. 1962. Notes on Tennessee Collembola. Three new 

species of Isotomidae: Folsornia. Journal of the Tennessee Academy of 

Science. 37: 129- 132. 

The obvious conclusion here is that we know only bits and 

pieces about our Southern United States collembolan fauna, 

and even less about their specific role in woody debris 

breakdown. Intensive studies yield large numbers of 

species, many of which may be undescribed. We cannot 

begin to assess diversity and cornmunity structure of 

collembolan populations without studies that include 

descriptive biology. The specific functional role of 

Collembola in woody breakdown has not been well 

documented. However, preliminary studies demonstrate 

the existence of important relationships between 

collernbola and microflora in the late stages of decay. 

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Importance of Coarse Woody Debris to 

Southern Forest Herpetofauna 

Matt R. Whiles and Jack W. Grubaugh 

Abstract 

Most information on the relationships between herpetofaunal diversity 

and coarse woody debris (CWD) exists in the form of natural history 

observations; experimental data are lacking. However, these observations 

demonstrate that all major groups of North American reptiles and 

amphibians use CWD in some manner. The range of temperature and 

moisture regimens associated with CWD, along with its structural 

diversity, are important to many amphibians and reptiles for a variety of 

reasons. CWD serves as an important site for such vital activities as 

reproduction (nesting and mate attraction), feeding, and 

thermoregulation. Additionally, some groups such as salamanders may 

be obligatory in their association with CWD. Other probable uses of 

CWD by herpetofauna, such as refugia from predation, are potentially 

important but not well documented. Existing evidence suggests that 

amphibian and reptile diversity is likely linked to both quantity and 

quality of CWD. Thus, the current trend in forest management which 

enhances CWB availability should be continued. 

Introduction 

The forests of the Southern United States are inhabited by a 

rich diversity of frogs, toads, salamanders, lizards, snakes, 

and turtles. This region has the highest herpetofaunal 

diversity in the United States, including a large fraction of 

all known salamander species in the world (Conant and 

Collins 199 1 ; Goin and Goin 197 1). Several interrelated 

factors account for this diversity, including the geologic 

and physiographic variability of the region (Mount 1975). 

Unfortunately, in many regions of the Southeast and the 

rest of the United States, this diversity is impeniled by land 

management practices and habitat destruction (Dodd 1987; 

Duellrnan and Trueb 1986; Wilson and Porras 1983). 

The majority of reptiles and amphibians in the United 

States have little or no recognized economic importance; 

thus, management of herpetological communities has 

historically received little attention. However, with 

increased interest in the conservation of biodiversity, all 

plant and animal communities (including reptiles and 

amphibians) are now considered important components of 

forest ecosystems. Many amphibians and reptiles are 

important predators on invertebrates and other vertebrates. 

In turn, herpetofauna are important dietary components of 

other vertebrates. Additionally, many amphibians and 

reptiles have an aesthetic value too rarely recognized. 

As concern over the conservation of biodiversity increases, 

scientists and land managers are striving to identify habitat 

characteristics that promote diversity and abundance of 

organisms (e.g., Hansen and others 199 1; Hansen and 

others 1993; Sharitz and others 2 992). Ideally, 

identification of important habitat characteristics is 

followed by instigation of appropriate management plans. 

Of the many significant habitat features currently 

identified, the abundance, distribution, and condition of 

coarse woody debris (CWD) appears to be extremely 

important for optimizing diversity in both terrestrial 

(Harmon and others 1986; Maser and others 1988; 

Swanson and Franklin 1992) and aquatic (Benke and others 

1984; Harmon and others 1986; Maser and others 1988) 

ecosystems. 

The objective of this paper is to examine the relationship 

between CWD and herpetofaunal diversity. Little 

experimental data on this relationship exist. Most of the 

information has been gathered from natural history studies 

of various herpetofauna, which provide important 

information on the function of CWD in herpetofaunal 

communities. The few studies that directly examined the 

relationship between herpetofaunal diversity and 

CWD (mostly on salamanders in the Northwestern United 

States) are discussed where relevant. Recommendations 

and possible management strategies are discussed as well. 

Uses of Coarse Woody Debris by 

Amphibians and Reptiles 

Herpetofauna use woody debris for a wide variety of 

purposes (tables 1 and 2); and the usefulness of CWD is 

Graduate Students, Institute of Ekology, University of Georgia, Athens, 

CA 30602-2602. 
Table 1-Some uses of coarse woody debris by North American amphibians 

- 

Use 

Salamanders Frogs Toads References 

Reproduction (nesting) X 

Reproduction (calling) 

Feeding substrate 

Thermoregulation X X X 

(hibernationlprotection 

from temperature 

extremes, warming) 

Protection from 

desiccation 

Norman 1986; Maser & Trappe 1984; 

Thomas 1979; Mount 1975; Smith 1961 

Thomas 1979; Johnson 1977 

Harmon and others 1986; Maser 

& Trappe 1984; Mount 1975; 

Storm & Aller 1947 

Aubry and others 1988; Maser & 

Trappe 1984, Thomas 1979, Mount 1975; 

McKenzie & Storm 1970 

Aubry and others 1988; Maser & Trappe 

1984; Thomas 1979; Mount 1975; 

Stebbins 1966 

Table 2-Some uses of coarse woody debris by North American reptiles 

Use Lizards Snakes Turtles References 

Reproduction 

(nesting) 

Feeding substrate 

Themoregulation 

(hibernationlprotection 

from temperature extremes, 

basking) 

Protection from 

desiccation 

Ernst & Barbour 1989; Thomas 1979; 

Mount 1975; Fitch 1954, 1963; Stille 1954 

X X Collins 1982; Thomas 1979; Mount 1975 

X X X Ernst & Barbour 1989; Collins 1982; 

Gregory 1982; Mount 1975; Brattstrom 1965; 

Fitch 1954 

Ernst & Barbour 1989; Collins 1982; 

Mount 1975; Smith 1961 
probably attributable to the associated range of 

environmental conditions (e.g., temperature and moisture 

regimes) (Hamon and others 1986; Maser and others 1988; 

Maser and Trappe 1984; Thomas 1979). In forest 

ecosystems, CWD increases habitat heterogeneity and thus 

structural diversity (Hansen and others 1991; Sharitz and 

others 1992). Both are vital components in determining the 

diversity of herpetofauna and other organisms in forested 

systems (Harmon and others 1986). 

Unfortunately, the relative importance of CWD for any one 

purpose is hard to determine due to the interrelationships of 

these uses (e.g., both themoregulating and avoiding 

predation in a sun-warmed log). However, all major groups 

of amphibians and reptiles have been reported to use CWD 

in at least some fashion (table 3). Of these, turtles and 

toads appear to be the least associated with CWD, while 

frogs, lizards, snakes, and salamanders use CWD 

extensively for a variety of purposes. It should be noted 

that many uses are assumed or observed but have not been 

well documented or tested experimentally (table 3). 

The Role of Coarse Woody Debris in Amphibian and 

Reptile Reproduction 

Reptile eggs often require warm temperatures for proper 

development (Goin and Goin 197 1 ). Additionally, females 

with eggs developing within them, and those that are 

ovoviviparous, often become thermophilic prior to egglaying or delivery (Goin and Goin 197 1 ; Heatwole 1976). 

Incubation temperatures influence development time, 

hatching success, and health of hatchling reptiles (Deeming 

and Ferguson 199 1; Janzen 1993; Packard and others 

1987). Amphibian eggs are less dependent upon warm 

temperatures but can be quite sensitive to extremes 

(Duellman and Trueb 1986, Goin and Goin 197 1). 

Numerous amphibians and reptiles deposit eggs in and 

under downed logs (Collins 1982; Ernst and Barbour 1989; 

Fitch 1954, 1963; Maser and Trappe 1984; Norman 1986; 

Stille 1954; Thomas 1979). For many species of 

amphibians and reptiles, downed logs provide an optimal 

temperature environment for egg incubation by damping 

temperature fluctuations (Savely 1939). In addition, sites 

within and around a given log can provide a range of 

temperature regimes (Graham 1925; Savely 1939). 

Graham (1925) observed temperatures higher than ambient 

on the upper sides of logs exposed to sunlight, while 

temperatures under these logs were lower than ambient. 

These features of CWD allow placement of eggs in areas 

with optimal temperature regimes and reduce the risk of 

detrimental temperature fluctuations during development. 

Table 3-Uses of coarse woody debris by North American 

frogs (F), lizards (L), salamanders (SA), snakes (SN), toads 

(T), and turtles (TU) 

Use 

Group 

F L SA SN T TU 

Reproduction: 

Nesting OXXXO? 

Mate attraction: 

Calling XOOOOO 

Displaying O?OOOO 

Feeding substrate XXXX?? 

Thermoregulation: 

Hibernation/ XXXXX? 

avoidance of cold 

Avoidance of heat XXXXX? 

Basking or warming X X X X ? X 

Avoidance of desiccation X ? X ? X ? 

Predator avoidance: 

Refugia ?????? 

Lookout post O?O?O? 

Total (X) 655531 

Total (X + ?) 798868 

X = documented in literature, ? = likely to occur, but no 

documentation found (use may be mentioned or speculated 

by some authors, but not well documented), 0 = probably 

does not occur. 
Eggs of both reptiles and amphibians are subject to 

desiccation during dry periods (Coin and Coin 197 1). 

Moisture availability during incubation is critical to 

hatching success, as well as condition of hatchlings 

(Duellman and Trueb 1986; Fitch and Fitch 1967; Packard 

and Packard 1988). Downed logs and the surfaces beneath 

downed logs provide optimal moisture for many reptile and 

amphibian eggs (Maser and Trappe 1984; Thomas 1979). 

The interiors of these logs have relatively constant moisture 

regimes compared to most forest surface habitats, and 

usually remain moist longer during dry periods (Boddy 

1983, Place 1955). 

Belowground conditions may also provide a constant 

temperature and moisture environment; however, for some 

taxa belowground conditions may be too cool and/or too 

dry or wet for proper incubation. Additionally, in areas 

with clay and other relatively hard soils, nest excavation 

into decomposing logs (or the use of pre-existing tunnels of 

other wood-inhabiting animals) requires less energy 

expenditure than ground excavation. 

Salamanders appear to be most closely associated with 

CWD for reproduction. All known nest sites of Ensatina in 

the Pacific Northwest were found in association with CWD 

(Jones and Aubry 1985; Maser and Trappe 1984; Norman 

and Norman 1980). In forests of the Eastern United States, 

the marbled salamander, Ambystoma opaceum 

(Gravenhorst), is apparently dependent upon downed logs 

for successful reproduction. During the autumn-winter 

breeding season, adult A. opaceurn emerge from 

underground retreats and migrate to river flood plains. 

Here courtship and fertilization take place. Eggs are 

deposited on land in a shallow depression and guarded by 

the female until spring flooding of the nest. Nests are 

located under downed logs or any other available cover 

(Mount 1975; Smith 19619, most likely to avoid desiccation 

andlor predation on the adult female and her brood. Other 

uses of CWD associated with herpetofaunal reproduction 

include calling sites for male tree frogs attracting mates to 

breeding ponds (Thomas 19799, and perches for male 

lizards protecting harems or signaling potential mates 

(Werth 1972). 

Coarse Woody Debris as Habitat and Refugia 

for Forest Herpetofauna 

All extant amphibians and reptiles are predominantly 

ectothemic. Thus, most themoregulation is accomplished 

by moving to favorable microhabitats (Brattstrom 1965; 

Cloudsley-Thompson 197 1 ; Duellman and Trueb 1986; 

HeatwoIe 1976). Additionally amphibians and, to a lesser 

degree, reptiles are subject to desiccation. Relatively 

constant temperature and moisture regimes found in and 

under CWD provide protection from temperature extremes 

and moisture loss (Aubry and others 1988; Harmon and 

others 1986; Maser and Trappe 1984; Thomas 1979). 

Throughout most of North America, herpetofauna hibernate 

during the winter months. Depending upon the severity of 

winter in a given region, large logs and other forms of 

CWD can serve as important shelter for hibernation during 

cold periods (Gregory 1982; Harmon and others 1986; 

Stebbins 1966; Thomas 1979). In or under CWD, risk of 

freezing is reduced, moisture remains available, and the 

hibernating animal is sheltered from predators. 

Cooling is usually accomplished by burrowing or using 

pre-existing burrows, movement to shade or cover, or 

movement into CWD (Cloudsley-Thompson 197 1; Goin 

and Goin 197 1 ; Maser and Trappe 1984). Thus, cooling 

activities generally do not increase risk of predation. In 

contrast, warming requires movement to surface areas 

exposed to sunlight. Except for species capable of rapid 

escape from predators, warming sites that allow the animal 

to remain hidden are almost always chosen (undersides of 

sun-warmed rocks, logs, and other surface debris, or 

beneath the bark of dead trees) (Brattstrom 1965; 

Cloudsley-Thompson 197 1 ; Collins 1982; Ernst and 

Barbour 1989; Maser and Trappe 1984; Smith 196 1 ; 

Thomas 1979). 

In aquatic and semiaquatic habitats, CWD is often used as 

basking sites by semiaquatic herpetofauna (Brattstrom 

1965; Collins 1982; Smith 196 1). Congregations of 

Psuedemys, Graptemys, Chrysemys, and other semiaquatic 

turtles can often be observed basking on exposed portions 

of partially submerged CWD in the Southeastern United 

States. Watersnakes of the genus Nerodia also use these 

basking sites. Basking sites are important in that they 

allow the animal to raise its body temperature for feeding 

and digestion and still avoid predators confined to 

shorelines. 

Many small snake species of southeastern forests, such as 

the scarlet snake, Cemophora coccinea (Blumenbach) 

(Palmer and Tregembo 1970), and the pine woods snake 

Rhadinia Jlavilata (Cope) (Myers 1967), are often found in 

close association with CWD. Many salamanders (e.g., 

Batrachoseps and Ensatina in the West, and many species 

of Plethodon throughout the United States) spend most of 

their lifespan in or near CWD (Aubry and others 1988; 
Maser and Trappe 1984; Mount 1975; Raphael 1983). 

on and others (1986) suggested possible obligatory 

use of GWD by salamanders, This close association with 

CWD, apparent in both amphibians and reptiles, is 

undoubtedly linked to predator avoidance as well as 

temperature and moisture regulation. 

Predators of amphibians and reptiles include birds, 

mmmals, other reptiles and amphibians, and, to a lesser 

degree, fish and invertebrates. Although no experimental 

evidence for the role of CWD as a refuge from predation 

appears to exist, behavioral observations and natural history 

information suggest that CWD is quite important in 

this regard. 

Coarse Woody Debris as Feeding Substrate 

for Herpetofauna 

Downed logs and other forms of CWD often harbor high 

densities of invefiebrates, some of which (e.g., termites) are 

obligatory in their use of CWD (Harmon and others 1986; 

Maser and Trappe 1984; Seastedt and others 1989). These 

CWD-inhabiting invertebrates represent an important food 

resource for forest herpetofauna--one that is accessible 

without requiring them to forage in the open, where risk of 

predation is increased. 

Although little experimental evidence exists regarding the 

importance of CWD as a source of prey, numerous 

observations of herpetofauna feeding in and around CWD 

are documented (e.g., Collins 1982; Emst and Barbour 

1989; Maser and Trappe 1984; Mount 1975; Smith 196 1). 

The majority of forest herpetofauna feed on invertebrates, 

and CWD-inhabiting invertebrates are undoubtedly an 

important resource. Storm and Aller (1947) found termites 

in the guts of Aneidesferreus (Cope); conclusive evidence 

that these salamanders were foraging within CWD. 

Lizards, such as Sceloporus undulutus (Latrielle) and 

Anolis carolinensis carolinensis (Voigt), often bask on 

sunlit snags and logs in southern forests. The lizards are 

most likely feeding in this habitat, as basking is linked to 

enicient foraging and digestion (Cloudsley-Thompson 

197 1 ; Coin and Coin 197 1 ). 

High diversity and densities of invertebrates in CWD, 

along with the favorable temperature and moisture 

conditions, attract food items for larger reptiles as well. 

Small mammals, amphibians, and reptiles associated with 

GWD in southern forests represent important prey items for 

larger snake species (e.g., Elaphe and Pituophis) (Ernst and 

Barbour 1989). Rat snakes, such as the black rat snake 

(Eluphe obsoleta obsoleta) (Say) of eastern and 

southeastern forests, often forage in and around logs and 

snags for small mammals and birds (including cavity 

nesting birds) (Ernst and Barbour 1989; Fitch 1963; Mount 

1975; Neal and others 1993). 

In aquatic systems, biomass and production of invertebrates 

and fish are often highest on and around snags (Benke and 

others 1984). These "hot spots" of biotic activity represent 

important foraging areas for water snakes (mostly Nerodia) 

and some aquatic (e.g., Chelydru) and semiaquatic (e.g., 

Chrysemys and Graptemys) turtles in streams and lakes of 

the South. Also, these foraging areas are conveniently 

associated with basking surfaces. 

Other Uses of Coarse Woody Debris 

by Herpetofauna 

Some lizards (e.g., Sceloporus and Anolis) that inhabit 

eastern forests maintain territories and communicate to 

conspecifics and others through body movements (Collins 

1982; Mount 1975). This behavior is often performed from 

an elevated perch where the animal is basking. Snags and 

other forms of CWD are potentially important in this 

respect, as they are often well lit (no leaves) and elevated. 

These perches may also provide good vantage points for 

detection of predators (Mount 1975). 

Management 

In recent years, demand has been increasing for watershed 

preservation and nonprofit amenities, such as conservation 

of biodiversity in forests (Sharitz and others 1992). 

Integrating these demands with profitable production 

practices is a challenge for land managers. Attention is 

tuming not only to forest-stand age, but also to habitat 

heterogeneity (landscape and habitat) and structural 

characteristics (including quantity and quality of CWD) of 

the forest stand (Spies and others 1988). 

The importance of CWD to diversity of many flora and 

fauna is well documented (e.g., H on and others 1986), 

and current forestry practices are changing to enhance the 

quantity of GWD in managed forests (Swanson and 

Franklin 1992). As research into these relationships 

proceeds, hmesting and silvicultural practices must 

continue to more toward methods that enhance CWD 

availability and other forms of stmctural diversity in 

southern forests. 
Conclusions and Research Needs 

Obvious relationships exit between the herpetofaunal 

communities of the Southeastern United States and GWD. 

The relative importance of each use is difficult to ascertain 

because many uses are probably interrelated. However, all 

major herpetofaunal groups have been shown to use GWD 

in some fashion, and many are using it for such vital 

processes as reproduction and feeding. This evidence 

warrants the continued change in management practices 

toward methods that encourge the availability of CWD and 

other components of structural diversity. 

Herpetofaunal cornunities have received little qualitative 

and even less quantitative study. However, some recent 

studies suggest that species using CWD may predominate 

within the herpetofauna (Harmon and others 1986; Raphael 

1983; Raphael and others 1982). These studies (mostly 

from western forests), and the available information on life 

histories suggest that species diversity may be more closely 

linked to CWD in herpetofauna than in any other vertebrate 

group. Studies directly exmining this relationship, 

especially in southern forests, are clearly needed. 

Experiments exarnining the responses of herpetofaunal 

communities to CWD removal or addition, and the 

qualitative characteristics of the CWD used, would provide 

more conclusive information on the importance of CWD to 

herpetofaunal diversity. 

Acknowledgments 

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Influences of Coarse Woody Debris 

on Birds in Southern Forests 

J. Drew Lanharn and David C. Guynn, Jr. 

Abstract 

The importance of coarse woody debris (CWD) as a habitat component 

for birds in southern forests is reviewed. Few studies estimating snag 

density and relating species use to snag characteristics have been 

conducted in southern forests. We are unaware of studies describing the 

use of dead down woody debris (DDW) by any bird species except ruffed 

grouse, which use is for drumming logs. However, 45 species using 

snags and 20 species using DDW were identified primarily from natural 

history accounts. Snag density appeared to be directly related to the 

hardwood component and intensity of timber management across forest 

types. Use of snags by cavity-using birds was related to size, degree of 

decay, and tree species of snags. Snags appear to stand for a short time; 

managers begun to address issues of snag management in 

the Southern United States (Carmichael and Guynn 19133). 

Information on the value of DDW to birds is severely 

lacking. Most of the research that has acknowledged use of 

DDW by birds has been conducted in the Pacific Northwest 

(Maser and others 1979) where forest types, climate, log 

decay dynamics, and management practices differ markedly 

from those in the South. Most accounts of bird use of 

DDW in southern forests are anecdotal in nature with the 

exception of ruffed grouse drumming log studies. 

Sabin (1991) reported that 88 percent of snags in the South Carolina The main purpose of this paper is to highlight the few Piedmont fell within 6 years after death. Identified research needs include 

the following tasks: (I) describe CWD dynamics by forest type, (2) studies conducted in the Southern United States that relate 

relate! use by species and guild to CWD characteristics, (3) relate bird snag characteristics and management practices to bird 

species richness and diversity to size distribution of CWD, and (4) relate abundance and species diversity. We will also describe the 

bird species occurrence and diversity to CWD characteristics through potential importance of DDW to various species of birds in 

controlled experiments. southern forests from natural history accounts. 

Introduction 

Coarse woody debris (CWD), in the form of standing dead 

trees (snags) and down dead woody materials (DDW), is a 

critical and dynamic component of forest habitats for birds 

(Hunter 1990; Maser and Trappe 1984). Snags are created 

by fire, insects, disease, wind, lightning, and suppression 

(Fischer and McClelland 1983; Harlow and Guynn 1983) 

and may represent 5 to 10 percent of the standing trees in a 

forest (Hunter 1990). Down dead woody is created when 

trees are felled and recruited to the forest floor by forces 

such as wind, ice and/or snow, soil movement, floods, 

natural decay, and senescence of snags (Maser and Trappe 

1984). Cull trees, as well as stumps, limbs, and slash, may 

also become DDW as a result of fires and stand 

improvement operations. 

The value of snags as wildlife habitat, and in particular to 

various bird species, has been well documented. Fischer 

and McClelland (1983) published a bibliography 

addressing snags and cavity-nesting species that includes 

1,7 13 titles. However, only recently have researchers and 

Graduate Research Assistant and Professor, respectively, Department of 

Forest Resources, Clemson University. Clemson, SC 29634-1003. 

Usage of Snags 

Birds use snags for drumming, perching (hunting and 

singing), foraging, nesting, and roosting (Bull 1978; Miller 

and Miller 1980; Scott and others 1977). In North 

America, 85 species of birds are classified as either primary 

cavity-nesters, excavating their own nest holes, or as 

secondary cavity-nesters, using cavities created by disease, 

mechanical injury, or by primary excavators (Fischer and 

McClelland 1983). Within the Southern United States, 

Hamel (1992) lists 45 species of birds that use snags and/or 

cavities for various purposes (table 1). 

Snag characteristics, such as density and longevity, vary 

according to stand type, stand age, and stand history (table 

2). Although relatively few studies have been conducted in 

southern forests, certain trends are apparent from studies in 

South Carolina (Carmichael 1983; Carmichael and Guynn 

1983; Harlow and Guynn 1983; Sabin 1991), Florida (Land 

and others 1989; McComb and others 1986), Kentucky 

(McComb and Muller 1983; Moriarty and McComb 1983), 

Louisiana, and Mississippi (McComb 1979). 

On the South Carolina Coastal Plain, Harlow and Guynn 

(1983) found that nonpine stands had significantly higher 

densities of pine and hardwood snags than pine-dominated 

stands. They also found that the majority of snags (84 

percent) were pine and less than 14 inches in diamater at 
Table 1-Bird species that use snags and cavities in the Southern United States 

Species 

groupinga 

Cavity Minimum 

Snag tree snag Species 

useb useb d.b.h. groupinga 

Cavity Minimum 

Snag tree snag 

useb useb d.b.h. 

Game species: 

Wood duck+ N 

Hooded merganser" N 

Diurnallnocturnal raptors: 

Black vulture* N 

Turkey vulture' N 

Osprey NIP 

Bald eagle NIP 

American kestrel' F/N 

Common barn-owl+ NIP 

Eastern screech owl+ NIP 

Barred owl+ NIP 

Northern saw-whet owl+ NIP 

Resident species: 

Belted kingfisher 

Red-headed woodpecker*+ 

Red-bellied woodpecker 

Northern flicker*' 

Yellow-bellied sapsucker* 

Downy woodpecker* 

Hairy woodpecker* 

Red-coc kaded woodpecker* 

Pileated woodpecker* 

Black-capped chickadee*" 

Carolina chickadee*' 

F 

NIP 

NIP 

NIP 

N 

A 

A 

A 

NIP 

NIP 

- 

NIP 

NIP 

N/P 

NIP 

NIP 

- 

NIP 

NIP 

NIP 

F 

A 

A 

A 

NIP 

N/P 

NIP 

Tufted titmouse*" NIP NIP 

Red-breasted nuthatch*' N - 

White-breasted nuthatch*" - N 

Brown-headed nuthatch*" N N 

Brown creeper' N N 

Carolina wren+ N N 

Bewick's wren+ N N 

Resident species: 

Eastern bluebird+ NIP NIP 

hggerhead shrike F - 

European starling' N N 

Brown-headed cowbird P - 

Neotropical migrants: 

Chimney swift+ 

Olive-sided flycatcher 

Eastern wood-pewee 

Acadian flycatcher 

Great crested flycatcher' 

Western kingbird 

Eastern kingbird 

Gray kingbird 

Purple martin+ 

Tree swallow+ 

House wren+ 

Prothonotary warbler" 

NIP NIP 

F - 

F - 

F - 

NIP N/P 

F - 

F - 

F - 

N N 

N - 

" * = primary cavity nester; + = secondary cavity nester (for scientific names, see table 4). 

N = breedinglnesting; P = perching; F = foraging; A = all activities. 

Source: Adapted from Hamel 1992. 
Table 2-Snag densities in Southern United States forest types 

Snag 

Location Forest type Age density Source 

South Carolina 

South Carolina 

South Carolina 

South Carolina 

South Carolina 

South Carolina 

South Carolina 

South Carolina 

South Carolina 

South Carolina 

Upland hardwood 

Cove hardwood 

Upland hardwood 

Pine-hardwood 

Cove hardwood 

Pine-hardwood 

Pine plantation 

Pine plantation 

Oak-tupelo-cypress 

Longleaf pine 

Florida 

Florida 

Florida 

Florida 

Florida 

Florida 

Pine 

Hardwood 

Pine 

Pine-hardwood 

Pine 

Pine 

61+ 

All 

3 1-60 

All 

All 

0-30 

Kentucky 

Kentucky 

Kentucky 

Kentucky 

Louisiana 

Louisiana 

Bottomland hdwd. 

Bottomland hdwd. 

Mississippi 

" 1 = Carinichael and Guynn (1983); 2 = Sabin (1991); 3 = Harlow and Guynn (1983); 4 = McComb and 

Muller (1983); 5 = Moriarty and McComb (1983); 6 = McComb and others (1986); 7 = McComb (1979). 

breast height (d.b.h.). Using average bird density estimates 

derived from Legrand and Hamel (1980), Harlow and 

Guynn (1983) concluded that-for birds using smaller 

snags (5 through 9 inches d.b.h.)-nonpine stands had 

> 100 percent of the minimum number of suitably sized 

snags for average bird populations. Pine stands, however, 

contained only 20 percent of the minimum number of this 

size class needed for average bird populations, Estimates 

of the abundance of larger snags (> 10 inches d.b.h.) were 

lower. Nonpine stands provided enough snags for 27 

percent of the needs of average bird populations, while 

larger diameter-class pine stands provided enough snags for 

only 6 percent of average bird populations. 

McComb and others (1986) assessed the densities of snags 

in Florida and also found them to be more abundant in 

hardwood stands than in pine stands. Snag densities were 

higher in older (> 61 years) stands, naturally regenerated 

pine stands (vs. plantations), riparian zones, and deep 

swamps (as compared to drier uplands). They detected a 

positive correlation (r = 0.7 1) between estimated densities 

of primary cavity-nesters and densities of snags among age 

classes and cover types. They recommended that a surplus 

of 4 to 9 snags per primary cavity-nester be maintained for 

average potential populations of primary cavity-nesters in 

Florida, 
Table 3-Bird species use of coarse woody debris in Southern United Statesa 

Speciesb Statusc Use Sourced 

Green-backed heron 

Black vulture 

Turkey vulture 

Ruffed grouse 

Wild turkey 

Northern bobwhite 

American woodcock 

Common nighthawk 

Chuck-will's-widow 

Pileated woodpecker 

Flycatcher species 

Carolina wren 

Bewick's wren 

House wren 

Winter wren 

Wood thrush 

Blue-winged warbler 

Louisiana waterthrush 

Prothonotary warbler 

Kentucky warbler 

Slash percher 

Log nester 

Log nester 

Log drummer, rooster 

Nests under fallen canopies 

Log rooster 

Nests beside logs 

Stump nester 

Hollow log rooster 

Log forager 

Root wad perchers 

All activities 

All activities 

All activities 

All activities 

Territory defense from logs 

Nests beside log 

Root wad nester 

Floating log forager 

Nests under fallen canopies 

a Southern States include: AL, AR, FL, GA, KY; LA, MS, NC, eastern OK, SC, TN, eastern 

TX, VA. 

For scientific names see table 4. 

" B = breeder in the Southern United States (Hamel 1992); W = winter resident in the 

Southern United States (Hamel 1992). 

1 = Hamel (1992); 2 = Terres (1980); 3 = Maser and others (1979). 

Land and others (1989) studied slash pine plantations in the 

Florida Coastal Plain and found that higher snag densities 

were associated with stands containing many snag clusters 

(3 2 snags < 0.5 m apart). Overall density estimates for this 

study (2.6 to 38.6 ha) fell within the range of most other 

southern studies cited previously, They also found that 

cavity-nesting bird density, diversity, and species richness 

were positively influenced by increases in stand age, stand 

d.b.h., and resultant increases in snag density. Cavity-nester 

densities also increased as the area of land surrounding the 

study sites increased. Species diversity declined, however, 

as the area of a single-aged stand increased. 

Cmichae1(1983), Carmichael and Guynn (1983), and 

Sabin (1991) conducted snag density studies in the upper 

Piedmont of South Carolina. Carmichael(1983) and 

Carmichael and Guynn (1983) found that significant 

differences existed among different stand types in the 

Piedmont and also between the Piedmont and Coastal 

Plain, In the Piedmont, upland and cove hardwood sites 

had higher densities of snags than pine-hardwood sites and 

pine plantations. Smaller snags (10.1 to 25.0 cm) also 

outnumbered larger diameter classes in the Piedmont. 

When compared to Harlow and Guynn's findings, 

Piedmont sites were found to have higher densities of 

snags. Carmichael(1983) found that the abundance and 

diversity (H') of birds detected on transects with snags 

were greater than on transects without snags during the 

nonbreeding season. Bird species diversity was not 

significantly different during the breeding season, however. 

Sabin (1991), in a continuation of Garmichael's study, 

noted similar trends, with hardwood sites having the 

highest snag densities and pine plantations having the 
Table &Scientific names of birds using coarse woody debris in southern forests 

Common name Scientific name Common name Scientific name 

Green-backed heron 

American woodcock 

Wood duck 

Hooded merganser 

Black vulture 

Turkey vulture 

Osprey 

Bald eagle 

American kestrel 

Ruffed grouse 

Northern bobwhite 

Wild turkey 

Common barn-owl 

Eastern screech-owl 

Barred owl 

Northern saw-whet owl 

Chuck-will's-widow 

Common nighthawk 

Chimney swift 

Belted kingfisher 

Red-headed woodpecker 

Red-bellied woodpecker 

Yellow-bellied sapsucker 

Downy woodpecker 

Hairy woodpecker 

Red-cockaded woodpecker 

Northern flicker 

Pileated woodpecker 

Olive-sided flycatcher 

Butorides striatus 

Philohela minor 

Aix sponsa 

bphodytes cucullatus 

Coragyps atratus 

Cathartes aura 

Pandion haliaetus 

Haliaeetus leucocephalus 

Falco spawerius 

Bonasa umbellus 

Colinus virginianus 

Meleagris gallopavo 

Tyto alba 

Otus asio 

Strix varia 

Aegolius acadicus 

Caprimulgus carolinensis 

Chordeiles minor 

Chaetura pelagica 

Megaceryle alcyon 

Melanerpes erythrocephalus 

Melanerpes carolinus 

Sphyrapicus varius 

Picoides pubescens 

Picoides villosus 

Picoides borealis 

Colaptes borealis 

Dryocopus pileatus 

Nuttallomis borealis 

Eastern wood-pewee 

Acadian flycatcher 

Great crested flycatcher 

Western kingbird 

Eastern kingbird 

Gray kingbird 

Purple martin 

Tree swallow 

Black-capped chickadee 

Carolina chickadee 

Tufted titmouse 

Red-breasted nu thatch 

White-breasted nuthatch 

Brown-headed nuthatch 

Brown creeper 

Carolina wren 

Bewick's wren 

House wren 

Winter wren 

Eastern bluebird 

W~od thrush 

Loggerhead shrike 

European starling 

Prothonotary warbler 

Blue-winged warbler 

Louisiana waterthrush 

Kentucky warbler 

Brown-headed cowbird 

Contupus virens 

Empidona virescens 

Myiarchus crinitus 

Tyrannus verticalis 

Tyrannus tyrannus 

Tyrannus dominicensis 

Progne subis 

lridoprocne bicolor 

Parus atricapillus 

Parus carolinensis 

Parus bicolor 

Sitta canadensis 

Sitta carolinensis 

Sitta pusilla 

Certhia familiaris 

Thryothorus ludoicianus 

Thryomanes bewickii 

Troglodytes aedon 

Troglodytes troglodytes 

Sialia sialis 

Hylocichla mustelina 

Lanius ludovicianus 

Stumus vulgaris 

Protonotaria citrea 

Vermivora pinus 

Seiurus motacilla 

Oporomis formosus 

Molothrus ater 

lowest. Specifically, he concluded that shortleaf and 

loblolly pines, and red and white oaks accounted for 95 

percent of all cavity years. Shortleaf pine made up 16 

percent of all snags but accounted for 58 percent of all 

cavity years observed. Snag loss was calculated at 0.52 

snags per ha per year, with 88 percent of all snags falling 

within a 6-year period, The mean number of cavities per 

snag ranged from 0.04 to 0.17 cavities per snag during the 

first 5 years after death and increased to 0.62 cavities per 

snag 6 years after death. Kentucky studies on stands 

improved for timber production vs. unmanaged stands 

revealed a higher density of snags in the improved stands 

(Moriarty and McComb 1983). Improved timber stands 

had a higher density of animal-excavated cavities, but the 

unmanaged stands had higher densities of cavities from 

other sources. 

Usage of Down Dead Woody Debris 

Hamel (1992) cites nine species of birds that use downed 

logs, slash piles, and windrows. Accounts from natural 

history studies also indicate that various species of birds 

not typically associated with DDW, use downed logs, roots 

of windthrows, or fallen branches in some manner. Maser 

and others (1979) state that "Some . . . birds reproduce 

alongside, under, or within logs." Their description of class 

2 logs shows that: elevated areas on logs may provide 

lookouts and feeding sites; trunks provide food sources for 

woodpeckers, especially pileated woodpeckers; limbs are 

used as perches and-when hollow-as nest cavities; root 

wads are used by flycatchers as perching sites, by grouse 

for dusting, and by juncos as nesting sites; and protected 
areas under the log are used as nesting cover by grouse. 

Bird species and their associations with DDW are 

summarized in table 3 (common names) and table 4 

(scientific names). 

Little information was found in the literature that related 

specific characteristics of DDW to bird populations. 

However, a few studies address the attributes of ruffed 

grouse drumming sites. Hale and others (1982) concluded 

that drumming sites in northern Georgia were strongly 

associated with a relatively dense understory of ericaceous 

shrubs, and that the structure of the understory was most 

critical in detemining grouse usage of logs as drumming 

sites. Thompson and others (1987), investigating habitat 

characteristics of drumming sites in oak-hickory forests in 

Missouri, found that use of drumming logs was most 

positively correlated with the density and structure of the 

vegetation surrounding the drumming log and not with 

characteristics of the log itself. Their study concluded that 

drumming logs had higher coniferous and deciduous shrub 

densities, coniferous canopy closure, understory foliage 

density, total woody stem densities, and slope position than 

randomly chosen logs. The density of deciduous trees and 

deciduous tree canopy closure were lower at confirmed 

drumming logs. 

Management of Snags and Down Dead 

Woody Debris 

Several management actions are proposed if adequate 

densities of snags are to be maintained in southern forests: 

1. Control the removal of dead, dying, and decayed trees 

(Cmichael 1983; Harlow and Guynn 1983; Land and 

others 1989; McComb and others 1986). 

2. Create snags by girdling, chemical injection, etc. 

(Carmichael 1983; Harlow and Cuynn 1983; McComb 

and others 1986). 

3. Preserve strips of unmanaged mature forest along 

drainage systems (Harlow and Guynn 1983). 

4. Increase rotation age, limiting the area of even-aged 

forests and avoiding the creation of forest islands (Land 

and others 1989). 

6. Emphasize tree species that are most likely to be 

recruited into the snag population (Sabin 199 1). 

Although no specific guidelines have been suggested for 

managing CWD in southern forests, Maser and others 

(1979) suggest that management within a forest for snags 

will naturally add to the DDW component as logs are 

recruited to the forest floor by decay and various physical 

forces. 

Conclusions and Recommendations 

Coarse woody debris is clearly an important habitat 

component for many species of birds in southern forests. 

However, little effort has been directed at documenting the 

use of CWD by birds and measuring its influence on 

species occurrence and diversity in these forests. Studies 

from the Pacific Northwest provide general inferences 

about the probable functions of CWD as habitat for birds in 

southern forests. However, studies documenting specific 

uses of CWD by bird species or guilds in various southern 

forest ecosystems are needed before meaningful 

management strategies can be developed. Other 

information needs include the following: 

1. Description of snag dynamics to include size 

distribution, recruitment and loss rates, decay rates, and 

stages of snags and DDW by tree species and forest type. 

2. Quantification of relationships between (a) volume, 

size, temporal and spatial distribution; (b) decay 

processes; and (c) living vegetation characteristics, and 

CWD use by bird species and guilds. 

3. Correlation of bird species richness and diversity with 

size distribution of CWD. 

4. Quantification of the relationships between 

occurrence and diversity of bird species with CWD 

characteristics through controlled experiments, such as a 

comparison of snagless plots with plots that have various 

densities of snags. 

5. Thin stands to create habitat conditions favorable to 

cavity-dependent bird species. 
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Cost, Noel D. 1986. Snag resources in Florida . . . are they sufficient 

for average populations of cavity nesters? Wildlife Society Bulletin. 

14:40-48. 

McComb, William C.; Muller, R.N. 1983. Snag characteristics in oldgrowth and second-growth Appalachian forests. Journal of Wildlife 

Management. 47:376-382. 

Miller, Eileen; Miller, Donald R. 1980. Snag use by birds. In: DeGraaf, 

Richard M., tech. coord. Proceedings, workshop on management of 

western forests and grasslands for nongame birds; 1980 February 11- 

14, Salt Lake City, UT. Gen. Tech. Rep. INT-86. Ogden, UT: U.S. 

Department of Agricuture, Forest Service, Intermountain Forest and 

Range Experiment Station: 337-356. 

Moriarty, John J.; McComb, William C. 1983. The long term effect of 

timber stand improvement on snag and cavity densities in the central 

Appalachians. In: Davis, Jerry W.; Goodwin, Gregory A.; Ockenfels, 

Richard A., tech. coords. Proceedings, symposium on snag habitat 

management; 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: 40-44. 

Sabin, Guy R. 1991. Snag dynamics and utilization by wildlife in the 

upper piedmont of South Carolina. Clemson, SC: Clemson University. 

49 p. M.S. thesis. 

Scott, Virgil E.; Evans, Keith, E.; Patton, D. R. [and others]. 1977. 

Cavity nesting birds of North American forests. Agric. Handb. 5 1 1 

Washington, DC: U.S. Department of Agriculture, Forest Service. 

112p. 

Terres, John K. 1980. The Audubon Society encyclopedia of North 

American birds. New York: Alfred A. Knopf, Inc. 1109 p. 

Thompson, Frank R.; Freiling, Deretha A.; Fritzell, Erik K. 1987. 

Drumming, nesting and brood habitats of ruffed grouse in an oakhickory forest. Journal of Wildlife Management. 51(3):568-575. 

Maser, Chris; Anderson, Ralph 6.; 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; 1979 September; Portland, 

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

Northwest Forest and Range Experiment Station; Wildlife 

Management Institute; U.S. Department of the Interior, Bureau of 

Land Management: 78-95. 
The Role of Coarse Woody Debris 

in the Ecology of Southeastern Mammals 

Susan C. Loeb 

Abstract 

Coarse woody debris (CWD) is an important habitat component for 

many mammals. At least 23 of the approximately 81 species of mammals 

found in the Southeast use standing CWD (snags) and at least 55 species 

use downed woody debris (logs). Snags are used for nesting, cover, and 

foraging whereas logs are used for travel routes, cover, nesting, and 

foraging. However, little is known about the characteristics of CWD that 

are important in determining its use by mammals, and even less is known 

about the availability of CWD resources in the Southeast. Before CWD 

can be effectively managed for mammals, several questions must be 

addressed: (1) Which species use CWD and for which of these species is 

CWD a critical habitat feature? (2) What function does CWD serve for 

each species? (3) What characteristics of CWD determine its suitability 

(e.g., size, decomposition stage, dispersion in the habitat)? and (4) How 

does use and importance of CWD vary with habitat and what 

environmental conditions control variation? 

Introduction 

The importance of coarse woody debris (CWD) to forest 

function and health has been well documented (e.g., 

Harmon and others 1986; Maser and others 1988b). 

Mammals use CWD for a variety of functions, and it is 

critically important to many species (Maser and others 

1979, 1988a; Thomas and others 1979). However, much of 

the research on the importance of CWD to mammals and 

other wildlife has been conducted in the Pacific Northwest. 

In the Southeast, data are available on standing CWD 

densities and its use by wildlife (e.g., Carrnichael and 

Guynn 1983; Harlow and Guynn 1983; McComb and 

others 1986a), but few studies have examined either the 

role or the availability of downed material. Furthemore, 

most studies dealing with standing CWD have evaluated 

available resources relative to the needs of cavity-nesting 

bird populations and few have addressed the CWD 

requirements of mammals. 

To egectively manage CWD for the mammals of the 

Southeast, it is necessary to know how CWD is used, what 

characteristics (e-g., size, decomposition state) determine 

its suitability, and how these characteristics change with 

Research Ecologist, Southern Research Station, U.S. Department of 

Agriculture, Forest Service, Department of Forest Resources, Clemson 

University, Clemson, SC 29863. 

time and environmental conditions. It is a large task to 

determine the usage of CWD for a group such as mammals. 

Although the Class Mammalia may not include as many 

species as other classes of animals, it is highly diverse. In 

the Southeast, body size ranges from 3 g for the pygmy 

shrew' to approximately 140 kg for the black bear. 

Moreover, while some mammals, such as pocket gophers 

and moles, are almost totally subterranean, others, such as 

flying squirrels, spend most of their lives in trees. Still 

others, such as mink and muskrat, are semiaquatic. 

Although most mammals are nocturnal, many species, such 

as most squirrels, are diurnal. Food habits also vary 

considerably, and mammals in the Southeast include 

insectivores (e.g., bats and shrews), herbivores (e.g., voles, 

cotton rats, beaver, deer), mycophages (e.g., northern flying 

squirrels), carnivores (e.g., weasels, bobcats), and 

omnivores (e.g., bears, opossums, white-footed mice). 

Given this variety of lifestyles, the role of CWD and its 

important characteristics will probably vary cansiderably 

among species or groups. Therefore, in the following 

review I discuss some of the general characteristics of 

CWD that may be particularly important to mammals, some 

of the important functions of CWD for mammals in 

general, and what is known about the use and availability 

of CWD in the Southeast. Finally, I will propose some 

areas and approaches for future research that will increase i 

our knowledge of CWD use by southeastern mammals. 

General Characteristics of Coarse Woody 

Debris and Its Use by Mammals 

CWD is usually categorized as standing or downed and 

referred to as snags or logs, respectively (Harmon and 

others 1986; Spies and Franklin 1988). These are 

important categories for mammals because use of each 

category varies considerably among species. Causes of tree 

death and the type of CWD debris produced by each 

mortality agent have been reviewed by Harmon and others 

(1986) and Maser and others (1988a). Although foresters 

usually define a snag as any broken tree > 6.1 m in height, 

for wildlife purposes snags are usually defined as any dead 

or partially dead tree > 10.2-cm diameter at breast height 

' Scientific names of all southeastern mammals are given in the appendix. 
(d.b.h.) and > 1.8 m in height (Thomas and others 1979). 

Because downed woody debris has rarely been measured 

for wildlife purposes, definitions of logs are rare 

(Cooperrider 1986). However, Spies and Franklin (1 988) 

defined logs as any woody debris > 10-cm diameter at the 

large end. Because this closely coincides with the 

definition of a snag, it is probably a good definition of 

downed CWD for wildlife purposes as well. 

Snags 

Snag characteristics potentially important to determining 

suitability for use by mammals include size (diameter and 

height), species, and decomposition stage. Several schemes 

for classifying snag decomposition have been devised for 

use in wildlife research. Thomas and others (1979) 

described nine stages of snag decomposition ranging from a 

healthy tree (Stage 1) to a stump (Stage 9), while Cline and 

others (1980) described five stages of snag decomposition 

and Sabin (1991) classified snags into three decomposition 

classes. Although these schemes vary considerably in the 

number of decay classes, criteria for distinguishing among 

stages in all schemes are based on some combination of the 

same three characteristics important to wildlife: (1) the size 

and number of limbs, (2) the amount of bark remaining, and 

(3) the amount of heartwood and sapwood decay. 

For mammals, the presence or absence of limbs Is probably 

not a critical element, although snags with many large limbs 

may contain more cavities than those without. In contrast, 

the presence or absence of bark and the amount of decay are 

very important. Many species of bats roost under loose 

bark (Hamilton and Whitaker 1979; Maser and others 

1988b). Therefore, the presence and abundance of loose 

bark will determine the utility of the snag for these animals. 

Decay is important because it is related to cavity 

excavation. The state of decay greatly influences the 

amount of time and energy necessary for cavity excavation, 

and it has a large bearing on whether birds will excavate 

cavities in a particular snag (Conner and others 1975; 

DeGraaf and Shigo 1985). For many mammals, the 

presence of cavities is the most important characteristic of a 

snag. Because mammals do not make their own cavities, 

they must rely on the presence of naturally occurring 

cavities or on primary cavity-nesting birds to excavate 

them. The state of decay may also affect the microclimate 

(e.g., temperature, humidity) and integrity of cavities 

influencing their suitability. However, I am not aware of any 

data pertaining to this aspect of snag decay. 

Cavities are important structures for several reasons. They 

provide cover from predators, particularly raptors, as well 

as shelter from the elements, such as wind and rain. They 

also provide a relatively stable thermal environment. For 

example, although average monthly temperatures inside 

and outside unoccupied raccoon dens in Illinois did not 

differ significantly, temperatures inside the dens varied only 

0.4 to 3.2 "C per day, while those outside varied 6.4 to 13.0 

"C per day (Stains 196 1). Furthermore, maximum and 

minimum outside temperatures (32 OC and -21 "C, 

respectively) were far more extreme than maximum and 

minimum temperatures inside the cavity (26 "C and -7 "C, 

respectively). This probably explains why species such as 

gray and fox squirrels, which use both cavities and outside 

leaf nests, increase their use of cavities during the winter 

(Edwards and others 1989; Weigl and others 1989). 

Cavities are also excellent structures for raising young. In 

addition to providing protection from ground predators and 

the elements, these semi-enclosed structures may also keep 

young animals from wandering away from, or falling out 

of, the nest. 

Bats are the primary arboreal insect feeders, and they do 

most of their foraging while flying. Therefore, snags are 

not usually considered an important food source for 

mammals. However, because many species of birds and 

mammals nest and rear young in snags (DeGraaf and Shigo 

1985; Maser and others 1988b), they may be a rich source 

of food for some of the semiarboreal predators such as the 

opossum, raccoon, and weasels. 

The availability of snags in the Southeast and various 

factors that influence snag availability have been examined 

in the mountains (McComb and Muller 1983; Rosenberg 

and others 1988), Piedmont Region (Carmichael and 

Guynn 1983; Sabin 1991) and Coastal Plain (Harlow and 

Guynn 1983; Land and others 1989; McComb and others 

1986a). In general, snag densities are lower in pine stands 

than in pine-hardwood and hardwood stands (Carmichael 

and Guynn 1983; Harlow and Guynn 1983; McComb and 

others 1986a; Sabin 199 1). Large snags (> 25-cm d,b.h). 

are far less abundant than snags < 25-cm d.b.h. (Carmichael 

and Guynn 1983; Harlow and Guynn 1983; McComb and 

Muller 1983; Rosenberg and others 1988; Sabin 199 1). 

This is important because cavities are far more likely to 

occur in large snags (Sabin 1991; Loeb, unpublished data). 

The relationship between snag density and stand age is not 

clear. While McComb and others (1986a) found that snag 

densities increased with stand age in pine and pinehardwood forests of Florida, Rosenberg and others (1988) 

found that little variation in snag density occurred among 

age classes of oak and oak-hickory stands in the Southern 

Appalachians. Moreover, Sabin ( S 99 1) and McComb and 

Muller (1983) found that snag densities decreased in older 
pine and pine-hardwood stands of the Piedmont and 

Coastal Plain, respectively. Digerences among studies may 

be due to differences in the age classes compared and their 

respective stages of succession (Waldrop 1995). 

Whether snag resources in the Southeast are adequate to 

support populations of mmmals that require them is 

unknown. Most studies on snag availability in the 

Southeast have related their findings to cavity-nesting birds 

(e.g., Land and others 1989; Rosenberg and others 1988; 

Harlow and Guynn 1983; Cmichael and Guynn 1983; 

McComb and others 1986a; McComb and Muller 1983) 

and no similar studies have been conducted for mammals. 

Logs 

Other than bats, almost all nonaquatic mammals spend at 

least part of their life on or under the ground. Therefore, 

logs have received more attention than snags in studies of 

mammalian ecology. Thomas (1979) defined a log as "any 

section of the bole or thicker branches of a felled tree after 

trimming and cross-cutting; also any section of the bole or 

of the thicker branches of a dead and down tree." Maser 

and others (1979, 1988a) classified logs into five stages of 

decay which correspond to the nine stages of snag decay 

described by Thomas and others (1979). Characteristics 

used to distinguish among classes include the amount of 

bark and twigs remaining, texture, shape, color, the portion 

of the tree on the ground, whether roots have invaded the 

log, and whether roots have invaded the sapwood or 

heartwood. 

Several studies have demonstrated that downed logs are an 

important habitat feature for many North American 

mammals, particularly small mammals (e.g., Bany and 

Francq 1980; Corn and others 1988; Gore 1988; Graves and 

others 1988; Kennedy and others 199 1 ; McComb and 

Rumsey 1982; Nordyke and Buskirk 1988; Planz and 

Kirkland 1992; Seagle 1985). Downed logs serve a variety 

of functions for terrestrial mammals ranging in size from 

shrews to bears. Initially, the soil disturbance and 

microsites provided by tree fall (Beatty and Stone 1986) 

probably provide foraging and burrowing sites for many 

species of mice, shrews, and ground squirrels. Logs also 

provide cover from both the elements and predators. 

Therefore, many species, such as gray fox, weasels, and 

striped skunks, as well as rodents and shrews, place their 

nests and dens under logs. 

Several studies have shown that mice use logs extensively 

as travel routes (Bmum and others 1992; Graves and 

others 1988; Olszewski 1968; Planz and Mirkland 1992). 

These rodents travel predominantly on top of the logs 

although Olszewski (1968) suggested that differential travel 

on top of and beneath, logs may be one way two species of 

mice in Poland (Apodemus fivicollis and Ckthrionomys 

glareolus) partition the habitat and avoid direct 

competition. Because travel on logs may be quieter than 

traveling among ground cover, particularly dry leaves, use 

of logs as travel routes has been viewed as a means of 

predator avoidance (Bamum and others 1992; Fitzgerald 

and Wolff 1988; Planz and Kirkland 1992). 

Few data on the importance of logs as feeding and foraging 

sites are available. However, an animal that moves to a log 

to process and eat its food (e.g., hard mast, pine cones, or 

other foods with long handling times) would have a higher 

vantage point for detecting predators while feeding, and 

easier access to cover if a predator is detected. The many 

species of insects that invade decaying logs (see Hanula 

1996; Savely 1939) would provide a rich source of food for 

terrestrial insectivores such as shrews. Larger species such 

as the madillo and raccoon are often observed digging 

through decaying logs for the invertebrates that inhabit 

them. Downed logs may also act as traps for winddispersed seeds and thus may be important foraging areas 

for seed-eaters such as Peromyscus spp. 

The fungi that invade decaying logs are also eaten by a 

variety of small mammals (Fogel and Trappe 1978; Maser 

and Maser 1987; Maser and others 1978). It has been 

suggested that mycophagy by small mammals is an 

important link in forest regeneration (Maser and others 

1979). After feeding on the sporocarps, the spores are 

defecated, often at a distance from the original source. 

Thus, small mmmals may be important dispersers of 

mycomhizal fungal spores, many of which are necessary for 

growth and suwival of conifers. Although most data on 

fungallsmall mammaVconifer relationships have been 

obtained in the Pacific Northwest, Weigl and others (1989) 

suggest that fox squimels, which forage on fungi in longleaf 

pine ecosystems of the Southeast, play a similar role. 

Many other species of mammals probably forage on fungi 

in the Southeast and play a role in fungal dispersal. 

However, few data are available on fungal consumption by 

southeastern mammals. 

The abundance of logs and the relationship between log 

availability and physiographic region, forest type, age, and 

history have not been detemined for the Southeast. Some 

data are available on log characteristics imporlant to 

detemining use by small mammals. Hayes and Cross 

(1987) found that use of logs by deer mice and western redbacked voles (C. cal$omicus) in Oregon was positively 
correlated with log length, log diameter, and overhang area. 

Overhang area was primarily responsible for variation in 

log use, while the decay stage had no effect. In contrast, 

white-footed mice in Minnesota and Maryland do not select 

logs on the basis of length, although they prefer logs > 5 

cm in diameter and avoid logs c 5 cm in diameter (Barnurn 

and others 1992). Fu&emore, they prefer soft logs that 

are either smooth or covered with moss and avoid hard, 

smooth logs, Differences between these studies may be 

due to different techniques (trapping vs. fluorescent 

tracking), habitats examined, and/or species studied. More 

studies are necessary to reconcile these differences. 

Use of Coarse Woody Debris 

by Southeastern Mammals 

Use of CWD by a particular species probably depends on 

mmy factors, including phylogenetic constraints (e.g . , 

morphology), natural history, and environmental 

conditions. For example, the gray fox is known to use a 

variety of den types including hollow logs or trees, rock 

outcrops, underground burrows constructed by other 

species, wood piles, and brush piles (Fritzell and Haroldson 

1982). However, structures such as logs, hollow trees, and 

snags probably become more important in areas where 

burrowing animals, such as ground squirrels (Spermophilus 

spp.), do not occur (e.g., the Southeast) than in areas where 

they are abundant. This example shows that use of CWD 

and its importance in fulfilling the requirements of an 

animal may vary among regions and even among habitats 

within regions. Therefore it is necessary to consider both 

the natural history of an animal and the environmental 

conditions, including the presence of other species, when 

evaluating the importance of CWD for a given species. 

Studies focusing on use of either snags or logs by 

southeastern mammals are rare. However, studies of 

natural history and habitat selection have documented their 

use by many species. The Appendix summarizes the uses, 

or possible uses, of snags and logs by each species of 

mmmal found in the Southeast. Primary sources for the 

appendix include general species accounts by Chapman and 

Feldhamer (1982), Hamilton and Whitaker (19"79), and 

others as cited. 

As shown in the appendix, both snags and logs are used by 

a variety of mammals, and logs are used by far more 

species than snags. Of the approximately 81 species of 

terrestrial mammals found in the Southeastern United 

States at least 23 species are known to use either cavities or 

the loose bark of snags, and an additional three species may 

also use snags. In contrast, at least 55 species are known to 

use logs, and at least 10 species use both snags and logs. 

Cavities in snags are used by a wide variety of southeastern 

mammals ranging from bats to raccoons. Some species 

probably use snags opportunistically and are not dependent 

on them for survival, For example, the opossum is a 

generalist in almost all aspects of its ecology (McManus 

1974), and although it often dens in cavities in snags, it also 

dens in or under logs, burrows, rock outcrops, hay stacks, 

vine tangles, and culverts (Gardner 1982). In contrast, 

several species of southeastern bats are highly dependent on 

cavities in snags for roosting sites; therefore, cavities are an 

important habitat requirement. Cavities are also an 

important habitat feature for the tree squirrels of the 

Southeast. Although fox squirrels use cavities infrequently 

during most of the year, they may need cavities for 

successful reproduction (Loeb and Moncrief 1993). In 

contrast, red squirrels, gray squirrels, northern flying 

squirrels, and southern flying squirrels commonly utilize 

cavities year round. Because live den trees may be scarce 

in many habitats (McComb and others 1986b), these 

squirrels may be dependent on snags for nesting sites. Deer 

mice, white-footed mice, and cotton mice also nest in 

cavities (Frank and Layne 1992; Wolff and Hurlbutt 1982), 

and Wolff and Hurlbutt (1982) found that deer mice and 

white-footed mice in Virginia prefer snags to live trees for 

nesting. Although woodrats are best known for their 

construction of elaborate stick nests or houses, eastern 

woodrats occasionally use cavities for nesting (Fitch and 

Rainey 1956; M. Strayer, personal communication), 

Bats are the primary mammals that use the area behind the 

loose bark of snags. At least five species of southeastern 

bats use the loose bark for protection, The Indiana bat 

often places its nursery colonies in these sites (Brady 

1983); therefore, snags with loose bark are a critical habitat 

component for this endangered species. 

Snags may also be used for foraging. Among southeastern 

mammals, opossums and raccoons are probably the primary 

mmmals that use snags as foraging sites. Both species are 

highly opportunistic omnivores (Kaufman 1982; McManus 

1974). They feed on grasses, forbs, fruits, nuts, 

invertebrates, small mammals, small birds, eggs, and 

carrion. Snags may be sources for such food items as eggs, 

young birds and mammals, and pMicularly invertebrates. 

Kennedy and others (1991) found that aeas used by 

raccoons in Tennessee and Kentucky had higher densities 

of snags than those areas that received little use. They 
suggested that raccoons selected these areas because the 

snags were impoflant sources of invertebrates for their diet. 

Logs serve a variety of functions for the 55 or more 

southeastern mammals. Many species, particularly the 

larger species, probably use logs in an opportunistic 

manner. For these species, logs may improve the quality of 

the habitat but are not critical habitat features. For 

example, species such as deer, mountain lion, and bobcat 

may readily use logs for cover, but other features of the 

habitat are probably far more important in detemining 

suitability and preference. 

In contrast, logs appear to be a critical habitat feature for 

many other species. Almost all descriptions of the 

preferred habitats of shrews include logs (e.g., Hamilton 

and Whitalcer 1979). Because they are extremely small, 

shrews almost always require cover from both predators 

and climatic conditions. Moisture is also an important 

habitat feature that influences the abundance and diversity 

of shrews (Churchfield 1990). Shrews have relatively high 

water requirements because of high evaporative water loss 

resulting from their extremely high metabolic rates. 

Furthermore, shrews feed primarily on insects and other 

invertebrates that, in general, are more abundant and more 

accessible in moist conditions. Because logs often retain 

moisture, they may provide favorable microsites for both 

shrews and their prey. How extensively shrews actually 

forage in or under logs is unknown, but some foraging 

around logs probably occurs. 

Logs are also an important habitat feature for many of the 

mice and rats found in the Southeast. Logs are important to 

microhabitat selection by deer mice and white-footed mice 

in some forest types (Barry and Francq 1980; Vickery and 

Rivest 1992) and are used extensively as travel routes 

(Barnum and others 1992; Graves and others 1988; Planz 

and Kirkland 1992). In addition, the number of cotton mice 

captured in longleaf pine (Pinus palustris) stands with large 

amounts of CWD is approximately double the number 

caught in similar stands where the CWD has been removed 

(Loeb, unpublished data). Even though the golden mouse 

is primarily arboreal and weaves a nest of grasses, leaves, 

shredded bark, or Spanish moss to the side of a tree or 

shrub, large communal nests are occasionally placed among 

the branches of fallen trees or under logs (Hamilton and 

Whitaker 1979; Linzey and Packard 1977). Logs are also 

important to both macrohabitat and microhabitat selection 

of Gapper's red-backed voles (Merritt 1981). The presence 

of red-backed voles in forests of the Pacific Northwest is 

often used as an indicator of old-growth forest conditions 

(Nordyke and Buskirk 1988); however, little research has 

been done on how logs are actually used by this species. 

These voles probably use logs for travel routes and cover, 

and because fungi make up a large portion of their diet 

(Fogel and Trappe 19781, logs may also be used for 

foraging. 

For many species, logs provide cover from the elements 

and predators. Species ranging from shrews to bears use 

logs for cover and many animals, such as mice, foxes, 

bobcats, and weasels, use the area under elevated logs for 

nesting sites. McCullough and Fritzell (1984) found that 

the majority of spotted skunk den sites in the Ozark Plateau 

were in hollow logs. Moreover, many species that den 

underground, such as foxes, armadillos, and mice, prefer to 

use dens with their entrances under or next to a log. 

Because logs also provide excellent cover from predators, 

species such as shrew, mice, rats, and rabbits probably use 

logs to hide or escape. 

Logs are probably an important foraging substrate for many 

southeastern mammals, particularly those that feed on 

invertebrates. Logs may be an important source of 

invertebrates for shrews, which are almost exclusively 

insectivorous. Decaying logs are also important sources of 

invertebrates for opossums, raccoons, skunks, and 

armadillos (Galbreath 1982; Godin 1982; Kaufman 1982; 

McManus 1974). These species often dig through decaying 

logs and forage on the variety of invertebrates found there. 

Taber (1945) also found that armadillos often foraged 

intensively in areas where logs had completely decayed. 

He attributed this behavior to increased humus in these 

areas. Logs may also have indirect benefits related to the 

foraging behavior of many species. For example, if the 

presence of logs increases the density of small mammals in 

an area, carnivores, such as weasels, foxes, and bobcats. 

may experience increased foraging efficiency. 

Future Research 

This discussion has shown that CWD is used by a wide 

variety of mammals. For some species, the presence of 

CWD is critical; for others it may be used only 

opportunistically. However, the importance of CWD is 

unknown for many, if not most, species. While this 

discussion has emphasized autecological processes and 

predator-prey relationships, the presence of CWD may also 

be important for other interactions, such as ameliorating 

competitive interactions. For example, by increasing 

limited resources such as nesting sites or prey availability, 
competitive interactions may be reduced and opportunities 

for habitat partitioning may be increased. 

Effective management of CMTD resources to benefit native 

mammalian species cannot occur unless the following 

questions are answered: (1) Which species use CWD and 

for which of these species is CWD a critical habitat 

feature? (2) What functions does CWD serve for each 

species? (3) What characteristics of CWD determine its 

suitability (e.g., size, decomposition stage, dispersion in the 

habitat)? (4) How do use and importance of CWD vary 

with habitat and what environmental conditions control 

variation? Until these and other questions are answered, 

evaluating present CWD resources is not possible. 

Several approaches to the study of the importance of CWD 

in mammalian ecology are possible. For example, 

researchers primarily interested in habitat selection will 

need only to add CWD measurement and characteristics to 

the more conventional vegetation measurements and habitat 

characteristics when doing traditional habitat selection 

studies. However, more specific studies are also needed to 

determine which species utilize logs and snags of various 

sizes and in various stages of decay, how CWD is used by 

various species, and how use varies with habitat. These 

studies may require techniques different from those used in 

studies of mammalian habitat selection (e.g., trapping and 

radiotelemetry ). For example, the fluorescent tracking 

technique (LRmen and Freeman 1985) has added greatly to 

our knowledge of how white-footed mice and deer mice use 

logs for travel. Other techniques, such as sand tracking 

(e.g., Vickery and Rivest 1992), smoke-paper-covered 

boards (Bailey 1969), or video cameras, may also be quite 

valuable in determining which species use logs and snags. 

In addition to testing the direct effects of CWD, examining 

indirect effects will also be necessary. For example, does 

the presence of CWD increase predator populations by 

increasing prey populations? Ultimately, research on the 

effects of CWD on mamalian populations will require an 

ecosystem approach, ranging from the ecosystem contained 

in individual logs or snags to the larger scale that includes 

entire forests, watersheds, or regions. 

Acknowledgments 

Partial funding for this project was provided by the 

Department of Energy, Savannah River Site, and the USDA 

Forest Service, Savannah River Forest Station. I thank 

D.C. Guynn and M. Strayer for helpful comments on earlier 

drafts. 

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Appendix 

Use of coarse woody debris (CWD) by mammals of the Southeastern United States and the physiographic regions in which they are commonly found-Coastal Plain 

(CP), Piedmont (PD), or Mountains (MT). Uses of CWD were classified as nesting or roosting (N), foraging (Fo), feeding (Fe), travel (T), and cover (C). A usage 

type followed by a "?" indicates that it is a possible usage but no confirming evidence has been found 

Scientific name Common name 

Snags- SnagsCP PD MT bark cavity Logs 

Didelphis virginiana 

Sora einereus 

Sara longirostris 

Sorex l?alustris 

Sorex fumeus 

Sorex dispar 

Sorex hoyi 

Blarina brevicauda 

Blarina carolinensis 

Cryptotis parva 

Parascalops breweri 

Scalopus aquaticus 

Condylura cristata 

Myotis luci,ugus 

Myotis austroriparius 

Myotis grisescens 

Myotis septentrionalis 

Myotis ~Qdalis 

Myotis leibii 

Lasionycteris noctivaguns 

Pipestrellus subflavus 

Eptesicus fuscus 

Lasiurus borealis 

Lasiurus sentinolus 

Lasiurus cinereus 

Lasiurus intermedius 

Nycticeius humeralis 

Plecotus townserzdii 

Plecotus rafinesyuii 

Tadarida brasiliensis 

Dasypus noventcinctus 

Sylvilagus palustris 

SylvikagusJloridanus 

Opossum 

Masked shrew 

Southeastern shrew 

Water shrew 

Smokey shrew 

Long-tailed shrew 

Pygmy shrew 

Short-tailed shrew 

SE short-tailed shrew 

Least shrew 

Hairy-tailed mole 

Eastern mole 

S tar-nosed mole 

Little brown bat 

Southeastern myotis 

Gray bat 

Northern long-eared bat 

Indiana bat 

Small-footed bat 

Silver haired bat 

Eastern pipistrelle 

Big brawn bat 

Red bat 

Seminole bat 

Hoary bat 

Northern yellow bat 

Evening bat 

Townsend's big-eared bat 

Rafinesque's big-eared bat 

Mexican free-tailed bat 

Nine-banded armadillo 

Marsh rabbit 

Eastern cottontail 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

N 

? 

? 

N 

N 

? 

N 

? 

? 

? 

N 

? 

Not used 

? 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

N,Fo 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

N 

N 

? 

Not used 

N 

? 

N 

? 

N 

N 

Not used 

N 

Not used 

N 

Not used 

N 

Not used 

Not used 

Not used 

Not used 

N,Fo,C? 

N,Fo,G 

N,Fo,C 

N,C 

N,Fo,C 

N,Fo,C 

N,Fo,C 

N,Fo,C 

N,Fo,C 

N,Fo,C 

Not used 

Not used 

N? 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

? 

? 

? 

? 

? 

? 

Not used 

Not used 

Not used 

Not used 

N, Fo 

C 

C 
G. 

i 2, a 

C 5 3 =. 42 g 

- X'a 

g 5 

E-' 

E e 

8 z 

2 fj 

aG 5% 

-3 g 3 .- 3 8 C 8, -.-( ,. c.Gn 

g%8 

'G ;b g .9 .a 

.$ - g 

28~ 

a .a 8 0 g-0 5~2 

"b I-rC 

go0 w2 9 *s 0 

5 -3 mX$ 

+ 33 

83 & 

cdr;(d 

E E-c .2 

,x E .z 

rims 

a .3 g 

33, 2,8%J 

-2 2 3 

8.9 " Kg.. @a = 8%" 

3g,x 

2~8 

g8 g 2 .& = 

Q, 28 g 3-* 

'aaaa'a aa'aaaa mama aa'aaaaaaa 

22X2X 

33s33 XXXX %X%XX%X%2 3333 333331333 zz5z.;; z555zz 'dz'dz zzzzzzzz5 zZZzzzzzZzzzzZzZzzzzZzZzZzzzZzZzz 

X XXXXXXXX X 

X XXXX X 

XXXXXXX XX*X 

XXX XXX X X X * 

XX X XXXXXX XXXXXXX X XX 
Use of coarse woody debris (CWD) by mmmals of the Southeastern United States and the physiographic regions in which they are commonly found-Coastal Plain 

(CP), Piedmont (PD), or Mountains (MT). Uses of CWD were classified as nesting or roosting (N), foraging (Fo), feeding (Fe), travel (T), and cover (C). A usage 

type followed by a "?'indicates that it is a possible usage but no confirming evidence has been found 

Scientific name Common name 

Snags- SnagsCP PD MT bark cavity Logs 

Canis latrans 

Canis rufus 

Vulpes vulpes 

Urocyon cineroargenteus 

Ursus americanus 

Procyon lotor 

Mustela nivalis 

Mustela frenata 

Mustela vison 

Spilogale putorius 

C 

Mephitis mephitis C 

00 Lutra canadensis 

Felis concolor 

Felis felis 

Odocoileus virginanus 

Coyote 

Red wolf 

Red fox 

Gray fox 

Black bear 

Raccoon 

Least weasel 

Long- tailed weasel 

Mink 

Eastern spotted skunk 

Striped skunk 

River otter 

Mountain lion 

Bobcat 

White-tailed deer 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

Not used 

N,Fo 

Not used 

Not used 

Not used 

N 

Not used 

Not used 

Not used 

Not used 

Not used 

N,Fo? 

N 

N ? 

N,Fo? 

N 

Fo 

Fa? 

N, Fo? 

N, Fo? 

N, Fo 

Fo 

N 

N?, T 

N, T 

C ? 
Influences of Coarse Woody Debris on Stream Habitats and 

Invertebrate Biodiversity 

J. Bruce Wallace, Jack W. Grubaugh, and Matt R. Whiles 

Abstract 

Coarse woody debris (CWD) serves a number of important roles in 

stream ecosystems. For example, it retains organic and inorganic matter, 

provides food for invertebrates, and serves as habitat for both 

invertebrates and fish. Stream invertebrates apparently further the 

decomposition of CWD in freshwaters by scraping, gouging, and 

tunneling wood colonized by microbiota. Evidence is presented that the 

distribution of CWD varies among streams in different Southeastern 

ecoregions. The impact of woody debris on the availability of food 

resources, invertebrate colonization, taxonomic diversity, and community 

structure differs greatly between Appalachian and Coastal Plain streams. 

The primary reason for this is the availability of other sources of stable 

substrata in the latter. We compare and contrast some of the effects of 

CWD on invertebrate communities among stream types of the 

Southeastern United States. 

Introduction 

Coarse woody debris (CW) has historically been 

considered a nuisance and an undesirable feature of 

Southeastern streams and rivers. Indeed, the removal of 

woody debris to ease navigation may well represent one of 

the first impacts of European settlement on Coastal Plain 

river systems. As early as 1801, the Georgia Legislature 

allowed for the formation of companies to conduct wood 

removal or "snagging" operations on the Altamaha, Oconee, 

Ogeechee, and Savannah Rivers (Clayton 1 8 1 2). Some 

snagging projects were continued well into the 20th century 

on larger rivers (Sedell and others 1982). 

The importance of woody debris in dictating stream 

ecosystem structure and function has been recognized only 

in the last few decades (e.g., Keller and Swanson 1979). In 

relatively high-gradient streams (slopes > 4 percent), woody 

debris retains allochthonous particulate organic matter, 

reduces stream-channel erosion, improves fish habitat, and 

serves as a substrate for many invertebrates and as a food 

resource for wood-feeding invertebrates (Bilby 198 1 ; Bilby 

and Likens 1980; Harmon and others 1986; Swanson and 

others 1982). In larger, low-gradient streams, woody debris 

has been shown to be a "hot spot" of invertebrate 

Professor of Ekology and Entomology and Graduate Students, 

respectively, Institute of Ecology, University of Georgia, Athens, GA 

30602. 

colonization, growth, and secondizry production (Benke and 

others 1984, 1985). 

Our objectives are to review the current state of knowledge 

on the inputs, decomposition, and distribution of CWD in 

southeastern stream ecosystems and to characterize the 

influence of woody debris on the functional structure of 

aquatic invertebrate communities. In particular, we will 

focus on the differing roles of woody debris in high-gradient 

Appalachian streams versus the low-gradient systems of the 

Coastal Plain. 

Coarse Woody Debris Inputs 

Sources, quantities, and timing of CW inputs are highly 

variable among Southeastern streams (Webster and others, 

in press). In upland streams with relatively stable channel 

courses, primary sources of woody debris are deadfalls and 

storm blowdowns. For the meandering, low-gradient 

systems of the Coastal Plain, most of the wood originates 

from large trees that fall into the streams as erosional banks 

are undercut (Benke and Wallace 1990; Wallace and Benke 

1984). Measured inputs of wood into upland streams of the 

Southeast range from 38 to 425 g mz yr-1 and from 34 to 

11 1 g ma yr-1 for Coastal Plain streams (Webster and others, 

in press). An unassessed source of woody inputs into 

Southeastern streams is the sequestering of woody debris by 

beaver. Woody debris inputs into Southeastern streams also 

tend to be highly episodic; recent examples include massive 

blowdowns from Hurricane Hugo in North Carolina and 

South Carolina (Putz and Sharitz 1991; Sharitz and others 

1992) and large inputs of woody debris into some 

Appalachian streams during the East Coast blizzard of 

March 1993. Because of such high spatial and temporal 

variability, comprehensive characterizations require 

long- term monitoring and measurement strategies over 

several decades; such studies are very rare. 

Decomposition of Large Woody Debris 

In terrestrial environments, where oxygen is rarely limiting, 

invertebrates enhance woody decomposition by constructing 

deep galleries into the wood interior, thus promoting 
fragmentation and increasing surface area available for 

microbial colonization. In contrast, oxygen concentrations 

within the interior of wetted wood are very low, which 

serves as a barrier to both microbiota and invertebrates. 

Hence, wood decomposition tends to be much faster in 

terrestrial than in aquatic environments (Harmon and others 

1986), where aquatic invertebrate colonization is primarily a 

surface phenomenon. 

Although limited to the wood surface, evidence shows that 

invertebrates promote decomposition by scraping, gouging, 

and tunneling wood colonized by microbiota (Anderson and 

others 1984; Dudley and Anderson 1982). These activities 

expose additional wood to further microbial decomposition 

(Anderson and others 1984). The wood-gouging habits of 

net-spinning caddisflies (Trichoptera: Hydropsychidae) can 

contribute to significant underwater damage of wooden 

structures. In 1988, a section of bridge spanning the 

Pocomoke River in Maryland collapsed (National 

Transportation Safety Board [NTSB] 1989). Subsequent 

investigation revealed that the untreated timber pilings 

exhibited a 53- to 58-percent reduction in cross-sectional 

area, which resulted in the collapse. The NTSB attributed 

the reduction to the combined effects of microbial 

decomposition and gouging by larvae of Hydropsyche 

incommoda, which had colonized the pilings (NTSB 1989). 

The gouged, oval depressions on the surface of these piles 

are identical to pitted wood colonized by H. incommoda, as 

well as other hydropsychids from many Coastal Plain 

streams. 

Distribution of Large Woody Debris 

in Southeastern Streams 

Differences in stream size and geomorphology influence 

patterns of distribution and retention of large woody debris, 

Small, high-gradient Appalachian streams are characterized 

by shallow, nmow channels having low stream unit power 

(Leopold and others 1964) and high channel roughness 

(Chow 1959). These features enhance the retention of 

woody debris and other particulate organic matter in the 

form of debris dams within the stream channel. Wallace and 

others (1982) showed the frequency of debris dams 

decreased with increasing stream size along a first- through, 

third-order stream gradient in Western North Carolina. 

More recently, a similar pattern was shown in a firstthrough, fifth-order gradient in an adjacent stream 

basin (fig. 1). 

Stream unit power tends to increase sharply in larger, 

high-gradient systems (Leopold and others 1964), where 

woody debris is often transported from the stream channel 

into the riparian zone during periods of high discharge. This 

phenomenon has been reported for many high-gradient, 

large-river reaches in Western North America (e.g., Minshall 

and others 1983; Triska and Cromack 1980), and is evident 

in some Appalachian rivers. In these systems, woody debris 

deposited in the riparian zone may stabilize substrata for 

growth of riparian vegetation, seed banks, and habitat for 

small mammals (R.J. Naiman, personal communication). 

Changes in geomorphology and riparian vegetation within a 

single lotic system can result in pronounced differences in 

woody debris distribution. A low-gradient, sixth-order reach 

of the Little Tennessee River near Otto, NC, drains a broad, 

alluvial valley and retains relatively large amounts of woody 

debris within its meandering stream channel. In contrast, a 

high-gradient, seventh-order reach of the same river 40 km 

downstream lacks an extensive alluvial valley and retains 

only small amounts of in-channel wood. In a second-order 

Piedmont system, Sweeney (1993) noted that woody debris 

volume was 27 times greater in portions of the stream that 

flowed through a forest than in a meadow reach immediately 

downstream. This distribution suggests downstream 

movement of wood is not an important process of Piedmont 

streams. 

In contrast to riparian deposition of woody debris in 

high-gradient Appalachian systems, large woody debris is 

generally retained within the stream channels of I 

'3 -r 

Ball Creek and Upper Coweeta Creek , 

Distance (m) from Headwaters 

Figure 1-Frequency of organic debris dams along a 5.6 km reach of Ball 

Creek and upper Coweeta Creek, encompassing stream orders 1 (extreme 

left) to 5 (right). 
low-gradient rivers on the Coastal Plain (fig. 2). Studies of 

the Ogeechee, a sixth-order Coastal Plain river, show higher 

standing stocks of woody debris in the river than in the 

riparian zone (cf. Cuffney 1988; Wallace and Benke 1984). 

Several mechanisms contribute to this phenomenon. First, 

water is diverted from the stream channel over the extensive 

floodplain during high-flow conditions, which decreases 

stream unit power (Roberts and others 1985). As a result, 

the stream lacks sufficient power to transport woody debris 

from the channel to riparian areas (Benke and Wallace 1990; 

Wallace and Benke 1984). Second, movement studies of 

tagged wood indicate that high-flow conditions actually 

sequester woody debris from the floodplain into the main 

channel (Benke and Wallace 1990). Finally, since wood 

decomposition is slower in aquatic than in terrestrial habitats 

(Harmon and others 1986), CWD in the river channel will 

tend to persist and accumulate while wood on the floodplain 

will decompose more rapidly and be less likely to 

accumulate. 

Woody Debris and Stream Invertebrates 

The effects of woody debris on stream processes and 

invertebrate communities can vary greatly depending on 

stream size, depth, cross-sectional area, discharge, gradient, 

Submeraed Wood Distribution 

Stream Width (rn) 

Figure 2-Top: mean depth profile of the Ogeechee River, with erosional 

bank as 0 regardless of bank orientation, i.e., west or east bank. Vertical 

fines represent 95 percent CI for depth (em) at 2-m intervals from 

erosional bank during low flow hydrogfaph (August 1983). Bottom: 

mean percentage of submerged wood volume within each 10 percent 

increment of width across an "average" transect with a mean channel 

width of 33-m (redrawn from Wallace and Benke 1984). 

and the availability and stability of inorganic substrates for 

invertebrate colonization. Existing evidence suggests that 

the impact of woody debris on the availability of food 

resources, invertebrate colonization, taxonomic diversity, 

and cornunity structure differs greatly between 

Appalachian and Coastal Plain streams. Below, we compare 

and contrast some of the effects on invertebrate communities 

among diverse types of streams fouild in the Southeastem 

United States. 

In high-gradient Appalachian streams, deposition of large 

woody debris results in a series of alterations to the physical 

structure of the stream. Upstream of debris dams, channel 

depth and width increase, water velocity decreases, and 

deposition of particulate organic matter and sediments is 

enhanced. As a result, local substratum characteristics are 

changed and overall physical heterogeneity of the stream 

channel is increased (Trotter 1990). This effect has been 

shown experimentally at the Coweeta Hydrologic 

Laboratory in North Carolina. Large woody debris was 

added to three of six cobble-riffle sites in 1988. Mean depth 

increased and velocity decreased immediately upstream of 

the log addition sites, and major shifts in substrate 

composition occurred as deposition of sand, silt, and organic 

matter buried the original cobble riffles. Storage of 

particulate organic matter increased sharply at debris 

addition sites relative to the untreated cobble-riffle 

sites (fig. 3). 

Cunningham Creek (Coweeta) 

600 7 Cobble riffles 

Leaf Wood Misc. FPOM 

Particulate Organic Matter 

Figure 3-Particulate organic matter (POM) standing crop (~r: SE) in three 

cobble riffles and three riffles to which logs were added "debris dams." 

POM storage did not differ significantly (ANOVA, p > 0.05) among 

reference riffles and "log addition riffles" prior to log additions or with 

reference riffles following log additions, whereas above were highly 

significant following debris additions (ANOVA, p < 0.001). FPOM is fine 

particular matter. 
Changes that alter the physical structure of stream 

ecosystems result in subsequent changes in the function and 

smcture of the invertebrate community as it responds to 

changes in food resource availability and the physical 

environment (e.g., Huryn and Wallace 1987, 1988, Molles 

1982). The debris dam addition experiment at Coweeta 

demonstrated these functional and structural responses. 

With decreased velocity and increased sedimentation, 

filtering and scraping invertebrates decreased sharply at the 

debris dam site relative to the untreated cobble-riffle sites. 

Gatherer invertebrates and trichopteran and dipteran 

shredders increased at the debris dams, presumably due to 

increased storage of particulate organic matter. Predators 

also increased, probably in response to the prey component 

of the community. Despite large increases in trichopteran 

and dipteran shredders, the total number of shredders 

remained virtually unchanged as a result of sharp declines in 

plecopteran shredders at the log addition sites. These results 

coincide with earlier studies in Coweeta streams, where 

depositional areas displayed very different faunal 

associations than those of cobble-riffles (e.g., Huryn and 

Wallace 1987), and provide direct experimental results for 

previous observations. 

The effects of woody debris on functional feeding group 

composition in small Coastal Plain streams differs from that 

described above for small Appalachian systems. For 

example, in a sandy, low-gradient headwater stream on the 

Virginia Coastal Plain, all functional groups except 

gatherers increased at debris darn sites (Smock and others 

1992), in contrast to the Coweeta debris-dam study where 

only gatherers and predators increased (figs. 4a and b). 

Similar to that of Appalachian streams, woody debris in the 

Coastal Plain stream retained large amounts of organic 

matter (Smock and others 1989), thereby increasing food 

resources for detritivores such as trichopteran and dipteran 

shredders (plecopteran shredders were absent from this 

stream). Woody debris also provided the primary stable 

substratum for filterers and scrapers in this sandy bottom 

stream, which contrasts sharply with debris dams in cobble 

bottom Coweeta strems. 

ce of large woody debris to the 

invertebrate communities of larger streams and rivers also 

differs between Appalachian and Coastal Plain systems, 

primarily due to the availability of other sources of stable 

substrata. The sixth-order reach of the Little Tennessee 

River contains substantial amounts of large woody debris, 

but the extensive cobble substratum is covered with a dense 

growth of the aquatic macrophyte, Podusternurn 

ceratuphyllum Michx., which affords a stable, 

three-dimensional habitat for invertebrate colonization. We 

compared the invertebrate community on woody debris to 

that of the Podosternurn-covered cobble substrate in this 

reach of the Little Tennessee River; invertebrate abundance 

and biomass were much greater on the Podostemum-covered 

cobble than on woody debris (fig. 5a). These results are in 

sharp contrast to those found by Benke and others (1984) in 

the Satilla River, a Coastal Plain system in Georgia (fig. 5b). 

The most abundant habitat in the Satilla is primarily shifting 

sand substrate, which supports very low-standing stock 

biomass relative to woody debris or snags (Benke and others 

1984). Other studies have also reported very high 

invertebrate production on wood habitats in Coastal Plain 

streams (Cudney and Wallace 1980; Smock and others 

1985, 1992). 

Cunningham Creek (Coweeta) 8000 1 

c 

-2 - Cobble riffles 

2 5 6000 II Debris dams 

7J 

2 4 

a 4000 

2 E 24 

c U) 8 E 2000 

a, 

0) 

0 

Scr. Shr. Gath. Filt. Pred. 

Buzzard's Branch (Coastal Plain) 10000 El Sandy sediments 

c II Debris dams 

.2 

c. - L 8000 

e 

3 $ 6000 

2 

4000 

C: U) 

8 E 2000 

8 

0 

Scr. Shr. Gath. Filt. Pred. 

Functional Feeding Group 

Figures -A) Comparisons of functional group production of 

invertebrates at debris dams and cobble riffles in a high-gradient 

Appalachian stream (Cunningham Creek; Coweeta; J.B. Wallace and 

others, unpublished data) with same (B) at debris dams and sandy 

substrates of a Coastal Plain stream, Buzzard's Branch, in Virginia 

(calculated from data of Smock and others 1992, using a DM to AFDM 

conversion of 0.85). 
Use of Woody Debris by Stream 

Invertebrates 

Some potential uses of woody debris by stream invertebrates 

are summarized in table 1. Many invertebrates, especially 

aquatic insects, use woody debris both above and below the 

waterline as a substratum for egg deposition. Wood may 

also be used as a direct food resource; Pereira and others 

(1982) examined gut contents of 108 taxa of lotic insects 

and found that 45 taxa had guts containing significant 

amounts of wood. Since wood often represents the most 

stable substratum in some streams, it provides attachent 

sites for feeding activities. Abundant crevices and loose 

bark of woody debris provide retreats and concealment sites 

Little Tennessee River at Otto, NC 

Snags 

gg Bottom 

Scr. Shr. Gath. Filt. Pred. 

4 Satilla River, Georgia 

$j 3 

cd .g Em3 .P I. " 'is 

x ZNE 2 

& 

231 Q 

g21 

5 0 

G -9 

n Y 

Scr. ~hr. Gath. Filt. Pred. 

Functional Feeding Group 

Figure 5-Top: (A) Comparison of standing stock biomass of invertebrate 

functional groups on wood substrates with that of the stream bed 

(primarily cobble and Podusremum-covered cobble) in the sixth order, 

Little Tennessee River near Otto, NC (J.W Grubaugh, unpublished data). 

Bottom: (B) Comparison of standing stock biomass of invertebrate 

functional groups on wood with that of the stream bottom (primarily sand 

and mud) in the Satilla River on the Coastal Plain of Georgia (from 

Benke and others 1984). 

for protection from predators. Some Trichoptera 

incorporate woody debris into their larval cases (Wiggins 

1977). For many endopterygote insects, wood provides 

stable substratum for pupation and important emergence 

sites for many groups such as Odonata, Ephemeroptera, 

Plecoptera, Trichoptera, and Diptera. Adult insects also use 

woody debris as resting sites. 

Coarse Woody Debris and Ecosystem 

Structure and Function 

In addition to its specific importance to the invertebrate 

community, the presence of CWD in Coastal Plain rivers 

exerts a profound influence on the structure and function of 

the entire stream ecosystem. 

Epixylic biofilms--organic layers consisting of rnicrobiota, 

extracellular pofysaccharides, and large quantities of trapped 

seston that coat submersed wood-are known to develop 

within a 2-week period following exposure of wood to river 

water (Couch and Meyer 1992). This rapid development of 

biofrlm corresponds well with invertebrate colonization on 

introduced woody substrates. Nilsen and Larimore (1973) 

reported rapid increases in invertebrate biomass and 

abundances during the first 2 weeks following log 

introduction to the Kaskaskia River in Illinois. Colonization 

of woody substrates introduced into several tributary 

streams of the Savannah River was also very rapid, with 

most species approaching steady state within 1 week 

following wood introduction (Thorp and others 1985). 

Filter feeders dominated initial colonization, followed by 

other functional groups, such as gatherers (Thorp and others 

1985). Hax and Golladay (1993) showed that 

macroinvertebrate abundances and taxa richness were 

positively correlated with biofilm on woody substrates. 

Rapid colonization of CWD by filter feeders is facilitated by 

their energy resources (e.g., organic particles and drifting 

animals). These resources are produced elsewhere in the 

system and delivered by the current, which represents an 

energy subsidy. Woody debris is necessary only as stable 

substrate; hence, colonization by filterers is not dependent 

on the developing epixylic biofilm. In Coastal Plain streams 

where substrate is limiting, invertebrate biomass on snags is 

generally dominated by filterers (e.g., Benke and others 

1984; Cudney and Wallace 1980; Smock and others 1985). 

However, for gathering invertebrates, flocculated, dissolved, 

organic carbon and fine seston particles of the epixylic 

biofilms represent a major food resource (Benke and others 

1992; Edwards and Meyer 1990); gatherer colonization of 

woody debris is thus influenced by biofilm availability. 
Table I-Some potential uses of woudy debris by invertebrates in Southeastern United States streams 

Use Comments Southeastern geographic region References 

Oviposition sites 

Direct food source 

Indirect food source 

(a) Retention of CPOMa 

(b) Retention of FPOMb and 

epixylic biofilm formation 

Attachment sites for 

(a) Feeding 

(b) Catchnet and retreat 

construction 

Above uses contribute to high 

invertebrate biomass 

Refugia from predators 

and drought 

Metamorphosis 

Aerial adult insects 

Eggs are often deposited on wood All-numerous examples Dudley and Anderson 1982; 

below and above the waterline among aquatic insects Merrit and Cummins 1984 

A few invertebrates feed directly All-Appalachians, Piedmont, Benke and others 1984; 

on wood by gouging, tunneling Coastal Plain Merrit and Cummins 1984; 

Pereira and others 1982 

Serves as food and relatively All--especially low-gradient Anderson and others 1984; 

stable substrata for Coastal Plain streams where Benke and others 1984; 

(a) Shredders unstable sand substrates exist; Dudley and Anderson 1982; 

(b) Collectors and scrapers minimum importance in large, Smock and others 1985, 1992; 

high-gradient rivers where there Wallace and Benke 1984 

is little wetted wood 

Important for filter-feeding taxa As above. 

such as larvae of black flies and netspinning caddisflies-in large lowgradient rivers, filterers dominate 

invertebrate biomass on snags 

Prey-rich patches for invertebrate 

and vertebrate predators 

Crevices, loose bark, etc., aid in 

concealment, woody debris 

improves moisture retention in 

intermittent channels 

Woody debris serves as a stable 

substratum for pupation as well as 

concealment under loose bark, etc. 

Emergence, adult resting sites, 

and copulation 

Indirect effects produced by Increased stream depth, reduced 

physical modification of channel current velocities modify physical 

characteristics and increase 

retention of organic material leading 

to increased habitat heterogeneity 

All--especially larger 

streams of Coastal Plain, 

where Odonata, Plecoptera, 

Megaloptera, and some 

dipteran predators are abundant 

Probably all regions; however, 

in small, intermittent headwater 

channels 

All-especially low-gradient 

Coastal Plain streams with 

unstable, sandy substratum 

All--especially larger streams 

and rivers of the Coastal Plain 

Primarily small, headwater 

streams, especially those 

draining high gradient reaches, 

where woody debris is 

responsible for high physical 

retention and exerts a strong 

influence on community 

structure 

Benke and others 1984; 

Cuffney and Wallace 1980; 

Smock and others 1985; 

Wallace and Benke 1984 

Benke and others 1984; 

Smock and others 1985; 

Wallace and Benke 1984 

Dudley and Anderson 1982; 

Everett and Ruiz 1993; 

Wiggins and others 1980 

Dudley and Anderson 1982; 

unpublished observations for 

the Southeast 

Dudley and Anderson 1982; 

unpublished observations for 

the Southeast 

Bilby 1981; 

Bilby and Likens 1980; 

Wuryn and Wallace 1987, 1988; 

Molles 1982, 

Smock and others 1989, 1992; 

Trotter 1990; 

Webster and others 1992; 

plus unpublished data 

"CPOM = Coarse particulate organic matter. 

FPOM = Fine particulate organic matter. 
High standing-stock densities and biomass of gatherers and 

filterers supported on CWD represent an abundant food 

resource for invertebrate predators such as Odonata, 

Plecoptera, and Megaloptera (e.g. Benke and others 1984; 

Smock and others 1985). The total invertebrate community 

on wood also serves as a major food resource for vertebrate 

predators. Benke and others (1985) have shown that 

snag-inhabiting invertebrates represent at least 60 percent of 

the gut contents of some fishes in the Satilla River. Clearly, 

woody debris in Coastal Plain streams enhances abundance 

and production of invertebrates and thus, higher trophic 

levels that depend on them for food. 

Large Woody Debris and Taxonomic 

Diversity of Invertebrates 

The presence of woody debris can serve as a mechanism to 

increase taxonomic diversity in a wide variety of 

Southeastern streams. This is especially evident in Coastal 

Plain systems. In the Satilla River, Benke and others (1984) 

found that 63 invertebrate taxa and over one-half of the 

standing stock biomass resided on woody debris, although it 

represented less than 6 percent of the effective substrate. 

Many of these taxa (45 percent) were exclusively found on 

woody substrates. In contrast, sandy substrates, 

representing 85 percent of the effective habitat surface area, 

had only 3 1 taxa, and muddy substrates (9 percent of the 

effective habitat) had 41 taxa present (fig. 6). 

We tabulated numbers of taxa present in several 

Southeastern stream studies where woody debris was 

incorporated into invertebrate sampling regimes (table 2); 

several points concerning the influence of wood on 

taxonomic diversity are evident. First, in one-half of these 

studies more taxa were found associated with woody debris 

than with stream-bottom habitats. Second, two of the three 

studies (Coweeta Creek and the Little Tennessee River), 

where bottom substrata had greater taxa abundances than 

woody debris, were conducted at sites having either 

abundant Podusternurn-covered cobble, cobble substrata, or 

both. Cobble provides an extensive substratum for 

invertebrate colonization. Finally, the proportion of taxa 

associated only with woody debris at all sites is substantial; 

it ranges from 13.7 percent to over 40 percent of total taxa 

found. Hence, woody debris does tend to increase the 

number of taxa within a given stream segment. 

Recommendations for Future Research 

and Management 

In the past, clear-cut logging practices involved removal of 

all trees without considering the importance to the streams 

of a sustainable supply of CWD. In the Appalachians, 

examinations of the result of such practices indicate 

long-term sediment and particulate organic matter losses in 

a number of streams (Webster and Golladay 1984; Webster 

and others 1988, 1992). In the Pacific Northwest, 

management efforts have been made, using tree size and 

distance from stream, to identify riparian trees that may 

provide sustainable yields of CVVD to streams (e.g., Robison 

and Beschta 1990). To our knowledge, such information is 

not available but is sorely needed for different regions of the 

Southeast. 

Information on the distribution of woody debris and 

associated invertebrate communities in streams of the 

Piedmont Plateau is sparse at best. Mulholland and Lenat 

(1992) suggest that because of disturbed conditions, 

Piedmont streams have received less attention than those of 

the Appalachians and the Coastal Plain. Preserving and 

restoring riparian areas should be an immediate step toward 

rehabilitation of Piedmont streams (Mulholland and Lenat 

1992). Protection of riparian vegetation is especially 

important in the Piedmont, where bank erosion is greatly 

Satilla River, Georgia 

Total taxa 

I- Taxa limited to habitat 

2 60 2 

.a 

2 

40 

- c 

yl. 

0 

20 

a 

E 

n - I I I 

Woody Sandy Muddy 

Debris Bottom Backwater 

(Snags) Habitat 

Figure Momparison of the number of invertebrate taxa collected from 

woody debris, sandy substrates, and muddy backwaters; and the number 

of taxa limited (and their percentage) to each habitat type in the Ogeechee 

River, Georgia. (Calculated from data of Benke and others 1984). 
Table 2-Number of taxa found associated with woody debris, stream substratum, and 

combined habitats in various southeastern streams 

Total number of taxa by habitat 

Location 

Taxa 

Debris dam Stream Combined exclusive 

or snags substratum habitats to wood 

Coweeta, NCa 66 75 87 14 

Lt. Tennessee River, NGb 21 36 44 18 

Buzzard's Branch, VAc 34 36 44 18 

Collier's Creek, VAc 27 20 33 39 

Cedar Creek, SCd 39 3 1" 47 34 

Satilla River, GAf 63 5 88 98 41 

Average 42 43 59 27 

a Wallace, unpublished. 

Grubaugh, unpublished. 

Smock and others 1992. 

* Smock and others 1985. 

Includes stream bottom and muddy banks. 

Benke and others 1984. 

g Includes sandy bottom and muddy backwaters. 

retarded by the anchoring effect of root wads of live and 

dead trees (Keller and Swanson 1979). 

The Stream Renovation Guidelines Committee (1983), 

established by The Wildlife Society and American Fisheries 

Society, examined various aspects of debris removal from 

streams. This cornittee acknowledged that only in a few 

situations is debris removal justified. While removal of 

organic debris may provide flood relief in the immediate 

area, it encourages unwise development of floodplain areas 

and may increase peak flows in downstream areas. Based 

on studies to date, there can be little doubt that debris 

removal results in the loss of impomnt invertebrate habitat 

(e.g., table 2). 

The relationships between damming activities of beaver, 

Castor canadensis, stream habitats, and macroinvertebrates 

in the Southeast are poorly understood compared to those of 

other regions (e.g., Naiman and others 1988). In other 

regions, the fauna of beaver dams difTer greatly from those 

of stream substratum. For example, Clifford and others 

(1993) demonstrated that invertebrate faunal assemblages 

differed greatly among beaver ponds, beaver dams, and 

main stream assemblages. Faunal assemblages of beaver 

dams share a number of functional similarities with those of 

debris dams, woody snags, and lake outlets (Clifford and 

others 1993). Hence, the addition of woody debris by 

beaver apparently increases the range of habitats available 

for invertebrates by increasing heterogeneity. 

Unfortunately, the extent to which the above studies, which 

were conducted in other regions, can be applied to the 

Southeast remains unknown. 

The extensive snagging operations on Coastal Plain rivers 

undoubtedly produced substantial hydrologic and energetic 

impacts on these systems. For example, over 15,000 snags 

were removed from the lower Satilla River in the late 19th 

and early 20th century (J.R. Sedell, personal 

comunication; Wallace and Benke 1984). Benke and 

others (1985) estimate that invertebrate production available 
as food resource for fisheries may have been reduced by as 

much as 70 percent by woody debris removal. Although in 

some situations the removal of woody debris may be 

warranted (i.e., to reduce and remove blockages and 

eliminate impediments to flow), managers should be aware 

of the vital role played by large woody debris in determining 

ecosystem structure and function in Coastal Plain streams 

(Benke and others 1985). Perhaps the best management 

practice for these streams is "no management" other than 

protection of the adjacent floodplains (Wallace and Benke 

1984). 

Conclusions 

The input and retention of woody debris, which is primarily 

the result of physical processes in low-gradient Coastal 

Plain streams, provides stable substrate for biofilm 

fornation and investebrate habitat in an environment that 

would otherwise be unsuitable for colonization for many 

species. In these streams, woody debris encourages 

taxonomic diversity, increases invertebrate biomass, and 

supplies food resources for higher trophic levels. In 

high-gradient Appalachian systems, CWD promotes habitat 

heterogeneity and resource availability through the retention 

of particulate matter, and retards down-wasting of the 

stream bed. Presumably, woody debris performs a similar 

function in Piedmont streams, but information regarding the 

distribution, invertebrate associations, and effective 

management strategies of CWD in these systems is sorely 

needed. 

Aldo Leopold (1941) pointed out more than a half-century 

ago that the dominant downhill movement of nutrients and 

materials is curtailed by the consumption, cycling, and 

storage function performed by the biota. In the decades 

since, we realize kopold's perceptive observations can be 

extended to large woody debris as well-especially in the 

context of lotic ecosystems. 

Acknowledgments 

Published infomation and personal communication 

concerning the Pocomoke Bridge collapse were supplied by 

Dr. Oliver S. Flint, Smithsonian Institution, Washington, 

DC. This work was supported by grants from the National 

Science Foundation and Cooperative Agreement 

12- 1 1-008-876, #I45 with the USDA Forest Service. 
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1 1356-68. 
Large Woody Debris, Fish Habitat, 

and Historical Land Use 

C, Andrew Dolloff 

Abstract 

Large woody debris (LWD) influences many ecologicail processes and 

plays a key role in the stmcture and function of habitats for a variety of 

aquatic species. Large woody debris influences sediment scour-fill 

patterns by deflecting Row; it delays and damps flood peaks downstream; 

and it decreases nutrient loss by trapping seston and inorganic sediments. 

Large woody debris is important to pool formation, which influences a 

stream's velocity, depth, and storage capacity. Pools are especially 

important to fish as refuges at times of stress, during droughts or floods, 

and as sources for recolonization. Heavy LWD loadings provide complex 

cover, protecting fish from predation, competition, and displacement; and 

may decrease the number of behavioral interactions, permitting greater 

numbers of fish to coexist. Stream loading of LWD is a natural 

phenomenon that has been drastically altered by human activity. Riparian 

areas should be managed so they eventually return to their presettlement 

role as a source of LWD. 

Introduction 

Large woody debris (LWD) plays a key role in the structure 

and function of habitats for a variety of aquatic species. 

Only recently, however, have land managers begun to 

recognize the value of LWD in maintaining biotic diversity. 

Even today, many managers of public lands and private 

corporations mandate debris removal from streams and 

rivers, citing benefits such as flood prevention or habitat 

improvement. Although careful removal of individual trees 

and debris accumulations may be justified for safe, efficient 

navigation of large rivers and to protect property or 

individual bridges, wholesale removal of LWD typical1 y 

results in dramatic changes in aquatic habitats. In this 

paper I review the relationships of LWD to fish and fish 

habitats. I also relate historical land use, primarily 

exploitative logging, to changes in LWD loading and fish 

habitat in the Southem Appalachians. 

Large woody debris is any piece of wood at least 10 cm in 

diameter at the small end and 1.0 m in length, including 

logs, branches, snags, or entire trees with attached root 

wads (Bisson and others 1987). Smaller pieces of wood 

are also important to stream ecology, providing benefits 

such as vital substrates and nutrients for macroinvertebrates 

and microbes. Because smaller pieces are more readily 

dislodged and transported downstream, they are less likely 

to influence channel morphology and habitat, Large woody 

debris is often a component of debris dams (along with 

many smaller pieces and detritus) that slow the flow of 

water, trap sediment and organic matter, and create 

microhabitats for fish and benthic macroinvertebrates 

(Bilby and Likens 1980). 

Functions of Large Woody Debris 

Large woody debris influences many ecological processes, 

including primary and secondary production, habitat 

formation, and control of sediment and water output 

(Harmon and others 1986). Many macroinveaebrates and 

microbes depend on LWD both directly for specific habitat 

needs and indirectly for food. All pieces of LWD that 

intersect the bank-full profile of a stream channel have the 

potential to modify channel morphology. When strems 

flow at or beyond capacity (bank-full discharge), LWD 

deflects flow and influences sediment scour-fill patterns, 

delaying and damping flood peaks in downstream areas. 

Large woody debris also traps seston and inorganic 

sediments, thereby decreasing the rate of nutrient loss 

(Golladay and others 1987). 

Large woody debris is a critical element of pool fornation 

in streams flowing through forested areas. Strems with 

few pools have low water storage capacities and 

consequently tend to have lower fish populations. Many 

species of fish require the lower water velocity and greaterthan-average depth provided by pools, In mountain 

streams, trout typically occupy and defend specific 

positions in pools from which they forage for insects and 

other drift food items. Pools are especially important when 

fish are under stress, such as during droughts or floods. 

After streamflow returns to normal, fish are able to 

recolonize from these critical refuges. 

Pools form around hydraulic roughness elements such as 

boulders, bedrock protrusions, and LWD (Sullivan and 

others 1987). LWD is an especially conspicuous poolforming element in small- to medium-sized streams flowing 

through old-growth forests (Andrus and others 1988). In 

the Southern Appalachians, many streams drain land that 

Project Leader, USDA Forest Service, Southern Research Station, 

Depaflment of Fisheries and Wildlife,Virgina Polytechnic Institute and was cleared 50-300 years ago, and most of these streams 

State University, Blacksburg, VA 2406 1-032 1. 
have lost much of their LWD. Large woody debris was 

deliberately removed at the time of logging, gradually 

depleted through decay, fragmentation, and downstream 

transport, or catastrophically flushed during floods (Silsbee 

and Larson 1983). The percentage of pools formed by 

LWD tends to be much lower in streams flowing through 

second- and younger-growth forests because riparian 

vegetation is not yet able to contribute large amounts of 

LWD (Flebbe and Dolloff 1991). Recent research, 

however, has shown that LWD is a component in at least 50 

percent of pools in Appalachian streams that flow through 

riparian zones ranging in age from 28 to 300 or more years 

(Hedman 1992). 

Large woody debris influences pool development in many 

ways. Plunge pools, dam pools, and backwater pools are 

three of the most common types of pool used by fish 

(Bisson and others 1982). Recent research has 

demonstrated that the deepest pools form behind pieces that 

are perpendicular to flow and are at least as wide as the 

stream channel (Cherry and Beschta 1989). 

Streams having high LWD loads tend to have complex 

habitat. Overhanging logs, debris jams, and root wads 

provide complex cover, protecting fish from predation 

(Everett and Ruiz 1993), competition, and displacement. 

Fish in pools with complex cover tend to be visually 

isolated, which may decrease the number of behavioral 

interactions and permit greater numbers of fish to coexist 

(Dolloff 1986; Fausch and Northcote 1992). Complex 

cover in deep pools is especially valuable during times of 

increased stress such as winter, or whenever flows are 

particularly high or low (Bustard and Narver 1975; 

McMahon and Hartman 1989; Tschaplinski and Hartman 

1983). Fish find shelter from flushing streamflows by 

moving into or behind LWD accumulations (Shirvell 1990). 

Elliott (1986) and Dolloff (1986) found that production of 

juvenile anadromous salmonids was greater where debris 

accumulations were left intact. Angermeier and Karr 

(1984) removed all LWD from one side of a small 

Midwestern stream that they had partitioned down the 

center with fine mesh hardware cloth. The side without 

debris had smaller amounts of litter, fewer species and 

lower biomass of benthic macroinvertebrates, fewer fish 

species, and smaller fish than the side where LWD was left 

in place. 

Debris removal lowers habitat complexity (Heede 1985; 

Lisle 1986), channel stability (Bilby 1984), fish numbers, 

smaller average size of fish, and biomass (Coulston and 

Maughn 1983; Dolloff 1986; Elliott f 986; Fausch and 

Northcote 1 992). Habitat simplification and subsequent 

decreases in residual LWD loading after timber harvest 

have also been implicated as a cause for long-term changes 

in the diversity of fish assemblages. Reeves and others 

( 1993) documented changes in the composition of juvenile 

salmonid assemblages after timber harvest in watersheds of 

the Oregon Coast range, where formerly abundant steelhead 

and cutthroat trout have apparently been replaced by coho 

salmon. 

Recent research on ecological disturbances has emphasized 

the importance of refugia (areas that remain habitable 

during extremes of drought, flood, or other disturbance) 

and the need for connectivity among stream channels and 

riparian zones (Meffe 1984; Naiman and others 1993). 

Fish and other aquatic organisms that find and use refuges 

are more likely to recolonize main stream habitats after a 

disturbance. The frequencies of occurrence, availability, 

and suitability of refugia greatly influence the stability and 

adaptability of aquatic systems. From small pieces in 

individual habitat units to large accumulations scattered 

throughout entire drainage basins, LWD features 

prominently in refugia of all types and sizes (Sedell and 

others 1990). In streams and rivers that have been 

channelized or detached from their floodplains, or that 

simply lack significant amounts of LWD, the variety and 

availability of refugia for aquatic organisms are greatly 

reduced. 

Input and Loading of Large Woody Debris 

Trees naturally enter streams after their root systems are 

undercut by flowing water. With their support systems 

weakened, these bankside trees are easily toppled by 

windthrow or the accumulation of ice or snow. Rates of 

LWD input depend on factors such as species and health of 

trees in the surrounding riparian zone, stream size and age, 

and patterns of past land use. Insect attacks and diseases 

may accelerate this process. Epidemics can greatly 

influence LWD loading. In the Eastern United States a 

blight virtually eliminating the formerly common American 

chestnut (Custunea dentutu (Marsh) Borkh.), has resulted 

in high LWD loads (except where intact chestnut logs were 

salvaged) composed primarily of blight-killed chestnut 

trees (Hedman 1992). The greatest input of LWD, however, 

can usually be traced to a specific event such as a flood, 

tornado, or hurricane; the amount of LWD in a small 

Appalachian watershed more than doubled after Hurricane 

Hugo swept over northwestern North Carolina (Dolloff and 

others 1994). 
Most in-stream LWD originates from a narrow strip along 

both sides of a stream channel. Over 70 percent of the 

LWD in streams flowing through mature and old-growth 

riparian zones in western Washington and Oregon 

originated within 20 m of the stream bank (McDade and 

others 1990). However, debris can be introduced from 

more distant sources on floodplains and hillslopes by floods 

or debris torrents (Benda and others 1992; Hack and 

Goodlet 1960; Keller and Swanson 1979). 

In general, the proportional loading of LWD is higher and 

its contribution to habitat structure is greater in headwater 

tributaries than in downstream rivers (Minshall and others 

1983). In parts of the Southeastern United States, however, 

LWD loading in some large rivers increases with increasing 

stream order (Benke and Wallace 1990). The observed lack 

of LWD in other large rivers, such as the Missouri and 

Mississippi, is in large measure a result of river 

management. Over 800,000 snags (average length 40 m) 

were removed from the lower 1,650 km of the Mississippi 

River between 1830 and 1880 to improve navigation 

(Sedell and Luchessa 1982). All across the United States, 

LWD was and still is removed wherever rivers serve as 

primary commercial routes (Sedell and others 199 1). 

The architecture of instream LWD is a function of stream 

size, the nature of the input process, and geomorphic 

characteristics of the site (Bisson and others 1987). In 

headwater streams many arrangements are possible, but 

generally pieces stay where they fall or move very little 

after input, because small streams have little power to move 

larger pieces. Large woody debris of all sizes may provide 

the nucleus for the formation of complex debris dams in 

small headwater streams (Bilby and Likens 1980). 

In intemediate-size streams, LWD tends to accumulate 

along the margins or at channel constrictions. Stream 

power is sufficient to float pieces from streambanks and 

upstream accumulations but many pieces still span the 

width of the channel, Submerged pieces can remain in 

place for many years, influencing channel morphology by 

creating side channels or meanders, and altering habitat 

formation by changing patterns of sediment scour and fill. 

In larger channels, LWD forms tight clumps at the heads of 

point bars and side channels, at islands, and along the 

outside curves of meanders. 

Large woody debris residence ranges from the time until 

the next high flow or hundreds of years, depending on site 

characteristics (stream size, channel shape, etc.) and wood 

size and quality (decay resistance, specific gravity, etc.). 

Smaller pieces have higher ratios of surface area to volume 

and lower proportions of decay-resistant heartwood than 

large pieces. Consequently, small pieces may have higher 

rates of fragmentation, abrasion, and decomposition, and 

disappearance through floatation may be higher for small 

versus large LWD (Hamon and others 1986). LWD 

loading follows a cycle of loss and replenishment in 

systems that have been undisturbed for a long time. As 

some pieces are lost or moved about, new pieces take their 

place, preserving the state of dynamic stability. 

Until recently, most people associated high loads of LWD 

with streams in the Pacific Northwest where up to 4,500 m3 

per ha were estimated in a stream flowing through a 

redwood stand in northern California (Keller and others, in 

press). Because of the long history of settlement and land 

clearing in the East, estimates of LWD loading tend to be 

much lower in southeastern streams (40-300 m3 per ha) 

(Harmon and others 1986). The most comprehensive 

inventory of LWD in Southern Appalachian watersheds 

showed that loadings were highly variable depending on 

land use and disturbance histories, the number and variety 

of riparian tree species, and the dynamics of American 

chestnut mortality. Large woody debris loadings, 

particularly those originating in mature and old-growth 

forests, were lower than expected and considerably lower 

than those in comparable streams in the Pacific Northwest 

(Hedman 1992). 

Despite their current low rates of loading, streams flowing 

through eastern forests probably would have substantial 

loads of LWD if the lands they drain had not been logged 

and cleared. Streams in unlogged watersheds in the Great , Smoky Mountains National Park contain four times more I 

LWD (338 m3 per ha vs. 84 m3per ha) than streams in 

watersheds logged before the park was established (Silsbee 

and Larson 1983), and Flebbe and Dolloff (1 99 1) found 

higher loads of LWD in streams flowing through unlogged 

vs. logged wilderness areas in two Southern Appalachian 

national forests. 

Impact of Past Land Use 

Land use has had a major impact on the loading and input 

of LWD in streams flowing through virtually all of the 

forested regions of the world. Human use has so changed 

the structure and composition of most forested watersheds 

that it is difficult for the average citizen to understand why 

LWD matters. Forests and rivers have been cleared and 

manipulated for centuries in Europe and Asia (Harmon and 

others 1986). 
Faced with the need to transport timber 20 miles down the 

shallow Saba River, late 12th century Japanese loggers 

" . . . constructed a succession of 1 18 temporary dams, 

each one raising the water level sufficiently to float the 

pillars (fogs 100 feet long and 5 feet in diameter) seaward a 

few score yards. They dredged the last 2 miles of the Saba, 

gaining enough water to float the pieces9' (Totman 1983). 

Many of Japan's larger rivers were "improved" during the 

17th century by the removal of rocks, sandbars, and debris. 

High up in the watersheds, villagers worked with hammers 

and chisels to reduce rough ledges to smooth channels. 

Where debris was abundant, the villagers diverted 

streamflow, loaded up the channel, soaked the 

accumulations in oil, and set them ablaze. After allowing 

the stream bottom to become heated, they diverted the 

water back into the stream channel, shattering the ledge 

which was then removed (Totman 1983). 

At about the same time, on the other side of the world in 

North America, logging and land clearing on a large scale 

was just beginning. As in other countries, stream and river 

"improvement" removed any hindrance to free flow and 

navigation. Because such a monumental task was beyond 

the means of the average citizen or municipality, Congress 

directed the U.S. Army Corps of Engineers to oversee the 

clearing and removal of many hundreds of thousands of 

snags, logs, and debris piles from rivers all across the 

United States from 1867- 19 12 (Sedell and Luchessa 1982). 

Although most of the easily exploited forest in the 

Southeastern United States had already been cut by 1880, 

vast reserves of high-quality timber remained deep in the 

southern mountains. Over 20,000 square miles of 

untouched forest in Kentucky was within easy reach of the 

Mississippi and its numerous tributaries (Sargent 1884). 

As timber supplies were depleted from readily accessible 

lowlands adjacent to larger rivers, lumber companies 

pushed into the mountains. There they encountered rough 

country and numerous streams that they "developed" into 

conduits for log transportation (Clark. 1981). Splash dams, 

flumes, and slides were common in parts of the Southern 

Appalachians wherever conditions pemitted (Brown 1936; 

Mastran and Lowene 1983; Rector 1949). 

One of the most spectacular splash dams was erected on the 

Russell Fork of the Big Sandy River at the town of 

Splashdam in southwest Virginia (Anon. 1910; Anon. 

19 12). From 19 10 to 12, the Yellow Poplar Lumber 

Company sent over 50 million board feet of yellow-poplar 

logs (average diameter 63.5 cm, length 0.5 to 11.5 m.) (fig. 

1) through the bays of its I f 0-m long, 7.5-m high concrete 

dam (fig. 2) and down the Big Sandy to its mill in Coal 

Figure I-Yellow-poplar trees, Dickenson County, Virginia, ca 1910. 

Grove, OH. The effects of the repeated torrerds of wood 

and water and accompanying stream improvements totally 

transformed the channel, which exhibits few signs of 

recovery today. 

Many other Appalachian streams were similarly 

transformed, including the Tellico in Tennessee. From its 

base of operations in Tellico Plains, the Tellico Lumber 

Company operated a system of splash dams in the upper 

Tellico River watershed. Over 1 million board feet of 

timber was used to construct three dams, each 122-m long 

and 12-m high, on the major forks of the TeIlico (fig. 3). 

Nearly 4,000 logs would be flushed weekly down the 

Telhco, even ". . . when there was not water enough in the 

river at the mill to wet one's ankles in wading across" 

(Anon. 1901). Here too, damage to the river was 

extensive; a hole 36-feet deep was worn in the rock below 

the outlet of one dam. 
Mountain streams continued to play an important role in 

log transportation even after railroads penetrated the 

mountains (fig. 4). This new technology actually 

accelerated the degradation of southern watersheds as 

stream gravels were mined to build roads, and rails were 

frequently laid directly over small stream channels (fig. 5). 

Companies frequently ran short lines to transport timber 

from remote coves and small drains to rollways and log 

dumps on the larger rivers. 

The use of streams and rivers for timber transportation 

persisted well into the 20th century. The Federal 

Government eventually acquired much of the cutover lands 

in the Southern Appalachians during the 1920's and 1930's. 

These "lands that nobody wanted and the streams that 

drained them have largely reforested and are managed by 

the U.S. Departments of Interior and Agriculture in national 

parks and forests (Mastran and Lowerre 1983). With the 

return of the forest, however, knowledge and understanding 

of the changes caused by past land use are fading from 

memory. 

Management of Large Woody Debris 

Many people and some governmental bodies do not 

appreciate the role that LWD plays in our streams and 

rivers. Others, however, embraced recent findings on the 

importance of LWD, halted expensive and unwarranted 

debris removal programs, and now manage for LWD 

recruitment. These new policies have created some 

credibility problems for managers and biologists. For 

years, loggers have been required to keep debris out of 

streams; now they see fishery and watershed managers 

discouraging stream cleaning and deliberately placing 

debris back in streams. Although enthusiasm for LWD 

typically runs high once its value is understood, a word of 

caution is advised: there is a difference between beneficial 

LWD and slash-typical logging residue composed of 

small trees, tops, and branches (Froelich 1973). Except in 

the smallest of streams, slash tends to be unstable and 

contributes little to instream habitat. However, individual 

trees that accidentally enter a stream should usually be left 

and counted as habitat enrichment rather than to risk 

damaging stream banks and accelerating erosion by 

removing them. 

measure of ecological integrity) to individual streams by 

direct addition of trees, this approach is clearIy not feasible 

on a large scale. Alternatively, given enough time many 

riparian areas will regain the characteristics of mature 

forests and provide LWD. Between these extreme 

strategies lies a range of management strategies-practical, 

long-term solutions that employ a mix of techniques to 

address both specific current shortages and long-term goals 

for natural LWD recruitment. 

To ensure adequate supplies for the future, recruitment of 

LWD must be included in the development of riparian 

management strategies. The diversity of riparian zone 

functions and values suggests that advocates for LWD must 

compete with proponents of other uses. For example, to 

preserve sources of LWD until understory trees mature, the 

salvage of trees killed by storm, fire, or insects may be 

limited to a specified distance from the streambank 

(Carlson and others 1990). 

The selection of appropriate species or assemblages to be 

managed for LWD depends on site suitability, decay 

resistance, and other riparian management objectives. For 

example: northern red oak produces hard mast and other 

benefits for wildlife, high quality timber, and decayresistant LWD (Perkey and others 1993). Eastern hemlock, 

while of lesser value for timber, provides thermal cover 

during both winter and summer and is very resistant to 

decay. 

During the last 20 years, increasing knowledge about the 

many functions of LWD has contributed greatly to both the 

science and practice of riparian ecosystem management. 

Understanding and appreciation of the benefits of 

interdisciplinary, integrated approaches to management 

should increase the abilities of present and future managers 

to address the increasing demands for traditional and 

potential new uses of riparian ecosystems. 

To provide sustainable amounts of LWD for the future, we 

must manage both the stream and the area where land and 

instream environments interact: the riparian zone. 

Although it is possible to temporarily restore LWD (and a 
Figure 2-Splash dam operated by the Yellow Poplar Lumber Company on the Russell Fork of the Big Sandy River, Dickenson County, 

Virginia, 1910. When filled to capacity, the mile long, 25-ft deep "pond behind the dam held over 35,000 logs. 

Figure 3-Splash dam on the Tellico River, ca. 1901. 
Figure 4-Logging in the Appalachian Mountains, 1912. Headwater stream channels made the best road beds. 

Figure 5-West Virginia Spruce Lumber Company salvage operations, 1908. 

136 
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f 

t 
Models and Management Implications of 

Coarse Woody Debris Impacts on Biodiversity 

Michael A. Huston 

Abstract 

Coarse woody debris (CWD) affects biological diversity in two ways: (1) 

it is a major contributor to habitat structure, and (2) it is a slow-release 

energy and nutrient reservoir. The relationship between productivity and 

biodiversity is complex, and the patterns of energy storage and species 

richness do not always coincide. The shifting landscape patterns of 

disturbance and productivity may lead to different levels of biological 

diversity among primary producers, herbivores, carnivores, and 

decomposers. For example, plant diversity appears to reach a maximum 

at low productivity, while carnivore diversity is greatest at high 

productivity. The effects of CWD on biodiversity appear most 

prominently in the decomposer food webs, which use the energy and 

structural diversity of the forest floor habitat to support a complex array 

of species. Management of CWD is potentially a major tool in managing 

biodiversity of these organisms. 

Introduction 

Coarse woody debris (CWD) is unique among ecological 

resources in that it simultaneously provides both physical 

structure and energy. Environmental heterogeneity, 

provided by the physical structure and species composition 

of plants, spatial variation in soil properties, and spatial 

variation in other biotic and abiotic environmentd 

properties, is probably the single most important factor for 

explaining local and landscape scale variation in 

biodiversity. Productivity, or the amount of available 

energy, is also known to have a strong positive effect on 

biodiversity in many situations. These two factors have 

been extensively investigated and discussed by ecologists 

from both empirical and theoretical viewpoints. (Grime 

1979; Huston 1979,1994; Tilman 1982; Rosenzweig and 

Abramsky 1993). 

Most of the sources of physical structure in the 

environment are relatively inert. For example, the massive 

calcium carbonate skeletons of corals, the rocky substrates 

of the intertidal zone, and the boles and branches of forest 

trees provide a physical structure that supports a great 

diversity of plants and animals, but in general does not 

provide a significant amount of energy or other resources 

that can be consumed by animals. However, when trees die 

and the chemical and physical protection of their woody 

structure decreases dramatically, the complex physical 

structure of the boles, branches, and twigs becomes a rich 

source of carbon-based energy. This energy supports a 

complex and diverse food web of fungi, bacteria, 

invertebrates, and vertebrates that alter the structure of the 

wood as they convert the cellulose, lignin, and other 

compounds to animal biomass and heat. Ultimately, the 

physical structure of the CWD disappears completely when 

all of the mass is converted to energy and living tissue. 

The effects of CWI> on biodiversity, and the effects of 

various management activities on CWD-related 

biodiversity, can be understood in the context of these two 

factors: (I) the available energy content, and (2) the 

structural properties of CWD. 

Productivity and Biodiversity 

The relationship between biodiversity and productivity has 

a long and controversial history in ecology. Productivity 

can be defined as the solar energy that is captured and 

converted into living tissue by plants (and eventually 

converted back into energy by humans and other 

organisms). Primary productivity is considered to be the 

amount of energy converted into plant tissue (measured as 

plant biomass), and secondary productivity is the amount of 

plant-derived energy converted into animal tissue 

(measured as animal biomass). We have good data 

and theoretical models demonstrating that higher 

productivity should be associated with higher diversity, but 

we also have good data and theory showing that diversity is 

reduced under the most productive conditions. These 

conflicting patterns have prevented the development of a 

comprehensive understmding of productivity -diversity 

relationships and slowed the development of guidelines for 

managing biodiversity in relation to site index and other 

estimates of productivity. 

The confusing patterns of biodiversity in relation to 

productivity can be understood if the properties of different 

types of organisms and different environmental conditions 

Research Associate, Environmental Sciences Division, Oak Ridge 

National Laboratory, Oak Ridge, TN 3783 1. 
are taken into account. The first step is to divide the 

multitude of organisms found in any ecosystem into groups 

based on their functional relationships with each other and 

with the entfironment. This subdivision is based on the 

well-known concept of ecological guilds, which are groups 

of organisms that are suficiently similar to one another that 

they are likely to compete for resources. Thus, competition 

is likely to be an important process within guilds, and less 

likely to be important between organisms from different 

guilds. 

Division of biodiversity into functional groups (guilds) of 

organisms provides a way of understanding why different 

groups of organisms may respond differently to the same 

environmental conditions. In particular, a given 

managernent activity is likely to lead to an increase in the 

diversity of some types of organisms and a decrease in the 

diversity of other types of organisms. 

Two very important envirisnmental factors that vary 

naturally across landscapes and are affected by virtually 

every management activity are (1) site productivity and 

(2) disturbance. These two factors provide a framework for 

understanding patterns of biological diversity in both 

natural and managed systems. Because biodiversity results 

from populations of organisms surviving and coexisting 

High 

ation Growth 

Rates 

Figure 1-Expected pattern of species diversity among non-competing 

organisms in relation to productivity (population growth rates) and 

disturbance (from Muston 1994). 

together, the general principles of population biology can 

be used to make predictions about patterns of biodiversity. 

In general, populations with many individuals are expected 

to have a higher probability of survival than populations 

with few individuals, and populations that can rapidly 

increase their numbers following a disturbance should have 

a higher probability of survival than populations that 

recover slowly. 

Because both population size and growth rates are 

influenced by the availability of resources in the 

environment, we would expect the greatest number of 

surviving populations-and thus the highest biodiversityunder productive conditions where resources availability is 

high. Disturbances that kill individuals decrease the 

probability of population survival; therefore, we would 

expect diversity to be highest under conditions where the 

frequency of disturbances is low (fig. 1). This pattern is 

found in some, but not all, situations. Specifically, it tends 

to be found among groups of organisms that do not 

compete strongly with one another, that is, organisms of 

different types. Since evergi ecosystem is composed of 

many different functional types of organisms, with some 

functional types having many species and others only a few 

species, the pattern predicted by figure Z is most likely to 

be found in groups of organisms composed of many 

Low High 

Rate of Population Growth 

and 

Competitive Disp 

Figure ?-Expected pattern of species diversity among organisms that 

potentially compete, in relation to productivity (population growth 

rate) and disturbance (from Huston 1994). 
diEerent functional types. It is less likely to be found in 

groups composed primarily of a single functional type. 

Among groups of organisms that can compete strongly, 

such as plants competing for light, diversity is often 

reduced under the most productive conditions when a 

dominant competitor excludes other species (fig. 2). 

What this means is that for an entire ecosystem, the total 

number of species (including bacteria, fungi, insects, 

plants, and vertebrates) is likely to increase with increasing 

productivity, but the diversity within any particular group of 

organisms may decrease drmatically even while total 

diversity is increasing. In general, plant diversity decreases 

with increasing productivity, while animal diversity, 

particularly of carnivores, increases with increasing 

productivity (fig. 3). 

Interactions between competition, which reduces diversity 

under productive conditions, and mortality-causing 

disturbances, which tend to prevent competitive exclusion, 

mean that not all groups of organisms will respond the 

same way to a change in disturbance frequency or intensity 

(e.g., burning, harvesting, etc.). This represents obvious 

problems for biodiversity management, since an increase in 

total forest diversity may be accompanied by a decrease in 

some groups of plants or animals that are of particular 

management concern. Consequently, simply increasing 

productivity is not necessarily a good management practice. 

Likewise, changing a disturbance regime is not likely to 

affect all groups of organisms in the same way. 

Coarse Woody Debris and Biodiversity 

Management 

No other manageable property of the forest environment 

has a greater impact on biodiversity than CWD. Even 

harvesting, which can in some cases act as a disturbance 

that increases tree diversity, probably has a greater effect on 

total forest biodiversity through the alteratiotl and removal 

of CWD than through its effect as a disturbance that 

"resets" forest succession. Because CWD provides two of 

the primary regulators of biodiversity- energy and 

heterogeneity-removal of CWD through harvest is 

potentially one of the most significant, and least 

appreciated, differences between managed and unmanaged 

forest ecosystems. The other chapters of this volume clearly 

demonstrate the critical role of CWD for virtually all 

components of forest biodiversity. 

Low Hgh 

Productivity 

Disturbance Productivity 

Figure 3-Predicted differences in diversity patterns among plants, 

herbivores, and carnivores in relation to productivity and disturbance. 

The diversity of plants tends to reach a maximum at low levels of 

productivity, while the diversity of carnivores tends to be highest at high 

levels of productivity (from Huston 1994). 

The relationship between the energy content and the 

structural heterogeneity of CWD is the key to CWD use 

for biodiversity management. Because structural 

heterogeneity decreases to zero as the energy content of 

wood is decreased to zero by decomposition, a continual 

input of CWD into a forest ecosystem is needed to maintain 

CWD-dependent biodiversity. The variable dimensionality 

of CWD, from thin twigs to massive boles, provides both a 

great range of spatial heterogeneity, and great variation in 

the time required for the structure and energy content to be 

reduced to zero. While branches can provide higher initial 

structural heterogeneity than large boles, more rapid 

decomposition reduces both the energy content and the 

structure to zero much more rapidly for branches than for 

boles. 

Both the energy content and structure of CWD are 

constantly changing through time, with energy decreasing 

continuously, while structural heterogeneity can increase 
during the early and mid stages of decomposition. These 

dynamics allow management to manipulate the CWD 

dynmics of a forest by altering the input of different types 

(dimensions) of CWD, Total diversity will usually be 

maximized by the combination of high energy input and 

high structural heterogeneity (fig. 4), and different 

dimensions (and energy content) of CWD will have 

different patterns and rates of change in energy/ 

heterogeneity. For example, logging slash can provide high 

heterogeneity and rapid release of energy following harvest, 

but unless boles and other large-dimension CWD are also 

left or later put into the system, both CVVD energy and 

CWD structure will rapidly drop to zero, with an inevitable 

reduction in many components of biodiversity. 

Low High 

Structural and Chemical 

Heterogeneity 

Figure &Patterns of diversity of CWD-dependent species that result 

from decomposition of CWD with various initial energy content and 

heterogeneity. (A) Lowest total energy content, low heterogeneity (e.g., 

small branch slash). This CWD rapidly decreases in total energy, 

heterogeneity and species diversity as a result of decomposition. 

(B) Low total energy, intermediate heterogeneity (e.g., medium and large 

branch slash). (C) Moderate total energy, relatively high heterogeneity, 

(e.g., branch slash and small boles). (D) High total energy content, low 

heterogeneity (e.g., large boles). This type of CWD takes much longer to 

decompose and reaches a higher level of heterogeneity and species 

diversity than smaller dimension CWD. Note that during decomposition, 

structural and chemical heterogeneity increase during the early stages, 

and decrease during the later stages, as total energy content drops to zero. 

CWD-dependent species diversity is continually changing over the course 

of decomposition as energy content and heterogeneity change. Diversity 

is expected to be maximum under conditions of highest energy content 

and structurallchemical heterogeneity. 

Because of the high host specificity of many fungal 

decomposers, high plant diversity (i.e., high chemical 

diversity of dead wood) can be expected to result in very 

high diversity of some types of decomposers. However, 

since high plant diversity is usually found on less 

productive sites, those CWD-dependent groups that are 

most strongly affected by energy supply, (insectivores and 

higher trophic levels such as carnivores) may not reach 

their highest diversity on these sites, and instead have 

maximum diversity on more productive sites (fig. 5). 

The amount of CWD-based energy in a natural ecosystem 

is clearly a function of forest productivity, as represented 

by site index. Management through thinning and harvest 

removes some portion of that energy, leaving a fraction of 

the amount that would be naturally available. This 

reduction in available energy (and structure) might be more 

critical on unproductive sites than on productive sites, but 

the possibility has probably never been evaluated. 

Plant Diversity 

a 

Low High 

Low 

.- 0 

.- 3 Generalist Herbiv -a > 

8 3 

Primary Productivity 

8 

Y0 

iii 

.a 

High 

3 

0, 

F 

m 

Figure 5-Expected response of species diversity to variation in CWD 

input (primary productivity) into a forest ecosystem for (A) species 

specialized on the structural and chemical heterogeneity of CWD; and 

(B) generalist species (fungivores, carnivores) that depend primarily on 

the total energy content of CWD. Specialist species respond primarily to 

woody plant diversity, which tends to be highest under low productivity 

conditions. Generalist species respond primarily to total energy 

availability, independent of the plant diversity (from Huston and Gilbert, 

in press). 

5 P 

z 

a 
is a critical factor in the biodiversity of 

forest ecosystems, providing both energy to support the 

complex food webs of the forest, and structural and 

chemical heterogeneity that allows the coexistence of many 

different species. CWD is greatly affected by most 

management activities, and is thus a management tool of 

potentially great importance in managing biodiversity. 

Literature Cited 

Grime, J.P. 1979. Plant strategies and vegetation processes. New York: 

John Wiley & Sons. 222 p. 

Huston, M.A. 1979. A general hypothesis of species diversity. American 

Naturalist. 1 13:81-101. 

Huston, M.A. 1994. Biological diversity: the coexistence of species on 

changing landscapes. Cambridge, MA: Cambridge University 

Press. 

Huston, M.A.; Gilbert, L.E. [In press]. Secondary production and the 

diversity of consumers. In: Orians, G.; Peralta, R., eds. Ekosystem 

processes and the biodiversity of tropical forests. Berlin: SCOPE/ 

Springer-Verlag. 

Rosenzweig, M.L.; Abramsky, 2. 1993. How are diversity and 

productivity related? In: Ricklefs, R.E.; Schluter, D., eds. Species 

diversity in ecological communities: historical and geographical 

perspectives. Chicago: University of Chicago Press: 52-65. 

Tilman, D. 1982. Resource competition and community structure. 

Princeton, NJ: Princeton University Press. 
Workshop Summary and Recommendations 

James W. McMinn and D. A. Crossley, Jr. 

Participants in the Workshop on Biodiversity and Coarse 

Woody Debris (CWD) in southern forests noted a general 

lack of information dealing specifically with forests of the 

Southeastern United States. Many data exist on the 

loadings and distribution of coarse woody debris (CWD), 

but these data are scattered and need to be organized into a 

viable database. Process studies (i.e., generation, 

decomposition, and dynamics) of CWD also need to be 

strengthened. From the standpoint of biodiversity, a large 

array of flora and fauna appear to be associated with CWD 

in southern forests, but the nature of those relationships is 

not well known. In particular, both the obligate nature of 

species assemblages related to CWD and the relative 

importance of CWD as a refuge from unfavorable climatic 

or anthropogenic events are unclear. However, CWD in 

Southern forests offers managers significant opportunities 

to affect and conserve biodiversity. 

Workshop recommendations emphasized the need for (1) 

approaches to use existing information, (2) additional 

research on the floral and faunal groups that use CWD, and 

(3) informed management direction. 

Specific Recommendations 

Inventory and Dynamics of Coarse Woody Debris 

in Southern Forests 

Compilation of forest survey data is needed to document 

CW loadings in southern forests. Survey data are readily 

available and analyses could dramatically increase 

knowledge of CWD across forest types, age classes, 

ownership patterns, and management practices. Further 

development of models that describe the dynamics of CWD 

and relate CWD dynamics to biodiversity are priorities. 

These models will facilitate analysis of the effects of 

management practices on CWD dynamics. 

Importance of Coarse Woody Debris 

for Biodiversity in Southern Forests 

The uses of CWD by flora and fauna in southern forests 

need to be studied. More specifically, research is needed 

on how stage of decay, spatial and temporal distribution, 

and stand structure affect CWD-use by given biotic groups. 

Coarse woody debris is clearly an important structural 

Project Leader, U.S. Department of Agriculture, Forest Service, Southern 

Research Station, Forestry Sciences Laboratory, 320 Green Street, 

Athens, GA 30602-2044, and Research Professor, Institute of Ecology, 

University of Georgia, Athens, GA 30602-2602. 

habitat variable. It may be especially important seasonally 

or in drought conditions. Both experimental and 

obsewational approaches are needed to isolate factors 

detemining the importance of CWD for biodikrersity. For 

studies of biodiversity of invertebrate organisms, the need 

for cooperation by systematists was emphasized, The 

development of local fauna lists, in cooperation with 

competent taxonomists, was viewed as an extremely 

important step toward knowledge of biodiversity in 

southern forests. 

Coarse Woody Debris and Biodiversity 

of Stream Systems 

Riparian zones deserve more attention, including 

experiments that delineate optimal width, estimate the 

stability of large woody debris in streams of different 

orders, and identify tree species that contribute to large 

woody debris in streams. Work should be undertaken to 

quantify CWD in streams in different physiographic 

provinces of the Southeast and the associated occurrence of 

biota. Process studies are needed to provide infomation on 

input, decomposition, movement, and colonization of CWD 

by invertebrate populations in all physiographic regions. 

Manipulative experiments should include additions and 

removals of CWD for analysis of effects on processes, as 

well as on the biodiversity of vertebrates and invertebrates. 

Considerations for Forest Management 

It is clearly premature for specific recommendations on 

managing CWD in the South. The dearth of information 

about CWD in southern forests provides an inadequate 

basis for such recommendations; however, some general 

considerations may be offered from the existing 

information. 

Forest floor ecosystems contain a set of microflora and 

fauna species that are interrelated ecologically. In general, 

any management practice that increases the spatial 

heterogeneity or resource base by providing a range of 

temporal successional patterns will increase the diversity of 

both microflora and fauna. A variety of size classes of 

CWD should remain available, and dispersal of CWD on 

the forest floor would increase microsite heterogeneity. 

Uneven-aged stands would promote a range of size classes 

of CWD. Shorter rotations may produce less CWD or 

fewer large classes of CWD, which may be especially 

critical. Fire management methods that yield cooler fires 

(winter fires or head fires) may have less impact on the 

diversity of forest floor biota. The highest diversity of 

species may occur in forests that are subject to repeated 

disturbance-the '"ntemediate disturbance" hypothesis. 
Workshop Participants 

John Blake 

USDA Forest Service 

Savannah. River Forest Station 

P. 0. Box 710 

New Ellenton, SC 29809-2279 

Telephone 8031725- 1807 

Ronald S. Caldwell 

Lincoln Memorial University 

Cumberland Mountain Research Center 

Harrogate, TN 37752-0901 

Telephone 6 151869-6227 

Fa 6 151869-4825 

H. Ronald Carroll 

University of Georgia 

Institute of Ecology 

Athens, GA 30602-2202 

Telephone 706f542-2968 

Fax 7061542-6040 

D. A. Crossley, Jr. 

University of Georgia 

Institute of Ecology 

Athens, GA 30602-2602 

Telephone 7061542-7832 

Fax 7061542-3344 

E-mail dac @ sparc.ecology.uga.edu 

C. Amdrew Dolloff 

USblA Forest Service 

Southern Rese~ch Station 

Virginia Polytechnic Institute and 

Slate University 

Depaflment of Fisheries and Wildlife Science 

Blacksburg, "Via 12406 1-032 1 

Telephone 703123 1 -48M 

Fa 703523 f -7580 

Jack We Gmbaugh 

University of Georgia 

Institute of kdsgy 

Athens, GA 30602-2602 

Telephone 706-542-7880. 

David Ce Grzgnn, Jr. 

Clemson University 

Department of Forest Resources 

Clernson, SC 29863- 1003 

Telephone 8031656-4830 

Fax 8031656-3304 

James L. Hanula 

USDA Forest Service 

Southern Research Station 

320 Green Street 

Athens, GA 30602-2044 

Telephone 706f546-2467 

Fax 7061546-2478 

Richard A. Hardt 

University of Georgia 

School of Forest Resources 

Athens, GA 30602 

Telephone 7061369-5757 

E-mail RHARDTOUGA 

Mark E. Harmon 

Oregon State University 

Department of Forest Science 

Corvallis, OR 9733 1-5705 

Telephone 5031750-7333 

Fax 503/737- 1393 

E-mail hmon@ flx.orst.edu 

Paul F. Hendrix 

University of Georgia 

Institute of Ecology 

Athens, GA 30602-2202 

Telephone 7061542-2968 

Fax 7061542-6040 

Michael A. Huston 

Oak Ridge National Laboratory 

Environmental Sciences Division 

B! 0. Box 2008 

Oak Ridge, TM 3783 1-6038 

Telephone 6 151576-800 1 

6 15f576-8646 

E-mail MKU@ ORBL.GOV 

John M. Jahnston 

University of Georgia 

Institute of Ecology 

Athens, GA 30602-2602 

Telephone 7061542-6557 

Fax 7061542-6040 

E-mail HILANDER@ UGA,CC.EGA.EDU 
J. Drew Lanham 

Clemson University 

Department of Forest Resources 

Clemson, SC 29863- 103 

Telephone 8031656-4830 

Fax 8031656-3304 

Susan C. Loeb 

USDA Forest Service 

Southern Research Station 

Clemson University 

Department of Forest Resources 

Clemson, SC 29863- 1003 

Telephone 8031656-4865 

F;ax 8031656-3304 

James W. McMinn 

USDA Forest Service 

Southern Research Station 

320 Green Street 

Athens, GA 30602-2044 

Telephone 7061546-244 1 

Fax 7061546-2478 

Karen K. Nakasone 

USDA Forest Service 

Forest Products Laboratory 

Center for Forest Mycology Research 

One Gifford Pinchot Drive 

Madison, WI 53705-2398 

Telephone 608123 1-92 12 

Fax 608123 1-9596 

E-mail FSWAlS=K.NAKASONU 

OU=S32A@MHS.AT"TMAIL.COM 

Diane Sanzone 

University of Georgia 

Institute of Ecology 

Athens, GA 30602-2602 

Telephone 706-542-6557 

Rebecca R. Sharitz 

Savannah River Ecology Laboratory 

Drawer E 

Aiken, SC 29802 

Telephone 8031725-2472 

Fax 8031725-3309 

Richard J. Snider 

Michigan State University 

Department of Zoology 

East Lansing, MI 48823 

Telephone 5 171355-8473 

Fax 5 171336-2789 

E-mail 23 1 18MGR@imb.cl.msu.edu 

David H. Van Lear 

Clemson University 

Department of Forest Resources 

Clemson, SC 29634- 1003 

Telephone 803/656-4857 

Fax 8031656-3304 

Thomas A. Waldrop 

USDA Forest Service 

Southern Research Station 

Clemson University 

Department of Forest Resources 

Clemson, SC 29634- 1003 

Telephone 8031656-5054 

Fa 8031656-3304 

E-mail T. WALDROP.529L07h 

J. Bruce Wallace 

University of Georgia 

Department of Entomology 

Athens, GA 30602-2202 

Telephone 7061542-7886 

Fax 7061542-2279 

E-mail wallace@ sparc.ecology.uga.edu 

Matt R. Whiles 

University of Georgia 

Institute of Ecology 

Athens, GA 30602-2602 

Telephone 706-542-7880 

The Forest Service, 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. To file a complaint, write 

the Secretary of Agriculture, U.S. Department of Agriculture, 

Washington, DC 20250, or call (202) 720-7327 (voice) or 

(202) 720-1 127 (TDD). USDA is an equal employment 

opportunity employer.