Coarse Woody Material Research Articles

Estimates of Down Woody Materials in Eastern US Forests

Down woody materials (DWMs) are an important part of forest ecosystems for wildlife habitat, carbon storage, structural diversity, wildfire hazard, and other large-scale ecosystem processes. To better manage forests for DWMs, available and easily accessible data on DWM components are needed. We examined data on DWMs, collected in 2001 by the US Department of Agriculture (USDA) Forest Inventory and Analysis (FIA) program on some plots in several states. We compiled DWM data from 778 plots to compute biomass for the following components: coarse woody material, fine woody material (three size classes), litter, duff, and shrub/herb cover. We developed regression equations to predict DWM components for extension to FIA’s more intensive plot network. Seven regression equations were applied to the FIA data to create maps of DWM biomass. As a first attempt to summarize FIA DWM measurements and extend them to plots without these data, our model produces reasonable results except possibly for duff and litter.

Technical Note—Amounts of Down Woody Materials for Mixed-Oak Forests in Kentucky, Virginia, Tennessee, and North Carolina

Abstract Fallen or down dead wood is a key element in healthy forest ecosystems. Although the amount of down wood and shrubs can provide critical information to forest resource managers for assessing fire fuel build up, data on biomass of down woody materials (DWM) are not readily accessible using existing databases. We summarized data collected by the USDA Forest Service's Forest Inventory and Analysis (FIA) program into biomass for mixed-oak forest types in Kentucky, Virginia, Tennessee, and North Carolina to obtain a baseline average for Appalachian mixed-oak forests. We sampled a subset of 76 plots from 16 oak forest types and computed biomass for each DWM component, using slightly different equations for each. Biomass of DWM components was summarized using simple statistics. The mean of all DWM components combined was 32 Mg/ha, and the median was 29 Mg/ha. Over half the mean DWM was duff and litter (18 Mg/ha combined); coarse woody material (CWM) was less than 15% of mean DWM; and fine woody material (FWM) (7 Mg/ha) was almost twice CWM. The range of mass for individual components was quite large. These estimates compare favorably to those found in studies for other forest types. South. J. Appl. For. 28(2):113–117.

Stand composition and structure of the boreal mixedwood and epigaeic arthropods of the Ecosystem Management Emulating Natural Disturbance (EMEND) landbase in northwestern Alberta

Conservation of biological diversity under the natural disturbance model of boreal forest management relies on the assumption that natural mosaics of stand composition and structure can be adequately recreated through forest management activities. Maintaining compositional and structural features that provide adequate habitat for species within managed stands is the basis of coarse-filter conservation strategies. Here we test the effect of stand composition and stand structure on the epigaeic arthropod fauna from four boreal mixedwood cover types in western Canada. We observed differences in epigaeic community composition and species-specific associations among each of the four cover types. Differences in the carabid fauna between cover types were defined by relative abundance of carabid species associated specifically with moss cover, forb cover, and of coarse woody material, rather than unique, stand-specific species compositions of the overstory. Cover-type differences were less apparent among the comparatively species-rich spider assemblages largely because of their low abundance in undisturbed stands. For the effective conservation of all species, our results suggest that coarse-filter management of mixedwood boreal forests must incorporate structural features beyond overstory canopy composition. Our analyses also suggest that activities directed at managing the amount of coarse woody material on the ground and understory plant composition, perhaps through variable retention harvesting, is a logical first step.

Saproxylic beetles (Coleoptera) using Populus in boreal aspen stands of western Canada: spatiotemporal variation and conservation of assemblages

Saproxylic beetles associated with Populus coarse woody material were sampled from two age classes of fire-origin aspen stands in north-central Alberta, Canada. A combination of rearings from wood bolts and window traps attached to snags yielded 9571 beetles representing 257 taxa over the 3-year period (1993–1995). We investigated faunal variation across regions, stand ages (mature, 60–90 years; old, >100 years), decay classes, wood types, and years in terms of species richness, abundance, and trophic differences. Although trophic structure was similar, faunal composition differed between the two study regions. Species richness and abundance were similar across stand ages; however, many species were collected exclusively or in great majority from old stands and from snags of large diameter, which suggested that truncation of stand age structure through widespread industrial harvest could have serious consequences for saproxylic assemblages. Beetle species richness increased with the level of wood decay, whereas the total catch of beetles tended to be higher in early stages of decay. Wood borer abundance tended to be higher in snags; however, total species richness was higher in logs. Our analyses suggest that (i) many beetle species in the Canadian boreal forest depend directly upon standing and fallen large-diameter woody material from Populus trees, (ii) variation in stage of decay is critical to beetle diversity, and (iii) provision for retention of representative old stands is critical to conservation of saproxylic communities.

A Field Test of Point Relascope Sampling of down Coarse Woody Material in Managed Stands in the Acadian Forest

We field tested a new method for sampling down coarse woody material (CWM) using an angle gauge and compared it with the more traditional line intersect sampling (LIS) method. Permanent sample locations in stands managed with different silvicultural treatments within the Penobscot Experimental Forest (Maine, USA) were used as the sampling locations. Point relascope sampling (PRS) with three different angles spanning the practical range of angles for such stands was used along with 40 m of LIS sample per sample point. Compared to LIS, the three angles resulted in similar number of pieces and volume of CWM from stands with different histories of repeated partial harvests. In terms of sampling efficiency, PRS was up to 4 times more efficient than LIS. These results, while limited to only one forest type and a relatively small sample, are the first published results available on the field performance of PRS.

Distribution and annual net accumulation of above-ground dead phytomass and its influence on throughfall quality in a Mexican tropical deciduous forest ecosystem

The amount and annual net accumulation of above-ground dead woody material were quantified in a tropical deciduous forest in western Mexico. Three plots were located within a small watershed (16 ha) and distributed along a 150-m-elevation gradient (Upper, Middle and Lower plot). Total amount of above-ground dead phytomass (fine + coarse) was 27.2 Mg ha-1. Coarse dead category (branches + logs) made up 70.6% (19.2 Mg ha-1) of the total. The rest comprised the fine fraction, which was lying on the forest floor as surface litter. Of the total coarse dead woody mass, 70.8% was standing, hanging or still attached to live trees (13.6 Mg ha-1). Dead wood net accumulation was 6.6 Mg ha-1 y-1; 58% of this was coarse woody material and the rest comprised the fine litterfall fraction. The amount of standing, hanging/attached dead branches (2-20 cm circumference) varied significantly among plots, with the highest value in the Upper plot. Dead wood net accumulation was similar between the Upper and Middle plots, and significantly higher than the Lower plot. Compared to the intact canopy, the removal of dead mass (hanging/attached dead branches and standing dead logs) caused a significant decrease in throughfall nutrient concentration and nutrient flux by this pathway.

Early colonization ofPopuluswood by saproxylic beetles (Coleoptera)

The early colonization of newly created coarse woody material (CWM) by beetles was studied in aspen mixedwood forests at two locations in north-central Alberta. Healthy trembling aspen (Populus tremuloides Michx.) trees, in old (>100 years) and mature (40–80 years) stands, were cut to provide three types of CWM: stumps, bolts on the ground (logs), and bolts suspended above the ground to simulate snags. Over 2 years, 1049 Coleoptera, representing 49 taxa, were collected. Faunal structure differed little between the two locations. Species diversity was higher in old than in mature stands, and higher in stumps and logs than in suspended bolts; however, these "snags" tended to have higher abundance when compared with stumps and logs. Overall beetle abundance and the catch of wood-boring beetles was significantly higher in the first year post-treatment, mainly because of the ambrosia beetle (Trypodendron retusum (LeConte)) and one of its predators, Rhizophagus remotus LeConte; however, beetle diversity was higher in the second year, suggesting that early wood-boring species may "precondition" the wood for a number of succeeding species. The high turnover rate of taxa and spatial or temporal variation in faunal structure suggests that effort focused on habitat classification of CWM will facilitate management to conserve saproxylic faunal diversity.

STRUCTURE AND COMPOSITION OF RIPARIAN BOREAL FOREST: NEW METHODS FOR ANALYZING EDGE INFLUENCE

Riparian ecotones at lakeshore edges are prominent features on the hetero- geneous boreal forest landscape. We introduce a new method (the critical values approach), which incorporates inherent variability in interior forest, to quantify distance of edge in- fluence at lakeshore forest edges. We use this method to examine the variation in forest structure and composition along the lakeshore forest edge-to-interior gradient in the mixed- wood boreal forest. Our objectives were: (1) to quantify distance of edge influence for forest structure and composition at lakeshore forest edges; and (2) to investigate spatial pattern in vegetation along the edge-to-interior gradient. Trees, coarse woody material, saplings, shrubs, and herbs were sampled in plots at varying distances along 200-m transects established perpendicular to lakeshore forest edges. Distance of edge influence was deter- mined by comparing mean values at different positions along the transect to critical values established from a randomization test of interior forest data. The spatial pattern of four selected species along the edge-to-interior gradient was assessed using split moving window analysis and wavelet analysis. The results suggest that a distinct lakeshore forest edge community exists. This community was ;40 m wide and was characterized by greater structural diversity, larger amounts of coarse woody material, and more saplings and mid- canopy trees than interior forest. Distance of edge influence for understory composition was generally greater than for forest structure. Patterns of response for different species along the edge-to-interior gradient were related to shade tolerance. Lakeshore forest edges are distinct landscape elements, but their prominence depends on the reference forest, species, and scale.

Defecation Rates of Mule Deer

Pellet-group counts were made with penned mule deer (Odocoileus hemionus) over a period of 12 years. The defecation rates observed were somewhat higher than those commonly assumed, being from 13 to 14 groups per day. Weights of pellet groups, the number of pellets per group, and pellet size were too variable to provide any assistance in identifying fecal deposits of individual animals. Foraging juvenile animals exhibited higher rates of defecation than did mature animals; therefore, age classifications are important to accurate censuses. The rates of yearlings seldom differed significantly from older animals. The level of forage intake affected the rate of defecation. Rates must be expressed in terms of the weight of the animal; otherwise, juvenile animals with low forage consumption and high rates mask the effect. Also, the kind of forage eaten affected the number of defecations. Barring mildly laxative effects of concentrates and possibly succulent forage, coarse woody material usually produced higher defecation rates than the same amounts of more nutritious food. Data obtained from field counts with known populations of deer gave generally lower values than were found in the pens, but failure to locate pellets may have been an important factor. The validity of counts in dense vegetation in the summer is highly questionable. Statistical analyses of counts made on winter ranges indicate more than 200 plots of 100 square feet each in size may be required for reasonable accuracy with high deer populations. The 100-square-foot plot size, though a convenient area for counting, is possibly too small a sample. Four such plots in a cluster seem to be a better basis for the individual observation. Further modification of the plot to 108.9 square feet so that each observation would represent 0.01 of an acre would facilitate computation. Counting pellet groups is a technique used to determine populations and distribution of game animals. This technique necessitates knowing the defecation rate of the animal to establish the size of the population, otherwise pellet-group counts only indicate relative numbers and distribution of animals. Furthermore, where animals occupy a range for only part of the year, uncertainty with respect to arrival and departure dates of the animal may prevent the determination of animal numbers. Bennett et al. (1940) first proposed the pellet-group technique for comparing white-tailed deer (Odocoileus virginianus) populations, but they provided no data on defecation rates. Rasmussen and Doman (1943) made counts of pellet groups in enclosures where the mule deer populations were known. Their findings first made possible the conversion of pelletgroup counts to deer populations. More recently data have been reported that are somewhat at variance with figures rereported by them. The data reported herein provide additional information on defecation rates of mule deer and some problems encountered in sampling and identifying pellet groups in the field.