The Role of Aquatic Invertebrates in Processing of Wood Debris in Coniferous Forest Streams

Publisher Website
Google Scholar
Abstract
The wood-associated invertebrates were studied in 7 streams of the Coast and Cascade Mountains of Oregon [USA]. The amount of wood debris was determined in terms of both weight and surface area. Standing crop of wood per unit area decreases with increasing stream order. Invertebrates associated with wood were functionally categorized and their biomass on wood determined. Major xylophagous species were the caddisfly (Heteroplectron californicum), the elmid beetle (Lara avara) and the snail (Oxytrema silicula). Standing crop of these species is greater on wood in the Coast Range than in the Cascades, which is attributed to species composition of available wood debris. The density of L. avara was strongly correlated with the amount of wood available, irrespective of stream size within a drainage. The standing crop of invertebrates was about 2 orders of magnitude greater on leaf debris than on wood. A potential strategy for wood consumption, based on microbial conditioning, was presented. The data were used to develop a general scheme of wood processing by invertebrates in small stream ecosystems. Their impact is similar to that of invertebrates which process leaf litter in terrestrial and aquatic environments when the full decomposition cycle of wood debris is considered.