Influence of large woody debris on stream insect communities and benthic detritus

We examined the extent to which benthic detritus loadings and the functiona l feeding group structure of stream insect communities respond to channel m odifications produced by experimental addition of large woody debris (LWD, entire logs) to Stony Creek, Virginia. Benthic detritus loadings per sample did not change after LWD additions, but large increases in pool habitats c reated by LWD increased net detritus by an estimated 27 kg (25%) in the 250 m of stream receiving LWD. A large increase in the proportional area of po ol habitats may result in a dominance of collector-gatherers and correspond ing decreases in shredders and scrapers. Functional feeding group community structure in pools was similar spatially and temporally. Riffles were spat ially convergent, but differed temporally. Community structure was signific antly different between pools and riffles. The results indicate possible la rge scale influences in overall community structure due to channel alterati ons by LWD, but little within-habitat change.