Relations among larval tailed frogs, forest harvesting, stream microhabitat, and site parameters in southwestern British Columbia

Amphibians are the most abundant vertebrates in many forests and have the potential to play a significant role in ecosystem dynamics. We examined the effects of logging on larval Ascaphus truei Stejneger in low-order streams. Density, biomass, and mean snout-vent length were greatest in streams flowing through old growth; however, effects associated with forest harvest depended on elevation, stream size, percent cover of sand, boulders, runs, and riffles. Density and biomass were highest in high-elevation streams where silt and algae were absent and where temperature and percent cover of sand were lowest. Larvae appeared to select pool, run, or riffle microhabitats depending on their body size or developmental stage, with larger and more developed larvae occupying faster stream sections. Logging history appears to have less influence on Ascaphus variables than do stream microhabitat and site. In our study, over 86% of the variation in both density and biomass was associated with stream and site parameters. Because our results suggest that forest disturbance has major impacts under only certain conditions, we recommend that the variability of stream microhabitat and site parameters be considered prior to making harvesting decisions when managing for Ascaphus and other organisms with similar habitat requirements.