Aquatic Biological Diversity Responses to Flood Disturbance and Forest Management in Small, Forested Watersheds

We examined riparian system responses to an extreme rainfall event on 1–4 December 2007, in eleven small watersheds (mean area—13.2 km2) from 2008–2016 at debris flow, high flood, and low flood reaches (all extended overbank flows). Macroinvertebrate followed expected outcomes after disturbance including increasing chironomids other multi-voltine species. A core assemblage of twenty abundant common species-maintained populations even flow (likely by recolonizing quickly) with total richness during project 253 183 rare species (<0.01 abundance) supporting annual turnover 22 33%. Primary changes habitat were declines shade in-channel wood all reaches, more strongly reaches. communities across intensities became increasingly similar the storm. Combined effects reducing channel complexity previous logging decreasing recruitment systems, limits complexity. Until this feature forested watershed streams returns, there appears be a ceiling reach scale aquatic biological diversity.