Landscape patterns and stream reaches in the Alaskan taiga forest: potential roles of permafrost in differentiating macroinvertebrate communities

Abstract

We investigated spatial variability in the community structure of stream macroinvertebrates at six reaches within Caribou-Poker Creeks Research Watershed in the Alaskan taiga forest. Stream reaches differed most notably in river continuum position (stream orders 1–4) and influence of permafrost. Permafrost may underly much of an entire watershed or may be only locally present in valley bottoms. Permafrost distribution influences hydrology, water temperature, and riparian vegetation. We sampled benthic macroinvertebrates six times during the ice-free season between June 1995 and June 1996. Mean invertebrate abundance (range: 1160–14494 individuals *#x2022; m-2) was significantly different among sites, the lower values occurring in stream reaches affected by the local presence of permafrost and the highest value in a headwater stream unaffected by permafrost. Taxonomic composition of the macroinvertebrate community also differed among reaches, with the quantity of watershed-level permafrost and stream size providing the strongest influences. This research highlights the importance of permafrost at two spatial scales (watershed and reach) for macroinvertebrate communities of headwater streams at high latitudes.