Longitudinal distribution patterns of headwater stream macroinvertebrates along intermittent-perennial gradients and implications of forest harvesting practices in a Cumberland Plateau catchment

Shifts in upland macroinvertebrate assemblages downslope from ephemeral to perennial channels are typically subtle and represents species-specific tolerances (e.g., diapause) to channel drying. As a precursory study to ecosystem structural and functional responses to alternative forestry treatments adjacent to streams channels of differing hydrologic permanency, macroinvertebrate communities were studied along an intermittent-perennial continuum in a Cumberland Plateau catchment. Forest stand age and disturbance history were virtually identical along and between study channels. All sampling was conducted in February and April 2004–2005. Five replicate samples were taken from 50-m long midstream and downstream reaches from ten separate study streams. Unpaired t-tests (combining midstream and downstream reaches) and one-way ANOVAs (midstream and downstream reaches kept separately) using species richness and functional feeding groups as dependant variables both revealed undetectable differences in macroinvertebrate assemblages between intermittent and perennial channels. In addition, rank curves plotting proportional abundance of each taxon against the corresponding taxonomic abundance ranking showed similar diversity patterns longitudinally. Overall, the similarities in assemblage structure between intermittent and perennial channels suggest that hydrologic gradients were relatively shallow. Forest cutting started in May 2008 with different alternative harvesting treatments in intermittent and perennial channels, with post-harvest sampling to begin in February 2009.