Stream Macroinvertebrate Community Responses as Legacies of Forest Harvest at the H.J. Andrews Experimental Forest, Oregon
To evaluate long-term effects of forest harvest, we sampled benthic and emergent macroinvertebrate communities in headwater streams through young-growth and old-growth forests in the H.J. Andrews Experimental Forest, Oregon, from June, 2003 to June, 2004. Thirty to forty years after harvest, macroinvertebrate density and richness did not differ among streams through young growth and old growth. Effects of deciduous riparian vegetation, including seasonal canopy openings and litterfall, continue to influence patterns of macroinvertebrate responses to forest harvest, as shown by higher densities of shredders in young-growth sites, the timing of emergence within basin pairs, and assemblage differences in two of the pairs of basins. The paired-basin design helped in distinguishing the specific influences of forest age from natural variability of macroinvertebrate distributions within the 5th order Lookout Creek basin. Our study suggests that understanding how macroinvertebrates respond to historical disturbances is enhanced by measures sensitive to changes in life history, such as rates of emergence, and to functional composition that reflect resource availability.