Multiple-scale landscape predictors of benthic macroinvertebrate community structure in North Carolina

Both riparian zone characteristics and watershed-wide landscape attributes affect the water quality of streams and rivers. Understanding the relative importance of these factors is significant for determining management and monitoring actions that adequately protect water quality and the ecological integrity of aquatic communities. In this study, we analyzed Geographic Information System-derived data to: (1) determine whether North Carolina benthic macroinvertebrate community structure is more closely correlated with landscape characteristics at the scale of riparian zones or entire watersheds; (2) understand which landscape attributes are correlated with aquatic invertebrate communities that reflect degraded stream conditions; (3) investigate whether the importance of streamside forest varies with watershed size. Watershed characteristics explained a greater amount of variability in macrobenthic community structure (69.5-75.4%) than riparian attributes (57.4-65.2%). While topographic complexity was the most important variable at all scales, different land cover characteristics were of secondary importance at both scales: developed land cover for watersheds, and forest cover at the riparian scale. The amount of riparian zone and watershed-wide forest cover accounted for more variability in small watersheds than in large watersheds.