Relationship between riparian vegetation and stream benthic communities at three spatial scales

We examined the influence of riparian vegetation on macroinvertebrate community structure in streams of the Upper Thames River watershed in southwestern Ontario. Thirty-three mu-basins (129-1458 ha) were used to identify land cover variables that influenced stream macroinvertebrates. Micro-basins represented the entire drainage area of study streams and were similar in stream order (first, second) and land cover (agricultural or forest; no urban). We described the structure and composition of riparian vegetation and benthic macroinvertebrate communities at the outflow reach. The nature of the land cover was quantified for the stream network buffer (30 m) and the whole mu-basin. The objective of this study was to measure the magnitude and nature of the relationship between the riparian vegetation and benthic macroinvertebrate community at the outflow reach, stream network buffer, and whole mu-basin scales. Taxon richness (including total number of Ephemeroptera, Plecoptera, and Trichoptera taxa) and Simpson's diversity of the macroinvertebrate community all increased with increased tree cover in the riparian zone at the outflow reach scale. Simpson's equitability was lower with greater agricultural land cover in the stream network buffer. No relationship between the macroinvertebrate community and land cover was found at the whole mu-basin scale. Analysis of the influence of land cover on stream communities within a spatial hierarchy is important for understanding the interactions of stream ecosystems with their adjacent landscapes.