For two years, in southwestern Wisconsin, Weigel et al. compared aquatic macroinvertebrate assemblages among stream segments within continuously grazed pastures, intensive rotationally grazed pastures, undisturbed grassy vegetative buffer strips, and undisturbed woody vegetative buffer strips. The results for macroinvertebrate response to watershed condition demonstrated that substantial, inherent differences among stream are likely to persist, even with careful selection of similar streams from one ecoregion in the study. Evidence showed that macroinvertebrate assemblages change within about 100-300 m of stream in response to riparian land use treatments after the authors statistically accounted for watershed differences between streams. The mean pollution tolerance value indicated a marginally significant difference between continuously grazed and woody buffer reaches. Results also showed that continuously grazed reaches, the reaches with the most erodible banks and embeddedness of coarse substrates, have the highest species richness and lowest representation of EPT taxa. Overall, these results demonstrate the importance of accounting for inherent stream variability in comparative analyses of multiple streams. Macroinvertebrate assemblages primarily respond to large-scale watershed influences such as land-cover.
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