Links among landscape, habitat, and stream biology: Hierarchical relationships in streams of southeastern Michigan

D.M. Infante¹ and J.D. Allan².¹Institute for Fisheries Research, University of Michigan and Michigan Department of Natural Resources, Ann Arbor, Michigan 48109, ²School of Natural Resources and Environment, University of Michigan, Ann Arbor, Michigan 48109

Biological assemblages of streams are influenced by anthropogenic and natural landscape features acting through landscape’s effects on fluvial physical habitat. While many studies using correlative analyses support these relationships, identification of mechanisms by which landscape influences biology requires an understanding of covariation among measures and the ability to quantify hierarchical chains of influence. Using Covariance Structure Analysis, we examined relationships among the landscape, physical habitat, and fish and macroinvertebrates of 46 streams in southeastern Michigan. To identify potential differences in biota’s response to landscape factors, we summarized fish and macroinvertebrates by richness, diversity, and functional traits. Results emphasized complex interactions among the landscape, habitat, and stream biology. First, while natural landscape features exerted greater control over habitat than anthropogenic features, different aspects of habitat varied with different landscape features. Flow stability decreased with increasing imperviousness of catchment surficial geology, and habitat complexity increased with stream slope. Also, different organisms varied with different habitat features. Only fish varied with channel size, while only macroinvertebrates varied with substrate. Increasing flow stability did not affect the diversity and richness of fish, yet it was important to macroinvertebrates. Together, these results provide insights into the indirect influence of landscape on biology through physical habitat.