Responses of macroinvertebrate communities to 4 years of deer exclusion in first- and second-order streams

Abstract

We compared hydrological environments and macroinvertebrate communities in 1st- and 2nd-order streams between a deer-excluded catchment (EC) and a control catchment (CC) to test effects of deer-induced hillslope soil erosion and sedimentation on macroinvertebrates. Overland flow contribution to the streams was greater in CC than in EC, and substrate in 1st-order streams contained more fine sediment in CC than in EC, whereas fine sediment in substrate in 2nd-order streams was similar between catchments. Macroinvertebrate community structure in 2nd-order streams was similar between catchments, but community structure in 1st-order streams differed between catchments. In 2nd-order streams, grazer and predator taxa predominated in both catchments, whereas in 1st-order streams, a clinger taxon predominated in EC and a burrower taxon predominated in CC. Diversity of macroinvertebrates in 1st-order streams was 1.14× higher in EC than in CC. We suggest that effects of deer on macroinvertebrates were less apparent in 2nd- than in 1st-order streams because fine sediments did not accumulate in 2nd-order streams exposed to deer browsing. Our results suggest that effects of sediment addition caused by deer browsing depends on the hydrogeomorphic properties of headwater streams.