Deer browsing extremely decreases understory plants. Since these plants protect soil, denudation by deer causes soil erosion via overland flow. Eroded soil inflow to streams may affect macroinvertebrate communities (MC) by altering substrate composition.

We compared hydrological environments and MC in 1st and 2nd order streams between a deer-excluded catchment (EC) and a control catchment (CC) after 4 years of deer exclusion.

Inflow of overland flow to stream was greater in CC than EC, and substrate in 1st order streams in CC was finer than those in EC, whereas that in 2nd order streams was similar between them. These results suggest that deer exclusion has restored heterogeneity of substrate in 1st, but not yet in 2nd order streams.

Differences in MC between EC and CC were observed in 1st order streams. The MC in 2nd order streams was dominated by grazer and predator taxa, whereas that in 1st order streams was dominated by a clinger taxon in EC and burrower taxa in CC. The diversity was higher in EC than in CC in 1st order streams. These results suggest that deer exclusion has restored gravelly substrate and diverse MC in 1st, but not yet in 2nd order streams.

Given that sedimentation in streams from headwaters is obvious, further downstream monitoring is needed.