Abstract
The effects of differences in substrate characteristics on benthic macroinvertebrate communities were studied in two small catchments with different land usage (agriculture and forestry) in central Hokkaido, northern Japan. Permeable sediment/substrate samplers were installed on streambeds within each catchment from June to November, 1998. The proportion of substrate particle size was clearly different between the catchments. The amount of fine sand (particle size : 0.1-1 mm) that was collected in the agricultural catchment was 50-60 % of the total sediment, while that in the forested catchment was only 30 % of the total. The density of macro invertebrates in the agricultural catchment was only 10-20 % of that in the forested catchment. The results of canonical correspondence analysis showed fine sand was the most important variable in explaining the habitat characteristics in the agricultural catchment. Extensive agricultural land use in this region has induced gully erosion, resulting in a continuous sediment supply to the streambed. Effective stream restoration will require both construction measures for preventing slopes from eroding and the regulation of land use activities.
