Abstract
Recently, deer overbrowsing dramatically decreases understory vegetation in forested areas. Also, the deer impact leads riparian vegetation, which originally covers above headwater streams in summer, to be devastated. Riparian vegetation acts important roles linking forest and stream ecosystems by controlling soil erosion, and by providing terrestrial invertebrates to stream as food resources for fishes. Soil erosion activation would induce expansion of fine sedimentation on streambed, and subsequent decrease in diversity of benthic invertebrates in aspect of inorganic materials. Meanwhile, in aspect of organic materials, soil erosion activation would also increase an input of allochthonous organic matter derived from forests that cause changes in nutrient cycling within stream ecosystem. The former impact would be heterogeneously occurred in streams because distribution of fine sediment depends on stream power determined by fluvial geomorphology. Thus for detecting impacts of sediment runoff caused by deer overbrowsing on stream ecosystem, approaches with the view from hydrology and fluvial geomorphology coupling with ecology would be important. On the other hand, changes in quantity and quality of terrestrial invertebrates provided from riparian forest to stream might influ-ence stream fishes and their original ecosystem through biological chain in forest-stream ecosystem.
