Abstract
At Cape Shiretoko, problems of a decrease in Sasa owing to the higher density of sika deer (C. nippon yesoensis H.) is becoming serious. Also, marked decreases in specific kinds of trees, in seedings of trees and in shore plant communities containing the endangered species occur by their browsing or bark stripping. In addition, problem of soil erosion becomes also serious. Therefore, density manipulation of wintering sika deer herd was carried out in 2007, and it required us to develop the vegetation indexes that can evaluate the effect of human interventions or that can be indicating the start or the end of interventions. In this study, we investigated the biomass of Poaceae, the size structure of C. vurgare and the coverage and height of S. cannabifolius at the inside and outside of the fences. We also investigated the biomass of Poaceae, S. senanensis at Cape Shiretoko, and the leaves of forest vegetation around Cape Shiretoko grassland. As the results, after the density manipulation started, the biomass of Poaceae showed increasing, C. vulgare decreased promptly, coverage of S. senanensis showed increasing. We concluded that these could be the indexes in short term, and that height of S. senanensis could be used as the index in middle or long term because it showed a poor growth after the density manipulation started. Furthermore, this study also indicated that the biomass of leaves at every height of trees can be the indexes for long or short term, since biomass of leaves increased differently corresponding to each height.
