Formation Mechanisms of Community Boundaries in Subalpine Coniferous Forests

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This study was carried out to examine the formation and dynamics of the mosaic landscape of forest stand types with clear boundaries in subalpine forests of Hokkaido, northern Japan.Main research site was set on the western slope of Mount On'nebetsu of Shiretoko Peninsula, eastern Hokkaido. The mosaic landscape made by pure stands of Picea glehnii, and mixed stands of Abies sachalinensis, P. glehnii and Betula ermanii was described. Detailed census of core of, and margin between these two stand types showed that the discontinuous stand boundaries were not related to the edaphic conditions that changed gradually along the boundaries. Dynamic sequence around boundaries was from Picea -pure stands to mixed stands. The replacement process was hypothesized to be related to species difference in tolerance against aggravation by snow deposit on crown together with wind. Another site investigated was a successional landscape on the slope of Mount Komagatake in southern Hokkaido. The dynamic pattern of the invasion of Larix kampferi was analysed using sequential aerial photographs.As a generalized modelling tool, a new simulator was proposed through this study. The model is based on the geographically extended model of stand-level tree size structure (Kohyama and Shigesada 1995) and on the shifting patch mosaic model of stands with tree size structure in gap-dynamic landscape of forest (Kohyama 1993). The response of latitudinal forest zonation was re-examined using the new simulator. Compared to the case without patch mosaic (I.e. Kohyama and Shigesada), the forest boundaries made by competitive interaction was predicted to move slightly faster, while still millennia time lag was the case after centennial global warming.