Effects of decreasing snow accumulation under global change on forest ecosystems in central Japan

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Abies mariesii is a dominant sub-alpine tree in central Japan. Leader stems of tree-line A.mariesii at Mt.Norikura degenerate due to environmetal stresses above the snow surface during winters, whereas shoots within snowpack were not affected by any stresses. High photon flux density in the early spring might have injured photochemical systems of A.mariesii leaves above the snow surface at the tree-line. Shoots above the snowpack line suffered from winter desiccation and embolism during the winter over the snow surface. In early summer, stomatal conductance remained low due to embolism. Embolism did not recover until new xylem formation. Winter desiccation should decrease dry matter production over the snowpack line and the main production might be made by the part below snowpack line. Thus, decrease in snowfall under climate change should have an unfavorable effect on tree-line A.mariesii. Similarly, climate change might have an unfavorable effect on the regenerate process of dominant tree species, Fagus crenata in cool temperate forest. Seedlings of F.crenata could not survive in the snow-free winter due to embolism in xylem.