Dynamics of sub-alpine forest ecosystems as affected by decrease in snowfall under climate change

日本冷杉是日本中部占优势的亚高山乔木。Norikura山林系maresii主枝在冬季受地表以上环境胁迫而退化，而积雪内的枝条则不受任何胁迫的影响。早春时节的高光子通量可能对树线雪面以上白杨叶片的光化学系统造成了伤害。在积雪线以上的嫩枝遭受了冬季干燥和冬季在雪表面上的栓塞。在初夏，由于栓塞，气孔导度仍然很低。栓塞直到新的木质部形成才恢复。冬季干燥会使积雪线上的干物质产量减少，主要产量可能由积雪线下的部分产生。因此，与气候变化相适应的降雪量减少应该对树线白杨有不利影响

Abies mariesii is a dominant sub-alpine tree in the central Japan. Leader stems of tree-line A. mariesii at Mt. Norikura degenerate due to environmental 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 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 in accordance with climate change should have an unfavorable effects on tree-line A. mariesii