秩父山地金峰山における周氷河性岩塊斜面と森林限界の関係について

抄録

The forest limit is defined in this paper as a line which divides such scrubs as Pinus pumila from subalpine coniferous forests. Usually, control factors which determine the position of forest limits are temperature, wind, snow depth, slope form, and soil condition, and so forth. In this paper, effects of slope deposit and soil condition of the forest limit were discussed.
Mt. Kinpu-san (2, 595 m; 35°52'N) in Central Japan consists of granitic rocks. The forest limit on the slopes around summit ranges from 2, 280 to 2.570 m in altitude. It was found the periglacial block slope formed during the late stage of the Last Glacial age at higher than 2, 280 m in altitude around the summit. The surface of this slope is composed almost entirely of matrix-free blocks (0.5 to 6.0 m in diameter) covered with thin soil. The site condition on such slopes has halted forest from developing but to support the scrub. On the other hand, the periglacial block slope of the early Last Glacial age was distributed in lower altitudes than the younger one. Subalpine coniferous forests was developed on this older slope covered with thick soil. The forest limit is situated below the small cliff formed at the terminal of the younger periglacial block slope. From these facts we conclude that the local forest limit in this area is forced to be located in the margin of younger periglacial block slopes.