Mountain slope evolution controlling the distribution of Fagus crenata in the Kamikochi Valley, central Japan.

Abstract

The effects of geology and landforms on the distribution of Fagus crenata were investigated in a forest ecotone between subalpine and montane forest zones. The distribution of F. crenata trees was mapped by field surveys and aerial-photo interpretation in the Kamikochi Valley in the upriver regions of the Azusa River Basin, central Japan. Most F. crenata trees were found on steep, dissected slopes within areas of late Cretaceous to early Paleocene granitic rocks, and at the margin where Mesozoic sedimentary rocks contacted granitic rocks. The erosion front that has developed on mountain slopes since the Holocene probably controls the upper limits of F. crenata. Landslides on dissected slopes appear to be important for F. crenata to become established in the area of distributional limit. They may improve edaphic and light conditions on the forest floor.