1989 Volume 39 Issue 2 Pages 127-137
The alpine zone of Mt. Yakushidake (2926 m) is dominated by block fields covered with only sparse lichen and moss, with little development of ordinary alpine plant communities. To clarify the cause of this sparse vegetation, the lithology and slope development of this area were examined. In quartz-porphyry areas, large quantities of coarse blocks were deposited during the late Glacial Age to form extensive periglacial block fields. However, plant colonization during the post glacial age was severely limited by the lack of a matrix in the slope deposits. Although Pinus pumila scrub has invaded the lower slopes, the middle and upper slopes consist of block fields with only a sparse cover of lichen or moss. In dacite areas, active debris movement during the Neoglaciation age resulted in the formation of wide debris fields. In such areas, vegetation was absent due to the relatively recent slope formation and consequent delay in plant invasion. A portion of the dacite and granite area gave rise to fresh debris which formed gravel fields covered with two types of plant community. Muddy unstable gravel fields became dominated by the Viola crassa community, whereas on the stable sites, wind-blown heath developed. However, on the middle and upper slopes of this mountain the severe restructions imposed on plant growth have resulted in a unieque alpine landscape dominated by lichens and mosses.
