谷頭部の植生構造に及ぼす土壌浸蝕の影響 : 加住北丘陵での検討

抄録

A relationship between forest structure and surface soil erosion was examind in 30 valley heads in the Kasumi-Kita Hills, western part of Tokyo. The forest structure of the valley heads was classified into three types based on the degree of the development of shrub layer: well-developed type, slightly-developed type, and lacking for shrub layer type. Soil erosion activity in the surface of the valley heads was divided into three types : actively-eroded surface, moderately-eroded surface, and non-eroded surface. The distribution of the forest structure types corresponded well with the distribution of soil erosion activity; well-developed type standed on non-eroded surface which occupied the upper part of the valley head, while lacking for shrub layer type appeared on actively-eroded surface which occupied the lower or bottom part of the valley head. Those relationships suggest that the development of the shrub layer is affected by the surface soil erosion; active soil erosion results in lacking for soil materials, and prevents tree seedings from establishment because of lacking for soil materials. From the age sensus of canopy trees, erosion activity in the Kasumi-Kita Hills is supposed to have started dozens of years before.