Abstract
The purpose of this study was to clarify the effect of soil factors on the decline of Clyptomeria japonica in Kanto plains. Soil features, such as parent material, types of deposition, soil texture, bulk density(soil depth: 0-8, 8-16 cm), porosity and hardness of surface soil were investigated in 34 study sites, where the decline index previously reported. The index performed damaged at lowland sites with sandy alluvial soil, although healthy at upland or hill sites with clayey or loamy soils derived from volcanic ash or weathering products of sedimentary rock. These results showed locations and parent materials affected to the tree decline. Furthermore, the remarkable correlation was observed between bulk density and the decline index. Thus, compact surface soil was correlated with the decline, however, thick soil layer eases the influence of compact surface soil. Most of sites were located in the grounds of temples and shrines. Extremely compact surface soil often occurred by treading, and trees were damaged. The forest decline was effected by soil factors relating to density and was accelerated by artificial impacts.
