Abstract
The undisturved forest soil samples, 15.5cm in diameter and 10cm in height, were collected on the slopes where the andosol covered pyroclastic rocks, and their saturated coefficients of permeability in vertical (Kv) and horizontal (Kh) direction were measured, then the pore characteristics were analyzed. As the result, the anisotropy in permeability, mostly Kh > Kv, was confirmed. Layer poorer in macro pores had stronger anisotropy. In the topsoil of andosol and the clayey subsoil, the strength of the anisotropy depended on the quantitative relation between the pores of pF1.5 to 2.0 and the coarser macro pores. It was found that the anisotropy is affected by the orientation structure in the clayey subsoil and also the root system of undergrowth, Sasa Palmata Marliac Nakai, in the andosol topsoiol.
