Abstract
The amount of soil loss was measured for one year at 21 stands of Hinoki(Chamaecyparis obtusa) plantations (19-42 years old) in the northern part of Okayama prefecture. Mean annual soil loss in tending and untending stands were 2.22t/ha/yr (0.80-5.78t/ha/yr), 6.35t/ha/yr (0.31-23.08t/ha/yr) respectively. Mean annual soil loss in untending stands was three times larger than that in tending stands. Annual soil loss could be well estimated by multiple regression model using three factors; slope angle, stand density, and coverage of understories. The model predicted that soil loss increased when slope angle was larger than 35° even if stand density was 500 trees/ha. In such steep slopes, it is necessary to take measures for soil erosion control.
