Abstract
In order to provide a standard for predicting erodibility in Japanese cypress stands by using the quantification theory, availability of several features of the ground surface as indices of the intensity of soil erosion was examined. In a Japanese cypress plantation with patches of undergrowth of two species of fern, four study plots of 10 m square were set up; plots KT and UT being covered with Dicranopteris linearis and Gleichenia japonica, respectively, plots KC and UC having almost no undergrowth. In each plot, the amount of soil moving down the slope was mesured by using ten trap boxes and the undergrowth coverage and ground surface features such as number of "soil poles, " length and height of "soil cliffs, " and fine roots exposure were observed in five quadrats of 50 cm square. The order of soil erosion intensity expected from the undergrowth coverage was KT<UT«KC<UC. The order indicated by the ground surface features mentioned above was KT<UT«KC<UC. The order of the amount of the trapped soil was KT<UT«UC<KC. The effectiveness of the ground surface features as indices of soil erosion intensity was concluded from the good coincidence among the three orders. A single discrepancy was the reversal of KC and UC in the order of the amount of the trapped soil compared to the other orders. A comparison of several physical properties of the surface soil between UC and KC revealed that the amount of loose and easily erodible soil material was less in UC than in KC, which was considered to cause the discrepancy.
