Abstract
Studies were carried out to examine the mineral cycling of forests which have developed on steep slopes and which have the varying environmental or site conditions. Twenty sample plots of a deciduous broad-leaved natural forest were selected along slopes. Site conditions differed in each plot. It was necessary to evaluate the site condition of the plot to compare the rate of cycling among plots. The moisture index was adopted as the index of site condition. In the present paper, the validity of moisture index as a means of evaluation of site condition is examined. The index estimate is based on the floristic composition of trees and their number, and ranged from 0 to 300, as the floristic compo-sition changed from mesic to xeric. Though there was a general tendency for the moisture index to become greater with upward slope, the gradient of moisture index was different for each slope and for each part of the slope. Coefficient of exposure, mean tree height, moisture content of A0 layer and top soil, rate of decomposition of cotton cloth, and amount of dry matter of A0 layer were measured for each plot. Changes of the above mentioned factors along the slopes corresponded with change of moisture index, and there were fixed relationships among them regardless of difference of slope. In the area studied, the distri-bution of tree species along slope had been determined as result of the study on vegetation, so that the estimation of moisture index was not laborious. As far as the matured broad-leaved natural forest is concerned, moisture index can be taken as an index to compare the site or environmental conditions along slopes.
