Abstract
In order to assess the changes of various structures in a permanent pasture ecosystem due to cessation of grazing, studies were carried out from 1976 to 1979 in the pasture dominated by orchardgrass, extending on southern slope of Mt. Asama in Nagano prefecture. This report deals with the changes of soil physical conditions of the following three experimental plots ; Control plot: managed by rotational grazing ; Ca-exclosure plot: prohibited grazing from 1976 to 1979, with CaCO_3 (2 ton/ha) application at the beginning of excluding; Exclosure plot: with no CaCO_3 application. The experimental results obtained were as follows: 1. Three phase distribution of 0-15cm soil layer in control plot was almost unchanged throughout 4 years. In both exclosure plots, however, solid and liquid-phase of the soil decreased and gaseous-phase increased, especially evident in the upper soil layer. 2. The soil hardness in control plot increased with the increment of trampling pressure and was always harder than that in both exclosure plots, where the soil hardness decreased markedly in the upper soil layer. 3. The percentage of water-stable soil aggregates larger than 1mm diameter decreased with increment of soil depth in control plot, but in both exclosure plots the percentage reversely increased. 4. These changes of soil physical conditions caused by cessation of grazing were accelerated by applying CaCO_3.
