Abstract
A series of field experiments was undertaken to assess changes in some structure of a pasture ecosystem due to cessation of grazing. This report deals with the changes of the form and function of orchardgrass root system in following three experimental plots ; Control plot: managed by rotational grazing ; Ca-exclosure plot: prohibited grazing from 1976 to 1979, with CaCO_3 (2ton/ha) application at the beginning of excluding; Exclosure plot: with no CaCO_3 application. The experimental results obtained were as follows: 1. The root weight per unit area of the orchardgrass pasture was increased by cessation of grazing. 2. About 70% of roots in control plot were concentrated in the top 5cm soil layer. In both exclosure plots, however, percentage of roots in the top 5cm soil layer decreased and the root pattern was deeper than that in control plot, especially evident in Ca-exclosure plot. 3. The rate of root respiration of orchardgrass in control plot was 200〜300 CO_2mg/m^2. hr from 1977 to 1979. In both exclosure plots, the rate increased with increasing root weight untill the third year of excluding (1978), however it decreased in the fourth year (1979) despite of increasing root weight. From the above results, the role of root pattern is discussed in relation to productivity and stability of permanent pasture.
