Abstract: This paper studied the quantities and some biochemical properties of soil microorganisms in natural forests of different elevations, collectively-owned forests representing varying degrees of anthropogenic disturbance and elevations, forests under different tenures, and soils of different landuse types in eastern slope of Gaoligong Mountatins. At the upper part of the mountain, the quantities and activities of soil microorganisms in natural forests increased with decreasing elevation, but at the lower part, those in collectively-owned forests were decreased with decreasing elevation, due to the increasing intensity and frequency of anthropogenic disturbance. The quantities and activities of soil microorganisms declined as the forest tenure varied from state-run to collective and to individual. After natural forests were replaced by pure plantations, the quantities and activities of soil microorganisms rapidly declined. However, in some cases, soils under cultivation appeared to be favorable to microorganism reproduction. In mid-elevation(about 2000m) natural forest soils, microorganisms were abundant and highly active. High elevation and low temperature was unfavorable to microbial reproduction and biochemical processes. Intensive felling and utilization of forests could also reduce the quantities and activities of soil microorganisms to a lower level.

Key words: Natural forests, Collectively-owned forests, Soil microorganism, Pure forest, Gaoligong Mountains