Many of tropical rain forests have suffered from degradation caused by intense logging. Logging is well known to cause degradation in above-vegetation, but may also affect soil biogeochemical processes and soil microbial activities. This study aimed at exploring the changes of soil microbial biomass and extracellular enzyme activities in a forest-degradation trajectory in Deramakot and Tangkulap Forest Reserves, Sabah, Borneo, where various degradation stages of logged-over forests occur.
　　Thirty-five soil samples were collected and soil physiochemical properties were analyzed. In addition, microbial biomass carbon and nitrogen were determined by chloroform fumigation. The activities of acid phosphatase (ACP) were determined with pNPP as substrate. Those of leucine aminopeptidase (LAP), β-glucosidase (BG) and N-acetyl-glucosaminidase (NAG) were detected by a high throughput fluorescent measurement.
　　The results showed that soil microbial biomass carbon and nitrogen decreased with the aggravation of forest degradation (i.e., degradation trajectory). The activities of the four extracellular enzymes were also decreased in the trajectory. Soil microbial biomass carbon had a significant positive correlation with BG and LAP. We suggest that increasing forest degradation causes the reduction of microbial biomass, which in turn decreases microbial enzymatic activities.