Effects of anthropogenic disturbance on soil microbial biomass C, N and P in a tropical rainforest ecosystem of Assam, northeast India

The effect of anthropogenic disturbance on soil microbial biomass C, N and P dynamics in a tropical rainforest ecosystem of Northeast India was studied in undisturbed, moderately disturbed and highly disturbed stands. Tree species richness in the community was drastically reduced due to disturbance, from 82 species in the undisturbed stand to 13 species in the highly disturbed stand. Soil organic C, total Kjeldahl nitrogen and P concentration was low in the disturbed stands compared to the undisturbed stand. With the increase in disturbance, the microbial-biomass C, N and P decreased significantly (P>0.001) because of lower inputs of organic matter to the soil. Microbial biomass C, N and P ranged between 226-1060,u g g-\u27, 27-92,ug and 13-32 pig , respectively, in the undisturbed and highly disturbed stands. The seasonal pattern of microbial biomass C, N and P was influenced by the variation of soil moisture and temperature, with maximum during winter and minimum during the rainy season. There were significant positive relationships among microbial biomass C, N and P and SOC. TKN and P concentration. Destruction of above ground vegetation by selective logging and clear felling caused a significant reduction in microbial biomass in the disturbed stands