Seasonal changes of microbial biomass carbon related to climatic factors in soils from karst areas of southwest China

 The seasonal responses of soil microbial biomass C to changes in atmospheric temperature, soil moisture and soluble organic C were studied in soils from the karst areas of southwest China. These soils are relatively weathered, leached and impoverished, and have a low input of plant residues. Over 1 year, an inverse relationship between soil microbial biomass C and atmospheric temperature was found. The highest microbial biomass C occurred in winter and the lowest in summer, and ranged from 231–723 μg g^–1 dry soil. Although there was no obvious relationship between microbial biomass C and soil moisture, a negative correlation existed between microbial biomass C and soluble organic C. In the ecosystem studied, the marked changes in soil microbial biomass C at above 20  °C were ascribed to fluctuations of soil moisture, which were controlled by climatic factors and geomorphic conditions. The patterns of soluble organic C turnover were similar to those of soluble carbohydrate C, both of which were controlled by soil drying-rewetting cycles. It was concluded that the lowest amounts of soil microbial biomass C, measured in the summer, resulted in increases in soluble organic C due to higher turnover rates of the former at warmer air temperatures. Thus, there was a marked seasonal change in soil microbial biomass C. Received: 1 November 1998