Soil heterotrophic respiration and active carbon pools under subtropical forests in China

An understanding of the heterotrophic respiration part of belowground processes, as affected by active carbon, is crucial in order to predict the response of carbon emission from soil organic carbon, in forest ecosystems and climatic changes. However, in the current literature, most soil respiration measurements are interpreted without simultaneous information on active carbon pool dynamics. In this study, path analysis was used to demonstrate the impacts of microbial biomass carbon, water-soluble organic carbon and mineralisation carbon on soil heterotrophic respiration. It was found that variations in heterotrophic respiration were well related to mineralisation carbon and microbial biomass carbon, whereas water-soluble organic carbon was generally not adequate indicators of carbon effluxes. Mineralisation carbon and microbial biomass carbon have significant correlation relationships and indirect effects with each other on heterotrophic respiration, indicating a possible stimulatory effect of labile carbon and microbial activity on microbial processing of carbon. A single parameter recommended to quantify soil heterotrophic respiration in southern China is mineralisation carbon, as the most efficient measurement of soil variable.