Identifying the drivers of soil organic carbon (SOC) accumulation is essential to understanding C cycling in terrestrial ecosystems. More evidence has indicated that soil microorganisms are central in regulating SOC, yet what mechanisms and how they play are not clear. Here, we conducted a survey of soils across 16 locations along a ~ 4000 km forest transect in eastern China, spanning a wide range of climates, soil conditions, and microbial communities, and explored the effects of biotic and abiotic factors on SOC. Soil microbial carbon use efficiency and turnover were estimated by using 18O-water incubation method; microbial necromass was analyzed by using amino sugars.
Results/Conclusions
We discovered microbial biomass factors (i.e. microbial biomass, turnover time and carbon use efficiency) and microbial necromass are the most important factors on variances of SOC. The balance between microbial necromass and soil C decomposition directly determined the changes of SOC, while climate, soil properties, and C inputs processes had the indirect effects. Our results provide solid evidence that microbial anabolism and their necromass play a critical role in regulating SOC, with important implications for the improvement of C cycling models under global change scenarios.