Nutrient limitations dominate biogeography of microbial carbon use efficiency

Quantifying the biogeographical patterns of soil microbial carbon use efficiency (CUE) is crucial for C model development to accurately predict soil C stocks and the C-climate feedback. Here, we used the extracellular enzyme activities stoichiometry and metagenomic sequencing method to quantify the biogeographical patterns of microbial CUE and identify their drivers across northern China. We found that the values of CUE originating from the cold and humid ecosystem were dramatically greater than that of the warm and dry ecosystem. Soil microbial nitrogen (N) and phosphorus (P) limitation inferred from exoenzymatic stoichiometry and metagenomics, particularly for N limitation involving denitrification-induced N loss, exhibited strong negative effects on CUE. Our biogeographic analysis of soil microbial CUE highlights the importance of soil nutrients limitation to predict soil C sinks in Chinese ecosystem, which has significant implications for future study and policy decisions in different ecosystem management.