Soil extracellular enzymes as drivers of soil carbon storage under nitrogen addition

Enhanced anthropogenic nitrogen (N) inputs to ecosystems may have substantial impacts on soil organic carbon (SOC) cycling. One way to link species-rich soil microorganisms with specific SOC cycling processes is via soil extracellular enzyme activities (EEAs). Here, by presenting a meta-analysis on the response of soil C-degrading EEAs to N addition, our results show that N addition increases hydrolytic C-degrading EEAs that target simple polysaccharides by 12.8%, but decreases oxidative C-degrading EEAs that degrade complex phenolic macromolecules by 11.9%. The net effect of N addition on SOC storage is determined by the balance between the two types of C-degrading EEAs, with impacts varying across different ecosystem types. Our results help identify changes in soil microbial C use strategies under N addition. Incorporating this enzymatic influence into Earth system models could improve the representation of microbial processes as well as predictions of SOC dynamics in a changing environment.