Bioclimate and arbuscular mycorrhizal fungi regulate continental biogeographic variations in effect of nitrogen deposition on the temperature sensitivity of soil organic carbon decomposition

Abstract The temperature sensitivity ( Q 10 ) of soil organic carbon (SOC) decomposition is an important parameter for those seeking accurate projections of SOC dynamics and its feedback on climate change in terrestrial ecosystems. However, how Q 10 responds to N deposition across environmental gradients and the underlying mechanism remain largely unresolved. We conducted a novel incubation experiment with periodically varying temperature based on the of soil origin sites to elucidate the responses of Q 10 to N addition across China. Our results demonstrated that N addition effects (NAEs) on Q 10 were negatively related to latitude and were strongly site dependent. Bioclimatic, edaphic, and microbial variables together explained 50.1% of the total variation in NAEs on Q 10 , but bioclimate (16.0%) had the greater explanation than edaphic (11.8%) and microbial properties (6.3%). The response of soil exchangeable Ca 2+ to N addition was a predictive power for NAEs on Q 10 , contributing 7.2% relative importance in regulating this variation. Furthermore, arbuscular mycorrhizal fungi indicated by Glomeromycota were the best microbial predictor and contributed 10.9% relative importance in the variation regulating NAEs on Q 10 . Overall, our results suggest that increasing N addition will increase the sensitivity of SOC decomposition to global warming and highlight the importance of bioclimate, exchangeable Ca 2+ , and arbuscular mycorrhizal fungi in predicting the response of Q 10 to N deposition in natural terrestrial ecosystems. The biogeographic variation in response of Q 10 to N deposition should be considered in carbon‐climate models to decrease the prediction uncertainties of SOC dynamics and its feedback to global warming.