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 (Q10) 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 Q10 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 Q10 to N addition across China. Our results demonstrated that N addition effects (NAEs) on Q10 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 Q10, but bioclimate (16.0%) had the greater explanation than edaphic (11.8%) and microbial properties (6.3%). The response of soil exchangeable Ca2+ to N addition was a predictive power for NAEs on Q10, 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 Q10. 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 Ca2+, and arbuscular mycorrhizal fungi in predicting the response of Q10 to N deposition in natural terrestrial ecosystems. The biogeographic variation in response of Q10 to N deposition should be considered in carbon‐climate models to decrease the prediction uncertainties of SOC dynamics and its feedback to global warming.