Global Warming Has Imbalance Impact on Soil Nitrogen Transformation Rates

Global warming is projected to significantly influence soil nitrogen (N) transformations, yet a comprehensive understanding of the spatial distribution of these effects and the underlying driving factors at a large scale remains limited. This study employs a Random Forest model to develop nonlinear temperature sensitivity (Q₁₀) models for soil nitrogen mineralization (N_min), nitrification (N_nit), and denitrification (N_de) based on a data set comprising 1,131 records from across China. Our results revealed variations in Q₁₀ values across different N transformation processes and ecosystem types, with an average of 1.96 for N_min, 1.90 for N_nit, and 2.19 for N_de. Higher Q₁₀ values (>2) for N transformation rates were observed in the Northern and Western China, which exhibited a geographical spatial pattern that changed with longitude, latitude, and altitude. Soil substrate availability, N input, soil pH and climatic variables accounted for most of the variation in Q₁₀ among diverse ecosystem types and regions on a large scale. In projected future warming scenarios, it is expected that N transformation rates could increase by between 0.001 and 1.87 times under SSP2-4.5 and SSP5-8.5 from 2040 to 2100, compared to 2030. These findings deepen our understanding of the large-scale spatial variations and controlling factors of N transformation rates in response to global warming, providing a robust foundation for more informed ecosystem management and environmental policy decisions.