Nitrogen Addition Regulates the Temperature Sensitivity of Soil Carbon Release via Microbial Properties

ABSTRACT The temperature sensitivity (Q 10 ) of soil carbon (C) release is a key parameter for evaluating soil C stability under climate warming, with particular importance in high‐latitude regions that are highly vulnerable to rising temperatures. Nevertheless, the mechanisms by which nitrogen (N) addition modulates the temperature sensitivity of soil C release remain insufficiently understood. Here, we collected soils from a long‐term N addition experiment in a high‐latitude boreal forest and conducted controlled incubations to assess how N addition influences soil CO 2 release and its temperature sensitivity. We found that N addition significantly suppressed soil CO 2 release across all incubation temperatures (5°C, 15°C, and 25°C), yet its effects on Q 10 were nonlinear. Specifically, N addition enhanced Q 10 between 5°C and 15°C but suppressed Q 10 between 15°C and 25°C. Both CO 2 release and Q 10 were strongly associated with bacterial and fungal diversity and biomass, as well as with the activities of key C‐ and N‐cycling enzymes (e.g., β‐glucosidase, cellobiohydrolase, and N‐acetyl‐glucosaminidase). However, the effects of N addition on CO 2 release and Q 10 were primarily mediated through both direct and indirect influences on microbial properties. Together, these findings demonstrate that N addition regulates soil CO 2 release and Q 10 mainly through microbial pathways, underscoring the pivotal role of microbial processes in determining high‐latitude carbon dynamics and their feedbacks to climate change.