关键词: 热适应, 增温强度, 土壤氮素有效性, 碳代谢功能基因, 碳-气候反馈

Abstract: Microbial thermal adaptation plays a crucial regulatory role in the soil carbon (C) cycle, with stronger adaptation weakening the positive feedback between climate warming and soil CO₂ release. Previous studies have primarily focused on single-level warming experiments; however, climate change effect occurs incrementally with variable rates, and their regulatory effects on soil microbial thermal adaptation remains poorly understood. Here, we investigate microbial respiratory thermal adaptation across a warming gradient based on a 4-year multi-level warming experiment in a subtropical forest. Our results show that microbial thermal adaptation is positively correlated with warming intensity. Moreover, this relationship is mediated by soil nitrogen availability and microbial C-cycling functional gene diversity. Our findings highlight the need to incorporate progressively enhanced microbial thermal adaptation strategies into next- generation C cycle models to refine predictions of C-climate feedback.

Key words: Thermal adaptation, Carbon cycling, Climate warming, Microbial community, Carbon-climate feedback, Functional gene diversity