Stronger microbial respiratory thermal adaptation under higher warming levels

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.