Warming enhances soil microbial respiration through divergent mechanisms in a tropical forest and a temperate forest

• In-situ warming boosts soil microbial respiration without thermal adaptation in a tropical forest and a temperate forest. • Warming increases soil microbial respiration in temperate forest without altering microbial diversity or temperature sensitivity. • Warming boosts soil microbial respiration and temperature sensitivity in tropical forest by altering microbial diversity. Carbon dioxide (CO 2 ) emissions resulting from soil microbial respiration constitute a significant component of the global carbon cycle. However, the impact of climate warming on these emissions remains inconclusive, as it is uncertain whether microorganisms increase CO 2 emissions from soils to the atmosphere by increasing their respiration or mitigate them through thermal adaptation. Here, we conducted both in-situ warming experiments and laboratory-controlled assays to investigate whether microbial respiration exhibits thermal adaptation in a temperate forest soil and a tropical forest soil. We also examined the mechanisms of microbial thermal adaptation by analyzing changes in microbial respiratory temperature sensitivity (Q 10 ) and community structure (via amplicon sequencing). Our findings indicate that no thermal adaptation occurs and that in-situ warming enhances microbial respiration in both temperate and tropical forest soil samples, regardless of glucose addition. In the temperate forest soil, warming increased microbial respiration without significantly affecting respiratory Q 10 and diversity. Conversely, in the tropical forest soil, warming increased microbial respiration by significantly increasing respiratory Q 10 (by 8.13% with excess glucose and by 10.93% without excess glucose) and shifting diversity, including decreased richness and reduced Shannon diversity. The divergent responses of tropical and temperate forest soil microbes to warming may be attributed to temperature differences, leading to distinct microbial strategies for coping with temperature changes. Although limited to two sites and requiring further validation, our findings carrying significant implications for gaining insights into how soil microorganisms globally react to climate warming and for making future predictions about the intricate feedback mechanisms between the carbon cycle and climate.