The increase of microbial diversity enhances the compensatory thermal adaptation of soil microbial respiration

Abstract

Accurately predicting the feedback mechanisms of soil carbon (C) pool in response to warming hinges on our understanding of the thermal response of microbial respiration. However, how the thermal response of microbial respiration varies along climate gradients has not been systematically evaluated. In this study, using soils from natural forests along a 3800 km transect across China, we assayed microbial respiration response to temperature curves under 10 measurement temperatures for all samples after 6 months of incubation at two different temperatures (10 and 30 °C). Meanwhile, based on the macromolecular rate theory, we quantified thermal traits (T_opt (temperature optimum) and T_inf (inflection point)) and the thermal response of microbial respiration across a latitudinal-scale forest transect. Our findings reveal a shift in microbial respiration response to temperature curves towards higher incubation temperatures, accompanied by increases in both T_opt and T_inf, indicating a compensatory thermal adaptation of microbial respiration (CTA). The magnitude of CTA (the response ratio of thermal traits under incubation temperatures) exhibited a U-shaped relationship with mean annual temperature (MAT) along the transect and was associated with shifts in microbial biomass, bacterial richness, bacterial and fungal dominant community. Further analysis revealed that bacterial richness explained the maximum variation of CTA. For microbial properties, bacteria richness did not change significantly with MAT, while fungi richness increased linearly with increasing MAT. Our findings emphasize the consistent compensatory thermal adaptation of microbial respiration in forest soils and the critical link between microbial communities and thermal adaptation, with implications for better characterizing soil climate-C feedback under warming.