Effects of drought on the thermal adaptation of soil microbial respiration: A review

Drought induced by global climate change affects the thermal adaptation of soil microbial respiration, which has complex consequences on the carbon (C) cycle. Drought can either enhance C emissions and create a positive feedback loop, or promote C sequestration and generate a negative feedback effect. We reviewed the effects of drought on microbial thermal adaptation, analyzed the underlying mechanisms, and summarized current research findings and related debates. Drought significantly influences microbial thermal adaptation through altering soil aggregate structure, organic carbon molecular composition, and microbial community structure. Due to variations in climatic zones, ecosystem types, and soil conditions, the impacts of drought on microbial thermal adaptation exhibit regional variety and complexity. Future research should focus on experimental designs that simulate natural environments, utilizing diverse organic substrates (e.g., cellulose, oxalic acid and xylan) to generate more accurate data and explore the synergistic effects of drought with other environmental factors (e.g., elevated CO₂ concentrations, increased ultraviolet radiation, and nitrogen deposition) to reveal their combined impacts on microbial thermal adaptation. Advanced techniques like metagenomics and DNA-stable isotope probing should be warranted to further reveal the microbial mechanisms involved in the regulation of drought on microbial thermal adaptation.