Effect of freeze-thaw cycle on carbon fixation by soil microbes

The freeze-thaw cycle (FTC) is a common periodic process of soil change in middle and high latitudes and high altitudes. FTC can affect microbial functional genes, plant carbon input patterns and physicochemical protection mechanisms of soil organic carbon. FTC significantly affected soil carbon cycle and microbial carbon sequestration by changing soil porosity, temperature, water content and aggregate structure. However, current research lacks sufficient discussion on the long-term effects of FTC the functional mechanisms of microbial communities and soil carbon components, and the coupled effects of multiple environmental factors. This paper introduces the efficiency of the microbial carbon pump (MCP) and its related microbial indicators as key parameters into the analytical framework of the carbon cycle model. The review encompasses the following aspects: (1) the mechanisms of carbon fixation by soil microorganism; (2) response and changes in the composition and activity of soil microbial communities under freeze-thaw cyclic stress; (3) the influence of FTC on the carbon cycle under different soil depth conditions; (4) how FTC jointly affect soil carbon dynamics by regulating microbial carbon sequestration-related functional genes (involved in substrate utilization preference and carbon use efficiency) and their interactions with plant organic carbon input patterns. This review systematically integrates research findings on the effects of FTC on soil carbon pools and microbial carbon sequestration, clarifies core mechanisms and research gaps, and provides key support for theoretical refinement, ecological conservation, and carbon sink management in related fields, promoting interdisciplinary research integration. • Introduces ΔMCP efficiency to dynamically assess microbial carbon sequestration potential under freeze-thaw cycles. • Freeze-thaw cycles alter soil carbon dynamics by modifying microbial community structure and metabolic functions. • Archaea contribute to carbon fixation via methanogenesis/oxidation pathways under FTC stress. • Biochar amendment enhances soil carbon stability and microbial resilience to freeze-thaw perturbations. • Multiscale integration of microbial processes is crucial for predicting soil carbon responses to climate change.