Freeze-thaw processes regulate microbial controls on soil organic carbon decomposition in Qingzang alpine grasslands

Freeze-thaw cycling can influence microbial physiological states including microbial dormancy and resuscitation, and enzyme activities. These factors are essential to the mechanisms that control soil carbon and nutrition dynamics mediated by microbes. Warming-induced thawing may also cause changes in microbial functional diversity and stability. However, it remains a significant challenge to integrate these responses within microbial ecological models, which impedes the precision of carbon-nutrient-climate feedback projections. Here, we depict the dynamics of freezing and thawing soil, as well as the microbial and enzymatic functions in response to freeze-thaw processes within the Microbial-ENzyme Decomposition (MEND) model. The simulation was conducted in the Qingzang alpine grassland with field observations and comprehensive parameterization. Our findings suggest that microbial data potentially enhance confidence in model simulations. We also demonstrate that the relative substrate availability affects the trade-off between enzyme synthesis and metabolic flux. The results can deepen our understanding of microbial acclimation to freeze-thaw cycling and how they respond to soil organic carbon decomposition in permafrost ecosystems.