Abstract
Alpine ecosystems store vast amounts of soil organic carbon but are highly sensitive to climate change. Despite this, the response of in situ soil microbial metabolic processes, especially carbon substrate utilization, to climatic shifts remains underexplored. Here, we assessed microbial activity by metatranscriptomics in a Tibetan alpine grassland after a decade of experimental warming (+2°C) and altered precipitation (+50% and -50% of ambient precipitation). The experiment revealed that altered precipitation, rather than warming, shaped the active microbial community. Altered precipitation and warming had significant interactions: warming combined with increased precipitation generally suppressed microbial carbohydrate metabolism and methane oxidation, while warming with decreased precipitation enhanced these processes. Notably, increased precipitation induced a shift in microbial communities towards acid metabolism over sugar metabolism, predominantly driven by taxa such as Betaproteobacteria. This metabolic shift corresponded with an increased emission ratio of methane (CH(4)) to carbon dioxide (CO(2)), a change primarily driven by CH(4), underscoring the critical role of microbial carbon metabolic preferences in regulating greenhouse gas emissions. Our findings highlight the necessity of integrating microbial carbon metabolic preferences and their interactions with climatic factors into models to accurately predict carbon-climate feedbacks.IMPORTANCEMicrobes have specific preferences for different carbon substrates, but their responses to climate change remain unclear. Our study, conducted through a long-term climate manipulation experiment in a Tibetan alpine grassland, reveals that increased precipitation leads soil microbial communities to favor acid metabolism over sugar metabolism. This shift significantly affects greenhouse gas emissions by increasing the CH(4)/CO(2) ratio, which has important implications for global warming. These findings are crucial for accurately forecasting carbon-climate feedbacks and managing alpine ecosystems as climate change progresses.