Abstract
Alpine peatlands on the eastern Tibetan Plateau are vital carbon sinks, with soil moisture playing a key role in peatland carbon cycling. However, they face disruptions in their carbon balance due to drought, which reduces soil water content. Therefore, this study investigated microbially driven water-carbon interactions through field surveys, laboratory incubations, and metagenomics. Soil drying contributes to changes in both the metabolic quotient (qCO(2)) and the microbial quotient (Cmic: Corg), as well as the microbial abundance. As the soil water content decreased, both qCO(2) and Cmic: Corg exhibited an overall increasing trend. Moreover, soil water content had a more significant effect on soil bacteria, while its effect on fungi and archaea was minimal. Soil microbial carbon decomposition genes were also influenced by changes in soil water content. Next, we used RDA to analyze the relationship between soil respiration quotient values and microbial traits. The results revealed that Actinobacteria were strongly negatively correlated with qCO(2), whereas Archaea and Candidatus_R were positively correlated with qCO(2). Additionally, Cmic: Corg was closely linked to fungi, and both Proteobacteria and Acidobacteria exhibited positive correlations. qCO(2) had a strong negative correlation with genes involved in the degradation of monosaccharides and hemicellulose, whereas Cmic: Corg was positively correlated with genes related to the degradation of cellulose and lignin. Moreover, droughts affected microbial residue carbon and associated carbon metabolic pathways. Therefore, changes in soil water content may be an important factor influencing carbon metabolism processes in peatlands. This study deepens our understanding of the effects of drought on soil metabolism and microbial dynamics in alpine peatlands and provides new insights into the microecological mechanisms of soil carbon cycling in these ecosystems in the context of global change.