Soil bacteria mediate organic carbon stability during alpine wetland biogeomorphic succession in the arid region of Central Asia

Aims Soil organic carbon (SOC) stability greatly affects soil carbon sequestration capacity and carbon emissions, is related to soil bacterial communities, but it remains unclear whether such relationships exist in alpine wetland biogeomorphic succession. Methods Here, we used a space-for-time approach across hydrological gradients, and alpine wetland succession can be divided into three types: “Swamp” (S), “Swamp Meadow” (SM), and “Meadow” (M) to examine the dynamics change of SOC fractions and bacterial communities. Results The succession from S-SM-M resulted in decreased SOC stability (SM and M decreased by 18.65% and 31.88% compared to S). Furthermore, the decrease in SOC stability was primarily due to the decrease in soil moisture during succession and moisture-induced changes in bacterial community structure. e.g., the relative abundance of Proteobacteria decreased significantly by 40.99% and 52.87% in SM and M, while the relative abundance of Acidobacteria increased by 43.49% and 185.04% in SM and M compared to S. Co-occurrence network and random forest analyses further identified that changes in keystone taxa of bacteria, including Deltaproteobacteria, Acidimicrobiia, Bacteroidia and Gammaproteobacteria, were associated with SOC stability. Conclusions In conclusion, bacteria shifted their community composition to reduce SOC stability in response to soil moisture variations during succession, and underscores the importance of identifying keystone taxa that are crucial for maintaining SOC stability.