Response of Community Characteristics and Assembly Mechanisms of cbbL-Carrier Carbon-Fixing Microorganisms to Precipitation Changes in Alpine Lakeshore Wetland

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Precipitation change strongly influences soil microbial communities, and precipitation patterns have become a key factor affecting carbon and nitrogen cycling processes in wetland ecosystems. The cbbL gene is a key gene in the fixation of carbon dioxide during the Calvin cycle. However, the response of cbbL-carrier carbon-fixing microorganisms in the lakeshore wetland to precipitation change remains unclear. To this end, we established 25% and 50% increased and decreased precipitation treatments, along with a natural control, and used high-throughput sequencing to investigate the response of the cbbL-carrier carbon-fixing microbial community in a lakeshore wetland of Qinghai Lake in response to precipitation change. The results showed that a 25% reduced precipitation treatment significantly increased the relative abundance of Chlorophyta and Bradyrhizobium. pH was found to be the most important factor influencing the carbon-fixing microbial community, with a significant positive correlation with Ferrithrix. A 25% increased precipitation treatment significantly increased the relative abundance of aerobic chemoheterotrophy and chemoheterotrophy, while a 25% reduced precipitation treatment significantly increased the relative abundance of nitrogen fixation. The increased precipitation and 50% reduced precipitation treatments shift the community assembly process of cbbL-carrier carbon-fixing microorganisms from randomness to determinism. Co-occurrence network analysis showed that the network complexity and connectivity between species of cbbL-carrier carbon-fixing microorganisms initially decreased and then increased with increasing precipitation. In summary, precipitation change tended to reduce the carbon sequestration potential of the lakeshore wetland, while a 25% reduced precipitation treatment favored the nitrogen fixation process in these wetlands.