High sedimentary rate of organic carbon enhances the methanogenesis in a subtropical peatland over the past 13 kyr

We revealed a new mechanism which enhanced methanogenesis over the past 13 kyr in the Dajiuhu Peatland, a subtropical peatland in central China. We used two lipid biomarker fluxes for methanogens, archaeol and GDGT-0, along with the abundance of the methanogenic functional gene mcrA to reconstruct methanogenesis intensity in a peat sediment core spanning the past 13 kyr. These proxies showed a strong correlation with the sedimentary rate but no significant relationship with temperature or hydrological changes. We proposed that rapid organic matter deposition, driven by high sedimentary rates, sustained the methanogenic activity by continuously supplying fresh organic carbon substrates (e.g. sugars, amino acids, etc.) that are easily degraded by fermenting microorganisms. In contrast, aerobic methanotrophy, indicated by the pmoA gene, was linked to hydrological changes, emphasizing the role of redox conditions in methane consumption. This decoupling of methanogenesis and aerobic methanotrophy over the past 13 kyr highlights distinct controls on methane production and methane consumption.