Nonlinear Responses of Anaerobic Methane Oxidation to Water Table Drawdown in Peatlands

Anaerobic oxidation of methane (AOM) serves as a key methane (CH4) sink that attenuates methane emissions from peatlands. Climate change has induced widespread water table drawdown in peatlands, but the response of AOM to the water table depth (WTD) and the temperature sensitivity remain unclear. Using 13CH4-labeled incubations, we investigated the potential of AOM in composite peat samples (0–30 cm) collected from the Zoige peatland on the eastern Qinghai–Tibet Plateau along a drainage gradient (annual mean WTD of 15–45 cm) across temperatures of 5–25 °C. We found that AOM rates have a unimodal response to increasing WTD, peaking at sites with an annual mean WTD of a 30 cm WTD. This result was further supported by a global synthesis of 13C/14C-tracer-based peatland AOM measurements. The lowest temperature sensitivity (Q10 = 2.4) and activation energy (Ea = 57 kJ mol–1) also occurred at this WTD. Metabolic pathways shifted from ANME-2d archaea-driven syntrophy to NC10 bacterial-mediated AOM along the WTD gradient. Our findings provide a mechanistic framework to develop rewetting strategies to raise the climate mitigation potential of peatlands under future warming.