Global Patterns and Environmental Drives of Nitrite/Nitrate-Dependent Anaerobic Methane Oxidation Across Natural Ecosystems

The nitrite/nitrate-dependent anaerobic methane oxidation (DAMO) plays a crucial role in mitigating methane (CH₄) emissions and nitrogen (N) loadings in natural ecosystems, significantly contributing to global CH₄ consumption and N balances. However, the global patterns and environmental drivers of these processes across natural ecosystems remain unclear, hindering the estimation and management of global CH₄ emissions. In this study, we compiled a global dataset comprising 527 observations from 59 published studies across terrestrial and aquatic ecosystems. We found a global mean N-DAMO rate of 19.2 nmol g⁻¹ d⁻¹, which includes a mean nitrite-DAMO rate of 13.8 nmol g⁻¹ d⁻¹ and a mean nitrate-DAMO rate of 7.4 nmol g⁻¹ d⁻¹. Notably, N-DAMO rates were higher in soils from croplands (47.9 nmol g⁻¹ d⁻¹) and forests/grasslands (30.9 nmol g⁻¹ d⁻¹) compared to those from freshwater (8.4 nmol g⁻¹ d⁻¹) and coastal regions (12.7 nmol g⁻¹ d⁻¹). Nitrite-DAMO contributes more than 50% of the N-DAMO; however, this contribution was lowest in coastal regions (51.1%). The rates of N-DAMO exhibited a unimodal relationship with temperature and a significantly negative relationship with precipitation. Among soil properties, extractable N, substrates for N-DAMO, showed significant inhibition on N-DAMO rates, implying a diminished role of N-DAMO in global N enrichment scenarios. Our results illustrate that N-DAMO across natural ecosystems can reduce CH₄ emissions by 229.6 Tg year⁻¹ and has substantial potential for N removal worldwide. This work highlights the significance of N-DAMO for global CH₄ emission estimation and N management.