Contrasting patterns in the temperature dependence of wetland CH4 and CO2 emissions across globally geographic climate gradients

Determining the temperature dependence of wetland CH₄ and CO₂ emissions is critical for predicting the impacts of climate change on greenhouse gas (GHGs) emissions in wetland ecosystems. However, the spatial variation for temperature dependence of wetland CH₄ and CO₂ emissions is poorly understood, especially at the global scale. Here, we investigate the temperature dependencies of wetland CH₄ and CO₂ emissions across large-scale climatic gradients using 56,271 daily paired observations of ecosystem-level CH₄ and CO₂ emissions in 45 widely distributed wetlands from the FLUXNET-CH₄ database. The temperature dependencies of CH₄ and CO₂ emissions show contrasting spatial patterns across globally geographic climate gradients. Specifically, the temperature dependence of CH₄ emissions  increased with increasing mean annual temperature (MAT), but the opposite was true for that of CO₂ emissions. The ratio of CH₄ to CO₂ emissions was positively dependent on temperature when only MAT and mean annual precipitation were greater than 4.7 °C and 483 mm, respectively. Our results imply that the relative contribution of CH₄ to total GHG emissions increases with ambient temperature increases in a warmer and wetter climate region and could act as a positive feedback mechanism in the future.