Opposing seasonal temperature dependencies of CO2 and CH4 emissions from wetlands

Wetlands are critically important to global climate change because of their role in modulating the release of atmospheric greenhouse gases (GHGs) carbon dioxide (CO2 ) and methane (CH4 ). Temperature plays a crucial role in wetland GHG emissions, while the general pattern for seasonal temperature dependencies of wetland CO2 and CH4 emissions is poorly understood. Here we show opposite seasonal temperature dependencies of CO2 and CH4 emissions by using 36,663 daily observations of simultaneous measurements of ecosystem-scale CO2 and CH4 emissions in 42 widely distributed wetlands from the FLUXNET-CH4 database. Specifically, the temperature dependence of CO2 emissions decreased with increasing monthly mean temperature, but the opposite was true for that of CH4 emissions. Neglecting seasonal temperature dependencies may overestimate wetland CO2 and CH4 emissions compared to the use of a year-based static and consistent temperature dependence parameter when only considering temperature effects. Our findings highlight the importance of incorporating the remarkable seasonality in temperature dependence into process-based biogeochemical models to predict feedbacks of wetland GHG emissions to climate warming.