Opposing seasonal temperature dependencies of CO 2 and CH 4 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 (CO 2 ) and methane (CH 4 ). Temperature plays a crucial role in wetland GHG emissions, while the general pattern for seasonal temperature dependencies of wetland CO 2 and CH 4 emissions is poorly understood. Here we show opposite seasonal temperature dependencies of CO 2 and CH 4 emissions by using 36,663 daily observations of simultaneous measurements of ecosystem-scale CO 2 and CH 4 emissions in 42 widely distributed wetlands from the FLUXNET-CH 4 database. Specifically, the temperature dependence of CO 2 emissions decreased with increasing monthly mean temperature, but the opposite was true for that of CH 4 emissions. Neglecting seasonal temperature dependencies may overestimate wetland CO 2 and CH 4 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.