Differences in the temperature dependence of wetland CO2 and CH4 emissions vary with water table depth

Wetland CH4 emissions have been demonstrated to be more sensitive than wetland CO2 emissions to increasing temperatures, which may result in a greater relative contribution of CH4 to total GHG emissions under climate warming. However, it is not clear whether this greater sensitivity occurs globally across diverse hydrologic regimes. Here, we evaluate the temperature dependence of CO2 and CH4 emissions on water table depth using a global database and show similarities in the temperature dependence of CO2 and CH4 emissions. A lower water table is associated with a decrease in the temperature dependence of CH4 emissions and a higher water table has the opposite effect. Water table depth does not affect the temperature dependence of CO2 emissions. Our findings suggest the stimulatory effect of increasing temperature on wetland CH4 emissions may not always be stronger than that on CO2 emissions and depends on the wetland water table. Climate change may result in larger releases of CH4 than CO2 from wetlands as CH4 emissions seem to be more sensitive to temperature. Globally, CO2 and CH4 emissions show a similar temperature dependence but this is modulated by wetland water table depth, which affects CH4 (but not CO2) emissions.