Seasonality of temperature dependence of methane fluxes from natural wetlands

Temperature dependence is a crucial parameter in estimating methane (CH4)
fluxes from natural wetlands, yet our understanding of this parameter
remains inadequate. Seasonal fluctuations in water levels and ecosystem
productivity lead to seasonal differences in CH4 production and oxidation.
We hypothesized the existence of seasonality in the temperature dependence
of CH4 fluxes. To validate this hypothesis, we analyzed the FLUXNET-CH4
dataset to determine the seasonal variation in temperature dependence of
CH4 fluxes. We divided the year into six seasons based on air temperature
and assessed the temperature dependence for each season using the apparent
activation energy calculated by the Boltzmann-Arrhenius equation. Our
results showed that temperature dependence showed a unimodal trend with
seasons, with the apparent activation energy peaking in early summer (0.60
eV), and reaching its lowest point in late winter (-0.02 eV). This
seasonal pattern of temperature dependence was consistent across wetlands
with different vegetation types and hydrological conditions. Modeling of
global wetland CH4 emissions based on seasonal temperature dependences
showed a 19% (4-45%) increase in emission rates under the most severe
temperature rise scenario. Our results emphasize the seasonality of
temperature dependence, which will help to further improve current and
future predictions of wetland CH4 emissions.