Linking Freshwater Wetland Productivity and Methane Emissions: A Global Perspective

Understanding the link between wetland gross primary
productivity
(GPP) and methane (CH4) emissions is crucial for global
carbon cycle modeling, yet this coupling remains poorly constrained
at a global scale due to data limitations. To address this critical
gap, we compiled and analyzed the most comprehensive daily scale eddy
covariance data set of GPP and CH4 fluxes. In this analysis,
we define this coupling as the slope of the linear fit between carbon
fixed by ecosystems and carbon emitted as CH4. Results
indicate that the median lag time between CH4 emissions
and GPP is 24.8 days. In terms of their coupling, for every gram of
carbon fixed in wetlands, 0.03 (interquartile range: 0.02–0.05)
grams of carbon are released into the atmosphere as CH4. The upscaling results indicate that the coupling in tropical wetlands
is typically larger than in temperate and boreal wetlands, and the
CO2-equivalent emissions of CH4 surpass the
amount of CO2 absorbed through photosynthesis. These results
enhance our understanding of the complex biogeochemical processes
that drive CH4 emissions, offering valuable insights into
the interplay between carbon fixation and emissions dynamics in wetland
ecosystems.