Assessing the role of different wetland methane emission pathways with a biogeochemistry model

One great challenge to estimate regional wetland CH4 emissions is due to the uncertain pathways of methane transport from wetland to the atmosphere. Here, we refine the algorithms of diffusion, bubbling, and plan-aided transport pathways in our existing biogeochemistry model, the Terrestrial Ecosystem Model (TEM). The revised TEM is tested at two peatland sites in Michigan, USA. For the site with plant communities dominated by Chamaedaphne calyculata, an ericaceous shrub, the model estimated CH4 fluxes agree well with observations at a daily time step, with a linear fitting of intercept 8.9 mg m-2 d-1 and slope 0.47 (R2=0.33). For the site with areas dominated by plants with aerenchymatous tissues, a linear fitting is of an intercept 99.8 mg m-2 d-1 and a slope 0.72 (R2=0.49) between model estimates and observations. At both sites, the model showed the diffusion is the major pathway for CH4 effluxes to the atmosphere, followed by plant aided transport and ebullition. Their relative contributions depend on the vegetation type. Next, we will apply the model to temperate wetlands in the United States to further assess the role of these pathways in determining methane emissions.