Fig. 1: Schematic diagram of wetland CH4 dynamics and fractionations for isoTEM. | Communications Earth & Environment

Fig. 1: Schematic diagram of wetland CH4 dynamics and fractionations for isoTEM.

From: Improved global wetland carbon isotopic signatures support post-2006 microbial methane emission increase

Fig. 1

The model simulates δ13C of precursor organic matter (POM) (δ13C-POM), CH4 production, oxidation, and transport to the surface. δ13C-POM is determined by global C3/C4 plant distribution and long-term trends of atmospheric δ13C-CO2. CH4 is produced by two pathways, one using H2 and CO2 and another using acetate, with fractionation factors (α) for HMs (αHM) ≈ 1.030–1.080 and for AMs (αAM) ≈ 1.000–1.040. Produced CH4 is partly oxidized by methanotrophs with a fractionation factor αMO ≈ 1.015–1.035. Residual produced CH4 is emitted to the surface via three processes, plant-mediated transport (TP), diffusion (TD), and ebullition (TE), with different fractionations, αTP ≈ 1.000–1.030, αTD ≈ 1.005, αTE ≈ 1.000, respectively (Supplementary Tables 2–4 and Method “Model development, Model optimization”). Bold and dashed lines in the figure refer to chemical and transport processes, respectively.

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