The relative importance of methanogenesis in the decomposition of organic matter in northern peatlands: Relative Importance of Methanogenesis
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Journal of Geophysical Research: Biogeosciences, ISSN: 2169-8953, Vol: 120, Issue: 2, Page: 280-293
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- Earth and Planetary Sciences; Agricultural and Biological Sciences; Environmental Science; Peatlands; Permafrost; CO2 production; CH4 loss; Bog; Fen; Anaerobic carbon mineralization; Lake Agassiz peatland; Lost River; Peatland; Methane production; Stable Carbon; Pore water; Minnesota; Wetlands; Respiration; Biochemistry; Biogeochemistry; Environmental Sciences; Oceanography
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Using an isotope-mass balance approach and assuming the equimolar production of COand CHfrom methanogenesis (e.g., anaerobic decomposition of cellulose), we calculate that the proportion of total COproduction from methanogenesis varies from 37 to 83% across a variety of northern peatlands. In a relative sense, methanogenesis was a more important pathway for decomposition in bogs (80 ± 13% of COproduction) than in fens (64 ± 5.7% of COproduction), but because fens contain more labile substrates they may support higher CHproduction overall. The concentration of COproduced from methanogenesis (CO) can be considered equivalent to CHconcentration before loss due to ebullition, plant-mediated transport, or diffusion. Bogs produced slightly less COthan fens (2.9 ± 1.3 and 3.7 ± 1.4 mmol/L, respectively). Comparing the quantity of CHpresent to CO, fens lost slightly more CHthan bogs (89 ± 2.8% and 82 ± 5.3%, respectively) likely due to the presence of vascular plant roots. In collapsed permafrost wetlands, bog moats produced half the amount of CO(0.8 ± 0.2 mmol/L) relative to midbogs (1.6 ± 0.6 mmol/L) and methanogenesis was less important (42 ± 6.6% of total COproduction relative to 55 ± 8.1%). We hypothesize that the lower methane production potential in collapsed permafrost wetlands occurs because recently thawed organic substrates are being first exposed to the initial phases of anaerobic decomposition following collapse and flooding. Bog moats lost a comparable amount of CHas midbogs (63 ± 7.0% and 64 ± 9.3%).