Partitioning pathways of CO2 production in peatlands with stable carbon isotopes
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Although methanogenic pathways generally produce equimolar amounts of carbon dioxide and methane, CO2 concentrations are often reported to be higher than CH4 concentrations in both field and laboratory incubation studies of peat decomposition. In field settings, higher pore water concentrations of CO2 may result from the loss of methane by: (1) ebullition due to the low solubility of methane in pore water and (2) vascular-plant transport. Higher CO2 concentrations may also be caused by: (1) production of additional CO2 by high-molecular weight (HMW) organic matter (OM) fermentation and/or (2) respiration from non-methanogenic pathways. In this study of a peatland where advection and transverse dispersion were the dominant pore water solute transport mechanisms, an isotope-mass balance approach was used to determine the proportions of CO2 formed from non-fractionating OM respiration and HMW fermentation relative to CO2 production from methanogenesis. This approach also allowed us to estimate the loss of CH4 from the belowground system. The pathways of CO2 production varied with depth and surface vegetation type. In a Carex-dominated fen, methane production initially produced 40 % of the total CO2 and then increased to 90–100 % with increasing depth. In a Sphagnum-dominated bog, methanogenesis resulted in 60 % of total CO2 production which increased to 100 % at depth. Both bogs and fens showed 85–100 % of methane loss from pore waters. Our results indicate that the isotopic composition of dissolved CO2 is a powerful indicator to allow partitioning of the processes affecting peat remineralization and methane production.
KeywordsPeatlands Climate change Isotope-mass balance CO2 CH4
This research was supported by the National Science Foundation, EAR-0628349 and DEB 0841158. Conversations and interactions with Patrick Crill, Neal Blair, Scott Bridgham, Don Siegel, Lee Slater, Andrew Reeve, Xavier Comas, Juliana D’Andrilli, Mimi Sarkar and especially Julie Shoemaker improved this work. We thank Dr. Kelman Weider and two anonymous reviewers for their helpful comments.
- Blodau C, Roehm CL, Moore TR (2002) Iron, sulfur, and dissolved carbon dynamics in a northern peatland. Arch Hydrobiol 154(4):561–583Google Scholar
- Burdige DJ (2006) Geochemistry of marine sediments. Princeton University Press, Princeton, pp 421–424Google Scholar
- Chanton JP, Chasar L, Glaser PH, Siegel DI (2005) Carbon and hydrogen isotopic effects in microbial methane from terrestrial environments. In: Flanagan LB, Ehleringer JR, Pataki DE (eds) Stable isotopes and biosphere–atmosphere interactions, physiological ecology series. Elsevier, Amsterdam, pp 85–105CrossRefGoogle Scholar
- Chanton JP, Glaser PH, Chasar LS, Burdige DJ, Hines ME, Siegel DI, Tremblay LB, Cooper WT (2008) Radiocarbon evidence for the importance of surface vegetation on fermentation and methanogenesis in contrasting types of boreal peatlands. Glob Biogeochem Cycl 22:GB4022. doi: 10.1029/2008GB003274 CrossRefGoogle Scholar
- Chasar LS, Chanton JP, Glaser PH, Siegel DI, Rivers JS (2000b) Radiocarbon and stable carbon isotopic evidence for transport and transformation of dissolved organic carbon, dissolved inorganic carbon and CH4 in a northern Minnesota Peatland. Glob Biogeochem Cycl 14(4):1095–1108CrossRefGoogle Scholar
- Glaser PH, Siegel DI, Reeve AS, Chanton JP (2006) The hydrology of large peat basins in North America. In: Martini IP, Martinez CA, Chesworth W (eds) Peatlands: basin evolution and depository of records on global environmental and climatic changes. Elsevier, AmsterdamGoogle Scholar
- Knapp AK, Yavitt JB (1992) Evaluation of a closed-chamber method for estimating methane emissions from aquatic plants. Tellus 44B:63–71Google Scholar
- Shoemaker JK, Schrag DP (2011) Does methanogenesis require oxygen? In: Abstract presented at 2011 fall meeting. AGU, San Francisco, 5–9 DecGoogle Scholar
- Tfaily MM, Hamdan R, Corbett JE, Chanton JP, Glaser PH, Cooper WT (in press) Studies of dissolved organic matter reactivity in the Glacial Lake Agassiz Peatlands of northern Minnesota using Fourier transform ion cyclotron resonance mass spectrometry and excitation-emission matrix fluorescence spectroscopy. Geochim Cosmochim ActaGoogle Scholar