eMonocot Cyperaceae

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Carbon and hydrogen isotope ratio characterization of methane dynamics for Fluxnet Peatland Ecosystems

Publication Type:Journal Article
Year of Publication:2011
Authors:Alstad, K. P., Whiticar M. J.
Journal:Organic Geochemistry
Keywords:acetate fermentation, bog, carex dominated fen, ch4 production, co2 reduction, dissolved organic-carbon, fresh-water environments, north central alberta, seasonal variability, stable carbon

Methane concentration [CH(4)] and stable isotope ratio values (delta(13)C) characterize methanogenic and methanotrophic processes within two contrasting peatland ecosystems of the Fluxnet Canada Research Network: (i) a western Canada peatland fen in northern Alberta (Fen) and (ii) an eastern Canada peatland bog in southeastern Ontario (Bog). We use carbon isotope ratio discrimination of produced methane (delta(13)C(CH4)) from the precursor carbon compounds (delta(13)C(preC)) to estimate the relative proportions of archaebacterial acetoclastic methanogenesis (AM) and hydrogenotrophic carbonate reduction methanogenesis (HM) in these terrestrial ecosystems. The [CH(4)] and delta(13)C(CH4) signatures describe contrasts in the methanogenic and methanotrophic processes between the Fen and the Bog. The differences are substantiated by stable hydrogen isotope ratio (delta D) separation between the dissolved delta D(CH4) and co-existing delta D(H2O). Methanogenesis at the Fen is dominated by AM, in contrast to the Bog, which is essentially HM. We suggest that this is potentially a result of differences in type/quality of organic substrates. The trajectory of (13)C enrichment in delta(13)C(CH4) values with depth at the Bog reflects a closed system, substrate depletion effect. Our Rayleigh distillation model estimates 58-76% depletion in the source dissolved inorganic carbon (DIC). (C) 2011 Elsevier Ltd. All rights reserved.

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