Abstract
13C natural abundance variations were measured in peat soil and vegetation from two contrasting boreal forest wetlands: an upland watershed basin and a permanently saturated lowland mire. Evidence of methane oxidation was shown in the permanently saturated wetland with δ13C values as low as -97 ‰ in carbonate minerals found in floating peat mats. It is postulated that13C depleted CH4 is oxidized in the mat and reacts with calcium ions to form calcite (identified through x-ray diffraction). Methane flux measurements during the summer of 1992 showed much lower fluxes in areas with floating peat mats relative to open water. Secondary carbonates in the basin peat have isotope compositions close to the δ13C values of the peat organic carbon (-25 ‰), indicating their origin from fermentation and possibly from sulfate-reduction. In the upland basin peat deposits, the δ13CPDB values of organic C were constant with depth, while the permanently saturated mire had localities of13C enrichment in deeper layers of the peat. The13C enrichment may reflect areas of intense CH4 production in which13C enriched residual substrate is left behind during the production of highly13C depleted CH4.
Published Version
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