Stable carbon isotope fractionation during methanogenesis in three boreal peatland ecosystems

[摘要] The degradation of organic matter to CH₄ and CO₂ was investigatedin three different boreal peatland systems in Finland, a mesotrophic fen(MES), an oligotrophic fen (OLI), and an ombrotrophic peat (OMB). MES hadsimilar production rates of CO₂ and CH₄, but the two nutrient-poorpeatlands (OLI and OMB) produced in general more CO₂ than CH₄.δ¹³C analysis of CH₄ and CO₂ in the presence andabsence methyl fluoride (CH₃F), an inhibitor of acetoclasticmethanogenesis, showed that CH₄ was predominantly produced byhydrogenotrophic methanogenesis and that acetoclastic methanogenesis onlyplayed an important role in MES. These results, together with ourobservations concerning the collective inhibition of CH₄ and CO₂production rates by CH₃F, indicate that organic matter was degradedthrough different paths in the mesotrophic and the nutrient-poor peatlands.In the mesotrophic fen, the major process is canonical fermentation followedby acetoclastic and hydrogenotrophic methanogenesis, while in thenutrient-poor peat, organic matter was apparently degraded to a large extentby a different path which finally involved hydrogenotrophic methanogenesis.Our data suggest that degradation of organic substances in the oligotrophicenvironments was incomplete and involved the use of organic compounds asoxidants.

[学科分类] 地球化学与岩石