Uncoupling of acetate degradation from methane formation in Alaskan wetlands: Connections to vegetation distribution

摘要: [1] Laboratory incubations, gas and solute analyses, stable isotope methods were used to investigate the pathway of methanogenesis in 25 wetland peats varying vegetation composition along a latitudinal gradient Alaska. Sites divided into gross classes indicative tropic status: mostly Sphagnum (class 1); plus vascular plants (i.e., Carex) 2); plants, but still containing 3), and; sites dominated by with no visible species 4). The magnitude CO2, acetate CH4 as end products anaerobic metabolism varied greatly, ratios product formation differences C flow corresponded classes, especially at extremes, e.g., acetate-C accounted for 67% total production Sphagnum-rich 1) decreasing 13% devoid sphagna Conversely, comprised only 0.4% class 1 sites, increased 14% 4. Total respiration rates (sum all three products) factor ∼2 among (200–440 nmol ml−1 day−1), differed greatly if was not included suggesting that belowground cycling can be much more rapid than previously thought. Apparent fractionation factors (α = δ13CDIC + 1000/δ13CCH4 1000) estimate methanogenic pathway, i.e., relative contribution CO2 reduction or precursors methane, from ∼1.030 ∼1.080 agreed incubation ratios, underscoring importance presence absence mosses affecting flow. We contend general, including reduction, is impeded northern wetlands compared other compounds its decreases oligotrophy. connection suggests climate change scenarios leading increases plant cover may shift pathways toward acetotrophy methane formation, which positive feedback on warming.