Soil incubations reproduce field methane dynamics in a subarctic wetland
A major challenge in peatland carbon cycle modeling is the estimation of subsurface methane (CH4) and carbon dioxide (CO2) production and consumption rates and pathways. The most common methods for modeling these processes are soil incubations and stable isotope modeling, both of which may involve departures from field conditions. To explore the impacts of these departures, we measured CH4/CO2 concentration ratios and 13C fractionation factors (αC, indicating CH4 production pathways) in field pore water from a thawing subarctic peatland, and compared these values to those observed in incubations of corresponding peat samples. Incubation CH4/CO2 production ratios were significantly and positively correlated with observed field CH4/CO2 concentration ratios, though observed field ratios were ~20 % of those in incubations due to CH4’s lower solubility in pore water. After correcting the field ratios for CH4 loss with an isotope mass balance model, the incubation CH4/CO2 ratios and αC were both significantly positively correlated with field ratios and αC (respectively), both with slopes indistinguishable from 1. Although CH4/CO2 ratios and αC were slightly higher in the incubations, these shifts were consistent along the thaw progression, indicating that ex situ incubations can replicate trends in in situ CH4 production.
KeywordsPeatlands Methane Geochemistry Soil incubations Stable isotopes
We thank Tyler Mauney for incubation preparation, Tyler Logan for sampling assistance, and the Abisko Scientific Research Station for sampling infrastructure. This work was funded by the US Department of Energy Office of Biological and Environmental Research under the Genomic Science program (Awards DE-SC0004632 and DE-SC0010580). SR Saleska and VI Rich received support through the Ecosystem Genomics Initiative, by the University of Arizona Technology and Research Initiative Fund, through the Water, Environmental and Energy Solutions Initiative.
- Balch WE, Fox GE, Magrum LJ et al (1979) Methanogens: reevaluation of a unique biological group. Microbiol Rev 43:260–296Google Scholar
- Broder T, Blodau C, Biester H, Knorr KH (2015) Sea spray, trace elements, and decomposition patterns as possible constraints on the evolution of CH4 and CO2 concentrations and isotopic signatures in oceanic ombrotrophic bogs. Biogeochemistry 122:327–342. doi: 10.1007/s10533-014-0044-5 CrossRefGoogle Scholar
- Hines ME, Duddleston KN, Rooney-Varga JN, et al (2008) Uncoupling of acetate degradation from methane formation in Alaskan wetlands: connections to vegetation distribution. Glob Biogeochem Cycles 22:GB2017. doi: 10.1029/2006GB002903
- Lovley DR, Klug MJ (1983) Methanogenesis from methanol and methylamines and acetogenesis from hydrogen and carbon dioxide in the sediments of a eutrophic lake. Appl Environ Microbiol 45:1310–1315Google Scholar