Controls on Stable Methane Isotope Values in Northern Peatlands and Potential Shifts in Values Under Permafrost Thaw Scenarios

Author:

Kuhn McKenzie A.12ORCID,Varner Ruth K.12ORCID,McCalley Carmody K.3ORCID,Perryman Clarice R.124,Aurela Mika5ORCID,Burke Sophia A.12ORCID,Chanton Jeffrey P.6ORCID,Crill Patrick M.78,DelGreco Jessica2,Deng Jia2ORCID,Heffernan Liam9ORCID,Herrick Christina2ORCID,Hodgkins Suzanne B.10ORCID,Jones Cheristy P.12,Juutinen Sari5ORCID,Kane Evan S.1112ORCID,Lamit Louis J.13,Larmola Tuula14ORCID,Lilleskov Erik12ORCID,Olefeldt David15,Palace Michael W.12,Rich Virginia I.11ORCID,Schulze Christopher1516ORCID,Shorter Joanne H.17ORCID,Sullivan Franklin B.2ORCID,Sonnentag Oliver16,Turetsky Merritt R.18,Waldrop Mark P.19ORCID

Affiliation:

1. Department of Earth Sciences University of New Hampshire Durham NH USA

2. Earth Systems Research Center Institute for the Study of Earth, Oceans and Space University of New Hampshire Durham NH USA

3. Gosnell School of Life Science Rochester Institute of Technology Rochester NY USA

4. Department of Earth Systems Science Stanford University Stanford CA USA

5. Finnish Meteorological Institute Climate System Research Helsinki Finland

6. Department of Earth Ocean and Atmospheric Science Florida State University Tallahassee FL USA

7. Department of Geological Sciences Stockholm University Stockholm Sweden

8. Bolin Center for Climate Research Stockholm University Stockholm Sweden

9. Department of Ecology and Genetics/Limnology Evolutionary Biology Centre Uppsala University Uppsala Sweden

10. Department of Microbiology The Ohio State University Columbus OH USA

11. College of Forest Resources and Environmental Science Houghton MI USA

12. USDA Forest Service Northern Research Station Houghton MI USA

13. Department of Biology Syracuse University Syracuse NY USA

14. Natural Resources Institute Finland Helsinki Finland

15. Department of Renewable Resources University of Alberta Edmonton AB Canada

16. Département de Géographie Université de Montréal Montréal QC Canada

17. Aerodyne Research, Inc. Billerica MA USA

18. Department of Ecology and Evolutionary Biology University of Colorado Boulder Boulder CO USA

19. Geology, Minerals, Energy and Geophysics Science Center U.S. Geological Survey Menlo Park CA USA

Abstract

AbstractNorthern peatlands are a globally significant source of methane (CH4), and emissions are projected to increase due to warming and permafrost loss. Understanding the microbial mechanisms behind patterns in CH4 production in peatlands will be key to predicting annual emissions changes, with stable carbon isotopes (δ13C‐CH4) being a powerful tool for characterizing these drivers. Given that δ13C‐CH4 is used in top‐down atmospheric inversion models to partition sources, our ability to model CH4 production pathways and associated δ13C‐CH4 values is critical. We sought to characterize the role of environmental conditions, including hydrologic and vegetation patterns associated with permafrost thaw, on δ13C‐CH4 values from high‐latitude peatlands. We measured porewater and emitted CH4 stable isotopes, pH, and vegetation composition from five boreal‐Arctic peatlands. Porewater δ13C‐CH4 was strongly associated with peatland type, with δ13C enriched values obtained from more minerotrophic fens (−61.2 ± 9.1‰) compared to permafrost‐free bogs (−74.1 ± 9.4‰) and raised permafrost bogs (−81.6 ± 11.5‰). Variation in porewater δ13C‐CH4 was best explained by sedge cover, CH4 concentration, and the interactive effect of peatland type and pH (r2 = 0.50, p < 0.001). Emitted δ13C‐CH4 varied greatly but was positively correlated with porewater δ13C‐CH4. We calculated a mixed atmospheric δ13C‐CH4 value for northern peatlands of −65.3 ± 7‰ and show that this value is more sensitive to landscape drying than wetting under permafrost thaw scenarios. Our results suggest northern peatland δ13C‐CH4 values are likely to shift in the future which has important implications for source partitioning in atmospheric inversion models.

Publisher

American Geophysical Union (AGU)

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