24 Mar 2022
24 Mar 2022
Status: a revised version of this preprint is currently under review for the journal BG.

Spatial and temporal variation of 13C signature of methane emitted from a temperate mire: Methanogenesis, methanotrophy, and hysteresis

Janne Rinne1,2, Patryk Łakomiec1, Patrik Vestin1, Joel D. White1, Per Weslien3, Julia Kelly4, Natascha Kljun4, Lena Ström1, and Leif Klemedtsson3 Janne Rinne et al.
  • 1Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden
  • 2Natural Resources Institute Finland, Production Systems Unit, Helsinki, Finland
  • 3University of Gothenburg, Department of Earth Sciences, Gothenburg, Sweden
  • 4Lund University, Centre for Environmental and Climate Science, Lund, Sweden

Abstract. The reasons for spatial and temporal variation of methane emission from mire ecosystems are not fully understood. Stable isotope signatures of the emitted methane can offer cues to the causes of these variations. We measured the methane emission and 13C-signature of emitted methane by automated chambers at a temperate mire for two growing seasons. In addition, we used ambient methane mixing ratios and δ13C-CH4 to calculate a mire-scale 13C signature using a nocturnal boundary-layer accumulation approach. Microbial methanogenic and methanotrophic communities were determined by a captured metagenomics analysis. The chamber measurements showed large and systematic spatial variations in δ13C-CH4 of up to 15 ‰ but smaller and less systematic temporal variation. The trophic status of methanogenesis was the dominant factor explaining the spatial variation. Genetic analysis indicated that methanogenic communities at all sample locations were able to utilize both hydrogenotrophic and acetoclastic pathways and could thus adapt to trophic status. The temporal variation of methane emission and δ13C-CH4 over the growing seasons showed hysteresis-like behavior, indicative of time-lagged responses to temperature and trophic status. The up-scaled chamber measurements and nocturnal boundary-layer accumulation measurements showed similar average δ13C-CH4 values of -81.3 ‰ and -79.3 ‰, respectively, lending confidence to the use of mire scale isotopic signatures to be used in e.g. atmospheric inversion modelling of methane sources. The results obtained can constrain our theories on the variability of methane emission from mire ecosystems and be useful in development of numerical models of mire biogeochemistry.

Janne Rinne et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-76', Anonymous Referee #1, 15 Apr 2022
    • AC1: 'Reply on RC1', Janne Rinne, 25 May 2022
  • RC2: 'Comment on bg-2022-76', Edward Hornibrook, 06 May 2022
    • AC2: 'Reply on RC2', Janne Rinne, 25 May 2022

Janne Rinne et al.


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Short summary
The study uses stable isotope 13C of carbon in methane to investigate the origins of spatial and temporal variation of methane emitted by a temperate wetland ecosystem. The results indicate that methane production is more important for spatial variation than methane consumption by micro-organisms. Temporal variation in seasonal timescale is most likely affected by more than one driver simultaneously.