Spatial and temporal variation in <i>δ</i>¹³C values of methane emitted from a hemiboreal mire: methanogenesis, methanotrophy, and hysteresis

Abstract. The reasons for spatial and temporal variation in methane emission from mire ecosystems are not fully understood. Stable isotope signatures of the emitted can offer clues to causes these variations. We measured (FCH4) 13C signature (δ13C) by automated chambers at a hemiboreal two growing seasons. In addition, we used ambient mixing ratios δ13C calculate mire-scale using nocturnal boundary-layer accumulation approach. Microbial methanogenic methanotrophic communities were determined captured metagenomics analysis. chamber measurements showed large systematic variations δ13C-CH4 up 15 ‰ but smaller less variation. According δ13C–FCH4 relations, methanotrophy was unlikely be dominating cause Instead, an indication substrate availability methanogenesis being major factor explaining Genetic analysis indicated that all sample locations able utilize both hydrogenotrophic acetoclastic pathways could thus adapt changes available substrate. FCH4 over seasons hysteresis-like behavior high-emission locations, indicative time-lagged responses temperature availability. upscaled similar average values −81.3 −79.3 ‰, respectively, mire. close correspondence obtained methods lends confidence isotopic signature. This other recently published data on CH4 northern mires considerably lower than atmospheric inversion studies sources, suggesting need revision model input.