Reduced methane emissions in former permafrost soils driven by vegetation and microbial changes following drainage

• Published in: Global Change Biology
• Main Authors: Keuschnig, Christoph, Larose, Catherine, Rudner, Mario, Pesqueda, Argus, Doleac, Stéphane, Elberling, Bo, Björk, Robert, Klemedtsson, Leif, Björkman, Mats
• Other Authors: Ampère, Département Bioingénierie (BioIng), Ampère (AMPERE), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-École Centrale de Lyon (ECL), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Göteborgs Universitet = University of Gothenburg (GU), École polytechnique (X), Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management Copenhagen (IGN), Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH)-Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH), Gothenburg Global Biodiversity Centre, Research and development projects to future research leaders at FORMAS – Swedish Research Council for Sustainable Development grant agreement 2016-01187 (M.P.B.)Danish National Research Foundation, Center for Permafrost, CENPERM DNRF100 (B.E)The strategic research environment BECC - Biodiversity and Ecosystem services in a Changing Climate, SITES - Swedish Infrastructure for Ecosystem Science and the foundations of H. Ax:son Johnson, Wilhelm & Martina Lundgren, Knut & Alice Wallenberg, and Carl Tryggers, European Project: 657627,H2020,H2020-MSCA-IF-2014,PERMTHAW(2016)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: Arctic; climate change; methane; post-permafrost soil; Tundra ecosystems; [SDE]Environmental Sciences; Climate change; permafrost; Tundra
• Online Access: https://hal.science/hal-03827512; https://doi.org/10.1111/gcb.16137

International audience In Arctic regions, thawing permafrost soils are projected to release 50 to 250 Gt of carbon by 2100. This data is mostly derived from carbon-rich wetlands, although 71% of this carbon pool is stored in faster-thawing mineral soils, where ecosystems close to the outer boundaries of permafrost regions are especially vulnerable. Although extensive data exists from currently thawing sites and short-term thawing experiments, investigations of the long-term changes following final thaw and co-occurring drainage are scarce. Here we show ecosystem changes at two comparable tussocktundra sites with distinct permafrost thaw histories, representing 15 and 25 years of natural drainage, that resulted in a 10-fold decrease in CH4 emissions (3.2 ± 2.2 vs. 0.3 ± 0.4 mg C-CH4 m−2 day−1), while CO2 emissions were comparable. These data extend the time perspective from earlier studies based on short-term experimental drainage. The overall microbial community structures did not differ significantly between sites, although the drier top soils at the most advanced site led to a loss of methanogens and their syntrophic partners in surface layers while the abundance of methanotrophs remained unchanged. The resulting deeper aeration zones likely increased CH4 oxidation due to the longer residence time of CH4 in the oxidation zone, while the observed loss of aerenchyma plants reduced CH4 diffusion from deeper soil layers directly to the atmosphere. Our findings highlight the importance of including hydrological, vegetation and microbial specific responses when studying long-termeffects of climate change on CH4 emissions and underscores the need for data from different soil types and thaw histories.