Long-term in situ permafrost thaw effects on bacterial communities and potential aerobic respiration

• Published in: The ISME Journal
• Main Authors: Monteux, Sylvain, Weedon, James, Blume-Werry, Gesche, Gavazov, Konstantin, Jassey, Vincent, Johansson, Margareta, Keuper, Frida, Olid, Carolina, Dorrepaal, Ellen
• Other Authors: Department of Ecological Science Amsterdam, Vrije Universiteit Brussel (VUB), Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales Toulouse (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Department of Systems Ecology, University of Amsterdam Amsterdam (UvA), Climate Impacts Research Centre (CIRC), Umeå University
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDE.MCG]Environmental Sciences/Global Changes; permafrost
• Online Access: https://hal.archives-ouvertes.fr/hal-02377983; https://hal.archives-ouvertes.fr/hal-02377983/document; https://hal.archives-ouvertes.fr/hal-02377983/file/Monteux2018_ISME_J.pdf; https://doi.org/10.1038/s41396-018-0176-z

International audience The decomposition of large stocks of soil organic carbon in thawing permafrost might depend on more than climate change-induced temperature increases: indirect effects of thawing via altered bacterial community structure (BCS) or rooting patterns are largely unexplored. We used a 10-year in situ permafrost thaw experiment and aerobic incubations to investigate alterations in BCS and potential respiration at different depths, and the extent to which they are related with each other and with root density. Active layer and permafrost BCS strongly differed, and the BCS in formerly frozen soils (below the natural thawfront) converged under induced deep thaw to strongly resemble the active layer BCS, possibly as a result of colonization by overlying microorganisms. Overall, respiration rates decreased with depth and soils showed lower potential respiration when subjected to deeper thaw, which we attributed to gradual labile carbon pool depletion. Despite deeper rooting under induced deep thaw, root density measurements did not improve soil chemistry-based models of potential respiration. However, BCS explained an additional unique portion of variation in respiration, particularly when accounting for differences in organic matter content. Our results suggest that by measuring bacterial community composition, we can improve both our understanding and the modeling of the permafrost carbon feedback.