Increased CO2 fluxes under warming tests and soil solution chemistry in Histic and Turbic Cryosols, Salluit, Nunavik, Canada

• Published in: Soil Biology and Biochemistry
• Main Authors: Fouché, Julien, Keller, Catherine, Allard, Michel, Ambrosi, Jean-Paul
• Other Authors: Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Recherche en Informatique (LRI), Université Paris-Sud - Paris 11 (UP11)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Université Paris-Saclay, CentraleSupélec, Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11), Musée des Eyzies
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Arctic; Nunavik; Canada; Salluit; Global warming; permafrost; Tundra
• Online Access: https://hal.science/hal-01458015; https://doi.org/10.1016/j.soilbio.2013.10.007

International audience Cryosols in tundra ecosystems contain large stocks of organic carbon as peat and as organic cryoturbated layers. Increased organic mater decomposition rate in those Arctic soils due to increasing soil temperatures and to permafrost thawing can lead to the release of greenhouse gases, thus potentially creating a positive feedback on global warming. Instrumentation was installed on permafrost terrain in Salluit (Nunavik, Canada; 62 degrees 14'N, 75 degrees 38'W) to monitor respiration of two Cryosols under both natural and experimental warmed conditions and to simultaneously monitor the soil solution composition in the active layer throughout a thawing season. Two experimental sites under tussock tundra vegetation were set up: one is on a Histic Cryosol (H site) in a polygonal peatland; the other one is on a Turbic Cryosol reductaquic (T site) on post-glacial marine clays. At each site an open top chamber was installed from mid-July to the end of August 2010 to warm the soil surface. Thermistors and soil moisture probes were installed both in natural (N), or non-modified, surface thermal conditions and in warmed (W) stations, i.e. under an open top chamber. At each station, ecosystem respiration (ER) was measured three times per day every second day with an opaque closed chamber linked to a portable IRGA. Soil solutions were also sampled every alternate day at 10, 20 and 30 cm depths and analysed for dissolved organic C (DOC), total dissolved nitrogen (TON) and major elements. The experimental warming thickened the active layer in the Histic soil while it did not in the Turbic soil. In natural conditions, average ER at the HN station (1.27 +/- 0.32 mu mol CO2 m(-2) s(-1)) was lower than at the TN station (1.96 +/- 0.41 mu mol CO2 m(-2) s(-1)). A soil surface warming of 2.4 degrees C lead to a similar to 64% increase in ER at the HW station. At the TW station a similar to 2.1 degrees C increase induced an average ER increase of similar to 48%. Temperature sensitivity of ER, expressed by a ...