title: Experimental warming differentially affects microbial structure and activity in two contrasted moisture sites in a Sphagnum-dominated peatland.
abstract: Several studies on the impact of climate warming have indicated that peat decomposition/mineralization will be enhanced. Most of these studies deal with the impact of experimental warming during summer when prevalent abiotic conditions are favorable to decomposition. Here, we investigated the effect of experimental air warming by open-top chambers (OTCs) on water-extractable organic matter (WEOM), microbial biomasses and enzymatic activities in two contrasted moisture sites named Bog and Fen sites, the latter considered as the wetter ones. While no or few changes in peat temperature and water content appeared under the overall effect of OTCs, we observed that air warming smoothed water content differences and led to a decrease in mean peat temperature at the warmed Bog sites. This thermal discrepancy between the two sites led to contrasting changes in microbial structure and activities: a rise in hydrolytic activity at the warmed Bog sites and a relative enhancement of bacterial biomass at the warmed Fen sites. These features were not associated with any change in WEOM properties namely carbon and sugar contents and aromaticity, suggesting that air warming did not trigger any shift in OM decomposition. Using various tools, we show that the use of single indicators of OM decomposition can lead to fallacious conclusions. Lastly, these patterns may change seasonally as a consequence of complex interactions between groundwater level and air warming, suggesting the need to improve our knowledge using a high time-resolution approach.
authors.affiliation: Université d'Orléans, ISTO, UMR 7327, 45071 Orléans, France; CNRS, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France. Electronic address: fdelarue@mnhn.fr.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Delarue
authors.affiliation: Laboratoire de Chrono-Environnement, UMR CNRS 6249, UFR des Sciences et Techniques, 16 route de Gray, Université de Franche-Comté, F-25030 Besançon, France; École Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Laboratory of Ecological Systems (ECOS), Bâtiment GR, Station 2, CH-1015 Lausanne, Switzerland; WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Site Lausanne, Station 2, Case postale 96, CH-1015 Lausanne, Switzerland.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Buttler
authors.affiliation: École Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Laboratory of Ecological Systems (ECOS), Bâtiment GR, Station 2, CH-1015 Lausanne, Switzerland; WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Site Lausanne, Station 2, Case postale 96, CH-1015 Lausanne, Switzerland; University of Ferrara, Department of Life Science and Biotechnology, Corso Ercole I d'Este 32, I-44121 Ferrara, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Bragazza
authors.affiliation: CNRS, Laboratoire de Synthèse et de Réactivité des Substances Naturelles-UMR 6514, Université de Poitiers, 4 rue M. Brunet, 86022 Poitiers Cedex, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Grasset
authors.affiliation: École Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Laboratory of Ecological Systems (ECOS), Bâtiment GR, Station 2, CH-1015 Lausanne, Switzerland; WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Site Lausanne, Station 2, Case postale 96, CH-1015 Lausanne, Switzerland.
authors.forename: Vincent E J
authors.initials: VE
authors.lastname: Jassey
authors.affiliation: Université d'Orléans, ISTO, UMR 7327, 45071 Orléans, France; CNRS, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Gogo
authors.affiliation: Université d'Orléans, ISTO, UMR 7327, 45071 Orléans, France; CNRS, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France.
authors.forename: Fatima
authors.initials: F
authors.lastname: Laggoun-Défarge
mesh_terms: D057231:Climate Change; D017753:Ecosystem; D012987:Soil; D012988:Soil Microbiology; D044003:Sphagnopsida; D013696:Temperature
chemical_list: D012987:Soil
keywords: Carbon; Climate change; Enzymes; Microbial biomass; Moisture; Open-top chambers