title: Persistent high temperature and low precipitation reduce peat carbon accumulation.
abstract: Extreme climate events are predicted to become more frequent and intense. Their ecological impacts, particularly on carbon cycling, can differ in relation to ecosystem sensitivity. Peatlands, being characterized by peat accumulation under waterlogged conditions, can be particularly sensitive to climate extremes if the climate event increases soil oxygenation. However, a mechanistic understanding of peatland responses to persistent climate extremes is still lacking, particularly in terms of aboveground-belowground feedback. Here, we present the results of a transplantation experiment of peat mesocosms from high to low altitude in order to simulate, during 3 years, a mean annual temperature c. 5 °C higher and a mean annual precipitation c. 60% lower. Specifically, we aim at understanding the intensity of changes for a set of biogeochemical processes and their feedback on carbon accumulation. In the transplanted mesocosms, plant productivity showed a species-specific response depending on plant growth forms, with a significant decrease (c. 60%) in peat moss productivity. Soil respiration almost doubled and Q10halved in the transplanted mesocosms in combination with an increase in activity of soil enzymes. Spectroscopic characterization of peat chemistry in the transplanted mesocosms confirmed the deepening of soil oxygenation which, in turn, stimulated microbial decomposition. After 3 years, soil carbon stock increased only in the control mesocosms whereas a reduction in mean annual carbon accumulation of c. 30% was observed in the transplanted mesocosms. Based on the above information, a structural equation model was built to provide a mechanistic understanding of the causal connections between peat moisture, vegetation response, soil respiration and carbon accumulation. This study identifies, in the feedback between plant and microbial responses, the primary pathways explaining the reduction in carbon accumulation in response to recurring climate extremes in peat soils.
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research, WSL Site Lausanne, Station 2, 1015, Lausanne, Switzerland.|Ecole Polytechnique Fédérale de Lausanne EPFL, Laboratory of Ecological Systems ECOS, School of Architecture, Civil and Environmental Engineering ENAC, Station 2, 1015, Lausanne, Switzerland.|Department of Life Science and Biotechnologies, University of Ferrara, Corso Ercole I d'Este 32, Ferrara, 44121, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Bragazza
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research, WSL Site Lausanne, Station 2, 1015, Lausanne, Switzerland.|Ecole Polytechnique Fédérale de Lausanne EPFL, Laboratory of Ecological Systems ECOS, School of Architecture, Civil and Environmental Engineering ENAC, Station 2, 1015, Lausanne, Switzerland.|Laboratoire de Chrono-Environnement, UMR CNRS 6249, UFR des Sciences et Techniques, Université de Franche Comté, Besançon, 25030, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Buttler
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research, WSL Site Lausanne, Station 2, 1015, Lausanne, Switzerland.|Ecole Polytechnique Fédérale de Lausanne EPFL, Laboratory of Ecological Systems ECOS, School of Architecture, Civil and Environmental Engineering ENAC, Station 2, 1015, Lausanne, Switzerland.
authors.forename: Bjorn J M
authors.initials: BJ
authors.lastname: Robroek
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research, WSL Site Lausanne, Station 2, 1015, Lausanne, Switzerland.|Ecole Polytechnique Fédérale de Lausanne EPFL, Laboratory of Ecological Systems ECOS, School of Architecture, Civil and Environmental Engineering ENAC, Station 2, 1015, Lausanne, Switzerland.
authors.forename: Remy
authors.initials: R
authors.lastname: Albrecht
authors.affiliation: Department of the Sciences of Agriculture, Food and Environment, University of Foggia, via Napoli 25, 71122, Foggia, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Zaccone
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research, WSL Site Lausanne, Station 2, 1015, Lausanne, Switzerland.|Ecole Polytechnique Fédérale de Lausanne EPFL, Laboratory of Ecological Systems ECOS, School of Architecture, Civil and Environmental Engineering ENAC, Station 2, 1015, Lausanne, Switzerland.
authors.forename: Vincent E J
authors.initials: VE
authors.lastname: Jassey
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research, WSL Site Lausanne, Station 2, 1015, Lausanne, Switzerland.|Ecole Polytechnique Fédérale de Lausanne EPFL, Laboratory of Ecological Systems ECOS, School of Architecture, Civil and Environmental Engineering ENAC, Station 2, 1015, Lausanne, Switzerland.
authors.forename: Constant
authors.identifier: 0000-0001-7780-5366
authors.initials: C
authors.lastname: Signarbieux
mesh_terms: D002244:Carbon / Q000032:analysis*; D057486:Carbon Cycle; D002980:Climate; D012987:Soil / Q000737:chemistry; D013696:Temperature; D053833:Wetlands
chemical_list: D012987:Soil; D002244:Carbon
keywords: 
  Q
  10
  ; carbon accumulation; climate extreme; drought; organic matter chemistry; plant productivity; soil enzymes; soil respiration