title: Global change could amplify fire effects on soil greenhouse gas emissions.
abstract: BACKGROUND
  Little is known about the combined impacts of global environmental changes and ecological disturbances on ecosystem functioning, even though such combined impacts might play critical roles in shaping ecosystem processes that can in turn feed back to climate change, such as soil emissions of greenhouse gases.
  
  
  RESULTS
  We took advantage of an accidental, low-severity wildfire that burned part of a long-term global change experiment to investigate the interactive effects of a fire disturbance and increases in CO(2) concentration, precipitation and nitrogen supply on soil nitrous oxide (N(2)O) emissions in a grassland ecosystem. We examined the responses of soil N(2)O emissions, as well as the responses of the two main microbial processes contributing to soil N(2)O production--nitrification and denitrification--and of their main drivers. We show that the fire disturbance greatly increased soil N(2)O emissions over a three-year period, and that elevated CO(2) and enhanced nitrogen supply amplified fire effects on soil N(2)O emissions: emissions increased by a factor of two with fire alone and by a factor of six under the combined influence of fire, elevated CO(2) and nitrogen. We also provide evidence that this response was caused by increased microbial denitrification, resulting from increased soil moisture and soil carbon and nitrogen availability in the burned and fertilized plots.
  
  
  CONCLUSIONS
  Our results indicate that the combined effects of fire and global environmental changes can exceed their effects in isolation, thereby creating unexpected feedbacks to soil greenhouse gas emissions. These findings highlight the need to further explore the impacts of ecological disturbances on ecosystem functioning in the context of global change if we wish to be able to model future soil greenhouse gas emissions with greater confidence.
authors.affiliation: Laboratoire Ecologie, Systématique et Evolution, UMR 8079 Université Paris-Sud 11/CNRS/AgroParisTech, Université Paris-Sud 11, Orsay, France. audrey.niboyet@grignon.inra.fr
authors.forename: Audrey
authors.initials: A
authors.lastname: Niboyet
authors.forename: Jamie R
authors.initials: JR
authors.lastname: Brown
authors.forename: Paul
authors.initials: P
authors.lastname: Dijkstra
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Blankinship
authors.forename: Paul W
authors.initials: PW
authors.lastname: Leadley
authors.forename: Xavier
authors.initials: X
authors.lastname: Le Roux
authors.forename: Laure
authors.initials: L
authors.lastname: Barthes
authors.forename: Romain L
authors.initials: RL
authors.lastname: Barnard
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Field
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Hungate
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry; D011232:Chemical Precipitation; D058440:Denitrification; D005390:Fires; D017752:Greenhouse Effect; D038622:Internationality; D009584:Nitrogen / Q000737:chemistry; D009609:Nitrous Oxide / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013997:Time Factors
chemical_list: D012987:Soil; D002245:Carbon Dioxide; D009609:Nitrous Oxide; D009584:Nitrogen