title: Isotopomer and isotopologue signatures of N2O produced in alpine ecosystems on the Qinghai-Tibetan Plateau.
abstract: BACKGROUND
  Static-chamber flux measurements have suggested that one of the world's largest grasslands, the Qinghai-Tibetan Plateau (QTP), is a potential source of nitrous oxide (N2O), a major greenhouse gas. However, production and consumption pathways of N2O have not been identified by in situ field measurements.
  
  
  METHODS
  Ratios of N2O isotopomers ((14)N(15)N(16)O and (15)N(14)N(16)O) and an isotopologue ((14)N(14)N(18)O) with respect to (14)N(14)N(16)O in the atmosphere, static chambers, and soils were measured by gas chromatography and mass spectrometry in the summer of 2005 and the following winter of 2006 at three typical alpine ecosystems: alpine meadow, alpine shrub, and alpine wetland, on the QTP, China.
  
  
  RESULTS
  Site preference (SP) values of soil-emitted N2 O were estimated as 33.7‰ and 30.1‰ for alpine meadow and shrub, respectively, suggesting larger contributions by fungal denitrification, than by bacterial denitrification and nitrifier-denitrification, to N2 O production. Statistical analysis of the relationship between SP and δ(15)N(bulk) values indicated that in alpine meadow, shrub, and wetland sites fungal denitrification contributed 40.7%, 40.0%, and 23.2% to gross N2O production and the produced N2O was reduced by 87.6%, 82.9%, and 92.7%, respectively.
  
  
  CONCLUSIONS
  The combined measurements of N2O concentration, flux, and isotopomeric signatures provide a robust estimation of N2O circulation dynamics in alpine ecosystems on the QTP, which would contribute to the development of ecosystem nitrogen cycle model.
authors.affiliation: Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokohama, Kanagawa, Japan. tomomichi.kato@lsce.ipsl.fr
authors.forename: Tomomichi
authors.initials: T
authors.lastname: Kato
authors.forename: Sakae
authors.initials: S
authors.lastname: Toyoda
authors.forename: Naohiro
authors.initials: N
authors.lastname: Yoshida
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Tang
authors.forename: Eitaro
authors.initials: E
authors.lastname: Wada
mesh_terms: D000531:Altitude; D001272:Atmosphere / Q000032:analysis; D002681:China; D017753:Ecosystem; D004784:Environmental Monitoring; D008401:Gas Chromatography-Mass Spectrometry; D009569:Nitric Oxide / Q000737:chemistry*; D009587:Nitrogen Isotopes / Q000032:analysis
chemical_list: D009587:Nitrogen Isotopes; D009569:Nitric Oxide