title: In situ measurement of CO2 and water vapour isotopic compositions at a forest site using mid-infrared laser absorption spectroscopy.
abstract: We conducted continuous, high time-resolution measurements of CO2 and water vapour isotopologues ((16)O(12)C(16)O, (16)O(13)C(16)O and (18)O(12)C(16)O for CO2, and H2(18)O for water vapour) in a red pine forest at the foot of Mt. Fuji for 9 days from the end of July 2010 using in situ absorption laser spectroscopy. The δ(18)O values in water vapour were estimated using the δ(2)H-δ(18)O relationship. At a scale of several days, the temporal variations in δ(18)O-CO2 and δ(18)O-H2O are similar. The orders of the daily Keeling plots are almost identical. A possible reason for the similar behaviour of δ(18)O-CO2 and δ(18)O-H2O is considered to be that the air masses with different water vapour isotopic ratios moved into the forest, and changed the atmosphere of the forest. A significant correlation was observed between δ(18)O-CO2 and δ(13)C-CO2 values at nighttime (r(2)≈0.9) due to mixing between soil (and/or leaf) respiration and tropospheric CO2. The ratios of the discrimination coefficients (Δa/Δ) for oxygen (Δa) and carbon (Δ) isotopes during photosynthesis were estimated in the range of 0.7-1.2 from the daytime correlations between δ(18)O-CO2 and δ(13)C-CO2 values.
authors.affiliation: a Institute for Space-Earth Environmental Research, Nagoya University , Nagoya , Japan.|b Department of Natural and Environmental Science , Teikyo University of Science , Uenohara , Japan.
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Wada
authors.affiliation: a Institute for Space-Earth Environmental Research, Nagoya University , Nagoya , Japan.|c Graduate School of Science , Nagoya University , Nagoya , Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Matsumi
authors.affiliation: d Department of Meteorological Environment, Forestry and Forest Products Research Institute , Tsukuba , Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Takanashi
authors.affiliation: d Department of Meteorological Environment, Forestry and Forest Products Research Institute , Tsukuba , Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Nakai
authors.affiliation: a Institute for Space-Earth Environmental Research, Nagoya University , Nagoya , Japan.|c Graduate School of Science , Nagoya University , Nagoya , Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Nakayama
authors.affiliation: c Graduate School of Science , Nagoya University , Nagoya , Japan.
authors.forename: Mai
authors.initials: M
authors.lastname: Ouchi
authors.affiliation: a Institute for Space-Earth Environmental Research, Nagoya University , Nagoya , Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hiyama
authors.affiliation: e Institute of Low Temperature Science , Hokkaido University , Sapporo , Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Fujiyoshi
authors.affiliation: f Mount Fuji Research Institute , Fujiyoshida , Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
authors.affiliation: g Graduate School of Environmental Studies , Nagoya University , Nagoya , Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Kurita
authors.affiliation: h Ishikawa National College of Technology , Tsubata , Japan.
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Muramoto
authors.affiliation: i Agro-Meteorology Division, National Institute of Agro-Environmental Sciences , Tsukuba , Japan.
authors.forename: Naomi
authors.initials: N
authors.lastname: Kodama
mesh_terms: D002245:Carbon Dioxide / Q000032:analysis*; D065928:Forests; D007554:Isotopes / Q000032:analysis*; D007834:Lasers; D013057:Spectrum Analysis / Q000379:methods*; D013227:Steam
chemical_list: D007554:Isotopes; D013227:Steam; D002245:Carbon Dioxide
keywords: Carbon-13; discrimination coefficient; hydrogen-2; forest; isotope ecology; isotope measurement methods and equipment; isotopologues; laser spectroscopy; oxygen-18; temporal variations; water vapour