title: Dew water isotopic ratios and their relationships to ecosystem water pools and fluxes in a cropland and a grassland in China.
abstract: Dew formation has the potential to modulate the spatial and temporal variations of isotopic contents of atmospheric water vapor, oxygen and carbon dioxide. The goal of this paper is to improve our understanding of the isotopic interactions between dew water and ecosystem water pools and fluxes through two field experiments in a wheat/maize cropland and in a short steppe grassland in China. Measurements were made during 94 dew events of the D and (18)O compositions of dew, atmospheric vapor, leaf, xylem and soil water, and the whole ecosystem water flux. Our results demonstrate that the equilibrium fractionation played a dominant role over the kinetic fractionation in controlling the dew water isotopic compositions. A significant correlation between the isotopic compositions of leaf water and dew water suggests a large role of top-down exchange with atmospheric vapor controlling the leaf water turnover at night. According to the isotopic labeling, dew water consisted of a downward flux of water vapor from above the canopy (98%) and upward fluxes originated from soil evaporation and transpiration of the leaves in the lower canopy (2%).
authors.affiliation: Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China. wenxf@igsnrr.ac.cn
authors.forename: Xue-Fa
authors.initials: XF
authors.lastname: Wen
authors.forename: Xuhui
authors.initials: X
authors.lastname: Lee
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: Sun
authors.forename: Jian-Lin
authors.initials: JL
authors.lastname: Wang
authors.forename: Zhong-Min
authors.initials: ZM
authors.lastname: Hu
authors.forename: Sheng-Gong
authors.initials: SG
authors.lastname: Li
authors.forename: Gui-Rui
authors.initials: GR
authors.lastname: Yu
mesh_terms: D002681:China; D003903:Deuterium; D017753:Ecosystem; D006813:Humidity; D010103:Oxygen Isotopes; D018515:Plant Leaves; D006109:Poaceae; D012621:Seasons; D012987:Soil; D013227:Steam; D014908:Triticum; D014867:Water / Q000737:chemistry* / Q000378:metabolism; D052584:Xylem / Q000737:chemistry; D003313:Zea mays
chemical_list: D010103:Oxygen Isotopes; D012987:Soil; D013227:Steam; D014867:Water; D003903:Deuterium