Dew water isotopic ratios and their relationships to ecosystem water pools and fluxes in a cropland and a grassland in China |
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Authors: | Wen Xue-Fa Lee Xuhui Sun Xiao-Min Wang Jian-Lin Hu Zhong-Min Li Sheng-Gong Yu Gui-Rui |
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Institution: | (1) Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China;(2) School of Forestry and Environmental Studies, Yale University, New Haven, CT 06510, USA;(3) Qingdao Agricultural University, Qingdao, 266109, China |
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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 18O 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%). |
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