Dew water isotopic ratios and their relationships to ecosystem water pools and fluxes in a cropland and a grassland in China

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%).

[1]  J. Ehleringer,et al.  Vegetation effects on the isotope composition of oxygen in atmospheric CO2 , 1993, Nature.

[2]  H. Griffiths,et al.  Diurnal variation of Δ13CO2, ΔC18O16O and evaporative site enrichment of δH218O in Piper aduncum under field conditions in Trinidad , 1998 .

[3]  R. Scott,et al.  Partitioning overstory and understory evapotranspiration in a semiarid savanna woodland from the isotopic composition of water vapor , 2003 .

[4]  E. Malek,et al.  Dew contribution to the annual water balances in semi-arid desert valleys , 1999 .

[5]  J. R. Garratt,et al.  On the contribution of atmospheric moisture to dew formation , 1988 .

[6]  X. Lee,et al.  Continuous measurement of water vapor D/H and 18 O/ 16 O isotope ratios in the atmosphere , 2008 .

[7]  L. Merlivat.  Molecular diffusivities of H2 16O,HD16O, and H2 18O in gases , 1978 .

[8]  A. Dai.  Recent climatology, variability, and trends in global surface humidity , 2006 .

[9]  X. Lee,et al.  Temporal variations of the 18O/16O signal of the whole‐canopy transpiration in a temperate forest , 2007 .

[10]  M. Baskaran,et al.  Handbook of Environmental Isotope Geochemistry: Vol I , 2012 .

[11]  Joost C. B. Hoedjes,et al.  SMOSREX: A long term field campaign experiment for soil moisture and land surface processes remote sensing , 2006 .

[12]  Peter W. Thorne,et al.  Attribution of observed surface humidity changes to human influence , 2007, Nature.

[13]  X. Lee,et al.  deltaO of water vapour, evapotranspiration and the sites of leaf water evaporation in a soybean canopy. , 2008, Plant, cell & environment.

[14]  X. Lee,et al.  Canopy‐scale kinetic fractionation of atmospheric carbon dioxide and water vapor isotopes , 2009 .

[15]  H. Craig,et al.  Deuterium and oxygen 18 variations in the ocean and marine atmosphere , 1965 .

[16]  P. Berbigier,et al.  Partitioning net ecosystem carbon exchange into net assimilation and respiration with canopy‐scale isotopic measurements: An error propagation analysis with 13CO2 and CO18O data , 2004 .

[17]  Stephen S. O. Burgess,et al.  Hydraulic redistribution in three Amazonian trees , 2005, Oecologia.

[18]  J. Jouzel.  Chapter 2 – ISOTOPES IN CLOUD PHYSICS: MULTIPHASE AND MULTISTAGE CONDENSATION PROCESSES , 1986 .

[19]  N. Ingraham.  Chapter 3 – Isotopic Variations in Precipitation , 1998 .

[20]  X. Lee,et al.  In Situ Measurement of the Water Vapor 18O/16O Isotope Ratio for Atmospheric and Ecological Applications , 2005 .

[21]  Nurit Agam,et al.  Dew formation and water vapor adsorption in semi-arid environments : A review , 2006 .

[22]  Thomas J. Jackson,et al.  Observations of dew amount using in situ and satellite measurements in an agricultural landscape , 2009 .

[23]  M. Stewart.  Stable isotope fractionation due to evaporation and isotopic exchange of falling waterdrops: Applications to atmospheric processes and evaporation of lakes , 1975 .

[24]  John M. Baker,et al.  Direct measurement of biosphere‐atmosphere isotopic CO2 exchange using the eddy covariance technique , 2008 .

[25]  C. Leuschner,et al.  Vertical patterns and duration of surface wetness in an old-growth tropical montane forest, Indonesia , 2007 .

[26]  D. Randall,et al.  A three‐dimensional synthesis study of δ18O in atmospheric CO2 1. Surface fluxes , 1997 .

[27]  S. Rambal,et al.  Evaluating water fluxes of field-grown alfalfa from diurnal observations of natural isotope concentrations, energy budget and ecophysiological parameters , 1989 .

[28]  T. Dawson.  Hydraulic lift and water use by plants: implications for water balance, performance and plant-plant interactions , 1993, Oecologia.

[29]  F. Bosveld,et al.  Dew Formation, Eddy-Correlation Latent Heat Fluxes, and the Surface Energy Imbalance at Cabauw During Stable Conditions , 2010 .

[30]  N. Agama,et al.  Dew formation and water vapor adsorption in semi-arid environments — A review , 2006 .

[31]  Salah Er-Raki,et al.  Evapotranspiration components determined by stable isotope, sap flow and eddy covariance techniques , 2004 .

[32]  H. Griffiths,et al.  Toward a plant‐based proxy for the isotope ratio of atmospheric water vapor , 2007 .

[33]  X. Lee,et al.  A modeling investigation of canopy-air oxygen isotopic exchange of water vapor and carbon dioxide in a soybean field , 2010 .

[34]  樋口 浩和,et al.  Water Dynamics in Mango (Mangifera indica L.) Fruit during the Young and Mature Fruit Seasons as Measured by the Stem Heat Balance Method , 2006 .

[35]  K. Richards.  Observation and simulation of dew in rural and urban environments , 2004 .

[36]  S. P. S. Arya,et al.  Introduction to micrometeorology , 1988 .

[37]  J. Richards,et al.  Update on Nighttime Stomatal Conductance in Plants Nighttime Stomatal Conductance and Transpiration in C3 and C4 Plants 1[W] , 2006 .

[38]  X. Lee,et al.  Determining the Oxygen Isotope Composition of Evapotranspiration Using Eddy Covariance , 2010 .

[39]  M. Majoube.  Fractionnement en oxygène 18 et en deutérium entre l’eau et sa vapeur , 1971 .

[40]  X. Lee,et al.  Transition of stable isotope ratios of leaf water under simulated dew formation. , 2011, Plant, cell & environment.

[41]  H. Higuchi,et al.  Reverse flow in roots of Sesbania rostrata measured using the constant power heat balance method , 1999 .

[42]  H. Griffiths,et al.  Diurnal variation of ∆ 13 CO 2 , ∆ C 18 O 16 O and evaporative site enrichment of δ H 218 O in Piper aduncum under field conditions in , 2022 .

[43]  D. Yakir,et al.  Stable isotope composition of water in desert plants , 2007, Plant and Soil.

[44]  G. Farquhar,et al.  On the isotopic composition of leaf water in the non-steady state. , 2005, Functional plant biology : FPB.

[45]  H. Neumann,et al.  Ozone deposition onto a deciduous forest during dry and wet conditions , 1992 .

[46]  X. Lee,et al.  Water vapor and precipitation isotope ratios in Beijing, China , 2010 .

[47]  浩和 樋口,et al.  茎熱収支法によって測定した幼果期と成熟期におけるマンゴー（Mangifera indica L.）果実の水分動態 , 2006 .

[48]  T. Sowers,et al.  The Dole Effect and its variations during the last 130,000 years as measured in the Vostok Ice Core , 1994 .

[49]  X. Roux,et al.  Spatial partitioning of the soil water resource between grass and shrub components in a West African humid savanna , 1995, Oecologia.

[50]  P. Ciais,et al.  A comprehensive global three‐dimensional model of δ18O in atmospheric CO2: 1. Validation of surface processes , 2003 .

[51]  L. Sternberg,et al.  The use of stable isotopes to study ecosystem gas exchange , 2000, Oecologia.

[52]  J. McDonnell,et al.  Isotope tracers in catchment hydrology , 1998 .

[53]  K. Snyder,et al.  lose water at night , 2003 .

[54]  D. Yakir,et al.  Influence of Carbonic Anhydrase Activity in Terrestrial Vegetation on the 18O Content of Atmospheric CO2 , 2001, Science.

[55]  E. Maier‐Reimer,et al.  A model of the Earth's Dole effect , 2004 .