During daylight hours, the isotope composition of leaf water generally approximates steady-state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady-state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange systems we evaluated the isotope composition of tra...

Pakistan experiences a variety of climates ranging from a small humid patch in the north to extremely arid southern plains. Evapotranspiration is not a directly measurable element among agrometeorological parameters influencing crop growth and development. Many empirical and semi-empirical methods for estimation of crop evapotranspiration exist and are being used by individual scientists and re...

Evaporation of water from the guard cell wall concentrates apoplastic solutes. We hypothesize that this phenomenon provides two mechanisms for responding to high transpiration rates. First, apoplastic abscisic acid is concentrated in the guard cell wall. Second, by accumulating in the guard cell wall, apoplastic sucrose (Suc) provides a direct osmotic feedback to guard cells. As a means of test...

Chen, Wei-Chih. Ph.D., Purdue University, December 2014. Assessment of Irrigation Use on Crop Yield and Water Supplies in the Midwestern U.S. Major Professor: Keith Cherkauer. Climate plays an important role in many aspects of hydrological and agricultural systems. Temperature and precipitation are usually the main forcing inputs for hydrological and agricultural simulations, while wind effect ...

The Project for Intercomparison of Land-surface Parameterization Schemes (PILPS) has shown that different land surface models (LSMs) driven by the same meteorological forcing can produce markedly different surface energy and water budgets, even when certain critical aspects of the LSMs (vegetation cover, albedo, turbulent drag coefficient, and snowcover) are carefully controlled. To help explai...

Simulations of above-canopy water vapor and CO2 fluxes were calculated by the USGF linked model of canopy gas exchange and subsurface processes for the 1996-1997 winter wheat season at the AmeriFlux Wheat Site, Oklahoma. Soil surface CO2 flux plus canopy gas exchange and transpiration plus soil evaporation modeled the CO2 and water vapor fluxes, respectively. Parameter values for net photosynth...

Even though knowing the contributions of transpiration (T), soil and open water evaporation (E), and interception (I) to terrestrial evapotranspiration (ET = T+ E+ I) is crucial for understanding the hydrological cycle and its connection to ecological processes, the fraction of T is unattainable by traditional measurement techniques over large scales. Previously reported global mean T/(E+ T+ I)...

A reliable thermal-derived method for spatially and temporally continuous latent heat flux (LE) estimates is vital agricultural water resource management. In this study, we proposed a novel three-source LE model (TSLEM) derived by all-weather thermal infrared (TIR) land surface temperature (LST) to generate all-sky daily in mainland China. approach, was partitioned into the energy fluxes from c...

Changes in the 2 H and 18 O of atmospheric water vapour provide information for integrating aspects of gas exchange within forest canopies. In this study, we show that diurnal fluctuations in the oxygen isotope ratio ( δ 18 O) as high as 4‰ were observed for water vapour ( δ 18 O vp ) above and within an old-growth coniferous forest in the Pacific Northwest region of the United States. Values o...