δ2H isotopic flux partitioning of evapotranspiration over a grass field following a water pulse and subsequent dry down

摘要: The partitioning of surface vapor flux (FET) into evaporation (FE) and transpiration (FT) is theoretically possible because distinct differences in end-member stable isotope composition. In this study, we combine high-frequency laser spectroscopy with eddy covariance techniques to critically evaluate FET over a grass field during 15 day experiment. Following the application 30 mm water pulse, green coverage at study site increased from 0 10% ground area after 6 days then began senesce. Using partitioning, as fraction total 0% 40% green-up phase, which ratio decreased while exhibiting hysteresis respect coverage. Daily daytime leaf-level gas exchange measurements compare well daily averages (RMSE = 0.0018 g m−2 s−1). Overall average FT was 29%, where uncertainties Keeling plot intercepts composition resulted an uncertainty ∼5% our isotopic FET. Flux-variance similarity partially consistent isotope-based approach, divergence occurring rainfall when stressed. Over diurnal cycle, local meteorological conditions, particularly net radiation relative humidity, are shown control partitioning. At longer time scales, leaf available soil FT/FET. Finally, demonstrate feasibility combining flux-variance theory estimate use efficiency landscape scale.