Eddy covariance measurements of the dual-isotope composition of evapotranspiration

Braden-Behrens, Jelka; Markwitz, Christian; Knohl, Alexander

doi:10.1016/j.agrformet.2019.01.035

Cited by 17 publications

(27 citation statements)

References 75 publications

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“…Inc.,San Jose, USA) to measure the water vapor mole fraction C H2O and its stable isotopic compositions δ 18 O v and δD v at 44 m height above the forest floor. The measurement frequency is 2 Hz (Braden-Behrens et al, 2019). The used analyzer is an off-axis integrated-cavity output spectrometer in the near infrared, i.e.…”

Section: Stable Isotope Measurements Of δ H2omentioning

confidence: 99%

“…Aemisegger et al, 2012;Los Gatos Research Inc., 2012). We customized this calibration unit to enable calibration at the analyzer's flow rate of 4.2 slpm over a broad mole fraction range (see Braden-Behrens et al, 2019).…”

Section: Stable Isotope Measurements Of δ H2omentioning

confidence: 99%

“…We combined the 20 Hz anemometer measurements with the 2 Hz measurements of δ 18 O v and δD v to calculate the magnitude and the isotopic composition of ET using the eddy covariance software EddyPro®, version 6.2.0 (LiCor Biosciences, 2016). Further specification of this setup such as tubing material, tube heating, flow rates and the different data processing settings are described by Braden-Behrens et al (2019). In brief, the tubing to the 2 Hz-HF-WVIA was made of PTFE (teflon) and heated to avoid condensation.…”

Section: Eddy Covariance Measurements Of δ Etmentioning

confidence: 99%

“…The flow rates in the main tubes were chosen to guaranty turbulent conditions within the tubes upstream of the analyzer. Data processing includes double rotation and block averaging, spike removal, correction for instrument separation, as well as spectral corrections in the high frequency and low frequency range (see Braden-Behrens et al, 2019). Additionally to the stable isotope eddy covariance measurements, the meteorological tower is also equipped with a standard closed path CO 2 and H 2 O v analyzer (LI-6262 LiCor Inc., Lincoln, USA).…”

Section: Eddy Covariance Measurements Of δ Etmentioning

confidence: 99%

“…We quantify potential effects of ET on the isotopic composition of the atmosphere, by calculating isoforcing, based on EC measurements of the magnitude and the isotopic composition of ET (described in Braden-Behrens et al, 2019). Isoforcing (see e.g.…”

Section: Calculation Of Isoforcingmentioning

confidence: 99%

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Drivers of the variability of the isotopic composition of water vapor in the surface boundary layer

Braden-Behrens

Siebicke

Knohl

2020

Preprint

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Abstract. Measurements of the isotopic composition of water vapor, δv, as well as measurements of the isotopic composition of evaporation and transpiration provide valuable insights in the hydrological cycle. Here we present measurements of δv in the surface boundary layer (SBL) in combination with eddy covariance (EC) measurements of the isotopic composition of evapotranspiration δET for both δD as well as δ18O over a full growing season above a managed beech forest in central Germany. Based on direct measurements of isoforcing IF and the height h of the planetary boundary layer (PBL), we provide an estimate of isoforcing-related changes in δv, revealing the influence of local evapotranspiration (ET) on δv. At seasonal time scales we find no evidence for a dominant control of δv by local ET. Rayleigh distillation could at most explain 35 % of the observed variability and we did not find indications for the influence of entrainment at seasonal time scales. Instead, we obtain a strong significant correlation (R2 ≈ 0.52; p

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Section: Stable Isotope Measurements Of δ H2omentioning

confidence: 99%

Section: Stable Isotope Measurements Of δ H2omentioning

confidence: 99%

Section: Eddy Covariance Measurements Of δ Etmentioning

confidence: 99%

Section: Eddy Covariance Measurements Of δ Etmentioning

confidence: 99%

Section: Calculation Of Isoforcingmentioning

confidence: 99%

See 3 more Smart Citations

Drivers of the variability of the isotopic composition of water vapor in the surface boundary layer

Braden-Behrens

Siebicke

Knohl

2020

Preprint

Self Cite

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Evapotranspiration partitioning through water stable isotopic measurements in a subtropical coniferous forest

Xing,

Wang,

Cai

et al. 2024

Ecohydrology

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Evapotranspiration (ET) partitioning distinguishes the soil evaporation (E) and plant transpiration (T) components and is crucial for understanding the land‐atmosphere interactions and ecosystem water budget. However, the mechanism and controls of ET partitioning for subtropical forests in heterogeneous environments remain poorly understood. Here, we present δ18O and δ2H of about 1,527 isotope samples including atmospheric water, soil and plant water during different seasons in 2 years of 2020–2021 from a coniferous forest across Southeast China. We used the isotopic mass balance of ecosystem water pools, the Craig‐Gordon model and the Keeling‐Plot method to partition T from ET (T/ET) and quantify the controls on T/ET. Results indicated that the uncertainty in the T/ET was principally from the soil water evaporation (δE) value, about 20–30 cm was found to be a reasonable evaporating front depth for estimating δE in this coniferous forest. T/ET presented a “U” shape diurnal pattern and varied from 66.7% to 89.9%. Isotope‐based T/ET in autumn with high temperatures and little rain was higher than those in the summer and winter seasons. Relative humidity (or vapour pressure deficit) dominated the diurnal T/ET variations (relative contributions of > 40%) in summer and autumn, while air temperature and soil water content were the main controls in winter. Our study also showed that δ18O‐derived T/ET was consistent with that of δ2H, although δ2H was found to be more stable in ET partitioning, the dual stable isotope approach should be employed in future studies for the uncertainties brought by samplings or measurements. The agreement between the isotope‐based T/ET and ET partitioning approach that uses eddy covariance and sap flux data was stronger at midday. These isotope‐inferred ET partitioning can inform land surface models and provide more insights into water management in subtropical forests.

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High‐resolution in situ stable isotope measurements reveal contrasting atmospheric vapour dynamics above different urban vegetation

Ring,

Tetzlaff,

Dubbert

et al. 2023

Hydrological Processes

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We monitored stable water isotopes in liquid precipitation and atmospheric water vapour (δv) using in situ cavity ring‐down spectroscopy (CRDS) over a 2 month period in an urban green space area in Berlin, Germany. Our aim was to better understand the origins of atmospheric moisture and its link to water partitioning under contrasting urban vegetation. δv was monitored at multiple heights (0.15, 2 and 10 m) in grassland and forest plots. The isotopic composition of δv above both land uses was highly dynamic and positively correlated with that of rainfall indicating the changing sources of atmospheric moisture. Further, the isotopic composition of δv was similar across most heights of the 10 m profiles and between the two plots indicating high aerodynamic mixing. Only at the surface at ~0.15 m height above the grassland δv showed significant differences, with more enrichment in heavy isotopes indicative of evaporative fractionation especially after rainfall events. Further, disequilibrium between δv and precipitation composition was evident during and right after rainfall events with more positive values (i.e., values of vapour higher than precipitation) in summer and negative values in winter, which probably results from higher evapotranspiration and more convective precipitation events in summer. Our work showed that it is technically feasible to produce continuous, longer‐term data on δv isotope composition in urban areas from in situ monitoring using CRDS, providing new insights into water cycling and partitioning across the critical zone of an urban green space in Central Europe. Such data have the potential to better constrain the isotopic interface between the atmosphere and the land surface and to thus, improve ecohydrological models that can resolve evapotranspiration fluxes.

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Eddy covariance measurements of the dual-isotope composition of evapotranspiration

Cited by 17 publications

References 75 publications

Drivers of the variability of the isotopic composition of water vapor in the surface boundary layer

Drivers of the variability of the isotopic composition of water vapor in the surface boundary layer

Evapotranspiration partitioning through water stable isotopic measurements in a subtropical coniferous forest

High‐resolution in situ stable isotope measurements reveal contrasting atmospheric vapour dynamics above different urban vegetation

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