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@ARTICLE{Couvreur:873311,
      author       = {Couvreur, Valentin and Rothfuss, Youri and Meunier,
                      Félicien and Bariac, Thierry and Biron, Philippe and
                      Durand, Jean-Louis and Richard, Patricia and Javaux,
                      Mathieu},
      title        = {{D}isentangling temporal and population variability in
                      plant root water uptake from stable isotopic analysis: a
                      labeling study},
      journal      = {Hydrology and earth system sciences discussions},
      volume       = {},
      issn         = {1812-2108},
      address      = {Katlenburg-Lindau},
      publisher    = {Soc.},
      reportid     = {FZJ-2020-00629},
      pages        = {543},
      year         = {2019},
      abstract     = {<p><strong>Abstract.</strong> Isotopic labeling techniques
                      have the potential to minimize the uncertainty of plant root
                      water uptake (RWU) profiles estimated through multi-source
                      (statistical) modeling, by artificially enhancing soil water
                      isotopic gradient. Furthermore, physical models can account
                      for hydrodynamic constraints to RWU if simultaneous soil and
                      plant water status data is available.</p> <p>In this study,
                      a population of tall fescue (<i>Festuca arundinacae</i> cv
                      Soni) was grown in a macro-rhizotron setup under
                      semi-controlled conditions to monitor such variables for a
                      34-hours long period following the oxygen stable isotopic
                      (<sup>18</sup>O) labeling of deep soil water. Aboveground
                      variables included tiller and leaf water oxygen isotopic
                      compositions as well as leaf water potential
                      $(<i>\&#968;</i><sub>leaf</sub>),$ relative humidity, and
                      transpiration rate. Belowground profiles of root length
                      density (RLD), soil water content and isotopic composition
                      were also sampled. While there were strong correlations
                      between hydraulic variables as well as between isotopic
                      variables, the experimental results underlined the
                      discrepancy between variations of hydraulic and isotopic
                      variables.</p> <p>In order to dissect the problem, we
                      reproduced both types of observations with a one-dimensional
                      physical model of water flow in the soil-plant domain, for
                      60 different realistic RLD profiles. While simulated
                      $<i>\&#968;</i><sub>leaf</sub>$ followed clear temporal
                      variations with little differences across plants as if they
                      were $\&#8220;on$ board of the same $rollercoaster\&#8221;,$
                      simulated $<i>\&#948;</i><sub>tiller</sub>$ values within
                      the plant population were rather heterogeneous
                      $(\&#8220;swarm-like\&#8221;)$ with relatively little
                      temporal variation and a strong sensitivity to rooting
                      depth. The physical model thus suggested that the
                      discrepancy between isotopic and hydraulic observations was
                      logical, as the variability captured by the former was
                      spatial and may not correlate with the temporal dynamics of
                      the latter.</p> <p>For comparison purposes a Bayesian
                      statistical model was also used to simulate RWU. While they
                      predicted relatively similar cumulative RWU profiles, the
                      physical model could differentiate spatial from temporal
                      dynamics of the isotopic signature, and supported that the
                      local increase of soil water content and formation of a peak
                      of labelled water observed overnight were due to hydraulic
                      lift.</p>},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255)},
      pid          = {G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.5194/hess-2019-543},
      url          = {https://juser.fz-juelich.de/record/873311},
}