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@ARTICLE{Couvreur:877588,
      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: when
                      rooting depth matters in labeling studies},
      journal      = {Hydrology and earth system sciences},
      volume       = {24},
      number       = {6},
      issn         = {1607-7938},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2020-02310},
      pages        = {3057 - 3075},
      year         = {2020},
      abstract     = {Isotopic labeling techniques have the potential to minimize
                      the uncertainty of plant root water uptake (RWU) profiles
                      estimated using multisource (statistical) modeling by
                      artificially enhancing the soil water isotopic gradient. On
                      the other end of the modeling continuum, physical models can
                      account for hydrodynamic constraints to RWU if simultaneous
                      soil and plant water status data are available.In this
                      study, a population of tall fescue (Festuca arundinacea cv.
                      Soni) was grown in amacro-rhizotron and monitored for a
                      34 h long period following the oxygen stable isotopic
                      (18O) labeling of deep soil water. Aboveground variables
                      included tiller and leaf water oxygen isotopic compositions
                      (δtiller and δleaf, respectively) as well as leaf water
                      potential (ψleaf), 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 partial disconnect
                      between the temporal dynamics of hydraulic and isotopic
                      variables.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 ψleaf
                      followed clear temporal variations with small differences
                      across plants, as if they were “onboard the same roller
                      coaster”, simulated δtiller values within the plant
                      population were rather heterogeneous (“swarm-like”) with
                      relatively little temporal variation and a strong
                      sensitivity to rooting depth. Thus, the physical model
                      explained the discrepancy between isotopic and hydraulic
                      observations: the variability captured by δtiller reflected
                      the spatial heterogeneity in the rooting depth in the soil
                      region influenced by the labeling and may not correlate with
                      the temporal dynamics of ψleaf. In other words, ψleaf
                      varied in time with transpiration rate, while δtiller
                      varied across plants with rooting depth.For comparison
                      purposes, a Bayesian statistical model was also used to
                      simulate RWU. While it predicted relatively similar
                      cumulative RWU profiles, the physical model could
                      differentiate the spatial from the temporal dynamics of the
                      isotopic composition. An important difference between the
                      two types of RWU models was the ability of the physical
                      model to simulate the occurrence of hydraulic lift in order
                      to explain concomitant increases in the soil water content
                      and the isotopic composition observed overnight above the
                      soil labeling region.},
      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},
      UT           = {WOS:000541483600002},
      doi          = {10.5194/hess-24-3057-2020},
      url          = {https://juser.fz-juelich.de/record/877588},
}