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@PHDTHESIS{Huber:202647,
      author       = {Huber, Katrin},
      title        = {{T}he role of soil heterogeneity on field scale
                      evapotranspiration: 3{D} integrative modellingand upscaling
                      of root water uptake},
      volume       = {263},
      school       = {Univ. Bonn},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2015-04837},
      isbn         = {978-3-95806-057-9},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {xii, 128},
      year         = {2015},
      note         = {Dissertation, Univ. Bonn, 2014},
      abstract     = {Background and Motivation: Hydrological models mainly rely
                      on empirical functions to describe rootwater uptake.
                      However, in case of water limitation due to either scarce or
                      heterogeneously distributedsoil water, plants have developed
                      strategies to adapt. One short-term strategy is the
                      regulation ofstomatal aperture either by plant hydraulics or
                      phyto-hormones. The latter are thought to act as a kindof
                      sensor for dry soil. It can be assumed that hormones are
                      produced locally in single root segments asfunction of low
                      root water potentials. After being transported with the
                      xylem stream they becomeeffective in stomatal closure.
                      Long-term adaptation strategies are mostly related to
                      changes in carbonallocation within the plant and result in
                      growth adaptations. Both strategies often remain
                      insufficientlyrepresented in hydrological models.Methods:
                      R-SWMS, a mechanistic soil and root water flow model that
                      operates at the scale of a singleroot system was used to
                      conduct a variety of virtual experiments. The model
                      simulates threedimensional water flow through the soil, to,
                      and within the roots. It was extended by a module toaccount
                      for additional hormonal signalling, subsequently testing its
                      influence in virtual split-rootexperiments. In a next step,
                      direct mathematical relationships that link effective soil
                      water potentialand transpiration were derived. Considering
                      the long-term adaptation strategies, the numerical modelwas
                      modified to incorporate measured dynamic root
                      architectures.Results: Measured hormone concentrations in
                      the leaves and some phenomena, like e.g. oscillations
                      instomatal aperture, were reproduced by the model. The
                      direct relationships between soil water potentialand
                      transpiration showed that the stomatal behaviour depends on
                      the underlying control and itsparameterization. Experimental
                      data, visualizing root systems over a 30 day growth period,
                      wereobtained from UFZ Halle, Germany, by CT scans. This
                      dataset showed that plants grown underpermanently limited
                      water supply were considerably smaller with correspondingly
                      less total wateruptake compared to plants with initially
                      unrestricted water resources. In combination with
                      thenumerical model, the flow dynamics in the soil-root
                      system were resolved. The predicted location ofroot water
                      uptake was found to be different from the measured zone of
                      water depletion.Conclusion: The implementation of
                      bio-physical relationships into a mechanistic root soil
                      modelresulted in a powerful tool to identify key processes
                      for plant water use in agricultural environments.This work
                      provided new direct relationships between the effective soil
                      water potential andtranspiration rate in case stomata are
                      controlled by hormones. In combination with an
                      experimentaldataset it gave new insights into water pathways
                      within the soil-plant continuum.},
      cin          = {IBG-3},
      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)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2015071401},
      url          = {https://juser.fz-juelich.de/record/202647},
}