% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Kuppe:1022314,
      author       = {Kuppe, Christian W.},
      title        = {{R}hizosphere models and their application to resource
                      uptake efficiency},
      school       = {RWTH Aachen},
      type         = {Dissertation},
      publisher    = {RWTH Aachen University},
      reportid     = {FZJ-2024-01432},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2023},
      note         = {Dissertation, RWTH Aachen, 2023},
      abstract     = {The efficient acquisition of finite and plant
                      growth-limiting resources becomes increasingly important in
                      sustainable agriculture and crop production. The rhizosphere
                      as root-soil interface and its traits are critical for plant
                      nutrition. Thus, I aim at discovering traits and mechanisms
                      for efficient nutrient uptake via rhizosphere modeling.
                      Rhizosphere models are interdisciplinary. They build on soil
                      models and encompass a collective equation system of
                      biological, physical, and chemical concepts. Such concepts
                      and underlying assumptions are fundamental to simulation
                      results and their interpretation. Hence, in the first part
                      of the thesis, I comprehensively analyze how the rhizosphere
                      has been modeled so far. Nutrient uptake calculated from
                      rhizosphere models affects the entire plant. I compared
                      numerical methods for calculating uptake, since for root
                      architecture models with a large number of root segments,
                      each with its own soil conditions with a priori unknown
                      concentration profiles, such methods need to be reliable,
                      fast, and accurate. The hitherto de facto standard methods
                      for single ion transport in radial rhizosphere models,
                      Crank-Nicolson and explicit Euler, are not universally
                      applicable for the wide range of parameter values. I
                      recommend adaptive stiff or Runge-Kutta methods with
                      higher-order spatial discretizations. In the second part of
                      the thesis, I develop two novel models to simulate the
                      uptake of the essential nutrients, phosphorus (P) and
                      nitrogen (N). This mechanistic modeling addresses how plant
                      traits influence uptake efficiency. I explain how upland
                      rice can efficiently grow on strongly sorbing soils with low
                      plant-available P and how root-exudation of biological
                      nitrification inhibitors (BNIs) can facilitate N uptake
                      efficiency and reduce N loss to the environment. The
                      mechanisms behind efficient P uptake on strongly sorbing
                      soils, and the role of different root classes, were not well
                      understood. Fine lateral roots are metabolically low-cost
                      and make up a large proportion of the root system, but their
                      sole uptake strength is low. Models typically underestimated
                      P uptake, which restrained targeted trait selection.
                      However, the new P-pH model agrees with the observed plant
                      P-uptake. The model allows for fast- and slowly reacting P
                      depending on root-induced pH change, different root classes,
                      and root morphology. The pH value (in the initially acidic
                      soil) increases throughout the rhizosphere by acid-base
                      diffusion, forming a P solubilization zone around the root.
                      However, this solubilized P diffuses to the root too slowly.
                      The results of the data-driven modeling convey to breeders
                      the importance of solubilization and fine hairy lateral
                      roots as integrative phenotype, i.e. in combination with
                      other traits, because fine roots are most beneficial for P
                      uptake in the vicinity of thicker roots due to their greater
                      solubilization of P. BNIs have been suggested as strategy
                      for improving N uptake and reducing environmental N
                      pollution. Not all plants exude BNIs, and their importance
                      to plants is questionable. With the new N-BNI model, I
                      investigate the efficacy of BNIs and explain under which
                      conditions BNIs are beneficial. The benefit of nitrification
                      inhibition for uptake strongly depends on the availability
                      of soil N-forms. BNIs are only beneficial for plant-N uptake
                      when it is not impaired by lower nitrate production over the
                      growth period. If nitrate availability is low, nitrification
                      would be beneficial for uptake. The model indicates that the
                      same N uptake can be achieved with reduced fertilizer
                      application due to reduced nitrification and, therefore,
                      reduced N loss. As mode of action, the sensitivity analysis
                      suggests bactericidal exudates rather than bacteriostatic
                      ones. Selection for BNI exudation should be accompanied by
                      improved ammonium uptake. In conclusion, the rhizosphere
                      models in this thesis enabled the identification of traits
                      for P- and N-efficient plants. The results of the P-pH
                      modeling are already used by a plant breeder developing new
                      rice lines. Future studies on BNIs are required to consider
                      rhizosphere conditions since the ecological and
                      plant-physiological benefits of BNIs are distinct.},
      keywords     = {Hochschulschrift (Other) / Rhizosphere modeling ; nitrogen
                      ; nitrate ; ammonium ; N uptake ; phosphorus ; P uptake ;
                      soil pH ; phosphate ; solubilization ; upscaling ; BNI ;
                      radial solute transport; NUE; uptake efficiency ; bacteria ;
                      nitrification ; inhibition ; upland rice ; roots ; numerical
                      methods ; Wurzel ; N-Aufnahme ; Nitrifizierung ; P-Aufnahme
                      (Other)},
      cin          = {IBG-2 / IBG-1 / IBG-4},
      cid          = {I:(DE-Juel1)IBG-2-20101118 / I:(DE-Juel1)IBG-1-20101118 /
                      I:(DE-Juel1)IBG-4-20200403},
      pnm          = {2171 - Biological and environmental resources for
                      sustainable use (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2171},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2023-11292},
      url          = {https://juser.fz-juelich.de/record/1022314},
}