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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/bg-2018-280
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2018-280
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 05 Jul 2018

Submitted as: research article | 05 Jul 2018

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The revised manuscript was not accepted.

A mechanistic model for electrical conduction in soil–root continuum: a virtual rhizotron study

Sathyanarayan Rao1, Félicien Meunier2, Solomon Ehosioke3, Nolwenn Lesparre4, Andreas Kemna5, Frédéric Nguyen3, Sarah Garré6, and Mathieu Javaux1,7 Sathyanarayan Rao et al.
  • 1Université catholique de Louvain, Earth and Life Institute-Environmental Sciences, Louvain- la-Neuve, Belgium
  • 2Computational and Applied Vegetation Ecology lab, Ghent University, Gent, Belgium
  • 3Applied Geophysics, Université de Liège, Chemin des Chevreuils 1, 4000 Liege, Belgium
  • 4Laboratoire d'Hydrologie et Géochimie de Strasbourg, University of Strasbourg/EOST/ENGEES, CNRS UMR 7517, 1 Rue Blessig, 67084 Strasbourg, France
  • 5Department of Geophysics, University of Bonn, Meckenheimer Allee 176, 53115 Bonn, Germany
  • 6Université de Liège, Gembloux Agro-Bio Tech, TERRA Research and Teaching Center, Passage des déportés 2, 5030 Gembloux, Belgium
  • 7Agrosphere, IBG3, Forschungszentrum Juelich GmbH, Germany

Abstract. Electrical Resistivity Tomography (ERT) has become an important tool to study soil water fluxes in cropped field. ERT results translates to water content via empirical pedophysical relations that take soil physical properties into account, usually ignoring the impact of roots. Studies shows high root dense soils behaves quite differently than less root dense soils in terms of bulk electrical conductivity. Yet, we do not completely understand the impact of root segments on the ERT measurements. In this numerical study, we coupled an electrical model with a plant-soil water flow model to investigate the impact of plant root growth and water uptake on the ERT virtual experiment. The electrical properties of roots were explicitly accounted in the finite element mesh and we obtained the electrical conductivities of root segments by conducting specific experiments on real maize plants. The contrast between electrical conductivity of roots and soil depends on factors such as root density, irrigation, root age, and root water uptake pattern. Root growth and water uptake processes thus affect this contrast together with the soil electrical properties. Model results indicate a non-negligible anisotropy in bulk electrical conductivity induced by root processes. We see a greater anisotropy in a sandy medium when compared to a loamy medium. We find that the water uptake process dominates the bulk electrical properties. The Gauss-Newton type ERT inversion of virtual rhizotron data demonstrate that, when root-soil electrical conductivity contrasts are high, it can lead to error in water content estimates since the electrical conductivity is partly due to root. Thus, incorporating the impact of root in the pedophysical relations is very important to interpret ERT results directly as water content.

Sathyanarayan Rao et al.
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Interactive discussion
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AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Sathyanarayan Rao et al.
Sathyanarayan Rao et al.
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Short summary
This paper illustrates the impact of electrical property of maize root segments on the Electrical Resistivity Tomography (ERT) inversion results with the help of numerical model. The model includes explicit root representation in the finite element mesh with root growth, transpiration and root water uptake. We show that, ignoring root segments could lead to wrong estimation of water content using ERT method.
This paper illustrates the impact of electrical property of maize root segments on the...
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