Comparing root water uptake profile estimations from an isotope-calibrated mechanistic model and a mixing model

  • Yamanaka Tsutomu
    Faculty of Life and Environmental Sciences, University of Tsukuba
  • Kimura Takeo
    Graduate School of Life and Environmental Sciences, University of Tsukuba
  • Sun Xinchao
    Institute of Surface-Earth System Science, Tianjin University, China
  • Kato Hiroaki
    Faculty of Life and Environmental Sciences, University of Tsukuba Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba
  • Onda Yuichi
    Faculty of Life and Environmental Sciences, University of Tsukuba Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba

抄録

<p>The root water uptake profile (RWUP) reflects a plant’s survival strategy and controls evapotranspiration and carbon fluxes. Despite its importance, there is still no reliable method for reconstructing this profile. In this study, we applied and compared two possible approaches to a case study in a conifer plantation: an isotope-calibrated mechanistic model and a mixing model with a bell-shaped approximation. Our results show that, after calibrating the hydrologically-active root density profile, the mechanistic model gave a good estimation of the xylem water isotope delta (δx); even though the measured root density was greater in shallower soils, water uptake occurred throughout the entire soil profile, with more uptake in deeper soils. The RWUPs estimated by the mixing model were different from those estimated by the mechanistic model and were unrealistic. However, when we constrained the minimum thickness of the water uptake zone, there was good agreement between the RWUPs from the two approaches. We can therefore conclude that the mechanistic model calibrated with isotopes gave better results, and that sole use of the mixing model is not recommended unless appropriate constraints are applied.</p>

収録刊行物

  • Hydrological Research Letters

    Hydrological Research Letters 11 (3), 161-167, 2017

    水文・水資源学会/日本地下水学会/日本水文科学会/陸水物理研究会

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