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LWFBrook90.jl—Including Stable Water Isotopes in a Soil Vegetation Atmosphere Transport Model to Constrain Vertical Root Water Uptake Dynamics

F. Bernhard,J. Knighton,S. Seeger,P. Waldner,K. Meusburger

Published 2025 in Journal of Advances in Modeling Earth Systems

ABSTRACT

In water‐limited ecosystems, soil water availability plays a pivotal role in determining the stress levels experienced by vegetation. Understanding the vertical distribution of roots and root water uptake (RWU) is essential for accurately predicting drought conditions using Soil Vegetation Atmosphere Transport (SVAT) models. However, quantifying RWU in environments poses a considerable challenge. Here, stable isotope signatures in water offer a promising avenue for inferring RWU. They can effectively trace the movement of precipitation through soil layers into trees. Combining isotopes with precipitation and soil moisture content enables inferring relative and absolute contributions of soil layers to RWU, thereby providing added benefit over mixing models. In this study, we extended the SVAT model LWF‐Brook90 with transport of stable isotopes in water. The model was validated using measurements from a forest monitoring site and further test cases. Across calibration scenarios combining observed hydrometric and isotopic state variables as calibration targets, we compared model accuracy, predictive uncertainty, and parameter equifinality. Our results demonstrated that the model accurately reproduced observations and that overall model accuracy and precision could be improved by a multi‐objective calibration approach combining isotopic and hydrometric time series. Isotopes specifically constrained parameters linked to RWU and preferential infiltration. Including isotopes reduced uncertainty in parameter estimates and model predictions and reduced parameter equifinality. Combining isotope mixing with SVAT models holds the potential to significantly enhance our mechanistic understanding of water fluxes in water‐limited ecosystems, including dynamics of root water uptake, facilitating more accurate predictions of vegetation responses to changing environmental conditions.

PUBLICATION RECORD

  • Publication year

    2025

  • Venue

    Journal of Advances in Modeling Earth Systems

  • Publication date

    2025-11-01

  • Fields of study

    Not labeled

  • Identifiers
    DOI 10.1029/2024MS004445
  • External record

    Open on Semantic Scholar

  • Source metadata

    Semantic Scholar

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