Mechanistic Root Water Uptake Functions Derived from Soil and Root Hydraulic Properties
(2023) ASA, CSSA, SSSA International Annual Meeting, St. Louis, MO. — Location: St. Louis, MO (29.October.2023)
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- Abstract
- Transpiration by plants is driven by an energy limited water demand or potential transpiration and limited by a maximal water supply that can be extracted from the soil by roots and transported to the transpiring canopy. The maximal supply rate depends on soil and root hydraulic properties and decreases when the soil dries out. If potential transpiration cannot be met by the maximal supply, stomata close and actual plant transpiration reduces to the maximal supply rate. The relation between actual transpiration and root water uptake distributions on the one hand, and potential transpiration, root architecture, root and soil hydraulic properties, and water distribution in the root zone on the other, can be predicted using detailed models that resolve the 3D flow from soil to root segments and within root segments to the canopy. However, such simulations are computationally very expensive, and we developed approaches to scale them up to 1D models. Still, the non-linear soil conductances around root segments require an iterative solution making simulations with upscaled 1D models also computationally expensive. Therefore, in analogy with currently used approaches, we developed functions that calculate root water uptake directly from soil water potentials and potential transpiration and that can be implemented in soil water flow models or in crop models easily. These functions were derived using approximations of the flow equations in the soil-root system and represent both soil and root hydraulic properties. Using this mechanistic derivation, we recovered some properties of currently used functions but also found important differences. The root water uptake functions depend on the soil and plant hydraulic properties and are not fixed functions of the plant or crop type but change over time together with the root system development.
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Citations
Vanderborght, J., Schnepf, A., Leitner, D., Couvreur, V., & Javaux, M. (2023). Mechanistic Root Water Uptake Functions Derived from Soil and Root Hydraulic Properties. ASA, CSSA, SSSA International Annual Meeting, St. Louis, MO., St. Louis, MO. https://hdl.handle.net/2078.5/240529