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| Titel |
Horizontal soil water potential heterogeneity: simplifying approaches for crop water dynamics models |
| VerfasserIn |
V. Couvreur, J. Vanderborght, L. Beff, M. Javaux |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 18, no. 5 ; Nr. 18, no. 5 (2014-05-12), S.1723-1743 |
| Datensatznummer |
250120354
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| Publikation (Nr.) |
 copernicus.org/hess-18-1723-2014.pdf |
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| Zusammenfassung |
| Soil water potential (SWP) is known to affect plant water status, and even
though observations demonstrate that SWP distribution around roots may limit
plant water availability, its horizontal heterogeneity within the root zone
is often neglected in hydrological models. As motive, using a horizontal
discretisation significantly larger than one centimetre is often essential
for computing time considerations, especially for large-scale hydrodynamics
models. In this paper, we simulate soil and root system hydrodynamics at the
centimetre scale and evaluate approaches to upscale variables and parameters
related to root water uptake (RWU) for two crop systems: a densely seeded
crop with an average uniform distribution of roots in the horizontal
direction (winter wheat) and a wide-row crop with lateral variations in root
density (maize). In a first approach, the upscaled water potential at
soil–root interfaces was assumed to equal the bulk SWP of the upscaled soil
element. Using this assumption, the 3-D high-resolution model could be
accurately upscaled to a 2-D model for maize and a 1-D model for wheat. The
accuracy of the upscaled models generally increased with soil hydraulic
conductivity, lateral homogeneity of root distribution, and low
transpiration rate. The link between horizontal upscaling and an implicit
assumption on soil water redistribution was demonstrated in quantitative
terms, and explained upscaling accuracy. In a second approach, the soil–root
interface water potential was estimated by using a constant rate analytical
solution of the axisymmetric soil water flow towards individual roots. In
addition to the theoretical model properties, effective properties were
tested in order to account for unfulfilled assumptions of the analytical
solution: non-uniform lateral root distributions and transient RWU rates.
Significant improvements were however only noticed for winter wheat, for
which the first approach was already satisfying. This study confirms that
the use of 1-D spatial discretisation to represent soil–plant water dynamics
is a worthy choice for densely seeded crops. For wide-row crops, e.g. maize,
further theoretical developments that better account for horizontal SWP
heterogeneity might be needed in order to properly predict soil–plant
hydrodynamics in 1-D. |
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