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| Titel |
An optimality-based model of the coupled soil moisture and root dynamics |
| VerfasserIn |
S. J. Schymanski, M. Sivapalan  , M. L. Roderick, J. Beringer, L. B. Hutley |
| 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 ; 12, no. 3 ; Nr. 12, no. 3 (2008-06-17), S.913-932 |
| Datensatznummer |
250010665
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| Publikation (Nr.) |
 copernicus.org/hess-12-913-2008.pdf |
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| Zusammenfassung |
| The main processes determining soil moisture dynamics are infiltration,
percolation, evaporation and root water uptake. Modelling soil moisture
dynamics therefore requires an interdisciplinary approach that links
hydrological, atmospheric and biological processes. Previous approaches treat
either root water uptake rates or root distributions and transpiration rates
as given, and calculate the soil moisture dynamics based on the theory of
flow in unsaturated media. The present study introduces a different approach
to linking soil water and vegetation dynamics, based on vegetation
optimality. Assuming that plants have evolved mechanisms that minimise costs
related to the maintenance of the root system while meeting their demand for
water, we develop a model that dynamically adjusts the vertical root
distribution in the soil profile to meet this objective. The model was used
to compute the soil moisture dynamics, root water uptake and fine root
respiration in a tropical savanna over 12 months, and the results were
compared with observations at the site and with a model based on a fixed root
distribution. The optimality-based model reproduced the main features of the
observations such as a shift of roots from the shallow soil in the wet season
to the deeper soil in the dry season and substantial root water uptake during
the dry season. At the same time, simulated fine root respiration rates never
exceeded the upper envelope determined by the observed soil respiration. The
model based on a fixed root distribution, in contrast, failed to explain the
magnitude of water use during parts of the dry season and largely
over-estimated root respiration rates. The observed surface soil moisture
dynamics were also better reproduced by the optimality-based model than the
model based on a prescribed root distribution. The optimality-based approach
has the potential to reduce the number of unknowns in a model (e.g. the
vertical root distribution), which makes it a valuable alternative to more
empirically-based approaches, especially for simulating possible responses to
environmental change. |
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