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| Titel |
Ecohydrologic controls on vegetation density and evapotranspiration partitioning across the climatic gradients of the central United States |
| VerfasserIn |
J. P. Kochendorfer, J. A. Ramírez |
| 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 ; 14, no. 10 ; Nr. 14, no. 10 (2010-10-27), S.2121-2139 |
| Datensatznummer |
250012458
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| Publikation (Nr.) |
 copernicus.org/hess-14-2121-2010.pdf |
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| Zusammenfassung |
| The soil-water balance and plant water use are investigated over a domain
encompassing the central United States using the Statistical-Dynamical
Ecohydrology Model (SDEM). The seasonality in the model and its use of the
two-component Shuttleworth-Wallace canopy model allow for application of an
ecological optimality hypothesis in which vegetation density, in the form of
peak green leaf area index (LAI), is maximized, within upper and lower
bounds, such that, in a typical season, soil moisture in the latter half of
the growing season just reaches the point at which water stress is
experienced. Via a comparison to large-scale estimates of grassland
productivity, modeled-determined peak green LAI for these systems is seen to
be at least as accurate as the unaltered satellite-based observations on
which they are based. A related feature of the SDEM is its partitioning of
evapotranspiration into transpiration, evaporation from canopy interception,
and evaporation from the soil surface. That partitioning is significant for
the soil-water balance because the dynamics of the three processes are very
different. Surprising little dependence on climate and vegetation type is
found for the percentage of total evapotranspiration that is soil
evaporation, with most of the variation across the study region attributable
to soil texture and the resultant differences in vegetation density. While
empirical evidence suggests that soil evaporation in the forested regions of
the most humid part of the study region is somewhat overestimated, model
results are in excellent agreement with observations from croplands and
grasslands. The implication of model results for water-limited vegetation is
that the higher (lower) soil moisture content in wetter (drier) climates is
more-or-less completely offset by the greater (lesser) amount of energy
available at the soil surface. This contrasts with other modeling studies
which show a strong dependence of evapotranspiration partitioning on climate. |
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