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| Titel |
Topography induced spatial variations in diurnal cycles of assimilation and latent heat of Mediterranean forest |
| VerfasserIn |
C. Tol, A. J. Dolman, M. J. Waterloo, K. Raspor |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 4, no. 1 ; Nr. 4, no. 1 (2007-02-22), S.137-154 |
| Datensatznummer |
250001505
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| Publikation (Nr.) |
 copernicus.org/bg-4-137-2007.pdf |
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| Zusammenfassung |
| The aim of this study is to explain topography induced spatial
variations in the diurnal cycles of assimilation and latent heat of
Mediterranean forest. Spatial variations of the fluxes are caused by
variations in weather conditions and in vegetation characteristics.
Weather conditions reflect short-term effects of climate, whereas
vegetation characteristics, through adaptation and acclimation,
long-term effects of climate. In this study measurements of plant
physiology and weather conditions are used to explain observed
differences in the fluxes. A model is used to study which part of
the differences in the fluxes is caused by weather conditions and
which part by vegetation characteristics. Data were collected at
four experimental sub-Mediterranean deciduous forest plots in a
heterogeneous terrain with contrasting aspect, soil water
availability, humidity and temperature. We used a sun-shade model to
scale fluxes from leaf to canopy, and calculated the canopy energy
balance. Parameter values were derived from measurements of light
interception, leaf chamber photosynthesis, leaf nitrogen content and
13C isotope discrimination in leaf material. Leaf nitrogen
content is a measure of photosynthetic capacity, and 13C
isotope discrimination of water use efficiency. For validation,
sap-flux based measurements of transpiration were used. The model
predicted diurnal cycles of transpiration and stomatal conductance,
both their magnitudes and differences in afternoon stomatal closure
between slopes of different aspect within the confidence interval of
the validation data. Weather conditions mainly responsible for the
shape of the diurnal cycles, and vegetation parameters for the
magnitude of the fluxes. Although the data do not allow for a
quantification of the two effects, the differences in vegetation
parameters and weather among the plots and the sensitivity of the
fluxes to them suggest that the diurnal cycles were more strongly
affected by spatial variations in vegetation parameters than by
meteorological variables. This indicates that topography induced
variations in vegetation parameters are of equal importance to the
fluxes as topography induced variations in radiation, humidity and
temperature. |
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