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| Titel |
Surface fluxes and water balance of spatially varying vegetation within a small mountainous headwater catchment |
| VerfasserIn |
G. N. Flerchinger, D. Marks, M. L. Reba, Q. Yu, M. S. Seyfried |
| 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. 6 ; Nr. 14, no. 6 (2010-06-17), S.965-978 |
| Datensatznummer |
250012336
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| Publikation (Nr.) |
 copernicus.org/hess-14-965-2010.pdf |
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| Zusammenfassung |
| Precipitation variability and complex topography often create a mosaic of vegetation
communities in mountainous headwater catchments, creating a challenge for measuring and
interpreting energy and mass fluxes. Understanding the role of these communities in
modulating energy, water and carbon fluxes is critical to quantifying the variability in
energy, carbon, and water balances across landscapes. The focus of this paper was: (1) to
demonstrate the utility of eddy covariance (EC) systems in estimating the evapotranspiration
component of the water balance of complex headwater mountain catchments; and (2) to compare
and contrast the seasonal surface energy and carbon fluxes across a headwater catchment
characterized by large variability in precipitation and vegetation cover. Eddy covariance
systems were used to measure surface fluxes over sagebrush (Artemesia arbuscula and
Artemesia tridentada vaseyana), aspen (Populus tremuloides) and the
understory of grasses and forbs beneath the aspen canopy. Peak leaf area index of the
sagebrush, aspen, and aspen understory was 0.77, 1.35, and 1.20, respectively. The sagebrush
and aspen canopies were subject to similar meteorological forces, while the understory of
the aspen was sheltered from the wind. Missing periods of measured data were common and made
it necessary to extrapolate measured fluxes to the missing periods using a combination of
measured and simulated data. Estimated cumulative evapotranspiratation from the sagebrush,
aspen trees, and aspen understory were 384 mm, 314 mm and 185 mm. A water balance of the
catchment indicated that of the 699 mm of areal average precipitation, 421 mm was lost to
evapotranspiration, and 254 mm of streamflow was measured from the catchment; water balance
closure for the catchment was within 22 mm. Fluxes of latent heat and carbon for all sites
were minimal through the winter. Growing season fluxes of latent heat and carbon were
consistently higher above the aspen canopy than from the other sites. While growing season
carbon fluxes were very similar for the sagebrush and aspen understory, latent heat fluxes
for the sagebrush were consistently higher, likely because it is more exposed to the
wind. Sensible heat flux from the aspen tended to be slightly less than the sagebrush site
during the growing season when the leaves were actively transpiring, but exceeded that from
the sagebrush in May, September and October when the net radiation was not offset by
evaporative cooling in the aspen. Results from this study demonstrate the utility of EC
systems in closing the water balance of headwater mountain catchments and illustrate the
influence of vegetation on the spatial variability of surface fluxes across mountainous
rangeland landscapes. |
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