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| Titel |
Contribution of advection to the carbon budget measured by eddy covariance at a steep mountain slope forest in Switzerland |
| VerfasserIn |
S. Etzold, N. Buchmann, W. Eugster |
| 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 ; 7, no. 8 ; Nr. 7, no. 8 (2010-08-17), S.2461-2475 |
| Datensatznummer |
250004933
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| Publikation (Nr.) |
 copernicus.org/bg-7-2461-2010.pdf |
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| Zusammenfassung |
| We calculated the contribution of advection to the C budget measured by the
eddy covariance (EC) technique for a steep and forested mountain site
(CarboEurope site CH-Lae, Lägeren, Switzerland) during the growing
season 2007 (May to August). Thereby we followed two approaches: (1) the
physical correction of the EC data for directly measured advection terms and
(2) the u∗ filter approach that replaces periods with u∗ below a site-specific threshold with empirically modelled fluxes. We found
good agreement between the two approaches in terms of daily (linear
regression slope: 0.78 ± 0.04, intercept: 0.68 ± 0.29 μmol m−2 s−1, adj. R2=0.78) and seasonal sums of gross
fluxes (difference ≤ 12%), when using a u∗ threshold of
0.3 m s−1 and correcting EC for horizontal advection only.
Incorporating also vertical advection into the mass balance equation
resulted in unrealistic and highly erratic fluxes. However, on a daily basis
vertical advection cancelled out to nearly zero. The u∗ filter
seems to account primarily for respiration fluxes, which are mainly affected
by horizontal advection. We could confirm our corrections by a
cross-validation with independent approaches, such as soil respiration
chamber measurements, light curves and energy budget closure. Our results
show that flux measurements on steep sites with complex topography are
possible. Actually, sloping sites seem to have the advantage over flat sites
that advection measurements can be reduced to a simplified two-dimensional
measurement approach due to the two-dimensional characteristics of the wind
field at those sites. |
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