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| Titel |
Multiresolution quantification of deciduousness in West-Central African forests |
| VerfasserIn |
G. Viennois, N. Barbier, I. Fabre, P. Couteron |
| 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 ; 10, no. 11 ; Nr. 10, no. 11 (2013-11-04), S.6957-6967 |
| Datensatznummer |
250085394
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| Publikation (Nr.) |
 copernicus.org/bg-10-6957-2013.pdf |
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| Zusammenfassung |
The characterization of leaf phenology in tropical forests is of major
importance for forest typology as well as to improve our understanding of
earth–atmosphere–climate interactions or biogeochemical cycles. The
availability of satellite optical data with a high temporal resolution has
permitted the identification of unexpected phenological cycles, particularly
over the Amazon region. A primary issue in these studies is the relationship
between the optical reflectance of pixels of 1 km or more in size and ground
information of limited spatial extent. In this paper, we demonstrate that
optical data with high to very-high spatial resolution can help bridge this
scale gap by providing snapshots of the canopy that allow discernment of the
leaf-phenological stage of trees and the proportions of leaved crowns within
the canopy. We also propose applications for broad-scale forest
characterization and mapping in West-Central Africa over an area of
141 000 km2.
Eleven years of the Moderate Resolution Imaging Spectroradiometer (MODIS)
Enhanced Vegetation Index (EVI) data were averaged over the wet and dry
seasons to provide a data set of optimal radiometric quality at a spatial
resolution of 250 m. Sample areas covered at a very-high (GeoEye) and high
(SPOT-5) spatial resolution were used to identify forest types and to
quantify the proportion of leaved trees in the canopy. The dry-season EVI
was positively correlated with the proportion of leaved trees in the canopy.
This relationship allowed the conversion of EVI into canopy deciduousness at
the regional level. On this basis, ecologically important forest types could
be mapped, including young secondary, open Marantaceae, Gilbertiodendron dewevrei and swamp forests. We show
that in West-Central African forests, a large share of the variability in
canopy reflectance, as captured by the EVI, is due to variation in the
proportion of leaved trees in the upper canopy, thereby opening new
perspectives for biodiversity and carbon-cycle applications. |
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