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| Titel |
Deriving seasonal dynamics in ecosystem properties of semi-arid savanna grasslands from in situ-based hyperspectral reflectance |
| VerfasserIn |
T. Tagesson, R. Fensholt, S. Huber, S. Horion, I. Guiro, A. Ehammer, J. Ardö |
| 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 ; 12, no. 15 ; Nr. 12, no. 15 (2015-08-05), S.4621-4635 |
| Datensatznummer |
250118049
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| Publikation (Nr.) |
 copernicus.org/bg-12-4621-2015.pdf |
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| Zusammenfassung |
| This paper investigates how hyperspectral reflectance (between 350 and 1800 nm) can be used to infer ecosystem properties for a semi-arid savanna
grassland in West Africa using a unique in situ-based multi-angular data set
of hemispherical conical reflectance factor (HCRF) measurements.
Relationships between seasonal dynamics in hyperspectral HCRF and ecosystem
properties (biomass, gross primary productivity (GPP), light use efficiency
(LUE), and fraction of photosynthetically active radiation absorbed by
vegetation (FAPAR)) were analysed. HCRF data (ρ) were used to study the
relationship between normalised difference spectral indices (NDSIs) and the
measured ecosystem properties. Finally, the effects of variable sun sensor
viewing geometry on different NDSI wavelength combinations were analysed. The
wavelengths with the strongest correlation to seasonal dynamics in ecosystem
properties were shortwave infrared (biomass), the peak absorption band for
chlorophyll a and b (at 682 nm) (GPP), the oxygen A band at 761 nm used
for estimating chlorophyll fluorescence (GPP and LUE), and blue wavelengths
(ρ412) (FAPAR). The NDSI with the strongest correlation to (i)
biomass combined red-edge HCRF (ρ705) with green HCRF (ρ587),
(ii) GPP combined wavelengths at the peak of green reflection (ρ518,
ρ556), (iii) LUE combined red (ρ688) with blue HCRF
(ρ436), and (iv) FAPAR combined blue (ρ399) and near-infrared
(ρ1295) wavelengths. NDSIs combining near infrared and shortwave
infrared were strongly affected by solar zenith angles and sensor viewing
geometry, as were many combinations of visible wavelengths. This study
provides analyses based upon novel multi-angular hyperspectral data for
validation of Earth-observation-based properties of semi-arid ecosystems, as
well as insights for designing spectral characteristics of future sensors for
ecosystem monitoring. |
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