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Deriving seasonal dynamics in ecosystem properties of semi-arid savanna grasslands from in situ-based hyperspectral reflectance

Tagesson, T.; Fensholt, R.; Huber, S.; Horion, S.; Guiro, I.; Ehammer, A. and Ardö, Jonas LU (2015) In Biogeosciences 12(15). p.4621-4635
Abstract
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 (rho) 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... (More)
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 (rho) 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 (rho(412)) (FAPAR). The NDSI with the strongest correlation to (i) biomass combined rededge HCRF (rho(705)) with green HCRF (rho(587)), (ii) GPP combined wavelengths at the peak of green reflection (rho(518), rho(556)), (iii) LUE combined red (rho(688)) with blue HCRF (rho(436)), and (iv) FAPAR combined blue (rho(399)) and near-infrared (rho(1295)) wavelengths. NDSIs combining near infrared and shortwave infrared were strongly affected by solar zenith an-gles 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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biogeosciences
volume
12
issue
15
pages
4621 - 4635
publisher
Copernicus Publications
external identifiers
  • wos:000360003700005
  • scopus:84938723088
ISSN
1726-4189
DOI
10.5194/bg-12-4621-2015
language
English
LU publication?
yes
id
b31f5c39-6a0c-4180-9252-49e6ef16a089 (old id 7972379)
date added to LUP
2015-09-23 13:05:44
date last changed
2017-06-04 03:20:26
@article{b31f5c39-6a0c-4180-9252-49e6ef16a089,
  abstract     = {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 (rho) 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 (rho(412)) (FAPAR). The NDSI with the strongest correlation to (i) biomass combined rededge HCRF (rho(705)) with green HCRF (rho(587)), (ii) GPP combined wavelengths at the peak of green reflection (rho(518), rho(556)), (iii) LUE combined red (rho(688)) with blue HCRF (rho(436)), and (iv) FAPAR combined blue (rho(399)) and near-infrared (rho(1295)) wavelengths. NDSIs combining near infrared and shortwave infrared were strongly affected by solar zenith an-gles 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.},
  author       = {Tagesson, T. and Fensholt, R. and Huber, S. and Horion, S. and Guiro, I. and Ehammer, A. and Ardö, Jonas},
  issn         = {1726-4189},
  language     = {eng},
  number       = {15},
  pages        = {4621--4635},
  publisher    = {Copernicus Publications},
  series       = {Biogeosciences},
  title        = {Deriving seasonal dynamics in ecosystem properties of semi-arid savanna grasslands from in situ-based hyperspectral reflectance},
  url          = {http://dx.doi.org/10.5194/bg-12-4621-2015},
  volume       = {12},
  year         = {2015},
}