Spatial heterogeneity in vegetation canopies and remote sensing of absorbed photosynthetically active radiation: A modeling study

A large number of previous studies have investigated the possibility of estimating absorbed photosynthetically active radiation (PAR) from spectral reflectance of plant canopies. An important factor not considered in these studies is the case of horizontally heterogeneous plant stands where the grou...

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Bibliographic Details
Published in:Remote sensing of environment 1992-08, Vol.41 (2), p.85-103
Main Authors: Asrar, G., Myneni, R.B., Choudhury, B.J.
Format: Article
Language:English
Subjects:
Animal, plant and microbial ecology
Biological and medical sciences
CANOPY
CLUMP LEAF AREA INDEX
COUVERT
CUBIERTA DE COPAS
ENERGIA SOLAR
ENERGIE SOLAIRE
Energy absorption
ENVIRONMENTAL FACTORS
FACTEUR DU MILIEU
FACTORES AMBIENTALES
FOTOSINTESIS
Fundamental and applied biological sciences. Psychology
General aspects. Techniques
HORIZONTALLY HETEROGENEOUS
LEAF AREA
LEAF AREA INDEX
Mathematical models
MODELE
MODELOS
Natural resources exploration
OPTICAL PROPERTIES
PHOTOSYNTHESE
PHOTOSYNTHESIS
PROPIEDADES OPTICAS
PROPRIETE OPTIQUE
REFLECTANCE
REMOTE SENSING
Sensitivity analysis
SOLAR ENERGY
SOLAR RADIATION
SPATIAL DISTRIBUTION
Spectrum analysis
SUPERFICIE FOLIAR
SURFACE FOLIAIRE
TELEDETECCION
TELEDETECTION
Teledetection and vegetation maps
THREE-DIMENSIONAL RADIATIVE TRANSFER MODEL
VEGETACION
VEGETATION
VEGETATION TYPES
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Summary:A large number of previous studies have investigated the possibility of estimating absorbed photosynthetically active radiation (PAR) from spectral reflectance of plant canopies. An important factor not considered in these studies is the case of horizontally heterogeneous plant stands where the ground cover is usually less than 100%. We investigated the relationship between spectral indices and fraction of absorbed PAR in horizontally heterogeneous vegetation canopies with the aid of a three-dimensional radiative transfer model. Canopy reflection at optical wavelengths and PAR absorption was simulated using this model. The errors incurred in using a 1D model for calculating the radiation regime of spatially heterogeneous canopies are shown to be significant. Our analysis indicates that the leaf area index of a canopy is less of an instructive parameter than ground cover and clump leaf area index for these canopies. The relationship between normalized difference vegetation index and fraction of absorbed PAR is found to be almost linear and independent of spatial heterogeneity. However, this relationship is sensitive to the reflectance of the soil or background.
ISSN:0034-4257
1879-0704
DOI:10.1016/0034-4257(92)90070-Z