Inversion of a radiative transfer model for estimating vegetation LAI and chlorophyll in a heterogeneous grassland

Radiative transfer models have seldom been applied for studying heterogeneous grassland canopies. Here, the potential of radiative transfer modeling to predict LAI and leaf and canopy chlorophyll contents in a heterogeneous Mediterranean grassland is investigated. The widely used PROSAIL model was i...

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Vydáno v:	Remote sensing of environment Ročník 112; číslo 5; s. 2592 - 2604
Hlavní autoři:	Darvishzadeh, Roshanak, Skidmore, Andrew, Schlerf, Martin, Atzberger, Clement
Médium:	Journal Article
Jazyk:	angličtina
Vydáno:	New York, NY Elsevier Inc 15.05.2008 Elsevier Science
Témata:	ancillary information Animal, plant and microbial ecology Applied geophysics Biological and medical sciences canopy biophysical variables Canopy chlorophyll Earth sciences Earth, ocean, space Exact sciences and technology Fundamental and applied biological sciences. Psychology General aspects. Techniques Grassland Hyperspectral Internal geophysics LAI Leaf chlorophyll leaf-area index LUT Model inversion neural-network optical-properties precision agriculture Radiative transfer model reflectance data remote-sensing data retrieval satellite data Teledetection and vegetation maps MED Grassland Radiative transfer model Model inversion LAI Hyperspectral LUT Canopy chlorophyll Leaf chlorophyll Spectroradiometry stratification radiative transfer vegetation Spectral data grasslands LA1 models inverse problem Prediction chlorophyll Plant leaf utilization heterogeneity Measurement in situ Content Canopy(vegetation) Reflectance Leaf area index
ISSN:	0034-4257, 1879-0704
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Popis
Shrnutí:	Radiative transfer models have seldom been applied for studying heterogeneous grassland canopies. Here, the potential of radiative transfer modeling to predict LAI and leaf and canopy chlorophyll contents in a heterogeneous Mediterranean grassland is investigated. The widely used PROSAIL model was inverted with canopy spectral reflectance measurements by means of a look-up table (LUT). Canopy spectral measurements were acquired in the field using a GER 3700 spectroradiometer, along with simultaneous in situ measurements of LAI and leaf chlorophyll content. We tested the impact of using multiple solutions, stratification (according to species richness), and spectral subsetting on parameter retrieval. To assess the performance of the model inversion, the normalized RMSE and R2 between independent in situ measurements and estimated parameters were used. Of the three investigated plant characteristics, canopy chlorophyll content was estimated with the highest accuracy (R2=0.70, NRMSE=0.18). Leaf chlorophyll content, on the other hand, could not be estimated with acceptable accuracy, while LAI was estimated with intermediate accuracy (R2=0.59, NRMSE=0.18). When only sample plots with up to two species were considered (n=107), the estimation accuracy for all investigated variables (LAI, canopy chlorophyll content and leaf chlorophyll content) increased (NRMSE=0.14, 0.16, 0.19, respectively). This shows the limits of the PROSAIL radiative transfer model in the case of very heterogeneous conditions. We also found that a carefully selected spectral subset contains sufficient information for a successful model inversion. Our results confirm the potential of model inversion for estimating vegetation biophysical parameters at the canopy scale in (moderately) heterogeneous grasslands using hyperspectral measurements.
Bibliografie:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0034-4257 1879-0704
DOI:	10.1016/j.rse.2007.12.003