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Advanced spectrometry on vegetation types and assessment of structural effects on the vegetation spectrum

High resolution spectral measurements have been carried out on selected vegetation types with different biochemical content to study the optical properties and to establish a spectral signature database. 120 samples were collected, representative of both agricultural and nonagricultural vegetation types. Spectral reflectance and transmittance measurements were performed on single and stacked leaves. The samples were then dried and the spectral measurements were performed again. The dried samples were then sent for chemical analysis to 2 different laboratories. The results of the first series of analysis concerned the relative concentration of biochemical components such as lignin, cellulose, starch, water and nitrogen. This is one of the most comprehensive data sets which has ever been established for remote sensing purposes involving the spectral properties of vegetation and its biochemical components. First comparisons of the spectral signatures with the chemical analyses show some promising correlations especially with the spectral measurements made on dry samples. A new European goniometric facility has been installed and tested. This instrument allows a light source and a detector to be independently positioned anywhere on a 2 m radius hemisphere centred on the target and thereby to perform bidirectional measurements. The control software allows the full programming of an experiment, the graphical visualization of the geometry and the interface to a dedicated data base for the experimental results. A 2 stream radiative transfer model has been developed to investigate different absorption features in the reflectance spectrum of leaves and canopies. The investigation was focussed in the spectral window of 1.65 to 1.76 um thought to be a signature of lignin. It was concluded that the 1.7 um residual does show a systematic relation with the vegetation cover type.

Reported by

Joint Research Centre, Ispra
21020 Ispra
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