An assessment of canopy chemistry with AVIRIS-A case study in the Landes Forest, South West France

Studies the capability of airborne (AVIRIS) and laboratory high spectral resolution information for assessing the chemical composition (lignin, nitrogen, cellulose, ...) of a pine forest (Les Landes, SW France). Simultaneously with AVIRIS acquisition, an atmospheric profile and a forest vegetation sampling for chemical and laboratory spectral analyses, were collected. Predictive relationships between concentrations of nitrogen (r=97%), ligin (r=89%), cellulose (r=83%), and reflectances of pre-treated pine needles were determined through stepwise regression analyses. A methodology was designed to assess their extrapolation to remotely acquired spectrometric data: (1) geometric and atmospheric corrections, (2) registration within a biophysical data base (LAI, biomass, ...), and (3) comparative statistical analysis of laboratory and airborne spectrometric information. Nitrogen and cellulose concentrations predicted with canopy reflectances were relatively correlated with actual concentrations (74% and 79% respectively); poorer results were obtained for lignin (55%). Atmospheric corrections did not improve correlations. It was attempted to improve these results while taking into account the influence of the canopy structure and total quantity of chemical compounds. Predictive equations base on laboratory measurements were applied to reflectances of pine needles that were computed through the inversion of two reflectance models. This approach only improved correlations for lignin (74%). Finally, chemical concentrations in the studied area were mapped in order to provide spatial information suitable for ecosystem models