A Simplified 3D Radiative Transfer Approach for the Retrieval of Chemical and Structural Properties of Individual Tree Crowns from Hyperspectral Data

摘要

In this work, we used hyperspectral remote sensing and a simplified three-dimensional radiative transfer approach to retrieve structural and chemical properties of individual tree crowns (ITCs) from a tropical forest area. First, a Look-Up-Table of simulated ITC reflectance was built by randomly varying parameters of the DART and PROSPECT models. Then, simulated and experimental reflectance of ITCs were compared in terms of spectral similarity. Finally, model parameters that yielded simulations spectrally similar to experimental data were related to sub-pixel fractions and narrow-band vegetation indices computed from the hyperspectral images. DART canopy structural parameters were related to the proportion of non-photosynthetic vegetation (NPV) (R^{2=0.65), green photosynthetic vegetation (GV) (R2=0.72) and shade (R2=0.34) estimated within ITCs. PROSPECT parameters describing foliar chemical traits such as Chlorophyll a+b (Cab) and Carotenoids (C_xc) were related to the ratio of TCARI/OSAVI (R2=0.77) indices and to the simple ratio between reflectance at 515 nm and 570 nm (R₅₁₅/R₅₇₀) (R2=0.42), respectively.}