| Quantifying forest biomass is of crucial importance for estimating carbon fluxes on the regional and global scale in climate change studies. Significant relationships have already been established between radar mean intensity and forest biomass, but these relationships show a reduced sensitivity to biomass variations for mature stands (about 80 t.ha-1 and more). On the contrary, recent studies have shown that image texture is significantly related to biomass even for mature stands for a temperate, monospecific, even-aged forest of which the biomass is 140 t.ha-1 at its highest point. The present paper aims at extending these observations to tropical forests which represent a large terrestrial biomass pool with values higher than 450 t.ha-1. Radar images were acquired during the TropiSAR experiment in 2009, which took place over a tropical rain forest located in French Guyana with the use of SETHI ONERA airborne instrument. Three sets of treatments applied to 15 forest stands provided biomass values from 260 to 470 t.ha-1 and permanent plots of 6.25 ha each were mapped and regularly measured. Homogeneous patches were selected inside each of the 15 experimental stands. Statistical features were then derived for each patch: a) from gray level statistics; b) from the statistics of pixel pairs on the basis of the gray level co-occurrence matrix. It is shown that linear relationships between texture features and forest biomass are heavily influenced by stand structure and the local topography and soil of the experimental plots. |
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