Polarimetric Alos/Palsar-2 data for retrieving aboveground biomass of secondary forest in the Brazilian Amazon

Secondary forests (SFs) are one of the major carbon sink in the Neotropics due to the rapid carbon assimilating in their aboveground biomass (AGB). However, the accurate contribution of the SFs to the carbon cycle is a great challenge because of the uncertainty in AGB estimates. In this context, the main objective of this work is to explore polarimetric Alos/Palsar-2 data from to model AGB in the SFs of the Central Amazon, Amazonas State. Forest inventory was conducted in 2014 with the measured of 23 field plots. Multiple linear regression analysis was performed to select the best model by corrected AIC w and validated by leave-one-out bootstrapping method. The best fitted model has six parameters and explained 65% of the aboveground biomass variability. The prediction error was calculated to be RMSEP = 8.8 ± 2.98 Mg.ha -1 (8.75%). The main polarimetric attributes in the model were those direct related to multiple scattering mechanisms as the Shannon Entropy and the volumetric mechanism of Bhattacharya decomposition; and those related to increase in double-bounce as the co-polarization ratio (VV/HH) resulted of soil-trunk interactions. Such models are intended to improve accuracy for mapping SFs AGB in often cloudy environments as in the Brazilian Amazon.