Biomass assessment in the Cameroon savanna using ALOS PALSAR data

Abstract

In this paper, ALOS PALSAR data have been used to map above ground biomass (AGB) in savanna ecosystems in Cameroon. The study has been motivated by the need to have estimates of carbon in African savannas. The L-band PALSAR mosaic data are suitable for the retrieval of savanna biomass (typically less than 100Mg.ha−1) at national and continental scales. The retrieval methods have been developed using the following steps a) collection of in situ data and estimate of AGB and its uncertainties, b) pre-processing of SAR data, with an emphasis on the reduction of uncertainties due to speckle, while preserving the SAR resolution (25m), c) development of a regression model with a reduced number of fitting parameters. The methodology is developed in a representative study area where in situ data are collected, using standard PALSAR Fine Beam Dual polarisation data, and d) pixel-to-pixel mapping of AGB over 259 228km2 of Cameroon savanna using PALSAR mosaic data. The dense tropical forest has been masked using the GlobCover 2009 land cover map. A value of AGB and its uncertainty has been assigned to each pixel. The results indicate a total AGB of 1.25±0.04Pg or 0.63±0.02PgC of above-ground carbon in the Cameroon savanna.