Analysis of forest biomass variation in the Amazon and its' influence on the response of P-band SAR polarimetric data João Roberto dos Santos Luciana Spinelli de Araujo, Corina da Costa Freitas, Luciana de Souza Soler, Fábio Furlan Gama, Luciano Vieira Dutra National Institute for Space Research — INPE * ABSTRACT Radar images are presently being used in association with optical remote sensing data to characterize the different processes of land use in Brazilian Amazon region. Considering the current development in remote sensing techniques for estimating forest biomass, where L, X and C band images have their limitations, it was recently accomplished a scientific airbome mission with image polarimetric P-band imagery acquisition at lower Rio Tapajós region, Brazil. This study analyses the biomass variation of the primary forest and secondary succession and it's influence on the response of backscatter values in the P-band polarimetric images. The start of this study was the understanding of the behavior of the structural variables of the vegetation cover (measured during the field survey) and its'correlation with the backscatter data obtained from P im -, Pay - and Pvv - band data. A statistical regression model was used to verify the relationship between biomass (estimate by different allometric equations) and P-band polarimetric data. Based on the regression equation that best fits the data sets, a biomass map was elaborated. *This was done through the segmentation of the backscatter image, using Caesar 3.0 rwseg algorithm (based on the successive edge detecting and region growing procedures). with the of each resulting segment was converted into biomass values by the best fit function. The final goal of this P-band experiment is to improve the regional inventory and monitoring biomass dynamics, as well as landscape changes, due to human action in Amazon. Keywords: biomass, tropical rain forest, secondary succession, P-band data, inventory, Amazon 1. TNTRODUCTION The Brazilian Amazon region occupies 5 million Km 2 and approximately 76% of this area is covered by different forest types. Studies more recent have shown that the conversion of forest areas through deforestation, burning and implantation of agricultural activities, and specially catde raising, have risen to 600,000 Km 2 in this region. The mean rate of gross deforestation was estimated in15,800 km 2/year (INPE, 2002), although this value fluctuates widely due to such factors as the effectiveness of governmental policy in the control of forest resources. From the total area of forest destroyed in Amazon region, around 15% refers to abandoned land (non-productive), which is occupiedby several stages of secondary succession. Another activity of degradation is the selective logging without a management plans, whose results of this practices are being estimated to be of 2,500 km 2/year in the terra firme forest areas (Santos et al., 2002a). The human actions in the tropical forest have been conducted without planning, causing significant environmental damage (fragmentation, loss of biodiversity and reduction of sou l fertilit ). The decision makers on environmental issues use remote sensing data as an important tool to support the inventory and control plans of Amazon region. Furthermore, such datasets are also used as a support for the estimation of carbon emission/re-absorption in the global climate analysis, due to large scale changes of land use/land cover. New scientific studies with SAR data are being performed, in complement with a long time experience on the use of data from different optical sensor systems, in order to improve the knowledge on the characteristics and dynamics of forest. In this frame, the objective of this study is to analyze the biomass variation of primar)/ forest and sccondary succession in the P -band airborne SA polarimetrie data, derived from certain structural characteristics. *1NPE: Av. do Astronautas, 1758, CEP: 12227 -010,São José dos Campos (SP)-Brasil; phone: +55 (12) 3945 6427; fax.: +55 (12) 3945 6449; e-mail: jroberto@ltid.inpe.br. 252 Remote Sensing for Agriculture, Ecosystems, and Hydrology IV, Manfred Owe, Guido D'Urso, Leonidas Toulios, Editors, Proceedings of SPIE Vol. 4879 (2003) (0 2003 SPIE • 0277-786X/03/$15.00