Yearly Variation of Acacia Plantation Forests Obtained by Polarimetric Analysis of ALOS PALSAR Data

Applications of remote sensing by microwaves have become widely adopted in forest management, but microwave backscattering mechanisms in plantations remain poorly understood. This study attempts to understand backscattering characteristics under different forest structural conditions in plantation forests of fast-growing acacia trees in Sumatra, Indonesia. A general four-component scattering power decomposition method was applied to ALOS PALSAR data collected from 2007 to 2010 to see the variations of acacia plantation. The yearly variation in decomposition powers was compared to forest inventory data with visual assessments of stand conditions. The results were highly consistent with the field-measured data. Based on the variation patterns of decomposition powers, we can identify the presence of understory and distinguish between damaged and well-grown stands. The PALSAR data analysis can also reveal partial damages within a forest compartment, even minor damage in younger forests. This in-depth study indicates that changes in forest stand composition and the growth and degradation of plantation forests can be monitored by transitions in the polarimetric parameters.