Relating envisat ASAR and ALOS PALSAR backscattering coefficient to spot NDVI for monitoring seasonal change of pasture biomass in Western Australia

Regular estimates of pasture biomass are invaluable for managing the supply of annual pasture in Western Australia (WA). NDVI has been used for estimation of biomass in Australia, with some shortcomings which could be overcome by SAR. The regression model between pasture biomass and SAR backscatter could be obtained if sufficient ground measurements of biomass are available. However, biomass measurements over a large area are not easy to be obtained. Therefore, we are trying to relate ENVISAT ASAR/ALOS PALSAR backscatter to NDVI, and then to biomass. It was found that time series of NDVI is significantly correlated to ASAR HH, HV+HH, VV+VH (dB) with R² of 0.71, 0.67, and 0.63, respectively. NDVI is also significantly related to ALOS PALSAR HH (R²=0.82). In conclusion, the investigation confirmed the potential of ASAR and PALSAR data monitoring biomass and its seasonal change in the temperate Southwestern Australia, and provided a solid foundation for further research concerning quantitative estimation of biomass.