Forest monitoring with JERS-1/SAR and ALOS/PALSAR

JERS-1/SAR images taken in 1990´s and ALOS/PALSAR images taken in 2000´s are used and examined the deforestation status during ~14 years. Many trees had been fallen by a typhoon hit in 2004 in a test site, Tomakomai. There is also a plantation area and the site show active change during the term. The forest stands could be roughly classified for four types, forest stands, vacant, where almost all trees were carried out, and two types of transitional stands from a forest to a vacant. Many deforested areas are easily detected by using the difference of backscattering coefficients between two images, if fallen trees have been carried out from the stands. The change from the normal forest to the vacant stands causes 3.1dB decrease in the sigma⁰ _HH. On the other hands, transitional stands show almost same backscattering as the normal forest stands, although. Three- component scattering model shows surface scattering component accounts for 50% over the vacant stands, while volume scattering component accounts for ~60% over the forest stands. But the model doesn´t show the clear difference between transitional forest site and normal forest. The temporal changes of the forest during 14 years are also examined for the plantation area. One stand show gradual increase of sigma⁰ and the values seem to be saturated around 17.4 tons/ha (~5 m in average height).