Investigations on ARD monitoring in Siberian forest using spaceborne SAR

Nation-wide monitoring of afforestation, reforestation and deforestation (ARD) activities is explicitly addressed in the Kyoto Protocol. This paper investigates the feasibility of ARD mapping using spaceborne synthetic aperture radar (SAR) and interferometric SAR (InSAR) data from the European Remote Sensing (ERS) satellite, the ENVISAT satellite and the Japanese Earth Resources Satellite (JERS). As test site the forest enterprise of Bolshe-Murtinsky, Central Siberia, was chosen since relatively long time series of ERS-ENVISAT and JERS SAR data were available spanning 1996-2004 and 1994-1997 respectively. The ERS-2 SAR and ASAR Image Mode (IM) backscatter acquired during winter under frozen conditions decreased by 1-2 dB following stand-wise logging, whereas reforestation in young stands could not be detected. The JERS SAR backscatter commonly showed stronger forest/nonforest contrast, between 2 and 4 dB depending on the weather conditions at image acquisition, whereas the repeat-pass JERS coherence was characterized by a 0.3-0.4 difference before and after deforestation activities. None of these two signatures was found to provide information on reforestation, mainly because of the too short time series with respect to the forest growth rate. To assess the possibility of using ERS-ENVISAT- and JERS-type of data for reforestation, a first-order approach has been developed. Preliminary results show that young stands can be distinguished from nonforested areas not earlier than approximately 25 years using JERS repeat-pass coherence and 30 years using ERS-ENVISAT SAR backscatter.