Landsat-based analysis of insect outbreaks in southern Siberia

Landsat data were used to examine the effect of large-scale insect outbreaks in the forests of southern Siberia. Two insect outbreaks were studied: Ket-Chulym, similar to1.5 million hectares of forest damaged between 1954 and 1957; and Priangar'e, similar to0.5-0.7 million hectares of forest damaged between 1994 and 1996. Landsat scenes from 1980 to 2000 were analyzed. The optimal Landsat channels combination for detecting damage classes were bands 2 (0.525-0.605 mum), 4 (0.750-0.900 mum), 5 (1.55-1.75 mum), and 6 (10.40-12.50 mum). The damage to the forests caused an increase inradiometric temperature (20.20 +/- 0.04degreesC for damaged forests versus 19.47 +/- 0.02degreesC for healthy forests). The following pattern of forest succession was observed in the outbreak areas: dead stands with dense grass and shrub communities, burn scars, grass and shrub formations, open woodlands, closed young and middle-age birch stands, mature birch stands, and mixed conifer-deciduous stands. Forest regeneration goes through long-term species-change successions, and the rate depends on the size of the outbreak area. On-ground mapping after the outbreak and later Landsat analysis showed that even 45 years after the Ket-Chulym outbreak the area of forests did not increase. In the Priangar'e area approximately 45% of damaged forests have recovered.