Analysis of the tropical forest vegetation change in Xishuangbanna of P.R. China by using LANDSAT TM

Abstract

The tropical forest change of Xishaungbanna in P.R.of China was studied here, which includes several steps. Firstly, The LANDSAT TM images acquired respectively on March 26, 1987, February 10, 1997, and March 6, 2000 were geometrically corrected, matched, and radiantly corrected. Secondly, the Normal Different Vegetation Index (NDVI) was formulated for the three periods. Thirdly, the false color composition images were achieved respectively for the three periods, which were used for visually interpreting forest and non-forest. Fourthly, the forest areas of the three periods were extracted semi-automatically from NDVI of the three periods by their suitable threshold. Fifthly, the forest areas of the three periods were changed into vector form. Sixthly, the extracted forest area of the three periods in vector form superposes their false color composition images for evaluating their accuracies. Finally, the map of forest change among the three periods was made, and the forest change area was calculated. The research shows: The decreased tropical forest area between 1987 and 1997 is 234558 hectares, accounted for 19 percent of the tropical forest area in 1987. The decreased tropical forest area between 1997 and 2000 is 41237 hectares, accounted for 4.2 percent of the tropical forest area in 1997