关键词: 植被盖度, NDVI差值指数, 定量分析, Landsat TM卫星影像, 石家庄市

Abstract: Vegetation is a key issue which can play very important role in the globe change research. Along with the progress in the 3S field (especially in the remote sensing)，there are more and more researcher use it in their related study. Moderate landsatellite image is widely used in the resource and environment investigation，as well as LUCC and vegetation changes. Shijiazhuan City has a very important position in the north of China，its changes in ecology and environment not only affect Beijing region，but also has indicating role to the other city which located around it. In this paper，we used the Landsat TM image of August 30，2004 and August 15，2010 which covered all of administrative region of Shijiazhuang City. Consulting the others last related works，the NDVI were calculated by the Band 3 and band 4 data of TM image. Based on the NDVI，we also retrieved the vegetation coverage and NDVI difference value. According to this，the vegetation changes and its driving factors were studied. By comparing the relative data from 2004 to 2009，it was found that the vegetation statue of 2010 is better than that of 2004. There are three aspects are support this results. The first one is that the mean NDVI value is 0.470 7 in 2004，but the same item of that in 2010 is 0.541 6. In the 6 years period，NDVI value has increased 0.0709. The second one is that the area ratio of vegetation coverage in severe low class，low class，medium class and high class had reduced 0.12%，0.7%，4.77% and 24.32% respectively，but the severe high class has increased 29.9% at the same time. The third is that the NDVI difference value showed that the ameliorative area of vegetation ratio occupied 83.84% from 2004 to 2010. In different eco-region，the biggest decreasing area of serve low class mainly distributed in the middle hill sub-region，and the low class is in the middle hill sand east plain sub-region. In the east plain sub-region，the reducing degree of medium and high class vegetation coverage was the most remarkable. In the west mountain and the middle hill sub-region，the increasing area of severe high class was above 5 500 hm2 and other classes were all decreasing. From the NDVI difference value，the east economic forest sub-region occupied the biggest area in ameliorative changes，in which the ratio reached 91%，and the smallest area in ameliorative changes appeared in urban forest sub-region. Considering the driving forces of vegetation changes in Shijiazhuang City，we can not infer a direct correlation between vegetation changes and climate changes from 2004 to 2010. We found that the characteristics of the climate changes in this period belong to the warn-dry type，and this is a very disadvantage condition to the vegetation development. But all related results shows that the state of vegetation is ameliorative，this indicated that the human factors are main driving forces to vegetation changes. The factors include regional green ecological construction projects，urban greening municipal construction projects，and economic forest developing projects in plain region.

Key words: vegetation changes, NDVI, vegetation coverage, NDVI difference value, Landsat TM, Shijiazhuang City