基于Landsat长时间序列数据的敦煌绿洲动态变化分析

Dynamic change analysis of Dunhuang Oasis based on long time Landsat image series

绿洲是干旱区独特的自然景观,是干旱区人们赖以生存和发展的物质基础。以敦煌绿洲为研究区域,基于Landsat TM长时间序列遥感图像,采用最佳指数因子研究最佳波段组合并进行图像分类,基于转移矩阵分析了绿洲主要覆被构成要素的转换特征,并基于土地利用类型动态度模型进行了动态变化分析。结果表明:1975-1998年间敦煌绿洲面积呈缓慢扩张趋势(平均0.35 km2/a);1998-2006年间绿洲面积快速增大(平均3.88 km2/a);2006-2011年间绿洲面积基本稳定。1990-2006年间水浇地和林地的面积总体呈增加趋势;2006-2011年,人工干预加速了土地利用方式的转变。

The Dunhuang Oasis is a typical representative of a desert landscape in arid area, as well as the material basis for human beings in arid area to survive and develop. However, the oasis has obvious environment vulnerability. Besides, salinization and desertification can induce the degradation of the oasis ecosystem. Therefore, the dynamic change analysis on the Dunhuang Oasis has considerable significance. This paper takes China＇ s Dunhuang Oasis as research area to study its dynamic change. Multi-source data, including long-time series Landsat MSS and TM data from 1975 to 2011, field investigation material of Sep 27,29 and 30,2011, land use map of 1990 are used to determine well-adapted classification method using OIF and maximum likelihood algorithm. Information of the land cover and land use is extracted based on the well-adapted classification method. Dynamic change of the Dunhuang Oasis is analyzed based on change detection statistics and land use dynamic degree model. The result reveals that during the 36 years from 1975 to 2011, the boundary area tended to increase from 1975 to 1998 with a speed 0.35 km2/a, and increase from 1998 to 2006 with a speed 3.88 km2/a. The boundary area became stable from 2006 to 2011. During the period of 1990 to 2011, the irrigable land and forest land area tended to increase; the saline and alkaline land area tended to increase, decrease, and then increase ; the sand and bare rock area decrease and then increase. The land cover change detection reveals as follows： from 1990 to 1998, 14.27 km2 of irrigable land and forest land changed into saline and alkaline land, while 28.28 km2 of saline and alkaline land changed into irrigable land and forest land, and 0.2 km2 of irrigable land and forest land changed into sand and bare rock, while 6.09 km2 of sand and bare rock area changed into irrigable land and forest land. From 1998 to 2006,23.85 km2 of irrigable land and forest land changed into saline and alkaline land, while 38.11 km2 of saline and alkaline land changed into irrigable land and forest land, and 0.34 km2 of irrigable land and forest land changed into sand and bare rock area, while 2.65 km2 of sand and bare rock area changed into irrigable land and forest land. From 2006 to 2011,42.42 km2 of irrigable land and forest land changed into saline and alkaline land, while 15.13 km2 of saline and alkaline land changed into irrigable land and forest land, and 0.31 km2 of irrigable land and forest land changed into sand and bare rock area, while 0.39 km2 of sand and bare rock area changed into irrigable land and forest land. The conclusion is that the irri- gable land and forest land were expanded from 1990 to 1998 and from 1998 to 2006,while the irrigable land and forest land were shrinked from 2006 to 2011. Comprehensively, the constituent and structure of the Dunhuang Oasis evolved from 1998 to 2006 while degenerated from 2006 to 2011. Land use and land cover change rate was accelerated from 2006 to 2011.