甘肃河西地区沙漠化遥感监测评估

 河西走廊位于我国西北干旱半干旱区，由于自然环境的变化和人为因素的影响，生态环境脆弱，沙漠化严重。随着遥感和GIS的发展，为沙漠化研究提供了有效的途径。利用2002和2008年6～8月的MODIS数据（空间分辨率为1 km），采用改进型土壤调节植被指数（MSAVI）、地表反照率（ALBEDO）、陆地表面温度（LST）、植被覆盖度（FAVI）和温度植被旱情指数（TVDI）作为沙漠化程度的指标，对河西地区沙漠化特征进行了研究。结果表明：河西地区荒漠化土地面积较大，占总面积的50%以上。2008年的荒漠化土地面积比2002年减少了6 431.64 km²，非荒漠化土地和轻度荒漠化土地面积增加，分别增加了2.55%和0.26%；中度、重度和极重度荒漠化土地减小，分别减小了1.40%、1.09%和0.31%。荒漠化的逆转速度大于发展速度，呈现整体逆转，局部发展的趋势。研究区荒漠化土地以轻度荒漠化为主，2002年和2008年分别占23.64%和23.90%；其次为中度，分别为18.47%和17.07%；重度所占比例分别为12.71%和11.62%；极重度所占比例很小，不到1%。降雨和风速对沙漠化的逆转起主要作用，2008年的降水比2002年多，风速小。

Desertification assessments of Hexi regions in Gansu province by remote sensing

the Hexi region lies in the arid and semiarid regions of China, its fragile ecological environment and severity desertification were caused by natural environments change and humanity influences. With the development of remote sensing and GIS, it provides an effective method to research desertification. In this paper, MODIS data between June and August in 2002 and 2008 were used to analyze desertification, and five indexes {including MSAVI (Modified Soil-Adjusted Vegetation Index), Surface Albedo, LST (Land surface temperature), FAVI and TVDI} were used to assess degrees of desertification. The results indicate that the desertification land in Hexi region is larger and occupies more than 50% land in total land. The desertification land was decreased by 6431.64 km2 in 2008, the non-desertification land and slight desertification land increased by 2.25 and 0.26%, respectively; moderate, severer and extremely severer desertification land decreased 1.4, 1.09 and 0.31%, respectively. Summery, the reverse rate of land desertification is larger than development rate, and shows that reversing is common tendency but part region is in desertification development. In the study region, it mainly is slight desertification land, 23.64 and 23.90% in 2002 and 2008, respectively, and then belongs to moderate, severer and extremely severer desertification lands.