1995～2000年中国沙地空间格局变化的遥感研究

Remote Sensing Based Analysis of the Distribution Pattern and Dynamic Changes of Sandy Land in China From 1995 to 2000

利用遥感方法 ,在覆盖全国的 Landsat-TM数据的基础上 ,对 1 995年和 2 0 0 0年中国沙地的空间分布格局与动态变化进行了调查。结果显示了 2 0 0 0年中国沙地总面积为 5 9× 1 0 4 km2 ,主要分布于各主要沙漠和我国的 7个主要省份。1 995～ 2 0 0 0年 ,有 470 9.7km2的土地转化为沙地 ,同时又有 2 1 5 6.4km2的沙地转化为其它土地利用类型 ,沙地总面积扩大了2 5 5 3 .3 km2 。对变化为沙地的土地进行分析 ,发现草地占主要部分 ,但耕地所占的比重也非常突出 ,同时也表明有部分沙地变化为草地和耕地。根据土地沙化的空间分布特征 ,将土地沙化过程分为 5种格局 :沙地 -绿洲型、沙漠型、沙地 -黄土过渡型、沙地 -草地型和高原风蚀型。通过对中国发生土地风蚀沙化的主要省份在 1 995～ 2 0 0 0年间的土地利用动态变化发现 ,土地利用变化是促使土地发生沙化的一个重要因素。在 5 a的时间里 ,7个省份耕地总面积扩大了 90 3 9.7km2 ,草地减少了 1 1 5 97.9km2。耕地的增加部分几乎均表现为对草地的侵占 ,土地变为沙地也主要发生在草地区。人为因素导致的耕地面积扩大是促使土地沙化的重要原因。对主要省份的土地利用方式进行分析 ,探讨不同地区减轻土地沙化趋势下的土地利用布局。

With rapid economic growth and the world's largest population, land degradation and ecosystem deterioration in China are becoming more and more serious, especially wind erosion and sandy desertification it caused. Wind erosion may cause land use changes as soil is eroded or lands are buried by sand dunes. Irrational land use, typically represented by the reclamation and over grazing in semi arid and arid area in China, can also aggravate wind erosion. Moreover, when wind erosion happens in vast areas, dust and aerosol from these areas will influence global climate and environment. Relation between sandy desertification and land use changes in China is one of the key points to be studied. Using remote sensing and Geographical Information System (GIS), the paper studies the spatial temporal changes of sandy land in China. Based on nationally covered Landsat TM data, the spatial distribution of sandy land in 2000 and 1995 is investigated, and its changes are analyzed. In 2000, total area of sandy land in China is 59×10 4km 2 which distributes mostly in seven provinces (Xinjiang, Inner Mongolia, Qinghai, Gansu, Ningxia, Shaanxi, Tibet) that lie to the Northwest and Southwest China. Results show that 4709 7 km 2 of land has changed to sandy lands. At the same time, 2156 4 km 2 of sandy land has changed to other land use. Thus the net change to sandy land is 2553 3 km 2. Grassland is the main type of land use that changes to sandy land. At the mean time, the area of cropland that changes to sandy land is also noticeable. To the area where sandy land is shrinking, the grassland and cropland are expanding, while where the sandy land is expanding, the grassland is shrinking. To the process of desertification in China, five geographic regions can be classified: oases, desert, the Loess Plateau, grassland and Qinghai Tibet Plateau. Each region has its own characteristic in the process of sandy desertification. To the oases, more and more grasslands between cropland and desert are changing to cropland or desert. To the desert areas, the process of desertification is represented by the transition of low covered grassland to sandy land. To the Loess Plateau, sandy lands are expanding due to the expansion of Mao Us Sandy Land to the northwest of the plateau. To most grasslands in semi arid and arid areas, their changes to sandy land are the most obvious. To the Qinghai Tibet Plateau, land use changes are mostly caused by wind erosion. Because of the dramatic fluctuation of daily temperature, the weathering process is intense. With strong wind, the sandy land expands through encroaching the grassland and cropland in the valleys. Irrational land use contributes most to the sandy desertification in China. From 1995 to 2000, the increase of the total area of cropland in the seven provinces is 9039 7 km 2, whereas the total area of grassland decreases by 11597 9 km 2. Almost all cropland expansion is from the reclamation of grassland while most of the expanded sandy lands come from grassland.