西藏拉萨市土地沙漠化现状与趋势

西藏拉萨市已有１７万ｈｍ２土地沦为沙漠化土地，沙漠化的危害涉及农牧业生产和人民生活的各个方面。研究表明，本区沙漠化过程是在干旱多风的气候条件下，以缓慢的自然沙漠化过程为基础，自然与人为因素共同作用，相互激发，相互促进所形成的人为加速与加剧过程，它是强度的不合理的土地利用与脆弱的生态环境和贫乏的自然资源之间不相协调的产物。在目前的土地利用方式和强度下，拉萨市沙漠化将会进一步加剧。预计到２０００年和２０２５年，拉萨市沙漠化土地面积将分别增加到１９．６万ｈｍ２和２８．９万ｈｍ２，比目前的沙漠化土地面积扩大３．０万ｈｍ２和１１．９万ｈｍ２，使人类的生存环境进一步恶化。

Land Desertification and Its Developing Trend in Lasa Area of Tibet

Land desertification has become the first importance of environmental problem in Lasa area of Tibet. At present, about 5.86% of the total land area of the region has been desertified. Among them, moving sandy land, semi fixed sandy land, fixed sandy land, uncovered gravel land and sparsely vegetated land account for 5.41%, 19.55%, 21.60%, 10.11% and 43.33% of the total desertified land respectively. Analysis of the factors related to the desertification shows that among various natural and man made factors related to the desertification, flood land area and density of farming and stock raising population are in significant positive correlation to the desertified land area, while forest land and per capita farm land and per head animal range area are in significant negative correlation to the desertified land area. These indicate that the dry and windy climate conditions and large area of sandy land surface are the prerequisite of land desertification in the area, while intensive and unreasonable land use, especially overload and over grazing of the range are the main reasons of desertification aggravation.Under the existing pattern and intensity of land use, the desertified land is expected to reach 196 000 hm 2 and 289 000 hm 2 by 2000 and 2050, which will steadily deteriorate the living condition of the local people. Rational use of land resources is the fundamental way to control land desertification. Improving land use condition, regulating land use structure and enhancing land use management are the three major aspects of rational use land resources. Desertification control in Lasa area should be started with the three aspects.