西藏山南地区土地沙漠化现状与趋势

山南地区是西藏主要的农业区，也是土地沙漠化强烈发展的地区之一。研究表明，山南地区雅鲁藏布江宽谷大面积河滩地中存在的大量沙源以及本区稀少的林地植被，加之本区干旱多风的气候条件，为本区沙漠化的发生提供了先决条件；随着人口和牲畜数量的增长而导致的草场严重超载过牧和大面积垦荒又加速了本区沙漠化的发展。在目前的土地利用方式和利用强度下，本区沙漠化土地将以平均每年约４０００公顷的速度扩展，预计到２０００年和２０２５年，山南地区沙漠化土地面积将由目前１７６０００公顷增加到２０００００公顷和２９６５００公顷，分别比目前的沙漠化土地面积增加１３．６％和６８．５％，使人类经济活动与脆弱生态环境问题的恶性循环变得更为严重。

DESERTIFICATION AND ITS DEVELOPING TRENDIN SHANNAN REGION OF TIBET

Shannan Region,the main farming area of Tibet,is one of the regions where land desertification is violently developing.Studies show that the vast amount of sands which exists in the wide vallies of the Yarlung Zangbo River and sparse vegetation as well as the windy and dry climate of region are the preconditions of land desertification,the development of desertification is greatly sped up by over grazing and over reclamation caused by population and domestic amimal growth.Under the existing land use pattern and intensity,the land desertification will expand at the rate of 4000 hm 2 per year.By the year of 2000 and 2025,the desertified land areas of the region are expected to 200000hm 2 and 296500hm +2,increasing by 13.6% and 68.5% in comparison with the existing 176000hm 2 of desertified land,which will make the vicious circle between man economic activities and the fragile ecological environment more serious.