【摘要】 在对西藏林芝地区进行垂直带划分的基础上,运用MODIS-NDVI数据对2000-2009年四季不同垂直带的植被演变进行研究。结果表明:1)不同海拔带的NDVI年内变化特征不同,随着海拔下降,植被生长旺盛期由秋季变为冬季;2)10年内,海拔3 000 m以下垂直带的NDVI平均值除秋季增长外,其它季节都表现为降低,而海拔3 000 m以上垂直带植被四季都表现为增长;3)10年来研究区春季、夏季和冬季低于海拔3 000 m的区域,植被退化的面积大于趋好的面积,而海拔3 000 m以上区域,植被趋好的面积大于等于退化的面积,但秋季所有海拔带中植被趋好的面积都大于退化的面积。总之,作为低海拔热带、亚热带和暖温带植被与高海拔寒温带和寒带植被分界线的海拔3 000 m,是一条重要的生态分界线,分界线上下的植被表现出不同的变化趋势,而气温升高是导致植被变化的因素之一,人类活动也有一定的作用。更多还原

【Abstract】 Based on the division of elevation belts in Linzhi area,Tibet,the vegetation changes of four seasons from 2000 to 2009 year in different elevation belts has been analyzed according to the MODIS-NDVI data.The results were: 1) The variations of NDVI within a year were different for different elevation belts,that the most flourish time of vegetation changed from autumn to winter gradually with the decreasing elevation;2) Except for autumn,the mean NDVI of other seasons all decreased within the past 10 years in elevation belts lower than 3 000 m,however,the mean NDVI of all seasons increased in elevation belts higher than 3 000 m;3) In spring,summer and winter of the past 10 years,the deteriorate vegetation area was larger that the improved area in the region lower than 3 000 m,but it was just opposite in the region higher than 3 000 m.In autumn,the improved area was bigger than the deteriorate area for all elevation belts.In summary,as roughly the boundary of tropical,subtropical and warm-temperate vegetations at low elevations between cold-temperate and cold vegetations at high elevations,the elevation of 3 000 m contour was an important ecological line,that the vegetations below or above this line shown different trends,and one of the main driver to change the vegetation was the increasing air temperature,with the human activities imposing some effects as well.更多还原