西藏地区近期植被变化的遥感分析

Dynamical Analysis of Recent Vegetation Variation with Satellite Dataset in Tibet Region

利用2000—2007年的归一化植被指数,分析了近期西藏地区植被的分布状况及变化趋势,从气候条件、人类活动及其他因素等3个方面讨论了典型区域(那曲地区)植被减少的原因。结果表明,植被覆盖最好的区域是林芝及山南南部,其次是昌都、拉萨及那曲东部;不同地区的植被有显著的季节差异。近年来西藏部分地区的植被状况有所改善,植被覆盖减少最严重的区域位于那曲中东部,就全区平均而言,植被覆盖明显减少时段出现在2003—2006年之间;降水量增加(减少)、风速减少(增加)基本对应着植被覆盖的增加(减少)。近期那曲地区气温升高、降水量减少,可能导致植被覆盖减少;人口增长,城市化加剧,过度放牧,有毒植物增多,中草药的挖掘,地下矿产资源的开采以及严重的草地鼠害、虫害等都导致了那曲地区植被覆盖的减少。

Using the normalized difference vegetation index（NDVI） from 2000 to 2007,the distribution and variation tendency of vegetation in Tibet is analyzed. The reason of vegetation degradation in Nagqu region also is discussed based on the climate condition,human activity and other influencing factors.Results show that the area with the best vegetation cover is Nyingchi and south part of Shannan,then Chamdo,Lhasa and east part of Nagqu.The seasonal difference of vegetation is quite evident at different areas.The vegetation status is getting better for some part of Tibet region in the recent years,and the area with the most serious degradation is in the middle and south parts of Nagqu region.The period of distinct vegetation degradation is between 2003 and 2006 on the average in the whole Tibet.The increase（decrease） of precipitation and decrease（increase） of wind speed is basically responding to the increase（decrease） of vegetation cover.The increasing temperature,decreasing precipitation can lead to the vegetation degradation at present in Nagqu.All following factors may resulted in the vegetation degradation in Nagqu region as well such as the growth of human population,intensified urbanization,over grazing,increasing of poisonous grass,dig the Chinese Traditional drug,minerals production under ground,serious rodent damage and pest damage and so forth.