基于MODIS/N_(DVI)时序数列的长沙市植被覆盖动态变化

Dynamic changes of vegetation cover in Changsha city based on MODIS/N_(DVI)

NDVI是识别植被的一个重要参数,与植被盖度有明显的相关性。NDVI时序变化曲线反映了植被随时间的推移而发生的生长和变化状况。本研究利用2000～2009年长沙市MODIS数据,采用均值变化法分析了长沙市连续10 a NDVI的时空演变。结果显示：这10 a间,植被在生长季（4～10月）总体长势较好,年均NDVI都在0.9以上;从时间角度来看,NDVI呈现缓慢增加趋势,但期间出现2个峰值和1个最低值,分别为2002年、2006年和2003年;从空间角度来看,东部NDVI最高,西部其次,中部最低,植被覆盖以中、高植被覆盖区为主,随时间变化,NDVI在空间上表现出波动变化;NDVI年代际变化率表明,长沙市NDVI值在2000～2009年连续10 a时间里,既有增加,也有减少。2003、2007和2009年年代际变化率为负值,其余年份为正值。

The change of vegetal index can reveal the evolvement of environment. Long-term quantitative analysis of vegetal distribution and change can illustrate the reasons of environment change. Based on the continuous MODIS data with the spatial resolution of 250 m × 250 m and temporal resolution of 16 d from 2000 to 2009,by means of some image software such as ENVI 4.8 and Arcgis 9.3,the variations of NDVI in Changsha were analyzed. The results show that the plantations were growth well between the months April and October and the annual mean NDVI were all above 0.9,the NDVI showed a slow increase trend which varied with years; from the space perspective,the highest NDVI was in the east and next is west,the middle part was the lowest and they showed a fl uctuation change with years. The vegetation cover mainly was in medium and high; the annual gradient indicates that the NDVI in Changsha city between 2000 and 2009 both increased except in 2003,2007 and 2009.