伊犁河流域归一化植被指数的时空变化及其对气候的季节响应

The spatio-temporal changes of normalized difference vegetation index and its response to seasonal climate in Ili River basin

基于影响归一化植被指数(NDVI)变化的主要气候因子:气温和降水量,以及2000-2013年16 d合成的MODIS NDVI与同期气象数据,分析了伊犁河流域植被覆盖变化趋势及其对气温和降水量的季节性响应特征.结果表明14 a来,伊犁河流域绝大部分区域NDVI并未发生显著变化,但植被覆盖呈退化趋势的面积远大于呈改善趋势的面积;春、夏、秋三季的植被覆盖均呈退化趋势,降水量与植被NDVI的季节相关性不显著;伊犁河流域4种主要植被类型在三个季节均呈退化趋势,其中草原植被的退化趋势最为显著,而草甸、灌丛、林地在夏季的退化趋势较春、秋两季更为显著.各季节不同植被类型的NDVI与气候因子的关系表明,春季和夏季NDVI与温度关系密切(P<0.05),秋季NDVI的变化是温度和降水量共同作用的结果.

Based on the air temperature and precipitation which are considered as the principal climate factors driving normalized difference vegetation index（NDVI） changes,and on 16 d composite MODIS NDVI and corresponding meteorological data of 2000-2013,the change trend of vegetation cover and its response to seasonal temperature and precipitation in the Ili River basin was analyzed.The results showed that the NDVI of most of the areas had not significantly changed,the area of vegetation cover degraded was much larger than that of vegetation cover ameliorated.In the recent 14 years,the vegetation cover had been degrading in spring,summer and autumn.A correlation analysis between seasonal NDVI and corresponding seasonal climate factors showed that the correlativity between NDVI and temperature was significant in spring and summer,and the correlation coefficient between NDVI and precipitation in all three seasons did not reach a significant level,indicating that temperature was a main factor influencing seasonal changes in vegetation cover in the Ili River basin.It was found that four different vegetation types experienced a degrading trend in all three seasons,with the degradation of grassland vegetation being most remarkable,and the degradation trends of meadows,shrubs and forests in the summer being more significant than the other seasons.The NDVI of most vegetation correlated significantly to temperature（P〈0.05） in spring and summer,and the changes of NDVI correlated to the interaction between precipitation and temperature in autumn.