基于SPOT NDVI的祁连山草地植被覆盖时空变化趋势分析

Analysis on the Spatio-temporal Variation of Grassland Cover Using SPOT NDVI in Qilian Mountains

基于RS、GIS技术和SPOT VGT-NDVI数据,运用累积平均法、均值法、趋势线分析法和影像差异法,分析了祁连山草地植被覆盖在时间和空间上的变化特征,并用Hurst指数动态预测祁连山草地植被覆盖未来变化趋势。结果表明:①1999-2007年祁连山草地植被NDVI呈缓慢增加趋势。典型草原和平原草地植被年均NDVIy和生长期NDVIg增加速率高于高寒草甸草地和沙漠草地。祁连山草地植被NDVI增加和减少的面积分别为69776 km2和15928 km2,植被NDVI增加的区域分布在冷龙岭、拉脊山、大通山、达坂山、青海南山、走廊南山、托来山、托来南山等地区,减少的区域分布在乌鞘岭、大通河、石羊河、黑河、北大河、疏勒河等河流河谷以及青海湖周边地区。②祁连山草地植被NDVI年内月和旬变化曲线均呈单峰型。③冷龙岭、宗务隆山、青海南山、镜铁山、拉脊山、乌鞘岭、大通河、黑河、北大河、疏勒河等河流河谷以及青海湖周边等地区未来草地植被覆盖有改善的趋势;走廊南山、托来山、托来南山、大通山以及湟水、石羊河等河流河谷地区未来草地植被覆盖有退化的趋势。沙漠草地、高寒草甸草地未来有改善的趋势;而典型草原和平原草地未来则有退化的趋势。

Based on RS and GIS technology,the grassland cover spatio-temporal variation of Qilian Mountains was analyzed using cumulative average method,average method,trend line analysis,image differencing with the SPOT VGT-NDVI data,and Hurst exponents were utilized to predict the future trends of grassland cover change in Qilian Mountains.The results show that：（1） the grassland vegetation NDVI has been increased in Qilian Mountains from 1999 to 2007.The increase rate of annual average NDVI and growing season NDVI in typical steppe and plain grasslands was higher than that in alpine meadow and desert grasslands.The increased and re-duced areas were 69776 km2 and 15928 km2,respectively.The grassland vegetation NDVI in Lenglong Ridge,Laji Mt.,Datong Mt.,Daban Mt.,South Qinghai Mt.,Zongwulong Mt.,Tuolai Mt.,South Tuolai Mt.was im-proved,and comparatively,the grassland vegetation NDVI was reduced in Wushao Ridge,the valleys of Datong River,Shiyang River,Heihe River,Beida River and Shule River and the surrounding areas of Qinghai Lake.（2） The grassland vegetation NDVI of Qilian Mountains with a single peak curve during the year changes in Qilian Mountains.（3） The grassland cover in Lenglong Ridge,Zongwulong Mt.,South Qinghai Mt.,Jingtie Mt.,Laji Mt.,Wushao Ridge;the valley of Datong River,Hei River,Beida River,Shule River and the surrounding areas of Qinghai Lake will be sustainably improved in the future,and the grassland cover will be degraded in South Zoulang Mt.,Tuolai Mt.,South Tuolai Mt.,Datong Mt.and the valleys of Huangshui and Shiyang rivers.The cover of desert grasslands and alpine meadow grasslands will be improved,and the typical steppe and plain grasslands will be degraded in the future.