基于遥感分析13年来石羊河上游山区植被变化研究

NDVI是监测区域植被生长状况及植被覆盖度最常用的指标。基于2002和2015年9月上旬植被生长期内的Landsat TM遥感卫星影像,以ENVI 5.2软件为影像处理工具,分别获取两期影像的NDVI,研究内陆河石羊河流域上游祁连山山区植被覆盖度的变化;利用主成分分析法对两期影像进行了监督分类,获得各植被类型的面积以及变化情况。结果表明,2015与2002年相比,石羊河上游地区高覆盖度、中等覆盖度、低覆盖度植被面积均有所下降,分别下降了18.4%、13.4%、10.1%,而极高覆盖度和极低覆盖度面积均有所增加,分别增加了0.5%、26.6%。NDVI差值植被指数结果显示,上游地区植被发生退化的面积为6935.6154 km²,占总面积的51.26%,而发生改善的面积为6595.2834 km²,占总面积的48.74%。通过监督分类获得的各植被类型的面积显示,乔木林面积增长显著,13年间增长了108.75%,但是灌木林和草地的面积缩小严重,分别减少了49.87%、19.78%。祁连山石羊河流域上游森林植被在13年间呈现退化趋势。

Monitoring vegetation dynamics in the mountainous area of the Shiyang River upper reaches using remote sensing technology

NDVI (the normalized difference vegetation index) is the most commonly used index for monitoringvegetation growth conditions and coverage.In this study,Landsat TM images were collected during the vegetation growth periods of September 2002 and 2015 in the mountainous area of the Shiyang River Basin's upper reaches in the Qilian Mountains.The two periods' NDVI were calculated and vegetation dynamics were analyzed by using ENVI 5.2 software.In addition,the images were analyzed using supervised classification and principal component analysis so that the areas and changes of vegetation types could be calculated.Results showed that vegetation areas with high,medium and low coverage had decreased in 2015 compared to 2002 by 18.4％,13.4％ and 10.1％ respectively.Vegetation areas with extremely high and extremely low coverage increased by 0.5 ％ and 26.6 ％ respectively.NDVI results showed that the degraded and improved areas of vege-tation were 6935.6154 and 6595.2834 km2,accounting for 51.26％ and 48.74％ of total area respectively.Analysis of vegetation type areas showed that the area of arbor forest had significantly increased by 108.75 ％,while the areas of shrub forest and grassland had significantly decreased by 49.87％ and 19.78％ respectively.These findings show that forest vegetation in the upper reaches of the Shiyang River Basin has degraded over the 13-year period.