基于遥感的青海省植被覆盖时空变化定量分析

Analysis of Vegetation Spatial and Temporal Variations in Qinghai Province Based on Remote Sensing

使用1 km分辨率MODIS NDVI时间序列数据,采用决策树分类、监督分类和非监督分类相结合的综合分类方法,将青海省土地覆盖类型划分为14个类别.这种分类方法重点突出了植被,特别是稀疏植被（包括稀疏草地和稀疏灌丛）的空间分布.在将青海省分为5个高程带的基础上,使用GIS软件的空间分析功能,对青海省2001-2006年的地表植被覆盖在各级高程带上的空间分布和时间序列变化进行了定量分析.结果表明,近5 a青海省的植被覆盖有所改善,植被覆盖面积从2001年的370 047 km^2增加到2006年的374 576 km^2,植被覆盖率增加了0.63%.青海省5级高程带中高山地带的植被覆盖率最高,达到67.92%.在青海省各级高程带上,高山地带上中覆盖度草地的分布面积最大,为94 003 km^2.高山地带高覆盖度草地的面积增加最多,为1 280 km^2.5 a间植被覆盖变化最大的是高山地带上稀疏草地向中覆盖度草地的转变,转变面积达到15 931 km^2.

1 km MODIS NDVI time series data combining with decision tree classification,supervised classification and unsupervised classification was used to classify land cover type of Qinghai Province into 14 classes.In our classification system,sparse grassland and sparse shrub were emphasized,and their spatial distribution locations were labeled.From digital elevation model（DEM） of Qinghai Province,five elevation belts were achieved,and we utilized geographic information system（GIS） software to analyze vegetation cover variation on different elevation belts.Our research result shows that vegetation cover in Qinghai Province has been improved in recent five years.Vegetation cover area increases from 370047 km^2 in 2001 to 374576 km^2 in 2006,and vegetation cover rate increases by 0.63%.Among five grade elevation belts,vegetation cover ratio of high mountain belt is the highest（67.92%）.The area of middle density grassland in high mountain belt is the largest,of which area is 94003 km^2.Increased area of densegrassland in high mountain belt is the greatest（1280 km^2）.During five years,the biggest variation is the conversion from sparse grassland to middle density grassland in high mountain belt,of which area is 15931 km^2.