三江源区植被覆盖度的定量估算与动态变化研究  

QUANTITATIVE ESTIMATION AND DYNAMIC CHANGES OF VEGETATION FRACTIONAL COVERAGE IN THE SANJIANGYUAN REGION

作　　者：于秀娟[1,2] 燕琴[1] 刘正军[1] 郗利华 王苑[3] 

机构地区：[1]中国测绘科学研究院摄影测量与遥感所,北京100830 [2]国家光电测距仪检测中心,北京100039 [3]青海省基础地理信息中心,青海西宁810001

出　　处：《长江流域资源与环境》2013年第1期66-74,共9页Resources and Environment in the Yangtze Basin

基　　金：国家科技支撑项目(2012BAB16B00)

摘　　要：植被覆盖度是衡量地表植被状况的重要指标,其时空分布和变化对政府进行区域规划和决策起着重要作用。MODIS植被指数是区域植被覆盖度提取的重要数据源。利用2000年1月到2009年10月的MODIS 250m归一化植被指数16d合成产品(MODIS NDVI)和其他MODIS辅助数据估算三江源区的植被覆盖度并分析时空格局变化趋势。在混合像元二分模型的基础上改进了NDVI参数的确定方法,然后利用重构后的MODIS数据估算植被覆盖度。与2007年8月的野外采样点数据比较,估算精度是87.72%,相关系数r为0.889 7,表明该模型估算大面积植被覆盖度是可行的。将获得的植被覆盖度分为5个等级,从年最大化植被覆盖度Mfc的角度进行10a里植被覆盖度的年际变化趋势分析和时空格局变化分析。趋势分析结果表明,2000～2009年三江源区植被覆盖波动式变化,东北部地区得到改善,西部地区在退化,总体呈现退化趋势;时空格局变化分析结果表明,植被覆盖破碎度降低,趋于集中化分布;不同等级覆盖度分布的复杂化程度降低。The Vegetation Fractional Coverage （VFC） is a fundamental parameter of climate and hydrologic models. The spatio-temporal distribution and change of the VFC is important for future regional planning and governmental policy-making. Moderate Resolution Imaging Spectroradiometer （MODIS） vegetation in- dex （VI） is an important data to extract global and regional VFC. The objectives of this study are to ex- plore the potential of quantitatively estimating the VFC using time-series of MODIS 250 m Normalized Difference Vegetation Index （NDVI） 16-day data and other auxiliary MODIS data,and to monitor the spa- tio-temporal patterns of the changes from 2000 to 2009 in the Sanjiangyuan Region. Under the assumption that each pixel of a MODIS image contains two NDVI end members：vegetation NDVI （NDVIveg） and bare soil NDVI （NDVI^o~I） ,this paper improved the determination of parameters NDVIwg and NDVIso^l in the pix- el unmixing model. Then based on the time-series reconstruction of MODIS data, the VFC was quantitative- ly retrieved using different pixel unmixing models. The retrieval accuracy was assessed at 88.72% and the correlation was 0. 8897 for Aug. 2007 ,which suggested this method might be generally useful for VFC esti- mation at broad spatial scales. The inter-annual dynamic variability trends and the spatio-temporal land- scape patterns of change were characterized over the past ten years based on the year-maximization vegeta- tion fractional coverage （Mfc）. The slope trend analysis and field investigation indicated that the change trend of vegetation was fluctuant and the VFC had been improved in the eastern part while worsened in the western part. The are to 2009. The patterns plicated degree of the a of vegetation degradation was larger than that of vegetation improvement from 2000 of change revealed that the coverage fragmentation had been decreasing and the com- distribution of different grades had been reduced.

关 键 词：三江源区 植被覆盖度 时间序列 MODIS NDVI 像元二分模型 动态变化 

分 类 号：TP79[自动化与计算机技术—检测技术与自动化装置]