基于SPOT-VGT的宁夏盐池县近8年生态环境动态监测

为评价宁夏盐池县近年来生态环境质量的变化，该文利用最新的10 d合成SPOT-VGT NDVI数据，合成最大化植被指数(MNDVI)和年平均植被指数(YMNDVI)，并结合盐池县的降水数据，分析了1999—2006年间MNDVI和YMNDVI的变化。同时，还用一元线性回归分析法模拟了这8年来每个像元MNDVI和YMNDVI的变化趋势。MNDVI的变化趋势显示，在1999—2006年盐池县植被出现改善的面积为6 345 km2，占总土地面积的73.27%，而出现退化的面积为1 449 km2，只占总土地面积的16.72%；YMNDVI的变化趋势也显示，植被出现改善的土地面积大于植被出现退化的土地面积。综合分析结果表明，宁夏盐池县1999年以来整体生态环境处于好转状态，虽然有部分年份受严重干旱影响出现植被退化，但整体上地表植被开始增加，生态环境开始改善，已扭转了20世纪90年代生态环境恶化的局面，并开始显露出一定的抵御自然灾害的能力。 

Dynamic monitoring of eco-environment change over 1999-2006 in Yanchi County, Ningxia Hui Autonomous Region based on SPOT-VGT data

For estimating the eco-environment changes in Yanchi County, Ningxia Hui Autonomous Region, northwestern China, the authors used the 10 days synthesized normalized difference vegetation index (NDVI) which acquired by SPOT-VGT sensor, synthesized maximum normalized difference vegetation index (MNDVI) and yearly mean normalized difference vegetation index (YMNDVI) and analyzed their changes from 1999 to 2006 based on the precipitation data. At the same time, the paper used the linear regression methods to analyze the change trend of MNDVI and YMNDVI during these 8 years. The results of MNDVI change trend show that Yanchi County has 6 345 km² areas, about 73.27% of whole county, where vegetation cover was increasing, and 1 449 km² areas, about 16.72% of whole county, where vegetation cover was decreasing. The YMNDVI change trend also shows that Yanchi County has more vegetation increasing areas than decreasing areas. The ecosystem of Yanchi County has been greatly changed since 1999. Although the vegetation was affected by drought disaster that happened in the period, the ecosystem has become more and more stabilization that can endure some natural disasters.