Spatio-temperal Response Of NDVI In A Large Basin With High-altitude In Tibet, China

The paper under the National Natural Science Foundation of China (41301611) and Natural Science Foundation of Jiangsu Province (BK20130103) funding, based on the features of high elevation and large basin, the dissertation takes a research into the Yarlung Zangbo River Basin and Grand Canyon National Nature Reserve. A spatial analysis of different vegetation types on the altitudinal gradient distribution is done through SPOT_VEGETATION NDVI data sets and spatial analysis of GIS. Additionally, meteorological influences is considered while doing research on the NDVI regularity of temporal and spatial variation of the vegetation types and altitudinal gradients of Grand Canyon National Nature Reserve.With the purpose of figuring out the response relationship between change of the Vegetation Patterns and the features of NDVI vertical zonation in the background of global climate changing. The main conclusions are as follows:(l)Millin is the most part of vegetation types in Yarlung zangbo River Basin, and vegetation types are descend from downstream to upstream in Basin. Miscellaneous grasses in Alpine kobresia meadow have the largest,area above all, and alpine sparse vegetation is second, both of them are consists of the 52.5% areas of the basin, which are distribute on the elevation above 4000m, Inversly, coniferous and broad-leaved forests on the elevation below 4000m.(2) The trend of annual NDVI showed a significant growth in different altitudinal gradient of basin from 1999-2013, and the different seasons NDVI are same, which NDVI are decreases with increasing elevation. NDVI changes have the significant vertical gradient in basin. Among them, the <3500m altitude’s NDVI growth rate is the maximum, and the >3500m altitude’s NDVI growth rates are decrease as elevation increases. From July to September and October to December, the<4500m altitude have a significant growth trend, and help the basin’s NDVI growth.(3) The various altitudinal gradients are influenced by the differences of the vegetation. NDVI of the<3500m altitude is influenced by coniferous forest and hardwood forests, the 3500-4000m altitude’s by irrigation grass transition and coniferous forest, the 4000-4500m altitude’s by irrigation grass transition and irrigation bundle, the 4500-5000m altitudes by grass meadow, alpine vegetation and irrigation bundle, and two altitudes’ above 5000m by grass meadow and Alpine vegetation.(4)Since 2000, Medog natural reserve are renamed the Yarlung zangbo Grand Canyon National nature reserve by the State Council of China, Reserve areas are expansion, the NDVI improvement and vegetation growth are better than before. Under the climatic conditions of increasing temperature and decreasing precipitation, NDVI of test zone in Reserve are growth maximum, increased significantly than the core zone and buffer zone(5) the length of phenology of Basin have growed in recent 15 years, characterized by end of the growing season(EOG) is delayed than the start of the growing season(SOG), and help the length of growing season(LOG) to grow. The LOG’s growing speed are fastest, that is the reason the length of phenology had growed in Basin.