Research On Vegetation Change And The Environmental Impact Factors In Hailiutu River Basin

Erdos Plateau is rich in coal, oil, gas and other mineral resources. It will be one of the most important energy bases of China in the 21st century. Hailiutu River basin is located in the north of the Erdos Plateau. Because it is in arid and semi-arid southeastern edge of Maowusu Desert, the ecological environment is very fragile. In recent years, the increasing development of the region resulted in severe environmental changes: depletion of groundwater level, salinization and environmental destruction caused by mining in some regions. This does not meet with national environmental strategies for sustainable development in China. Therefore, strengthening the regional ecological environment survey and evaluation are very important to the rational development of the Erdos Plateau. The study selected vegetation as the research focus, which is the most important factor in environment and the normalized difference vegetation index (NDVI) as the main indicators. By means of variation analysis of vegetation during 24 years(1985 to 2008) and monthlyvariation of vegetation in 2008, the relationship between vegetation and impact factors of meteorology, elevation, topography, groundwater, and the human activity were discussed in this thesis.It is found that: (1) the annual average NDVI of Hailiutu River basin is changed between 0.05and 0.35, and the vegetation became better with year from 1985 to 2008 except the year of 1989. (2)In the last twenty-five years the largest Vegetation changes was in valley region. The most obvious change was in sandy areas in northern region, which average NDVI in northern sandy region increased by 200% compared with 1985. The most unobvious changes of vegetation appeared in Bulang River region and the southwestern shrub areas. (3)In the meteorological factors which affecting the distribution of vegetation, temperature and precipitation played the most dominant roles and there was a one year delay about the effect of rainfall on vegetation. The evaporation has liitle impact on vegetation change. (4) Through the relationship between vegetation and elevation, it is found that: the NDVI in the elevation of 1050m is relatively low and in the data of the elevation of 1350m and 1300m is relatively high. (5) Based on the relationship between vegetation and groundwater level, it is found that: 0.3m is the threshold of the ground water depth for aquatic vegetation, 0.8m is threshold of groundwater depth of soil salinization, 2.9m is the groundwater depth with best vegetation growth, 2.8m is best groundwater depth for the dominant vegetation, 0.8 ~ 4m plant was suitable water depth for the local dominant vegetation. (6) The impact of human activity on the vegetation is changed obviously.