Research The Change Of Vegetation In Ejin Oasis After Transferring Water

Oasis is invisi-bility of the landscape in the condition of a stable water source against the big background of climate control in desert and arid semi-desert region. It plays a decisive role in the regional economic development. However, the dependence of single and absolute water resources on survive and develop of oasis is doomed to the fragile ecosystems of oasis. The reducing or unreasonable use of water resources very easily leads to the degradation (desertification) of oasis ecosystem. Thus the stability of oasis and the security of ecological and economic are jeopardizing.Ejin Oasis is located in the western of Inner Mongolia which is extreme drought. It is the ecological barrier in the northwestern region of China. The shortage of water resources, vegetation decay and oasis shrinking seriously impact the production of regional agriculture, forestry and animal husbandry and the development of other industries due to the upriver excess development in recent decades, to the late 20th century, the deterioration of the ecological environment in oasis gradually. It becomes the obstacle of sustainable development of regional economic.Vegetation coverage is a very important eco-climatic parameter and is a comprehensive quantitative index of the status of plant communities covering the earth surface. Study the estimate and change of vegetation coverage play an important role in environmental change of ecosystems and are of great significance in the hydrology, ecology, global change and other fields. In this paper, the image data of TM / ETM in the year of 1990, 2000 and 2006 is used as the main data source combining field survey. The methods are including combining remote sensing and GIS, combining quantitative and qualitative, combination of landscape ecology and the traditional methods such as step research. The research is focus on the change of vegetation cover in Ejin oasis since transferring water. It shows that:1. Sub-pixel decomposition model is used to calculate vegetation coverage. The results of precision test of model show that the model basically meets the requirements of precision in research work and suit for researching the changes of vegetation cover in oasis.2.By analyzing vegetation status in quo of Ejin oasis, it shows that low vegetation cover is the main type of vegetation cover in oasis, an area of 4706.17 km2 accounting for 30.34% of the total area in study area. This is followed by middle vegetation cover and high vegetation cover, account for 1.87% and 0.23% of the total area in study area.3. It shows that vegetation coverage increased after transferring water in Ejin oasis through analyzing the dynamic changes of vegetation cover in 2000-2006. The largest transferring area is no vegetation cover transferring to the low vegetation cover, an area of 553.23 km2, accounting for 5.14% in a total area of no vegetation cover in 2000. This was followed by low vegetation cover transferring to middle vegetation cover.4. By comparative analysis of vegetation cover in 1990 and 2000 before transferring water in oasis, it shows that vegetation coverage decreased and vegetation degradated seriously since 1990 in Ejin oasis. It reached the worst state in 2000 in three times. After the water diversion of Heihe River vegetation had improved since 2000 in Ejin oasis. But the vegetation coverage in 2006 was not better than that in 1990. It indicates that the speed of improvement still not reach the speed of degradation. That fully shows the arduous task of transferring water and the lag effect in improving ecological environment. The intensity of transferring water should be strengthened.5. The study shows that vegetation coverage increased in Ejin Oasis. In addition that transferring water to Ejin oasis have a major impact on vegetation changes, other factors such as temperature, precipitation and ecological migrants, returning farmland to forest and grassland, reducing livestock etc. also played a non neglectable role.