关键词: 自然环境演变, 风沙通道, 多源遥感, 阿拉善东南部

Abstract:

The research area, the southeastern part of Alxa, lies in the west of Inner Mongolia Plateau in China. It bounds Mt. Yabrai and Mt.Bayan Ul to the west and Helan Mountains and Yellow River to the east,connects Hexi Corridor to the south and Langshan Mountains to the north. The area includes Tengger Desert and Ulan Buh Desert. The well-known Jartai Salt Lake lies in Ulan Buh Desert. Topographically it is the connection part of Alxa Plateau, Loess Plateau and Qinghai-Tibet Plateau. It is also the transitional zone between the semiarid dry-grassland areas and arid-hyperarid areas.Its climate is arid and semiarid. This is the sensitive region of global change and is one of the sand storms most frequently hit areas in China. In the late Pleistocene, Tengger Desert and Jartai Lake were large broad fresh water lakes separately. In Tengger Desert, there were more than 400 lakes of different sizes. The Alxa Plateau had ever been such a geographical environment with many rivers and lakes. Due to the effect of the uplifting of the Qinghai-Tibet Plateau, the moisture laden ocean air current was blocked from entering in. This turns central-Asia into inland arid climate region, and its environment became deteriorated.The cause of the aridity is due to two aspects:First, the climate became dry, and the water of the lakes was strongly vaporized. So, the areas of the lakes turned smaller and smaller, and finally into dry basin and lacustrine sediments exposed to the ground to turn into desert under the wind erosion. Secondly, due to the funnelling effect, drifting sand from Yamaleike Desert in the west of Jartai and from Badain Jaran Desert in the west of Tengger Desert invades along the narrow passageway.That is a very important factor leading to desertification of the lake basin.In the arid and semiarid regions, the structure of the eco-system is very simple,which is liable to induce ecological calamities.Today the main problem in these areas is the invasion of the drifting sand and sandstorms.Therefore, based on studies of remote sensing images,relevant measures for improving the research area's ecological environment are identified as to block and fix the sand in the west, and to establish ecological protective belt in the east, to renovate and control sand encroachment in divided blocks. With these measures to harness ground surface environment, the invasion and expansion of the drifting sand, the occurrence and the intensity of the sandstorms from the area's surface can be controlled effectively. The prevention and control of the sandstorms of the area is of very important to the mitigation of the sandstorm calamity in Beijing.

Key words: physical environmental evolution, trajectory of drifting-sand, multi-source remote sensing, southeastern Alxa