阿拉善东南部自然环境演变与地面流沙路径的分析

阿拉善东南部包括腾格里和吉兰泰两区。腾格里和吉兰泰两区在晚更新世均是一个湖域广阔的淡水大湖。之后 ,吉兰泰大湖和腾格里大湖在封闭状态下 ,一方面因气候转为干旱、蒸发致使湖域减小直至完全干涸 ,露出的湖底在风的吹蚀作用下形成沙漠 ;另一方面在“狭管效应”作用下 ,由吉兰泰西部来自雅玛雷克沙漠和在腾格里西部来自巴丹吉林沙漠的风吹沙沿着地形上狭窄通道的侵进是加剧这两个湖盆沙漠化的另一个重要因素。对此 ,基于遥感的研究提出了研究区西缘挡沙固沙 ,建立生态保护带 ,区内分块治理、有效控制流沙的侵进和扩张以及通过改善下垫面性质来控制沙尘的发生与强度 ,逐步改善生态环境的措施。研究区风沙的治理 ,对于缓解京津沙尘灾害具有重要的意义。

The physical environment evolution and trajectories of drift sand in southeastern Alxa of China

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.