THE PROBLEMS ASSOCIATED WITH PERMAFROST IN THE DEVELOPMENT OF THE QINGHAI-XIZANG PLATEAU
青藏高原开发中的冻土问题

About 54.3% area of the Qinghai-Xizang Plateau is underlain by permafrost. It is the largest in area and highest in elevation in the low and middle latitude regions. Since Pleistocene, the plateau permafrost experienced a series of changes following the alternate changes of glacial and interglacial periods. Especially during the past two decades, the degradation of plateau permafrost is becoming more obvious. The permafrost degradation will continue under the global warming trend. In order to set the strategy for the development of the western China, it is imperative to assess the problems associated with permafrost in the Qinghai0izang Plateau, to study the impact of anthropogenic activities on permafrost in lieu of climatic and environmental changes, and to predict possible changes in permafrost environment to meet the requirement of sustainable development of the Qinghai-Xizang Plateau. The major problems in the development of the Plateau are engineering geology and environment protection. The problems about engineering geology are mainly frost expansion caused by water movement and freezing in permafrost, and subsidence caused by thermal karst and deformation. These are the causes of all engineering geology problems in permafrost zone. The destructions of all kinds of structures in the permafrost zone are caused by frost heave and poor geological conditions. The ecosystems of the Qinghai-Xizang Plateau are very fragile and closely related with the permafrost dynamics. The vegetation communities of the permafrost zone in the Plateau gradually changed from temperate communities to younger ones adaptable to cold and arid environment following the rising of the Plateau. Because of the long period of adaptation to the Plateau environment, many plants developed a series of morphology cology characteristics to adapt the alpine environment. The internal structure exhibits many characteristics. Permafrost limits the moisture exchange between ground surface and the upper permafrost. This is the primary factor controlling the moisture regimes of the plant communities and wetland distribution in both time and space. The drastic and extensive periglacial process also produced different ecological effects. Since the 70′s, the plants colonial superiority increased and the biodiversity also increased following the degradation of permafrost. The combined effects enhanced desertification. The permafrost of the Qinghai-Xizang Plateau is very sensitive to changes in climateand ground surface conditions. Changes in permafrost directly affects hydrological processes. Permafrost is a special thick regional aquater. It separates the same aquatar into super ections and sub ections. It retards the direct hydrological interaction between the two sections and formed two totally different aquafers. The ground water of the Qinghai-Xizang Plateau can be divided into three basic types: aquafer above permafrost, aquafer below permafrost and talik. Water sequestration and rel