关键词: 青海湖, 土地沙漠化, 驱动机制, 古沙丘活化

Abstract: Under influence of natural factors and the unreasonable human activities, the Qinghai Lake basin and surrounding regions are facing serious ecological and environmental problems such as sandy desertification, wetland shrinking, grassland degradation, and soil erosion. This paper analyzes sandy desertification status and its driving mechanism around the Qinghai Lake. The results show that widely distributed fossil dune is the sand supply of the modern sandy desertification. The grain size characteristics of mobile dune sand and fossil dune sand are very similar, and the relationship of inheritance and transformation between them are obvious. The turf surface which contained a dense growth of grass and its matted roots and underlying silty soil are the protective shell of loose fossil dune. Mechanical destruction of protective shell is the key step in formation of sandy desertification. The exposed loose sand is blown out by wind, forming of lateral concave pits which leading surface protective shell collapsed. With the expansion of wind erosion pit, aeolian activities intensified, leading the reactivation of fossil dunes and forming sandy desertification. Analysis shows that the subsidence of dunes and water erosion are the main factors that causing the destruction of turf layer. Other factors such as drop of water level of the Qinghai Lake, fluvial sediments, sand blown into the lake can increase area of sandy land, but these are only confined to someplace along the lakefront.

Key words: Qinghai Lake, sandy desertification, driving mechanism, reactivation of fossil dune