古尔班通古特沙漠沙垄表面的稳定性与顶部流动带的形成

古尔班通古特沙漠是我国惟一受西风气流控制的沙漠,也是我国最大的固定与半固定沙漠。个体沙垄表面的稳定程度从基部至顶部呈现明显的差异。通过分析沙丘的粒度组成、水分动态、土壤植被及生物结皮等下垫面因素的垂直变化,特别是对沙丘表面蚀积过程的实地观测和研究,探讨古尔班通古特沙漠固定、半固定沙垄表面的稳定性和顶部流动带的形成。

Stabilization of Dune Surface and Formation of Mobile Belt at The Top of Longitudinal Dunes in Gurbantonggut Desert, Xinjiang, China

Gurbantonggut Desert,located in Junggar Basin in north Xinjiang,with an area of 48 000 km²,is the second largest desert in China.Affected by the west current,fixed and semi-fixed dunes are the main types.There is a mobile belt at the top of dune,which has aroused the concern of many researchers.In this paper,based on analysis of the main factors affecting the vertical variations of dune surface stabilization,especially on field measurement of erosion and deposit process,the stabilization over the dune surface and the formation of mobile belt are discussed and some results are obtained.(1) Generally speaking,fixed and semi-fixed dunes in Gurbantonggut Desert are characterized by natural environment.The vertical variation of stabilization on dune surface is mainly affected by some factors,such as composition of sand materials,soil type,water content,plant coverage and the distribution of soil microbiotic crust.The ability of soil resisting wind erosion various at different parts of dunes,which leads to the spatial change of mobile degree on dune surface.The research shows that,from the bottom to the top of dune,there is a change of sand activity from weak to strong.(2) In fact,the mobile belt on dune surface is the area with frequent deposition and erosion,a width of 10~40 m at the top of longitudinal dunes.Erosion area exists at windward slop and deposit at leeward in general,both of them happen alternately at one part of dunes.The intensity of sand deposit and erosion is controlled by the wind regime and ground surface condition.The dynamic pattern of dunes in Gurbantonggut Desert is that the sand particles at the top of longitudinal dunes are transported alternately from one side to the other and generally move forward along the ridge,while the base of dune keeps on unchanged.