塔克拉玛干沙漠灌草丘的发育特征及环境意义

对灌草丘的发育条件及沉积特征的研究表明，塔克拉玛干沙漠地区的灌草丘形成在绿洲受风沙入浸，由水沉积转为风沙沉积过程中，气候变化对灌草丘的发育未产生重要影响，但流水在其中起了决定性作用。灌草丘开始发育之后，可以依某一速率持续增长，也可能被埋没（主要是风沙流），或被侵蚀夷平，但部分灌草丘在沙漠的发展过程中保存达数千年之久。有限的测年数据及地表景观显示灌草丘发育的阶段性，实际上也是沙漠发展的阶段性。

The Environmental Significance of Vegetation Cones of the Taklimakan Desert,China

egetation cones of the Taklimakan Desert are as a result of advance of drifting-sand flow in a large scale.They grow while both the plants are growing well and the dirfting-sand is accumulating constantly.Because of limited precipitation,most species of the plants in the desert only reproduce along with migration of the river channels,and germination of seeds and roots and stems parts are all in the post-flooding season(latter fall),but non in the rainfall season(summer).The plants keep alive only on the channel flooding and groundwater.In addition,geological data indicate that there has not been a climatic suitabletime for plant to develop in the desert.When drifting-sand flows into vegetated-lands(floodplains,terraces and swampland,etc),the ground surface structure(or pattern) is changed.Probably vegetation cones start developing.14C dating,geomorphology and landscape show that the cones of the Taklimakan Desert developed in different stages which are main expansion of the desert.Preliminary age dating study states that there are at least 3 stages of the cone development,which began at 4500a B.P.,3000a B.P.and 1500a B.P.,and expresses the important events of the desert development since the last 5000 years.The vegetation cones may meet one of the three different geologic processes,(a)accumulation,the cones keep growing with their primary structures 1(b)burying,the cones are buried by drifting-sand,or other deporsits without their primary structures;(c)erosion,they are eroded by wind or other process.No matter whether the accumulation,the burying or the erosion occurs,the development of the cones is a degradation process of oasis.The later two processes are not the development,but evolution of the cones.Final produsts of the above processes are moving sand dunes.