毛乌素沙地南缘沙丘水分的时空分布特征

Preliminary Study on the Spatiotemporal Distribution of Moisture Content in Sand Dunes in the Southern Marginal Zone of the Mu Us Desert

在2003年4-10月，通过对毛乌索沙地南缘沙丘0-100cm沙层水分含量的定点观测，结果表明：不同季节水分含量为秋季〉春季〉夏季，春、秋季节为沙丘水分的积累期，夏季为水分亏缺期；沙丘水分垂直变化小，近地表水分含量低，普遍存在一层干沙层，厚度约为10～20cm。沙丘各部位水分由高到低依次为丘间〉背风坡〉迎风坡〉丘顶，夏季由于地表出现干沙层，故迎风坡水分高于背风坡。

The study area （ 37°38＇ 42＂- 37°42＇ 42＂N, 108°50＇54＂-108°58＇00＂E） marginal zone of the Mu Us Desert, where it to the semiarid climate, and is located in the southern the annual precipitation is 394.7 mm, in which the summer precipitation occupies 57% ; the annual evaporation is as high as 2 484.5 mm, and the annual-average aridity index is 2.3; the days of occurring strong winds varies in a range of 20 -40 days, especially strong winds occur frequently in spring, the average monthly wind speed is 4-5 m/s, and the maximum wind speed varies in a range of 20-25 m/s; the vegetatin coverage is low, and the vegetation is mainly composed of Artemisia blepharolepis , Agriophyllum squarrosum , Corispermum puberulum , Psammochloa villosa, Salix psammophylla, etc. Based on the stationed observation during the period from April to October 2003, in this study the spatiotemporal characteristics of moisture content in sand dunes in the southern marginal zone of the Mu Us Desert are researched. The results are as follows： （1） There is a dry sand surface layer, its thickness varies in a range of 10-20 cm, and the variation of moisture content in depth of 20-100 cm in sand dune is not so significant; （2） The seasonal dynamic change of moisture content in sand dune can be divided into two stages, i.e., the accumulating and consuming stages, and the moisture content is Mc autumn 〉 Mc spring 〉 Mc summer; （3） The moisture content in sand dunes is in a sequence of windward 〉 leeward 〉 dune top 〉 dune bottom, and the moisture content decreases from the bottom to the top of sand dunes; （4） The soil moisture content of windward slope is higher than that of leeward slope in summer because of the dry sand surface layer.