中文摘要：

通过对横山县境内毛乌素沙地东南缘的实地考察,根据植被类型和植被覆盖度,将沙丘分为裸露流动沙丘、灌木覆盖沙丘、乔木覆盖沙丘,分别在各类沙丘不同地貌部位实施4 m深度钻孔取样,并进行含水量测试和粒度分析,研究沙地土壤含水量变化。结果表明：对于垂直方向0～4 m深度的沙地、灌木和乔木覆盖沙丘平均含水量变化为：丘间洼地〉迎风坡〉背风坡,而裸露流动沙丘平均含水量变化为：丘间洼地〉背风坡〉迎风坡;不同类型沙丘在各地貌部位不同层段含水量变化差异明显,变化趋势不统一。沙丘的地貌部位相同,地表的植被类型和覆盖度差异是影响沙地土壤含水量的重要因素,测试结果显示,迎风坡含水量为：灌木覆盖沙丘〉乔木覆盖沙丘〉裸露流动沙丘;背风坡含水量为：灌木覆盖沙丘〉裸露流动沙丘〉乔木覆盖沙丘;丘间洼地含水量为：灌木覆盖沙丘〉乔木覆盖沙丘〉裸露流动沙丘。灌木覆盖沙丘土壤含水量变异系数最大,水分含量在不同层位波动较大,裸露流动沙丘和乔木覆盖沙丘含水量波动差异较小。沙丘上生长的灌木和乔木明显地改变了沙丘含水量的变化特征,灌木比乔木对沙丘含水量及其垂向变化的影响更显著。灌木对地表大气中的粉尘有较强的拦截能力,灌木沙丘平均的粉砂和黏土含量高,灌木的覆盖有利于沙地的土壤化进程和保持沙地水分,在沙地绿化过程中,应充分考虑灌木植物的作用。

英文摘要：

The study area is located in the southeastern marginal zone of the Mu Us Sandy Land,and it is a semiarid climate area with annual precipitation of 394.7 mm.Based on the investigation in the study area in late-April 2009,the sand dunes were divided into bare migratory dunes,shrub-covered dunes and tree-covered dunes according to the vegetation types and vegetation coverage on the sand dune surface,and the samples of drilling holes of 4 m in depth at different topographic sites of the dunes were taken for analyzing the change of soil moisture content and soil granular properties of the sand dunes.The results are as follows：（1） Average soil moisture content at depth of 4 m was different from different dune types,that of the shrub-covered dunes and tree-covered dunes was in an order of dune intervale windward slope leeward slope,but that of the bare migratory sand dunes was in an order of dune intervale leeward slope windward slope.Furthermore,the variation of soil moisture content at different depth of each dune type was different,and that of shrub-covered dunes at different depth was more significant than that of the tree-covered dunes and bare migratory dunes;（2） Vegetation types and surface vegetation coverage affected the variation of soil moisture content of dunes at the same topographic positions of different dune types.Results of the test show that the soil moisture content on windward slope was in an order of shrub-covered dunes tree-covered dunes bare migratory dunes,it on leeward slope was in an order of shrub-covered dunes bare migratory sand dunes tree-covered dunes,and it at dune intervale was in an order of shrub-covered dunes tree-covered dunes bare migratory dunes;the variation coefficient of soil moisture content of shrub-covered dunes was higher than that of other dune types,the soil moisture content of shrub-covered dunes at different depth fluctuated more obviously compared with that of other dune types,and the shrubs and trees growing over the sand dunes affected obviously the change o