Abstract: 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 of soil moisture content of sand dunes; (3) Shrubs intercept strongly atmospheric dust. The average silt and clay content of the shrub-covered dunes was higher than that of other dune types, which reveals that the shrubs are beneficial to the loamification and soil moisture conservation of sand dunes. Therefore, it is valuable to plant shrubs for preventing and controlling desertification in the Mu Us Sandy Land.

Key words: sand dune type, soil moisture content, particle size analysis, topographic position, Mu Us Sandy Land, Hengshan, Shaanxi province