Abstract: Water is a main factor which limits agriculture and animal husbandry development, desert control and afforestation. Studying the water dynamics has theoretical and practical significance for afforestation under water balance condition. Based on the site observation in 1997, this paper studies the water content of aeolian sandy soil within 0~100 c m layer below the surface. The aeolian sandy soil samples are from shifting sand dunes, natural shrub lands of Artemisia ordosica and Sabina vulgaris, and planted forest lands of Salix psammophila and Pinus syvistris var. mongolica. During the whole growth period, the trend of water content in aeolian sandy soil is declinning from top to bottom. The moistur e content of mobile aeolian sandy soil is much stable with mean content about 3%, which is favorable for plant's growth. The water content in fixed and semi fixed aeolian sandy soil with plants growing on varies more greatly; the annual mean content is 1%~2%. The water content of aeolian sandy soil is mainly affected by precipitation, plant transpiration and soil evaporation. During the arid period from April to July and September to October, the vertical distribution of aeolian sandy soil moisture exists two distinctive layers: surface dry sand layer within 0~10 cm and active soil moisture layer within 10~80 cm. Under the shrubs of Artemisia ordosica, Sabina vulgaris and Salix psammophila, the water content within 0~50 cm layer where roots distribute thickly fluctuates in a greater range than that under the layer. But the contrary result is obtained in Pinus syvistris var. mongolica land. The aeolian sandy soil moisture reachs its maximum during the rain season(From July to August). Based on the seasonal variation of aeolian sandy soil moisture,it can be divided into three phase: the soil moisture lose phase from April to June and September to November; the refilling phase from July to August; the freezing water logged phase after August in this year and till April in the next year.

Key words: Aeolian sandy soil, Mechanical composition, Soil water content, Seasonal variation, Mu Us sandy area