Abstract: Applying the methods of deducing time series from vegetation space alignment,we analyzed the spatial and temporal variation features of soil moisture under artificial Caragana microphylla shrubs built in1984,1987,1995,1999. The results showed that affected by mechanical composition of mobile sandy dunes,the soil of sandy land was mainly composed of sandy particle,and the particles of >0.01 mm were accounted for 97%. The withered moisture was 1.55%. The field waterhold capacity was 5.5%,and the available moisture storage was 3.95%. With the increase of the dominance of fix sand vegetation,the moisture content of soil under artificial Caragana microphylla shrubs was decreased. The soil moisture of vegetation built in1984 was lower than that built in1999. The soil moisture conditions of four stages vegetation were continued depressing from April to June in a year,the lowest point presenced in June,and then gradually increased from July to October. The vertical change of soil moisture showed the tendency of increasing with soil depth. The soil moisture decreased by the degrees of early built vegetation (1984,1987). Especially in70 cm soil depth,the moisture content of soil decreased obviously. Caragana microphylla shrubs absorbed water and aggravated the shortage of soil moisture content near the root system,which affected the component of vegetation in Caragana microphylla shrubs .The species of herbaceous plants and annual plants increased during the growth of Caragana microphylla shrub.

Key words: Caragana microphylla, Soil moisture, Kerqin sandland, thermal diffusion probe, sap flow rate, environmental factor, time lag characteristics