Studies On Soil Moisture Content Under Different Land Uses In Sunjiacha Basin

In the study, soil moisture characteristics in the SunJiaCha basin were measured by the data from1979to1986and in2011, and analyzed by classical statistics and geostatistics. The result as that:(1) Soil moisture under semi-arid condition has a relationship with rainfall, evaporation, terrain and land use. The variability of soil moisture decreases with an increase in soil depth and rainfall. Soil moisture can be divided into three levels according to standard deviation(S) and coefficient of variation(Cv) of season change: Active layer (Cv>30%, S>3).Secondary active layer (Cv=10%～20%,S=1～3) and Relatively stable layer (Cv<10%, S<1). The dynamic changes of soil moisture in depth of1.20～1.40m are affected by seasonal climate significantly, soil moisture in depth of1.40～1.60m are affected by seasonal climate indistinctively, soil moisture have temporal stability of the spatial distribution characteristics in the same year when soil depth is more than1.60m.(2) Soil moisture has obvious difference with spatio-temporal change in depth of1.80m under different land-use and hydrological years in the semi-arid loess. In the same conditions of precipitation and other conditions, soil moisture content of agriculture slope are significantly higher than the wasteland slope.(3) Spherical model fits better to vertical distribution of soil moisture under different land-use type in wet year. Spherical model of soil moisture only fit good in terrace and woodland in normal year and dry year. The space distribution of soil moisture in agriculture slope and wasteland slope has strong random.(4) Soil moisture is strongly influenced by rainfall and its spatial and temporal distribution in semi-arid loess. Soil moisture in different layers show concussion, the surface layer is low in winter and spring, with the influence of temperature and rainfall, surface soil moisture content higher than deep soil after summer.(5) In the SunJiaCha basin, compared soil moisture content:Terrace(13.3%)> Woodland(11.1%)>Agriculture slope (9.9%)> Wasteland slope(8.2%).Soil moisture of shrub land in surface layer(10.4%) was higher than the wasteland(9.2%). Soil moisture content of shrub land (6.7%) was lower than the wasteland (7.2%) in the deep layer. The average water content of pine plains(7.8%) was higher than almond(6.4%). Planting bushes and the right kind of tree species can reinforce the conservation of water and soil. Compared soil moisture content of different site types: shady slope>sunny slope. Growing suitable autumn crop such as potato and grass in wasteland with good soil can improve water use efficiency in the gentle slope area. (6) Compared soil moisture content of different topography and physiognomy position:Ditch (17.3%)> Beam (12.4%)> Mizobe (11.1%)> Gully (10.1%). Trees and grasses should choose fitness species, and modern natural ecological balance should be stayed reasonable. Plants were under long period of drought in beam and gully. Developing agriculture require advanced technology of collecting water.