Spatial Distribution Characteristics Of Soil Profile In The Slope-soil Basin Of The Southern Slope Of The Qinling Mountains

Xie-Yu River is located in Dan-Jiang-Kou reservoir water source protection areas of the National south-to-north water transfer project in Middle Route. Land reclamation and deforestation are so serious in the middle and lower reaches of this river in the early years that the situation of slopes, water and soil loss are terrible or more. Since the basin comprehensive management project implemented 2010, forest coverage rate is greatly improved and the ability of water conservation of forest vegetation is significantly improved. In this study, Xie Yu River Basin is divided into upper, middle and lower reaches of the three section,in each section, a typical slope was selected to collect soil samples. This research through the field acquisition of soil sample, indoor sample analysis for the basin 0?80 cm soil moisture data, soil bulk density, porosity, size composition, organic matter content, pH data, and through the statistical analysis software such as SPSS, GS+, CANOCO4.5, SAS to systematically explore the spatial distribution and variation law of soil moisture and the main factors which influence the spatial distribution in soil physical and chemical properties and other problems happened in the river basin of Xie-Yu River. This research is aimed at supplying science instruction for the water conservation, ecological environmental protection and agricultural activities in this basin still the whole Qin-ling Mountain area.From the perspective of the distribution characteristics of soil moisture in the different sections of this basin, soil moisture content between 7.81%?38.44%; soil moisture mean order for upstream (21.16%)> downstream (18.12%)> middle stream (17.46%). From the point of profile distribution, the average soil water content in each layer of 0-80cm was between 13.91%?22.29%, and the content of soil moisture in the upper reaches was greater than that in the middle and downstream reaches. All these illustrated that the capacity of the primeval forest in the upstream to conserve water is better than the man-made with secondary communities in the middle and lower stream.From different land-use types, in addition to the sort of slope farmland, average soil water content are arbor> shrub> grassland in the middle and downstream reaches, which show that the forest land's capacity to conserve water is better than grassland. Soil moisture profile characteristics in different land-use types show that the soil moisture of the slope farmland and grassland is related to the root system of the crops there.Semi-variable function analysis showed that the optimal semi variance model of 0-80cm soil layer averaged soil moisture respectively index model, spherical model, exponential model on the upper, middle and downstream reaches. Each reaches appeared strong spatial auto-correlation; space auto correlation distance is 24.7m,25.0m, 15.5m.0-80cm soil moisture profile semi-variation function analysis showed that the soil moisture of each layer showed a strong spatial auto-correlation.From the characteristics of the soil properties, the bulk density mean of the soil profile content between 1.13 g/cm3?1.34 g/cm3. The worst to improve the soil bulk density is the slope cropland, while the arbor forest is the best. Profile distribution shows that the soil bulk density will be increased with the increasing of soil depth. The total porosity mean of the soil profile content between 49.43%?55.85%; the effect of the shrubbery to improve the soil porosity is the largest, while the slope cropland is the lowest; the change characteristic of profile show that the soil porosity will be decreased with the increase of the soil depth. The size composition show that all kinds of land category are mostly composed with silt. The organic content of the soil profile distribute between 12.22%-88.02%; compared the organic content of the four kinds of profiles soil in different sections, slope cropland is the lowest, then is the grassland, while slope cropland,arbor forest and grassland are the largest in the upstream region, shrubbery is the lowest in the downstream region, the pH of the soil profile content between 5.75?6.77; the order of the pH in different sections is shrubbery>slope cropland>arbor forest>grassland. The linear trend show that the soil moisture decreases with the increasing of the bulk density, and increases with the increasing of the porosity. The soil moisture also has a positive correlation with clay, silt and organic content, and a negative correlation with sand content and pH.From the CCA ordination between soil physical and chemical properties and soil moisture, the order of the affection of the analyzed soil physical and chemical properties to the soil water content is silt>clay>organic content in the upstream region, organic>grain-size content in the midstream region, bulk density>porosity>organic content in the downstream region. Therefore, the organic matter content in soil, particle size content can be the main reference factor in the study of soil moisture profile about the physical and chemical property.Using SAS multiple regression analysis to establish the prediction model of soil water content in each section, the accuracy of the model is verified by the experimental data of the sample point. The accuracy of prediction model in the upper reaches is more than 89%, middle reaches is more than 84% and downstream area is more than 86%, the accuracy of prediction model is higher.