Abstract:

Study on the spatial differentiation of soil water and salt is an important basis for the prevention and improvement of soil salinization， and also an important foundation for the development and utilization of saline land resource. At a watershed scale， relatively few studies have been conducted on the spatial differentiation of soil water and salt under different land-use types such as forest land， grassland， cropland， saline land and desert in the Shiyang River basin， which can hardly support the improvement and utilization needs of saline land under the changing environment in the new period. In this study， the spatial differentiation of soil water and conductivity in the Shiyang River basin were studied using geostatistical and traditional statistical methods， and the effects of different land-use types on soil water and salt distribution were analyzed. The results showed that the soil water content in the Shiyang River basin demonstrated a trend of high in the southwest and low in the east and west， and gradually increased from 8.75% in the surface soil layer to 10.19% in the deep soil layer. Soil conductivity showed a trend of low in the southeast and southwest and high in the northeast and northwest， and the area of moderately and heavily saline and saline soils accounted for 56.55% of the total watershed area. The highest average water content was exhibited in forest soils （21.08%）， followed by arable land （15.60%）， saline land （12.40%）， grassland （6.98%）， and desert （1.60%）. The highest average soil conductivity was found in saline land （8.55 dS·m^-1）， followed by grassland （1.28 dS·m^-1）， desert （0.51 dS·m^-1）， cropland （0.48 dS·m^-1） and forest land （0.18 dS·m^-1）. Land-use type had a significant effect on the vertical distribution of soil water and salt， and soil moisture was significantly and positively correlated with elevation， vegetation biomass， cover， and density， while significantly and negatively correlated with soil bulk density. There was no significant correlation between soil moisture and conductivity in forest land and grassland， while significant positive correlations were detected in cultivated land， saline land and desert showed， indicating that the dependence of soil salinity on soil moisture increased from the upstream to the downstream of Shiyang River basin.

Key words: Shiyang River basin, soil moisture, soil conductivity, land-use type, spatial differentiation