Abstract:

In the Minqin area,Gansu Province,China,the climate is dry,water resources are scarce,and the ecology is fragile.Over the long history of human development,the land use types and spatial structures of the oasis have undergone many changes,which in turn have affected the stability of the oasisdesert ecosystem.The soil water and salt characteristics have resulted from the combined effects of local natural conditions (e.g.,climate,topography,hydrogeology,and vegetation) and human activities (e.g.,unreasonable irrigation systems,overgrazing,and large reclamation).Unreasonable distribution of soil water and salt will directly lead to soil salinization and even to desertification,which will seriously affect the living environment and human living conditions.Therefore,preventing soil salinization and protecting existing land resources are important tasks for the sustainable development of human society.This study takes the downstream area of the Shiyang River Basin,Minqin Oasis,as a research area; through field sampling,field investigation,and experimental analysis,it is understood that there are significant differences in the soil water and salt characteristics for different land use types.The soil moisture content is generally low and ranges 5.35%-20.58%.The average salt content is 47.02 g·kg^-1 and the degree of salinization is severe.Both the soil water and salt contents are moderately variable,thus indicating that they are susceptible to climate,topography,hydrogeology,and human activities.The vertical distribution of soil water and salt under different land use types is significantly different.The variations of soil water content in the vertical direction are more complicated but the salt content mainly appears as “surface accumulation” and “oscillating” in the vertical direction.The degree of variation in soil salinity is obviously greater than the degree of variation of water content.This indicates that the spatial dependence of soil salinity is greater than the soil moisture content.The variations of surface soil water and salt are larger,indicating that the surface soil water and salt levels are susceptible to external factors (such as climate,terrain,and human activities).However,as the depth of the soil layer increases,the effect of external factors gradually weakens,thus resulting in a gradual decrease in the intensity of the variations in soil water and salt levels in the vertical direction.The spatial distribution of soil water and salt in each soil layer in the study area is in the form of strips.The soil moisture content of Minqin Oasis is generally high in the west,low in the east,high in the south,and low in the north,while the soil salinity shows a trend of high in the north,low in the south,high in the east,and low in the west.

Key words: Minqin Oasis')">

Minqin Oasis, soil moisture, soil salinity, spatial distribution