Assessment Of Soil Salinization Ecological Environment Change In The Ebinur Lake Basin Using Remote Sensing Technology

Soil salinization and secondary salinization severely restricts the development of social economy of oasis,and the constantly threatening of ecological system stability,is one of the main ecological environmental problems faced by all countries all over the world.The main causes of soil salinization are very poor natural conditions,low rainfall,strong evaporation,high groundwater level,salt accumulation,and difficult to output.The problem of soil salinization has become one of the important problems of ecological environment in Ebinur Lake region.The monitoring of salinization is urgent.Therefore,accurate,scientific and rapid access to the degree of salinization change,spatial distribution,water and salt transport of information,provide an important basis for quantitative monitoring and prediction of soil salinization and it is of great significance to harness,utilize and plan soil salinization in Ebinur Lake area.Based on the measured data,using statistical analysis and Geostatistical analysis,the characteristics and spatial distribution of soil salinization in the Ebinur Lake area were studied.The sensitivity of different indexes to soil salinity was studied by means of remote sensing image as data source,combined with measured EC data;select the most sensitive to soil salinity index,build the soil salinization ecological environment index of the Ebinur Lake area,The ecological environment of soil salinization area is monitored rapidly,quantitatively and objectively,and provide a new idea for the treatment of soil salinization in the Ebinur Lake area.The main conclusions are as follow:?1?Descriptive statistics was used to analyze the physical and chemical properties of soil samples in Ebinur Lake area,and the apparent aggregation of soil salinization was obtained.0-10 cm,SSC was higher,EC was bigger.The soil salinity ion content from high to low are Na⁺>Ca²⁺>K⁺>Mg²⁺ according to the cation,SO₄^2->Cl^->HCO₃^-according to the anion.The composition of surface soil salt is mainly classified as sulfate and chloride salt according to anions and mainly classified as sodium salt and calcium magnesium salt according to cations.The average value of pH in soil layers was between 8.16-8.49 and the soil is alkaline.Soil profiles are mainly divided into three types.Through the analysis of redundancy and correlation analysis,it is concluded that EC and soil salt content have a high correlation.0-10 cm,Soil salinity and seven salinity ions have passed the significant test,and the correlation is strong.pH is more relevant to HCO₃^-and Na⁺.?2?Using the semi-variogram analysis,it is concluded that the spatial correlation of pH,EC,HCO₃^-,SO₄^2-,Na⁺ and Mg²⁺ is less than 0.25,and it has very strong spatial correlation.The spatial correlation of K+ and Ca²⁺ was 0.342 and 0.478,respectively.It was affected by random factors and structural factors,belonging to middle spatial correlation.Cl-is weak spatial variability intensity.The best theoretical model of pH,SO₄^2-,Na+ and Ca²⁺ is Exponential,and the best theoretical model of EC,HCO₃^-,K+ and Mg²⁺ is Spherical,and The best theoretical model of CI-is Linear.From the Kriging interpolation map can be seen in distribution of surface soil salinity of Lake Ebinur Lake area and EC is roughly the same,in the northeast and southwest of lake is higher.pH belongs to weak spatial variation,and its distribution is more homogeneous.The distribution law of the ion content shows a decrease from the lake area to the outside.?3?Based on Landsat8 OLI data study extracted the 5 kinds of salt index,four vegetation index,surface albedo and humidity index,and combination with soil conductivity,using the method of curve estimation,analyzed the response of different index on soil salinity.The results show that Salinity index are significantly correlated with soil conductivity,and the degree of sensitivity to salinization is high.Among them,the SI3 index based on Cubic model showed the best performance in salt index,R2=0.713,Compared with other vegetation indices,the EVI index is most sensitive to the soil salinization in the Ebinur Lake region,and the nonlinear model Cubic model performs best,R2=0.784.The best model of surface albedo is the Cubic model,R2=0.665,with the best correlation.The fitting effect of Cubic model based on WI index is relatively good,R2=0.735.?4?Principal component analysis?PCA?method was introduced to couple the four indicators?salinity,surface albedo,vegetation coverage and wetness?,build soil salinization ecology index?SSEI?.The result shows that there is a significant relationship between SSEI and salt content observed?R2=0.7512?.Through PCA ananlysis shows that the first principal component appears stable and its share of all indicators is greater than 75%.?5?The SSEI index is divided into 5 grades: bad,comparatively bad,medium,good and excellent,the area of good and great had decreased 8.78% during 1990-2015,the area of bad,comparatively bad,medium had increased 8.78%,which shows the ecology environment has not improved in Ebinur Lake region.Change map during 1990-2015 shows that the desert area without influencing by human activities still keeps a poor level,and the ecological problem is still very serious.The function of artificial oasis has been improving.