Strengths Of Soil Sodification Based Remote Sensing Inversion In The Wuyuer River And Shuangyang River Basin

With the global warming,the sustained growth of global population and rapid development of economy,the environmental problem which is faced by human beings becomes increasingly prominent and tends to be serious.Soil salinization and sodification have become very important environmental problems,which have great harm to ecological environment and agricultural production.Moreover,soil alkalinity and salinity have severely harms to the sustainable development of ecological environment and agriculture.The formation and development of soil salinization and sodification are resulted from many nature and human-related reasons.The variation characteristics of soil salinization and sodification are in space-time.The damage and complexity of soil salinization and sodification have have caused high attention and research from all over the world.Wuyuer River and Shuangyang River Basin is located in the Songnen Plain,Northeast China,which is a typical black soil region.Its upstream area is one of the important commodity grain bases,and the downstream area is in the wide wentland and lakes.It has important theoretical significance and practical value for prevention and cure of soil salinization and sodification and ecological environment to detect the characteristics and strengths of soil salinization and sodification;to reveal the spatial distribution of soil salinity and alkalinity quantitatively with remote sensing data in the study area;to reveal the influence resulted from nature and human-related factors on the strengths of soil salinization and sodification quantitatively;as well as to reveal the relationships of nature and human-related factors.In the current study,the statistical analysis of topsoil revealed the physico-chemical characteristics and strengths of soil salinization and sodification in the basin.The sensitive bands to soil alkalinity and salinity were acquired with correlation analysis based on the physico-chemical and lab spectral data of soil.The stepwised models and PLSR models based on lab spectral data were constructed to estimate the strengths of soil salinization and sodification quantitatively.When the stepwised models were applied to Landsat 8 OLI images and the PLSR models were applied to HSI images respectively,the maps of different degrees of soil alkalinity and salinity cover entire and part basin were acquired.The quantitative influence of nature and human-related factors on strengths of soil salinization and sodification and the relationships between factors were revealed.Main results are as follow:(1)There are alkaline soil,neutral soil and acid soil in the basin.The soil alkalinity so strong that sodic soil could be found occasionally.There are non-affected soil,slightly saline soil,moderately saline soil and highly saline soil in the basin.But the saline soil is rare and the non-affected soil is dominant.The saline soil is highly alkaline soil.The dominant soil soluble salts were Na2SO4,Na HCO3 and Na2CO3 in the study area.(2)The correlation coefficients in VIS and NIR bands were highest between soil p H,EC,CO32-,Na+and the raw spectral reflectance.These suggested that these bands were sensitive to soil p H,EC,CO32-and Na+.These bands were optimal spectral wavelengths and had potential to estimate soil alkalinity and salinity quantitatively with models.(3)The calibration and validation of the quantitative models for estimating strengths of soil salinization and sodification performed better.VIS and NIR bands had more important contribution to the estimating models.The result was similar with the analysis of spectra.These indicated VIS and NIR bands were the optimal wavelengths in estimating strengths of soil salinization and sodification.(4)When the stepwised models and PLSR models were applied to multi-spectral images and hyperspectral images respectively,the validation of the map inversion was satisfactory.According to the inversion of Landsat 8 OLI images,the alkaline soil distributed widely in the basin with half of total area.The alkaline soil distributed in the lowlands near river downstream and wetland.But a few saline soils distributed in the lowlands near river downstream and wetland.(5)The natural factors and social factors had different risk on the variation of soil alkalinity and salinity in the study area,including terrain(DEM),spring temperature,precipitation,evaporation,ground temperature(0cm),groundwater depth,population density and cultivated land area percentage.Terrain(DEM),spring temperature and ground temperature(0cm)had high risk on the variation of strengths of soil salinization and sodification.They were the dominant factors which made greater contribution to the variation of soil alkalinity and salinity.(6)Compared with other factors,the statistically difference between terrain(DEM)and the variation of strengths of soil salinization and sodification was significant.The Interactive impact of paired natural factors were non-linear enhance and bi-enhance.The Interactive impact of paired social factors was bi-enhance.The Interactive impact between natural factor and social factor were bi-enhance.The Interactive impact of paired natural factors was the domiant impact on the variation of strengths of soil salinization and sodification.The Interactive impact of natural factors will be enhanced by the social factor when the paired natural factor and social factor work together.