Study On Three-dimensional Spatial Heterogeneity Of Soil Salinity In The Yellow River Delta

As an important reserve land resource area in China,the Yellow River Delta has been affected by long-term salinization,becoming a typical area of soil salinization in coastal areas.Soil salinization seriously affects agricultural production in the Yellow River Delta region and restricts the effective use of land.Understanding the distribution pattern of soil salinity in the region and exploring the spatial variation characteristics of soil salt content provides a reference for the governance of soil salinization in the Yellow River Delta.In this paper,Kenli District,Dongying City,a typical area of Yellow River Delta,is selected as the research area.Using multi-source remote sensing Sentinel-2 and Landsat-9satellite data,various environmental factors such as topography,humid and hot environment,soil physical attributes,etc.are extracted,and the factors that affect the maximum spatial differentiation of soil salinity are screened.With the help of three-dimensional Kriging interpolation method,a three-dimensional spatial interpolation model of soil salinity in the Yellow River Delta is established,Analyze the spatial differentiation characteristics of soil salinity.The main research findings are as follows:(1)Analysis of main factors affecting spatial differentiation of soil salinity in Yellow River DeltaThrough preliminary analysis of all 37 environmental factors,seven environmental factors,namely,surface temperature,distance from point to coastline,soil bulk density,PH,elevation,underground water conductivity and soil clay content,were screened out,which are related to soil salinity and meet the collinearity conditions.Then,the factor detector in the geological detector method was used to analyze the screened factors,The results show that the soil bulk density factor is the environmental factor that has the greatest degree of explanation for the three-dimensional spatial differentiation of soil salt,taking into account the differences in vertical distribution of soil salt.(2)Spatial variation of salt content in different soil layersOverall,the distribution of surface salinity shows a trend of gradual increase in soil salinity content from the southwest inland to the northeast coastal areas,and the degree of soil salinization gradually increases.The fitting analysis of salt content and coastline distance shows a logarithmic relationship and a significant negative correlation.Overall,soil salt content decreases with the increase of coastline distance,especially in the surface layer(0-20cm)within30km from the coastline where the trend of soil salt reduction is more intense.The scope of action of the ocean is limited,with a greater impact on surface soil salinity within 30 kilometers,and a weaker impact on the ocean as it is further away.In February,there were some non-saline soils in the southwest region,with light,medium,and severe saline soils distributed in the central and central southern parts of the region.Saline soils were mainly distributed in the north and northeast.In May,the salinization degree of the entire region was above moderate,and the vast majority of the area was saline soil,with a small portion of medium and severe saline soils distributed in the southwest direction.Compared to the ten layers of soil,each layer exhibits a distribution pattern of high in the northeast and low in the southwest.Affected by the dilution of water flow near the Yellow River,the salt distribution shows local variations that protrude towards the direction of water flow.As the soil deepens,the proportion of saline and non-saline soils decreases,while the proportion of mild,moderate,and severe saline soils increases.(3)Changes in three-dimensional spatial volume of soil salinitySoil salinity exhibits significant vertical heterogeneity and significant spatial variability.The salt content of the soil gradually decreases from the surface to the bottom layer,and vertically,the salt content in the surface layer is the highest,showing an overall "surface aggregation" distribution.The section from the southwest inland to the northeast coastal direction of the research area shows a clear pattern of increasing salt content from southwest to northeast.This paper uses the correlation coefficient method,collinearity analysis and geographical detector method to find the environmental factors that explain the maximum degree of soil salinity differentiation,and comprehensively analyzes the spatial differentiation law of soil salinity from two perspectives of each soil layer and the three-dimensional distribution map of soil salinity,providing decision-making support for the control of soil salinization in Yellow River Delta.