Spatial Distribution Patterns Of Soil Water,Salt And Nutrient Content In The Grass Lake Area Of Jiayuguan City And Its Influencing Factors

The soil nutrient is the basis for maintaining the function of wetland ecosystem,water,salt content,topography and vegetation status are important factors affecting soil nutrient content and its distribution pattern.they interact with each other,which in turn affects the formation and evolution of wetland vegetation patterns,and ultimately affects the structural stability and functional health of wetland ecosystems.Wetlands are an important part of the arid zone and are critical to the sustainable development of the region and are extremely sensitive to changes in the climate,therefore,to understand the spatial distribution pattern of soil water,salt and nutrients in wetland and its relationship with topography and vegetation status,reveal the environmental adaptation mechanism of wetland plants and the maintenance mechanism of wetland ecosystem structure and function,it can provide a basis for effective conservation of soil nutrients and efficient use of resources in wetlands.This paper takes the Grass Lake wetland in Jiayuguan City and its surrounding areas as research objects,The Geostatistical method and GIS technology was used to establish the theoretical model of soil nutrient variability in five different landform types(swamp,salt marsh,salt marsh and dune overdraft,dune,Gobi),and according to the vegetation cover conditions(high,medium and low)of three Calamagrostis Pseudophragmites single dominant species patches,the variation function theory model was established for soil(0~90cm)Water and salt content and vegetation coverage.the spatial distribution characteristics of soil nutrient of different landform types and soil water and salt content and vegetation coverage of three different vegetation cover conditions Calamagrostis Pseudophragmites single optimum population patches was established by the Kriging interpolation method,The spatial autocorrelation relationship and degree of soil nutrient,soil water and salt content and vegetation coverage were determined by Moran I coefficient,The correlation between soil nutrient and topographic factors(altitude,slope,aspect),spatial heterogeneity of soil water and salt content and vegetation coverage and their interactions were further determined.The results were showed as follows:a)The soil indexes of the Jiayuguan Grass Lake wetland area analyzed in this study are in line with the normal distribution,The coefficients of variation from large to small are conductivity(133.98%)> water content(123.54%)> available potassium(75.33%)> available phosphorus(43.55%)> nitrate nitrogen(30.47%)> ammonium nitrogen(32.31%)> pH value(7.41%),Among them,both conductivity and water content show strong variation,the available potassium,available phosphorus,nitrate nitrogen and ammonium nitrogen all showed moderate variation,and the pH value showed weak variation;The spatial autocorrelation intensity of soil nutrient from high to small is fast-acting potassium(0.6126)>effective phosphorus(0.3675)>nitrate nitrogen(0.3142)>ammonium nitrogen(0.2997),indicating that the spatial aggregation of available potassium is stronger and the ammonium nitrogen is the weakest;The spatial autocorrelation intensity of other indicators from high to small is water volume(0.4826)> bulk density(0.4649)> conductivity(0.2857)> pH value(0.1343),indicating that the spatial agglomeration of water content is stronger and the pH value is the weakest.b)Spatial analysis shows that the pH value of the Grass Lake wetland area in Jiayuguan City from high to small is inland salt marsh-sand dune transition zone > inland salt marsh > sand dune > herbaceous marsh > Gobi,but all are alkaline;Soil conductivity from large to small is inland salt marsh > herbaceous marsh > Gobi > inland salt marsh-sand dunes transition zone > sand dune;Soil water content from large to small is herbaceous marsh > inland salt marsh > inland salt marsh-sand dune transition zone > Gobi > dune;Soil bulk density from large to small is sand dunes > Gobi > inland salt marsh-sand dune transition zone > inland salt marsh > herbaceous marsh;Soil nutrients are generally characterized by high in the west and low in the east,The contents of ammonium nitrogen,nitrate nitrogen and available potassium were as follows: herbaceous marsh > inland salt marsh > inland salt marsh-sand dune transition zone > Gobi > sand dune,and the effective phosphorus content was overall expressed as herbaceous marsh > inland salt marsh > inland salt marsh-sand dune transition zone > sand dune > Gobi.c)Through correlation analysis,it was found that the soil salinity,water content and bulk density are important factors affecting soil ammonium,nitrate nitrogen and available potassium,but the effect on soil available phosphorus is relatively small,the content of ammonium,nitrate and available potassium in soil increased with the increase of soil salinity and water content,and decreased with the increase of soil bulk density;The soil nutrient and slope showed a negative correlation,and the available potassium showed a significant negative correlation with the slope.Soil nutrient and altitude showed positive correlation,and ammonium nitrogen was significantly correlated,and available potassium was extremely significantly correlated;Both ammonium nitrogen and available potassium were positively correlated with the slope direction,and the ammonium nitrogen were significantly positively correlated with the slope direction,while the available phosphorus and the slope direction were extremely significantly negatively correlated;Soil nutrients were negatively correlated with soil bulk density,except for available phosphorus,the other three nutrient indicators were extremely significantly negatively correlated with soil bulk density.d)For the single dominant species patches of Calamagrostis Pseudophragmites,The number of average water content was followed by lakeside>dry lake>flat land between dunes,and its average salt content was followed by dry lake>lakeside>flat land between dunes.On the patch scale,the data of Soil water and salt content and vegetation cover were in line with the normal distribution model.The spatial structure of soil water and salt content in each layer and vegetation cover of Calamagrostis Pseudophragmites in the three sample areas all existed high degrees of spatial heterogeneity.The spatial distributions of soil water and salt content and vegetation coverage in all three plots had positive correlations and agglomeration characteristics.The spatial agglomeration intensity of soil water and salt content for the 60~90 cm soil layer was larger than those of 0~30cm and 30~60cm soil layers,and the spatial clustering characteristics of the vegetation cover was more obvious in the Lakeside plot.And thus,the Calamagrostis Pseudophragmites maximized the use of soil water and salt resources,and so as to improve its adaptability and competitiveness to the drought habitats.And to a certain extent,it affected the spatial distribution pattern of soil Lakeside plot in small scale.