Multi-scale Spatial Variability Of Urban Soil Texture And Its Effects On Water Properties

Atmosphere,water,soil are important parts of the environment,as a link of environment,soil has an important ecological function.With the rapid development of the city,the strength of city's construction is increasing,while the soil's ecological function remains ingored.Especially the impervious surface which used in the city,has caused a series of problems,such as the urban flood disaster and heat island effect,has a serious influence on the city's development and human health.Soil texture,as a basic physical properties of soil,has an important influence on the ecological environment of the city.This article analyzed soil texture's influence on the impact of water from the perspective of space mutation.Because of the complexity of the urban soil,this article adopts the method of multi-scale comprehensive analyses soil texture's space changing rule.For further revealing the soil texture's city spatial heterogeneity,this article adopts the method of GIS and geostatistics analyses Shanghai city strip,including Xuhui district,Minhang district and Fengxian district.The three districts have the gradient difference of suburban country,have the ecological environment vulnerability.Then using soil conversion function for further prediction,such as soil water characteristic curve,soil field capacity,soil saturated hydraulic conductivity,reaching following major conclusions.1.On the basis of soil texture statistical feature,the average value of soil clay is 13.05%,the average soil sand is 6.96%,both belong to moderate spatial variation,sand soil's variation of intensity is larger than soil clay.And they are adjust to Gaussian Model,have strong spatial autocorrelation,in which soil sand still higher than soil clay.On the scale of district,the spatial variation of soil clay also less than the sand in Xuhui district,as well as in Minhang district and Fengxian district,the spatial variability of sand soil is most outstanding in Minhang,then Fengxian.Consider from spatial structure,they are based on exponential model;consider from nugget coefficient,clay in Minhang and sand in Xuhui are strong influenced by random factors,the spatial autocorrelation of clay is stronger than sand in Xuhui district.In the perspective of functional zone,the variation coefficient of soil clay is most outstangding in industrial zone,then in traffic greenbelt,residential area,Pujiang farmland and park.Sand soil has most variability in industrial zone,the variation coefficient is 0.89,bolongs to moderate spatial variability.The space structure of functional area is still based on exponential model,the nugget coefficient of clay in industrial zone is largest,which explains that the industrial zone's clay is under strong interference.2.The mean value of soil organic matter is 20.53g/kg,which is of moderate intensity spatial variation;The soil organic matter in xuhui district,which has a strong spatial self correlation,and is a spherical model,other minhang district is gauss model,and fengxian district is gauss model.The contents of organic matter in xuhui district,minhang district and fengxian district are respectively 23.96 g/kg,21.96 g/kg,18.18 g/kg,item are all of moderate spatial variability.As can be seen from the half-variation function,soil organic matter is still determined by structural factors;The soil organic matter is an exponential model.3.The multi-scale spatial distribution of soil texture shows that the distribution of soil sand is higher in the southeast and lower in the northwest,which shows a banded distribution.Due to the strong complementary of sand soil and clay soil in space,the clay is opposite of the sand,appears the phenomenon that the lower urbanization level is,the higher soil sand content is.In Minhang district,the content of sand appears an island shaped distribution,which illustrates that it is affected by the strong human factors.And we get the results by ordinary kriging interpolation,thus its accuracy is high.The soil sand content in Xuhui district increases from west to east,which shows a banded distribution,the highest value appears in northeast.And soil sand in Xuhui is used cross validation method to get results,has the highest prediction accuracy.Silt soil in Xuhui district shows a zonal distribution,the high-value area distributs in the centre of Xuhui as well as the soil clay has a downward trend from west to east.Soil sand in Minhang district is dot distribution,its spatial distribution regularity is not obvious,the low-value area mostly distributes in the middle of Minhang;soil clay appears an island shaped distribution,its spatial distribution is complex.In Fengxian district,sand soil content is reduced from the north to the direction of the Hangzhou bay,the high-value area distribution is in low-lying area of the Hangzhou bay,apprars obvious zonal distribution;distribution of clay is in the opposite,the high-value area mainly located in where the sand is less.When it comes to different functional areas,in industrial zone,soil sand is distributed as island,the high-value areas are mainly distributed in northern;soil clay is also distributed as island.In agricultural district,soil sand shows an article zonal distribution,regularity is not obvious,and the high-value area is mainly located in the southwest,clay soil content appears a trend that lower in the west and higher in the east.In residential district,soil sand also shows an article zonal distribution,the high-value area is located in road exit of the village,clay soil content is lower on both sides but higher in the middle.In traffic greenbelt,sand soil is lower and lower from north to south.In the park,soil sand also appears to an article zonal distribution,and soil clay content appears an island shaped distribution.4.High content of soil organic matter is high value area distribution in xuhui district,low in distribution in fengxian area,from the city center to the outskirts of soil organic matter content has a decreasing trend of law,in urban soil,which spatial distribution of soil organic matter content is closely related to the intensity of class activities,and the spatial distribution is complex,and have to accumulate.5.Estimation and analysis of the nature of water through the soil basic properties can be obtained,which parameters of soil water(soil field capacity,soil saturated water content,wilting coefficient,etc.)and clay soil has stronger positive correlation,and soil saturated hydraulic conductivity is closely related to soil of sand.The soil water transfer function is used to estimate that the parameters of soil moisture characteristics.In this paper,the soil saturation water conductivity rate is the transportation greenfield > industrial zone of > residential area of > park in the > agricultural area.It has shows that the water conductivity of the different functional areas is different.The saturated moisture content of the soil transportation greenfield > residential area of > agricultural area of > industrial area of > in the park,indicating that the water supply performance of difference functional areas is different.Field water area residential area >agricultural area > industrial zone > transportation green space.Overall performance is low,the sample with a water for soil water characteristic curve,it has negative correlation with soil water content,soil water suction usually at high suction stage is mainly decided by the soil texture,and in lower suction stage is mainly composed of soil properties,such as structure,density of soil organic matter.Therefore,improving soil organic matter content and improving soil structure can effectively improve soil water supply and water supply,and can improve soil effectively.