Comprehensive Evaluation Of Soil Characteristics Of Street Trees In Different Land Use Types

With the rapid development of urbanization,Shanghai,as one of the largest cities in China,has a large area of traffic green space.Street tree soil is very important in this green space system,but it is usually affected by more human activities and is prone to occurrence.Soil compaction,barrenness,heavy metal pollution and other issues.Street trees play an important role in urban ecological system and social environment.Poor site conditions are likely to have adverse effects on the physical and chemical properties of street tree soil,comprehensive fertility,and metal environmental quality.In order to scientifically manage the healthy growth of urban street trees,promote the precise fertilization of street trees,prevent potential ecological risks caused by heavy metals,improve the soil quality of street trees in different areas of the city,and ensure the sustainable development of urban green space ecosystems,this study combines the status quo of urban development in Shanghai with reference to The second-level classification of national land use types further divides land use types into five major categories,including urban residential land area(L1),commercial land use area(L2),industrial and mining construction land(L3),and rural residential land(L4),Agricultural and forestry land(L5).On this basis,the soil of street tree soil of 136 roads in 16 administrative districts of the city was studied as an object to study the fertility and metal environment characteristics of street tree soil,and the physical and chemical properties of soil and the content of main nutrients were measured in terms of comprehensive soil fertility characteristics,and the soil was measured in terms of metal environmental quality.The content of Cr,Ni,Cu,Zn,Cd,As,and Pb in the soil,using ANOVA,PCA,and GIS spatial analysis methods to analyze the soil nutrient content level,comprehensive fertility level,heavy metal pollution status,potential ecological risks,and heavy metal levels under different land use types.Primary sources for research and discussion.Below are key research findings:(1)According to the international system classification,the soil texture of street trees in Shanghai is mostly silt loam,with an average bulk density of 1.38g/cm3 and an average p H value of 8.43.The average contents of soil organic matter,alkaline nitrogen,available phosphorus,and available potassium are 15.92g/kg,56.10mg/kg,13.01mg/kg,and187.90mg/kg,respectively.The contents of main nutrient indicators are relatively low and the spatial distribution varies greatly.The average contents of soil available calcium,available magnesium and available sulfur are respectively: 3851.5mg/kg,129.40mg/kg,20.90mg/kg.The average value of the comprehensive soil fertility index(IFI)was 0.53,which was significantly positively correlated with organic matter,total nitrogen,alkaline nitrogen,available phosphorus and available sulfur(P<0.001),and significantly positively correlated with available potassium(p <0.05),showing a very significant negative correlation with p H(P<0.001).(2)There were no significant differences in the organic matter content,available nutrient(AN,AP,AK)content,bulk density and porosity of the street tree soil of different land use types.The content of available magnesium and available sulfur in the street tree soil of agricultural and forestry land(L5)was significantly higher than that of the other four land use types.The soil p H value and available calcium content of street trees in urban commercial land(L2)were significantly higher than those of the other four land use types.The comprehensive soil fertility of street trees in Shanghai is mostly at the middle level,and the soil fertility in different regions is significantly different and the correlation is not obvious.The horizontal distribution is the most,and the proportion of industrial and mining construction land(L3)is the highest at the lower level,which is higher than that of other land use types.The agricultural and forestry land(L5)is all in the middle and high levels.(3)Under different reference standards,the street tree soil in Shanghai has relatively serious Cd or Cr pollution,and relatively light As,Pb or Cu pollution.Under the five different land use types,the content of heavy metals in the soil of street trees in industrial and mining construction land(L3)was relatively high,and that in the soil of agricultural and forestry land(L5)was relatively low.However,the Cu content of commercial land(L2)was significantly higher than that of other land types.(4)The potential ecological risk caused by Cd in the soil of downway trees in different land use types was significantly higher than that of the other six heavy metal elements,and was in the middle and serious risk range(80≤Er<160).The potential ecological risks of individual elements in industrial and mining construction land(L3)are relatively high.The comprehensive potential ecological risks in the central urban area of Shanghai,the southeast region and the northern part of Chongming Island are relatively low,while the western and northeastern coastal regions have moderate or more serious comprehensive potential ecological risks(150≤Ri<300),which is different from that in this region.There is a certain correlation with the type of land use.The source of Cu and Zn heavy metals in the soil of different land use types is similar to that of Cu and Zn,and the source of Cr,Ni and Cd is similar.There was no significant correlation between As and Pb.The source of Pb in industrial and mining construction land(L3)was relatively independent,while the source of As in agricultural and forestry land(L5)was relatively independent.