The Analysis On The Landscape Of Urban Green Space System And Evaluation Of Soil Quality In Tianxin Distract Of Changsha

Urban green space system is the main components of urban ecosystem, it plays an important part in the urban ecological system. The urban green system improves the air quality, reduce heating island effect, purifies and preserves water reservoirs, hence it is vital for development of suitable ecological environment. This dissertation studied on the urban Greenland system in Tianxin distract of Changsha. Based on the RS imagery of Tianxin distract by QuickBird, analyzing the indicators of landscape pattern by using the theories of landscape ecology, and selected some soil samples in Tianxin distract, their physical and chemical properties, Nutrient and heave metals were analyzed in the lab, in order to have a comprehensive evaluation on soil quality of the distract. The research could provide suggestions for urban Greenland construction and soil quality management. The results of the research are as follows:The number of various types Green patch was in the order as:sub greenlands>public greenlands>protective greenlands>productive plantation areas>the other greenlands; The size of different patches was in the order as: the other greenlands> productive plantation areas> sub greenlands> public greenlands> protective greenlands; The green patches mainly were small patches, their number was accounted for 76%, the small patches were mainly in the sub greenlands; There were little large patches in the distract, but its size was accounted for 76.42%; The size of types Greenlands was uniform, the index of uniformity was large, and the dominance was not obvious; Generally speaking it indicated a lower degree of fragmentation, but the sub greenlands had a high degree of fragmentation, the lands were small and scattered; The landscape diversity was low in the distract, and with less greenland type, high degree of urbanization.the soil of the greenlands in Tianxin distract was acidic to alkaline, and it was suitable for most of garden plants growing; The average content of organic on the surface of the soil was 24.50g/kg, The average content of N was 0.79g/kg, the average content of P was 0.33g/kg, the average content of K was 3.99g/kg. compared with the result of the second soil survey in Hunan province, the average content of organic in study area were higher than the average content of Hunan province,except the sub greenlands'. the Nitrogen content was at a medium level, and inadequate supply of phosphorus, Potassium concentrations are far below the average of Hunan soil, Potassium concentrations are far below the average of Hunan soil, The results show that the overall fertility of the greenland soil is not high in Tianxin distract, but the nutrient content of productive greenlands was more balanced, and its soil fertility was relatively good.Soil analysis showed that the soil of Tianxin distract was not fertile, only the productive plantation areas fertility was relatively good; concentrations of heavy metals in public greenlands, sub greenlands, road and traffic greenlands were generally higher than those in productive plantation areas, and spatial distributions of heavy metals indicated discernible variations in different greenlands soil. Correlation analyses showed that organic matter was the main carrier of heavy metals, the five heavy metals (Cd, Pb, Ni, Cu and Zn) came from the same source in sub greenlands, road and traffic greenlands; Cd, Pb, Ni, Cu and Zn in public greenlands and road and traffic greenlands mainly came from vehicular source, and those in sub greenlands from life pollution source. Comprehensive pollution index of soil heavy metals in four kinds of urban greenlands was in the order:public greenlands> sub greenlands> road and traffic greenlands> productive plantation areas, and all were in light pollution grade, with the highest index value of Cd, next to Pb, Cu, and the lowest values of Zn, Mn and Ni; Contamination of Cd and Cu was more serious in public greenlands, sub greenlands, contamination of Pb and Ni was more serious in public greenlands, road and traffic greenlands, contamination of Zn was more serious in sub greenlands, road and traffic greenlands; The order of potential ecological risk index of soil heavy metals in four kinds of urban green-lands ranked as follow:public greenlands>sub greenlands>road and traffic greenlands> productive plantation areas, all were in slight ecological risk degree, Cd had the highest potential to cause ecological damage, next to Pb, Cu, and the lowest of Zn, Mn.