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Urban green space system is a major part of the ecosystem of the city, is the city's main natural factors. Urban green space not only can absorb carbon dioxide and release oxygen, it has also beautify the environment, reduce noise, dust, water purification, increasing humidity, improve the urban heat island effect a variety of functions, is one of the key factors in maintaining the health of the environment of the city, the city of The healthy development of great significance. In this thesis, Tianxin urban green space system as the research object, the use of the principles of landscape ecology for quantitative analysis of the landscape pattern of the area of ??urban green space system, the same time the green soil samples collected within the study area, indoor test analysis of soil physical and chemical properties nutrient elements and heavy metals content, evaluation of the condition of the soil fertility in the study area, the heavy metal pollution levels and its potential ecological risk. The results can provide decision support for the of Changsha urban green space landscape planning, construction and green space soil quality management and improvement. The main findings are as follows: Tianxin various number of green patch Sort order: the attached green space (4180) gt; public green (424) gt; protective greenbelt (160) gt; the production green space (155) gt; other green spaces (67); the various plaque area the size of the order is: gt of other green (547.31hm2); production green (265.21 hm2) gt; attached green (163.44 hm2) gt; public green (89.28 hm2 in) gt; protection green (80.51 hm2); the green patch small plaque based, 76% of the total plaque and mainly attached green; small number of large patches, but the area accounts for 76.42% of the total area of ??the Tianxin green space; each green space type occupies an area more uniform, the overall evenness index, dominance is not obvious; Green Landscape in overall green landscape fragmentation is not obvious, but the higher the degree of fragmentation of the attached green, human disturbance, the green area is small and scattered; low diversity index, less green space type, building area, a high degree of urbanization. Tianxin greenbelt pH value of the soil acidic to weak alkaline, suitable for the growth of most garden plants; Greenland soil surface organic matter average content of 24.50g/kg, and the average total N content 0.79g/kg total P the average content for 0.33g/kg, total K content 3.99g/kg. Second soil survey results in Hunan Province, the relative ratio of the Tianxin green space soil except attached green, organic matter content of the remaining green space types are higher than the average of Hunan Province; N pigment content in the middle levels, inadequate supply of phosphorus, potassium the content is far lower than the average of Hunan soil, potassium deficiency is very serious. Show that the overall Tianxin greenbelt soil fertility quality is not high, but the the production green nutrient content is relatively balanced, relatively high fertility status. Public green space, the attached green space green areas and road traffic soil heavy metal content higher than the production of green space, Different Greenbelt Types spatial distribution of soil heavy metals are quite different; attached green parkland and road traffic, organic matter is the main carrier of soil heavy metals, Cd, Pb Ni, Cu, Zn, the possibility of the same sources; parkland and road traffic greenbelt pair-wise correlations between Cd, Pb, Ni, Cu, Zn, mainly derived from the traffic generated from the source of pollution, attached green the heavy metals may be derived from living sources of pollution; sort in descending order by the four kinds of soil heavy metals pollution index: public green gt; subsidiary of Greenbelt gt; road traffic greenbelt gt; production green in mild pollution levels, Cd pollution is the most serious , Pb, Cu pollution Secondly, Mn, Zn, Ni contamination is small; public green space, attached green Cd and Cu Pollution heavier road traffic green spaces, public green Pb and Ni serious pollution Zn pollution heavier is attached green and road traffic greenbelt; four kinds of soil heavy metals potential ecological risk index size Sort: public green gt; attached green gt; road traffic greenbelt gt; production green, both in the ecological risk of minor ecological hazards, Cd, Pb is followed, Cu, Zn, Mn min.
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