The Comprehensive Assessment And Policy Reseaching Of Urban Ecosystem Carrying Capacity In Changchun

City is not only the symbol of human being civilization, but also the focus and crystal of development change of economy, politics, society, science, culture, and environment. The contradiction between economic development and environment is becoming spiculater and spiculater with industrialization of city. The development of city need strong ecological sustentation, only maintain the natural work of society, economy and natural environment , can the harmonious development between environment and economy come true.Changchun is the center of economy, politics, science and culture in Jilin province, It pay much attention to city environment, and has achieved much effect. But the distance with developed city is obvious, such as the small amount of economy, unreasonable configuration, low water resources of built district per capita,asymmetric virescence of the city,serious sandy wind and so on. All of the above restrict the construction of ecological city in Changchun.This paper mainly studies the ecosystem of Changchun built district, proposing the urban ecosystem capacity quantitative indicators and building the urban ecosystem carrying capacity evaluation model from the viewpoint of urban ecosystem health, stability and sustainable development. On this basis, the paper analyzes the urban ecosystem structure and functional characteristics, the existence of bottlenecks and potential ecological effects with the major research tools of regional land use change, landscape evolution and environmental quality evaluation. The result shows: Water resources of built district per capita is low; the air quality tends to gradually improve in general; Urban development makes land area of built district doubled to narrow; Land types that are closely related to Urban Development such as Services sites, tourism sites, industrial sites, transportation sites and so on keep on growing continually.This paper builds an index system and evaluation methods to calculate carrying capacity, and it also analyzes and evaluates the urban ecosystem of built district carrying capacity changes during 1996-2005 Based on the urban ecosystem carrying capacity model and evaluation model along with the urban ecosystem structure and functional characteristics of built district. The results shows: the support capacity of Changchun urban ecosystem tends to grow steadily on the whole. Urban ecosystem structure and function tend to become improved and coordinated. In the component structure of support capacity, the level of natural support capacity is much greater than the acquired support capacity. It shows that Compared to well-running natural ecological subsystem with all kinds of functions, Socio-economic development of the subsystem level and operational efficiency is far lagging behind the goal of a harmonious system and a peaceful society that the ecological cities are trying to reach. Correspondingly, Changchun urban ecosystem pressure index changes have gone through two stages: the period of exponential decline in 1996-2000 (Index dropped from 0.48 to 0.12) and Steady decrease in 2001-2005 (Index dropped from 0.12 to 0.04). With socio-economic development accumulating to a certain stage, pollution control level and efficiency of resource use are improving gradually and the pressure that the socio-economic activities put on the urban ecosystem is reducing continually. In the meantime, Changchun urban ecosystem capacity index changes during 1996-2005(Index dropped from 3.0 to 0.18) shows that on the whole, Changchun is in a healthy state in which economy and the urban ecosystem support capacity develop simultaneously, and the development model it takes is sustainable. So it is possible to make the urban ecosystem of Changchun develop towards a healthy and orderly way if we take the following measures: taking Effective ecosystem management strategies, changing the status of restrictive factors that affect the urban ecosystem carrying capacity, slowing down the growth rate caused by the urban ecosystems pressure due to the development needs, Maintaining the trend that its support capacity for the growth is greater than its pressure.Nowadays, Changchun's urban ecosystem of sustainable development is facing many restrictive factors. In order to improve the carrying capacity of the city's ecosystem, we must begin with the construction of these five systems: the resource utilization system, ecological environmental system, economic development system, social security system and integrated control system. Based on these five systems, we can build a frugal use of resources system, an improved city service functions, a healthy and beautiful ecological environment, a competitive economic system, a people-oriented social system, a set of sustainable, normative and reasonable policies and regulations. If all these mentioned above could be put into practice, Changchun's urban ecosystem carrying capacity and the capacity for sustainable development will continue to improve.