Theoretical Study On Urban Ecosystem Indexes And Optimization Of Ecological Networks

Urban ecological system containsmany aspects and research contents. Urban greening indicators can be used to measure the pros and cons of the urban green space systems, and the landscape pattern index pattern can also describe the quality and difference from the green space system. They and other urban environmental factors constitute the natural subsystem of urban ecological networks. This paper analyzes thelevel of urban landscapingand the existing problemsin our countryby the greening indicators.Furthermore,it analyzes the change process of landscape pattern index dynamic through aggregation index and optimizes the structures of urban ecological networks.Firstly, average landscaping efficiency of each province,the population of green space service,urban environmental protection and construction and landscape pattern index of green space are generally investigated and analyzed in the paper. The results showed that:(1) Landscaping efficiencies of cities in coastal provinces are above the average, while cities in the southwestern provinces are below average.(2) Overload population of green space service is more serious, the average load ratio as high as 46.9%, especially in Shijiazhuang and Shanghai etc.(3)The north and south city reflects two different types of green space landscape pattern in evenness index and Shannon diversity index.Then, describing and simulating the dynamic process of the landscape pattern index of aggregation in order to describe the dynamic ecological processes. The results showed that:(1) Aggregation index Cr is related to the length of common boundary between two adjacent ecosystems and its control points. The variation of coordinates of control points embodies the change of landscape structure.(2)The change of coordinates of common control points for two adjacent patches reflects, in essence, the horizontal expansion. We obtained the change of horizontal diffusion of aggregation indexovertime after determining the change rate of density, the total amount of main expanding vegetation and the diffusion coefficient. In the vertical direction, describing the variation of coordinates of control points by using the method of SARIMA.(3)To illustrate the dynamic process of landscape indicators, a virtual landscape structure is simulated as an example,and we got the variation of aggregation index and common boundary length with the processes of expansion of the plaque.Finally, taking the urban ecological system into a network,the structure of the urban ecological networks are optimized through the measure of recycling. The results showed that:(1)The recycling values are both relatively small in the networks of second-tier cities and third-tier cities. Through the important nodes, there are six kinds of optimization scheme for each network. Eventually the model(2)3M is selected to be the optimal solution for second-tier cities, and the model(3)1M is selected to be the optimal solution for third-tier cities.(2)The recycling value of the network of all the cities is significantly larger. After deleting 17 redundant mapping relationships through the standardized regression coefficient, the optimized model and solution is determined.