| Urban ecosystem, providing the function such as recreation, environmental services and biological production,promotes the healthy and orderly development of the city and constitutes the important foundation of the natural subsystem. However,the rapid expansions of urban areas lead to the disappearance of ecological lands in inner cities and suburbs where are originally forest lands and cultivated lands.The urban ecosystem functions are weakening.As the living standards of urban population have increased rapidly,the quality of life has not been much well improved yet.The proper use of urban land is to constantly adjust to the city’s main functions,guarantee the healthy sustainable development of the city,and improve the urban competitiveness.Based on the HD images of 2003,as well as current land use database of 2013,this study analyzes the evolution on amount,structure and the space of ecological land in the districts of Chengdu city,and various types of ecological land conversion mechanisms.Then the change of landscape patterns and ecological lands of Chengdu city are analyzed with the use of the plugin of GIS software,Patch Analyst for landscape pattern index;land use types are clustered by fuzzy clustering analysis; Lastly,each parameter of gas regulation,environment purification,water and soil conservation are established as comprehensive evaluation system of ecological land service ability to evaluate the ecological land service ability of each district;grey correlation analytical(GRA) is adopted to measure the correlations between each parameter and the ecological land service ability.The conclusions are as follows:Firstly,there had been a decreasing trend in the areas of ecological land in Chengdu city from 2003 to 2013,reducing 3,040.1499 hectares,of which the area of cultivated land decrease accounted for 93%,the highest percentage of total decreased area.The ecological land areas of Chengdu took up 25.55% of the total studied area in 2003,but fell by 6.53% to 19.02% during the study period.From the point of ecological land conversion,ecological land changed into non-ecological land area by 3,310.1069 hectares;the mutual conversion between different types of ecological land areas were 405.1076 hectares;the areas of non-ecological land turned into ecological land were 135.151 hectares.Secondly,from the study of the landscape pattern,the number of patches were the largest,so are the average patch areas of the parks;while the patches of the orchards were small and scattered.The discrepancies of ecological land patch areas within the research phase were expanding,the landscape diversities were low,and the shapes of ecological lands were relatively simple.The overall fragmentation deepened,and the most obvious fragmentation was on orchard.By fuzzy clustering analysis of ecological lands,ecological lands of Chengdu city in 2003 were divided into three categories, while divided into four categories in 2013.Thirdly,the ecological land service capacities in each district differed greatly.In 2003,the ecological land service capacity of Chenghua district was the highest,while the lowest was the High-tech Zone.In 2013,Jinniu District enjoyed the highest ecological land service ability and Wuhou district was the lowest.Though demographic factors are considered,the discrepancies of ecological land service capacity were still large.The highest average ecological land service capacities in 2003 and 2013 was Chenghua district,while the lowest was Wuhou district.By GRA, the correlation of land and park versus the average ecological land service ability was higher,while the correlation of river versus the average ecological land service ability was the lowest. |
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