Study On Dynamic Changes In Landscape Ecological Security Pattern During Different Periods In Cheng Du City

Urban Landscape Ecological Security Pattern (SP) plays a key role on maintaining and controlling landscape ecological process, and exerts a significant influence on sustainable development of the economy. Based on the maintenance of regional ecological health and the protection of bio-diversity, the study objective is the optimal utilization and conservation of forest lands in the chosen object, Chengdu metropolitan regions. The study uses TM satellite data of 1985,1995 and ETM satellite data of 2006 year as main information source. With the help of GIS technology, the SP has been constructed and the three levels of ecological security have been classified. It identified and analyzed the characteristics of the SP, studied its spatiotemporally changing trends, and the driving impact from urbanization on these changes. The results showed that:(1) In these twenty-one years, the distribution of overall security level of the of the SP in Chengdu was imbalanced.(2) During the three periods, the ecological security pattern was the best in 1985; from 1985 to 1995, the ecological security pattern deteriorated significantly since most of high level of ecological security regions become middle level of ecological security regions; from 1995-2006, the ecological security pattern was improved greatly.(3) The aggregate area of forest lands in Chengdu decreased continually. The whole forest landscape tended to be fragmented and the shape of it inclined to be simple.The analysis of changes in different ecological security level regions in Chengdu shows that: in each period, the area of forest lands in the high security level region was much larger than that in intermediate or low level security level region and its fragmentation degree was the lowest. The area of the low security level region was the smallest and the number of patches was the fewest. There is a positive correlation between the changes in the area of forest land and the number of patches and the changes in the state of ecological security while there is no evident correlation between the complexity of the shape of the forest patches and the security regions where these patches are.(4) The main driving impact on the change in SP is the urban expansion. There is a game between the SP and urban expansion security pattern in Chengdu. The impact from human interferences on security pattern was significant. From 1985 to 2006, the constantly expansion of the area of the urban-use land, the constantly increase in the ratio of non-rural population and the pattern of the urbanization significantly influenced the urban sprawl security pattern, they also had the direct or indirect impact on the changes in the whole SP.Based on these results, the study offers relevant strategies of ecology management and construction according to the different landscape space from ecological security level.