Dynamic Evaluation Of Landscape Pattern And Ecological Vulnerability In Yuanjiang City

As an important base of agricultural and sideline products in China, Yuanjiang City, including the largest wetland protection area in Asia which is South Dongting Lake wetland protection zone, is a typical water town. The original landscape pattern of Yuanjiang City was broken, the ecological service function decline due to high strength development model and human activities. The research and protection of ecological environment is imminent.Under the support of RS and GIS technology, We analyze the Landscape Pattern in Yuanjiang City and temporal and spatial variation of ecological fragility, summarize the driving force for the changes of ecological environment, and put forward the corresponding protection suggestion by applying the transfer matrix evolution method, spatial principal component analysis method, principal component analysis method, weighted overlap addition method and Kriging interpolation method to four Landsat TM images of Yuanjiang City in 1996,2002,2008,2014 used as the data source. The main research results are as follows:The various types of landscape pattern changes significantly from 1996 to 2014 as below:the number of patches of water, forest, pond, construction increased. Meanwhile, the area increased; number of patches of mudflats and cultivated land went down and the area reduced; number of patches of reed beach increased, area increased firstly and then decreased. By analyzing the landscape pattern index of every type of landscape, we arrive at a conclusion as below:the landscape dominance of waters, bulrush bottomlands, pond and construction increased, the plaque aggregation increased, and the degree of fragmentation reduced; the landscape dominance of mud beach decreased, the plaque aggregation decreased, the degree of fragmentation increased; the landscape dominance of forest decreased, the plaque aggregation increased, and the degree of fragmentation reduced.Overall, from 1996 to 2014, the fractal dimension of area and perimeter area of the largest patch in Yuanjiang City decreased; the landscape separation, the degree of fragmentation, Shannon uniformity and Shannon diversity increased. It tells that the overall the landscape dominance of Yuanjiang City reduced, and the landscape patches tended to be simple and easily interfered by human activity, and the degree of fragmentation increased, the overall evenness increased, the landscape utilization rate is increased, and the biological diversity was rich.The landscape types, like among the mudflats, reed land and woodland, transformed frequently. From 1996 to 2002, the area of mudflats and cultivated land reduced sharply. They mainly transferred to reed beach, construction and waters; from 2002 to 2008, the area of mudflats and cultivated land continually decreased. They mainly transferred to reed beach, woodland and pond; from 2008 to 2014, the area of reed beach decreased sharply. They mainly transferred to woodland. This shows that the original landscape pattern of Yuanjiang City was destroyed with intensification of the social development and human activities.The total area of the ecological sensitivity in Yuanjiang City in descending order was as follows:moderate sensitivity> mild sensitivity> severe sensitivity> micro sensitivity> extreme sensitivity. Among them, ecological sensitivity according to the time sequence was as follows:2014> 1996> 2002> 2008; according to the sort of landscape types:woodland> reed Beach> mudflats> arable land> construction land> waters> pond.The total area of the ecological vulnerability in Yuanjiang City in descending order was as follows:micro vulnerability> extreme vulnerability> severe vulnerability> mild vulnerability> moderate vulnerability. Among them, The ecological vulnerability according to the time sequence was as follows:2014> 1996> 2002> 2008; according to the sorting of different landscape types:mudflats> construction> pond> waters> woodland> reed Beach> arable land. The area with high ecological vulnerability is mainly in the southwest and northeast of Yuanjiang City; the area with low ecological vulnerability is mainly in the central part of Yuanjiang City.As a result of Landscape Pattern and dynamic change of ecological vulnerability in Yuanjiang City, we can conclude that the driving force for ecological environment changes in Yuanjiang City mainly includes:influence of climate and sedimentation, influence of reclaim land from lakes and artificial afforestation. Through the analysis of the driving forces, we bring forward four suggestions on protection and management:establishing urban ecological system monitoring system, reinforcing the conservation of water and soil, rationally developing and utilizing resources, developing forest tending measures.