| Eastern Chongming Island is one of the largest wetlands in Shanghai.It plays an important role in resisting natural disasters such as storm surge,regulating climate,purifying water quality and so on.However,in recent years,land use / cover status and landscape pattern of Eastern Chongming Island have undergone a series of changes due to the impact of human activities such as reclamation and Spartina alterniflora.Therefore,it is of great significance to carry out land use / cover monitoring research in Eastern Chongming Island.Eastern Chongming Island Tidal wetland is located in the sea-land interchanges,the tidal flat is affected by damp and tide,and it is always changing and the accessibility is poor.In recent years,with the development of 3S technology,remote sensing technology is widely used in large scale,large scale wetland land use / cover survey because of its macroscopic,synchronous and dynamic advantages.The landscape pattern is the result of the interaction between different ecosystems in nature,biology and society in time and space.With the help of the principles and methods of ecology,the evolution of Eastern Chongming Island landscape pattern is analyzed,which is helpful to discuss the dynamic change of landscape spatial and land use / cover policies for sustainable development,based on the interrelationships between land use / cover and landscape.In this paper,TM images of 1985,TM images of 1989,TM images of 1995,ETM images of 2002,TM images of 2004 and Landsat8 images of 2013 are interpreted by means of relevant basic data.The land use / cover information is extracted from the artificial landscape and the natural landscape by using the supervised classification and the hierarchical classification,and the results of the artificial landscape and natural landscape classification are combined to extract the land use / cover information of the study area.Classification accuracy and field verification.Based on the classification results of six remote sensing images,the land use / cover types of Eastern Chongming Island were analyzed with time,and the changes of land use / cover types were studied through land transfer matrix.Finally,the change of landscape pattern in the study area was analyzed from the two aspects of landscape level and patch level.The main results of this study are as follows:(1)In the study area,artificial landscape classification accuracy is 71.58% and 82.50% in the natural landscape,and the accuracy of the whole study area is over 80%.(2)According to the classification results of the six images in the study area and the relevant statistical results,it was found that the land use / cover changed most in the past 30 years was agricultural land,followed by Spartina alterniflora.The proportion of agricultural land before and after 2002 gradually increased to 10010.3ha in 2013.Since the introduction of Spartina alterniflora,with the time to spread to 2013 covers an area of 2614.23 ha become the dominant species in the tidal beach vegetation.(3)During the past 30 years,the natural and artificial landscapes of the study area have changed a lot.In 2002,a lot of natural landscapes were transformed into artificial landscapes.One of the most obvious changes in the natural landscape and artificial landscape are Spartina alterniflora and agricultural land.The patch density and the maximum patch index of Spartina alterniflora were the largest in the year of 2013,which were 0.0995 and 0.9734,respectively,indicating that Spartina alterniflora became the dominant natural landscape.The spreading of Spartina alterniflora resulted in a decrease in patch size and fragmentation of the reed and Scirpus mariqueter.(4)In the study area,the fragrant diversity index and fragrant evenness index decreased from 1.5309 and 0.6967 to 1.0862 and 0.6062,respectively,which indicated that the landscape diversity decreased from 1985 to 2013,Landscape fragmentation increased.(5)The driving forces of landscape pattern change include human reclamation and the spread of Spartina alterniflora.The natural evolution,tidal current,wind,waves and natural erosion of Eastern Chongming Island also affected the landscape pattern.. |
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