Research On The Change Of Land Use And Landscape Pattern Of Chongming Dongtan Wetland

Land use change is an important factor restricting regional social and economic development,and it is also an important driving factor of regional ecological environment changes.Wetland is the most biologically diverse landscape type in nature.With the development of social economy and the increase of human activities,the land use and landscape pattern of wetland have undergone major changes,and the function of wetland ecosystem has been significantly affected.Therefore,the protection and utilization of wetland resources need to be solved urgently.This paper takes Chongming Dongtan as the research area and takes two years as a period.A total of 18 remote sensing image data from 1986 to 2020 are selected.The images are supervised and classified by ENVI software to obtain the temporal and spatial changes of the Chongming Dongtan wetland land use in the past 40 years.On the basis of land use data,Fragstats software is used to analyze the landscape pattern characteristics of Chongming Dongtan,such as landscape fragmentation and dominance,combined with socio-economic data and local natural environmental conditions,to explore the influencing factors of landscape pattern characteristics changes.On the basis of changes in land use and landscape pattern,the countermeasures and suggestions for the protection and utilization of Chongming Dongtan wetland resources in the future are put forward.The main conclusions are as follows:(1)The results of the extent of land use change show that the land use change in Chongming Dongtan from 1986 to 2020 is significant.Among them,sea water and plain beach are the main land use types in Dongtan area,accounting for more than 50% of the total area studied.The area and distribution range of vegetation in tidal flat changed greatly,among which,the area of reed beach first decreased and then increased,and the area of grassland beach first decreased,then increased and then decreased.The spatial changes of the two vegetation areas showed a transitional evolution to the east.In arable land,the change of dryland area is stable,while that of paddy field is increasing.The area of woodland and construction land increased year by year.From the point of view of the transfer,the land use types in the four stages changed more frequently.Among them,the main transfer is between the natural landscape and the artificial landscape,and the changing area and turning area of the water area are the largest,followed by the natural landscape such as reeds beach,grass beach and plain beach.The untransferred area of cultivated land,woodland and construction land showed a rising trend and accounted for a large proportion.The transferred area is dominated by artificial landscape,mainly paddy field,woodland and construction land,and human activities significantly affect the evolution of land use.(2)The results of the change of land use dynamic attitude and degree showed that the relative dynamic attitude was generally greater than the absolute dynamic attitude,and the absolute dynamic attitude had little change in the beach,water area and dry land of reed,while the other types had great change.In terms of the relative dynamic attitude,the change of land use types was strong except that the change of total sea water area in water area was small.It shows that the conversion between various land use types is huge.The dynamic attitudes of comprehensive land use in the four stages were 2.44%,2.04%,1.68%and 1.59%,respectively,which indicated that the rate of land use change decreased gradually and the land use evolution slowed down gradually.From the perspective of land use degree,the land use degree of Chongming Dongtan shows an upward trend,with an increase of 30.69 in the past 35 years,indicating that the increase of human activities aggravates the evolution of land use.(3)The results show that the characteristics of landscape pattern change in 1986-2020 degree of landscape fragmentation of Chongming Dongtan present growth trend,evident in the fragmentation degree,the landscape type in reed beaches and grass land fragmentation degree is most serious,followed by construction land,forest land and paddy field,dry land,Guang Tan and the waters of the broken degree is relatively low.The overall change trend of landscape dominance index was firstly decreased and then increased,among which the water area and plain land occupied the dominant position,the landscape dominance position of beach vegetation,reed beach and grassland land was replaced by paddy field and dry land,the dominance degree of woodland and construction land was smaller,but the landscape dominance degree increased continuously.The index of landscape diversity and evenness increased from 1986 to 2008,and after 2008,the change was more intense and the fluctuation decreased.The increase of landscape shape index(LSI)and the decrease of CONTAG indicated that the patch shape of Dongtan gradually became complex,and the scatter degree of patches intensified.Different landscape types intersected with each other,and the degree of human disturbance increased.(4)The change characteristics of landscape pattern of Chongming Dongtan wetland are caused by the combination of natural factors and human factors.The geographical environment is the basic factor that shapes the characteristics of the landscape pattern.Vegetation resources have a direct impact,bird resources have a side impact,policy planning is the guiding role,and economic structure and agricultural development are the driving role.According to the results of land use change and landscape pattern characteristics,combined with local actual situation,from the ecological space planning,coordinate the relationship between agricultural development and wetland protection,optimization of wetland and the surrounding land use layout three aspects for the future of Chongming Dongtan wetland resources protection and utilization of proposed countermeasures.