The Distribution Pattern Of S. Alterniflora Under Different Land Use Change Scenarios And The Planning Of Key Intrusion Monitoring Areas

With coastal wetland in Jiangsu province as survey region,this paper selected Spartina alterniflora as research object and analyzed the influences of the land use change on the distribution of Spartina alterniflora.According to socio-economic development plan and the features of Spartina alterniflora expansion,we built four scenarios—the natural trend scenario(scenario 1),the rapid invasion of Spartina alterniflora scenario(scenario 2),the ecological protection scenario(scenario 3)and rapid development of urbanization scenario(scenario 4).We simulated the spatial distribution of Spartina alterniflora under different uses of land based on CA-Markov model,meanwhile,we used ZONATION model to identify the high risk area that Spartina alterniflora invaded under different scenarios.The result showed that:(1)From 2002 to 2014,natural wetland area of the survey region reduced;the artificial wetland area increased;the non-wetland area increased fluctuatedly;the area of Spartina alterniflora changed slightly while the spatial distribution changed sharply.The landward expansion was limited while the seaward expansion was significant.Through transfer matrix,we found that the main land using types which affected the landward expansion of Spartina alterniflora were fish culture zone,paddy field and construction land.The bare mudflat and suaeda salsa were much influenced by Spartina alterniflora so the area of them reduced successively.The landscape pattern analysis showed that the index of wetland landscape pattern in Jiangsu Province was consistent with that of the swamp landscape pattern of Spartina alterniflora.It indicated that in Jiangsu Province the wetland use change determined the landscape pattern of Spartina alterniflora and that the landscape pattern of Spartina alterniflora tends to be more fragmental and heterogeneous.(2)According to the results of different scenarios in 2026,the general trend from 2002 to 2014 was consistent with that from 2014 to 2026,that is to say,natural wetland area reduced while artificial wetlands and non-wetland area increased.In scenario 1,the spatial location of Spartina alterniflora ceaselessly moved to sea.The area it transferred in concentrated on bare mudflat while the area it transferred out on artificial land;in scenario 2,the local vegetation area of natural wetland reduced while Spartina alterniflora area increased significantly,which threatened local ecological en-vironment;in scenario 3,the natural wetland was protected with the area of Spartina alterniflora and that of transferring in and out reducing;which could protect local ecological environment and grain;in scenario 4,with the town moving to sea,the expansion of Spartina alterniflora to land was limited,which threatened the local food security.In terms of landscape pattern,the index of land using landscape pattern was consistent with that of the landscape pattern of Spartina alterniflora under different scenarios in 2026.It indicated that the land use change under different scenarios would lead to the change of the landscape pattern of Spartina alterniflora correspondingly.Under scenario 2,the Spartina alterniflora area was the largest;the landscape agglomeration the highest;the shape most complex.Under scenario 3,the landscape fragmentation and heterogenization was the severest.Compared with scenario 1,under scenario 4,the landscape was more fragmental because the expansion of Spartina alterniflora was limited by the urbanization.(3)By using ZONATION model,we inferred the prior prevention area for Spartina alterniflora in 2026 under four scenarios.The primary and secondary prior monitoring area should be the key areas.The distribution of the primary prior monitoring area is different in four scenarios.Under scenario 1,it concentrates on the coastal area ranging from Xinyang Harbor to Doulong Harbor and from Dafeng Harbor to Liangduo River.Under scenario 2,the district from Sheyang Harbor to Xinchuan Harbor should be the primary prior monitoring area.Under scenario 3,the prior area,which is very narrow,distributed mainly in the district from Xinyang Harbor to Doulong Harbor.Under scenario 4,the main monitoring area distributes in both seaward and landward direction from Sheyang Harbor to Xinchuan Harbor.The acreage of the secondary prior monitoring area under four scenarios is of similar size.Under scenario 1,the area mainly distributes in bare mudflat,reed marsh,salsa marsh and fish culture zone from Dafeng Harbor to Changsha Harbor where are surrounded by Spartina alterniflora.Under scenario 2,it distributes in natural wetland and the landward region near where Spartina alterniflora grows.Under scenario 3,it concentrates on the district from Xinyang Harbor to Doulong Harbor.Under scenario 4,the key monitoring area distributes in the natural wetland both seaward and landward from Dagang Harbor to Changsha Harbor where the primary prior monitoring area laid around.This paper analyzed the distribution patterns of Spartina alterniflora and the key monitoring area where it invaded.It can provide scientific basis for the formulation of an appropriate,long-term,effective strategy for the control of Spartina alterniflora.Its methodologies of analyzing can be a good reference for other invasive speices.