Evaluation Of Coastal Wetland Ecosystem Stability And Future Landscape Simulation In Yancheng,jiangsu

As an important part of wetlands,coastal wetlands have huge ecological,economic,social,and cultural values in maintaining the stability of regional biological systems and providing material resources.With the increasing disturbance of human activities on coastal wetlands,changes in coastal wetland ecosystems are also increasingly concerned by scholars at home and abroad.Based on in-depth and detailed on-the-spot investigation and research,this study carried out sampling survey on soil,water quality and vegetation in Yancheng coastal wetland with the help of remote sensing and geographic information system technology to analyze the characteristics of wetland soil,water quality,vegetation and landscape pattern.The stability evaluation index system of the coastal wetland ecosystem in Yancheng has been constructed comprehensively,systematically and scientifically,and it has been graded and overall evaluated.The spatial distribution pattern of the stability level of the coastal wetland ecosystem in Yancheng has been preliminarily determined.The CA-Markov model was used to simulate the future landscape change of the coastal wetland in Yancheng,and its ecological risk assessment was performed.The main conclusions areas followed:(1)There were obvious regional differences in wetland soil organic matter content.The soil was moderately fertile and mainly alkaline soil.Among the available nutrients in wetland soil,the content of available potassium was much larger than that of ammonium nitrogen and available phosphorus,and the regional differences were large.The wetland water environment was relatively poor,and the average water quality was greater than Class V of the surface water environmental quality standard.Among them,the chemical oxygen demand of wetland water quality exceeded the standard seriously.There were many types of wetland vegetation,and various vegetations were unevenly distributed under different environmental characteristics.The level of landscape vulnerability had deepened,and the area of high vulnerability areas had grown rapidly.(2)The ecosystem stability of Yancheng coastal wetland was in the stage of early warning classification,and the ecosystem stability was under certain external threats and disturbances.In each region,the stability of the coastal wetland ecosystem in the coastal segment was in a relatively stable state,while the stability of the coastal wetland ecosystem in the Xiangshui segment,Sheyang segment,Dafeng segment and Dongtai segment was in an early-warning state,and the stability of the wetland ecosystem in the Dafeng segment was the weakest.The indexes that had a great influence on the ecosystem stability of Yancheng coastal wetland include the degradation rate of tidal and beach wetland(D₁),regional development index(D₃),urbanization rate(D₆),organic matter(D₁₄),biodiversity index(D₂₃),landscape fragmentation degree(D₂₄),construction investment of nature reserve(D₃₁).(3)The optimal analysis granularity of the Yancheng coastal wetland landscape pattern was 30m,which was used as the cell size.Using the CA-Markov model,the landscape data under the three scenarios of the study area in 2021 and 2025 were simulated.According to the simulation process,the simulation results could be divided into current situation use scenarios,natural development scenarios,and ecological protection scenario.In the scenario simulation,under the current situation use and natural development scenarios,artificial wetlands tended to increase and natural wetlands decrease.Under the ecological protection scenario,the areas of reed,Suaeda,and Spartina alterniflora on the ecological land expanded rapidly,and the area of constructed wetlands decreased.From 1991 to 2025,the Yancheng coastal wetland conversion was complicated and the conversion area involved a wide range.A total of 1,770.36 km² of conversion occurred,and the area with severe conversion was concentrated in the south of central Sheyang County.(4)The ecological risk of coastal wetland in Yancheng was intensified and the spatial differentiation was obvious.From 1991 to 2017,the area of extremely low,low,and relatively low level risk areas decreased rapidly,while the areas at medium,relatively high,high,and extremely high levels increased significantly.The ecological risk was prominently manifested as low in the north and high in the south,with the middle of Sheyang County as the boundary.Land and coastal ecological risks showed different risk differences in different periods.From2017 to 2025,under the current situation scenario,the medium risk zone will maintain its dominant position.Under the natural growth scenario,the dominant level will change from the middle level in 2021 to the higher level in 2025.Under the ecological protection scenario,the dominant grade type will change from a higher grade in 2021 to a medium grade in 2025.The high levels of ecological risk ware concentrated in the south of Sheyang County,Dafeng District,and the middle of Dongtai City.