| The muddy coastal wetland in Yancheng is one of the most typically primitive coastal wetland for the significant strategic position in global biodiversity protection.. Over the years, under the influence of the nature and human socio-economic development, the wetland landscape structure and function changed dramatically. Especially, the contradictions between wetland protection and development gradually increase for the implement of the strategy about the Coastal Development Drive. In this context, how to identify the spatial patterns of the landscape evolution under the influences of natural and human factors and revealing the mechanisms for the wetland landscape structure and the pattern of spatial-temporal evolution under the intrinsic ecological process drive. They are important scientific problems to achieve the aim that using and protecting the coastal wetlands reasonable.The theories about the landscape ecology, geography, and environmental sciences and the methods of RS, GIS, and mathematical modeling are used in this study. Taking the coastal wetland in Yancheng as the typical area, and the region was separated into the labor control and natural condition parts to investigate the soil properties and changes, and to reveal the threshold effects of different ecological evolution from the perspective of the landscape ecological process. Based on these researches, a landscape model based on the ecological process was constructed by using the spatial data of the landscape structure in wetland and the ecological process data of landscape. The spatial-temporal evolution process and mechanisms were studied under the two modes. And the scenario analysis and prediction for the evolution of regional landscape were implemented. The study not only embodies the innovation of the research methods about the landscape process model, but which is of great significance for guiding regional wetland ecological protection and rational utilization. The main conclusions are as follows:(1)The temporal-spatial changes of landscape structure and pattern in the coastal wetlands are obvious. Landscape structural changes appeared the trends that the reed swamp expanded continuously and the area of spartina marsh decreased. The areas of reed marshes and Spartina alterniflora marsh by the manual management increased by30.92% and352.61%, respectively, while that of Suaeda marsh decreased by78.81%; the areas of reed marshes and Spartina marsh area under natural conditions, increased of368.25%and96.63%, respectively. While that of Suaeda marsh decreased by60.96%.On the aspect of landscape pattern, it appears that reed marsh expanded to the sea and Spartina alterniflora marsh expanded to the sea and land in both directions at the same time, and the Suaeda marsh contracted to the center. Among these, in human activities area, the expansion speed of reed marshes is240m/year, that of Spartina alterniflora marsh are40m/year and61m/year to the sea and land, respectively, and the expand to land is the main trend. The contraction speed of the Suaeda marsh from land and sea are61m/year and240m/year, respectively, and expand to sea is the main trend. In natural conditions, the expansion speed of reed marshes is162m/year, and that of Spartina alterniflora marsh to land and sea are117m/year and40m/year, respectively, and the main treed is to sea. The contraction speed of Suaeda marsh from land and sea are30m/year and162m/year, respectively, and the main trend is contracting to the sea.(2) Soil properties are the main elements that controlling the landscape type spatial differentiation and the soil moisture and salinity spatial differentiation are the dominant factor affecting the evolution of landscape types. Overall, the direction from land to sea, the soil moisture and salinityof the reed swamp, Suaeda marsh, and Spartina alterniflora marsh, showed an increasing trend. In the dry years, the average soil moisture content of the reed marshes, Suaeda marsh and Spartina alterniflora marsh are38.83%,41.79%and46.97%in human management areas, respectively. And the salinity average contents in these three landscapes are0.39%,0.71%and1.76%, respectively. In wet years, the moisture content of the corresponding landscape types are slightly increased of0.44%,4.09%and1.51%, respectively, and salinity are decreased by28.21%,36.62%and32.39%.In the natural conditions area, in dry years, the average soil moisture contents of the reed marshes, Suaeda marsh and Spartina alterniflora marsh are36.79%,40.70%and44.16%, respectively, and the average salinity contents are0.43%,0.93%and1.34%, respectively. In the wet year, the soil moistures of the reed marshes and Spartina alterniflora marsh increased by5.60%and4.23%, respectively, and the soil moisture of Suaeda marsh reduced by0.69%, the salinity in all kinds of landscape types decreased, and the decreased number are11.63%,32.26%and35.07%, respectively.(3) The threshold effect is obvious by controlling the soil moisture and salinity of the coastal wetland landscape. The study results show that the range of threshold of soil moisture and salinity are different in different landscape types. The scope of the soil salinity for the reed swamp is0.15%～0.53%, and that of the soil moisture is33.11%～42.28%; the scope of the soil salinity of the salsa swamp is0.53%～0.89%, and that of the soil moisture is33.11%～48.63%; the scope of the soil salinity of the spartina marsh is0.89%-1.44%, and that of the soil moisture is26.42%-55.33%; the scope of the soil salinity of the optical flat is0.31%～0.89%, and that of the soil moisture is48.63%-66.59%.(4) A simulation model of landscape evolution was constructed based on the process through using the spatial distribution data of regional landscape structure and soil properties data. The model not only possesses an ability of visualizing thedynamic changes of the spatial and temporal evolution, but also can reveal the evolution mechanism for the regional landscape from the perspective of the changeed landscape ecological processes. Based on the validation, the model showed a high accuracy in simulating the regional landscape evolution, and the overall accuracy can reach up to85%, and even more.(5) According to the characteristics of regional development and landscape changes, three different scenarios were designed, and the regional landscape evolution was simulated and predicted by using landscape process models in the coastal wetlands. The scenario simulation of the status quo mode (scenario I) shows that the Suaeda swamp is most affected types in the wetlands. Under the trend of the continued rapid expansion of reed marsh and Spartina alterniflora marsh, the Suaeda swamp will almost disappear in2025in the artificial management area. The Suaeda marsh will disappear in2030in the natural conditions area. The scenario simulation of the ecological recovery mode (scenario II) shows that the decrease trend of the Suaeda marsh area will be slow, and the area of the Suaeda marsh will increased by10.67times compared to scenario I in the artificial management area under the removal of the dam’s influence to2020. Under the scenario of the artificial restore area, the area of reed swamp will increase3.53%, and the area of the Suaeda marsh will increase150.07%compared to scenario I, the area of the Spartina marsh will decrease by7.90%compared to scenarios I in the natural condition to2020. The scenario simulation of protecting the local species Suaeda mode (scenario III) shows that controlling the expansion of the Spartina landward to2020, the area of the Suaeda marsh in human management areas and natural conditions will be3.26times and5.46times compared with scenario I. If removal the scenario of the Spartina mash, the area of the Suaeda marsh are7.24times and20.65times compared with scenario I in human management areas and natural conditions, respectively. |
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