Characteristics Of Temporal-spatial Variation And Driving Forces Of Coastal Wetland In The Southern Coast Of Laizhou Bay

As an ecological marginal zone,coastal wetlands have high biodiversity,which not only can maintain the ecological service function,but also play an important role in protecting the coastline.Due to abundant resources,the development of coastal wetlands is very frequent.With the rapid economic development of China's coastal cities and the rapid increase in population,a large number of reclamation activities have caused the area of coastal wetlands to shrink continuously,and its own potential cannot be fully utilized,and ecological service functions have begun to degrade.Studying the temporal and spatial characteristics of coastal wetlands and their relationship with human activities is conducive to the scientific protection and management of coastal wetland resources,and is also of great significance to the sustainable development of coastal economics.In this study,the southern coast of Laizhou Bay was selected as the research area,and a suitable wetland classification system was established.Object-oriented classification methods were combined with human-computer interaction to visually interpret Landsat remote sensing image data in the research area.On the basis of ensuring high classification accuracy,the characteristics of the spatiotemporal changes of wetlands in the southern coast of Laizhou Bay in the past 30 years and the change trend of landscape index were analyzed,and the driving force of wetland changes was analyzed.The findings are as follows:(1)From 1987 to 2017,the length of the coastline in the study area increased by73.4km,and the total area propelled to the sea reached 75175.12hm~2.In the past 30years,under the influence of natural and man-made factors,the whole coastline of the study area has been mainly pushed to the sea.(2)From 1987 to 2017,the area of natural wetlands in the study area showed a downward trend,decreasing by 6565.41 hm~2,and the rate of change was 40.29%.The area of constructed wetlands is increasing,increasing by 50954.81hm~2,and the rate of change is as high as 110.13%.The overall area of non-wetlands did not change significantly,with a change rate of 0.23%.(3)From 1987 to 2017,the bare beach in the natural wetland in the study area has the largest transferred area,which is mainly converted into salt fields,breeding ponds and construction land.Salt fields has the largest transferred area in constructed wetland,which is mainly converted into agricultural land and construction land.Agricultural land has the largest transferred area in non-wetland areas,which is mainly converted into construction land.(4)From 1987 to 2017,under the condition that human beings are continuously pursuing economic benefits,the expansion of salt fields and construction land is very large,and many areas have been linked together.Porosity of bare beach and forest grassland patches decreased and their distribution became increasingly concentrated.The spatial heterogeneity of agricultural land increases and the degree of fragmentation increases.In addition,the landscape types in the study area show a trend of uniform distribution,mainly due to the increasing number of measures to protect and restore wetlands in recent years.(5)Through principal component analysis and grey correlation analysis,it is found that in the process of wetland changes in the past 30 years,human factors have more significant influence on wetland changes in the study area.Among them,the human factors that have the greatest impact on wetland changes in the study area are the output value of primary,secondary and tertiary industries,while the natural factors,precipitation,have the greatest impact on wetland changes in the study area.