Analysis On The Evolving Progress And Driving Force Of Estuarine Wetland Landscape Types

The Yellow River Delta wetland is the youngest wetland ecosystem in China's warm temperate zone.It is also the most intact and most extensive.In order to understand the changing of landscape pattern and their causes of these changes in the Yellow River Delta wetland,this study analyzes the dynamic changes of wetlands mainly based on five Landsat series of images,including MSS,TM,OLI sensor in 1976,1986,1996,2006,2016.Object-oriented classification and the combination of spatial feature,spectral feature and Normalized Difference Vegetation Index(NDVI),Normalized Difference Water Index(NDWI),as well as brightness characteristic indices were used to classify the images in eCognition.The dynamic changes,future trends and driving factors of the landscape types in the Yellow River Delta wetland were analyzed by the transfer matrix,landscape pattern index,prediction simulation model.The results of the study show that:(1)From 1976 to 2016,the total area of wetlands in the study area showed a decrease from 2594.76 km~2 in 1976 to 2491.79 km~2 in 2016.The area of natural wetlands decreased954.03 km~2.The human-made wetlands increased by 851.06 km~2.(2)During the dynamic evolution of the wetlands,the transformation of natural wetlands was extensive.31.34%of Suaeda heteropteras cover was transformed into reservoir and ponds.Some human-made wetlands were transformed into non-wetlands types,1.55%of reservoir and ponds were transformed to construction land.As the intensity of human activities increased,the number of landscape types in the study area also continuously increased.The landscape fragmentation and splitting index(SPLIT)increased mainly due to human activities,which cause an increase in the landscape shape index(LSI)and the perimeter area fractal dimension(PAFRAC).The contagion index(CONTAG)and aggregation index(AI)decreased.From the results of the simulation of the Yellow River Delta wetland in 2026,it can be seen that the number of natural wetlands and non-wetlands are reduced,and the number of human-made wetlands are increasing and continuously reaching shallow sea areas expansion.In general,the Yellow River Delta wetland is degraded,the area of natural wetlands are reduced,and the whole wetland patches tend to be fragmented,complicated,and non-connected.(3)Wetland degradation in the Yellow River Delta is mainly affected by both nature and human-made factors,and the anthropogenic factors are the dominant factors in the drastic change of landscape types in the Yellow River Delta wetland.The proportion of landscape types that have been affected by human disturbances in the study area has been increasing,and the impact rate of human activities has increased from 16.77%in the first 10 years to52.94%in the last 10 years.Farmland farming was the main human activity factor affecting the change of landscape types from 1976 to 2006.Between 2006 and 2016,the distribution of changes in natural wetlands area affected by various human activities is relatively balanced,and the proportion of transfer to reservoir and ponds is 34%.Farmland reclamation was the main influence in 1976-2016.The results help to improve the understanding of the characteristics and causes of the dynamic changes occurring in the Yellow River Delta wetland.It provides important information for the wetland management departments to strengthen the protection and restoration of the wetlands.