The Landscape Biodiversity And Assessment Of Water Enviroment Function Of The Wetland In Ubanization Area

Wetlands have the richest biodiversity on the Earth's ecological landscape and are one of the most important environments inhabited by humans;they are one of the world's three major ecosystems(the other two are forests and oceans).Wetlands are regarded as "the Earth's filtration system".China is in the process of rapid urbanization,and many wetlands have been transformed into urban wetlands.Urban wetlands are often the product of urbanized process,which plays an important role in the transformation and migration of pollutants,surface water storage,improving urban water quality and adjusting urban microclimate.Therefore,urban wetlands are widely used in urban ecological construction.Because the urbanized process has a significant impact on the structure and catchment of wetlands,so the ecological functions of wetlands have changed dramatically.How to evaluate the wetland's ecological functions is important to scientifically understand urban wetlands and reasonably utilize and protect urban wetlands.Taking the typical wetlands in eastern suburb of Nanjing as examples,we used RS(Remote Sensing)?GIS(Geographic Information System)and field investigation to classify the urban wetland and study the landscape biodiversity and water environment characteristics of urban wetlands.On this foundation,we developed the functional index and model to evaluate the water environment functions of wetland.The main research findings include:(1)Under the influence of urbanization,the patch characteristic of urban wetland had great changes.The area of rural wetlands were larger,with complex shapes and better vegetation cover,and the revetments were mainly nature.The area of sub-urban and urban wetlands were small,the shape were more regular,with less vegetation cover,and the revetment were mainly impacted by human activities.The landscape diversity characteristics in the watershed in different types of wetlands had great differences.With the impact of urbanization increased,the landscape types of wetland dominated by single landscape type become gradually equalization,and the degree of landscape heterogeneity and fragmentation increased.(2)The basic features of urban wetland's water environment showed that the regularity of water level fluctuation was significant,the water quality was poor and the seasonal variation was significant.Different types of wetland had obvious differences of water environmental characteristics.Compared to sub-urban and urban wetlands,the water level fluctuation of rural wetlands waved significantly.The water quality of rural wetlands were better,and sub-urban and urban wetland were poorer.With the impact of urbanization increased,the water quality of wetland becomed gradually poorer.(3)Considering the two factors of ecological system of wetland and landscape diversity,we developed the water environment functional assessment model of urban wetland.The water environment functions of the urban wetlands showed obvious degradation due to urbanization.Compared to reference wetlands,the WEFI(Water Environment Function Index)score for the urban wetlands declined by 34%.In the sub-index of WEFI,the FCI(Functional Capacity Index)score of water purification function for the urban wetlands declined by 19%,the FCI score of the hydrological adjustment function declined by 37%,and the FCI score of the water storage function declined by 47%.In addition,the water environment functions of different urban wetlands showed obvious differences because of the impact of the complex urbanized landscape.The different water environment functions between different types of urban wetlands had great changes.Compared to reference wetlands,the WEFI score of rural wetlands declined by 30%,and the WEFI score of sub-urban and urban wetland decreased by 36%.