Geo-environmental Succesion Of Coastal Wetlands In The Modern Yellow River Delta

Wetland is called ”the kidney of the earth”,is one of the nature's ecosystems that owns the most rich biological diversity and it also one of the most important human living environment.It's playing an important role in regulating climate,water conservation,biodiversity conservation and provide resources for human production and living environment.etc.Coastal wetland is the joint produce of tidal process and freshwater input at a continental margin.It also under the control of various factors,such as biological process through biofilms,biotubation of sediments,fluctuation of currents and waves,organic enrichment in sediments,and closing of nutrient cycles.In the past decade,People have payed more attention on the research of wetland evolution.However,In particular,they focused on the evolution of dynamics of bacterial community,plant-soil system and biology.Coastal wetland still exist many geological problems unsolved.For example,the evolution from pro-delta to upper delta has not been reported,especially the influence of human activities on the wetland evolution process.The paleo-environmental reconstruction and study on responding mechanisms of the coastal wetlands can help further understand how the wetlands respond to the future environmental changes such as sea level rises,and thus we can have science-oriented approaches to coastal wetlands protections and management practice activities.The authors study sedimentary sequences formed since the last postglacial in the Yellow River Delta area,reconstruct paleo-environmental evolutions since nearly 10000 years ago,and analyze controls of the evolutions upon the coastal wetlands successions,on the basis of sedimentary observations,microfossils and dating data from five cores drilled in the Delta area in 2007,together with historic records and remote sensing data.The emphases are put on the discussions upon the deltaic progradation and wetlands successions,and also on the summarization of changes in ecology from aquatic systems to shallow sea wetland,tidal flat wetland and upper delta plain wetland systems and to terrestrial ecosystems.The method of comparisons between the modern and old Yellow River Deltas' situations is used to verify that climatic changes and human activities have accelerated and altered processes and directions of geo-environmental successions in the wetlands.The authors further put forward that the wetland successional rates became much faster after the year 1855 due to human activities,increasing by 8-33 fold compared with before.