Research On Vegetation Succession And Soil Organic Carbon Distribution Of Coastal Wetland In Yancheng

On the basis of remote sensing data of four time phases from 1992 to 2016,landscape classification was performed and types and distribution of wetland vegetation were analyzed for the coastline from Chuandong Harbor to Liangduo River mouth in Yancheng.The temporal and spatial evolution of coastal wetland vegetation was explored using transfer matrix method.Soil samples from the depth of 0-40 cm under different wetland vegetation was obtained every 10 cm.The soil particle size,organic carbon content and other parameters of these samples were measured to explore the influence of coastal wetland vegetation changes and its succession process on soil organic carbon content and distribution.The results indicated that:1)The dominant wetland vegetation types in the estuary from Chuandong Harbor to Liangduo River mouth are Couch grass?Artemisia halodendron?Phragmites australis?Spartina alterniflora.From 1992 to 2016,the total area of local vegetation decreased in general,during which time the Couch grass nearly disappeared.Meanwhile,the area of Artemisia halodendron and Phragmites australis continued to decrease while the growth of Spartina alterniflora boosted sharply.2)From 1992 to 2000,the area of vegetation rapidly reduced.Large areas of Couch grass,Artemisia halodendron were developed into cultivated land.From 2000 to 2009,aquaculture ponds occupied wetland vegetation area with an expansion of Spartina alterniflora.From 2009 to 2016,while Spartina alterniflora was expanding to the sea,it turned into a breeding pond on the land side due to pond development.3)Soil organic carbon contents under different vegetation types,growth status and distribution characteristics have distinguished characteristics.The content is highest under Spartina alterniflora,followed by Phragmites australis,Couch grass and Artemisia halodendron.On the vertical profile,the topsoil organic carbon content of Spartina alterniflora,Suaeda salsa and Phragmites australis communities was the highest,and decreased with the increase of depth,whereas grass communities shows opposite feature.There was a significant correlation between soil organic carbon content under vegetation community and soil particle size,that is,the larger the soil average diameter ? value,the finer the soil particle size,the higher the organic carbon content.4)The vegetation evolution from East Sichuan Port to Liangduo Estuary in Yancheng is a result of natural and human interaction.On the one hand,it is affected by the silting coast;on the other hand,it is impacted by various beach development activities with the guidance of government policy,as well as the rapid diffusion by the introduction of Spartina alterniflora.Correspondingly,coastal blue carbon disappeared with the reduction of vegetation due to large-scale reclamation but is also supplemented by the input of human activities and the expansion of wetland vegetation to the sea.