Analysis Of Marsh Wetland Change And Ecosystem Service Value In The Sanjiang Plain

Marsh land is a multi-functional ecosystem with semi-continental and semi-continental transition formed by land-water interactions.It has the dual attributes of terrestrial and aquatic ecosystems,and it is also a human living environment with biodiversity.At present,the wetlands of swamps are rapidly reduced with the interference of natural factors and human factors.They are threatened by human pressure and caused widespread concern from all walks of life.Marsh lands are extremely sensitive to global change factors and human activities,and their ecosystems are very fragile.Sanjiang Plain is one of the largest natural marsh distribution areas in China and an important supply base for commodity grain in China.A number of marshlands have been reclaimed as farmland due to the increase in the local population and the impact of policies on the mountain and the countryside.In this paper,we used the Corona image of 1965 and the Landsat image of 2015 as data source to judge the change in the land use structure of the Sanjiang Plain,the quantitative analysis of the landscape pattern index was performed for the significant changes in the landscape types of the Sanjiang marsh wetland,and the ecosystem service value table was also revised.To clarify the ecosystem service value of Sanjiang Plain marsh lands and the temporal and spatial characteristics of their changes,provide a theoretical basis for the management of marsh wetlands in the Sanjiang Plain,provide some reference for the evaluation of ecosystem service value,and provide protection for wetlands and the sustainability of ecosystems.The main results are as follows:(1)Between 1965 and 2015,the land use structure in the Sanjiang Plain region has undergone significant changes.The main landscape types have changed from swamps to paddy fields.Land use changes are mainly reflected in the rapid increase in water areas,construction land,paddy fields,dry land and unused land,and the rapid decline in forest lands,grasslands and swamps.Most of the swamps are converted into paddy fields,followed by conversion to water and dry land,and a small portion converted to forest land,grassland,construction land and other unused land;(2)Analysis of the landscape pattern index shows that the landscape of the Sanjiang Plain changed from the original wetland substrate to the current farm substrate.The paddy field has become the main type of land use in the Sanjiang Plain.Simultaneously with the decrease in the number of patches in the swamp during the study period,The distribution is more concentrated,forming a gradual decline in the degree of fragmentation of marsh landscapes throughout the region,indicating that the landscape pattern of the study area is moving in a simplistic direction.However,the decrease in the shape index of the swamp and the increase in the average patch area also reflect the fact that the swamps in the Sanjiang Plain have been destroyed by large areas and the reclamation has affected the ecological environment.As a result,people’s awareness of the protection of swamps has increased.The swamps have been protected and the conversion of farmland to grassland has been started.The measures of reforestation and returning farmland to wetlands have yielded remarkable results,which have reduced the decline of swamp area to some extent;(3)The value of ecosystem services in the study area decreased significantly.Through the analysis of the changes in the service value of different ecosystem functions,it was found that only the grain production function improved,while all other ecosystem functions showed a downward trend.In other words,the rapid increase in the ecological function of food production is at the cost of a decline in other ecological functions.If this trend continues,the ecological environment in the study area will certainly deteriorate.At the same time,the analysis of changes in ecosystem service values in different geographical categories shows that except for swamps in Sanjiang Plain,grassland is the type of land use with the most reduced ecosystem service value in the study area.Therefore,based on the protection of current swamps and forests,grassland protection and Recovery should also be a matter of priority in the future.