Remote Sensing Montitoring Of The Dynamic Changes Of Nanweng River Wetland In The Nenjiang River Source Region

Wetlands are unique natural ecosystems located at the intersection of water and land,known as "kidney of the earth",It has very important and irreplaceable ecological service functions in terms of biodiversity protection and maintaining ecological balance.However,wetlands are also one of the most serious natural ecosystems disturbed by natural and human activities in the world,especially the rapid economic development and huge population pressure in China,the contradiction between human and land is prominent,and the problem of wetland resources being disturbed and destroyed is particularly serious,resulting in a series of natural and ecological environment problems,restricting economic and social development,and the information management and decision-making of wetlands in China need to be strengthened urgently.Cold region wetland is one of the most important wetland types in China.More than half of the natural wetlands in the whole country are cold region wetlands,and many of them are important water conservation areas in the source areas of rivers and rivers,which are of great value in ecological protection and utilization.The Nanweng River Wetland Reserve in the Nenjiang River source area is the main source of the Nenjiang River system.It is the only Forest Wetland Ecosystem in the cold temperate zone in China and the main habitat for many rare waterfowls.However,due to the relatively simple composition of the wetland ecosystem in the cold region and the weak system regulation ability,it is particularly sensitive to climate and environmental change.In recent years,the interference of climate warming and human activities has led to the acceleration of permafrost melting,at the same time,the forest water consumption has been greatly reduced,the degradation of high-level wet land is serious,and the wetland area shows an overall reduction trend.This has led to a series of ecological and environmental problems,such as the decrease of biodiversity,the aggravation of major natural and ecological disasters such as floods and droughts,and also led to significant changes in the hydrological process of downstream wetlands.Therefore,this study extracts the information of Nanweng River Wetland in the sourcearea of Nenjiang River in recent 40 years,and through the dynamic change research,correctly understands the change rule of Nanweng River Wetland in time and space,timely grasps the distribution and change characteristics of wetland resources,and provides the basis for wetland protection and scientific decision-making.This paper uses Landsat series satellite data,sentinel-1 radar and other remote sensing image data as well as other terrain auxiliary data,and according to the constructed wetland classification system of Nanweng River in Nenjiang River source area,extracts the distribution information of Nanweng River Wetland Resources in Nenjiang River source area,carries out the dynamic change research on the distribution pattern of Nanweng River wetland,monitors and analyzes the distribution characteristics of Nanweng River Wetland in Nenjiang River source area of Nenjiang River in the past 40 years.The research work and achievements of this paper are summarized as follows:(1)The wetland classification system of Nanweng River in the source area of Nenjiang River is constructed,and the information of wetland resource distribution is extracted.Based on the results of the field investigation,Refer to the criteria for wetland classification in "National Wetland Resources Survey and Monitoring Technical Regulations" and "Ramsar Convention",and construct the wet classification system of Nanweng River in the source area of Nenjiang River.The landscape types included in the study area are divided into the following seven types:Water Body,Broadleaf Forest,Cultivated Land,Herbaceous Swamp,Forest Wetland,Artificial Land,and Mixed Wood.Through the classification and extraction method of the constructed random forest model,the classification information of Nanweng River Wetland from 1976 to2018 is extracted.(2)Based on the random forest classification method,the overall classification accuracy of Nanweng River Wetland in the source area of Nenjiang River is more than88%,and Kappa coefficient is 0.84,the mapping accuracy of the seven land use types is more than 80%,of which the mapping accuracy of Herbaceous Swamp is more than85%,and the mapping accuracy of Forest Wetland is 91.79%.Generally speaking,this method can distinguish most types well.(3)The evolution law of wetland distribution pattern of Nanweng River in the source area of Nenjiang River in recent 40 years is deduced.During 1976-2018,thetotal area of Nanweng River Wetland in Nenjiang River source area was gradually reduced,Wetland transferred out is large,Forest Wetland degradation is serious,and the change of Herbaceous Swamp is small.Due to the influence of climate warming,the influence of temperature change on the middle altitude area in the study area is more obvious.The change of wetland is mainly stable in the range of 370-550 m above sea level.In 1976-1997 and 1997-2018,three types of Forest Wetland,Herbaceous Swamp and Water Body changed most obviously in the range of 400-450 m above sea level,among which the area of Forest Wetland decreased the most.In the past 20 years,human activities have increased significantly.With the construction of artificial land such as scenic spots and roads,the area of cultivated land has expanded rapidly,the shape of wetland landscape has become more complex,and the fragmentation of wetland landscape has intensified.The SHDI and SHEI of the study area showed some ups and downs.In the past 10 years,the SHDI and SHEI began to significantly reduce.The dominant landscape types of wetlands are becoming more and more degraded,and the biodiversity is facing a reduction.(4)According to the historical changes and current situation of Nanweng River Wetland in the source area of Nenjiang River,the protection suggestions are put forward.Based on the analysis of the change trend of wetland pattern of Nanweng River in the source area of Nenjiang River,this paper finds out the reasons that affect the change of wetland,and then from the construction of dynamic monitoring and management system of Nanweng River Wetland in the source area of Nenjiang River,the moderate reduction of human activities,the strengthening of management of wetland protection in cold areas,the expansion of publicity,the improvement of people’s awareness of wetland protection,and continue to strengthen the scientific research on the wetland in the cold region and put forward the protection countermeasures for the wetland in Nanweng River in the source area of Nenjiang River.