Remote Sensing Monitoring Of Dynamic Changes Of Important Wetlands In Northeast China

Wetland is called"the kidney of the earth"for its important role in regulating the dynamic balance of earth hydrology,maintaining the diversity and stability of ecosystems,and reducing the incidence of natural disasters.It is one of the most valuable natural resources on earth and its ecological function is irreplaceable by other ecosystems.The stability of wetland ecosystem is not only closely related to food yield and water resources,but also an important prerequisite for maintaining ecological balance,ensuring ecological diversity and protecting rare plants and animals.Wetlands in northeast China account for a large proportion of the country's wetlands,they are mainly scattered in the great and small Hinggan mountains,Sanjiang Plain,Songnen Plain,the southeast of the northeast region and other regions.Northeast China has delivered a large number of high-quality grains and vegetables,such as rice and corn,to the central and local governments of China.Northeast China is called“grain marketing regulator”,“the biggest commodity grain strategy reserve base camp”.The cultivation of grain and vegetable is directly related to wetland ecology.The wetlands in northeast China have suffered a lot for it.As the contradiction between the increase of population and the decrease of land resources becomes more and more significant,a large area of wetlands are reclaimed for farmland to grow more food or build more houses.The water pollution is becoming more and more serious and the water resources are becoming more and more stress,and the wetlands are being destroyed again and again.If we do not take corresponding measures to protect it and stop the trend of wetland deterioration,human life will be greatly affected in the future.Based on Landsat7 ETM+image data of 1990 and 2000,and 2019 Sentinel 2 a/B image data of remote sensing data sources,by maximum likelihood classification method,and Google earth assisted extraction of artificial interpretation method of combining the northeast to 21 important wetland nature reserve of China from 1999 to2019,the wetland information,grasp the present condition of wetland to 21,they can be divided into rivers,lakes wetland reserve wetland reserve,artificial wetland reserve,marsh wetland reserve four kinds of wetland reserves.Based on their area change,spatial-temporal dynamic change,area normalization analysis and transfer matrix analysis,this paper analyzes the dynamic change differences of various wetland reserves,and finally proposes specific improvement measures for the uniqueness of each wetland reserve.The following conclusions are obtained through the research of this paper:1.From the perspective of wetland area and dynamic changes,the total area of 21wetland nature reserves decreased from 14059.37 km~2to 12795.7 km~2in the last 30 years during the study period,with a decrease of 1263.67 km~2.Among them,river wetland reserve,lake wetland reserve and swamp wetland reserve all show the dynamic change of continuous wetland decrease,among which,the wetland area of constructed wetland reserve decreased the most dramatically from 1990 to 2000,mainly for swamp wetland decreased by 14%.Between 2000 and 2019,lake wetland reserves declined the most,and swamp wetlands declined by 5%.The constructed wetland is the dynamic change which reduces first and then stabilizes.2.The total proportion of the four types of wetland reserves in northeast China also changes.In general,the proportion of the four types of wetland reserves has always been swamp wetland reserve>lake wetland reserve>constructed wetland reserve>river wetland reserve.But the trends are not the same.During the periods from 1990 to 2000and from 2000 to 2019,the proportion of river wetland continued to decrease,the proportion of lake wetland continued to increase,and the proportion of constructed wetland reserve and marsh wetland reserve continued to decrease and then slightly recover.3.In the research period of the four types of wetland protection areas in northeast China,the wetland transformation direction is mainly cultivated land,followed by other lands.However,after 2000,the area of wetland converted into cultivated land decreased significantly,especially in the protected area of lake wetland and the protected area of constructed wetland.