| Aquatic vegetation is an important part of the lake ecosystem,generally found in shallow near-shore areas,with ecological functions such as wind and wave suppression,water stagnation,sediment fixation and algae reduction,playing an irreplaceable role in maintaining the balance of the lake ecosystem,promoting material circulation and purifying water bodies.At the same time,as a primary producer of lake ecosystems,aquatic vegetation is an important indicator for monitoring the health of lake ecosystems.The Heilongjiang River Basin(Chinese part),which includes all of Heilongjiang,most of Jilin and northeastern Inner Mongolia,is a base for growing commercial grain and cash crops in China and has a long history of industrial development.At the same time,it is also one of the most concentrated areas in China in terms of lake distribution,and the deterioration of the ecological environment of the lakes can have an impact on the lives of people living in the cities around the lakes,restricting the economic development of the surrounding cities and affecting the regional environment.Therefore,monitoring the aquatic vegetation of lakes in the Heilongjiang River Basin(part of China)and constructing a dataset on the spatial distribution of aquatic vegetation in this region over a long time series is the basis for research and protectionof lake ecosystems.Satellite remote sensing technology has the advantages of being fast,objective and repeatable,and is currently the most commonly used technical tool for monitoring aquatic vegetation in lakes.However,the amount of satellite data required for long time series and large scale remote sensing monitoring is huge,and traditional remote sensing technology means are difficult to process such a huge amount of data quickly and effectively.With the rapid changes in network and computer technology,cloud storage and cloud computing technologies have been rapidly developed.The Google Earth Engine(GEE)cloud platform integrates Landsat,MODIS and Sentinel and other commonly used remote sensing data sets,and processes and applies remote sensing data directly in the cloud platform,thus eliminating a large amount of data download,pre-processing data and other This can greatly improve the efficiency of remote sensing data application.This paper completes the extraction of aquatic vegetation and water bodies of lakes larger than 20 km2 in the Heilongjiang River Basin(Chinese part)from 1985 to 2020 based on the GEE platform and random forest algorithm,and analyses the process of changes in the spatial distribution of water bodies and aquatic vegetation in these lakes over the past 30 years.The following conclusions were drawn from the study:(1)The area of water bodies and aquatic vegetation of lakes larger than20 km2 in the Heilongjiang basin(Chinese part)has shown an overall trend of shrinkage in the last 36 years,with the total area shrinking from 3569 km2 and 758km2 to 3447 km2 and 697 km2,with the largest and most significant changes in the area of aquatic vegetation in Hulun Lake,Lianhuan Lake and Chagan Lake.(2)The direction of mass migration of water bodies and aquatic vegetation in lakes larger than20 km2 in the Heilongjiang River basin(Chinese part)during 1985-2020 is basically opposite,with the mass centres of water bodies and aquatic vegetation migrating in a southeasterly and northwesterly direction respectively.(3)Anthropogenic factors are the main cause of changes in the dynamics of aquatic vegetation in lakes,while meteorological factors affect the distribution of aquatic vegetation to a certain extent and the correlation between changes in the distribution of aquatic vegetation and meteorological factors varies from region to region.Xiaoxingkai Lake show asignificant negative correlation between aquatic vegetation and the area of water bodies,while the area of water bodies and aquatic vegetation in Chagan Lake shows a highly positive correlation. |
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