| Wetland is an important part of the earth's ecosystem.It not only has the role of regulating climate and water source,but also maintains environmental functions and benefits such as biodiversity and soil erosion.In the past 100 years,64%of the total area of global wetland reduction(Ramsa Convention)has caused many ecological and social problems.Wetland vegetation is an important part of the wetland and has very important value,With the current state of wetland degradation,accurate dynamic monitoring of wetland vegetation is very important.Therefore,accurate monitoring of wetland dynamics from different scales and clarification of attribution have become the frontier issues of geography,environmental science and ecology.In this study,the border of Changbai Mountain area was used as the research area,and the long-range satellite remote sensing observation data was used to analyze the variation trend of vegetation coverage of different wetland types from the perspective of multi-scale spatial and temporal dynamic changes.The main conclusions are as follows:(1)Between 1982 and 2015,the average annual NDVI value of wetland vegetation in the border of Changbai Mountain area fluctuated between 0.41 and 0.47.Before 2000,the average annual variation of NDVI showed a slight downward trend,while after 2000,the upward trend was more obvious.From the perspective of different sub-basins,the annual average NDVI value of wetland vegetation in the Songhua River Basin fluctuates between 0.52-0.58,while the annual average NDVI value of wetland vegetation in the Yalu River Basin and the annual average NDVI value of wetland vegetation in the Tumen River Basin are both In the case of fluctuations,the NDVI values are approximately 0.39-0.43 and 0.7-0.84,respectively.(2)Between 1982 and 2015,the spatial slope value of wetland vegetation in the border of Changbai Mountain area was mostly greater than 0,which was about 68.73%(37.3%),showing an annual greening trend,indicating that the growth of wetland vegetation in the study area showed an improvement trend.·In the three sub-basins of the study area,the area of wetland vegetation slope>0 in the Songhua River Basin is about 73.40%(37.60%),and the wetland vegetation in the Yalu River Basin and the wetland vegetation slope>0 in the Tumen River Basin are only about 46.31%(36.25).%)and 4%(8%),indicating that only the growth of wetland vegetation in the Songhua River Basin shows an improvement trend.(3)Between 1982 and 2015,the average annual NDVI of herbaceous swamps and intermittent wetland vegetation in the border of Changbai Mountain area showed an upward trend.Only the annual average NDVI of coastal wetland vegetation showed a downward trend.The annual variation trend of herbaceous marsh vegetation is the most significant,especially the herbaceous swamp vegetation in the Songhua River Basin,followed by intermittent wetland vegetation,and the coastal wetland vegetation presents an annual negative change trend.The change degree of the slopes of the three wetland vegetations is combined with the change degree of the wetland vegetation slopes of the three watersheds.The changes of wetland vegetation in the three periods are consistent with the overall trend of the wetland vegetation in the basin.(4)Between 1982 and 2015,the annual average NDVI of wetland vegetation in the border of Changbai Mountain area showed an upward trend in both the concentrated precipitation and the dispersed precipitation.However,the average annual NDVI increase of the wetland vegetation in the dispersed precipitation was not significant At the same time,the annual greening trend of wetland vegetation in concentrated precipitation is generally higher than the season of scattered precipitation,indicating that the growth of precipitation wetland vegetation has promoted to a certain extent. |
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