Study On The Long-term Change Characteristics And Influencing Factors Of Poyang Lake Wetland Vegetation Based On GEE

Wetland vegetation is the basis of waterfowl habitat and fish breeding place,which can directly reflect the evolution of wetland.Moreover,wetland vegetation is an indicator that can intuitively reflect the evolution of wetlands.Wetlands are the most valuable and productive ecosystems on earth.Furthermore,wetlands can provide a variety of ecological services including global climate regulation,natural water purification,flood control and drought relief,and play an important role in regional ecological balance and security.Poyang Lake Wetland,as an internationally important wetland and the largest freshwater lake in China,is of great significance to my country’s ecological environment.Affected by various factors such as climate change and human activities,wetlands are suffering from a series of threats.The research on the change of wetland vegetation can directly reflect the change of wetland.Therefore,the study of temporal and spatial variation characteristics and influencing factors of wetland vegetation under the influence of a variety of factors has become the core issue of wetland ecosystem health diagnosis.The research is of great significance for scientific protection,management and use of wetland resources.However,due to the difficulty of data acquisition and time-consuming processing,the current research on the temporal and spatial evolution and impact of Poyang Lake wetland vegetation is mostly long-term changes in sparse time series or only research on intra-annual changes and influencing factors.There is a lack of long-term dense time series change characteristics analysis and research on influencing factors.Therefore,aiming at the scientific question of how long-term vegetation changes in Poyang Lake wetland and its influencing factors.This paper extracts the dense time series of Poyang Lake wetland vegetation information from 2000 to 2019 based on Google Earth Engine(GEE)remote sensing cloud computing platform,CART(Classification and Regression trees)classifier and Landsat series remote sensing images.And,study the long-term change characteristics of wetland vegetation in Poyang Lake.On this basis,combined with hydrological data,we analyze the relationship between wetland vegetation in dense time and water level changes series in different hydrological periods.Then quantitatively analyze the impact of meteorological factors on wetland vegetation changes through the geographic detector model,so as to fully understand the hydrological situation and meteorological factors how to effects on long-term changes of wetland vegetation in Poyang Lake.The main conclusions of this study are as follows:(1)The overall accuracy of vegetation information extraction of Poyang Lake wetland based on GEE platform and CART classification regression tree algorithm is higher than87%,and the Kappa coefficient is not less than 0.80,which meets the long-term accuracy requirements of vegetation information extraction of Poyang Lake wetland.(2)From 2000 to 2019,the average vegetation area of Poyang Lake wetland was857.00km~2,692.34km~2,187.88km~2 and 538.50km~2 in dry season,the rising water-level period,wet period and the receding water-level period,respectively.The maximum vegetation area appeared in the dry season in 2011,and the minimum value appeared in the wet season in 2010.The vegetation was mainly distributed in the lake center beach and around the disc lake.By calculating the spatial centroid of wetland vegetation in Poyang Lake,it is found that the spatial distribution of wetland vegetation in Poyang Lake has a trend of gradually evolving to the central area of the lake.(3)The vegetation area of Poyang Lake wetland was significantly affected by water level,and there was a negative correlation between water level and vegetation area.The influence of meteorological factors on vegetation change of Poyang Lake wetland was quantitatively analyzed by the factor detector of geographic detector.It was found that precipitation was the main driving factor of vegetation change of Poyang Lake wetland,and air temperature was the second major meteorological factor.Compared with meteorological factors alone,the interaction of different driving factors can better explain the long-term changes of Poyang Lake wetland vegetation with a higher degree of explanation.