Study On The Habitats Of Oncomelania Hupensis In The Typical Wetlands Of Poyang Lake Based On Remote Sensing Environmental Indicators

Grass Island of Poyang Lake is the main area for the snail breeding in Jiangxi Province.Oncomelania as the only intermediate host of schistosomiasis,Snail habitats and environmental factors are closely related,Its distribution has obvious regional,In recent years,due to the low and dry water level of Poyang Lake,the snail breeding area has the tendency of low altitude expansion.Therefore,to explore the environmental factors closely related to the snail breeding in Poyang Lake,and analyze the dynamic change trend of the snail breeding ground is of great significance for achieving the schistosomiasis control objectives in the Poyang Lake region as soon as possible.This article uses Poyang Lake National Nature Reserve as a research area,First,the Landsat8 data of the entire lake scale was used to invert NDVI、LST and TCW Correlation analysis was used to analyze the correlation between oncomelania density,presence of screw-on frame with NDVI、LST and TCW and DEM.Then,the remote sensing environmental indicator threshold range of the snail breeding environment was obtained.Secondly,using the object-oriented classification method,we extracted the habitats of snails that were exposed from September 2016 to July 2017 in the study area,and obtained the ruleset of snails habitats in the study area,which realized remote sensing dynamic monitoring of snail habitats in the year;Finally,the influencing factors of the temporal and spatial dynamic changes of the snail breeding ground were discussed,and a reasonable prospect was proposed for the application of remote sensing method to study the distribution of snail breeding ground in the later period.The results of the study show that:（1）The density of snails in Poyang Lake was closely related to vegetation and elevation.The snail situation in Poyang Lake in the autumn of 2015 was significantly associated with its NDVI and DEM at its breeding sites.The correlation between the average density of live snails and NDVI was 0.665（P<0.01）,and the correlation with the DEM was-0.62（P<0.01）.The correlation between the occurrence rate of the snail frame and NDVI was 0.742（P<0.01）and the correlation with DEM was-0.632（P<0.01）;Snail density increases with the increase of vegetation index（NDVI）,8.5¹1 m elevation is the expansion area of snail breeding.（2）The use of Object-oriented classification has practical significance for the extraction of snail breeding grounds from the low dry water level to the high water level in the study area.Spatio-temporal change of the snail habitat in the Poyang Lake National Nature Reserve has a significant correlation with the water level at the Xingzi station in the same period.From September 2016 to July 2017,the areas of upper sparse snail belt and concentrated snail belt generally showed a trend of“low-stability-low”,and the volatility of the area lower sparse snail belt and expansion area of snail first increased and then decreased.On February 11^th,2017,the minimum level of Xingzi was 8.34 m,and the most exposed was the grass island.The maximum range of snail breeding area was 192.26 km²,accounting for 53.17%of the total area of the entire study area.（3）During the entire study period,the distribution of snail habitats has typical regional characteristics.In the study area,from the southwest to the northeast,The spatial distribution pattern of snail habitat shows that the distribution of upper sparse snail belt and concentrated snail belt converges to the concentrated distribution of lower sparse snail belt and expansion area of snail,The distribution of snail habitats in the nine disk-shaped lakes showed a ring-like and band-like distribution along the lake core to the lake shore.Lower sparse snail belt are mainly distributed in grassland in the low elevation areas of Banghu Lake and Dachahu Lake.The oncomelania expansion zone is mainly distributed in the low-grassland of each sub-lake,depression,or channel canal,and is mainly distributed on the north and east coasts of Banghu Lake and Dachahu Lake,as well as Xiu River,tributaries of the Ganjiang River,and floodplains and scattered lakes.The concentrated snail belt are mainly distributed in the mid-high elevation areas of the 9 disk-shaped lakes;Due to the limitation of elevation,upper sparse snail are mainly distributed on the southwest shore of the Shahu Lake,the west bank of the Dahu Lake,and the high elevation areas of the Xiu River,the tributaries of the Ganjiang River,and the ditches.（4）The hydrological situation is the main factor affecting the temporal and spatial distribution of the snail habitat in Poyang Lake.The elevation distribution of the disk-shaped lakes in the study area has a significant effect on the spatial distribution of the habitat of snails.The dynamic response of Vegetation on Poyang Lake beach to the hydrological situation is likely to have an impact on the spatial and temporal distribution pattern of the snail habitat.