Study On The Environment Factor And Spatial Characteristic Of Oncomelania Snails' Distribution In Marshlands Of Dongtiong Lake Based On RS And GIS

The distribution of schistosomiasis is corresponds with the Oncomcelania Snails' distribution. The survival of Oncomcelania Snails relate closely to the environmental factors of habitats, therefore, the study on the relationships between the environmental factors and the distribution of Oncomcelania Snails are important to the prevention of schistosomiasis and control of Oncomcelania Snails.The unit of the remote sensing imagery, which is a digital database of environmental factors with excellent temporal and spatial references, and the great spatial analysis of the Geographic Information System (GIS), is regarded as a new useful tool to study the relationship between the distribution of Oncomcelania Snails and the surveillance of Oncomcelania Snails habitats. Based on the epidemiological investigation in 2004, the paper explores the characteristic of the Oncomcelania Snails' distribution, and the relationship between that and the natural environment by the method of GIS and remote sensing (RS).According to the investigation of the Oncomcelania Snails breeding area in 2004, the paper constitutes the GIS of the Oncomcelania Snails distribution area in marshlands of Dongting Lake region, which is regarding the digitized relief map of 1:50000 and the date from the remote sensing imagery as the spatial database, and taking the Oncomcelania Snails' distribution of Dongting Lake in 2004 as the attribution database.Based on the established GIS of the Oncomcelania Snails' distribution in Dongting Lake, the author analyzes the environmental condition of the Oncomcelania Snails' habitates comprehensively by the spatial analyzing technology. The results are as following: firstly, the predominant vegetation of Oncomcelania Snails habitat is reed and sedgy. The habitats with reed has a higher livability than with sedgy as dominating vegetation. However, the diffusion of Oncomcelania Snails is much serious in the habitats with sedgy. Secondly ,the predominant soil type of the Oncomcelania Snails breeding area is temporary submergic paddy soils, which is in weak acidity environment, of that PH value is 5.5--7.5, and the organic content is in 2---3%. Thirdly, the 80 percent ofthe Oncomcelania Snails breeding area, the normalized difference vegetation index (NDVI) of that is in 0.100-0.375%, and the soil humidity of that is in 0.202—0.507, and the distance to the water of that is in 10-230 meters. The results from the correlation analyses between the environmental factors and the Oncomcelania Snails' distribution indicates that there are positive correlations among the density of Oncomcelania Snails, Normalized difference vegetation index (NDVI) and the type of sedgy, and negative correlations among the density of Oncomcelania Snails, the PH value of the soil and the organic content of the soil.Using the GEODA and Arcgis to analyze the Oncomcelania Snails' spatial distribution of marshlands in Dongting Lake, the author gets some conclusions about Oncomcelania Snails' density:(Dthere is a spatial clustering model.(2)there is an intensely spatial autocorrelation, which is influenced by exception. (3)the variogram of the alive Oncomcelania Snails by the formula y(h) can be described as:f 0 h = Qy(h) = _^l_[7.0538(1 -e *????) h>0And then, based on the formula y(h) and the spatial characteristic of the density of alive Oncomcelania Snails in marshland of Dongting Lake, the paper establishes a prediction model to estimate the Oncomcelania Snails' distribution. Comparing with the trual distribution, the prediction model has a well coincidence and is feasible to predict.