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钉螺是血吸虫的唯一中间宿主,与众多地理因子一样,钉螺的空间自相关具有明显的尺度效应。在湖沼型血吸虫病疫区典型洲垸型草洲选择一块50 m×50 m的试验样地,采用推扫式全覆盖方法进行了钉螺普查。用全局空间自相关Moran I指数、局部空间自相关Moran散点图和局部Moran’s I指数,进行了钉螺分布空间自相关的样点尺寸效应研究。结果表明:所有样点尺寸钉螺数目的全局Moran’s I均为极显著空间正相关(P<0.001);不同样点尺寸下的钉螺样点在局部自相关Moran散点图上绝大多数集中分布在象限1和象限3内,表明试验样地的钉螺呈空间聚集分布;钉螺样点尺寸越小,用局部Moran’s I指数对单个钉螺样点附近的空间自相关表现得越细微,表明全局Moran’s I指标会掩盖实际存在的局部空间自相关与全局不一致的现象。
Snail is the only intermediate host of Schistosoma japonicum. Like many geographic factors, the spatial autocorrelation of Oncomelania snails has obvious scale effect. In the lakeshore schistosomiasis endemic area typical embankment grassland select a 50 m × 50 m plots, using push-pull full coverage snail snail investigation. Using the global spatial autocorrelation Moran I index, the local spatial autocorrelation Moran scatter plot and the local Moran’s I index, we studied the sample size effect of snail spatial autocorrelation. The results showed that the global Moran’s I of all sample size snails were significantly and positively correlated with each other (P <0.001). Most samples of snail samples at different sample sizes were concentrated on the Moran scattergram of local autocorrelation Quadrant 1 and quadrant 3, indicating that the snails in the experimental plots were spatially aggregated and distributed. The smaller the snail sample size, the finer the spatial autocorrelation of a single snail sample with the local Moran’s I index, indicating that the global Moran’s I index Will cover the actual existence of local spatial autocorrelation and global inconsistency.