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目的探讨钉螺空间分布格局的样点尺寸效应。方法对江西省鄱阳湖区的试验样地进行“推扫式”钉螺调查,获得试验样地以0.33 m×0.33 m为基本单元大小的连续覆盖钉螺调查数据。以不同格点数目组合为不同的假想样点尺寸,运用聚集度指标、回归分析和聚集因子指数进行钉螺空间格局测定。结果钉螺种群空间格局为聚集分布,样点尺寸越小越能反映出钉螺种群的空间聚集;回归结果表明钉螺主要以个体群形式分布,且相互吸引,聚集强度与钉螺密度有关;种群聚集均数表明,钉螺的空间聚集与钉螺习性和环境因素或钉螺自身的聚集行为等有关,其中由生物习性导致的聚集行为用小样点尺寸可以得到更好的测定。结论湖沼型血吸虫病流行区钉螺空间分布格局为聚集分布,样点尺寸不同会影响到生物指标的测定结果。
Objective To explore the sample size effect of snail spatial distribution pattern. Methods The samples of Poyang Lake in Jiangxi Province were investigated by “push-brooming” and “snail-feeding” surveys, and the data of continuous coverage of snails were obtained with the unit size of 0.33 m × 0.33 m. The number of different grid points was combined into different imaginary sample sizes, and the spatial pattern of snails was determined by using aggregation index, regression analysis and clustering factor index. Results The spatial distribution of Oncomelania hupensis population was aggregated. The smaller the sample size, the more the spatial aggregation of Oncomelania snails population was reflected. The regression results showed that the Oncomelania snails distributed mainly in individual groups and attracted each other, and the aggregation intensity was related to the snail density. The results showed that the snail space aggregation was related to snail habitat and environmental factors or snail’s own aggregation behavior. The aggregation behavior caused by biological habits can be better measured by the sample size. Conclusion The spatial distribution pattern of snails in the lakeshore schistosomiasis endemic area is agglomeration distribution. The different sample sizes will affect the biological indicators.