Abstract:

Objective  To study the spatial autocorrelation on the small-scale distribution of On-
comelania hupensis in marshland and lake regions.  Methods   A bottomland was randomly selected
from the Qiupu River in Guichi District, Chizhou City, Anhui Province, and the selected bottomland
 was divided into three parts according to the distance from the Qiupu River (riverside, middle and
roadside). The two parts of the riverside and middle in the bottomland were selected as the study
field for not being affected by external matters. The snails were censused carefully and the sample
 size was 100 frames respectively.  All the snails were brought back to the laboratory to distinguish
whether they were alive or not and tell mature snails from young snails. During the snail surveying,
 10 soil samples were also randomly collected from the two parts of the riverside and middle in the
 bottomland, and their humidity were measurecL The soil humidity and snail density were calculated
respectively, and the multiple comparisons were also performecL Finally, the values of Moran,s I
and Geary' s C statistic were calculated to test whether Oncomelania hupensis had spatial autocorrela-
 tion,  and how it changed   Results   Oncomelania hupensis had positive spatial autocorrelation, which
 changed consistently with snail density.  The values of Moran' s I statistic were all greater than 0. 22,
and the values of Geary' s C statistic were all less than 0. 76,  and their P values were all less than
 0.01.  Spatial autocorrelation of Oncomelania hupensis in the riverside of the bot-tomland was greater than that in the middle of the bottomland before floods, but less than that in themiddle of the bottomland after the floods.  Spatial autocorrelation of the young snails was greater than
that of the mature snails in both the riverside and middle of the bottomland  Conclusion   Positive
spatial autocorrelation exists on the small-scale distribution of Oncomelania hupensis in marshland
and lake regions.

Key words: Oncomelania hupensis ; , Spatial autocorrelation; , Spatial statistics; , Marshland and lake regions

摘要：

目的研究湖沼地区湖北钉螺小尺度分布的空间自相关性。方法从安徽省池州市贵池区的秋浦河沿岸随机选择一个滩地的中间层和河边层作为研究现场，采用交叉复核随机抽检的查螺方法于滩地水淹前后各普查钉螺100框，判别死活，并分辨成螺和幼螺。在两层内各随机取10份土壤样本，测量土壤湿度。先计算并比较水淹前后两层的土壤湿度和钉螺密度，然后计算Moran'sI和Geary's C两个空间自相关指标，探讨钉螺的小尺度分布情况及是否存在空间自相关。结果钉螺的小尺度分布始终存在正空间自相关，其变化与钉螺密度的高低一致。Moran,s I均>0. 22，Geary，s C均<0. 76，P<O. 01。水淹前，河边层钉螺的空间自相关大于中间层；水淹后，中间层幼螺和成螺的空间自相关均大于河边层，并且同一层内幼螺的空间自相关均大于戍螺。结论湖沼地区湖北钉螺的小尺度分布存在正空间自相关。

关键词:  湖北钉螺；空间自相关；空间统计；湖沼地区