栎黄枯叶蛾低龄幼虫空间分布的地统计学分析

栎黄枯叶蛾(Trabala vishnou gigantina Yang)是近年在陕西吴起发现的严重危害沙棘的一种食叶害虫。为了准确把握栎黄枯叶蛾幼虫的分布规律,以便对该虫的危害盛期进行预测预报和采取防治措施,因而采用地统计学分析方法对不同坡向和疏密度的沙棘林中栎黄枯叶蛾低龄幼虫的空间分布格局进行了研究。结果表明:栎黄枯叶蛾卵孵化高峰期为6月中旬。通过全方向的变异函数曲线分析得知:阴坡密林、阴坡疏林、阳坡密林、阳坡疏林中,栎黄枯叶蛾低龄幼虫空间依赖范围分别为19.96、9.45、20.75、13.48 m,空间变异值分别为0.692、0.613、0.679、0.597。密林样地的半变异函数最佳拟合模型均为高斯模型,疏林样地均为指数模型,两种模型均指明栎黄枯叶蛾低龄幼虫的空间分布格局为聚集分布。引起种群聚集的原因主要为其生物学特性。用Kriging插值方法生成的空间分布图显示低龄幼虫在空间分布上存在明显的边缘效应。

Geostatistic analysis on the spatial distribution of Trabala vishnou gigantina Yang early stage larvae

Trabala vishnou gigantina Yang have been a serious leaf-eating pest of Hippophae rhamnoides in the Wuqi county of Shaanxi in recent years. The spatial characteristics of T. vishnou gigantina early stage larvae were analyzed using geostatistical methods in H. rhamnoides forests with different slopes and densities, for forecasting and scientific management. The results showed that high levels of hatching occurred mainly in mid-June. Analysis of isotropic variograms indicated T. vishnou gigantina early stage larvae spaced themselves 19.96, 9.45, 20.75, and 13.48 m apart in densely forested shady slopes, open forests on shady slopes, densely forested sunny slopes, and open forests on sunny slopes, respectively, while the intensity of local spatial continuity was 0.692, 0.613, 0.679, and 0.597, respectively. Semivariogram analysis revealed the Gaussian model had the best fit in dense forest, while the Exponential model fitted best with the open forest, implying an intense spatial aggregation pattern of T. vishnou gigantina early stage larvae. The reason for aggregation was mainly its bionomics. As the maps with Kriging interpolation described, T. vishnou gigantina early stage larvae exhibited an obvious edge effect.