褐梗天牛幼虫和成虫空间分布的地统计学研究

褐梗天牛(Arhopalus rusticus Linnaeus)是一种对松、杉、柏等林木危害非常严重的蛀干害虫,主要危害针叶树的衰弱木以及火灾后的枯立木,是继松褐天牛之后携带拟松材线虫能力最强的蛀干害虫。为了更好地控制其危害,深入地研究其种群空间格局,运用地统计学方法分析了3块受害程度不同的油松林内褐梗天牛幼虫和成虫的空间分布特性。结果表明:3种受害程度不同的林分内,褐梗天牛的危害具有显著差异,轻度受害林分内有虫株率为30.8%,中度受害林分内有虫株率为44.3%,而重度受害林分内高达78.3%。根据变异函数曲线图分析得知:轻度受害林、中度受害林和重度受害林内褐梗天牛幼虫种群空间分布最优拟合模型分别为高斯模型、高斯模型和指数模型,成虫的种群空间分布最优拟合模型均为线性模型。在3种林分中褐梗天牛幼虫数量具有明显的空间依赖性,轻度受害林、中度受害林和重度受害林内幼虫数量的空间依赖范围分别是19.10、11.97、61.98m,其空间连续性强度分别是0.646、0.784和0.500;成虫的空间依赖范围分别是43.08、43.23、44.17m,其空间连续性强度分别是0.044、0.021和0.171,但其成虫的数量在空间呈随机分布,没有表现出空间依赖性。根据垂直分布图分析得出:褐梗天牛幼虫和成虫在油松上主要集中聚集在某个高,然后随着高度增加密度降低,随着高度接近地面密度也降低。用Kriging插值法生成的空间分布图显示幼虫在空间分布上具有明显的聚集性,其聚集中心主要集中在林地中心,由林地中心株向整个林地扩散,而成虫则表现为随机分布。

Geostatistical analysis of the spatial distribution of Arhopalus rusticus larvae and adults

Arhopalus rusticusis an important wood-boring pest that can cause considerable damage to species of the genera Pinus,Cunninghamia,and Cupressus,mainly in weak conifers and dry wood after fires, which have the strongest likelihood of supporting Bursaphelenchus mucronatus and Monochamus alternatus. To effectively control this insect, and to confirmthe spatial distribution of its population, spatial characteristics were analyzed using Go-statistical methods for A. rusticus larvae and adults in three Pinustabulaeformis woodlands with different levels of damage. The results showed that the degree of damage caused by A. rusticus differed significantly in the three woodlands. In lightly infested woodland, 30.8% of trees were infested, whereas 44.3% and 78.3% of trees were infestedin moderately and heavily infested woodlands, respectively. Isotropic variogr amanalysis indicated that Gaussian models were suitable for simulation of the spatial distribution of A. rusticus larvae in lightly andmoderately infested forests, while, the Exponential modelswere suitable for heavily infested forests. In contrast, linear models were suitable for simulation of the spatial distribution of A. rusticus adults in lightly, moderately, and heavily infested forests. The quantity of larvae showed evident spatial dependence in the three woodlands, with the distances of larval spatial dependence for lightly, moderately, and heavily infested forests being 19.10, 11.97, and 61.98m, respectively, and the related intensities of local spatial continuity being 0.646, 0.784, and 0.500, respectively. The distances of adult spatial dependence for lightly, moderately, and heavilyinfested forests were 43.08, 43.23, and 44.17m, respectively,and the corresponding intensities of local spatial continuity were 0.044, 0.021, and 0.171, respectively. The number of adults was, however, randomly distributed in space, and did not show spatial dependence. Analysis of the vertical distribution of A. rusticus indicated thatlarvae and adults preferred to congregate at a certain height in Pinus, whereas above and below this height, the density decreases. In lightly infested woodland, the largest number of larvae were found at a height of 24-25cm, whereas the largest number of adults was found at a height of 4-5cm; in moderately infested woodland, the largest number of larvae were found at 9-10cm and the largest number of adults at 26-27cm;and in heavily infested woodland, the largest numberof larvae were found at 13-14cm, and the largest number of adults at 5-6cm. The spatial distribution pattern generated by Kriging interpolation showed thatthere was intensivespatial aggregation of larvae in all three types of woodland, and that the aggregation was primarily centered in the center of the woodland and spread from there into the entire woodland. In contrast, adults showed a random distribution.