云南松楚雄腮扁叶蜂幼虫在表土层的空间分布特点及理论抽样数

楚雄腮扁叶蜂是云南省的一种重要的针叶树食叶害虫,云南松是其主要寄主树种。为了解云南松楚雄腮扁叶蜂幼虫在表土层的空间分布格局,运用聚集度指标、Lloyd幂法则以及Iwao的m^*-m回归分析法进行了测定和分析。结果表明:无论是方位还是土层深度,楚雄腮扁叶蜂幼虫在表土层为聚集分布,其空间分布格局符合负二项分布; 楚雄腮扁叶蜂幼虫集中分布在0～10 cm深度表土层中,其幼虫在水平和垂直方位表土层中的平均虫口密度间差异不显著。根据空间分布参数,建立了精度分别为0.1、0.2和0.3时的理论抽样模型,依次为N_0.1=6 788.11/m+3.85,N_0.2=1 697.03/m+0.96,N_0.3=753.98/m+0.43。该模型适用于不同虫口密度下的楚雄腮扁叶蜂幼虫林间抽样,当其虫口密度为20、50、80头/m²时,可分别计算出应取样86、35和22个样方。

Spatial distribution characteristics and theoretical sampling of Cephalica chuxiongnica larvae on overburden in Pinus yunnanensis forest

Cephalcia chuxiongnica is one of the important defoliator pests in coniferous forest in Yunnan province, and which mainly infested Pinus yunnanensis. The spatial distribution pattern of C. chuxiongnica larvae on topsoil in P. yunnanensis stands was surveyed and determined using aggregated indices and Iwao’s m^*-m regression mode and power law of Lloyd. The results showed that C. chuxiongnica larvae was the pattern of aggregative distribution. The spatial distribution pattern of C. chuxiongnica larvae could be described by negative binomial distribution. Investigation result of horizontal distribution and vertical distribution showed that there was no significant difference in larvae density of C. chuxiongnica on overburden in P. yunnanensis forest. Theoretical sampling equations were N_0.1=6 788.11/m+3.85,N_0.2=1 697.03/m+0.96,N_0.3=753.98/m+0.43, which were the estimated sample size for different densities of larvae with an accuracy of 0.1, 0.2 and 0.3, respectively. These results provided a basis for the scientific sampling of C. chuxiongnica larvae in the forest. According to the above equations, 20, 50 and 80 sampling units should be sampled when the density of C. chuxiongnica is assumed to be 86, 35 and 22 individuals per sampling unit.