种群趋势指数的方差近似估计式及其应用

根据吴惠龙等（1986）发表的稻纵卷叶螟 Cnaphalocrocis medinalis 的生命表及 Watt 种群趋势指数数学模型,在delta-方法的基础上，本文提出了一种种群趋势指数方差的近似估计法，并应用于评价稻螟赤眼蜂Trichogramma japonicum Ashmead 及化学杀虫剂（甲六粉）对稻纵卷叶螟的控制作用。根据中心极限定律，当样本足够大时，种群趋势指数近似于正态分布。根据近似方差估计量以及 Z-检验方法，取得以下结论：放蜂区明显优于对照区，因其种群趋势指数取值较小，相应的 P 值为 0.0111，该区也明显优于化学杀虫剂处理区，相应的 P 值为 0.0036。杀虫剂处理区差于对照区，因其种群趋势指数值较大（0.3035），但这种差异并未达到显著水平，P 值为 0.2236。虽然本文的结论近似于吴惠龙等（1986）单纯依据种群趋势指数所得到的结果，但本文的结论更具统计意义，更加可靠。

An approximate variance estimator for index of population trend developed with delta-method and its application

On the basis of Watt's mathematical model of the index of population trend(I),an approximate variance estimator of I was developed with delta-method in this paper.Taking the natural population life tables of rice leaf roller Cnaphalocrocis medinalis(Lepidoptera:Pyralidae)published by Wu et al.(1986)as an example,it was applied in evaluating the control effectiveness of biological agent(Trichogramma japonicum Ashmead)and chemical insecticide(powder,1.5% mevinphos 3% alpha-hexachloro cyclohexane).By Z-test criterion,biologically and statistically sound conclusions were drawn that at the generation level,the suppression effectiveness of trichogramma wasp against rice leaf roller was better than the blank control with P=0.0111 and smaller I value(0.0390 versus 0.1768),and it was also statistically better than the insecticides with P=0.0036 and smaller I value(0.0390 versus 0.3035).The insecticides was not statistically worse than the blank control with greater I value(0.3035 versus 0.1768),and P=0.2236.Although these conclusions are close to that drawn by Wu et al.(1986)only based on the index of population trend point estimates,they are supported by an accuracy measurement P-value.