稻田节肢动物群落多样性

DIVERSITY OF ARTHROPOD COMMUNITIES IN PADDY FIELDS

本文运用种类丰富度(S)、均匀性(V)和申农指数(Shannon's index.H')分析稻田节肢动物群落和各亚群落多样性的空间层次差异、季节动态、以及杀虫药剂的作用。稻田节肢动物群落的多样性值较低,H'值一般在3以下,表明群落稳定性差;多样性季节变化较大。在不用农药条件下,8月底以后的H'值较高;水稻群体上部群落的S、和V'值均大于下部的对应值;杀虫药剂的应用虽提高了群落总体的H'和V'值,但对亚群落的分析表明,杀虫药剂促进害虫亚群落的H'和V'值上升,却降低了各天敌亚群落的有关值,从而扩大了害虫和天敌之间稳定性的差距,使两者的同步关系受到损害;杀虫药剂的应用还使各天敌亚群落种类数和个体数明显减少,特别是寄生天敌昆虫种类数、个体数均大幅度下降,使其难以起到控制害虫的应有作用,这又为害虫的再猖獗提供有利条件。通过分析认为,就稻田节肢动物而言,多样性仍然是群落稳定性的一个重要测定指标。

The diversity of arthropod communities in the paddy fields of southern Jiangsu Province was studied by using the indices species richness (S), evenness (V') and Shannon's index (H'), and the difference in spatial stratification, seasonal fluctuation and effect of insecticide application were analyzed. It was found that the arthropod communities of paddy fields consisted of 210 species of which more than 30% belonged to insects injurious to the crop or pests-and 50% pertained to their natural enemies; and the index S was higher in the upper portion of the crop vegetation. In general the indices H' and V were not high; and their values of natural enemies were higher than those of pest insects in the fields without insecticide application after August. The H' values of parasitic insects were the highest and those of predatory insects were the lowest in the upper portion of the vegetation. The H' values of spiders were highest in the lower portion where the H' values of other natural enemies were low. In the fields with insecticide application, indices S became smaller in the upper portion of the vegetation and this occurred obviously for the natural enemies, especially the parasitic insects. The indices H' and V of pest insects became higher. A careful analysis showed that insecticide application had decreased the stability of communities of natural enemies and increased that of pest insects- It is appropriate to evaluate the stability of the arthropod communities in the paddy fields by using diversity as one of the standards.