The research result is following : the annual species richness index of studied forest plant community averaged 64 . 688 , the species diversity index was 2 . 982 . the proportion of every functional group of forest plant community is : herbaceous layer ( average is 68 . 89 % ) > tall tree layer ( average is 15 . 266 % ) > shrub layer . ( average is 15 . 845 % ) the proportion of every functional group in forest insect communities is remarkably different , and the order of the proportion is herbivorous insect group ( average 0 . 729 ) > predatory natural enemy insect group ( average 0 . 136 ) > parasitical insect group ( average 0 . 135 ) . with seasonal change , the proportion of herbivorous and predatory insect group decreased obviously , while that of parasitical insect group increased on average by 147 % 研究结果如下：森林植物群落种的全年物种丰富度指数平均为64 . 688种，多样性指数为2 . 982森林植物群落内各功能类群物种所占比重依次为：草本层(平均为68 . 89 ) >乔木层(平均为15 . 266 )灌木层(平均为15 . 845 ) 。森林昆虫群落中，全年各功能类群所占比重以植食性昆虫类群为最大，平均占0 . 729 ；捕食性昆虫类群次之，平均占0 . 136 ；寄生性天敌类群为最小，平均为0 . 135 。
The results showed that the temporal dynamics of predatory natural enemy community in cotton fields could be classified into seven types and the change of the community could he divided into three major stages of formation and development period ( in the vegetative growth stage of cotton ) , great prosperity period ( in the vegetative and reproductive growth stage of cotton ) and decline period ( in the reproductive growth stage of cotton ) 结果表明，棉田捕食性天敌群落的时序动态可以分为7种类型；演变可以分为形成和发展阶段（棉花营养生长期） 、鼎盛阶段（棉花营养生长和生殖生长并进期） 、衰退阶段（棉花生殖生长期） 3个主要阶段。
The application of nitrogen fertilizer affected positively and negatively the predation abilities both in laboratories and fields by its indirect and direct roles in the trophic relationship among host plants , herbivores and predators , the improvement of nutrients and the modification of allelochemicals in host plants 摘要施用氮肥后可以直接或间接地通过对植物害虫天敌三者之间关系的干预、改变寄主植物内的营养成分和次生化学物质的含量等从正反两个方面影响捕食性天敌的捕食能力。
