边缘效应对棉田害虫和天敌种群的影响

比较了棉田中间棉株与边缘棉株上害虫、天敌的种群动态，分析了边缘效应对棉株-害虫-天敌能量动态的影响。结果表明，棉田边缘棉株上第2代棉铃虫幼虫发生量比其中间棉株高出1．94倍；第3代棉铃虫发生量比棉田中间要低62．12％；第4代棉铃虫比中间棉株高12．5％。棉田边缘棉株上苗蚜发生量比棉田中间要高出1．09倍，伏蚜和秋蚜的数量比棉田中间分别低97．73％和37．70％。棉田边缘棉株上捕食性瓢虫、蝽类、蜘蛛和寄生性天敌的种群数量低于棉田中间的数量，分别为棉田中间的73．81％、35．79％、52．90％和39．11％；棉田边缘棉株上害虫群落多样性高于棉田中间，而天敌群落的多样性低于棉田中间；棉田边缘的光能利用率和生产力比棉田中间的值要高。

Edge effect on the dynamics of pests and natural enemies in cotton agroecosystems

Investigation on the population dynamics of pests and natural enemies on the cotton plants in the middle and edge of cotton agroecosystems showed that the population of the 2nd generation of cotton bollworms ( Heliocopavar armigia ) abstract and seedling aphids ( Aphis gossyppi ) abstract was respectively 1.94 times and 1.09 times higher, but that of the 3rd generation cotton bollworms and summer aphids population was respectively 62.12% and 97.73% lower in the edge than in the middle of cotton agroecosystem. The population of predacious ladybeetles, predacious bugs, spiders and parasites in the edge of cotton agroecosystem was 73.81%, 35.79%, 52.90% and 39.11% of that in the middle of cotton agroecosystem, respectively. The greater diversity of pest community and the less diversity of natural enemies community were found in the edge than in the middle of cotton agroecosystem. The increase of energy utilization efficiency and gross production in the edge of cotton agroecosystems showed the edge effect of cotton agroecosystems.