棉田及其邻作田地表节肢动物天敌的季节动态

运用陷阱法对小麦/玉米-棉花、苜蓿-棉花、棉花-棉花3种交错带的棉田及其邻作田共6种类型田块的地表节肢动物群落进行了抽样调查,研究地表天敌物种组成、数量及多样性的季节动态.结果表明：与不同作物邻作的棉田中,每个陷阱全年收集到的物种数差异显著,以与小麦/玉米邻作的棉田物种最丰富,为13.3种,与苜蓿邻作和棉棉邻作棉田的物种数分别为10.4和11.7种;每个陷阱全年收集的天敌个体数差异亦显著,以棉棉邻作棉田的最少,平均50.1头,与小麦/玉米和苜蓿邻作棉田分别为75.1和77.6头.3种邻作方式下,棉田地表天敌数量在4月中旬至8月中下旬均呈现明显的季节性波动,8月底至9月底则呈波动上升趋势.棉田及其邻作苜蓿田或小麦/玉米田天敌数量的季节性波动趋势基本一致,棉田与其邻作田之间地表节肢动物天敌存在迁移.综合6类型田块地表节肢天敌功能团的数量动态,蜘蛛类在各类型田块中长期是优势天敌功能团,尤以6、7、8月数量更大;隐翅甲是次优势天敌功能团.对6类型田块地表节肢天敌的群落特征分析表明,天敌功能团多样性指数H＇与物种多样性指数H＇显著相关,可用天敌功能团多样性指数H＇代替物种多样性指数H＇研究天敌群落特征;节肢动物天敌功能团优势度指数D、均匀度指数J与物种优势度指数和均匀度指数并不完全显著相关.对地表节肢动物天敌群落特征的系统聚类分析结果表明,与小麦/玉米邻作、棉棉邻作的两块棉田地表节肢动物天敌群落较为相似;与苜蓿邻作的棉田较为特殊,其多样性指数H＇最低（1.425）,优势度指数D最高（0.473）,均匀度指数J最低（0.731）.

Seasonal Dynamics of Ground-dwelling Natural Enemies in Cotton Fields and Their Adjacent Crop Fields

A pitfall trap survey was made in cotton fields and their adjacent crop fields from April to September 2004 to investigate the composition and seasonal dynamics of the ground-dwelling arthropod natural enemies.There were three kinds of ecotones involved,i.e.wheat/corn-cotton,alfalfa-cotton,and cottoncotton ecotones.It showed that:(1) There were significant differences among averaged number of species and averaged number of individuals per pitfall trap during the whole survey period.There were 13.3 species in average in cotton field adjacent to wheat/corn field,which was more abundant than that in cotton field adjacent to alfalfa(10.4 species) or cotton field(11.7 species).There were 50.1 individuals captured per pitfall trap in cotton field adjacent to cotton field,which was less than that in cotton field adjacent to wheat/corn(75.1 individuals) or alfalfa field(77.6 individuals).(2) The numbers of ground-dwelling arthropod natural enemies fluctuated during middle April to middle to late August,and increased from late August to late September,in all the six fields of the three ecotones.Seasonal dynamics in cotton field and its adjacent wheat/corn or alfalfa field were similar,indicating there was free migration of ground-dwelling arthropod natural enemies between the adjacent fields.(3) Spiders were the most abundant ground-dwelling natural enemy group,especially in June to August,followed by the functional group of Staphylinidae,in all the six fields of the three ecotones.(4) There was significant correlation between Shannon-Weiner diversity index H' of functional groups of natural enemy and that of natural enemy species.Whereas there were not always such correlations in Simpson dominance index D and Pilou evenness index J of functional group level and species level.(5) Cluster analysis showed that the community structure of ground-dwelling natural enemies cotton field adjacent to wheat/corn field was similar to that adjacent to cotton field.But cotton field adjacent to alfalfa field was different from them,with lower Shannon-Weiner diversity index H'(H'=1.425),higher Simpson dominance index D(D=0.473),and lower Pilou evenness index J(J=0.731)