苜蓿田地表蜘蛛边缘效应及苜蓿刈割后的溢出效应

为明确不同类型苜蓿田地表蜘蛛边缘效应及苜蓿刈割后地表蜘蛛溢出效应在小麦田与玉米田之间的差异,于2015年5—7月采用陷阱法调查了银川平原不同类型苜蓿田及邻作玉米田和小麦田中的蜘蛛种类及个体数,比较苜蓿田边缘区及中心区蜘蛛群落多样性指数和个体数量的时空变化以及苜蓿田刈割前后相邻农田边界处蜘蛛群落的时空动态变化。结果表明,在整个取样季节共采集蜘蛛标本7 894头,隶属10科22种,其中苜蓿单作田中蜘蛛个体数量最多,共2 550头;苜蓿-小麦邻作田中蜘蛛群落物种丰富度最高,共17种。星豹蛛Pardosa astrigera和甘肃平腹蛛Gnaphosa kansuensis为优势种,分别占个体总数的38.08%和27.17%。非量度多维尺度(non-metric multidimensional scaling,NMDS)分析显示苜蓿单作田同苜蓿邻(间)作田蜘蛛群落的结构组成差异较大,且在苜蓿田边界处和内部存在差异。不同类型苜蓿田边界处和内部蜘蛛群落的多样性指数、优势度指数、个体数量和丰富度在取样的不同时期存在显著差异。刈割可以促进苜蓿田中地表蜘蛛向邻作农田中迁移,苜蓿刈割后与苜蓿田邻作的小麦田和玉米田中蜘蛛个体数量和多样性指数均存在溢出效应,溢出效应的范围为距界面处0~20 m。小麦田中蜘蛛个体数量密度和多样性指数总体高于玉米田,溢出效应的持续时间为1~7 d,高于玉米田。

Edge effect of ground-dwelling spiders and spillover effect after alfalfa mowing in alfalfa fields of Yinchuan area

In order to investigate the difference in the edge effect of ground-dwelling spiders among different alfalfa fields and spillover effect between wheat and corn fields after mowing in alfalfa fields, the species and individual numbers of spiders were surveyed by using the pitfall traps in alfalfa fields under different cropping patterns in Yinchuan Plain from May to July, 2015, and the diversity index and individual number of spiders in the margin of alfalfa fields, the spatial and temporal distribution changes of spiders in wheat and corn fields adjacent to alfalfa fields before and after the mowing of alfalfa fields were compared. The results showed that, during the field survey, a total of 7 894 spiders were collected, which belonged to 22 species of ten families. Pardosa astrigera accounted for 38.08% of the total, Gnaphosa kansuensis 27.17%, which were the dominant species. The results of non-metric multidimensional scaling (NMDS) showed that the individual number of spiders was highest in alfalfa fields, and the species richness of spider community was highest in alfalfa-wheat fields under the conditions of the same individual number of spiders. The community composition in alfalfa fields was different from in other fields, including field margins. There were significant differences among diversity index, dominance index, individual number and species richness in alfalfa fields under different cropping patterns during different periods in the whole survey season. Mowing can promote the migration of grounddwelling spiders from alfalfa fields to adjacent fields. The spillover effect of diversity and individual number of spiders existed in the wheat and corn fields adjacent to alfalfa fields after mowing. The range of spillover effect is 0-20 m from the interface. The spillover effect lasts from one to seven days in wheat fields, longer than in corn fields. The total diversity and density of spiders was higher in wheat fields than in corn fields.