Samu Ferenc
Plant Protection Institute, Hungarian Academy of Sciences, PO Box 102 Budapest, H-1525 Hungary.
Pest Manag Sci. 2003 Apr;59(4):437-42. doi: 10.1002/ps.635.
The study investigated the effect of strip management in alfalfa on the abundance and diversity of spiders. In strip management, narrow strips were left unmown in the crop, which were then shifted at next mowing. In an experimental field, out of the six 50 x 50-m blocks, three received strip management and three were managed traditionally (ie the whole block was mown). Our main hypothesis was that unmown strips will contain a more diverse and abundant spider assemblage, which will increase spider numbers in the mown parts of the crop. Over the 3 years of the study, unmown strips contained a spider assemblage of more than 50% higher abundance than in control alfalfa. Species diversity was also greater in the strips, and the presence of specific indicator species could be shown. We found that five dominant species comprised over 75% of spiders in the strips, and they were the same species as those that are dominant in alfalfa, where they represent 85% of all spiders. In contrast, a neighbouring meadow, which was a control in the study, also had high diversity, but different dominant species. The main result of the experiment was negative in that elevated abundance of spiders in unmown strips did not raise spider numbers in the mown strips of alfalfa, where abundance was only marginally higher than in the control alfalfa. We can speculate that better ecological conditions in unmown strips attract and conserve spiders from neighbouring areas and from the crop at mowing. We suggest that if diversification is more interspersed within the crop, we have a higher chance of increasing the number of natural enemies and bringing them closer to pests, so that they can interact more intensively.
该研究调查了苜蓿条带管理对蜘蛛数量和多样性的影响。在条带管理中，作物中留出狭窄条带不进行刈割，然后在下一次刈割时移动这些条带。在一个试验田中，六个50×50米的地块中，三个采用条带管理，三个采用传统管理方式（即整个地块进行刈割）。我们的主要假设是，未刈割的条带将包含更多样化和丰富的蜘蛛群落，这将增加作物刈割部分的蜘蛛数量。在研究的3年中，未刈割条带中的蜘蛛群落数量比对照苜蓿高出50%以上。条带中的物种多样性也更高，并且可以显示特定指示物种的存在。我们发现，五个优势物种占条带中蜘蛛的75%以上，它们与苜蓿中的优势物种相同，在苜蓿中它们占所有蜘蛛的85%。相比之下，作为研究对照的邻近草地也有很高的多样性，但优势物种不同。该实验的主要结果是否定的，即未刈割条带中蜘蛛数量的增加并没有提高苜蓿刈割条带中的蜘蛛数量，其数量仅略高于对照苜蓿。我们可以推测，未刈割条带中更好的生态条件吸引并保护了来自邻近区域和刈割时作物中的蜘蛛。我们建议，如果在作物中更多地穿插多样化种植，我们就有更高的机会增加天敌数量并使它们更接近害虫，从而使它们能够更密集地相互作用。
