Abstract
One way of reducing the rapid decline in biological diversity in agricultural landscapes is to establish wildflower areas. The species richness and abundance of heteropteran bugs in twenty 1- to 4-year-old wildflower areas and winter wheat fields were compared, and the effects of succession in the wildflower areas investigated. Vegetation and environmental parameters (plant species richness, vegetation structure, flower abundance, field size, surrounding landscape) and their effects on bug species were explored. Total species richness and abundance of bugs were significantly lower in wheat fields than in wildflower areas but did not differ in the wildflower areas of different ages. The numbers of zoophagous bugs in the wildflower areas were positively correlated with the age of the wildflower areas. Correspondence analysis showed that the bug species composition in the winter wheat fields was very similar but strongly separated from that in the wildflower areas. The species composition of bugs in the wildflower areas became increasingly dissimilar with advancing successional age. In a partial canonical correspondence analysis, the bug assemblage was significantly associated with the number of perennial plant species, the number of annual plant species and vegetation structure, which accounted for 13.4%, 12.6% and 7.2% of the variance, respectively. As wildflower areas clearly increased heteropteran diversity on arable land and bug species composition changed with increasing successional stage, the establishment of a mosaic of wildflower areas of different age is recommended as it enables the survival of heteropteran bugs with different life history traits.
Highlights
Due to the intensification of agriculture in recent decades and the rapid change in landscape structure, biological diversity in agricultural landscapes has declined (Tscharntke, 1998; Marshall & Moonen, 2002)
This study focuses on bug assemblages (Heteroptera) in winter wheat fields (Triticum aestivum Linnaeus), the most frequently cultivated crop in Switzerland, and in 1to 4-year-old wildflower areas, one type of ecological compensation area
Sixteen wildflower areas of four ages were studied: 1-year-old areas were sown at the beginning of May 2001, 2- to 4-year-old areas were sown in April 1998 to 2000
Summary
Due to the intensification of agriculture in recent decades and the rapid change in landscape structure, biological diversity in agricultural landscapes has declined (Tscharntke, 1998; Marshall & Moonen, 2002). Natural areas adjacent to arable crops are essential for animals since they provide refuges for hibernation and transition zones between habitats on arable land (Wiedemeier & Duelli, 1999). Several methods are being introduced to counteract this rapid decline in biological diversity. In the European Union, set-aside programmes have been established to enhance the animal and plant diversity of farmland and prevent overproduction of crops (Kleijn et al, 2001). Apart from its economic aspects, set-aside is considered an important contribution to nature conservation in agroecosystems (Corbet, 1995). Swiss agricultural policy subsidizes various types of ecological compensation areas where farmers apply specific forms of management (e.g. extensively managed grasslands, hedges, orchards, conservation headlands, wildflower areas)
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