Insectes pollinisateurs dans les paysages agricoles : approche pluri-échelle du rôle des habitats semi-naturels, des pratiques agricoles et des cultures entomophiles

Abstract : agricultural landscapes where oilseed rape, a mass flowering crop, is produced. It is original as it considers agricultural practices and not only the amount of semi-natural habitats, to assess the impacts of agricultural intensification. In 14 European sites, the bees are adversely affected by agricultural intensification (measured by the amount of pesticides and nitrogen fertilizers and by the livestock density) and positively affected by the amount of semi-natural habitats. At the landscape scale, we find that : (1) bees and hoverflies are more abundant on oilseed rape (OSR) field margins than on other types of field margins, showing the attractiveness of OSR ; (2) the role of semi-natural habitats can differ according to the landscape structure : in the “bocage”, hedgerows and grasslands have a positif impact whereas in the openfield, bees seem to rely on lanes (providing nesting sites for ground-nesting bees) and field margins (providing floral resources) ; (3) in the “bocage”, accounting for the recent past use (5 years) of crop fields shows that temporary grasslands in crop rotations have a positive impact on solitary bee species richness. An analysis of the spatial distribution of pollinator insects in OSR fields indicates that (1) in the “bocage”, all insects use both the edges and the interior of fields. Bumblebees, whose flight capabilities are most important, use preferentially the interior of fields, where the amount of resources is maximum, (2) in the openfield, where the amount of OSR is higher, we observe a "dilution" effect, which makes more difficult the understanding of insect behavior. By improving knowledge about spatial distribution of pollinator insects, our study permits to better estimate pollen flow, and therefore the potential impacts of transgenic crops.
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Violette Le Féon. Insectes pollinisateurs dans les paysages agricoles : approche pluri-échelle du rôle des habitats semi-naturels, des pratiques agricoles et des cultures entomophiles. Ecologie, Environnement. Université Rennes 1, 2010. Français. ⟨tel-00566660⟩

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