Effets de la gestion des bandes enherbées sur le contrôle biologique des ravageurs de cultures : rôle de la diversité fonctionnelle des carabes (Coleoptera : Carabidae) et de la structure végétale

Abstract : In the agricultural landscapes, non cropped habitats are an important source for the beneficial entomofauna of crops. It is therefore important to adapt the management of these habitats to best benefit of the services provided by the diversity of this beneficial entomfauna. The objective of this thesis is to understand how field margin management could improve the biological control service delivered by ground beetles. First, we examined by which mechanisms, changes in the functional diversity of ground beetles increases their capacity of pest suppression. Thus, efficiency of predation by ground beetle assemblages, which have different levels of body size diversity, on a prey population was compared in the laboratory. Also, through an experiment installed in cereal fields, we studied the effects of five field margin management on the vegetation structure of these non cropped habitats, and therefore on the structure of ground beetle communities. Our results revealed the absence of resource partitioning among the different-sized ground beetles. The amount and size of prey consumed increased with increasing ground beetle body size. Prey suppression was, therefore, strongly strengthened by the presence of large ground beetles in the assemblages. These results suggest that increasing ground beetles size diversity increases their predation efficiency through the sampling effect. We have showed a functional redundancy among species of ground beetles. This redundancy could reduce the spatial and temporal variability in pest suppression by ground beetles. Our study showed the importance of the field margins as a habitat for many ground beetle species that are important for biological control. Management influenced ground beetles only in the field margin. Plants functional diversity within these field margins has been identified as the main factor promoting the species richness of ground beetles. However, activity-density of ground beetles was promoted by less heterogeneous vegetation and high percentage of bare ground. The responses to the vegetation structure vary between ground beetles with different body sizes. This diversity in ground beetles responses to the vegetation structure appears to be also related to variation in other life history traits (i.e. diet). The knowledge and results produced as part of this thesis will be used in the development of indicators measuring the impact of management on biological control delivered by ground beetles
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Abdelhak Rouabah. Effets de la gestion des bandes enherbées sur le contrôle biologique des ravageurs de cultures : rôle de la diversité fonctionnelle des carabes (Coleoptera : Carabidae) et de la structure végétale. Sciences agricoles. Université de Lorraine, 2015. Français. ⟨NNT : 2015LORR0048⟩. ⟨tel-01751605⟩

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