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Le concept de niche écologique associé à la co-existence des espèces végétales : mise en évidence du rôle de la symbiose mycorhizienne et de sa microflore associée dans la structuration de la strate herbacée en milieu tropical

Abstract : Sahelian ecosystems have been studied to define the role of mycorrhizal symbiosis and mycorrhizospheric flora in plant communities' structuration. The study concerns three main levels of soil - microorganisms - plant systems evolution: (i) the implication of Arbuscular Mycorrhizal Fungi (AMF) like Agent-mediated coexistence processes in an herbaceous weakly disturbed ecosystem; (ii) the study of the impact of AMF like Agent-mediated allelopathic effect of exotic fast growing trees [Gmelina arborea Roxb, Eucalyptus camaldulensis] on endogenous organisms (herbaceous and soil microbial communities) and lastly, (iii) the study of soil invasion by an exotic herbaceous plant [Amaranthus viridis] on soil microbial community (AMF, total bacteria, rhizobia) structure and function, on C, N, P availability in soil and, on the regeneration of five sahelian Acacia species. The results indicate that (i) the presence and abundance of AMF in soils, associated with P availability, could strongly mediate plant species coexistence processes and thus, determine plant species partitioning in terrestrial ecosystems; (ii) AMF's are biological agents which optimize plant growth, restore degraded lands and promote plant biodiversity and finally, (iii) Amaranthus viridis, a very weakly mycotrophic plant species, alters soil chemistry and promotes a reduction in soil mycorrhizal and rhizobial communities after its invasion, thus compromising the survival of Acacia seedlings. Furthermore an increase in soil mycorrhizal propagules could make it possible to mitigate significantly the depressive effect of the invasive plant on the re-establishment of these Acacia species.
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Arsène Alain Sanon. Le concept de niche écologique associé à la co-existence des espèces végétales : mise en évidence du rôle de la symbiose mycorhizienne et de sa microflore associée dans la structuration de la strate herbacée en milieu tropical. Biologie végétale. Université Henri Poincaré - Nancy 1, 2009. Français. ⟨NNT : 2009NAN10004⟩. ⟨tel-01748533⟩

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