Introduction: In Niger, the degradation of ecosystems leads to a loss of biodiversity and an increase in the adverse effects of climate change, especially in the ecosystems contracted from the plateaux of the Niger W biosphere reserve. Objective: The objective of this study is to characterize the spatial variability of the flora according to the north-south rainfall gradient of the reserve. Methodology: Phytosociological surveys, an ascending hierarchical classification and a canonical analysis of correspondences between plant groups and environmental factors. Results-Discussion: The 126 inventoried species have 88 dicotyledons, 28 woody species, and 98 herbaceous species. The most common families are: Poaceae (21.42%), Fabaceae (12.69%), Rubiaceae (7.14%) and Convolvulaceae (6.34%). The biological spectrum is dominated by therophytes then microphanerophytes. The world chorology is marked by African species followed by palaeotropics or pantropicales, and at the African level, Sudano-Zambezian species are the most frequent. The presence of intermediate species (GC-SZ and GC-SZ-Sah-S) is noted. From north to south, 3 groups of plants were highlighted: the group with Sida cordifolia and Guiera senegalensis whose phytodiversity is reduced; Group II consisting of the subgrouping with Combretum nigricans and European Scientific Journal January 2018 edition Vol.14, No.3 ISSN: 1857 -7881 (Print) e -ISSN 1857 157 Microchloa indica and the subgrouping with Combretum micranthum and Gardenia sokotensis floristically rich, with however a regeneration dominated by Guiera senegalensis; grouping with Loudetia togoensis and Acacia macrostachya, in good state of conservation. Conclusion: The study made it possible to characterize floristically the various landscapes along the rainfall and anthropic gradient.Thus, in view of the structures of the stands observed, the distribution of floristic diversity increases according to a gradient of decreasing aridity from the periphery to the internal part of the reserve. From the north to the south there is a degraded part, a part gradually invaded by Guiera senegalensis and another well preserved. This work, which provides an overview of the state of conservation of the floristic diversity of the Niger W Biosphere Reserve, allows taking appropriate measures to safeguard our plant resources.
Keywords: Floristic diversity, plateaus, Biosphere Reserve, Niger
RésuméIntroduction : Au Niger, la dégradation des écosystèmes induit une perte de la biodiversité et une accentuation des effets néfastes du changement climatique surtout au niveau des écosystèmes contractés des plateaux de la réserve de biosphère du W du Niger. Objectif : L'objectif de cette étude est de caractériser la variabilité spatiale de la flore suivant le gradient pluviométrique Nord-sud de la réserve. Méthodologie : Des relevés phytosociologiques, une classification hiérarchique ascendante et une analyse canonique des correspondances entre groupements végétaux et facteurs du milieu. Résultats-discussion : Les 126 espèce...