Biodiversity and Structure of Woody Plants of Sahelian Rangelands of Baban Rafi, Niger

The present study investigates the importance of harvesting regimes and natural disturbances on the diversity, the population structure and the regeneration trends of the woody plant species of Sahelian rangelands and their implication for sustainable browsing management. Woody plants data was collected in 42 plots established in the interval of 500 m, along transects distant of 500 m, in the direction South-west and North-east of the study area. In each plot, height and diameter at breast height of each individual mature tree and shrub (diameter < 4 cm), and the number of seedlings (diameter > 4 cm) were recorded. A total number of 21 plants species were recorded, with low values of the Shannon-Weaver (H’) index and the evenness of Piélou (E) indicating very low diversity of rangelands. Analysis of size classes distribution of diameters and heights of the whole vegetation and the three dominants species revealed high density of juveniles, relating to stable populations. The juvenile plants represented more than 80 of the vegetation with diameters and heights respectively lower than 6 cm and 2.5 m, indicating shrubby vegetation. Combretum micranthum, Guiera senegalensis and Combretum nigricans which have the highest values of IVI, have also the greatest rates of seedling and vegetative propagation densities. Stable populations with strong capacity of regeneration under harsh area and high human pression such as logging and grazing can be related ecological success. Management practices that promote plantations or managing natural regeneration of such species can facilitate fast secondary succession towards desirable condition.