Population Dynamics of Vitex doniana Sweet and Vitellaria paradoxa C.F.Gaertn. along a Rainfall Gradient in the Dosso Partial Wildlife Reserve, Niger

Abstract

Vegetation cover is one of the most important land-use components within protected areas, which are designated for the conservation and sustainable management of natural resources. As areas of ecological and environmental value, protected areas play an important role in biodiversity conservation by providing habitats for diverse flora and fauna. The Dosso Partial Wildlife Reserve (RPFD) contains biodiversity of considerable socio-economic value, but it is currently threatened by substantial anthropogenic pressure. This study analysed the dendrometric and structural attributes of populations of two important species, Vitex doniana and Vitellaria paradoxa. An inventory was conducted in 200 plots (2,500 m² in agrosystems and 1,000 m² in natural stands). Diameter and height measurements were used to calculate density, basal area and Lorey height. The results showed that the rainfall gradient favoured the Sudanian zone, where V. doniana and V. paradoxa had densities (25.36 and 27.94 trees/ha) and mean diameters (59.26 and 67.51 cm) that were significantly higher than those recorded in the Sahelian zone. However, population structure indicated ageing stands and limited regeneration, suggesting an ecological imbalance associated with anthropogenic pressure. Sustainable management measures,  including farmer-managed natural regeneration (FMNR) and stronger protection of young plants, are required to support regeneration. Effective conservation and sustainable management of these species should also promote cost-effective regeneration while encouraging the active and voluntary participation of rural communities.