Distribution and structural characterization of Balanites aegyptiaca (L.) Delile and Ricinodendron heudelotii (Bail.) Pierre among phytodistricts and land use types in Benin (West Africa).

Balanites aegyptiaca (L.) Delile and Ricinodendron heudelotii (Bail.) Pierre are multipurpose wild oil plants (WOP) with high socio-economic and ethnoecological importance. Both WOPs remained neglected and underutilized at the national or regional level. In this study, their geographic distribution and structural characteristics were assessed in Benin. Inventory surveys were carried out along 170 linear transects for both species and 488 and 64 circular plots for B. aegyptiaca and R. heudelotii, respectively. The dendrometric, density, and diversity parameters were collected to characterize the stand structure of the species using linear and generalized linear models, Pearson pairwise correlation, Weibull distribution and the Importance Value Index. Adults of B. aegyptiaca were exclusively found in the semi-arid zone of Benin. The tree-density increased northward with high value in East Mekrou-Pendjari phytodistrict. The highest value for recruitment was obtained in the Atacora chain and West Mekrou-Pendjari phytodistricts in gallery forest and wooded savannah. As for R. heudelotii, adults were found in sub-humid and humid zones with an aggregated spatial distribution. The tree-density of R. heudelotii was not significantly affected by phytodistricts and land use types. The recruitment rate was high in South Borgou and West Plateau phytodistricts in the forest. The dendrometric characteristics were high in North Borgou and East Mekrou-Pendjari phytodistricts in farm/parkland for B. aegyptiaca and South Borgou and Pobe phytodistricts in gallery forest and forest for R. heudelotii. The demographic pattern of these species revealed a low potential for regeneration and recruitment of individuals from low to high diameter classes as a result of anthropogenic pressures. These results demonstrate the need to intensify the domestication or assisted natural regeneration of these species in degraded areas to promote and ensure their sustainable exploitation. [ABSTRACT FROM AUTHOR]