Regeneration of Vitellaria paradoxa and Parkia biglobosa in a parkland in Southern Burkina Faso

摘要

Because of intensification of agriculture and the change towards a dryer climate, concerns have been raised about regeneration of trees in agroforestry parklands. We investigated the regeneration of Vitellaria paradoxa, Parkia biglobosa and other species in a parkland in Nobéré, Burkina Faso. Studies were carried out in fields and fallows in two zones differing in cultivation intensity. Inventories of adult trees and regeneration plots were used to assess regeneration, and permanent plots under trees were established to monitor regeneration during 2½ years. For V. paradoxa, densities of mature trees were high. There were many trees in small diameter classes, especially in fallows. Seedling densities were higher under tree crowns than outside and higher in the less intensively cultivated zone. The number of seedlings was high in the rainy season, but decreased in the dry season. Densities of P. biglobosa were lower (5 trees ha−1) and not significantly different between fields and fallows. P. biglobosa trees were almost exclusively old trees. The few seedlings recorded disappeared after one to a few months. Densities of other species were low in fields but higher in fallows. Despite an abundant regeneration of other species only few trees were found in large diameter classes because most species are considered as weeds by the farmers and are removed during cultivation. Lack of regeneration of P. biglobosa seems to be due to intensive seed harvest, leaving few seeds to germinate, and browsing animals destroying individuals that germinate. Institutional arrangements in the village disfavour regeneration of P. biglobosa as the trees belong to land chiefs. In order for P. biglobosa to regenerate it will be necessary to introduce direct sowing and/or plantations of the species, as well as to find a solution to the conflicting interests.