Establishment and indigenous management of Vitellaria paradoxa (Gaerth. F).parkland systems in southwestern part of Burkina Faso: case study of Torokoro village

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Traditional agro forestry parkland systems, where farmers grow annual crops in fields with scattered trees are among the most widespread agro forestry systems in Sub-Saharan Africa. These systems have the potential of being biologically more productive and stable, and socially more acceptable than agriculture and forestry mono-cultures in developing areas. Despite the importance of parklands, some authors agree that they have been degrading in the last decades. The aim of the current study was to characterize traditional agro forestry parkland systems at the village (Torokoro in Burkina Faso) scale in order to have a better understanding of establishment processes, dynamics and traditional management practices that can help develop strategies to sustain the productivity of these systems. Methods included first, a diachronic analysis assessing the spatial patterns of agroforestry parklands. Then comparative inventories were carried out to evaluate the influence of agricultural practices on parkland attributes. Finally, farmers were interviewed on tree management practices and uses of parkland resources. The results showed a recent strong expansion of cultivated land in Torokoro. In years 1956, 1983 and 1998, agro forestry parklands accounted for 2.5%, 5% and 27% respectively of the total land of Torokoro’s village and this recent increase is attributed to a recent flow of migration into the village. Tree species richness, density, diversity and equitability indices were found to be low in farmed parklands and high in natural vegetation areas. Tree population structure in fallow land gave a good picture of woody species regeneration. Parklands were strongly dominated by Vitellaria paradoxa and few useful species such as Tamarindus indica, Parkia biglobosa, Diospyros mespilifformis and Anacardium occidentale. The average tree measured 22.02 cm of diameter at breast height, 7.20 m of height and 4.10 m of crown diameter. The average Vitellaria tree, the dominant species was slightly bigger in size with 22.36 cm, 7.52 m and 4.32 m in diameter, height and crown size respectively. Diameter and crown size showed significant positive relationships with field age with an average growth of about 0.62 cm! year and 17, 69-cm/year for each variable respectively. On the contrary, tree height did not show a significant relationship with field age. Tree species-specific richness and Vitellaria tree density are significantly different in native and migrant smallholder fields. Therefore, Tree density (all species combined) diversity index and equitability index were not significantly different between the two groups of smallholders. Animal traction significantly affected parkland tree species-specific richness and diversity; whereas, no significant difference was found for tree density and equitability. Cotton cultivation showed significant effect on tree species specific richness and diversity compared to yam and cereal crop cultivation, but had no significant effect on tree densities and equitability. Tree species-specific richness and diversity decrease significantly with cultivation duration but no significant difference was found with regard to tree densities and equitability. Parkland tree management practices include tree planting, felling and pruning. Useful fruit production is the main criteria for tree species selection during field clearing but among individuals of a given useful tree species, phenotypic selection is used. Tree planting in fields is increasingly gaining an importance in Torokoro and it involves one exotic species, Anacardium occidentale. Tree tenure is closely link to land tenure with the exception of the exotic species.
A thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfilment of the requirements for the Master of Science degree in Agroforestry, 2004