Regeneration pattern of four threatened tree species in Sudanian savannas of Burkina Faso

摘要

Research was carried out on four threatened tree species across north and south Sudanian phytogeographical zones in Burkina Faso. A quantitative inventory of regeneration populations was completed and sapling dynamics were monitored through surveys of survival and growth in permanent plots. Laboratory and nursery experiments were carried out to test germination and the performance of transplanted seedlings. Results revealed difficulties that saplings faced during their development. In natural stands of Sterculia setigera and Afzelia africana, saplings were rare or irregularly distributed. A greater number of individuals of Bombax costatum were observed, which was the only species with significant density variation between phytogeographical zones (p = 0.021). Size class showed irregular population structures. A high mortality between the first and second year, followed by a stabilization trend, was observed. The initial height of saplings was highly correlated to their survival rate. The rate of new sapling spontaneous recruitment was better in Bombax costatum and Boswellia dalzielii stands, but heir growth was unpredictable in all species. Most saplings grew from lignotubers and root suckers; however, the potential for sexual reproduction was good. Sterculia setigera and Bombax costatum seedlings showed potential for use in silviculture, as evidenced by the fact that both showed high post-transplantation rates of survival and growth.