Constraints of seedling survival and recruitment under adult tree of a multi-use species Afzelia africana Sm and Pers in Sudanian region of Benin (West Africa)

Abstract

Afzelia africana is a tropical multi-use tree species distributed in West, East, and Central Africa. Understanding factors affecting seedlings is crucial to design an effective conservation and restoration plan for the species. Here, we examined the factors constraining seedling density and survival. We randomly established 203 circular plots of 5-m radius around adult trees in two different management systems (Agro-silvo-pastoral system and Protected Area). Then, we focused on the measurement of seedling density, survival/mortality in 2014 and 2015, and estimated disturbance and micro-environment features. We found that seedling mortality rate was higher in Agro-silvo-pastoral system than in Protected area, demonstrating the prominent role of the protected area for the species conservation. The more intense adult trees are pruned, the lower the seedling density beneath, showing a negative effect of pruning on seedling. Seedling density is relatively higher under large trees, revealing the seedlings recruitment bottleneck due to repeated fire and browsing. Furthermore, our data supported the Janzen–Connell effect, suggesting that seedlings are attacked by predators of their parents. Finally, we conclude that management system, pruning intensity, seedling predation determine the regeneration status of A. africana in Sudanian zone. Artificial regeneration program is necessary, as well as shelters and thorny protectors should be established around seedlings under reproductive trees. Firebreaks are also recommended to protect the seedlings and Afzelia stands.