Introduction. En raison de la diminution des ressources en bois d’œuvre tropicaux, il convient d'améliorer les connaissances sur les espèces ligneuses en vue de développer des politiques d'exploitation réellement durables. Reconnu pour la grande qualité de son bois, Cylicodiscus gabunensis Harms (Fabaceae-Caesalpinioideae) est une essence à haute valeur socio-économique. Cet article dresse la synthèse bibliographique des connaissances relatives à cette espèce en vue de mettre en avant l’ensemble des aspects méritant des investigations scientifiques approfondies. Littérature. Commercialisée sous le nom d’okan, C. gabunensis est une espèce ligneuse non grégaire vivant dans les forêts denses humides tropicales sempervirentes et semi-décidues. Arbre fétiche pour certains peuples autochtones, C. gabunensis est utilisé par les communautés rurales pour de multiples usages. C’est une espèce à phénologie régulière avec une dispersion anémochore des graines. Les populations d’arbres affichent un déficit de régénération en forêt dense humide sempervirente, ce qui compromettrait l’exploitation de l’espèce à long terme. Ce risque est accru par le manque évident d’informations écologiques et sylvicoles permettant une gestion durable. Conclusions. Cette revue bibliographique résume l’ensemble des informations disponibles sur C. gabunensis principalement en botanique, anatomie du bois, écologie et ethnobotanique. Elle renseigne sur l’état actuel des connaissances au regard des rythmes d’exploitation et de l’état des populations de l’espèce. Des informations complémentaires sont nécessaires pour (i) statuer sur la conservation des populations de l’espèce et (ii) proposer des stratégies de gestion adaptées.
Many commercial species are light-demanding and regenerate with difficulty in natural forest, which compromises the sustainability of logging. Okan, Cylicodiscus gabunensis Harms is one of the most exploited species in Central Africa and its regeneration is deficient in evergreen forest. In forest concessions, the enrichment of logging gaps with commercial species has already been tested but only for a few species. Mixed results have been obtained because the ability of seedlings to emerge from competing vegetation depends on the species, the environment and the silvicultural techniques adopted. This paper aims to determine the performance of C. gabunensis when planted in felling gaps. The impact of fertilization and biochar application on the performance of the seedlings was examined, as well as the role of predation played by large mammals. In 30 gaps, whose light levels were quantified, we planted nine seedlings and applied three treatments (fertilizer and biochar, fertilizer, control). The performance of the seedlings (survival, mammal damage and growth) was followed for 18 months. In another 30 gaps, the preferential consumption of C. gabunensis seedlings was quantified using camera traps. Seedlings had moderate and highly variable growth (1.84 cm to 2.50 cm in height and 0.201 mm to 0.267 mm in basal diameter per month, all treatments combined). Gap size and initial fertilization significantly boosted growth in diameter and survival rate. Elephants preferentially sought out C. gabunensis seedlings and after 18 months they destroyed 35% of the plants. Enrichment of logging gaps with C. gabunensis should therefore be limited to the largest gaps in forests with low elephant densities. Initial fertilization is recommended but not allowed under the sustainable management certification guidelines. We suggest that these standards should be adapted to maximize the chances of success.
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