Highlights• Non-destructive sampling approach applied to derive ground truth observations and generate robust basic wood densities.• Species-specific and generic allometric equations.• Specific equations have better predictive capabilities than generic models. AbstractThe quantification of the contribution of tropical forests to global carbon stocks and climate change mitigation requires availability of data and tools such as allometric equations. This study made available volume and biomass models for eighteen tree species in a semi-deciduous tropical forest in West Africa. Generic models were also developed for the forest ecosystem, and basic wood density determined for the tree species. Non-destructive sampling approach was carried out on five hundred and one sample trees to analyse stem volume and biomass. From the modelling of volume and biomass as functions of diameter at breast height (Dbh) and stem height, logarithmic models had better predictive capabilities. The model validation showed that in absence of data on height, models using Dbh only as variable was an alternative. The comparison of basic wood densities to data published in literature enabled to conclude that the non-destructive sampling was a good approach to determining reliable basic wood density. The comparative analysis of species-specific models in this study with selected generic models for tropical forests indicated low probability to identify effective generic models with good predictive ability for biomass. Given tree species richness of tropical forests, the study demonstrated the hypothesis that species-specific models are preferred to generic models, and concluded that further research should be oriented towards development of specific models to cover the full range of dominant tree species of African forests.

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RESUMELes forêts sacrées connaissent une dégradation proportionnelle à l'augmentation des populations riveraines et du développement de leurs activités socioéconomiques. La présente étude avait pour objectif d'étudier la structure forestière de la forêt sacrée de Nassou, et d'évaluer les possibles effets anthropiques sur les caractéristiques dendrométriques et écologiques de 4 essences fruitières ligneuses. A cet effet, un inventaire forestier de 60 placettes carrées de 900 m 2 réparties suivant un échantillonnage stratifié aléatoire dans les trois formations végétales de ladite forêt a été réalisé. De plus, les niveaux de pressions anthropiques ont été notés en suivant une grille d'évaluation. Certains paramètres structuraux ont été calculés et analysés. Les paramètres dendrométriques et écologiques obtenues variaient globalement en fonction des formations végétales pour les quatre espèces. En général, les plus fortes valeurs sont obtenues en forêt dense sèche par comparaison aux autres formations. Les distributions en diamètre au sein de la forêt présentent globalement des allures normales mais la structure de chaque peuplement d'espèce présente des allures diverses. De plus, une corrélation négative et non significative de manière globale a été observée entre les niveaux de pression et les espèces cibles, indiquant une pression anthropique dirigée vers d'autres espèces. Il faudra donc continuer les investigations pour identifier les espèces les plus vulnérables au choix sélectif des populations et leur effet sur la viabilité des peuplements. ABSTRACTSacred forests are deteriorating in proportion to the increase in riparian populations and the development of their socio-economic activities. This study assessed forest structure of sacred grove Forest of Nassou and possible human effect on biometric and ecological parameters of four fruit plant species. To that P. O. AGBANI et al. / Int. J. Biol. Chem. Sci. 12(6): 2519-2534, 2018 2520 end, a forest inventory in 60 plots of 900 m 2 were established using a stratified random across the three vegetation types of the forest. In addition, pressure scale were used to appreciate pressure threshold on target species. Some structural parameter were calculated and statistically tested. Main results shown a variation of biometric and ecological following vegetation types with the highest values obtained in dry forest. Diameter structure were globally followed normal distribution for the whole forest, whereas per species and across vegetation the distribution varies a lot. Moreover, negative correlation between human pressure and diameter structure of the target species. This indicate a pressure on others species of the forest leading to further studies to identify vulnerable species to selective choice by local population and consequences on their viability.

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