Facteurs déterminant la productivité et la séquestration de carbone de Acacia auriculiformis A. Cunningham ex Benth. au Bénin

Acacia auriculiformis is the third most frequently planted fast-growing tree species in Benin. Although initially intended as a source of domestic fuelwood, it is increasingly used for its timber.   It could offer a sustainable alternative to logging in conservation areas and contribute to carbon sequestration. The aim of this study was to assess the factors that influence timber production and carbon sequestration in plantations of A. auriculiformis in Benin. The study was conducted in twelve plantations (young: 4-7 years, average-aged: 9-11 years, and mature: 15-29 years), distributed over ferruginous, vertisolic, ferralitic and sandy soils in the Guinean climatic zone. The parameters measured were average radial growth, diameter at 1.30 m height, bole height, total height, proportion of heartwood and proportion of blemish-free wood. Productivity was higher on ferruginous and ferralitic soils, with an average growth rate of 2.4 cm/year up to 6 years of age. A significant difference in growth rates appeared between young and old trees. The proportion of blemish-free wood was highest on ferruginous soils. Optimum carbon sequestration was at 20 years of age. The optimum age for timber production in Benin was about 15 years for trees growing on ferruginous soils. Soil type is the most determining factor for the production of A. auriculiformis timber. Ferruginous soils account for about two thirds of all soil types found in Benin, which holds out good prospects for an A. auriculiformis timber sector. However, technical characterisation of A. auriculiformis wood grown on the different soil types in Benin is required to assess its physical and mechanical properties as a timber species.