Résumé : The study was carried out in the Pahou forest reserve in southern Benin as a contribution to sustainable management of this forest. Plant communities’ assessment was made usi ng t he synusi al approach to phytosociology. Soils were characterized according to their pedological profiles and physico-chemical properties. Silvicultural plantations parameters were studied using temporary sample plots of 300 m² each in representative sites of the forest. This study allowed to identify and to describe five phytocoenoses (plant communities). Two hundred and forty-seven (247) species were found in the undergrowth of Acacia auriculiformis plantations in Pahou forest belonging to two hundred and nine (209) genera and seventy-one (71) families. The mean annual increment in diameter and height of the plantations ranged f rom 1. 2 to 3. 1 cm/year and 1. 4 t o 4.2 m/year, respectively, indicating that acacias plantings of Pahou forest are among t he most product i ve i n West Africa. The relationships between ecological factors and productivity of the different plant communities enabled to identif y and map four forest types among which the most productive was represented by the Barteria nigritana – Rauvolfia vomitoria plant community, while the least productive is the biotope supporting Axonopus compressus – Scleria depressa plant community. Recommendations are given on the use of these phytosociological indicators as tools for sustainable forestry management.