This study defined ecological groups of tree species based on species life-history traits within the savannah-forest mosaic of the Lopé National Park, Gabon in order to understand the connection between different types of forest within this study area. Three life-history traits were the most efficient at discriminating species groups within the floristic assemblage, namely, functional guild, dispersal type and phytogeographic type. The combination of dispersal potential and functional guild enabled us to rank the 169 studied species on gradient of forest types. A species classification into functional groups based on similar biological traits was proposed for the purpose of conservation management and development of new conservation areas. This first classification distinguished between canopy species and understorey species, thus suggesting the existence of two separate dynamics for tree species and three functional groups. These results are useful to set conservation priorities to achieve management plans.