Within the Central Congo Basin, semi-deciduous forests are established on contrasted habitats marked by sandy and clay substrates. We present a case study of plant communities located in a particular zone of our study area where sandy and clay substrates encounter over a steep textural gradient. We then analyze species distribution patterns driven by this edaphic differentiation, with a particular interest on vegetation features in the interface zone. We also describe the spatial structure of the considered edaphic variables, based on the Moran's index. The relationships between soil features and species within forest layers are also exposed. We show that some species are much more related to a type of soil, therefore defining some "edaphic specialists" species while many others can be considered "generalists". As of current scientific interest, we focus on phylogenetic patterns occurring in these plant communities and examine the way all this is linked to the observed edaphic heterogeneity.