Resumo. This study aimed to test the occurrence of the successional process in a mature forest using the distribution of the trees in phases of development. The study forest remnant, a 11-ha old-growth seasonal forest, is located in the margins of Rio Capivari in Lavras, Minas Gerais state, Brazil. The data collection was carried out in 1998, 2003, 2009 and 2014, when we measured and identified to species level all trees that have reached the pre-established inclusion criteria (circumference at 1.3 above the ground level - CBH ≥15,7 cm). From these data, we obtained the species richness for each of the four development phases established on the basis of circumference criteria (Juvenile, Pre-established, Established and Emerging), as well as information on the species turnover, structure, floristic composition and the sharing between these phases The results indicated that there are no significant temporal differences in the structure and the distribution of species richness in development phases. Besides, we found a subtle movement of species mainly among the small phases. Concerning to the similarity among phases, we observed a clustering of the two smallest development phases and the clustering of the two largest ones, in which the floristic composition and most representative species were more similar. In addition, there was a non-directional turnover of the most representative species of each phase, probably related to a mismatch among the population life cycles. Thus, the occurrence of temporal changes in richness’ patterns can indicate the existence of dynamic succession processes in a climax stage community.