This work is a study on the spatial structure, diversity and types of diaspores of populations of trees in tropical forest, especially in old secondary forest of Masako forest reserve. It is part of community ecology and main objective was to document the involvement of the biology of the diaspores of tree species in the definition of spatial patterns of distribution of their populations. Thereby, in the context of the successional dynamics contributing to the understanding of its action on the coexistence of species in the tropical forest. The method used was that of patches or parcel established on a1'1area of two hectares. Each one hectare plot was subdivided into four plots or subplots of 50 m x 50 111 (total 8 subplots) in which all individuals at ~lO cm DBH were identified. At the end of the inventory, 625 individuals owned 91 species and grouped into 77 genera and 27 families were listed. OW' results on the spatial distribution of the population show that in this forest formation taken population distribution across display an aggregated structure similar to spatial structures observed in mature forests. However, the disintegration of these populations by intense samples of individuals, tends to make more random dispersions. As for mature stands, were observed in the secondary forest of this reserve, a clear dominance of types of diaspores sarcocbores populations. Species diversity is high (Simpson: 0.95;) Shannon: 3.71; Fairness: 0.82) and reaches values comparable to those obtained in mature training (Simpson: 0.95;) Shannon: 3.48; Fairness: 0.91).Spatialiy, there is a floristic structure related to U1e consolidation of the species in this indicating the influence of environmental factors on the spatial organization of the vegetation.