The purpose of this study was to describe the floristic composition and structural changes in three sites of the arboreal community of a semideciduous forest in the Tripuí Ecological Station (EET), located in Ouro Preto, Minas Gerais State, Brazil. Sites one (A1) and two (A2) are the most conserved patches, without any disturbance reported during the last 30 years. Site three (A3) is the youngest successional portion of this forest and it occurs in an old area of tea plantation abandoned for 40 years. In each site, every tree with perimeter at breast height (PBH) 3 5 cm found in three quadrats of 10 x 30 m was sampled. The soils in the EET were considered structurally young, with low fertility. Sixty eight species of trees belonging to 42 genera and 25 families were registered. The most representative families in number of species were Myrtaceae (13), Lauraceae (9), Fabaceae (5), Flacourtiaceae (5) and Rubiaceae (5). The distribution of PBH and height classes of A1 and A2 are significantly different from A3. The Shannon index was higher in A1 (3.15), followed by A3 (3.00) and A2 (2.36). Sorensen index showed a low floristic similarity among the three sites studied. The floristic and structural differences found in the forest studied are due to differences in the intensity of human interference in the past.
Floristic; structure; semideciduous forest; Tripuí Ecological Station
