FLORISTIC COMPOSITION AND STRUCTURE OF A TROPICAL DRY FOREST AT DIFFERENT SUCCESSIONAL STAGES IN THE ESPINHACO MOUNTAINS, SOUTHEASTERN BRAZIL

The floristic composition and structure of intermediate and late successional stages of a tropical dry forest (TDF) growing on limestone outcrops, situated in the southern portion of the Espinhaco Mountains, Southeastern Brazil, was studied. In each fragment, three plots of 20x50m were delimited, totaling 0.3ha for each successional stage. In each plot, all trees with a diameter at breast height (DBH) >5cm were sampled and identified. Standard phyto-sociological parameters were calculated and compared between stages. The most representative families in the two successional stages were Fabaceae, Apocynaceae and Malvaceae, but species composition differed between intermediate and late stages: species with highest importance value in the former were Myracrodruon urundeuva, Rauwolfia,sellowii and Inga platyptera, whereas Anadenanthera colubrina, Myracrodruon urundeuva and Bauhinia brevipes predominated in the latter. The main parameters measured varied with the successional stage. In the intermediate stage, the structural parameters were: basal area 17.8m(2).h(-1), density 1076 individuals/ha, average height 6.30m, species richness 23, while community indexes were Shannon-Winner biodiversity 1.51 and Pielou evenness 0.48. For the late succession stage, the structural parameters were: basal area 29.3m(2).h(-1), density 1226 individuals/ha, average height 7.7m and species richness 38; community indexes were Shannon-Winner's diversity 2.38 and Pielou's evenness 0.64. Due to the marked isolation, this TDF has a unique floristic composition. Results demonstrated important changes in floristic composition and structure along two successional stages, contributing to ecological process understanding. The limited knowledge about this rich ecosystem was expanded and the urgent need for its preservation is reinforced.