FLORISTIC AND STRUCTURE OF SEASONALLY DRY TROPICAL FORESTS

A floristic and structural survey of the tree community in different environments (slope, Arboreal Caatinga and ecotone to savannah) were carried out in Cavernas do Peruacu National Park, North of Minas Gerais. We aimed to test the following hypotheses: 1 - There is floristic differentiation among the environments; 2 All environments have the same structural characteristics. Venn Diagrams were used to compare both the shared and unshared species among the environments. Tree distribution by diameter classes for each environment was made by means of frequency histograms. An Indicator Species Analysis and usual phytossociological parameters were used. A total of 305 species were found, distributed in 173 genera and 48 families, of which 166 were found in the slope, 204 in the Arboreal Caatinga and 155 in the ecotone. 54 species were exclusive to the slope, 65 to the Arboreal Caatinga and 35 to the ecotone and only 69 species were common to all three environments. 1391 individuals were sampled, yielding an estimated density of 1340.62, 1765 and 1280 individuals. ha(-1) respectively for the slope, Arboreal Caatinga and ecotone. The basal area reached 47.64, 30.05 and 23.29 m(2). ha(-1), respectively for the slope, Arboreal Caatinga and ecotone. The Shannon diversity index and Pielou's evenness were, respectively, 3.49 and 0.80 for the slope, 3.74 and 0.84 for the Arboreal Caatinga and 3.61 and 0.85 for the ecotone. The Arboreal Caatinga and the slope presented a gradual decrease in frequency towards the higher diameter classes whereas the ecotone tended to follow a normal distribution.