STRUCTURE AND DIVERSITY OF A TROPICAL DRY FOREST ON RESIDUAL RELIEFS IN NORTHEASTERN BRAZIL

We studied the structural characteristics of forests to better understand their current condition and help plan for the sustainable management of their resources. We delimited 14 sampling units, according to physiognomy and geomorphological position (base, medium slope 1, medium slope 2, and inselberg). To characterize vegetation structure, we used the transect method (50 x 2 m) following to Method of Phanerophytes and Chamaephyties Inventory. After this step, we classified the transects into four biotopes: (CAR: Caatinga on rocky substrate, CBA: Caatinga with open woods, CBC: Caatinga with closed woods, and CDA: degraded shrubby “Caatinga”), according to geomorphological position. Our objective was to test the hypothesis that adjacent areas with different topography differ from one another. For those comparisons, we calculated parametric and non-parametric tests in the software R. We recorded a total of 67 species, including trees, shrubs, and herbs, and high values for diversity (3.4 nats/individual) and evenness (0.83). Based on the comparison between rarefaction curves and non-parametric estimates, we observed the highest diversity in the category Caatinga with closed woods (CBC). Considering its species composition and abundance the group degraded shrubby Caatinga      (CDA) is undergoing succession. The Jaccard index did not suggest floristic similarity between biotopes, but rather pointed to a diverse floristic composition in the area, with the presence of species either common or rare to the Caatinga   and a higher heterogeneity than among other Brazilian semiarid areas