The Atlantic Forest has a heterogeneity that is still largely unappreciated, especially that associated with altitudinal factors; this has rarely been examined in the northern extension of this biome. The study investigated the occurrence of variation in floristic composition, diversity, and vegetation structure at two altitudes in a remnant area of forest in southern Bahia state. A total of 0.5 ha of vegetation was sampled in five separate plots established in a wet forest in the RPPN Serra Bonita, Bahia, Brazil. A total of 354 species belonging to 68 families were found, with Myrtaceae, Fabaceae, Rubiaceae and Lauraceae being the richest taxa. The two altitudinal sites showed significant differences in density, basal area and structure. There were notable changes in forest structure with increasing altitude, reflected in higher densities of the understory and a reduction in species richness. Serra Bonita had high species diversity that was similar to other areas in Bahia, but higher than found in the Atlantic Forests of southeastern Brazil. The forest sections sampled were well preserved, as indicated by the abundance of woody vines, elevated basal area, and lack of evidence of significant logging activities. The variation detected between the areas suggests the existence of abrupt structural modifications influenced not by edaphic factors but by rainfall differences, temperature variations, and by local barriers determined by the steep topography.
tree diversity; montane forest; diversity profiles; rarefaction curves; similarity
