INFLUENCE OF SOILS AND TOPOGRAPHIC GRADIENTS ON TREE SPECIES DISTRIBUTION IN A BRAZILIAN ATLANTIC TROPICAL SEMIDECIDUOUS FOREST

AbstractThis study investigated the effect of environmental variables such as soil class, soil water availability, topography and slope on spatial distribution patterns of tree species in a Brazilian Seasonal Semideciduous Forest area. Floristic and structural data for a tree community were obtained by sampling 100 plots 10 × 10 m in which every tree with trunk diameter (dbh) ⩾ 4.77 cm at 130 cm above ground level was sampled. The area under study showed a marked soil gradient, directly associated with the topography: flat hilltops with Al3+-rich Dystric Latosols give way to steep colluvial slopes with shallower and more Dystric Cambic Latosols without Al3+, changing over, at the bottom of the hollows, to Epieutrophic Cambisols richer in nutrients. The floristic-sociological parameters analysed for the soil habitats did not differ statistically from each other. The diversity and equability indices were 3.6 and 0.84, 3.48 and 0.85, 3.49 and 0.84 for the Dystric Latosol, Dystric Cambic Latosol and Epieutrophic Cambisol, respectively. The soil variables (related to the fertility and texture) and the soil water regime (drainage) were probably the principal factors determining the spatial distribution patterns of tree species in the forest.