Species abundance distribution in tree community of a hill top in subtropical seasonal forest/Distribuicao de abundancia de especies da comunidade arborea do topo de um morro na floresta estacional subtropical

Ecological Models of Species abundance distribution (SADs) of a tree community were investigated to find: (i) if environmental variables are divided stochastically and similarly between species; (ii) if each species exhausts more than half of the existing ecological niche; (iii) if the tree community has many species with intermediate levels of abundance and a few rare and common species; (iv) and if, in secondary succession, the later colonizing species have greatest needs for a specialized niche, so, they are more rare than the initial colonizers species. The data were obtained in eight sampling units with dimensions of 20m x 50m, distributed in a systematic way, totaling 0.8 ha sample; grouped in five models of SADs (broken-stick, niche-preemption, lognormal, Zipf and Zipf-Mandelbrot) for the sample of the tree community and the eight sampling units; the criteria of accuracy of the models were: Akaike, Bayesian and Deviance. The ecological model described the SADs that rank/abundance of tree species for ecological community which was the Zipf-Mandelbrot. The ecological models of SADs that characterized the eight sampling units were niche-preemption, Zipf and Zipf-Mandelbrot. The Zipf-Mandelbrot model postulates the colonization of species under the requirements of environmental preconditions for the establishment of the species, and thus detects up an arboreal community stage of maturity. The ecological models of SADs obtained for the sampling units, separately, show the disparity in the distribution of species abundance within the tree community that was interpreted as the effect of heterogeneity of conditions and environmental resources, and natural disturbances, originating a mosaic vegetation. Key words: trees, curves Whittaker, biological diversity, ecological dominance, forest ecology. Modelos ecologicos de distribuicao de especies (DAEs) em uma comunidade arborea foram investigados para constatar: (i) se as variaveis ambientais sao divididas de maneira estocastica e de modo similar entre as especies; (ii) se cada especie exaure mais da metade do nicho ecologico existente; (iii) se a comunidade arborea possui muitas especies com niveis intermediarios de abundancia e poucas especies raras e comuns; (iv) e se, na sucessao secundaria, as especies colonizadoras tardias tem as maiores necessidades de um nicho especializado, de tal modo que sao mais raras que as especies colonizadoras iniciais. Obteve-se os dados em oito unidades amostrais de dimensoes