Regeneração natural de um fragmento da floresta estacional decidual na reserva biológica do Ibicuí-Mirim (RS)

The natural regeneration under below the lower stratum of the Seasonal Forest in the Biological Reserve of the Ibicui-Mirim (29°32'27 " S and 53°48'35 " W) in the county of Sao Martinho da Serra (RS) was inventoried in different slope classes in a topographical gradient, with the purpose of evaluating the dynamics and the existent environmental correlations of forest distribution of the species. They were allocated 28 plots of 10x10 m along the topography gradient, to sample all the individuals with perimeter at breast height (PAP) from 5 - 29,9 cm. They where also collected topographical data and superficial soil samples (0 - 20 cm) for chemical and texture of the soil analysis. It was registered 698 individuals, distributed in 28 families, 49 genera and 59 species. The natural regeneration presented high index of diversity of Shannon (H' = 3,21 nats. /individuo), correlated the low ecological dominancy by the equabilidade of Pielou (J' = 0,78). The main species of the study area were Trichilia elegans A.Juss., died standing trees, T. claussenii C.DC., Sorocea bonplandii (Baill.) W. C. Burger, Lanj. & Wess. Boer e Cupania vernalis Cambess., with 44,1% of the accumulated value of importance. The canonical correspondence analysis (CCA) showed variation of the environmental heterogeneity of the fragment, being the slope the main characteristic in the condition of exhibition of the bedrock, depth of the soil and stability of the land, they, influencing in the abundance of some species from the natural regeneration