In Pará, the Bragantina region was one of the first areas to be massively colonized and to suffer from the process of vegetation removal. It is estimated that 90% of the primary forest has been transformed into secondary forest in various stages of development. The knowledge of the vegetation and the search for appropriate techniques for the elaboration and application of forest management plans can contribute to changes in the socio-environmental framework of the region. Thus, this work is being developed with the objective of contributing to the knowledge of the floristic and phytosociological composition of the tree stratum of secondary forests in the municipality of Bragança-PA (Brazil). Six Permanent Monitoring Plots (PPM) of 50 m x 50 m were allocated for the study of the tree vegetation (diameter at breast height-DAP > 5 cmol). For the 40-year-old capoeira, 2113 individuals, 99 species, 68 genera and 34 botanical families were sampled. The Shannon index was high (H' = 3.5) and within the normally found limit and the equability (J') was 0.77. The species that occupied the first three positions for IVI and IVC were Eugenia tapacumensis O. Berg., Maprouneaguianensis (Aubl) and Neea sp. In the 50-year-old henhouse the sampling included 1616 individuals distributed in 131 species, 62 genera and 38 botanical families. The diversity found by the Shannon index (H') was 4.03 and the equability (O') 0.83. Tapiriraguianensis Aubl, Cuatteria poeppigiana Mart. and Myrcia bracteata (Rich) DC occupied the first three positions for IVI and IVC. The results of this study represent an important step towards defining the distribution and abundance pattern of plant species, constituting a basis for conservation and deepening the understanding of the ecological processes that maintain the biodiversity of this ecosystem.
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