This study aimed to characterize the composition and density of the seed bank of the floodplain forest located in the Environmental Protection Area, Combu Island , in the city of Belém , Pará , Brazil . 6 were systematically allocated plots of 20 x 20 m in three areas of the forest that had no human disturbance, 100 m apart from each other for a total of 0.24 ha. In each plot we used a jig wood measuring 50 x 50 cm for the standardization and collecting 20 samples of soil seed bank at 20 cm depth was discarded litter. The 120 samples were placed in 30 plastic bags and transported to the Botanical Garden located in the research campus of the Museu Emilio Goeldi. The samples were distributed in plastic containers measuring 36 cm x 5 cm deep in a nursery with black drop to 50 %. The experiment was conducted from may to august 2013 with the quantification of seedlings from 10 cm and identified at family, genus, species and calculated the average density of seedlings. To compare the diversity of species we used the diversity index of Shannon-Wiener (H') and Sorensen similarity index (S').Registered 26 families, 38 genera and 41 species. The most representative families were Poaceae, Asteraceae and Cyperaceae with four species each. The most dominant species and their average densities were Polybotrya caudata Kunze, Cecropia
palmata Willd., Cyperus difformis L., Alternanthera tenella Colla, Clidemia hirta (L.) D. Don, Commelina erecta L. e Phyllanthus niruri L. The -3 -3 herbaceous growth was dominant in all areas . Was recorded index H'= 0.86 nats ind for Area 1, H' = 1.91 nats ind to Area 2 and H'=-3 1.35 nats ind to the area 3 and the similarity of S'= 0.50 for Area 1, S'= 0.48 for area 2 and S'= 0.50 for area 3. The floristic composition
of the seed bank was higher than those recorded in other lowland forests and mismatched families and species commonly recorded in the upper stratum.The dominance of herbaceous species characterizes a possible natural or anthropogenic disturbance in the area and the fact Polybotrya caudata adapt to the shaded and moist.
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