The present paper aims at evaluating the forest dynamics - mainly that brought by natural regeneration -in a fragment of dense, terra firme tropical primary forest from 1998 through 1999, municipality of Peixe-Boi (PA). Three 1 ha permanent plots were marked off and every individual within having DBH ≥ 10 cm was registered. Individuals having DBH between 5 and 10cm were sampled out in an area of 6.000 m2, those having DBH between 2 and 5cm were sampled out in an area totaling 2.400 in2, and individuals having DBH under 2 cm were sampled in 240 m2. There are about 143.000 individuals ranging from seedlings to trees, of 337 species and 76 families. Mimosaceae was the family with higher diversity (44 species). Fourteen families occurred as an only species, including 7 families occurring also as an only individual. Considering the whole sample (that is, independently from diametric class) the egression of 56 species versus ingression of 68 was verified, producing a net gain of 12 species. The dynamics of species richeness in natural regeneration is remarkably intense, and the dynamics of abundance of natural regeneration, is more intense than that of floristic richeness. It was also observed that only one family left, while 14 other families entered, thus enriching biodiversity in almost 30%. The highest mortality verified was of Bauhinia cf. rutilans and Mabea aff speciosa (300 and 21 individuals). Rinorea negleta and Lecythis idatimon displayed the recruitment of 171 and 89 specimens. The recruitment/mortality rate was higher than one unit in all diametric classes. The proportion of seedlings needed to obtain a tree, a sapling and a stemlet is 297, 160 e 48 respectively. Richeness and abundance increased during the one year period, as did basal area and biomass.
Forest dynamics; Primary tropical forest; Undergrowth; Diversity and structure; Amazon