The aim of this study was to analyze and to compare the floristic composition and horizontal structure of managed forest (FM) and unmanaged forest (FNM). A stratified random sampling was used with 12 plots in the FM and 12 plots in the FNM. In plots of 28 x 350 m, all individuals with circumference at breast height (CAP) greater than or equal to 31.4 cm and smaller than 94.2 cm (inclusion level I) were measured, plots of 28 x 100 m, individuals with ≤ 94.2 cm CAP <157.1 cm (inclusion level II), plots of 28 x 250 m individuals with CAP ≥ 157.1 m (inclusion level III). In both forests 216 species were found, distributed in 44 botanical families. The FNM had a higher diversity index of Shannon-Weaver (H ') (H' = 4.47). The floristic composition, in the FM did not change significantly during the forest management. However, there were significant changes in richness and basal area between FM and FNM because of the harvesting done which resulted in the removal of individuals in commercial classes and also to the damage caused to the remaining trees. The most important species in ecological FNM were RinoreaguianensisAubl (Violaceae), Pouteriabilocularis (H. Winkler) Baehni (Sapotaceae) and Sclerolobiumpaniculatum Vogel (Fabaceae). In FM, were RinoreaguianensisAubl (Violaceae), Manilkarahuberi (Ducke) Chevalier (Sapotaceae) and Eschweileracoriacea (DC.) S.A.Mori (Lecythidaceae). For the period considered, the basal area seems to be recovering properly.
phytosociology; forest management; Amazon forest