Composição florística e estrutural da regeneração natural em uma floresta manejada no município de Itacoatiara (AM)

Abstract

The regeneration of vegetation is a natural process in which each species develops its own characteristics. Knowing the process of natural regeneration, when subjected to selective logging is of fundamental importance for the success of forest management. Aiming to analyze natural regeneration after such interventions, six plots of 10 x 100 (level 2 = 2.4 ha) were allocated divided into sub plots of 2 x 2 m (level 1 = 0.288 ha) in three areas with different ages of exploration and a witness in the logged forest of the timber company Precious Woods Amazon Ltda, located in Itacoatiara (AM). At each level were taken three size classes, level 1 (C1 = 0.50 m ≥ height < 1.50 m; C2 = 1.50 m ≥ height < 3 m; C3 = height ≥ 3 m and DBH < 5 cm), level 2 (C1 = 5 cm ≥ DBH < 10 cm; C2 = 10 cm ≥ DBH < 15 cm; C3 = 15 cm ≥ DBH ≤ 20 cm). Plant height was measured with a ruler graduated in meters and the diameter was measured with a diameter tape, the identification of plants was made in the field and in the laboratory and much of the plant material was collected, pressed, dried and identified by comparison with the herbarium material. The floristic composition consisted with 4365 individuals (level 1 = 2278, level 2 = 2087), 49 families (level 1 = 44, level 2 = 46), 154 genera (level 1 = 125, level 2 = 126) and 416 species ( level 1 = 341, level 2 = 268). The Shannon diversity index was 5.24 (level 1 = 4.97, level 2 = 4.95) and floristic similarity of 0.38 (38%) with 193 species common to both levels. The vertical structure of the natural regeneration showed a decrease in the number of individuals at both levels, according to the amplitude of the class size adopted. The first class of each level (C1) detained most of the individuals, when compared to the last two classes. At both levels of approach, the different areas analyzed were dominated by individuals belonging to family Burseraceae, as to the number of species, the families differed among the areas examined at the two levels. For the size classes at the two levels of approach, 35 (8.41%) species covered all size classes. Among those that occurred in all classes, for both levels, are the species that are exploited by the company: Goupia glabra Aubl. (cupiúba), Scleronema micranthum (Ducke) Ducke (cardeiro) and Zygia racemosa (Ducke) Barneby & J.W. Grimes (angelim rajado). Regarding the vertical structure analyzed for the level one species Duguetia flagellaris Huber (envira amarela) was the most important in the parameter on natural regeneration. The most important species in the horizontal structure forest of the for level 2 was Protium sp. 2. (breu vermelho). The forest is considered non-stocked for the species exploited by the company for level 1, because the stock index was 18.43% as in the level 2 was considered the forest stocked because the stock index was 72.50%.