Estrutura e composição do estrato arbóreo em diferentes trechos da Reserva Biológica Municipal Santa Cândida, Juiz de Fora-MG

Abstract

The anthropogenic disturbances as coffee plantation in the Zona da Mata of Minas Gerais were main factors to the elimination of the vegetal coverage. After the reduction human activities in Juiz de Fora, there was the recovery of degraded ecosystem, resulting on secondary forests. The Biological Reserve Santa Cândida, situated in Juiz de Fora county (21º41' 20''' 40' S and 43º20' W), Zona da Mata of Minas Gerais, is a remnant secondary forest fragment with an area of 113,3 ha, whose tree community composition is still unknown. This study had as its aim (a) characterize the foristic composition and the structure of the vegetation in different areas in Biological Reserve Santa Cândida, (b) compare the floristic composition in internal and edge stands in the forest fragment through similarity coefficient, (c) test by cluster analysis the floristic composition among tree community sampled in Biological Reserve Santa Cândida and other surveys in Minas Gerais State. The phytosociological survey was made by 84 plots laid on the edge (Bor-1, Bor-2, Bor-3) and internal (Int-1, Int-2, Int-3) stands, resulting in 0,84 ha sampled area. All trees with circumference at breast height ≥ 15 cm were identified and measured (circumference and height). The survey registered 1.968 trees, distributed in 176 species, 113 genera and 52 families. The values of the Shannon-Wiener index (H') and equability respectively were 4,298 and 0,83. The families Fabaceae, Lauraceae, Meliaceae and Euphorbiaceae, as in species richness as abundance, were less common in edge stands, suggesting low tolerance in hardest biotic and abiotic conditions. Differently, Moraceae and Erytrhoxylaceae showed significant increase in species and individuals amount in the edge stands. In the case of sampled death plants and the species Cupania ludowigii, Piptadenia gonoacantha, Myrcia splendens, Apuleia leiocarpa e Guapira venosa were registered highest importance values in reserve. Some 24 trees species sampled in this study were not registered with distribution in Valley of South Paraíba and 9 species presented new occurrence in Minas Gerais State. Approximately 41% of the sampled individuals had height values between 6,1 m and 10 m with wide range in height class distribution and emergent layer reaching 36 m. The analysis of size class distribution demonstrated a concentration of individuals in the lesser size class, which may assure the canopy regeneration by replacement of the death plants. There wasn’t significant difference between Shannon-Wiener index between stands, but the internal stands showed highest observed species richness. The Int-1 and Int-2 stands had highest value to similarity coefficient (58,6%), which promoted the gathering of their floristic compositions through cluster analysis. However the different floristic compositions among other stands hindered the observation of other groups. This floristic ix heterogeneity in the Biological Reserve Santa Cândida tree community produced clear separation of three of six stands by detrended correspondence analysis (DCA) and resulting ordination analysis was directly influenced by tree species presents in edge stands Bor-1 and Bor-2. The statistical analysis demonstrated significant difference in the parameters density, number of species by plot, size class distributions and height class distributions between internal and edge stands. The ecological group analysis in this survey showed predominance of early and late secondary in detriment of pioneer species. The abundance of early secondary species affected the successional index value in the forest community (SI=2,11), indicating that forest community is intermediate successional stage. However, in the edge stands (Bor-1, Bor-2) the successional index values were about 2, due to an increase in the abundance of pioneer and a decrease in late secondary species, suggesting an initial stage in successional process. Therefore, the tree community composition and structure gained in this survey characterized a mosaic in the forest fragment and made the implantation of conservation activities in bordering stands evident to assure the integrity of the unit of conservation.