Composição floristica e estrutura da comunidade arborea num gradiente altitudinal da Mata Atlantica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

In this study, we describe the changes in soil properties, and in the tree community structure and species composition of the Brazilian coastal Atlantic rain forest along an altitudinal gradient. The study was carried out in the Serra do Mar State Park, São Paulo state, south-eastem Brazil (44048 W e 23022 S). According to the IBGE s c1assification system, the vegetation is dense ombrophilous forest, generally named Atlantic rain forest. Plots were established at five altitudes: 2 m (coastal plain), 100, 300, 600 and 1000 m (slope). The total area surveyed was 2.34 ha. Soil samples were collected and analysed for their properties. Significant differences among altitudes were found for soil pH, leveI of K+, A13+ and soil texture. In each plot all trees, palms and tree fems (_ 5 cm DBH) were enumerated, measured and identified. A total of 3970 trees, 298 species, and 61 families were recorded. Diversity was lowest at the coastal plain and greatest at 300 m. The composition of species varied with altitude, and three groups were differentiated by multivariate analyses (Cluster and Twinspan): coastal plain (2 m), middle slope (100-600 m) and summit (1000 m). The altitudinal range of many species sampled in the present study is narrow and only Euterpe edulis, Campomanesia guaviroba, Garcinia gadneriana, Sche.fflera angustissima and Guapira opposita showed a distribution with no c1ear altitudinal pattem. The structure of forest also varied with altitude: tree robustness was highest at 100 and 300 m and tree slendemess was highest at coastal plain (2 m) and summit (1000 m). Tree density (number ofindividuals ha-l) was higher at the coastal plain and lower at 100 m. Basal area was higher at 100 m and lower at the coastal plain. Maximum tree heigth was highest at 100 m while the lowest values of maximum height were found at the coastal plain and at 1000 m. The lower diversity and stature of sandy coastal and upper montane forests is presumed to result from relatively harsher environrnental conditions which restricts tree growth, such as restricted soil dranaige or reduced solar radiation under high cloudiness. Climatic factors such as temperature, rainfall, atmospheric humidity and solar radiation can also play an important role in determining the variations in tree species distribution. Different species are affected in different mannners by the variations in the physical environrnent, resulting on the variations in tloristic composition over the short altitudinal gradients of the Atlantic Forest. The analyses evidenced that tloristic and structural differences among the altitudes allow recognition of different communities along the gradient that can be classified into three formations: Lowland Dense Ombrophilous Forest, (2 m coastal plain), Lower Montane Dense Ombrophilous Forest (100-600 m) and Montane Dense Ombrophilous Forest (1000 m)

ASSUNTO(S)

flores - mata atlantica flores - metodos de estudo comunidades vegetais - mata atlantica

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