Gradiente pedológico-vegetacional de Cerrado em Paraopeba, MG

Abstract

The Cerrado physiognomic and structural mosaic is determined greatly by the soil fertility gradient, as well as by the irregularity of fire occurrence. The factors have an influence on the structure and floristic composition of the vegetation. Therefore, this work aims to classify the Paraopeba National Forest soils in Minas Gerais and to study the community and vegetation population variation according to the soils physical and chemical characteristics. Samples were collected with an auger and morphological observations were made for soil description in five different profile locations. For the routine chemical and granulometric analysis soil samples were collected every ten cm until the depth of 30cm, and from then on every 20cm until 150cm, with a total of nine samples per profile. The color, detailed morphological characteristics and P content were determined only for the 0-20cm and 0-40cm depth samples. Floristic composition and structure analysis were determined from a phytosociological sample of the woody vegetation, using the plot method. For sampling, five 20 x 100m plots were set out, totalizing 1 ha, where only the individuals with a soil height circumference (CAS) ≥ 10 cm were included. The floristic variation analysis was verified by floristic similarity in between the five plots and the structural variation through the analysis of the dissimilarity in which absolute density and dominance were used. Four soil classes were sampled, Red Latosoil, Red-yellow Latosoil, Yellow Latosoil and Cambisoil. The total FLONA richness was of 132 species distributed in 47 families. Of the species sampled, 111 were identified to species level, 12 to genus level, four to family level and five remained undetermined. The families that presented greatest richness were Fabaceae (18 species), Myrtaceae (9), Vochysiaceae (8), Bignoniaceae (7), Malpighiaceae (6), Rubiaceae (6), Anacardiaceae, Annonaceae, Erythroxylaceae e Melastomataceae (4). The five studied areas proved to be floristically and structurally distinct. A structural variation exists along the Paraopeba FLONA, even within the areas with equal phytophysiognomies as in the Cerrado s.s. over CXb and the Cerrado s.s. over LA. The variation of the Cerrado vegetation in the Paraopeba FLONA relates to the pedological variations encountered. Richness is positively correlated to fertility and negatively correlated to the aluminum content. The floristic similarity doesn’t relate to the gradients, being influenced before that by the proximity of samples. The structural variation is less related to fertility than to aluminum. Some species showed a preference to certain environments as for example, Miconia albicans, that presented large densities where the aluminum content was high. Dilodendron bipinnatum was present only where the aluminum content was low, but with high Ca2+ content. Alibertia edulis and Myrcia tomentosa occurred together associated to lower aluminum content and larger basal areas, which is being interpreted as less tolerance to aluminum and more tolerance to shading. Xylopia aromatica occurred associated to larger aluminum content and larger basal areas, which is being interpreted as larger tolerance to aluminum and shading. The pedological factors, especially aluminum, have a strong influence on physiognomy, floristic composition and the structure of the Cerrado in the Paraopeba FLONA.