Composição, estrutura e similaridade florística do estrato arbóreo de três fragmentos de floresta atlântica na Serra da Pedra Branca, Caldas, Minas Gerais

Abstract

The Atlantic forest has been degraded since the time of discovery of Brazil. Today is reduced to 7% of its original extent and is considered the world's eighth largest hotspot. Regions of the Atlantic Forest in Minas Gerais, yet without studies of inventory, have been proposed as priorities for scientific research. The Serra da Pedra Branca, located in the municipality of Caldas, southwestern state of Minas Gerais, is part of the Atlantic forest domain and constitutes one of the last remnants of this vegetation in the region. The region is characterized by presenting syenitic and granitic outcrops, where patches of montane forest and upper montane are interpolated by altitude fields. The aims of this study was to characterize the floristic composition and structure of forest trees in diferent gradient altitudinais (1400, 1600 e 1700 meters). Three fragments were sampled in different altitudinal gradients using the method of measuring distances with a transect of 300 meters per fragment, guided by compass with sights always following the same azimuth, sampling one point every ten meters, totaling 30 points per fragment. The fragments are named Mata da Bica da Onça, Mata da Pedra Grávida, Mata da Estrela. The phytosociological parameters analyzed were: density per unit area, relative density, absolute frequency, relative frequency, relative dominance and percentages of importance and coverage. Were described the horizontal and vertical structure of the areas, the diversity was calculated using the Shannon-Wiener index and the testing hypothesis about differences between the two indices using the test proposed by Hutcheson. The similarity was calculated using the similarity index of Sørensen. A total of 360 individuals were sampled, 120 per transect included in 37 Families, 65 genera, 84 species and an undetermined specimen. The most abundant species Alchornea Were triplinervia (Spreng.) Müll.Arg. (29 Individuals), Rapanea gardneriana A.DC. (15), Perkins and Sapium Mollinedia argyrogyna haematospermum Müll.Arg. (Individuals 13 each), Rudgea gardenioides (Cham.) Müll.Arg. (12), Blepharocalyx salicifolius (Kunth) O. Berg and Pepper pseudocaryophyllus (Gomes) Landrum (11 Individuals each), Nectandra oppositifolia Nees and Rapanea umbellata (Mart.) Mez (10 Individuals each) representing 34.44% of total. From the data of floristic composition and structure, the fragments could be differentiated into dense rain forest Upper montane (Mata da Bica da Onça) and semideciduous forest Montana (Mata da Pedra Grávida e Mata da Estrela). The dendrogram generated from the Sørensen coefficient showed that the Serra da Pedra Branca is more similar to altitude forest areas and that, the latitude and soil factors strongly influence the floristic similarity.