Aspectos florísticos, estruturais e fitogeográficos do componente arbóreo em florestas maduras na Serra da Mantiqueira Sul, Minas Gerais, Brasil

Abstract

The quest to understand the complexity of tropical forests has had its relevance recognized in policies for the conservation and recovery of degraded ecosystems, and of environmental quality in altered landscapes. The presence of man has become, along the past five centuries, a factor of destitution of the identity of the Atlantic Forest, making it one of the most endangered natural domains of the world, where testimonies of primitive forests are rare. Initiatives for the conservation of forest remainders represent an opportunity to safeguard the Atlantic Forest, and the Private Reserves of Natural Heritage (RPPN) emerge as an important tool to pursue intermediation of social, economic, and environmental aspects. The northern portion of the South Mantiqueira has few protected areas, and the unique identity and conservationist importance of its forest ecosystems are not yet duly recognized. This situation is probably due to a lack of knowledge about those forest remainders. In order to contribute to scientific knowledge about the area, phytosociological inventories (DBH ≥ 5 cm) were performed in one hectare of forest in each of the three Private Reserves of Natural Heritage (Brejo Novo - BN, Mato Limpo - ML, and Fazenda da Serra - FS), followed by stratified analyses with DBHs ≥ 5, 10 and 30 cm. A comparison was also made between data thus obtained and data obtained in surveys of other stretches of the Atlantic Forest considered "well-maintained" or "mature". In order to verify the floristic and phytogeographic influences, the geographical distribution and conservation status of the species identified were compiled, then phytogeographic patterns and environmental influences were analyzed within a context of 897 areas of the Atlantic Forest. In the three areas were recorded 5501 individuals belonging to 374 species. BN had 167 species, ML had 173 species and FS had 227 species. The species diversity index (H') was respectively 4.36; 4.33; and 4.70 nats.ind-1 for BN, ML, FS. The evenness (J) was 0.85; 0.84; 0.87, respectively. The total basal area was 32.94; 37.83; and 44.86 m².ha-1, respectively. Stratified analysis of the arboreal component provided a less static view of the floristic and structural relations of forests, fostering a better understanding of the progress of the succession process, and demonstrating that interpretations of this process based only on the percentage of rare species can promote misinterpretations. Within the general trend of data collected, we may conclude that the percentages of dead trees seen in the three areas of study were not good indicators of the conservation status of those areas. The patterns found show that the areas of study are referential of the natural variability of the Atlantic Forest, in their late succession process. The comparison between those three areas and the group of areas taken as a reference reinforces this finding. The flora found shows a strong influence of the Atlantic phytogeographic domain, especially of the Ombrophilous Forest. The percentages of species that are exclusive of each of the three areas demonstrate the high proportion of species replacement along the gradient formed between them, around which varied floristic influences are gathered. This group of unique contributions is also composed mainly of species represented by a small number of individuals. These characteristics, a key of the relevance of the study areas, also point to the uniqueness of this portion of the Mantiqueira for the conservation of the Atlantic Forest. Thus, we hope to highlight the important contribution of private reserves as a voluntary instrument able to safeguard that which is not included in the priorities set by public conservation policies.