Composição florística e ecologia de epífitas vasculares em fragmentos de Floresta Estacional Semidecidual na Serra da Mantiqueira, Minas Gerais, Brasil

Abstract

The vegetation heterogeneity is one feature responsible for the high biodiversity found in Atlantic forest, especially for the Seasonal Semidecidual Forest (SSF), which, despite high richness and endemism, is less known than other physiognomies like the rainforests. This phytophysiognomy is one of the most affected due to, especially the urban occupation in the Southeastern Region of Brazil. Currently in Minas Gerais, this physiognomy is represented especially by remnants of secondary forests. In this sense, we must highlight that the Serra do Ibitipoca, due to its biological importance, appears among the priority areas for conservation of the flora in this state, and nevertheless, is suffering with fragmentation and destruction of habitats. Fragmentation of habitats greatly threatens the biodiversity, affecting especially the epiphytic community. Other important feature in the composition of this community is the elevation gradient which provides high habitat heterogeneity even at short distances. Epiphytes are an important component for diversity of the tropical forests due to its high number of species, also presenting relevant ecological function. We studied five fragments with sizes varying between 2 and 8 ha and altitudes varying between 1230 and 1430 m.s.m. in the Serra da Mantiqueira, Minas Gerais between September 2013 and December 2016. Results are presented in two chapters. The aims of the first chapter were to realize the survey of vascular epiphytic community and evaluate the importance of the habitat heterogeneity to the richness and composition of species. We recorded 96 species of vascular epiphytes distributed in 40 genera of which Peperomia was the richest (eight spp.) and 10 families, of which Orchidaceae was the richest (30 spp.). The ferns presented richness higher than expected, probably due to the high altitude of the studied area. This study presented the highest richness to date know for SSF, highlighting the importance of maintenance of fragments with distinct structures for the epiphytic community. In the second chapter we evaluated the diversity of the community of vascular epiphytes and the correlation of species xiii richness with altitude and fragment size, besides phorophytes sizes. In each fragment we evaluated 60 largest phorophytes with at least one epiphyte. We calculated for each fragment the indices of diversity of Shannon (H‟) and equability of Pielou (J), besides the indices of taxonomic distinction (Δ+) and variation in taxonomic distinction (Λ+). An analysis of linear regression was conducted in order to verify correlation between altitude, area size and richness of species. We sampled 300 phorophytes with 1270 occurrences of epiphytes, distributed in 85 species. The number of species did not correlate with the size of the fragments pointing to a distinct history of disturbance, a feature confirmed by the relatively low indices of similarity. The closest and richest fragments presented the highest values of H‟ and Δ+ showing the best conservation status among the analyzed fragments. Although we did not find significant correlation between altitude and richness (p>0.05) it was clear the influence of the elevation in the composition of the community once seven species occur up to 1230m.s.m. and 13 were present only above the 1380m.s.m.