Padrões de diferenciação florística no extremo sul da Mata Atlântica: influências ambientais e histórica

Abstract

The spatial variation of species abundance can be determined by a series of historical and environmental causes. In order to identify floristic groups and their relationship to a set of soil and climatic variables (environmental), the geographic area (historical) in structuring the composition of trees along formations and seasonal rainforests from southern Atlantic forest, Brazil drew from the literature data on the composition and abundance of tree flora (DBH> 9.5 cm) of 52 sample units with about 1 ha in extension. The communities were characterized using seven climate, nine soil and three structural variables, as well as the Jost diversity, altitude and geographic coordinates. Ordination analysis were employed for the synthesis of soil, climatic and structural descriptors (PCA), the floristic structure between plots (NMDS) and subsequent correlation with environmental factors. Through hierarchical cluster analysis identified himself with floristic groups using indicator species, which were classified according to their migratory corridors. By using the G test, we evaluate the independence between the historic routes of dispersion and the composition of indicator species groups. Factors related to the niche of the species, such as temperature, total precipitation, and secondarily drainage, fertility and soil depth, are consistent with the distribution of the composition tree. Likewise the longitude is a strong predictor of floristic variation forming a gradient along the corridors of dispersal tropical flora, and the groups obtained were dependent indicator species of origin of their contingents Unlike the diversity, it was identified a structural gradient of basal area variation, average height and density between Araucaria forest and seasonal forests,. The forestry groups exhibit different degrees of separation between themselves. Seasonal forests and form a dense rain forest floristic gradient along two continuous migration corridors in order to consist a single block. The Araucaria forest is a group dissimilar to these formations with a subdivision marked by unique indicator species. Environmental and historical factors are responsible for both, the division between groups that may be abrupt or gradual, as well as the internal differentiation of these formations.