Floristic and structural variation in response to the environmental heterogeneity in a cloud forest in Ubirici, Santa Catarina, Southern Brazil

The objective of this study was to check if the tree component of a cloud forest, located in Urubici, SC, shows structural and floristic patterns variations associated to the environmental heterogeneity. For the tree community characterization, a total of 25, 20x20 m plots were allocated in the forest fragment. All trees with circumference at 1,30 m (CBH) >= 15,7 cm were measured (CBH and height) and identified. In each plot, environmental variables related to soils physical and chemical traits, terrain, canopy cover and environmental impact were collected. The data were analysed by Mann-Withney test, non-parametric multivariate ANOVA (NPMANOVA), nonmetric multidimensional scaling analysis (NMDS) and indicator species analysis. From exploratory analysis of data, it was observed that the NMDS indicated the occurrence of two floristic-structural groups associated to terrain declivity. The two sectors differed in their environmental characteristics, with the lower declivity sector demonstrating higher values of organic matter, sand, aluminum content and cation-exchange capacity, and the higher declivity sector with higher values of elevation difference, silt and calcium content, base saturation and pH. The environmental heterogeneity influenced the floristic-structural organization of the tree component and the occurrence of indicator species at the two sectors. The conditions of the physical environment, associated with the soil characteristics and declivity conditioned community organization in the fragment studied.