Spatial distribution, association patterns and richness of tree species in a seasonal forest from the Serra Geral formation, southern Brazil

Abstract

This study aimed to determine the spatial distribution of the most abundant tree species, to look for relationships that may be responsible for their distribution and to compare the expected richness along the Serra Geral formation in the state of Rio Grande do Sul, Brazil. An one-hectare plot was divided in 100 contiguous 10 x 10 m sampling units and all individuals with at least 4.8 cm diameter at breast high were measured and identified. Each sampling unit received a description of the spatial position through metric coordinates (x,y) in order to quantify the spatial pattern. Later, an association index among species was applied. Th e observed richness was rarefi ed and compared to other surveys located on the slopes of Serra Geral in Rio Grande do Sul. We surveyed 1,063 individuals belonging to 69 species and 33 families, and the Shannon’s diversity index showed a diversity of 3.35 nats (Pielou’s species evenness - J’ = 0.79). Most species showed an aggregated distribution. Both association and dissociation patterns occurred among species leading to distinct forest patches. Rarefaction results showed a decrease of Atlantic species, which were replaced by typical seasonal forest species, when analyzing fl oristic contingents towards the west.