Phytosociology and soil attributes in an Araucaria forest in southern Brazil

In the southern area of S. America, the natural forests are widespread ecosystems. However, currently there are only small remnants remain. Knowledge about the species diversity and relationships between forest species and their environment provide important information on the functioning of these ecosystems. This study aimed to analyze phytosociologically the tree component of an Araucaria Forest fragment, determining the main phytosociological indicators, and correlate soil attributes with species abundance and distribution. The study site, Parque Natural Municipal de Sertão, located in S. Brazil, is a conservation unit 570 ha, and it is mainly consisting of an Araucaria Forest, part of the Atlantic Forest biome. The methodology employed consisted of sampling 90 plots of 10×10 m, totalizing 9,000 m2 of area. All individuals with DBH (diameter at breast height) larger than 5 cm were identified and measured. Chemical analysis of soil was carried out on the first 10 plots, to check the normality of the data. The Pearson Correlation Coefficient was used to correlate species with more than five individuals with soil data. 88 tree species, belonging to 33 botanical families, with a total of 1.411 individuals were identified. Shannon diversity index (H') for species was 3.496 (nats) and evenness (J') was 0.771. The species with the highest importance value index (IVI) were Nectandra megapotamica, Allophylus edulis, Araucaria angustifolia, Matayba elaeagnoides, Prunus myrtifolia, Cupania vernalis, Ilex brevicuspis and Casearia decandra. The families with the highest number of individuals were Sapindaceae (391) and Lauraceae (198). Soil potassium showed a significant positive correlation with three species (Capsicodendron dinisii, P. myrtifolia and Sebastiania commersoniana), and can be considered the most influential variable for the species distribution in this study.