Abstract
The Araucaria forests of Southern Brazil have been drastically reduced as a result of anthropic intervention and are currently found at different stages of succession. The objective of our study was to understand the influence of forest fragmentation on the phytosociological composition of its tree component. The composition of floristic groups of the tree component and their correlation with the edaphic and environmental variables in a fragment of the Araucaria Forest in the municipality of Curitibanos, state of Santa Catarina, Brazil was analyzed. A hundred and ten permanent continuous plots (10 m²) with forest edges of different origins and formation times were established for sampling. Trees with diameter ≥ 5 cm at breast height (DBH) were measured and identified. Using TWINSPAN, data were analyzed for species importance values (including indicator species) in the formation of floristic groups. Floristic similarities resulted in separating groups conditioned by the forest succession. The presence of the invasive species Pinus taeda L. and pioneer species at the forest expansion border contributed to the formation of a spatially cohesive group. The other areas did not show influence of edge effects, being in an initial secondary succession stage, dominated by Jacaranda puberula Cham. Low edaphic variation among the classes of lithosols in a flat relief had no influence on the formation of floristic groups.
Highlights
The overall forest cover by the subtropical forests with Araucaria has been drastically reduced over the last hundred years, making them one of the most threatened forest formations in Brazil
The fragment has three borders: one, limited by an open road and pastures formed more than 60 years ago; another, formed by a firebreak and a forest of Pinus taeda formed in the 90's; the third, a humid area with native herbaceous vegetation
Our study showed that the forest edge, with the Asteraceae standing out as pioneer species, was characterized by an increase in the number of species typical of open areas (GUIDINI et al, 2014)
Summary
The overall forest cover by the subtropical forests with Araucaria has been drastically reduced over the last hundred years, making them one of the most threatened forest formations in Brazil. This forest type, called the Mixed Ombrophilous Forest (MOF) or Araucaria Forest, is characterized by the presence of tropical Afro-Brazilian and austral-antarctic Andean elements, with multiple plant species associations in various stages of succession. The forest canopy is made conspicuous by the tree species Araucaria angustifolia (Bertol.) Kuntze (LEITE, 2002). The Santa Catarina Forest and Floristic Inventory (IFFSC) estimates that the remaining MOF forest in this state represents only 22% of the original cover (VIBRANS et al, 2013).
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