Abstract
Abstract: Local and regional environmental variations lead to different species composition, creating transitional areas. An example is the Araucaria and Seasonal forest in southern Brazil. Our objectives were (1) to describe the tree community structure and composition of a subtropical forest in southern Brazil and (2) to compare the floristic relationships between two forest typologies (Araucaria and Seasonal forest) in order to characterize the study area and the distribution patterns of tree species. We conducted a survey at Chapecó National Forest (in southern Brazil) in an area of 1.2 ha, where all individuals ≥ 30 cm of circumference at breast height were sampled. Community structure was described using the traditional phytosociological parameters. The floristic relationships were obtained by comparing our results with compiled data from other scientific papers through cluster analyses using an unweighted average linkage method, based on Jaccard similarity coefficient. We sampled 809 individuals belonging to 61 species and 28 families. The richest family was Fabaceae and Coussarea contracta (Walp.) Müll.Arg. was the most abundant species. Taxonomic diversity was 3.06 and the evenness was 0.74. The floristic similarity revealed that species composition of our study area is more similar to Seasonal forest. Species composition is related to environmental factors such as great thermal amplitude and seasonality. This subtropical forest is well structured, highly diverse and extremely important for the local and regional biodiversity conservation.
Highlights
The community species composition results from processes that rule the assemblages
We considered the concept of Atlantic Forest s.l., including the forest physiognomies (Oliveira-Filho & Fontes 2000)
The results obtained from the inventory for Araucaria forest (AF) and Seasonal forest (SF) were summarized by Gasper, Uhlmann, et al (2013) and Gasper, Sevegnani, et al (2013) where they recorded 366 and 204 tree species, respectively
Summary
The community species composition results from processes that rule the assemblages. In general, the processes are related to neutral models (Hubbell 2001), niche-based models (Cornwell & Ackerly 2009) or both, in different scales (Xu et al 2017). The environmental characteristics can vary along the extent of an area, creating some special conditions to the development and occurrence of a set of species. Factors such as soil composition, rainfall patterns, latitudinal and altitudinal ranges lead to floristic differentiations (Liebsch et al 2008). These variations create gradients (or ecotones), known as transitional areas with great biodiversity, especially because of the overlap of different physiognomies (Risser 1995). Studies in these areas are mainly in the transition of forested and non-forested areas (Junyan et al 2014), and the forest-forest dynamics is poorly documented, especially because of the gaps in knowledge about the capacity of rearrangement of species distribution (Oliveira-Filho et al 2014)
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