Relationships between structure of the tree component and environmental variables in a subtropical seasonal forest in the upper Uruguay River valley, Brazil

Máida Ariane De Mélo,Jean Carlos Budke,Carlos Henke-Oliveira

doi:10.1590/s0102-33062013000400015

Abstract

This study aimed to analyze relationships among the structure of the tree component, edaphic variables and canopy discontinuity along a toposequence in a seasonal upland (hillside) forest in southern Brazil. Soil and vegetation were sampled in 25 plots of 20 × 20 m each. We described the vegetation in terms of structure, richness and diversity, as well as by species distribution patterns. We evaluated canopy continuity, determined sloping and calculated spatial coordinates. We applied partial canonical correspondence analysis (pCCA) to determine whether species distribution correlated with environmental and spatial variables. We identified 1201 individuals belonging to 76 species within 30 families. The species with highest density and frequency were Gymnanthes concolor Spreng., Calyptranthes tricona D.Legrand, Eugenia moraviana O.Berg and Trichilia claussenii DC. The pCCAs indicated significant correlations with environmental and spatial variables. Sand content, boron content and soil density collectively explained 36.17% of the species matrix variation (total inertia), whereas the spatial variables x, y and xy2 collectively explained 14.27%. The interaction between environmental and spatial variables explained nearly 4.5%. However, 45.05% remained unexplained, attributed to stochastic variation or unmeasured variables. Terrain morphology and canopy discontinuity had no apparent influence on richness, and changes in species distribution were correlated with sloping, which affects soil features and determines the directional distribution of some species.

Highlights

Many studies in ecology aim to understand the rules of ecological assemblages of natural communities at different scales
Several studies have demonstrated the importance of the topography and patterns that occur in areas with a sloping landscape—the flow of nutrients and water from the top to the base and its influence on the chemical and physical properties of the soil (Neary et al 2009), as well as the interaction between vegetation and light incidence—which can lead to differences in the composition of tree communities and the distribution of many tree species (Clark et al 1996)
For the family Fabaceae, in the seasonal forest along the upper Uruguay River, the richness and abundance of individuals are attributed mainly to the geographical location, which coincides with the entrance corridor of seasonal species in Rio Grande do Sul, as opposed to the Atlantic corridor species, which occur in the rain forest region to the east (Rambo 1961; Jarenkow & Waechter 2001)

Summary

Introduction

Many studies in ecology aim to understand the rules of ecological assemblages of natural communities at different scales. The landscape influences various environmental characteristics, such as light intensity, the distribution of nutrients and the water saturation of the soil (van den Berg & Santos 2003), and may act indirectly on the distribution of species (Budke et al 2010), especially in areas with steep inclines In this regard, several studies have demonstrated the importance of the topography and patterns that occur in areas with a sloping landscape—the flow of nutrients and water from the top to the base and its influence on the chemical and physical properties of the soil (Neary et al 2009), as well as the interaction between vegetation and light incidence—which can lead to differences in the composition of tree communities and the distribution of many tree species (Clark et al 1996).

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Conclusion