INFLUENCE OF SOIL AND TOPOGRAPHY ON THE COMPOSITION OF A TREE COMMUNITY IN A CENTRAL BRAZILIAN VALLEY FOREST

Abstract

The purpose of the present study was to investigate the correlations between environmental variables related to the substrate (soil and topography) and the distribution of tree species in a valley forest in the Chapada dos Guimarães National Park, Mato Grosso State, Brazil. The forest lies in the Cerrado Domain of Central Brazil where the dominant vegetation cover is cerrado (woody savanna). A survey of the tree community registered all live individuals with circumference at breast height (cbh)≥15cm found in eighteen 600m2 plots (total area 1.08ha). The substrate variables used in the gradient analyses were obtained from a topographic survey and from analyses of the chemical and physical properties of soil samples. A principal components analysis of soil and topography variables and a canonical correspondence analysis of the species–environment relationships produced similar results, separating both the substrate variables and the tree species abundances, mainly according to the two types of bedrock, sandstone or slate, underlying their soils, and secondly to the three topographic sectors recognized: Streamside, Mid Slope and Upper Slope. The differences in soil fertility and texture (related to the bedrocks) and the soil water regime (related to both soil texture and topography) were probably the chief factors determining the distribution of tree species in the forest.