The present study aimed at detecting the influence of both edge effects and space substrate-related variables on the structural variations of the tree community in a small (4.0 ha) forest fragment in Lavras, Minas Gerais state, SE Brazil. Trees with diameter at breast height (dbh) ≥ 5 cm were identified and measured in 29 (20 x 20 m), systematically distributed plots over the fragment. Substrate-related variables were obtained for each plot from the topography, laboratory analyses of soil samples and soil compaction measures. An 'edge factor' was calculated per plot from the fragment morphometry. Spatial variables were derived from the Cartesian coordinates of plot center. A canonical correspondence analysis of the species distribution abundance indicated significant correlations with some variables of the environmental and spatial matrices. The first ones were drainage classes, mean elevation, and saturation of bases, which explained 22.4% of the total variance. The spatial variables, x and x2*y, explained 12.7%, but the two sets shared, indistinctly, 4.6% of the total variance. Therefore, apart from the unexplained and stochastic variations (69.5%), the species distribution on the fragment is primarily influenced by spatial proximity, soil nutritional status and ground water regime.