Tree species composition and similarity in semideciduous forest fragments of southeastern Brazil

This study investigates the influence of fragment size on tree species composition, speciesrichness and on individual groups of species within 11 semideciduous forest fragments insoutheastern Brazil. We compared same-sized samples of 500 trees from 10 fragments<100 ha, allocated to three size categories, with three 500-tree samples collected in differentareas within a large forest, used as a reference forest. The variation in species richness,in the proportion of species/individuals in dispersal modes, and in the proportion of rarespecies was not related to fragment size. Nonetheless, comparisons between the mean valuesof these variables of each fragment size categories, using 95% confidence intervals,showed a wider range of variation within the category of small-sized fragments than inthe other size categories. NMS ordination plot also suggested the absence of a relationshipbetween fragment area and tree species composition. However, multiple regressions usingthe scores from the NMS ordination as response variables, and area and disturbance intensitiesas predictor variables, suggested that the interaction of area and disturbance mightbe a good predictor of species composition. Pre-existing environmental heterogeneityand geographical proximity also appeared to play a role in the variations of forest compositionamong the fragments studied. Our results demonstrated the high conservation value of small forest fragments