The stress-dominance hypothesis postulates that the importance of competition in plant communities declines with increasing environmental stress while the importance of environmental filters increases. To test this hypothesis for campo rupestre vegetation, we analyzed phylogenetic diversity and community structure of angiosperm communities at two study sites within the Itacolomi State Park, Minas Gerais, Brazil. Plots representing more favorable habitats, such as those with a higher percentage of rocky outcrops that might permit the tapping of deeper water and nutrient resources as well as higher contents of clay and loam thereby increasing water and nutrient availability, show higher phylogenetic diversity and therefore lower phylogenetic clustering than plots with more sever habitats. This observation is consistent with the stress-dominance hypothesis if we assume ecological niches to be conserved within evolutionary niches. However, more comprehensive studies including tests for phylogenetic signal of ecological niches are necessary before generalizations for larger regions may be carried out.

Este trabalho foi conduzido na Floresta Nacional de Paraopeba. O objetivo desse estudo foi classificar e avaliar o solo, assim como verificar a influência dos atributos do mesmo na vegetação. Para isso, foram também testadas as seguintes hipóteses: 1) nas áreas de Cerradão a fertilidade é mais alta e os teores de alumínio são mais baixos; 2) os cerrados stricto sensu ocorrem nas áreas com altos teores de Al3+. Para isso, os solos da FLONA foram mapeados e identificados, além da análise química e física dos solos de cinco perfis. O gradiente ambiental foi facilmente observado pela análise de componentes principais (PCA), onde as diferenças entres as áreas foram evidenciadas. A correlação de Spearman foi usada para verificar as hipóteses. A relação entre vegetação (área basal, densidade e riqueza) e solo (K, Ca2+, e Al3+) foi estatisticamente significante. As hipóteses foram aceitas, porém a hipótese 1 apenas parcialmente. As características do solo parecem ter uma influência nas fitofisionomias do Cerrado e também em sua estrutura. O fósforo disponível foi um importante fator para a manutenção da fisionomia de Cerradão, assim como o Al3+ que parece ter um papel importante no estabelecimento de diferentes fisionomias de Cerrado.

This study was carried out in Paraopeba National Reserve. It aims to classify and evaluate the soil of the studied area and to verify the influence of soil attributes on vegetation by testing the following hypotheses: 1) under woodland physiognomies (Cerradão) the soil fertility is higher and the Al content lower; 2) open savanna occurs only in areas with high Al contents. For this purpose, representative soils in the Paraopeba National Reserve were mapped, identified, and samples from five profiles were analyzed. The environmental gradient was easily observed by principal components analyses, where the differences between the sites were highlighted. The Spearman correlation was used to verify the hypothesis. The correlation between vegetation (basal area, density, and richness) and soil (K, Ca2+, and Al3+) was statistically significant. The hypotheses were accepted, but hypothesis 1 only partially. Soil features seem to have an influence on the Cerrado phytophysiognomies and structure. Available phosphorous was an important factor for the maintenance of woodland Cerrado. Also, exchangeable Al3+ plays a major role in the establishment of different Cerrado physiognomies in Paraopeba National Reserve.