Palavras-chave: Cadeia do Espinhaço, campos ferruginosos, campos quartzíticos, canga, Quadrilátero Ferrífero

(Phytosociology of quartzitic and ferruginous rocky outcrop areas in the Quadrilatero Ferrifero, Minas Gerais). Th e fl oristic composition and phytosociological structure of two areas with quartzitic and ferruginous (itabiritic) campos rupestres in the Quadrilatero Ferrifero region of Minas Gerais state were studied. Th e aim of this research was to determine if geology and geomorphology infl uence the vegetation of these communities. Th e campos rupestres in both lithologies were stratifi ed in three kinds of geomorphologic/phytophysionomic habitats: 1. Slopes with grasslands; 2. Plateaus with grasslands and 3. Lower slopes with woody savannas. In each habitat, 10 plots (10x10m) were randomly defi ned, totaling 60 plots. Frequency, dominance and importance value (IV) parameters were calculated for each species. Shannon-Wiener (H’) and Pielou (J’) indexes were estimated for each habitat. Jaccard index and clustering analysis were used to assess the fl oristic similarity of the diff erent habitats. Th ere were 165 species in the quartzitic and 160 in the ferruginous grasslands. Vellozia compacta was the species with the highest IV in both ferruginous grasslands. Lagenocarpus rigidus was the species with the highest IV in quartzitic sloped areas, followed by several phanerophytes. Echinolaena infl exa was the species with the highest IV in quartzitic plateaus followed by several phanerophytes and many hemicryptophytic species. Th e woody savannas in ferruginous areas were dominated by E. erythropappus and V. compacta, while in quartzitic areas by Echinolaena infl exa, Eremanthus erythropappus and many phanerophytic species. Woody savannas were more diverse than grasslands. Ferruginous campos rupestres exhibited lower diversity (H’=2.92) and equitability (J’=0.58) than quartzitic ones (H’=3.36; J’=0.66). Cluster analysis produced groups corresponding to the lithological and geomorphological habitats. Th e results give evidence that geology and geomorphology infl uence the fl oristic composition of campos rupestres.