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In South America, the largest area of tropical savanna is the Brazilian Cerrado biome, which encompasses a considerable range of environmental variation, with different types of soil, geology, geomorphology and climate, as well as distinct types of vegetation. These savannas include two types of vegetation: one on hilly slopes, with relatively shallow interspersed with rocky soils (RS), known as Rocky Cerrado, and the other located on flat terrain with deep soils (DS), known as Typical Cerrado. Our objective was to evaluate the effects of the heterogeneity of the chemical and granulometric properties of the soils on the composition and diversity of the shrubby-arboreal strata of the RS and DS. We found that, despite the reduced abundance of woody plants in the RS, and the physical limitations on plant development imposed by the rocky outcrops found in this environment, the RS is characterized by similar species diversity to that found in the DS. We present evidence of greater heterogeneity in the species composition and edaphic proprieties of the RS in comparison with the DS. We conclude that the greater variation and heterogeneity in the substrates of the RS accounts for the similarity in the species diversity between the RS and DS, although we suspect that other drivers, not investigated here, may also be involved. The intense conversion of native vegetation within the study region interferes with the establishment of exclusive species in RS (e.g., Norantea guianensis Aubl.) and DS (e.g., Couepia grandiflora (Mart. & Zucc.) Benth.) and consequently threatens the community structure of both environments with fundamental implications for the conservation.

We surveyed two savanna sites, one on fl at terrain with deep soil (DS), and the other on hilly terrain with rocky outcrops and shallow soil (RS), before and after an accidental fi re. We found that the fi re did not cause any signifi cant changes in the species composition or diversity of either community, and did not result in fl oristic homogenization. However, we did record a reduction in the density of plants and in basal area in the DS savanna in comparison with the RS savanna, as well as a higher rate of basal sprouting, which indicates a trade-off between mortality and sprouting. We conclude that, whereas post-fi re changes in vegetation structure were more pronounced in the DS savanna than in the RS, the diff erence in the underlying substrate did not have a direct infl uence on the post-fi re composition of woody species. Th e greater grass biomass found in the DS savanna in comparison with the RS savanna appears to have been the principal modulator of the severity of the fi res in the two phytophysionogmies, and accounts for the distinct responses to fi re we observed in the two woody communities.

Aims Different plant functional groups display diverging responses to the same environmental gradients. Here, we assess the effects of environmental and spatial predictors on species turnover of three functional groups of Brazilian savannas (Cerrado) plants—trees, palms and lianas—across the transition zone between the Cerrado and Amazon biomes in central Brazil. Methods We used edaphic, climatic and plant composition data from nine one-hectare plots to assess the effects of the environment and space on species turnover using a Redundancy Analysis and Generalized Dissimilarity Modeling (GDM), associated with variance partitioning. Important Findings We recorded 167 tree species, 5 palms and 4 liana species. Environmental variation was most important in explaining species turnover, relative to geographic distance, but the best predictors differed between functional groups: geographic distance and silt for lianas; silt for palms; geographic distance, temperature and elevation for trees. Geographic distances alone exerted little influence over species turnover for the three functional groups. The pure environmental variation explained most of the liana and palm turnover, while tree turnover was largely explained by the shared spatial and environmental contribution. The effects of geographic distance upon species turnover leveled off at about 300 km for trees, and 200 km for lianas, whereas they were unimportant for palm species turnover. Our results indicate that environmental factors that determine floristic composition and species turnover differ substantially between plant functional groups in savannas. Therefore, we recommend that studies that aim to investigate the role of environmental conditions in determining plant species turnover should examine plant functional groups separately.

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