Abstract In a climate change context, the buildup of CO2 will affect plant communities worldwide. This study evaluated the effects of CO2 enrichment on the development and defense of two Cerrado native species Baccharis dracunculifolia and B. platypoda and their associated endophytic fungi richness. The study took place in Open-Top Chambers, two with ambient CO2 concentration (~400 ppm) and two in an enriched environment (~800 ppm). Baccharis platypoda developed 20% more leaves under enriched CO2 conditions, whereas B. dracunculifolia was 30% taller and showed 27% more leaves than those under ambient conditions. In both species, leaf polyphenol concentration did not differ between treatments. Nevertheless, polyphenol content had a positive correlation with plant height on both species’ individuals grown under CO2 enriched conditions. Endophytic fungi richness and colonization rate on both plant species did not differ between ambient and enriched conditions. Our results show the positive effect of CO2 fertilizer in at least one of the measured growth parameters. An important new finding was a synergistic increase in growth and chemical defense in both studied species under enriched CO2 conditions, suggesting higher carbon assimilation and accumulation. This study suggests that the effects on primary productivity and secondary metabolites of Baccharis species will potentially reflect on the diversity and distribution of Cerrado plants and their associated animal communities.

ABSTRACT Rupestrian landscapes are characterized by vegetation mosaics comprised of different plant communities and strongly linked to environmental filters. These environments are nutrient-impoverished, and possess water retention deficits and high solar exposure. This study aimed to determine whether chemical properties of the soil shape the arboreal-shrub vegetation structure in two neighboring habitats; a rupestrian cerrado and a rupestrian grassland. We hypothesized that the habitat with higher soil chemical properties would have higher parameters for vegetation structure, and different species composition. We expected higher chemical properties of the soil to favor a greater variety of plant life-forms. A total of 1349 individuals of 85 species belonging to 24 families were recorded; 1141 individuals (65 species) in the rupestrian cerrado, and 208 individuals (20 species) in the rupestrian grassland. Overall, Asteraceae, Fabaceae and Melastomataceae had greater species richness in both areas. Both habitats floristic composition was strongly influenced by differences in soil chemistry. In the cerrado, species richness, composition, soil nutrient availability and acidity were greater than in the grassland. We demonstrated that variation in soil chemistry influences plant species richness and composition, and structural complexity of vegetation, in both contiguous rupestrian environments, and that soil chemistry heterogeneity yields different plant life-form strategies.