Rising [CO] changes competition relationships between native woody and alien herbaceous Cerrado species.

The structure of the Cerrado may be explained by the competition between woody and herbaceous species. However, the rising CO2 concentration ([CO2]) predicted under current climatic change may modify the ecophysiological responses of woody and herbaceous species owing to functional traits of each group, which may in turn modify vegetation structure as competitive relationships change among species. In this study we examined ecophysiological responses and competition between two cerrado species under elevated [CO2]. We selected an herbaceous alien grass (Melinis minutiflora P. Beauv.) and an endemic woody cerrado species (Hymenaea stigonocarpa Mart. ex Hayne). Hymenaea stigonocarpa individuals were maintained in three plots with different M. minutiflora densities: 0, 50 and 100% in two different [CO2] (380ppm and 700ppm) in open-top chambers. Leaf gas exchange, effective quantum efficiency of PSII, chlorophyll content, and growth increased in H. stigonocarpa plants under high [CO2]. The competition with M. minutiflora under elevated [CO2] led to an increase in specific leaf area, leaf area ratio and biomass allocation to shoots in H. stigonocarpa. In contrast, M. minutiflora had a delayed leaf development and high stem dry mass under elevated [CO2]. These changes in growth patterns under elevated [CO2] will modify allocation of resources, improving the competition potential of the woody species over the alien grass species in the Cerrado.