Physiological approaches to determine the impact of climate changes on invasive African grasses in the savanna ecoregion of Brazil

According to IPCC predictions for 2100, increasing CO₂ concentrations and global mean temperature could lead to a future scenario of increased incidence and duration of periods with exceptionally high temperatures and duration of drier seasons in some locations like Central Brazil. This extreme weather can affect fragile environments which are already suffering from anthropogenic disturbance that eventually culminate in biological invasions. One of these environments is the Brazilian Savanna (Cerrado), a biome with high levels of endemism, being considered an extremely important area for conservation. The present study aimed to investigate whether elevated CO₂ and temperature could modify protoplasmic tolerance to induced water deficit and acute heat shock in three species of invasive African grasses that are gradually replacing the Cerrado landscape. Results obtained from leaf tissues showed that elevated CO₂ and temperature had no effect on protoplasmic tolerances of Urochloa brizantha and that Megathyrsus maximus showed decreased thermotolerance. Urochloa decumbens showed improved tolerance responses to both types of these constraints undergone in vitro. Such adaptations to climate changes would probably represent an advantage in competition with other species. The results indicate that elevated CO₂ and temperature could cause modifications to protoplasmic responses of invasive grasses. The effects caused, however, depend on the species investigated. This ability to adapt or not to a changing environment may affect species distribution in natural and anthropized environments, especially in a future with predicted extreme weather.