Savannas are built to burn: plant-trait evidence from the Cerrado

Fire has been present in savannas worldwide for millions of years, shaping vegetation structure and composition. Besides its importance as one of the major vegetation consumers, fire has been viewed as detrimental leading to zero-fire policies for many years in Brazil, leading to severe wildfires and bad fire management. This review aims to clarify why and how fires occur in open ecosystems (grasslands and savannas) of the Cerrado, using a trait-based approach to show how plants deal with recurring fire disturbance and the consequences of altering fire regimes.

Savannas are fire-prone ecosystems with a combination of woody species and a flammable grass layer that will burn when environmental conditions allow. Fires are of low-mid intensity/severity, spreading fast on the surface and consuming most of the aboveground herbaceous layer. Fuels are composed of mostly highly flammable C4 grasses, which grow during the rainy season, and cure during the dry season leading to perfect conditions for fuels to burn. However, plants in savannas, such as in the Cerrado domain, have strategies to cope with the recurrent aboveground removal in the post-fire environment because they have a set of fire-related traits, allowing them to persist. Plants can protect their meristematic tissues in underground organs and through thick bark aboveground. The immediate post-fire herbaceous layer of the Cerrado is colorful, with many species flowering and producing seeds that enter the seed bank and later return to the community through post-fire germination.

In addition to changes caused by climate change, human-induced alterations of fire regimes have been a central issue in the conservation of the Cerrado. Although plants of the Cerrado can cope well with frequent fires, novel fire regimes can impose new challenges that can compromise the persistence of Cerrado species in the post-fire environment. We highlight the need to improve our knowledge about how savannas will respond to changes in fire regimes led by changes in climate and intensified human activity.