How do plants survive in the starving, burning, and hiding vegetation realms generated by novel fire regimes?

Abstract

Fire has been an important evolutionary force across many vegetation types worldwide, but human activities and climate change currently impose novel and unprecedented fire regimes. In some areas, fire is and will be excluded, while in others, fire activity will be increased either in intensity or frequency. Changes resulting in fire exclusion should create novel environments where competition for light dominates (starving realm), filtering out species with the costliest adaptations against fire. In areas where fire intensity will increase, fire should filter out species with aboveground parts exposed to the strongest impacts of the flames (hiding realm). Areas exposed to higher fire frequencies should promote species capable of quickly building protection between fire events (burning realm). Based on well-investigated savanna-forest mosaics in the Cerrado, we propose a set of plant adaptations and strategies that should be favoured or unfavored under different novel fire regimes. In the starving realm, species with the capacity to better explore vertical space and maintain competition for light with surrounding plants will likely be favored. In the hiding realm, species with strategies based on escaping flame exposure (for example belowground) will likely be favored. In the burning realm, species capable of shielding themselves from flames and quickly investing in aboveground protection in between fires should be favored. Finally, more than just promoting a collection of traits, novel fire regimes are expected to filter contrasting plants’ growth forms that perform better in fast vertical exploration, quick canopy expansion, or belowground strategies, imposing cascading consequences over vegetation structure and defining novel habitats for a wide range of organisms.