Fire-triggered flowering is the dominant post-fire strategy in a tropical savanna

Heloiza L. Zirondi, Mark K. J. Ooi & Alessandra Fidelis

In many vegetation types across the globe where fire is present, plants have adaptations to the fire regime to survive and reproduce. In many cases, plants bear thick barks and protected meristems. In addition, they can have fast responses after fire, which includes fast resprouting and stimulation and/or increase of flowering.

In the Cerrado, the neotropical species-rich savanna in Brazil, fire has been present for at least four million years. Although massive post-fire flowering (PFF) events were observed for the Mediterranean vegetation, there are surprisingly few published studies about how prevalent PFF is at the community level in savannas. Therefore, our aim was to understand how fire affects the flowering of Cerrado plant species compared to plants of a fire-excluded area. We established six plots, three recently and frequently burned (FB) and three excluded from fire for six years (E) in a Cerrado area in central Brazil. In all treatments, the number of species flowering and fruiting was counted every 15 days for three months, and then at six, nine and 12 months after fire. We also counted the number of reproductive and vegetative shoots in 10 subplots (1 m × 1 m) per plot. The results showed that more than 60% of the species – including shrubs, forbs, and graminoids – had their flowering stimulated by fire. Some of these species flowered faster in burned areas, while some species can be seen flowering only after fire (e.g. Lippia horridula). Another astonishing result is that these stimuli occurred in the middle of the dry season, three months before it began to rain.

Finally, at the local scale, quantifying the effects of fire is of extreme importance to understand how plant communities respond and regenerate after fire and give support to local managers to protect the biodiversity of these systems. Our study has broadened this understanding, hopefully allowing further insights into the relative importance of fire persistence strategies in the Cerrado, such as resprouting and PFF, and providing a basis for future comparison with other savanna systems.

This is a plain language summary for the paper of Zirondi et al. published in the Journal of Vegetation Science (https://doi.org/10.1111/jvs.12995). The blog post was prepared by Heloiza L. Zirondi.