Fire seasonality drives flowering patterns in the Campo Rupestre: implications for sempre-vivas management

Fire is an ecological force in the Campo Rupestre, affecting species composition, reproductive success and resource availability, while the season of fire can lead to divergent outcomes. We investigate how early-dry (May) and late-dry (September) prescribed fires affect flowering patterns in dry-flower species (sempre-vivas: Eriocaulaceae, Xyridaceae) and graminoids (Poaceae, Cyperaceae).

We established plots in burned and unburned areas under early-dry and late-dry fire treatments, and monitored the richness of species flowering and flower abundance over 22 months. Using linear mixed models, we tested the effects of fire occurrence, time since fire, and fire severity on flowering responses of target plant groups.

Fire season influenced the flowering patterns of dry-flower species, with species responding according to their phenology. Early-dry fire enhanced both the richness of flowering species (60% more flowering dry-flowers in July/2020) and flower abundance (92% higher dry-flower abundance in April/2020); late-dry fire also increased flower abundance but limited to fewer species. For graminoids, the richness of species flowering was not influenced by fire but was instead driven by seasonal patterns; flower abundance was slightly stimulated by early fire and phenological response. Fire residence times did not affect flowering, indicating that these heat levels were not detrimental to the plants.

Our findings show the importance of fire seasonality in shaping reproductive dynamics in the Campo Rupestre. While fire consistently stimulated flowering in dry-flower species, the magnitude and extent of the response were influenced by the burning season. Particularly, the early-dry fire suggested a positive role in supporting flowering across multiple species while also reducing the risk of wildfires. Whereas, late-fire exerted a pronounced influence on floral abundance. To refine these findings, long-term studies should evaluate the effects of repeated burns under different fire regimes, aiming to integrate ecological and traditional knowledge in fire management.