Fire stimulates seedling recruitment from the seed bank in the Cerrado

Questions

Fire is an important ecological factor influencing plant communities in many fire-prone ecosystems. Savannas in the Cerrado are resilient to fire, with plants exhibiting fire-related traits, allowing them to persist in post-fire environments. Therefore, excluding fire may result in changes in plant community dynamics, thus affecting their resilience. We investigated the effect of the reintroduction of fire in savannas where fire has been excluded for longer periods (>12 years) on seedling recruitment. We asked the following questions: (i) how does fire affect seed bank germination in sites with different fire histories; and (ii) how did fire exclusion affect species composition of the seed bank?

Location

Estação Ecológica de Itirapina (EEI), Southeastern Brazil.

Methods

Two sites with different fire histories were selected: FE1985 – fire exclusion for more than 30 years, with one fire event in 1985; and FE2009 – fire exclusion for 12 years, with three fire events since 1985, the last one being in 2009. Both areas have low fire frequency, but different times since the last fire. Soil samples were collected before and after prescribed fires to evaluate the effects of fire after longer periods of fire exclusion in the soil seed bank. Using the seedling emergence method, we evaluate the effects of the reintroduction of fire after longer periods of fire exclusion in the soil seed bank.

Results

We found that fire significantly increased the seed bank recruitment at both sites, FE1985 and FE2009 (increase of 16% and 50% in seedling recruitment, respectively), showing that species of the Cerrado responded positively to the fire passage. The reintroduction of fire promoted different effects on seed bank recruitment: shrubs experienced a significant decrease in seedling emergence from the seed bank at FE1985, while their recruitment was not affected at FE2009. Time since last fire appears to influence the seed bank composition, showing a shift in dominance from a grassy community to a woody one.

Conclusions

After fire, more species germinated from the seed bank, showing that direct and indirect effects of fire are affecting seed germination from the seed bank, and its importance on seedling recruitment from the seed bank in the Cerrado.