Seed ecology of post-fire flowering species from the Cerrado

Abstract

Post-fire flowering (PFF) species resprout, flower and disperse seeds within weeks after fire. This may be an important strategy to recruit new individuals and colonize the gaps opened by fire. The seeds released in the post-fire environment may interact with byproducts derived from plant burning, and the resulting ash may have compounds that can promote the germination of various seeds, particularly those with permeable coats. In the Cerrado ecoregion, PFF is a strategy commonly observed in the species of the ground layer, but their seeds are rarely investigated. So, we examined the quality and the germination of the seeds of 13 species that disperse seeds within 3 months after fire. We estimated the amount of empty, filled and predated seeds for each species, and tested the germination with or without ash. There was a clear separation in seed quality as dicots produced 35–75% filled seeds but grasses <15%. Pre-dispersal predation was only observed for dicots (<10%). Ash stimulated the germination of two out of the three dormant species but inhibited the germination of three non-dormant species. Overall, the seeds produced in response to fire are an important source of genetic variability in an ecosystem that has resprouting as the main persistence strategy. As most species have non-dormant seeds, ash may only be important to stimulate the germination of few PFF species. Even so, ash can be completely washed away by rains before seeds are dispersed and may not have an effect under field conditions.

Elevation modulates the impacts of climate change on the Brazilian Cerrado flora

“…For instance, some typical Cerrado families, such as the Poaceae and Melastomataceae, display a suit of traits that limit propagule movement and establishment. These include fire‐triggered flowering (Fidelis & Zirondi, 2021; Fontenele & Miranda, 2022; Pilon et al., 2018; Zirondi et al., 2021), a high proportion of embryoless seeds (Fontenele et al., 2020; Kolb et al., 2016; Le Stradic et al., 2015) and seed dormancy (Dayrell et al., 2017; Escobar et al., 2018; Silveira et al., 2012). Second, several Cerrado plants are edaphic specialists and adapted to acidic, aluminium‐rich, phosphorus‐impoverished quartzite soils, typical of much of the Cerrado (Abrahão et al., 2019; Haridasan, 2008; Oliveira et al., 2015; Teodoro et al., 2019).…”

Beyond fire: Flower production naturally occurs and is also influenced by leaf removal in a Neotropical savanna herb

“…These post-fire conditions could be beneficial for seedling establishment. However, the few studies on the smoke and ash effects on the germination of Cerrado seeds show, in general, that smoke or ash alone does not stimulate germination [ 43 , 61 – 64 ]. Nevertheless, due to the fast recovery of the herbaceous layer biomass after the fire, mostly resprouts from underground organs [ 53 ], in 6 months the proportion of bare soil might decrease to circa 20% [ 53 , 65 ], increasing competition for light.…”

“…As B . paradoxa produces non-dormant seeds [ 64 ], after fires in the dry-wet season transition the time between blooming, stalks elongation, seed maturation, and dispersion may allow germination to occur when rainfall is more constant, thus avoiding root desiccation of the newly emerged seedling during the short dry spells at the onset of the rains.…”

What happens when fire is too early? Observations of fire‐stimulated fruit opening releasing underdeveloped seeds for an endemic Cerrado shrub

“…These traits secure resprouting as the main regeneration strategy of the vegetation; hence obligate seeders are rare (Pilon et al, 2021; Zupo et al, 2021). Still, several resprouters also show post‐fire responses related to seedling recruitment in a strategy to benefit from the optimal establishment conditions created by fire (Coutinho, 1976; Fontenele & Miranda, 2022). For instance, fire‐stimulated flowering is a widespread trait in ground layer, particularly for the so‐called ‘post‐fire flowering species’ that resprout and produce seeds within weeks after fire (Fidelis & Zirondi, 2021; Pilon et al, 2018).…”

“…Particularly, many herbs and shrubs finish fruiting and begin dispersal in the first weeks of the dry season (Batalha et al, 1997; Munhoz & Felfili, 2007; Oliveira, 2008) and, therefore, fires in this period could compromise the reproduction of several species from various functional groups. Yet, this has been a neglected study topic as current seed ecology studies have focused on the post‐fire reproduction (stimuli or seed quality; Fidelis & Zirondi, 2021; Fontenele & Miranda, 2022; Pilon et al, 2018) or on already dispersed seeds (Daibes et al, 2022), but not on fruits developing at the moment of burns. With that in mind, we describe in this Natural History Note our observations of a fire‐stimulated fruit opening of an endemic Cerrado shrub that resulted in the release of immature seeds.…”