Fire-Borne Life: A Brief Review of Smoke-Induced Germination

Abstract

Naturally occurring fires have been shaping landscapes long before mankind existed. Presumably, it is an early observation that in some habitats, fire is crucial to maintaining species diversity and for the rejuvenation of the vegetation, and so early settled farmers might have started to take advantage of the controlled burning of a desired area. The heat of fire is essential to break the dormancy of many fire ephemerals and for the seed release of some serotinous or woody taxa. Besides the physical effects caused by the heat on seeds, smoke and burnt organic material contain chemical cues that regulate the germination of seeds and the early development of seedlings. The scientific community really started to reveal the secrets of these enigmatic components from the early 1990s, although there are still a number of questions to be answered. In this review, we briefly introduce the path which leads to our current knowledge on smoke-derived compounds and their enormous effects on plant life.

Seed ecology of post-fire flowering species from the Cerrado

“…2). Compounds derived from plant burning may remain active in the upper layers of the soil for a few months after fire (Preston and Baldwin, 1999;Ghebrehiwot et al, 2011Ghebrehiwot et al, , 2013 and can stimulate the germination of permeable seeds (Van Staden et al, 2000;Nelson et al, 2012;Soós et al, 2019), being important to signalize gaps and adequate recruitment conditions (Jiménez-Alfaro et al, 2016). However, three nondormant species were inhibited by the treatment.…”

“…Smoke is shown to stimulate the germination of several fire-prone species (Keeley and Pausas, 2018), including some Cerrado grasses (Le Stradic et al, 2015;Ramos et al, 2019), shrubs (Zirondi et al, 2019) and post-fire flowerers (Fernandes et al, 2021). As the chemical cues persist in the soil for short periods after burning (Preston and Baldwin, 1999;Ghebrehiwot et al, 2011Ghebrehiwot et al, , 2013Soós et al, 2019), species that quickly resprout, flower and disperse seeds may benefit from them in an alternate mechanism of fire-stimulated germination coupled to fire-triggered flowering (Fernandes et al, 2021), increasing the recruitment potential. Ash, although not always considered in germination studies, could also have a positive effect on the germination of recently dispersed seeds due to the shared compounds with smoke and the likely higher concentration and close contact with seeds (Van Staden et al, 2000;Nelson et al, 2012;Soós et al, 2019).…”

“…The seeds released in the post-fire environment are prone to interacting with residues and compounds derived from plant burning (Nelson et al, 2012; Soós et al, 2019). Smoke and ash are the main chemical cues released by fire, sharing compounds that may promote germination particularly for seeds with permeable coats (Van Staden et al, 2000; Nelson et al, 2012; Soós et al, 2019).…”

“…The seeds released in the post-fire environment are prone to interacting with residues and compounds derived from plant burning (Nelson et al, 2012; Soós et al, 2019). Smoke and ash are the main chemical cues released by fire, sharing compounds that may promote germination particularly for seeds with permeable coats (Van Staden et al, 2000; Nelson et al, 2012; Soós et al, 2019). Smoke is shown to stimulate the germination of several fire-prone species (Keeley and Pausas, 2018), including some Cerrado grasses (Le Stradic et al, 2015; Ramos et al, 2019), shrubs (Zirondi et al, 2019) and post-fire flowerers (Fernandes et al, 2021).…”

“…As the chemical cues persist in the soil for short periods after burning (Preston and Baldwin, 1999; Ghebrehiwot et al, 2011, 2013; Soós et al, 2019), species that quickly resprout, flower and disperse seeds may benefit from them in an alternate mechanism of fire-stimulated germination coupled to fire-triggered flowering (Fernandes et al, 2021), increasing the recruitment potential. Ash, although not always considered in germination studies, could also have a positive effect on the germination of recently dispersed seeds due to the shared compounds with smoke and the likely higher concentration and close contact with seeds (Van Staden et al, 2000; Nelson et al, 2012; Soós et al, 2019). As PFF species have their reproduction tied to fire events, seeds have been in contact with this fire-cue along their evolutionary history, possibly resulting in ash-stimulated germination (Lamont and He, 2017).…”