Burning seeds: germinative response to heat treatments in relation to resprouting ability

Abstract

Summary 1.In Mediterranean fire-prone ecosystems, plant species persist and regenerate after fire by resprouting, by recruiting new individuals from a seed bank (post-fire seeding), or by both resprouting and post-fire seeding. Since species with resprouting ability are already able to persist in fire-prone ecosystems, we hypothesize that they have been subjected to lower evolutionary pressure to acquire traits allowing or enhancing post-fire recruitment. Consequently, we predict that the germination of non-resprouters is more likely to be increased or at least unaffected by heat than the germination of resprouters. 2. To test this hypothesis we compiled published experiments carried out in Mediterranean Basin species where seeds were exposed to different heat treatments. We compared the probability of heat-tolerant germination (i.e. heated seeds had greater or equal germination than the control), the probability of heat-stimulated germination (i.e. heated seeds had greater germination than the control) and the stimulation magnitude (differences in proportion of germination of the heated seeds in relation to the untreated seeds, for heat-stimulated treatments) between resprouters and non-resprouters. 3. Non-resprouters showed higher probability of heat-tolerance, higher probability of heatstimulation and higher stimulation magnitude even when phylogenetic relatedness was considered. Differences between life-forms and post-fire seeding ability do not explain this pattern. 4. Non-resprouters appear to have a greater capacity to both (i) persist after fire by means of recruiting (greater heat-tolerance) and (ii) increase their population after fire (greater heat-stimulated germination), than resprouters. 5. Synthesis . Our results contribute to understanding the factors that condition the evolution of fire-persistence plant traits and support the hypothesis that resprouting and post-fire recruitment are negatively associated in Mediterranean Basin flora.

Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species

“…In particular, the relationship between high but short-term temperature conditions experienced by seeds during fire have been tested, identifying optimal and lethal temperature thresholds for a range of species (e.g. Keeley 1987;Auld and O'Connell 1991;Baeza and Vallejo 2006;Paula and Pausas 2008;and references therein).…”

Habitat structure and host plant specialization drive taxonomic andfunctional composition of Heteroptera in postfire successional habitats

“…Although these plants were not found in the studied replicates, they are common in burnt sites: e.g., Cistus spp. have active postfire germination from the seed bank (Paula and Pausas, 2008), D. suffruticosum resprouts after fire (Rego et al, 1993), and many ferns survive as rhizomes are protected underground (Paula et al, 2009). Fire may create early successional habitats that attract species that specialize in that kind of habitat (Valentine et al, 2012).…”

Role of Fire in the Germination Ecology of Fountain Grass (Pennisetum setaceum), an Invasive African Bunchgrass in Hawai'i

“…Herbaceous plants have two primary modes for survival following the passage of fire; either they resprout from underground storage tissues or recruit new individuals from a seed bank (Pausas et al 2004, Paula andPausas 2008). During a fire, seeds may be killed unless protected by some kind of adaptation or by an insulating layer of soil (Baskin and Baskin 1989).…”

“…During a fire, seeds may be killed unless protected by some kind of adaptation or by an insulating layer of soil (Baskin and Baskin 1989). Protected seeds may either be stimulated to germinate or remain dormant or quiescent (Baskin andBaskin 1989, Paula andPausas 2008). Seeds can avoid the effects of fire through a number of mechanisms including burial in the soil either by animals or with the aid of hygroscopic awns (Ernst et al 1992).…”