The effect of simulated heat-shock and daily temperature fluctuations on seed germination of four species from fire-prone ecosystems

Zupo, Talita; Baeza, M. Jaime; Fidelis, Alessandra

doi:10.1590/0102-33062016abb0246

Cited by 17 publications

(12 citation statements)

References 34 publications

(53 reference statements)

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“…S1), supporting the explanation of sensitivity cycling to physical dormancy breaking. Zupo et al 29 also found that seeds of C. albidus exposed to fire plus summer temperatures decreased germination in comparison to seeds only exposed to fire, but results were not explained. Probably, their results can also be explained in terms of sensitivity cycling.…”

Section: Discussionmentioning

confidence: 96%

“…The combined effect of heat shock and the typical high temperatures of the summer season is even more unknown than their isolated effects 17,21,29 . In Mediterranean habitats, seed dispersal occurs frequently during the summer, when seeds have to withstand the high soil temperatures before their germination in autumn or winter and eventual wildfire, which typically occurs during the summer in these areas.…”

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confidence: 99%

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RETRACTED ARTICLE: Fire and summer temperatures work together breaking physical seed dormancy

Luna

2020

Sci Rep

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Fire and high summer soil temperatures can break physical seed dormancy in Mediterranean fire-prone ecosystems. Their independent effect is somewhat recognized but both factors may act together with a synergistic effect yet unknown. This study aims to determine the isolated and combined effects of fire and summer temperatures on the release of physical seed dormancy in Cistaceae species. Fire and summer temperature treatments were applied in a factorial experiment to seeds of 12 species of Cistaceae. Seeds previously exposed or not to a heat shock (fire simulation) were kept for 1 or 2 months at constant or alternating temperatures (summer temperatures simulation). Additionally, I compared the effect of exposing the seeds to a heat shock before or after they had been subjected to the summer temperatures. Heat shock increased germination of all species, but summer temperatures produced different results. When seeds were exposed to summer temperatures after heat shock, germination decreased. This negative effect disappeared when heat shock was simulated at the end of the summer temperatures. Fire and summer temperatures modulate timing of germination in Cistaceae with a joint control on post-fire regeneration. Cycling of sensitivity to physical dormancy release may be the mechanism to explain this fine-tuning, which would ensure germination when environmental conditions are suitable for growth. These results contribute to our understanding of vegetation dynamics and postfire regeneration in Mediterranean ecosystems.

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Section: Discussionmentioning

confidence: 96%

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confidence: 99%

RETRACTED ARTICLE: Fire and summer temperatures work together breaking physical seed dormancy

Luna

2020

Sci Rep

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“…A particular gap in restoration research, little is known about the role of fire in the reproduction and establishment of savanna grassland plants. Initial studies on heat shock simulated in the laboratory suggest that fire does not break seed dormancy, stimulate germination, or kill the seeds (Le Stradic et al ., ; Fichino et al ., ; Zupo, Baeza & Fidelis, ), whereas in field experiments, although many seeds died, fire indirectly promoted germination of surviving seeds, by reducing vegetation cover, which increased soil surface temperature fluctuation (Daibes et al ., ). In a laboratory study of grasses of southern Africa, Ghebrehiwot et al .…”

Section: Restorationmentioning

confidence: 99%

Resilience and restoration of tropical and subtropical grasslands, savannas, and grassy woodlands

et al. 2018

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Despite growing recognition of the conservation values of grassy biomes, our understanding of how to maintain and restore biodiverse tropical grasslands (including savannas and open‐canopy grassy woodlands) remains limited. To incorporate grasslands into large‐scale restoration efforts, we synthesised existing ecological knowledge of tropical grassland resilience and approaches to plant community restoration. Tropical grassland plant communities are resilient to, and often dependent on, the endogenous disturbances with which they evolved – frequent fires and native megafaunal herbivory. In stark contrast, tropical grasslands are extremely vulnerable to human‐caused exogenous disturbances, particularly those that alter soils and destroy belowground biomass (e.g. tillage agriculture, surface mining); tropical grassland restoration after severe soil disturbances is expensive and rarely achieves management targets. Where grasslands have been degraded by altered disturbance regimes (e.g. fire exclusion), exotic plant invasions, or afforestation, restoration efforts can recreate vegetation structure (i.e. historical tree density and herbaceous ground cover), but species‐diverse plant communities, including endemic species, are slow to recover. Complicating plant‐community restoration efforts, many tropical grassland species, particularly those that invest in underground storage organs, are difficult to propagate and re‐establish. To guide restoration decisions, we draw on the old‐growth grassland concept, the novel ecosystem concept, and theory regarding tree cover along resource gradients in savannas to propose a conceptual framework that classifies tropical grasslands into three broad ecosystem states. These states are: (1) old‐growth grasslands (i.e. ancient, biodiverse grassy ecosystems), where management should focus on the maintenance of disturbance regimes; (2) hybrid grasslands, where restoration should emphasise a return towards the old‐growth state; and (3) novel ecosystems, where the magnitude of environmental change (i.e. a shift to an alternative ecosystem state) or the socioecological context preclude a return to historical conditions.

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“…Each replicate consisted of 20 seeds depending on seed availability (Supplementary Data Table S4). To avoid misinterpretation with soil temperature fluctuations, which reach up to 60 °C (Zupo et al, 2016;Daibes et al, 2017), lower temperatures were not tested. Therefore, we applied 100 °C as a typical fire-related heat dose (e.g.…”

Section: Heat Shocks and Germination Proceduresmentioning

confidence: 99%

Fire and legume germination in a tropical savanna: ecological and historical factors

et al. 2019

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Background and Aims In many flammable ecosystems, physically dormant seeds show dormancy-break patterns tied to fire, but the link between heat shock and germination in the tropical savannas of Africa and South America remains controversial. Seed heat tolerance is important, preventing seed mortality during fire passage, and is usually predicted by seed traits. This study investigated the role of fire frequency (ecological effects) and seed traits through phylogenetic comparison (historical effects), in determining post-fire germination and seed mortality in legume species of the Cerrado, a tropical savanna–forest mosaic. Methods Seeds of 46 legume species were collected from three vegetation types (grassy savannas, woody savannas and forests) with different fire frequencies. Heat shock experiments (100 °C for 1 min; 100 °C for 3 min; 200 °C for 1 min) were then performed, followed by germination and seed viability tests. Principal component analysis, generalized linear mixed models and phylogenetic comparisons were used in data analyses. Key Results Heat shocks had little effect on germination, but seed mortality was variable across treatments and species. Seed mortality was lowest under the 100 °C 1 min treatment, and significantly higher under 100 °C 3 min and 200 °C 1 min; larger seed mass decreased seed mortality, especially at 200 °C. Tree species in Detarioideae had the largest seeds and were unaffected by heat. Small-seeded species (mostly shrubs from grassy savannas) were relatively sensitive to the hottest treatment. Nevertheless, the presence of physical dormancy helped to avoid seed mortality in small-seeded species under the hottest treatment. Conclusions Physical dormancy-break is not tied to fire in the Cerrado mosaic. Heat tolerance appears in both forest and savanna species and is predicted by seed traits (seed mass and physical dormancy), which might have helped forest lineages to colonize the savannas. The results show seed fire responses are better explained by historical than ecological factors in the Cerrado, contrasting with different fire-prone ecosystems throughout the world.

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The effect of simulated heat-shock and daily temperature fluctuations on seed germination of four species from fire-prone ecosystems

Cited by 17 publications

References 34 publications

RETRACTED ARTICLE: Fire and summer temperatures work together breaking physical seed dormancy

RETRACTED ARTICLE: Fire and summer temperatures work together breaking physical seed dormancy

Resilience and restoration of tropical and subtropical grasslands, savannas, and grassy woodlands

Fire and legume germination in a tropical savanna: ecological and historical factors

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