Predicting patterns of post‐fire germination in 35 eastern Australian Fabaceae

Auld, Tony D.; O’Connell, Michael

doi:10.1111/j.1442-9993.1991.tb01481.x

Cited by 304 publications

(342 citation statements)

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“…Several studies in agricultural systems found that the hard seeds of clover, Trifolium subterraneum, softened in response to daily temperature regimes between 30 and 60 C, if treated for several weeks or months (Hagon 1971;Taylor 1981). Auld and O'Connell (1991) observed that many leguminous species from south-eastern Australia had their physical dormancy broken to varying degrees by temperatures experienced during fire. The most important factor breaking dormancy was temperature, with a few species reaching significant germination levels after treatment at 40 and 60 C, but most reaching their maximum germination after treatment at 80À100 C. The duration of exposure did not significantly change the effect on dormancy, however, it should be noted that temperatures maintained in the soil during fire are short and exposure duration was tested over a scale of only minutes (Bradstock and Auld 1995).…”

Section: Discussionmentioning

confidence: 99%

“…These species are characterised by having soil-stored seed banks and by having seeds with physical dormancy which is broken by heat (Auld and O'Connell 1991;Ooi 2007 The direct effects of fire in breaking physical dormancy of most of our study species have been previously studied in laboratory experiments by Auld and O'Connell (1991). The most important factor breaking dormancy was temperature, whereas the time of exposure had variable effects (1-120 min).…”

Section: Methodsmentioning

confidence: 99%

“…Auld and Bradstock (1996) found that the soil temperatures exceeded 40 C in burnt areas over summer, down to a depth of 4.5 cm, with the highest temperatures of above 60 C recorded near the soil surface, at 0.4-cm depth. Thus, temperatures reached after the passage of a fire may in some cases exceed the thresholds for breaking physical seed dormancy of the study species (Auld and O'Connell 1991). In contrast, soil temperatures after a winter fire or in unburned vegetation during summer did not rise above 40 C. Thus, we simulated daily temperature regimes using approximate summer conditions from three different depths down the soil profile.…”

Section: Methodsmentioning

confidence: 99%

“…Heat and smoke released during the passage of fire are considered to be the most important fire cues that break dormancy or promote germination in soil-stored seeds. Temperatures reached during the passage of fire can break physical dormancy of hard-coated seeds, allowing subsequent water imbibition and germination when environmental conditions are suitable (Auld and O'Connell 1991;Keeley 1991;Cocks and Stock 1997;Bell 1999). In addition, smoke can also affect the physiology of seeds and directly stimulate germination (Brown 1993;Dixon et al 1995;Keeley and Fotheringham 1998;Van Staden et al 2000;Moreira et al 2010) or act in combination with heat (Keeley 1991;Keith 1997;Morris 2000;Thomas et al 2003).…”

Section: Introductionmentioning

confidence: 99%

“…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).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2010

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M. (2010). Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species. Australian Journal of Botany, 58 (7), 539-545.Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species AbstractIn addition to direct fire cues such as heat, smoke and charred wood, the passage of fire leads indirectly to changes in environmental conditions which may be able to break physical dormancy in hard-coated seeds. After a fire, the open canopy and the burnt material lying on the surface alter the thermal properties of the soil, resulting in elevated soil temperatures for long periods of time. We simulated daily temperature regimes experienced at different depths of soil profile after a summer fire. Our aim was to determine whether these temperature regimes and the duration of exposure (5, 15 and 30 days) play an important role breaking physical seed dormancy in six legumes from south-eastern Australia. Our results showed that simulated temperature regimes break seed dormancy. This effect is specially pronounced at temperatures that are expected to occur near the soil surface (0-2 cm depth). The duration of exposure interacts with temperature to break dormancy, with the highest germination rates reached after the longest duration and highest temperatures. However, the germination response varied among species. Therefore, this indirect post-fire cue could play a role in the regeneration of plant communities, and could stimulate seedling emergence independent of direct fire cues as well as in interaction with direct cues. © 2010 CSIRO. Abstract. In addition to direct fire cues such as heat, smoke and charred wood, the passage of fire leads indirectly to changes in environmental conditions which may be able to break physical dormancy in hard-coated seeds. After a fire, the open canopy and the burnt material lying on the surface alter the thermal properties of the soil, resulting in elevated soil temperatures for long periods of time. We simulated daily temperature regimes experienced at different depths of soil profile after a summer fire. Our aim was to determine whether these temperature regimes and the duration of exposure (5, 15 and 30 days) play an important role breaking physical seed dormancy in six legumes from south-eastern Australia. Our results showed that simulated temperature regimes break seed dormancy. This effect is specially pronounced at temperatures that are expected to occur near the soil surface (0-2 cm depth). The duration of exposure interacts with temperature to break dormancy, with the highest germination rates reached after the longest duration and highest temperatures. However, the germination response varied among species. Therefore, this indirect post-fire cue could play a role in the regeneration of plant communities, and could stimulate seedling emergence independent of direct fire cues as well as in interaction with direct cues.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2010

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Temperature thresholds of physically dormant seeds and plant functional response to fire: variation among species and relative impact of climate change

Ooi

Denham

Santana

et al. 2014

Ecology and Evolution

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Variation in dormancy thresholds among species is rarely studied but may provide a basis to better understand the mechanisms controlling population persistence. Incorporating dormancy-breaking temperature thresholds into existing trait frameworks could improve predictions regarding seed bank persistence, and subsequently species resilience in response to fire, climate change and anthropogenic management. A key ecological strategy for many species from fire-prone ecosystems is the possession of a long-lived seed bank, ensuring recovery after fire. Physical dormancy is dominant in these ecosystems and maintaining this dormancy is directly linked to seed bank persistence. We identified a suite of seed-related factors relevant to maintaining populations in fire-prone regions for 14 co-occurring physically dormant species. We measured variation in initial levels of dormancy and then applied experimental heating treatments, based on current seasonal temperatures and those occurring during fires, to seeds of all study species. Additionally, higher seasonal temperature treatments were applied to assess response of seeds to temperatures projected under future climate scenarios. Levels of germination response and mortality were determined to assess how tightly germination response was bound to either fire or seasonal cues. Six species were found to have dormancy cues bound to temperatures that only occur during fires (80°C and above) and were grouped as having obligate pyrogenic dormancy release. The remaining species, classified as having facultative pyrogenic dormancy, had lower temperature dormancy thresholds and committed at least 30% of seeds to germinate after summer-temperature treatments. Evidence from this study supports including dormancy-breaking temperature thresholds as an attribute for identifying functional types. High temperature thresholds for breaking dormancy, found in our obligate pyrogenic group, appear to be a fire-adapted trait, while we predict that species in the facultative group are most at risk to increased seed bank decay resulting from elevated soil temperatures under projected climate change.

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Seedling performance covaries with dormancy thresholds: maintaining cryptic seed heteromorphism in a fire‐prone system

Liyanage

Ayre

Ooi

2016

Ecology

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Abstract. The production of morphologically different seeds or fruits by the same individual plant is known as seed heteromorphism. Such variation is expected to be selected for in disturbance-prone environments to allow germination into inherently variable regeneration niches. However, there are few demonstrations that heteromorphic seed characteristics should be favored by selection or how they may be maintained. In fire-prone ecosystems, seed heteromorphism is found in the temperatures needed to break physical dormancy, with seeds responding to high or low temperatures, ensuring emergence under variable fire-regime-related soil heating. Because of the relationship between dormancy-breaking temperature thresholds and fire severity, we hypothesize that different post-fire resource conditions have selected for covarying seedling traits, which contribute to maintenance of such heteromorphism. Seeds with low thresholds emerge into competitive conditions, either after low-severity fire or in vegetation gaps, and are therefore likely to experience selection for seedling characteristics that make them good competitors. On the other hand, high-temperature-threshold seeds would emerge into less competitive environments, indicative of stand-clearing high-severity fires, and would not experience the same selective forces. We identified high and low-threshold seed morphs via dormancy-breaking heat treatments and germination trials for two study species and compared seed mass and other morphological characteristics between morphs. We then grew seedlings from the two different morphs, with and without competition, and measured growth and biomass allocation as indicators of seedling performance. Seedlings from lowthreshold seeds of both species performed better than their high-threshold counterparts, growing more quickly under competitive conditions, confirming that different performance can result from this seed characteristic. Seed mass or appearance did not differ between morphs, indicating that dormancy-breaking temperature threshold variation is a form of cryptic heteromorphism. The potential shown for the selective influence of different post-fire environmental conditions on seedling performance provides evidence of a mechanism for the maintenance of heteromorphic variation in dormancy-breaking temperature thresholds.

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Predicting patterns of post‐fire germination in 35 eastern Australian Fabaceae

Cited by 304 publications

References 20 publications

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

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

Temperature thresholds of physically dormant seeds and plant functional response to fire: variation among species and relative impact of climate change

Seedling performance covaries with dormancy thresholds: maintaining cryptic seed heteromorphism in a fire‐prone system

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