Fire Cues Research Articles

Seed germination traits of desert perennials

While understanding that seed germination is crucial for ecological restoration activities, the seed traits of desert perennials are understudied. We experimentally determined germination traits of 43 species from 14 families from Hummock grasslands in the Great Sandy Desert, Australia. We defined morphological and physiological seed traits of framework species required for restoration and investigated the effects of fire and temperature on seed germination. We classified dormancy and explored the effect of Karrikinolide, a fire cue derived from smoke, on germination. Seeds of 38 (88%) out of 43 species were dormant: 13 (30%) with physical and 25 (58%) with physiological dormancy. Karrikinolide promoted seed germination of 9 (21%) species across all life-forms except trees, and widened the range of germination temperatures and increased germination rate of one species. Although high germination percentages were obtained over a wide temperature range, germination rate was affected by temperature. Non-dormant seeds and seeds pre-treated to overcome physical dormancy germinated quickly, with times to 50% germination of 1–5 days. Dormancy class differed between life-forms and families. Fast germination of non-dormant seeds is a trait that allows seeds to germinate during short periods of moisture availability. An absence of under-developed embryos is consistent with the global trends for hot deserts. A response to Karrikinolide shows that seed germination is related to a fire cue. These results will inform land managers of effective seed pre-treatments prior to seed broadcasting for restoration, and information on seed germination temperatures and rates will improve the understanding of when and where seeds could germinate in restored sites.

Postfire responses of the woody flora of Central Chile: Insights from a germination experiment.

Fire is a selective agent shaping plant traits and community assembly in fire-prone ecosystems. However, in ecosystems with no fire history, it can be a cause of land degradation when it is suddenly introduced by humans, as plant species may not be able to respond to such novel disturbance. Unlike other Mediterranean-type ecosystems (MTE) of the world, natural fires have not been frequent during the Quaternary in the matorral of Central Chile, and thus, plant adaptive responses are expected to be uncommon. We evaluated the effect of heat shock on seed survival and germination of 21 native woody plants of the Chilean matorral and compiled information on smoke-stimulation and resprouting, to evaluate the importance of fire-adaptive responses in the context of the other MTE. We found that in the Chilean woody flora negative seed responses to fire cues were more frequent than positive responses. Although resprouting is a relatively widespread trait, fire-stimulated germination is not as common in the Chilean matorral as in other MTE. The seeds of seven endemic species were strongly damaged by fire cues and this should be considered in post-fire restoration planning. However, our results also showed that many species were resistant to elevated doses of heat shock and in some, germination was even stimulated. Thus, future research should focus on the evolutionary causes of these responses. These findings could help to develop strategies for fire management in the Chilean matorral. In addition, they will improve our understanding of the evolutionary forces that shaped this plant community and to better frame this region among the other MTE worldwide.

Germination patterns of the scrublands in response to smoke: The role of functional groups and the effect of smoke treatment method

Smoke is thought to be one of the most important fire cues stimulating seed germination of species from both fire-prone and fire-free ecosystems. The impact of smoke on seed germination at the community level of certain habitats in Western Asia has not been investigated yet. We aimed to analyze the effects of different smoke treatments on soil seed germination of different plant functional groups in a scrubland habitat. A soil seed bank was used to count seedling emergence following aerosol smoke (15min or 30min exposure) or smoke-water (1:1000 and 1:500, v/v) treatment. Smoke-induced germination was then separated into five functional groups (i.e. annual grasses, perennial grasses, annual herbs, perennial herbs, and legumes). The results showed that seeds of annuals were stimulated with smoke. In contrast, germination of perennial grasses was reduced by the smoke treatments, whereas perennial forbs and legumes showed no particular response to the smoke treatments. The longer exposure time to the aerosol smoke (30min) and the higher concentration of smoke-water (1:500, v/v) were not at detrimental levels and resulted in maximum germination among the functional groups, other than perennial grasses. Our results indicate that smoke-stimulated germination of annuals plays an important role in species establishment after fire in the scrublands of Western Asia. Smoke treatments impacted differently on the different functional groups, and it is useful to determine the smoke response-classifications of these species to understand the effects of fires on the plant communities.

A new cue for torpor induction: charcoal, ash and smoke.

Recent work has shown that the use of torpor for energy conservation increases after forest fires in heterothermic mammals, probably in response to the reduction of food. However, the specific environmental cues for this increased torpor expression remain unknown. It is possible that smoke and the novel substrate of charcoal and ash act as signals for an impending period of starvation requiring torpor. We therefore tested the hypothesis that the combined cues of smoke, a charcoal/ash substrate and food shortage will enhance torpor expression in a small forest-dwelling marsupial, the yellow-footed antechinus (Antechinus flavipes), because like other animals that live in fire-prone habitats they must effectively respond to fires to ensure survival. Activity and body temperature patterns of individuals in outdoor aviaries were measured under natural environmental conditions. All individuals were strictly nocturnal, but diurnal activity was observed shortly after smoke exposure. Overall, torpor in females was longer and deeper than that in males. Interestingly, while both males and females increased daily torpor duration during food restriction by >2-fold as anticipated, a combination of food restriction and smoke exposure on a charcoal/ash substrate further increased daily torpor duration by ∼2-fold in both sexes. These data show that this combination of cues for torpor induction is stronger than food shortage on its own. Our study provides significant new information on how a small forest-dwelling mammal responds to fire cues during and immediately after a fire and identifies a new, not previously recognised, regulatory mechanism for thermal biology in mammals.

Germination ecology of the endangered species Asterolasia buxifolia (Rutaceae): smoke response depends on season and light

In fire-prone regions, many plant species rely on persistent seed banks for post-fire recovery. Understanding dormancy and germination cues is, therefore, important to predict population response. However, the germination ecology of species with physiologically dormant seeds in fire-prone regions is complex. We used the endangered species Asterolasia buxifolia, from riparian habitat in fire-prone south-eastern Australia, to investigate physiologically dormant seeds and their response to fire. We assessed whether fire cues alone promoted germination, or whether seasonal factors and light also played a role. Additionally, we tested the resilience of seeds to heat-shock temperatures produced in soil during fire, so as to identify potential factors that restrict such species to fire refugia. Seeds germinated only at winter seasonal temperatures, and had an obligate smoke and light requirement. Heat-shock treatments above 80°C slowed the germination rate. Smoke-related germination and the tolerance of A. buxifolia seeds to high fire-related temperatures demonstrated that recruitment dynamics can be driven by fire; however, germination is restricted to winter temperatures. This highlights the potential that changes to fire season may have on population persistence. The slow germination rate caused by heat, and a light requirement, may contribute to restricting this species to riparian habitat.

Heat and smoke pre‐treatment of seeds to improve restoration of an endangered Mediterranean climate vegetation type

AbstractInvasive alien plants impact ecosystems, which often necessitates their removal. Where indigenous species recovery fails following removal alone, an active intervention involving reintroduction of seed of native species may be needed. This study investigated the potential for a combination of the fire cues of smoke and heat as a pre‐treatment of seeds in breaking dormancy and facilitating increased germination. Species were selected to represent different functional types within Cape Flats Sand Fynbos; a fire‐prone, critically endangered vegetation type in South Africa. Seeds were exposed to either a heat pulse (temperatures between 60 and 300°C for durations of between 30 s and 20 min) or dry after‐ripening (1 or 2 months at milder temperatures of 45°C or less). Thereafter, seeds were soaked in smoke solution for 18 h and subsequently placed on agar at 10/20°C for germination. Most species fell into one of two main groups: Seed germination in the first group was greatest following a lower temperature (60°C) heat pulse, an extended period of mild temperature (20/40°C or 45°C) exposure, or no pre‐treatment with heat. Seed germination in the second group was promoted after brief exposure to higher (100°C) temperatures. No germination occurred in any species following heat treatments of 150°C or higher. Species which responded better to higher temperatures were mainly those possessing physical dormancy, but seed morphology did not correlate with germination success. This study showed that heat stimulation of seeds is more widespread in fynbos plant families than previously known and will enable the development of better seed pre‐treatment protocols before large‐scale sowing as an active restoration treatment after alien plant clearing.

Smoke and Ash Effects on Seedling Emergence from Germinable Soil Seed Bank in Fescue Prairie

Seedling recruitment plays a crucial role in recovering plant communities after disturbance. As a natural disturbance, fire can mediate species composition in fescue prairie. However, little was known about the effects of important fire cues on seedling recruitment in fescue prairie. Soil seed bank samples were taken from the top 5 cm of the soil profile and separated into litter, 0- to 1-cm, and 1- to 5-cm layers. Seedlings emerging from soil seed banks incubated in the greenhouse were examined after applying smoke, ash, and smoke plus ash in 2013 and 2014, to assess their effects on the density, richness, and composition of seedlings emerging from the soil seed bank in fescue prairie. Smoke plus ash significantly increased the number of Artemisia ludoviciana Nutt. seedlings emerging from 0- to 1-cm soil layer and Conyza canadensis (L.) Cronquist seedlings emerging from the litter layer (P < 0.05), while ash significantly increased the number of Artemisia frigida Willd. seedlings emerging from 0- to 1-cm soil layer (P < 0.05). Densities of total seedlings emerging from the 0- to 1-cm soil layer were increased by smoke plus ash in 2013 and by ash in 2014 (P < 0.05). Smoke plus ash and ash alone had more prominent effects on seedling density and richness of native forbs. Species composition was altered by ash in the 0- to 1-cm, 0- to 5-cm, and all layers combined in 2013 (P < 0.05). Direct fire cues appear to stimulate recruitment of some species, especially native forbs, contributing to potential changes in species composition of fescue prairie.

Micropylar seed coat restraint and embryonic response to heat shock and smoke control seed dormancy in Grevillea juniperina

AbstractSeeds of some eastern Australian Grevillea species show the characteristics of non-deep physiological dormancy, which is broken by exposure to heat shock and/or smoke. The current study tested whether the restrictive effect of the seed coat on germination was localized to specific regions, whether the fire cues affected the growth potential of the embryo, the mechanical strength of the seed coat itself, and the anatomy of fracturing of the seed coat. Removal of the micropylar seed coat allowed germination, while retaining it in place restricted germination. The growth potential of the embryo was increased by exposure to heat shock or to smoke, and increased the most if exposed to both cues. Estimation of the minimum force required by embryos to germinate from intact seeds suggested that this force was reduced for seeds treated with fire cues. The fire cues did not affect the resistance of the seed coat to compressive force when tested after 24 h of imbibition. Fracturing of the seed coat occurred between cell walls, except for the palisade layer, where fracturing occurred across palisade and sclerenchyma cells. While the micropylar end of the seed coat imposes dormancy, most likely by mechanical constraint, heat shock and smoke overcome dormancy by increasing the embryo's growth potential and possibly weakening the seed coat, either directly or via the embryo.

The Effect of Seasonal Ambient Temperatures on Fire-Stimulated Germination of Species with Physiological Dormancy: A Case Study Using Boronia (Rutaceae).

Dormancy and germination requirements determine the timing and magnitude of seedling emergence, with important consequences for seedling survival and growth. Physiological dormancy is the most widespread form of dormancy in flowering plants, yet the seed ecology of species with this dormancy type is poorly understood in fire-prone vegetation. The role of seasonal temperatures as germination cues in these habitats is often overlooked due to a focus on direct fire cues such as heat shock and smoke, and little is known about the combined effects of multiple fire-related cues and environmental cues as these are seldom assessed in combination. We aimed to improve understanding of the germination requirements of species with physiological dormancy in fire-prone floras by investigating germination responses across members of the Rutaceae from south eastern Australia. We used a fully factorial experimental design to quantify the individual and combined effects of heat shock, smoke and seasonal ambient temperatures on germination of freshly dispersed seeds of seven species of Boronia, a large and difficult-to-germinate genus. Germination syndromes were highly variable but correlated with broad patterns in seed morphology and phylogenetic relationships between species. Seasonal temperatures influenced the rate and/or magnitude of germination responses in six species, and interacted with fire cues in complex ways. The combined effects of heat shock and smoke ranged from neutral to additive, synergistic, unitive or negative and varied with species, seasonal temperatures and duration of incubation. These responses could not be reliably predicted from the effect of the application of single cues. Based on these findings, fire season and fire intensity are predicted to affect both the magnitude and timing of seedling emergence in wild populations of species with physiological dormancy, with important implications for current fire management practices and for population persistence under climate change.

Germination sensitivity to water stress in four shrubby species across the Mediterranean Basin.

Mediterranean shrublands are generally water-limited and fire-driven ecosystems. Seed-based post-fire regeneration may be affected by varying rainfall patterns, depending on species sensitivity to germinate under water stress. In our study, we considered the germination response to water stress in four species from several sites across the Mediterranean Basin. Seeds of species with a hard coat (Cistus monspeliensis, C.salviifolius, Cistaceae, Calicotome villosa, Fabaceae) or soft coat (Erica arborea, Ericaceae), which were exposed or not to a heat shock and smoke (fire cues), were made to germinate under water stress. Final germination percentage, germination speed and viability of seeds were recorded. Germination was modelled using hydrotime analysis and correlated to the water balance characteristics of seed provenance. Water stress was found to decrease final germination in the three hard-seeded species, as well as reduce germination speed. Moreover, an interaction between fire cues and water stress was found, whereby fire cues increased sensitivity to water stress. Seed viability after germination under water stress also declined in two hard-seeded species. Conversely, E.arborea showed little sensitivity to water stress, independent of fire cues. Germination responses varied among populations of all species, and hydrotime parameters were not correlated to site water balance, except in E.arborea when not exposed to fire cues. In conclusion, the species studied differed in germination sensitivity to water stress; furthermore, fire cues increased this sensitivity in the three hard-seeded species, but not in E.arborea. Moreover, populations within species consistently differed among themselves, but these differences could only be related to the provenance locality in E.arborea in seeds not exposed to fire cues.

Reproductive output, seed anatomy and germination under water stress in the seeder Cistus ladanifer subjected to experimental drought

Reproductive output and seed traits can be altered by water availability during seed formation and maturation, which could affect the population recovery after fire of seeders (i.e., species regenerating from seeds). This is important for species in fire-prone, dry areas that are projected to encounter reduced total precipitation and longer annual drought with climate change. Here we determine the sensitivity of several reproductive processes to drought in Cistus ladanifer, a plant widely distributed in the shrublands of the western part of the Mediterranean Basin. Three levels of annual drought were simulated in a shrubland by means of a rainout shelter and an irrigation system in 6×6m plots. Fruits and seeds from drought-exposed mother plants were collected, and reproductive output, seed size and anatomy studied. Seeds non-exposed/exposed to fire cues (heat plus smoke) were germinated at five levels of water stress (Ψs=0.0 to −0.50MPa). Hydrotime modeling was applied to germination under water stress. Plant growth was sensitive to drought, but reproductive output, seed size, dormancy and viability were not. Drought significantly affected seed anatomy, increasing the palisade layer at the micropyle. Drought in the maternal plants, in interaction with seed exposure to fire cues, significantly reduced final germination. Water stress during germination decreased final germination, independent of maternal plant drought, and interacted with fire cues to decrease germination when exposed. Hydrotime modeling confirmed that fire cues made seeds highly sensitive to water stress (Ψb (50)=−0.25MPa). Post-germination viability was reduced in seeds from drought-treated maternal plants that were exposed to fire cues and germinated under water stress. Reproductive output showed low plasticity in response to drought. However, the effects of drought in the mother plant affected seed anatomy and germination in interaction with fire cues. The conclusion is that exposing C. ladanifer maternal plants to drought arguably increases seed sensitivity to water limitations during germination after fire.

Physiological and behavioural responses of a small heterothermic mammal to fire stimuli

The predicted increase of the frequency and intensity of wildfires as a result of climate change could have a devastating impact on many species and ecosystems. However, the particular physiological and behavioural adaptions of animals to survive fires are poorly understood. We aimed to provide the first quantitative data on physiological and behavioural mechanisms used by a small heterothermic marsupial mammal, the fat-tailed dunnart (Sminthopsis crassicaudata), that may be crucial for survival during and immediately after a fire. Specifically, we aimed to determine (i) whether captive torpid animals are able to respond to fire stimuli and (ii) which energy saving mechanisms are used in response to fires. The initial response of torpid dunnarts to smoke exposure was to arouse immediately and therefore express shorter and shallower torpor bouts. Dunnarts also increased activity after smoke exposure when food was provided, but not when food was withheld. A charcoal/ash substrate, imitating post-fire conditions, resulted in a decrease in torpor use and activity, but only when food was available. Our novel data suggests that heterothermic mammals are able to respond to fire stimuli, such as smoke, to arouse from torpor as an initial response to fire and adjust torpor use and activity levels according to food availability modulated by fire cues.

Seed size and the regeneration niches of one rare (Melaleuca deanei) and three common (Melaleuca styphelioides, Melaleuca thymifolia and Melaleuca nodosa) Melaleuca (Myrtaceae) species of the Sydney region

AbstractMelaleuca species occupy varied habitats across Australia with 16 members of the genus occurring in the Sydney district including the rare species Melaleuca deanei F. Muell. Little is known of their germination and recruitment requirements. This paper reports on experiments assessing the effects of temperature, water potential, fire cues, light and shade levels on germination in four species of Melaleuca native to the Sydney region. For the shade experiment, seedling survival at 12 months is also reported. The experiments tested the hypothesis that M. deanei, which exhibits few seedlings in the field, has limited seedling recruitment because of its particular requirements for germination and establishment. Further, that it differs in these requirements from three common congenerics: M. nodosa (Sol ex Gaertn.) Sm., M. thymifolia Sm. and M. styphelioides Sm. Results indicate that M. deanei has a substantially similar temperature and water potential range for germination to the common congeners from 15 to 35°C, and 0 to −0.65 ψ. Melaleuca nodosa displayed the broadest regeneration niche on all factors assessed. Germination of M. styphelioides was significantly reduced in the dark and M. styphelioides and M. deanei were most sensitive to shade in the seedling establishment/post‐germination phase. Melaleuca deanei had significantly larger seed that was slower to germinate in all experiments. Germination of the four species was unaffected by the application of heat and smoke. The substantially similar germination parameters exhibited by the four species, despite differences in habitat, may reflect their close phylogenetic affinities. The effects of fire on stimulating seed release from the canopy, the high‐light environment post‐fire together with adequate follow‐up rainfall may all be critical in seedling establishment for M. deanei.

Comparative investigation of ‘survival’ and fatality factors in accidental residential fires

ObjectiveThis study compares the odds ratio (OR) values of factors associated with accidental residential fires where an individual has died versus fires where all occupants have survived (with no serious injury that required extended hospitalisation). MethodsAnalyses were based on 177 single fatalities (from coronial files) and 183 survivors (from interviews) of accidental residential fires. Results/discussionThe top seven risk factors (OR>10) that were significantly more associated with fatal than survived fires were, in descending order, psychotropic and sedative drug intake, discarded cigarettes, living alone, being aged over 70, being asleep, location in the room of fire origin (RFO) at ignition, and alcohol intake. The five risk factors (OR>10) that were more significantly associated with survived fires were, in descending order, cooking fires, electrical fires, kitchen being RFO, stove being an appliance involved in ignition, and fire in a one or two family dwelling. People who survived were more likely to wake up to non-smoke alarm fire cues (e.g. glass breaking, smoke) than a smoke alarm cue. ConclusionsThis comparative study provides new insights into statistically significant differences in risk factors between fatal fires and those fires where all occupants survived. The implications for fire engineering are complex as most fatal residential fires were associated with cognitive and physical impairment.

Life after fire: smoke and ash as germination cues in ericads, herbs and graminoids of northern heathlands

AbstractQuestionWhat is the impact of the fire cues smoke and ash on seed germination of important functional groups in the heathland system, namely ericads, herbs and graminoids? We predict that if germination from heathland seed banks is in part regulated by fire cues, there should be stronger responses to fire cue treatments in seed bank samples taken from heath that has not been recently burned in comparison with samples taken from newly burned heath, where seed banks have been exposed to the same cues in situ.LocationLygra, Lindås commune, western Norway.MethodsThe efficacy of smoke, charred wood, ash and heat in promoting germination has been documented in a wide range of species and systems, but relatively little work has been done on fire‐related cues in northern European heathlands under anthropogenic fire regimes. We studied fire experimentally by testing the effects of aqueous smoke solution, ash and a combination of the two treatments, on the germination of graminoids, herbs and ericads. A greenhouse germination trial compared seed banks from old heath (28 yr since the last fire) with seed banks from newly burned heath (burned the previous year), where we expected that fire‐cued germination had already occurred.ResultsWe found that both ericads and graminoids responded to fire cues, whereas herbs did not. In line with our predictions, responses were stronger in the old heath than in the young heath. Further, the smoke treatment is a more effective cue than ash across all functional groups.ConclusionsThe prevalence of positive fire cue responses across functional groups underscores the importance of fire in the ecology of these heathlands, and hence of burning as a central tool for their management. The finding that the germination response is stronger in naïve seed banks than in seed banks that have already been exposed to recent fire cues through in situ fires further supports the role of fire in the successional dynamics of these heathlands.

Germination of the endangered species Port Lincoln Speedwell in response to season and fire cues

Germination of the endangered species Port Lincoln Speedwell in response to season and fire cues

A Population Model of Chaparral Vegetation Response to Frequent Wildfires

The recent increase in wildfire frequency in the Santa Monica Mountains (SMM) may substantially impact plant community structure. Species of Chaparral shrubs represent the dominant vegetation type in the SMM. These species can be divided into three life history types according to their response to wildfires. Nonsprouting species are completely killed by fire and reproduce by seeds that germinate in response to a fire cue, obligate sprouting species survive by resprouting from dormant buds in a root crown because their seeds are destroyed by fire, and facultative sprouting species recover after fire both by seeds and resprouts. Based on these assumptions, we developed a set of nonlinear difference equations to model each life history type. These models can be used to predict species survivorship under varying fire return intervals. For example, frequent fires can lead to localized extinction of nonsprouting species such as Ceanothus megacarpus while several facultative sprouting species such as Ceanothus spinosus and Malosma (Rhus) laurina will persist as documented by a longitudinal study in a biological preserve in the SMM. We estimated appropriate parameter values for several chaparral species using 25years of data and explored parameter relationships that lead to equilibrium populations. We conclude by looking at the survival strategies of these three species of chaparral shrubs under varying fire return intervals and predict changes in plant community structure under fire intervals of short return. In particular, our model predicts that an average fire return interval of greater than 12 years is required for 50% of the initial Ceanothus megacarpus population and 25% of the initial Ceanothus spinosus population to survive. In contrast, we predict that the Malosma laurina population will have 90% survivorship for an average fire return interval of at least 6 years.

Field evidence of smoke‐stimulated seedling emergence and establishment in Mediterranean Basin flora

AbstractQuestionIn many plant species from fire‐prone ecosystems germination is promoted by smoke. Mediterranean Basin (MB) flora is no exception. However, most information regarding germination response to smoke in the MB comes from a few experiments performed in laboratory conditions. This approach does not consider factors that occur in the field, such as species interactions, density‐dependent processes or the fact that seeds spent time in the soil seed bank. In addition, species selection has been biased (e.g. there is a lack of information about annual species). Hence the importance of smoke relative to other fire cues is not clear, and we have a biased knowledge of post‐fire community assembly in the MB. In this framework, we tested the following hypotheses: (1) smoke enhances seedling emergence and establishment from the soil seed bank of MB species, and (2) annual species are an important component of this smoke‐stimulated flora.LocationMediterranean fire‐prone shrublands in eastern Spain. Western Mediterranean Basin.MethodsWe performed a field experiment in which we applied a liquid smoke treatment and tracked seedling emergence and seedling establishment during 1 yr. Differences between smoke and control subplots with respect to seedling emergence and seedling establishment were analysed at different scales: community, growth form (annual or perennial), family and species level.ResultsAt the community level, smoke played a clear role in seedling recruitment, increasing seedling emergence and seedling establishment. In addition, for most plots, families and species, establishment was higher in smoke subplots compared to the control. Annual species establishment was clearly stimulated by smoke but no effect was detected for perennials.ConclusionsSmoke derived from wildfires has a key effect on plant recruitment and hence on community assembly in the MB vegetation.

Effects of fire severity on early recovery of Patagonian steppes

Fire severity influences the recovery and biodiversity of plant communities. We compared the early post-fire recovery of plant functional groups in two sites (one burnt with high severity and one with low severity) in the north-western Patagonian steppe. We sampled the post-fire soil seed banks, as well as the composition and cover of aboveground plant species, and calculated richness, diversity and the percentage of exotic species. Low fire severity increased the diversity of aboveground vegetation and seed banks, whereas high fire severity reduced the cover of all functional groups, with the exception of fugitive species. Tiller production of perennial grasses decreased due to bud bank mortality. In the seed bank, high severity fire reduced fugitive species and increased exotic species. Fugitive species need fire to recruit, and the combination of fire cues and post-fire environmental conditions can explain the high abundance of these species after fire. In Patagonia, the use of fire is not considered a management option because fires are believed to be dangerous to humans, goods and services. However, north-western Patagonia is sparsely populated and the frequent wildfires pose no danger. It is necessary to increase the knowledge of the ecological processes of Patagonian ecosystems related to fire regime and land use, to achieve a reasonable balance between sustainable use and conservation in this region.

Fire cue effects on seed germination of six species of northwestern Patagonian grasslands

Abstract. Postfire recruitment of seedlings has been attributed to a stimulation of germination by fire-related cues. The germination response to heat shock (80 °C – 5 min), smoke (60 min), the combination of both factors and no heat no smoke (control) was studied in six native species (two dominant grasses, two dominant shrubs and two annual fugitive herbs) of northwestern Patagonian grasslands. Seeds of the grasses Festuca pallescens and Stipa speciosa and the shrub Senecio bracteolatus (Asteraceae) germinated when they were exposed to heat shock, whereas seeds of the other shrub, Mulinum spinosum (Apiaceae), were killed by this fire cue. In grasses, probably the glume of caryopsis protected embryos from heat. Possibly, the seed size could explain the different responses of the two shrubs. Heat combined with smoke reduced seed germination for S. speciosa and S. bracteolatus. The heat could have scarified seeds and the longer exposure to smoke could have been toxic for embryos. The same treatment increased germination of the annual fugitive herb Boopis gracilis (Calyceraceae). We concluded that fire differentially affects the seedling recruitment of the studied species in the northwestern Patagonian grasslands.