Fire Cues Research Articles

Seed release in serotinous lodgepole pine forests after mountain pine beetle outbreak

There are concerns that large-scale stand mortality due to mountain pine beetle (MPB) could greatly reduce natural regeneration of serotinous Rocky Mountain (RM) lodgepole pine (Pinus contorta var. latifolia) because the closed cones are held in place without the fire cue for cone opening. We selected 20 stands (five stands each of live [control], 3 years since MPB [3-yr-MPB], 6 years since MPB [6-yr-MPB], and 9 years since MPB [9-yr-MPB] mortality) in north central British Columbia, Canada. The goal was to determine partial loss of serotiny due to fall of crown-stored cones via breakage of branches and in situ opening of canopy cones throughout the 2008 and 2009 growing seasons. We also quantified seed release by the opening of forest-floor cones, loss of seed from rodent predation, and cone burial. Trees killed by MPB three years earlier dropped approximately 3.5 times more cones via branch breakage compared to live stands. After six years, MPB-killed stands had released 45% of their canopy seed bank through cone opening, cone fall due to breakage, and squirrel predation. Further losses of canopy seed banks are expected with time since we found 9-yr-MPB stands had 38% more open canopy cones. This was countered by the development of a modest forest-floor seed bank (6% of the original canopy seed bank) from burial of cones; this seed bank may be ecologically important if a fire or anthropogenic disturbance reexposes these cones. If adequate levels of regeneration are to occur, disturbances to create seedbeds must occur shortly after tree mortality, before the seed banks are lost. Our findings also suggest that the sustained seed rain (over at least nine years) after MPB outbreak may be beneficial for population growth of ground-foraging vertebrates. Our study adds insight to the seed ecology of serotinous pines under a potentially continental-wide insect outbreak, threatening vast forests adapted to regeneration after fire. Key words: biotic disturbance; cone burial; cone opening; Dendroctonus ponderosae; ground-foraging vertebrates; mountain pine beetle; natural regeneration; Pinus contorta var. latifolia; Rocky Mountain lodgepole pine; seed banks; serotiny (canopy seed storage); Tamiasciurus hudsonicus.

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

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.

The interaction of temperature, water availability and fire cues regulates seed germination in a fire-prone landscape

Ambient temperature and water availability regulate seasonal timing of germination. In fire-prone landscapes, the role of fire-related cues in affecting the range of temperatures and water potentials (psis) across which germination can occur is poorly known, especially in non-Mediterranean landscapes. We examined interactive effects of temperature (15 or 25 degrees C), psi (0 to -0.9 MPa), and fire-related cues (heat and smoke) on germination for seeds of three shrub species from fire-prone southeastern Australia. Incubation temperature affected germination of untreated seeds of Kunzea ambigua and Kunzea capitata (Myrtaceae) (reduction at 25 degrees C), but germination was uniformly low in Epacris obtusifolia (Ericaceae). Decreasing psi reduced germination across both incubation temperatures. Fire cues increased germination at both incubation temperatures and across psis, although in Kunzea the increase was smaller and occurred over a narrower range of psis at 25 degrees C. Hydrotime analysis suggested that fire cues reduced the amount of water necessary for germination of Kunzea seeds. Post-fire germination of the three study species may occur during the warm season, although it is reduced and confined to wet periods for the two Kunzea species. Warm season germination of the study species is consistent with a trade-off between the increased risk of failure of a cohort of seedlings, and benefits of early establishment of a cohort that may survive in an environment with aseasonal rainfall.

Social influence during the initial phase of a fire evacuation—Analysis of evacuation experiments in a cinema theatre

Unannounced evacuation experiments in a cinema theatre were analysed. The analysis focused on investigating if people are influenced by others during the initial phase of a fire evacuation. This type of influence is called social influence. Three separate behaviour types were identified and studied and the recognition and pre-movement time was measured. The results suggest that social influence is an important factor and that it becomes more important when the fire cue, e.g., the alarm, is unclear or uninformative. Results also indicate that social influence increases with decreasing distance between visitors. This result implies that individuals are influenced more by people who are close than by people who are further away.

Seed-coat Dormancy in Grevillea linearifolia: Little Change in Permeability to an Apoplastic Tracer after Treatment with Smoke and Heat

Seeds of Grevillea linearifolia germinate following fire, and have seed-coat dormancy broken by smoke and heat shock. Smoke breaks seed coat dormancy in Emmenanthe penduliflora by altering the permeability of the seed coat to an internal germination inhibitor, which subsequently escapes. This model was tested for in G. linearifolia by investigating the permeability of the seed coat to diffusion of high-molecular-weight compounds, and whether this changed after exposure to fire cues. Germination response of the seeds to heat shock, smoke or heat + smoke was tested. Penetration of Lucifer Yellow dye into intact seeds was examined after 24 and 48 h of exposure, and penetration of the dye from the inside of the seed coat outwards was examined after 24 h. Histochemical staining with Nile Red and Acridine Orange was used to locate cuticles, suberin and lignin. Twenty-three per cent of untreated seeds germinated; heat shock and smoke increased germination additively up to approx. 80 % for both cues combined. Lucifer Yellow did not penetrate fully through the seed coat of untreated seeds, whether diffusing inwards or outwards. Three barriers to diffusion were identified. Treatment with heat or smoke slightly increased penetration of the dye, but did not completely remove the barriers. Suberin was identified in secondary walls of exotestal and mesotestal cells, and was absent from primary cell walls. Movement of Lucifer Yellow occurred through the middle lamella and primary cell wall of suberized cells; movement of the dye was impeded where suberin was absent. Fire cues did not significantly decrease barriers to diffusion of high-molecular-weight compounds in the seed coat of Grevillea, and must be breaking dormancy by another mechanism.

Response surfaces for the combined effects of heat shock and smoke on germination of 16 species forming soil seed banks in south‐east Australia

Abstract There is limited understanding of how fire‐related cues such as heat shock and smoke can combine to affect the germination response of seeds from fire‐prone vegetation because combinations of multiple levels of both cues have rarely been investigated. Germination response surfaces were determined for the combination of heat shock and smoke by applying factorial combinations of temperature (up to 100°C) and aerosol smoke (0–20 min) to 16 species that form soil seed banks in the Sydney region of south‐eastern Australia. Duplicate populations of three species were also examined to assess the constancy of a species response surface. Of the 19 populations examined, 16 showed a germination response to both the fire cues, which combined interactively in 14 populations, and independently in two. No population responded only to a single cue; however, seeds of 11 populations responded to heat in the absence of smoke, and nine responded to smoke in the absence of heat. Heat applied in the absence of smoke negatively affected germination in seven populations, either progressively as temperature increased, or above a set temperature. Negative germination responses over part of the temperature range were fully reversed at higher temperatures for unsmoked seeds of four populations (curvilinear heat response). Smoke effects were most frequently positive over all or part of the range of durations used, and when combined with heat frequently fully or partially reversed negative heat effects. Three populations required the obligatory combination of smoke and heat. A novel response to the cues was observed for three species, with smoke reversing negative heat effects at 75°C, being supplanted by a positive heat response of unsmoked seed at 100°C. The response surface for duplicate populations of two of the three species examined was variable. Heat shock and smoke frequently combined to affect germination, in both positive and negative ways. Consequently, to gain an accurate assessment of the response of seeds to fires, an experimental design that samples within the potential response zones of germination cues is essential.

Seed banks of an Arizona Pinus ponderosa landscape: responses to environmental gradients and fire cues

We measured soil seed banks in 102 plots within a 110 000 ha Arizona Pinus ponderosa landscape, determined seed-bank responses to fire cues and tree canopy types (open or densely treed patches), compared seed-bank composition among ecosystem types, and assessed the utility of seed banks for ecological restoration. Liquid smoke was associated with increased community-level emergence from seed banks in greenhouse experiments, whereas heating to 100 °C had minimal effect and charred P. ponderosa wood decreased emergence. We detected 103 species in seed-bank samples and 280 species in aboveground vegetation. Erigeron divergens was the commonest seed-bank species; with the exception of Gnaphalium exilifolium , species detected in seed banks also occurred above ground. Although a dry, sandy-textured black-cinder ecosystem exhibited the greatest seed density, seed-bank composition was more ecosystem-specific than was seed density. Native graminoids (e.g., Carex geophila and Muhlenbergia montana ) were common in seed banks, whereas perennial forbs were sparse, particularly under dense tree canopies. Our results suggest that (i) smoke may increase emergence from seed banks in these forests, (ii) seed banks can assist establishment of major graminoids but not forbs during ecological restoration, and (iii) seed-bank composition is partly ecosystem-specific across the landscape.

Human Behaviour and Response Issues in High-Rise Residential Buildings

Integration of human behaviour and structural design in high-rise residential buildings has become an interesting topic for study. Although there has been growing research on human behaviour and awareness of fire safety in public and commercial buildings using response-based techniques, in residential buildings few studies have been done. In residential buildings, tenants come from various backgrounds and education levels from the lowest to the highest. Some may have proper training or may have attended fire safety courses and some may have not. If fire broke out in their building, what should they do? Do they know where to go and which route should they take to evacuate the building? This is because there does not appear to be any likelihood of significant reduction in cases of fire in Malaysia and other part of the world in the near future. Threat of fire is still high as the number of fire cases and fire casualty reported annually is overwhelming. There are hundreds of thousands of fires in buildings, hundreds of people have lost their lives, and thousands more have suffered injury, most likely from burns or smoke inhalation annually. In this paper we will discuss the perception and the action that the occupants of high-rise residential buildings are likely to take when they have seen fire cues or heard the fire alarm, motivation factors to trigger them to evacuate the building, choice of exit and evacuation behaviour and factors that most influent them during evacuation process.

How much seed remains in the soil after a fire?

Soil seed banks that persist after a fire are important in fire-prone habitats as they minimise the risk of decline or local extinction in plants, should the fire-free interval be less than the primary juvenile periods of the species. In two common woody plant genera (Acacia and Grevillea) in southeastern Australia, we examined the size and location of the residual seed bank after fire across areas of varying seedling densities at three locations in comparison to the distribution of seeds in the soil at an unburnt site. We found viable dormant seeds remaining in the soil after fire (evidence of residual soil seed bank). A significantly lower proportion of seeds remained in the top 5 cm of soil than at 5–10 cm or 10–15 cm soil depths, independent of seedling density or plant genus. This was due to greater germination, and possibly some seed mortality, near the soil surface. Reduced germination below 5 cm was probably due to the reduced efficacy of the fire cues that break seed dormancy, a declining ability of seeds to emerge successfully from such depths, and the lower abundance of seeds in the soil at such depths. The magnitude of the residual seed bank was similar across 0–5, 5–10 and 10–15 cm soil depths in Acacia suaveolens. For two Grevillea species, most residual seeds were at 0–5 and 5–10 cm. The residual soil seed bank in the top 10 cm of soil after fire varied across sites with estimates of 0, 19 and 27% in G. speciosa and 23, 35, and 55% in A. suaveolens. At two sites, both species had similar residual seed bank sizes, while at a third, there were large differences between the species (0–55%). The observed patterns imply that the fire-related cues that break seed dormancy generally declined with soil depth. For Acacia, seed dormancy is broken by heat shock, a fire-cue that declines with soil depth. Some 250 species (approx 15% of the fire-prone flora) in the region are thought to have dormancy broken by heat shock. For Grevillea, where seed dormancy is broken by the interaction of smoke and heat shock, at two sites, we suggest three possibilities: (i) the smoke cue declined with soil depth; (ii) both heat and smoke are obligatory for breaking seed dormancy; or (iii) the cues may be independent and additive and below the zone of soil heating, only a proportion of available seeds had dormancy broken by smoke alone. At a third site (no residual seed bank detected) the smoke cue was predicted not to have declined with soil depth. Up to 900 species (just under half the fire-prone flora) in the study region are thought to have seed dormancy broken by the interaction of heat and smoke during the passage of a fire.

Effects of seed storage and fire on germination in the nut-fruited Restionaceae species, Cannomois virgata

The effects of storage regime (laboratory and soil storage) and fire cues (heat and charate) on seed viability and germination were investigated in the nut-fruited Restionaceae species, Cannomois virgata (Rottb.) Steud. Soil-stored seeds were cycled through a series of alternating temperature and moisture regimes in a phytotron, while laboratory-stored seeds were kept at comparatively constant temperatures and low humidity. Seed deterioration in soil-stored seed was not significantly different to laboratory-stored seed. A marked improvement in germination of soil-stored seed was observed on exposure to charate from a fire.

Statistical analysis of response to fire cues

A statistical analysis of data on recognition of fire cues during sleep was carried out to determine the influence of the type of cue, sex and age on response. Four cues were used: crackling, shuffling, a flickering light and smell. The analysis was carried out on the observed data as well as on the corresponding parameters of a stochastic model of response previously developed. Linear models and, where required, a generalized linear model were used. At the low intensity levels used the most effective cues were auditory (crackle, followed by shuffle) while the two least effective were light and smell. Females had a waking up probability consistently higher than males, as well as a shorter response time. The influence of age was borderline for all cues. An important practical conclusion of the study is that a low level flickering light and fire smells are unlikely on their own to arouse sleeping people.

Occupants' behaviour in response to the high-rise apartments fire in Hiroshima City

A remarkable, large fire occurred in a 20 stories high-rise apartments in 1996 in Hiroshima City. The fire spread from the fire origin apartment unit on the 9th poor up to the top 20th floor, very quickly by external flame spread through balconies. The authors investigated the evacuation behaviour of the occupants including reaction to fire cues, motives for starting evacuation, and choice of evacuation route by means of questionnaire survey and also peer interviews with some of them, focusing on the use of elevators in evacuation by floor height and/or age group in this very rare fire incident. From the investigation, the following results were obtained. (1) Probably due to the experience of many past small fires, there was a time lag between the perception of fire and starting the evacuation. Many respondents started their evacuation on the directions of others, not by direct fire cues such as smoke. Also, the reaction of occupants after the perception of fire is affected by their perception of the seriousness of the fire, (2) The likelihood of elevator use in evacuation is mainly related to the floor height in which the occupants live, but is not so closely related to the age of the occupants, The proportion of elevator use in evacuation grows dramactically from the 10th to 13th poor. (3) People are likely to choose 'the route they usually use' or 'a safer route' rather than 'a closer route'.

Occupants' behaviour in response to the high‐rise apartments fire in Hiroshima City

A remarkable, large fire occurred in a 20 stories high-rise apartments in 1996 in Hiroshima City. The fire spread from the fire origin apartment unit on the 9th floor up to the top 20th floor, very quickly by external flame spread through balconies. The authors investigated the evacuation behaviour of the occupants including reaction to fire cues, motives for starting evacuation, and choice of evacuation route by means of questionnaire survey and also peer interviews with some of them, focusing on the use of elevators in evacuation by floor height and/or age group in this very rare fire incident. From the investigation, the following results were obtained. (1) Probably due to the experience of many past small fires, there was a time lag between the perception of fire and starting the evacuation. Many respondents started their evacuation on the directions of others, not by direct fire cues such as smoke. Also, the reaction of occupants after the perception of fire is affected by their perception of the seriousness of the fire. (2) The likelihood of elevator use in evacuation is mainly related to the floor height in which the occupants live, but is not so closely related to the age of the occupants. The proportion of elevator use in evacuation grows dramactically from the 10th to 13th floor. (3) People are likely to choose ‘the route they usually use’ or ‘a safer route’ rather than ‘a closer route’. Copyright © 1999 John Wiley & Sons, Ltd.

Investigation Of A Behavioural Response Model For Fire Emergency Situations In Secondary Schools

Though a large number of studies have been carried out in emergency movement and egress only few have considered evacuation of schools. A model to investigate and simulate the probable behavioral responses during fire related emergency situations has been developed for primary (elementary) and secondary (junior and senior high) schools. As part of this broader research program, a more limited study has been undertaken. The aim of this study is to determine the likelihood of responses by secondary school students to fire alarms and cues. A questionnaire was used and the behaviors were considered in terms of how they changed as a function of a number of variables such as different fire cues and social environment, grade level, gender, previous fire and drill experience. Responses to the questionnaire were analyzed to determine the most likely and unlikely behaviors from the model. The results indicate that for adolescents social environment can be the most pertinent variable influencing the decision to initiate risk reducing behavior. Therefore fire safety training for this age group must include presentation of psychological and social factors (such as the concepts of "pluralistic ignorance" and "diffusion of responsibility") that could influence an individual's behavior during an emergency.

Germination ecology of six shrubs in fire-prone Cape fynbos

To explain the recruitment and coexistence of species which establish after fire, this study predicted that each species would have different germination cues as a component of different regeneration niches. Furthermore, for species subject to natural fire frequencies of 10–20 years, fire-related cues, seed dormancy, extended longevity and fire-related germination cues might be predicted. However, results indicated broadly similar germination requirements. Seeds subjected to two heat treatments and a charcoal extract failed to show significantly enhanced germination. Instead, highest germination successes were achieved under alternating diurnal temperatures which implied an indirect fire cue, viz. the removal of insulating vegetation. Leachate solution inhibited germination in two species suggesting allelopathic effects during inter-fire periods. Only two species showed dormancy and three species did not have extended longevity but showed declining germinability after three years. Finally, in order to determine the potential germination from a soil-stored seed bank, data analysis simulated a seed bank comprising three years' accumulation of seeds. In each species the proportion of germinable seeds varied each year over the three years. Also, the germinability in response to ageing varied for each year's seed production. This would explain the variation in densities of the six species after different fire events, and hence offers a better explanation for species' coexistence.

The acquisition and maintenance of emergency evacuation skills with mildly to moderately retarded adults in a community living arrangement

This study investigated the effects of behavioral training on the acquisition, maintenance, and transfer of fire evacuation skills with mentally retarded adult subjects. Four subjects residing in a moderately supervised community living setting were taught to evacuate their apartments in the event of fire emergencies. A multiple baseline design across subjects was used to evaluate the impact of training on subjects' performance. Training components included instructions, modeling, behavioral rehearsal, feedback, and reinforcement. To facilitate maintenance of responding, all subjects received behavioral programming. Additional training was provided to facilitate responding during actual nighttime fire drills. To enhance the likelihood of generalization, all subjects were trained in their own apartments with actual and simulated fire cues. Assessment was carried out during daytime and nighttime hours. Day and night assessment of responding after treatment termination was also conducted. The results indicated a high level of mastery by all subjects across acquisition and response maintenance training, although only moderate levels of responding were noted during the nighttime period. Implications for future research efforts in the area of emergency responding in community settings are discussed.

Human awakening and subsequent identification of fire-related cues

Twenty-four college-age male subjects, employed for one night each, were evaluated on their ability to awaken and then identify fire cues. Twelve subjects were exposed to smoke alarm warning signals of three intensities, while the second twelve subjects were exposed to a smoke odor, a heat presentation, and a single smoke alarm warning signal. Subjects were, in all cases, awakened by alarms that reached their ears at signal/noise ratios of 34 dB. They were considerably less likely to be awakened by heat, the smoke odor, and alarm sounds that reached their ears at signal/noise ratios of 10 dB or less. Upon awakening, subjects repeatedly failed to correctly label radiant heat presentations and smoke alarm warnings as fire cues.

Human Awakening and Subsequent Identification of Fire-Related Cues

Twenty-four college-age male subjects, employed for one night each, were evaluated on their ability to awaken and then identify fire cues. Twelve subjects were exposed to smoke alarm warning signals of three intensities, while a second set of twelve subjects were exposed to a smoke odor, a heat presentation, and a single smoke alarm warning signal. Subjects were, in all cases, awakened by alarms that reached their ears at signal/noise ratios of 34 dB. They were considerably less likely to be awakened by heat, smoke odor, and alarm sounds that reached their ears at signal/noise ratios of 10 dB or less. Upon awakening, subjects repeatedly failed to correctly label radiant heat presentations and smoke alarm warnings as fire cues.