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The Need for Consideration of Fire Behavior and Effects in Prescribed Burning
Abstract
Prescribed burns are increasingly being used in ecological restoration and vegetation management. Despite the accumulation of scientific information on fire behavior and fire effects, however, in many cases fires are prescribed without consideration of such information and often simply because of evidence of past fires. Rather than basing fire management plans on ideas of the historical “natural” occurrence of fire, we present the case for fire management being based on the fire effects desired. Effective fire management and development of proper fire prescriptions require an understanding of fire processes and heat transfer that explain fire behavior characteristics, as well as an understanding of how fire behavior is coupled to specific fire effects. We provide a basic introduction to these concepts and processes, which will help in understanding the importance of having a more technical understanding of fire. The discussion includes the processes of heat transfer and the relative role of various fuel variables in these processes, as well as the concepts of fire intensity, rate of spread, fuel consumption, duff consumption, fire frequency, and the ecological effects associated with variation in these characteristics of fire behavior.
... Bond and van Wilgen (1996) defined fire regimes as the combination of how often fire occurs (frequency), when it occurs (season) and how fiercely it burns (fire type, intensity, and typical fire sizes). Consequently effective prescribed fire management and development of proper fire prescriptions requires on one side the understanding of the survival strategies of plant species and the succession dynamics of vegetation communities in a specific fire regime (Agee 1996, Bond andvan Wilgen 1996); on the other side it requires an understanding of fire processes and heat transfer that explain characteristics of normal fire behaviour (type, intensity, seasonality, ignition patterns) a s well as an understanding of how fire behaviour is coupled to specific fire effects Deeming 1980, Johnson andMiyanishi 1995). ...
... To plan prescribed fire to achieve stated objectives, to minimize cost of control, and to reduce the risk of escape, a firm basis of fire behaviour estimation must be established (Johnson and Miyanishi 1995). Because specific effects are sought and specific sites are burned under pre-selected conditions to achieve them, in many cases prescribed burning poses the most stringent requirements for fire behaviour prediction models (Albini 1976). ...
... being based on what appeared at the time to be self-evident reasoning (Johnson and Miyanishi 1995). ...
Prescribed burning is one of the main issue of current fire research in Mediterranean countries. Several benefits are expected: fire hazard abatement,
nature conservation management, carbon emission reduction. Nevertheless in
Italy very few knowledge is available about prescribed burning applicability. The
develop of new expertises is required. To minimize the risk with introducing
prescribed burning in fire management practices it is necessary to conduct
learning experiments. Manipulative fire experiments which test the effect of
different prescribed fire regimes (frequency, seasonality, intensity) have proved
to be useful throughout world ecosystems. With the objective to develop and
transferring expertises about the design of prescribed fire experiments two
studies were carried out. Both studies adopted a microplot scale analysis of fire
behaviour for correlation with ecological effects on vegetation.
... Second, does variation in severity of fires affect survival of L. japonicum genets? Fire severity, the extent to which organic biomass is reduced by fire (Keeley et al. 2008, Keeley 2009), varies locally with amounts of flammable fuels (Johnson and Miyanishi 1995). In pine savannas, local variation in fuels change fuel consumption, maximum temperatures, and damage to groundcover plants (Thaxton and Platt 2006). ...
... Pre-and post-fire fine-fuels were clipped within a 10 cm 2 area, oven dried at 50 o C, and weighed to determine total fuel consumption per plot. Fuel consumption was converted to total heat released per unit area using methods described by Johnson and Miyanishi (1995). Differences in total heat released among fuel treatments provided estimates of fire severity. ...
... Total heat released per unit area for increased fuels, reduced fuels, and unaltered fuels. Total heat per unit area (kJ/m 2 ) was calculated by multiplying total fuel consumption (t/ha) by 18,800 kJ/kg (Johnson and Miyanishi 1995). Data are expressed as means + standard errors. ...
... In the 1960s, after decades of fire suppression, land managers and ecologists developed the attitude that fires are a natural part of many ecosystems, rather than a purely destructive force (Johnson & Miyanishi 1995). Prescribed burning is a management technique that evolved from this shift in attitude, and has been used in a variety of fire-dependent ecosystems including prairies, savannas, and forests. ...
... The decision to reintroduce fire, however, is often based on a general notion of fire as a historically-important process that implicitly should be introduced. Although such a premise has merits, the use of prescribed burning as a restoration tool is only advisable to achieve specific goals (Johnson & Miyanishi 1995). ...
... Our current knowledge of prescribed burning has developed largely since the 1970s, usually in the form of technical literature that is not always read by managers and ecologists. Of the existing literature on the use of prescribed fire in the restoration and management of intact vegetation, most pertains to select grassland and savanna ecosystems (Johnson & Miyanishi 1995). By far the majority of the prescribed burning literature has been generated from silvicultural studies of site regeneration after forest harvesting (e.g. ...
... However, the broad application of burning as a management tool often only considers whether a particular habitat type or region was historically exposed to fire regimes. Such broad application fails to consider whether prescribed burning actually achieves the desired ecological effects or management goals for individual, rare species (Johnson & Miyanishi, 1995). Thus, although the benefits of fire on plant communities are widely documented, the impacts of burning on rare plant species are much less understood than for common plant species. ...
... Negative burn responses could be explained by burning too frequently and preventing adequate recovery or burning plants during their growing season (Brockway et al., 2002;Valk o et al., 2014). Similarly, negative burn responses could be the result of more severe burns in areas with higher fuel availability (Johnson & Miyanishi, 1995;Richter et al., 2019). Severe burns could damage individuals-particularly since all species negatively affected by burns were perennials-or change moisture dynamics that could negatively impact mesic species (Richter et al., 2019). ...
Rare species serve important ecosystem functions, including community resilience to global change. Yet rare species are disappearing globally because of anthropogenic activities such as fire suppression. Prescribed burning is a widespread management approach that can reduce invasive plant presence, recycle nutrients, and restore species diversity. However, the effects of prescribed burning on rare plants are not well understood. We analyzed the population dynamics of 67 rare, native plant species in response to prescribed burning using the Chicago botanic garden's Plants of Concern dataset. This dataset includes rare plant populations concentrated in the northeast part of Illinois, and a few populations in Indiana and Wisconsin, United States. We evaluated the effects of burning by comparing the percent change in population size in the short‐term (1–2 years) and long‐term (3–4 years) after prescribed burning, to the percent change in population size not following burns. In a global model with all species, we did not detect the effects of burning on percent change in population size. In species‐level analyses, we detected burn effects for most species for which we had the statistical power to detect possible burn responses, although the direction of their responses was mixed. Five species responded consistently between short‐ and long‐term datasets, and four species had mixed responses, with most responding positively over the short‐term and negatively over the long‐term. We complemented this analysis with a literature review of fire responses for available species. Our literature review revealed more responses to burning than what we found from our analyses; however, most of this evidence does not compare burned and unburned populations directly and should be treated cautiously. Through community science monitoring efforts, we were able to compile one of the largest studies of burn effects on rare plants to date, but continued monitoring is necessary to fully evaluate how prescribed burning impacts rare plant species.
... Many research and operational users of fire modelling systems have come to view Eqns 6 and 7 as universal in nature, probably as a result of the manner in which they are oftentimes treated in the wildland fire science and management literature (e.g. Rothermel and Deeming 1980;Norum 1982;Simard et al. 1989;Johnson and Miyanishi 1995;Andrews et al. 2011) and more recently on certain websites such as Forest Encyclopaedia Network (Kennard 2008a). As Nelson and Adkins (1986) point out, this is 'despite the fact that it was developed from a field study in a single fuel type' (see footnote A in Table 1). ...
... There has been very little research undertaken to evaluate the performance of the Van Wagner (1973) h s models when implemented within the context of the US fire modelling systems such Barney et al. 1984;Kercher and Axelrod 1984;Keane et al. 1989;Johnson 1992;Johnson and Gutsell 1993;Johnson and Miyanishi 1995;Burrows 1997;Gould et al. 1997;Dickinson and Johnson 2001). ...
This state-of-knowledge review examines some of the underlying assumptions and limitations associated with the inter-relationships among four widely used descriptors of surface fire behaviour and post-fire impacts in wildland fire science and management, namely Byram's fireline intensity, flame length, stem-bark char height and crown scorch height. More specifically, the following topical areas are critically examined based on a comprehensive review of the pertinent literature: (i) estimating fireline intensity from flame length; (ii) substituting flame length for fireline intensity in Van Wagner's crown fire initiation model; (iii) the validity of linkages between the Rothermel surface fire behaviour and Van Wagner's crown scorch height models; (iv) estimating flame height from post-fire observations of stem-bark char height; and (v) estimating fireline intensity from post-fire observations of crown scorch height. There has been an overwhelming tendency within the wildland fire community to regard Byram's flame length–fireline intensity and Van Wagner's crown scorch height–fireline intensity models as universal in nature. However, research has subsequently shown that such linkages among fire behaviour and post-fire impact characteristics are in fact strongly influenced by fuelbed structure, thereby necessitating consideration of fuel complex specific-type models of such relationships.
... Many research and operational users of fire modelling systems have come to view Eqns 6 and 7 as universal in nature, probably as a result of the manner in which they are oftentimes treated in the wildland fire science and management literature (e.g. Rothermel and Deeming 1980;Norum 1982;Simard et al. 1989;Johnson and Miyanishi 1995;Andrews et al. 2011) and more recently on certain websites such as Forest Encyclopaedia Network (Kennard 2008a). As Nelson and Adkins (1986) point out, this is 'despite the fact that it was developed from a field study in a single fuel type' (see footnote A in Table 1). ...
... There has been very little research undertaken to evaluate the performance of the Van Wagner (1973) h s models when implemented within the context of the US fire modelling systems such Barney et al. 1984;Kercher and Axelrod 1984;Keane et al. 1989;Johnson 1992;Johnson and Gutsell 1993;Johnson and Miyanishi 1995;Burrows 1997;Gould et al. 1997;Dickinson and Johnson 2001). ...
This state-of-knowledge review examines some of the underlying assumptions and limitations associated with the inter-relationships among four widely used descriptors of surface fire behaviour and post-fire impacts in wildland fire science and management, namely Byram's fireline intensity, flame length, stem-bark char height and crown scorch height. More specifically, the following topical areas are critically examined based on a comprehensive review of the pertinent literature: (i) estimating fireline intensity from flame length; (ii) substituting flame length for fireline intensity in Van Wagner's crown fire initiation model; (iii) the validity of linkages between the Rothermel surface fire behaviour and Van Wagner's crown scorch height models; (iv) estimating flame height from post-fire observations of stem-bark char height; and (v) estimating fireline intensity from post-fire observations of crown scorch height. There has been an overwhelming tendency within the wildland fire community to regard Byram's flame length–fireline intensity and Van Wagner's crown scorch height–fireline intensity models as universal in nature. However, research has subsequently shown that such linkages among fire behaviour and post-fire impact characteristics are in fact strongly influenced by fuelbed structure, thereby necessitating consideration of fuel complex specific-type models of such relationships.
... Knowledge of relevant biomass characteristics, or wildland fuels, as they affect fire propagation and behaviour is necessary to inform a wide range of fire management applications aimed at mitigating the occurrence of large fires and their impact on human well-being [7,8]. Applications may include the calculation of broad-scale fire danger for issuing public warnings [9][10][11], predicting wildland fire, or bushfire (a bushfire is a generic term used in Australia to denote rural fires of unplanned origin occurring in various types of vegetation (e.g., grasslands, forests, shrublands), both with and without a suppression objective attached to them; it is synonymous with "wildfire" or "wildland fire"), behaviour to aid fire suppression planning [12][13][14], and support of a range of other activities such as defining fuel management needs [15,16], prescribed burn planning [17], conducting risk assessments [18], calculating smoke emissions [1], and predicting fire effects at multiple scales [19,20]. ...
... Boulders/rock with algae, lichen, or scattered plants, or alpine fjaeldmarks 18 Eucalyptus low open woodlands with hummock grass 19 Eucalyptus low open woodlands with tussock grass 20 ...
Appropriate categorisation and description of living vegetation and dead biomass is necessary to support the rising complexity of managing wildland fire and healthy ecosystems. We propose a hierarchical, physiognomy-based classification of wildland fire fuels—the Bushfire Fuel Classification—aimed at integrating the large diversity of Australian vegetation into distinct fuel types that are easily communicated and quantitatively described. At its basis, the classification integrates life form characteristics, height, and foliage cover. The hierarchical framework, with three tiers, describes fuel types over a range of application requirements and fuel description accuracies. At the higher level, the fuel classification identifies a total of 32 top-tier fuel types divided into 9 native forest or woodland, 2 plantation, 10 shrubland, 7 grassland, and 4 other fuel types: wildland urban interface areas, horticultural crops, flammable wetlands, and nonburnable areas. At an intermediate level, the classification identifies 51 mid-tier fuel types. Each mid-tier fuel type can be divided into 4 bottom-tier fuel descriptions. The fuel types defined within the tier system are accompanied by a quantitative description of their characteristics termed the “fuel catalogue”. Work is currently under way to link existing Australian state- and territory-based fuel and vegetation databases with the fuel classification and to collate existent fuel characteristics information to populate the fuel catalogue. The Bushfire Fuel Classification will underpin a range of fire management applications that require fuel information in order to determine fire behaviour and risk, fuel management, fire danger rating, and fire effects.
... However, maximum temperatures do not provide a strong mechanistic link to fire effects (Van Wagner and Methven 1978;Bova and Dickinson 2008). The fire science literature has demonstrated that temperature-derived metrics are inadequate descriptors of fire intensity and that temperature might be a physically incorrect parameter because it is defined only for systems in thermodynamic equilibrium (Van Wagner and Methven 1978;Johnson and Miyanishi 1995;Kremens et al. 2010;Alexander and Cruz 2012). When relating observed temperatures with fire intensity, the expected diffusion flame temperature in the burns of Davies et al. (2015) would typically all be within the same maximum range and of the order of 800-11008C regardless of fire intensity (McNaughton et al. 1998;Smith et al. 2005;Wotton et al. 2012). ...
... If Davies et al. (2015) sought to characterise the impact of the radiative heat flux on the plants, then time-integrated temperature or maximum temperatures are not valid proxies. The radiative heat transfer process is proportional to the fourth power of temperature, making a linear temperature with time product inadequate to describe this mechanism (Van Wagner and Methven 1978; Johnson and Miyanishi 1995;Kremens et al. 2010;Alexander and Cruz 2012;Wotton et al. 2012). Further complicating the assumption that their time-integrated temperatures can serve as proxy for heat flux measurements is the lack of description of the vegetative thermal boundary conditions. ...
A recent study by Davies et al. sought to test whether winter grazing could reduce wildfire size, fire behaviour and intensity metrics, and fire-induced plant mortality in shrub-grasslands. The authors concluded that ungrazed rangelands may experience fire-induced mortality of native perennial bunchgrasses. The authors also presented several statements regarding the benefits of winter grazing on post-fire plant community responses. However, we contend that the study by Davies et al. has underlying methodological errors, lacks data necessary to support their conclusions, and does not provide a thorough discussion on the effect of grazing on rangeland ecosystems. Importantly, Davies et al. presented no data on the post-fire mortality of the perennial bunchgrasses or on the changes in plant community composition following their experimental fires. Rather, Davies et al. inferred these conclusions based on their observed fire behaviour metrics of maximum temperature and a term described as the 'heat load'. However, we contend that neither metric is appropriate for describing the heat flux impacts on plants. This lack of post-fire data, several methodological errors and the use of inappropriate thermal metrics limit the authors' ability to support their stated conclusions.
... Numerous studies on other fire-prone communities have established the relation between specific composition or vegetation structure and fire behaviour: vegetation height/flame height (Trabaud 1979;Chandler et al. 1983); vegetation height/maximum temperatures (Hobbs and Gimingham 1984); horizontal and vertical fuel continuity/fire behaviour (Brown 1981;Basanta et al. 1988;Whelan and York 1998); total biomass/intensity and severity (Papió and Trabaud 1991;Bessie and Johnson 1995); fractional fuel structure/intensity and velocity of fire propagation (Burgan and Rothermel 1984;Papió and Trabaud 1991); moisture content of live and dead fractions/intensity and severity (Cheney et al. 1993;Johnson and Miyanishi 1995;Burgan et al. 1998;Piñol et al. 1998). Thus a detailed knowledge of the structure of the fire-prone community is considered the first step in any attempt to predict fire behaviour and evaluate its possible consequences for the ecosystem Oechel 1991a, 1991b;Usó et al. 1997). ...
... On the three sites studied we found notable differences with respect to the intensity and severity of the burns, in spite of the fact that they were carried out in the same time period, in similar communities and under similar climatic conditions. This fact has been pointed out repeatedly in other communities (Whelan and York 1998;Baeza 2001), and it has been suggested that small variations in fuel amounts or in vegetation moisture content (Johnson and Miyanishi 1995;Baeza et al. 2002) could be responsible for these differences. In our experience, a higher intensity value was reached in site 1 (located on a South-facing slope) where live woody moisture content was lower than observed in sites 2 and 3 (located on North-facing slopes). ...
Since the early 1990s, Mediterranean gorse shrublands have expanded significantly in the Mediterranean regions of Spain mainly as a result of the increase in the frequency and extension of forest fires. Mediterranean gorse (Ulex parviflorus), which has been described as a degradation stage of forest communities after fire, has also been described as a fire-prone community. Thus, its presence increases the risk that new fires might occur. In spite of this evidence, there is little information on both the composition and structural characteristics of these communities or the relationship that might exist between these vegetation characteristics and fire behaviour. In this paper we present the results of a characterization of the vegetative structure (plant density, specific composition , biomass fractions, and horizontal and vertical fuel distribution) in Mediterranean gorse. We also analyse fire behaviour using indicators obtained at different scales. Our results show mature Mediterranean gorse shrublands to be communities with high biomass values (3000–4000 g m −2) and high horizontal and vertical vegetation continuity , in which the proportion of fine dead fuel fractions with low moisture content is around 50% of the total phytomass present. Ulex parviflorus is the dominant species and its degree of dominance is a key element in the behaviour of fire. Both the fire-line intensity values and the fire severity values observed can be considered high with respect to those observed in other Mediterranean communities, thus confirming Mediterranean gorse as a high-risk community.
... Rates of spread and measures of intensity are often used to quantify behavior of wildland fires (Pyne et al. 1996, Johnson andMiyanishi 1995). This information allows managers to predict potential fire behavior and design methods and/or guidelines in which to suppress wildfires. ...
... Relates to fire intensity and duff (partially decomposed organic horizon beneath litter) consumption; composition of vegetation, etc. (Johnson and Miyanishi 1995 Dead fuels versus live fuels exhibit major differences in combustion and spread and intensity and rate of spread (Rothermel 1983). Landscape character -Source patch sizes and ecological edge ...
... Many research and operational users of fire modelling systems have come to view Eqns 6 and 7 as universal in nature, probably as a result of the manner in which they are oftentimes treated in the wildland fire science and management literature (e.g. Rothermel and Deeming 1980;Norum 1982;Simard et al. 1989;Johnson and Miyanishi 1995;Andrews et al. 2011) and more recently on certain websites such as Forest Encyclopaedia Network (Kennard 2008a). As Nelson and Adkins (1986) point out, this is 'despite the fact that it was developed from a field study in a single fuel type' (see footnote A in Table 1). ...
... There has been very little research undertaken to evaluate the performance of the Van Wagner (1973) h s models when implemented within the context of the US fire modelling systems such Chandler et al. 1983;Barney et al. 1984;Kercher and Axelrod 1984;Keane et al. 1989;Johnson 1992;Johnson and Gutsell 1993;Johnson and Miyanishi 1995;Burrows 1997;Gould et al. 1997;Dickinson and Johnson 2001). ...
This state-of-knowledge review examines some of the underlying assumptions and limitations associated with the inter-relationships among four widely used descriptors of surface fire behaviour and post-fire impacts in wildland fire science and management, namely Byram’s fireline intensity, flame length, stem-bark char height and crown scorch height. More specifically, the following topical areas are critically examined based on a comprehensive review of the pertinent literature: (i) estimating fireline intensity from flame length; (ii) substituting flame length for fireline intensity in Van Wagner’s crown fire initiation model; (iii) the validity of linkages between the Rothermel surface fire behaviour and Van Wagner’s crown scorch height models; (iv) estimating flame height from post-fire observations of stem-bark char height; and (v) estimating fireline intensity from post-fire observations of crown scorch height. There has been an overwhelming tendency within the wildland fire community to regard Byram’s flame length–fireline intensity and Van Wagner’s crown scorch height–fireline intensity models as universal in nature. However, research has subsequently shown that such linkages among fire behaviour and post-fire impact characteristics are in fact strongly influenced by fuelbed structure, thereby necessitating consideration of fuel complex specific-type models of such relationships.
... In Slovakia, Act No. 314/2001 Coll. on Fire Protection [21] and in the Czech Republic, Decree ...
This monograph presents relevant knowledge, completed research results, derived new knowledge and information, concerning not only the factors influencing the behaviour of wildland fires but, especially, the management and tactics applied to fight them.
In addition to the knowledge on fire management and tactics applied in the conditions of the Slovak Republic, it also presents the procedures used abroad, in another Central European countries like Czech Republic, Hungary, and Poland. Although some of them cannot be applied in the conditions of the Slovak Republic due to the current legal situation. For this reason, they should be seen as inspiration for the innovation of existing methodological and tactical procedures in the future.
This monograph is a response to the demand of the practice to summarize and synthesize the existing knowledge in the field of tactics of firefighting in the natural environment not only from the domestic environment, but also from abroad and to convey them to a wide range of professionals and the public.
... Furthermore, predicting the level of stem scarring caused by PB is of economic significance, due to the lower value of damaged timber [42][43][44]. Bio-physical approaches have increased the understanding of fire-induced stem damage and the associated tree response, but they have also revealed large gaps in the knowledge (e.g., [17,20,[45][46][47][48][49][50][51]). ...
Little is known about the interactions between the variables involved in the post-fire response of Mediterranean pine species to prescribed burning (PB). Thus, it is essential to develop an empirical model in order to assess the influence of tree and stand attributes, burn season, and fire severity on the probability of stem cambium damage occurring. Prescribed burnings were conducted in different seasons and areas covering a wide climatic and ecological range. Potential explanatory variables were measured. A random effects hurdle model framework was used to evaluate the temperature duration above 60 °C as a proxy for stem cambium damage at tree scale. The results showed significant differences in cambium damage between the PB seasons. Pinus nigra was more resistant than other pine species. Bark thickness was critical for protecting cambium. Volume of crown scorch, percentage of stem scorch, and maximum outer bark temperature were directly related to temperature duration above 60 °C in the cambium. Prescribed burning conducted under tree canopy in Mediterranean pine species generally results in a low level of cambium damage. Empirical models could help managers to predict the effects of PB and thus select the most suitable prescriptions.
... These processes are crucial for alerting relevant persons and supporting their decision making, the wide scale of applications for management (control) of fires as well as creating measures to prevent large fires (Gill et al. 2013;Stephens et al. 2014). Such applications may be aimed at identifying fire hazards and issuing fire warnings (Brown & Davis 1973;Harris et al. 2017;Deeming et al. 1977), an assessment of the risk of fire occurrence in the natural environment (Ager et al. 2010;Majlingová 2015), modelling the behaviour of fire in various types of vegetation (for example grasslands, forests, bushes), planning of fire-fighting tactics and predicting the impact of fire from different perspectives (Johnson & Miyanishi 1995;Reinhardt et al. 2001). ...
The paper presents the results of the solution defining the possible application of the adapter as a fire-fighting mobile device with a base machine of a forest wheeled skidder (LKT) in the fire protection of forests in the Slovak Republic. Following the challenging accessibility to fire-fighting machinery during any intervention in forestry operation, the main aim was formulated. It will be about basic technical parameters of the DATEFF fire-fighting adapter, resulting from operational measures and following specification of its tactical deployment in extinguishing forest fires. This fact also follows from based on statistically processed data on fire in state forests of the Slovak Republic in the last ten years. The greatest damage occurs mainly the forests at a slope gradient of 16%. Designed fire adapter is structurally designed mainly to these terrains. Regarding its design and technical parameters, the proposed DATEFF adapter can be employed tactically as fire-fighting mobile device. In the case of an unavailable water source without access to the forest transport network, the adapter can be used as a part of long-distance water transport or as a mobile device for emergency import of material. Another option is to use it as a water tank in inaccessible terrain with the possibility of refilling using a Bambi bag and a helicopter. This fire-fighting adapter DATEFF is designed for forest wheel tractors that reach 40% slope availability, are able to work on the stand area, overcome obstacles and are available in sufficient quantities in all Slovak forest owners.
... Errors in estimated FMC have real-world consequences: over-predicting FMC can result in escaped prescribed fires, higher severity fires, and less predictable fire behavior. Underpredicting FMC may cause unsuccessful prescribed fires (for example, 41% of interrupted burns in Portugal were due to high FMC, Fernandes and Botelho, 2004), due to exaggerated perceptions of risk (Quinn-Davidson and Varner, 2012;Bovill et al., 2015), or in failing to meet intended objectives, such as fuel hazard reduction or ecosystem restoration (Bovill et al., 2015;Johnson and Miyanishi, 1995;Fernandes and Botelho, 2004). In the context of modeling, reported uncertainty in FMC of +/− 50% (that is, ±2 percentage points around a mean of 4 percent FMC) can produce errors of up to 80% in output variables such as the rate of fire spread (Trevitt, 1988). ...
Dead fuel moisture influences the risk of fire ignition events, with implications for fire hazards, risk mitigation, and the design of prescribed burning activities. Because direct fuel moisture measurements are rarely available, fuel moisture must be estimated when evaluating fire risks. Most estimates rely primarily on atmospheric conditions and ignore the interaction of fuels with the soil surface with which they are in hydraulic contact. In this study we explore whether dead fuel moisture predictions can be improved with information about surface soil moisture. Despite the likelihood that dead fuels would exchange water with underlying soil, the influence of soil moisture on fuel moisture has been poorly studied. An analysis of 202 observations of co-located soil moisture, 1 and 10 h fuel moisture measurements, with environmental and meteorological covariates, showed that soil moisture had a small but significant effect on fuel moisture across all sampled conditions. The influence of soil moisture on fuel moisture was the most important among all other environmental factors for wet soil conditions and 10-h fuels, where a 1% increase in soil moisture content led to approximately a 0.6% increase in fuel moisture. The effect of soil moisture on 1-h fuel moisture although significant was small. Incorporating spatio-temporal variability of soil moisture into time-series or spatial predictions of fuel moisture tended to (i) reduce the seasonal duration in which fuels had a high probability of ignition by an average of 52–60 days across the tested years, and (ii) increased the heterogeneity of the probability of ignition through space, compared with similar models that did not incorporate soil moisture information.
... Mechanistic models offer opportunities to quantify or guide the mitigation of these risks beyond the domains of empirical models (Butler & Dickinson, 2010;Dickinson & Johnson, 2001;Johnson & Miyanishi, 1995;O'Brien et al., 2018). In particular, recent work has highlighted the critical role of plant traits as drivers of wildland flammability (e.g. ...
Floral fire ecology incorporates a feedback loop in which plants influence fire behaviour and fire behaviour influences the flora. Recent advances in fire behaviour modelling have quantified many plant‐based drivers of fire behaviour, but the consequent ecological effects of this have not yet been adequately modelled mechanistically.
Here, I introduce the Fire Research and Modelling Environment (FRaME) as the open‐source R package frame on GitHub. FRaME calculates the influence of plants on fire behaviour using a biophysical, mechanistic model of fire behaviour, building this into complex simulations. From these, it models heat transfer from flames into surrounding surfaces, calculating its ecological effects on plants and soils. I demonstrate the application of the central analysis functions using a detailed case study, in which I validate predictions of fire behaviour and ecological effects, and derive quantitative measures for the efficacy of different management treatments to mitigate fire risk to a vulnerable ecosystem.
FRaME modelling predicted ecological effects such as the breaking of seed dormancy, scorch and the girdling of different tree strata, consistent with observed effects and providing insights into treatment efficacy that were not captured by existing assumptions. FRaME analyses were able to identify treatments that both increased the likelihood of success in containing fires and minimised fire impacts on a fire‐sensitive ecosystem.
FRaME provides a platform to examine the full role of fire in an ecosystem, from the ways that biota drive flammability to the influence of that flammability on the ecosystem. By mechanistically incorporating the effect of biophysical drivers throughout this feedback, FRaME can provide novel insights and solutions for complex problems, quantify risk and guide effective mitigation measures. The model is extensible, providing a conceptual framework into which emerging work on flammability and fire effects can be incorporated.
... Recurrent fires consume less fuel and produce less heat, which does not penetrate into soil as deeply as during high-intensity fires (Smith et al., 2016). Accordingly, fungal community shifts in pyrogenic ecosystems may be 'relatively modest' (Johnson & Miyanishi, 1995;Choromanska & DeLuca, 2001;Korb et al., 2004) and primarily be driven by indirect fire-induced changes in soil properties (e.g. pH shifts) and plant communities (e.g. ...
While the negative effects of infrequent, high-intensity fire on soil fungal abundance are well-understood, it remains unclear how the short-term history of frequent, low-intensity fire in fire-dependent ecosystems impacts abundance, and whether this history governs any abundance declines. We used prescribed fire to experimentally alter the short-term fire history of patches within a fire-frequented old-growth pine savanna over a 3 y period. We then quantified fungal abundance before and after the final fire using phospholipid fatty acid (PLFA) assays and Droplet DigitalPCR (ddPCR). Short-term fire history largely did not affect total fungal abundance nor pre- to post-fire abundance shifts. While producing similar conclusions, PLFA and ddPCR data were not correlated. In addition to piloting a new method to quantify soil fungal abundance, our findings indicate that, within fire-frequented pine savannas, recurrent fires do not consistently decrease total fungal abundance, and abundance changes are not contingent upon short-term fire history. This suggests that many fungi in fire-dependent ecosystems are fire-tolerant.
... Recurrent fires consume less fuel and produce less heat, which does not penetrate into soil as deeply as during high-intensity fires (Smith et al., 2016). Accordingly, fungal community shifts in pyrogenic ecosystems may be 'relatively modest' (Johnson & Miyanishi, 1995;Choromanska & DeLuca, 2001;Korb et al., 2004) and primarily be driven by indirect fire-induced changes in soil properties (e.g. pH shifts) and plant communities (e.g. ...
Pyrogenic savannas with a tree–grassland ‘matrix’ experience frequent fires (i.e. every 1–3 yr). Aboveground responses to frequent fires have been well studied, but responses of fungal litter decomposers, which directly affect fuels, remain poorly known. We hypothesized that each fire reorganizes belowground communities and slows litter decomposition, thereby influencing savanna fuel dynamics.
In a pine savanna, we established patches near and away from pines that were either burned or unburned in that year. Within patches, we assessed fungal communities and microbial decomposition of newly deposited litter. Soil variables and plant communities were also assessed as proximate drivers of fungal communities.
Fungal communities, but not soil variables or vegetation, differed substantially between burned and unburned patches. Saprotrophic fungi dominated in unburned patches but decreased in richness and relative abundance after fire. Differences in fungal communities with fire were greater in litter than in soils, but unaffected by pine proximity. Litter decomposed more slowly in burned than in unburned patches.
Fires drive shifts between fire‐adapted and sensitive fungal taxa in pine savannas. Slower fuel decomposition in accordance with saprotroph declines should enhance fuel accumulation and could impact future fire characteristics. Thus, fire reorganization of fungal communities may enhance persistence of these fire‐adapted ecosystems.
... In the western Central Hardwoods Region, there has been increased application of landscape-scale prescribed burning for woodland restoration due to both operational and ecological considerations. Operationally, large burn units allow greater area to be treated by minimizing labor requirements (e.g., reducing total fire break length and ignition points) per area burned and by allowing critical elements of burn plan prescriptions (e.g., wind speed, relative humidity, etc.) to be met during a single day (Johnson and Miyanishi 1995;Cleaves et al. 2000). From an ecological perspective, landscape-scale burning may better emulate historic fire patterns by allowing variability in fire behavior based on the spatial distribution in vegetation types and topo-edaphic characteristics (Stambaugh and Guyette 2008). ...
Landscape-scale prescribed burning may be appealing for natural community restoration due to operational efficiency and possible heterogeneity in fire effects across broad spatial scales. We monitored plant community responses for >15 years with variable prescribed fire frequencies applied across a Missouri Ozarks landscape stratified into distinct ecological site types. Through the study period, burning had no effect on the overstory tree density or basal area. Midstory stem densities decreased rapidly in periodically burned units and more gradually with annual fire. Burning increased total ground flora cover and the cover of forbs, grasses, and legumes. The effect of burning on species richness differed among site types, with increased species richness through time on exposed slopes. There was no effect of prescribed burning on species richness on two of three protected slope site types, and annual burning decreased species richness in upland waterways. Among the site types, the upland waterways had the most species associated with pre-burn communities. We conclude that 1) burning consistently increased cover of ground layer vegetation across the landscape, while decreasing the midstory stem densities; and 2) site type moderated ground flora richness response, with more pronounced effects of prescribed burning on exposed sites than on protected sites.
... Understanding how anthropogenic changes to fire regimes affect species' persistence is central to maintaining biodiversity in fire-prone ecosystems (Johnson and Miyanishi 1995;Keith et al. 2002;Allen 2008;Bennett et al. 2010;Penman et al. 2011). Some effects of changed fire regimes on plants, such as recovery from disturbance and seedling establishment, are relatively well understood (Knox and Clarke 2006;Sheuyange et al. 2005;Bradstock et al. 1996;Howe 1994). ...
In temperate ecosystems, fire management involving prescribed burning and wildfire suppression often causes a shift in fire season from hot and dry summer conditions to cooler, moister conditions in spring or autumn. The effects of this change on seed dispersal by wind after fire are unknown. However, calmer wind conditions and increased standing vegetation after fires in cooler seasons may reduce seed dispersal following fire. We studied seed dispersal in different seasons for a serotinous obligate-seeder, Callitris verrucosa, growing in a semi-arid environment in South Australia. We measured primary (wind-borne) and secondary (on-ground) seed dispersal during spring, summer and autumn, using empirical observations and modelling based on detailed measurement of wind characteristics. At comparable horizontal wind speeds, primary dispersal was greater in summer compared to spring and autumn. Secondary dispersal was similarly short in all three seasons when vegetation cover was high, but when cover was low, seeds travelled much further in summer than in the other two seasons. A shift in the seasonal timing of seed release can decrease dispersal distances of serotinous obligate seeders, which is likely to reduce gene flow and the ability to colonise new sites. This can lead to changes in population and community structures which may further affect fire patterns. These findings could be applicable to other serotinous obligate seeding plant species found in other families such as Proteaceae, Myrtaceae, Pinaceae and Cupressaceae.
... The potential for burn effectiveness to be a dynamic result of landscape condition highlights a greater need for an improved understanding of the processes under which landscapes transition between flammability states. There has been limited empirical quantification of the effect that patchiness within prescribed burns has on subsequent wildfire behaviour (Johnson and Miyanishi, 1995;Duncan et al., 2015), so further work is warranted to verify that fire simulation systems are accurately representing fire behaviour in areas that have been recently burnt. The ability to predict Type 1 patches has value outside of estimating the efficacy of burns in moderating fire risk. ...
Prescribed burning is a widely used strategy in forested landscapes to reduce the risk from wildfires to human lives and valued assets. The ability for managers to undertake prescribed burns is contingent on fuel, weather and operational constraints. In practice, not all areas nominated to be burnt get completed, and within burns that occur, not all the area is burnt. There has been limited research into rates of successful implementation of prescribed burns for fuel management and the degree to which the outcomes of prescribed burning are predictable. To better understand this, we undertook a quantitative analysis of prescribed burn outcomes in the State of Victoria, Australia between July 2009 and July 2015, investigating the likelihood of burns being completed and the time between nomination and completion. For those completed, we used Generalized Additive Models to investigate patterns of burn coverage, both for individual points within burns and aggregated to the burn level. We found a large proportion (29.6%) of scheduled prescribed burns were never burnt, and the time between nomination and completion was highly variable. The size of the nominated burn area was found to influence both the likelihood of completion and the likelihood of burns being postponed. Of burns that were completed, the proportion of area burnt was highly variable (mean 74%, median 84%). Patterns of burnt area were predictable: our point level model could predict the likelihood of any point within a burn being burnt with 66% accuracy from fuel type, aridity and temperature seasonality. The model was more confident in predicting what would remain unburnt than what would burn. Our burn level model explained 55% of variation in the proportion burnt from area weighted fuel type, average aridity, temperature seasonality and the size of the nominated burn area. An ability to foresee the outcomes of prescribed burn programs is important for managers in designing effective risk reduction programs.
... Tieto aplikácie môžu byť zamerané na stanovenie nebezpečenstva vzniku požiaru a vydávanie výstrah pred požiarom [9][10][11], posúdenie rizík výskytu požiaru v prírodnom prostredí [12,13], modelovanie správania sa požiarov vyskytujúcich sa v rôznych typoch vegetácie (napr. trávne porasty, lesy, kroviny), plánovanie taktických postupov likvidácie požiaru, výpočet emisií produktov horenia vznikajúcich pri požiari [1] a predvídanie dopadov požiaru z pohľadu viacerých aspektov [14,15]. ...
The publication has a form of a monograph summarizing theoretical knowledge, research results and practical experience of fire extinguishing in a natural environment. It is a collaborative work of authors working in the academic sphere and in the practice of crisis management and management and organization of rescue services.
It consists of twelve main chapters devoted to the characteristics, causes and factors influencing the behavior of fires in the natural environment; statistics on the occurrence of fires in the natural environment for the years 2000-2017; defining preventive measures in relation to the occurrence of fires in the natural environment; management and organization of work related to fire-fighting in the natural environment; the basic principle of extinguishing fires in the natural environment; description of the conditions and technology of fire extinguishing with water; a tactics of fire-fighting in the natural environment used in the Slovak Republic and abroad; a description of the technical and physical means used to fight the fires in the natural environment; extinguishing forest fires using aviation technology; defining the procedures for investigating the fires in the natural environment that are successfully used in practice abroad as well as the use of geoinformatics and information and communication technologies as a support tool for decision-makers and intervantion commanders.
The publication was created thanks to the financial support of two projects of the Cultural and Educational Agency of the Ministry of Education, Science, Research and Sports of the Slovak Republic. Especially, KEGA 012TU Z-4/2016 "Creating Innovative University Education Textbooks and Tools for Fire Protection and Safety and Integrated Safety Study Programmes" and KEGA 032PU-4/2018 "eLearning in the Urgent Health Care and Rescue Services Study Fields"
It offers a valuable source of knowledge for the students of the Rescue Services study field, studying not only at the Technical University in Zvolen.
It was created on the initiative and with considerable support of the Fire and Rescue Service members involved in the Ground Forest Fire Fighting Module Slovakia and is also devoted to them.
... The second is a reflection of the forest landscape age, or time since last fire of the various stands observed on the landscape (Weir et al. 1999 Wein & Maclean 1983, Payette 1992, Englemark et al. 1993, Caners & Kenkel 1998. Fire, climate and soils form a mutifactorial complex that defines the boreal ecosystem (Larsen 1980 Fuel moisture contenL and therefore weather, are of "prime importance,, when determining fire behaviour because of the level of heat energy needed to dry fuels (Johnson & Miyanishi 1995). The process of combustion requires a number of steps, the first ones being the heating of fuels to l00oC and the resulting evaporation of water present in the fuels. ...
No single process seems to characterize succession in the boreal forest; accumulating evidence suggests that it is subject to considerable variation resulting in multiple successional pathways. This study was undertaken to elucidate the structure and dynamics of major boreal forest stands in the Duck Mountain Provincial Park and Forest.
Detailed tree size and age data were obtained from each of 70 sampled stands located throughout the study area. Our approach involved reconstructing the initial post-fire composition of these stands, and classifying them into five stand types (Trembling Aspen, Balsam Poplar, White Spruce, Jack Pine, and Black Spruce). Successional pathways within these stand types were inferred through the careful examination of major stand dynamic features in 80-130 year old stands. A novel multivariate approach was used to examine the relationship between the initial cohort and the composition of the subsequent advance regeneration cohort. Variation in patterns of regeneration were examined universally and within each stand type. Timing of recruitment and major factors affecting secondary recruitment were also examined.
Our results reveal that landscape-scale succession in Duck Mountain does not result in convergence to a single self-perpetuating 'climax' forest community. Historically, many stands burned with sufficient frequency that canopy succession did not occur, resulting in long-term reestablishment of pre-fire canopy composition. In the absence of disturbance, the initial post-fire cohort composition may be maintained by gap dynamic processes. More often, however, recruitment of other species along with regeneration of the initial cohort species results in increased canopy diversity and complexity over time.
... In forest ecosystems faced with naturally occurring fires, in particular in boreal forest of Fennoscandia, Alaska, and Canada, an increasing awareness of the role of fire as an important ecological factor has led to the introduction of prescribed burning as restoration tool to imitate natural fires (Wikars 1992;Johnson and Miyanishi 1995;Haggstrom and Kelleyhouse 1996;Weber and Stocks 1998;New 2014). There are several studies that show that prescribed burning is an effective strategy to promote biodiversity (Hyvarinen et al. 2009), including saproxylic Hemiptera (Hägglund et al. 2015;Heikkala et al. 2017). ...
Saproxyly evolved several times independently within the insect order Hemiptera. Saproxylic Hemiptera are ancient groups of insects with approx. 5000 species described worldwide. They occur in all major zoogeographic regions but show the highest diversity in the tropics and subtropics. Species of this group are predominantly fungivores, sucking on fungal hyphae in deadwood, but also include a number of predators. They colonize a broad range of habitats, including deadwood structures of living trees as well as standing and downed logs of different diameters and decay stages. Also several pyrophilous species are known. Although most species have good dispersal capacities to find ephemeral deadwood structures, many species with reduced wings are known to occur in leaf litter, which provides a stable habitat, particularly in the tropics. Despite this numerical and ecological importance, our knowledge about the biology and ecology of these species is scarce. Most information is available from temperate and boreal forests, where many species are highly threatened due to intensive management and decreased fire frequency in fire-prone systems. It can be assumed that a high percentage of tropical species with their concealed lifestyle are still not discovered. More research on the ecology and habitat requirements of saproxylic Hemiptera is needed to protect this ancient and ecologically diverse group.
... Consumption of CWD, or woody fuel, contributes to postfrontal fire behaviour, including the rate of heat release and total energy output by the fire (Byram 1959;Rothermel 1983), convection column development (Potter et al. 2004), re-ignition potential and suppression/mop-up difficulty (Gould 2003;Page et al. 2013). Combustion of woody fuels also significantly influences first-order fire effects, such as soil heating (Hungerford et al. 1991;Burrows 1999;Reinhardt et al. 2001) and tree mortality (Burrows 1987;Johnson and Miyanishi 1995), and the volume and characteristics of atmospheric emissions from fire (Ottmar 2014;Weise and Wright 2014). Under favourable burning conditions, woody fuels may represent the bulk of biomass consumed by fire, particularly through the consumption of larger fuel particles with d . ...
Coarse woody debris (.0.6 cm in diameter) is an important component of the fuel complex in Australian eucalypt forests, influencing both fire behaviour, smoke production and post-fire ecological processes. We investigated how physical characteristics of woody fuel affected ignition and consumption during an experimental fire where the fuel complex characteristics, fire weather and fire behaviour varied within a narrow range. Decay status, bark condition, arrangement, suspension and extent of charring were classified for 2866 coarse woody fuel particles. We used generalised linear model (GLM) analysis to explain ignition success and the extent of consumption of individual particles, with a focus on larger diameter fuels (.7.5 cm in diameter), which comprised 83% of the woody fuel load and 94% of the woody fuel consumed during the flaming and smouldering stages of combustion. Ignition success was best explained by a model that included fuel arrangement (a surrogate of fuel proximity), suspension and decay status. The extent of fuel consumption was greater for pieces in advanced stages of decay, but suspension (inversely related) and arrangement (directly related) also affected the outcome. Forest management practices, previous fire history and other natural disturbances are likely to influence the distribution of pre-fire diameters and suspension classes that characterise large woody fuels at a site, and will therefore influence woody fuel consumption. This has practical implications for quantifying heat release and atmospheric emissions from fires burning in forests with different management histories. Additional keywords: coarse woody debris, fire behaviour, prescribed burning, smoke emissions.
... This fact has been pointed out in other communities (Baeza, 2001). It has also been suggested that variation in vegetation moisture might be responsible for these differences (Johnson and Miyanishi, 1995). Fuel moisture content is the main factor to control the fire spread rate in controlled burnings applied to young and mature Mediterranean gorse (dominated by Ulex parviflorus; Baeza et al., 2002b). ...
Forest fires are a recurrent disturbance in Mediterranean ecosystems, and the effect on the structure and
dynamics of vegetation may depend largely on fire severity. Our knowledge of how fuel consumption in
different species can be an indicator of fire severity is limited, and very few studies have covered this aspect.
Our initial work hypothesis is based on the existence of different ecological severities according to each species’ structural characteristics. The work aims to determine degree of severity by assessing biomass of different
species consumed during a fire. Three experimental fires in Ayora (eastern Iberian Peninsula) were conducted,
and subplots dominated by Rosmarinus officinalis, Quercus coccifera, Erica multiflora and Juniperus oxycedrus were selected. The soil temperature during fire was measured using thermocouples in each subplot. Average fuel consumption per species was determined by measuring the minimum diameter of the branches burned in each subplot. Our results indicate fire severity variability between species. The fuel consumption values within the subplots differed significantly between species. The largest were found for E. multiflora and R. officinalis if compared to Q. coccifera and J. oxycedrus. The temperature residence time above 40°C was very important for all species, but the longest occurred in E. multiflora and J. oxycedrus. Soil temperature and its duration were related to fuel type. The results show that fuel accumulation and its spatial distribution in the plant architecture, associated with reproductive strategy, are one of the most important traits in determining fuel consumption and soil temperature and can, therefore, play a key role in fire severity terms. These results indicate the importance of considering fuel structure and flammability of species as potential drivers of new fire regimes.
... Nonetheless, our ability to visualise its general dimensions (height, angle and length) makes a simple and efficient method to qualitatively assess fire intensity (Tolhurst and Cheney 1999). This allows practitioners to link fire behaviour with fire effects (Cheney 1981, Johnson andMiyanishi 1995) and efficiency of suppression methods and tactics (e.g., Plucinski, in preparation). (Table 5.13). ...
Mallee-heath vegetation occurring in semiarid and Mediterranean climates develops a vertically nonuniform
and spatially discontinuous fuel complex. The heterogeneity of the fuel layers sustaining fire
propagation leads to fire behaviour characterised by nonlinear dynamics where small changes in the drivers
of fire spread lead to large changes in observed fire behaviour. Within this fuel complex fire behaviour is
not just determined by the effect of fuels and weather, but to a large extent determined by the
interactions between those variables and the structure of the flame front. The aim of this research is to
understand these nonlinear processes and ultimately fire behaviour in this fuel type through a series of
experimental fires conducted in the Ngarkat Conservation Park, South Australia from 2006 to 2008.
Fuel complexes in the experimental burning program comprised mallee and heath vegetation with ages
(time since fire) ranging from 7 to 50 years old. Dominant overstorey mallee vegetation comprised
Eucalyptus calycogona, E. diversifolia, E. incrassate and E. leptophylla. Fuel complex structure was
assessed through destructive sampling and visual hazard assessment methods. Vertical wind profiles (from
10-m above ground to ground height) were characterised for each fuel complex. A total of 67 fires were
completed. The range of fire environment conditions within the experimental fire dataset were: air
temperature 15 to 39°C; relative humidity 7 to 80%; mean 10-m open wind speed 3.6 to 31.5 km/h; Forest
Fire Danger Index 1.7 to 46. Fire behaviour measurements included rate of spread, flame geometry,
residence time and fuel consumption. Total fuel load ranged from 3.8 t/ha in young (7-year old) mallee to
10 t/ha in mature stands. Measured rate of spread ranged between 50 and 3310 m/h with fireline intensity
between 144 and 11,000 kW/m.
The dataset provided an insight into the mechanisms that allow the development of a coherent flame front
necessary to overcome the fine scale fuel discontinuities that characterise the semi-arid mallee-heath fuel
types and allow self-sustained fire propagation. The dataset was also used to develop models to predict
the likelihood of fire propagation (go/no-go threshold), surface fire rate of spread, crown fire spread
regime and rate of spread. The models will be used in planning and conducting prescribed fire operations
and supporting wildfire suppression decision-making in mallee-heath fires.
... Further, BNP needs to increase the resolution of monitoring fire severity and intensity, possibly through mapping the Nonnalized Burn Ratio (t.NBR), an index derived by differencing pre-and post-fire values of Bands four and seven reflectance obtained by the Landsat Thematic Mapper (Key and Benson at http://nnnsc.usgs.gov/researchindbr.htrn). Finally, as recommended by Johnson and Miyanishi (1995), fire prescriptions and resulting ecological effects should be more carefully specified and monitored. This will require more work to differentiate effects between spring season, high intensity fires (rapid rates of spread, low fuel consumption) and mid-summer drought-driven fires where high severities (smoldering combustion of duff and heavy fuel) may occur. ...
The Banff National Park (BNP) management plan stipulates that Parks Canada maintain 50% of the long-tenn fire cycle through planned ignition if required. Landscape-level knowledge of the 10ng-tenn range of variability of fire regime attributes including fire cycle, ignition source, intensity, severity, and seasonality was used to adaptively restore fire. Plot measurements of regime attributes were used to aggregate ecological land classification ecosite types into fire groups, or areas of similar fire regime. Stand origin mapping was also used to model fire cycles as a function of mountain terrain attributes. Predicted fire regime characteristics over space and time provide a basis for large-area, high-intensity prescribed bwns. From 1983 to 2003, BNP burned ,.,17,000 ha (~1 , 000 acres), mostly with spring or fall season aerial ignition. Most bums were done along the eastern park boundary, and one required machine thinning of a >2 km (1.3 mile) wide shaded fuel break. Comparing predicted long-tenn fire attributes versus observed prescribed fire patterns showed that restoration was biased towards avoiding burning long fire cycle areas (> I 00 years). Prescribed fires have killed fewer trees than predicted from a model of historic fire intensity/severity extrapolated to current stand ages. Further, few areas have been burned in midsummer although much of the historic bum area may have occurred during this period. Future management and research directions may include better application of First Nation's traditional ecological knowledge, burning longer fire cycle areas in midsummer , remote sensing of fire effects, and differentiating fire effects due to fire intensity (flaming combustion) versus severity (smoldering combustion).
... Fire behavior in these forests is a crucial component of the development of management strategies for these species (Johnson and Miyanishi, 1995). Successful prediction of fire behavior in these stands has been the source of much investigation (Quintilio et al., 1977;Stocks, 1987Stocks, , 1989Stocks et al., 2004). ...
The 'Spring Dip' in conifer live foliar moisture content (LFMC) has been well documented but the actual drivers of these variations have not been fully investigated. Here we span this knowledge gap by measuring LFMC, foliar chemistry, foliar density and foliar flammability on new and old foliage for an entire year from both Pinus resinosa (red pine) and Pinus banksiana (jack pine) at a site in Central Wisconsin. We found that needle dry mass increased by up to 70% in just three weeks and these increases were manifested as strong seasonal variations in foliar moisture content and foliar density. These needle dry mass changes were driven by an accumulation of starch in old foliage, likely resulting from springtime photosynthesis onset, and also by accumulations of sugar and crude fat in new needles as they fully matured. Foliar starch, sugar and crude fat content accounted for 84% of the variation in foliar density across both species. Flammability differences were also strongly related to changes in foliar density, where density accounted for 39% and 25% of the variations in foliar time-to-ignition of jack pine and red pine respectively. Finally, we use the computational fluid dynamics-based wildland fire model FIRETEC to examine how these foliar physio-chemical changes may influence wildland fire behavior. Under the lowest canopy density and windspeed, simulated fires in dormant condition stands did not propagate as crown fires while spring dip stands successfully spread as crown fires as a result of the higher potential energy content of the canopy. Simulated wildland fire spread rates increased by as much as 63%, nominal fireline width increased by as much as 89% and active fire area more than doubled relative to dormant season fuel conditions and the most significant changes occurred in areas with low canopy cover and low within-tree bulk density. Our results challenge the assumption that live conifer foliage flammability is limited only by its water content; this study suggests a new theory and an expanded view of the factors that dominate live fuel flammability and that subsequently influence larger scale wildland fire behavior.
... It is important to conceptualize disturbance as a variable and to take a mechanistic approach to understanding its influence. For example, Johnson and Miyanishi (1995) have shown how to model and describe the wide range of fire effects quantitatively. In this section, we discuss several disturbance characteristics that have special relevance to restoration. ...
... It is important to address the effect of slope on fire spread as topography has a pronounced effect on fire behavior (see for example Noble and others 1980;Forestry Canada 1992;Mendes-Lopes and others 2003;Viegas 2004;Zhou and others 2007). Our results on rate of spread of fire agree with literature (Cheney and others 1993;Johnson and Miyanishi 1995;Burgan and others 1998;Piñol and others 1998;Baeza and others 2002), and support a negative relationship with moisture contents of fuels. On the contrary, because of the little amount of dead fuels, the effect of dead fuel moisture content on fire behavior has not been addressed in this study. ...
... Localized lethality or necrosis of the vascular cambium results from the physical transfer of heat greater than the tolerance threshold interaction of temperature and duration of exposure (Johnson and Miyanishi 1995;Dickinson and Johnson 2004;Jones et al. 2006). After cambial cell death, two dynamic processes result in scar formation: compartmentalization and wound closure. ...
Fire scars are initiated by cambial necrosis caused by localized lethal heating of the tree stem. Scars develop as part of the linked survival processes of compartmentalization and wound closure. The position of scars within dated tree ring series is the basis for dendrochronological reconstruction of fire history. Macroanatomical features were described for western larch, ponderosa pine, and Douglas-fir injured by fire in 2003 and harvested in 2011 at the Lolo National Forest near Missoula, Montana, USA. Bark scorch did not necessarily indicate the formation of a scar. Wound-initiated discoloration inward from the scar face was bounded tangentially by reaction zones. In western larch, the transition between earlywood and latewood was much less abrupt in woundwood rings than in rings formed the same year but not associated with a scar. Wood formed the year after injury contained tangential rows of resin ducts in the earlywood. Compartmentalization plays a key role in resisting the spread of infection and the loss of healthy sapwood and heartwood. Wound closure restores some degree of circumferential continuity of the vascular cambium and reinforces stem structure. The terminology presented here should facilitate communication among tree pathologists, wound anatomists, and dendrochronologists.
... In many ecosystems, lack of heterogeneity in prescribed fire has been a concern of scientists and fire practitioners for some time (Brockett et al., 2001;Fuhlendorf et al., 2006;Johnson and Miyanishi, 1995;Parr and Andersen, 2006;Van Wilgen et al., 2004). This concern likely extends back to the equilibrium vs. nonequilibrium paradigm shift that now also provides support for the theory of fire heterogeneity (Parr and Brockett, 1999;van Wilgen et al., 2007;Wu and Loucks, 1995) and its influence on biological diversity. ...
Reduction of fire hazard is becoming increasingly important in managed landscapes globally. Fuels reduction prescribed burn treatments are the most common form of reducing fire hazard on landscapes around the world but often result in homogenized fuel age structures and habitats. Alternatively, the size of unplanned fires, and hence fire hazard, can be reduced by controlling the size and patterning of fuels treatments in a patch mosaic arrangement on landscapes. Patch mosaic burning is being implemented globally as a means to increase heterogeneity to mimic natural fire regime results. Funding for prescribed fire programs is often justified primarily on hazardous fuels reduction with secondary consideration given for ecological effectiveness, which can be increased by particular fire mosaic patterns in some systems. The question we address is: Which of two prescribed fire treatment regimes, fuels reduction or patch mosaic burning, reduces fire hazard most effectively? We address the question using computer simulation modeling on synthetic landscapes representing both fire regime treatments. Treatment scale was important. Among fuel reduction treatments, large blocks burned less area than small blocks. For the mosaic treatments, small blocks reduced fire size the most (out of all treatments) and had the least variance in area burned. It is possible to reduce fire hazard and to provide heterogeneous age fuels structure on the landscape, simultaneously benefiting humans and many native fire-dependent species requiring mosaic habitat patterns.
... This increased tolerance for wildfire, especially during moderate fire years and shoulder seasons, will require continued public education on the ecological role of fire, as well as changes in policies and professional incentives for forest managers. Cutting trees, whether commercially or pre-commercially, can emulate fire effects on tree density and layering, but it cannot reproduce the effects of fire on nutrient cycling, snag creation, surface fuel reduction, mineral seedbed preparation, and regenerating associated shrub and herb vegetation (Johnson 1992, Johnson andMiyanishi 1995). ...
More than a century of forest and fire management of Inland Pacific landscapes has transformed their successional and disturbance dynamics. Regional connectivity of many terrestrial and aquatic habitats is fragmented, flows of some ecological and physical processes have been altered in space and time, and the frequency, size and intensity of many disturbances that configure these habitats have been altered. Current efforts to address these impacts yield a small footprint in comparison to wildfires and insect outbreaks. Moreover, many current projects emphasize thinning and fuels reduction within individual forest stands, while overlooking large-scale habitat connectivity and disturbance flow issues. We provide a framework for landscape restoration, offering seven principles. We discuss their implication for management, and illustrate their application with examples. Historical forests were spatially heterogeneous at multiple scales. Heterogeneity was the result of variability and interactions among native ecological patterns and processes, including successional and disturbance processes regulated by climatic and topographic drivers. Native flora and fauna were adapted to these conditions, which conferred a measure of resilience to variability in climate and recurrent contagious disturbances. To restore key characteristics of this resilience to current landscapes, planning and management are needed at ecoregion, local landscape, successional patch, and tree neighborhood scales. Restoration that works effectively across ownerships and allocations will require active thinking about landscapes as socio-ecological systems that provide services to people within the finite capacities of ecosystems. We focus attention on landscape-level prescriptions as foundational to restoration planning and execution.
... If advance white pine regeneration is present, however, seedlings and saplings may be vulnerable to fire. White pine seedlings and saplings do not resprout after being top-killed by fire and their thin bark makes it likely that fire would kill the cambium [20]. Blankenship and Arthur [19] reported that a single prescribed fire removed all white pine < 2.0 cm dbh from oak-pine forests in eastern Kentucky and caused significant mortality up to 6.0 cm dbh, but they also noted abundant post-burn colonization of white pine. ...
We examined the effects of prescribed fire on white pine (Pinus strobus) advance regeneration in small experimental plots in mixed hardwood-pine forests in southwestern Virginia during the fall and spring. Fires killed all newly germinated seedlings in both spring and fall. Saplings (ranging from 0.7 - 3.4 m in height) all suffered some degree of crown scorch, but sapling survival was higher on plots burned in the fall (54%) compared to those burned in the spring (20%). After one growing season following the fires, seedling density had recovered to a level similar to that of control plots for fall burns, but was still significantly lower than control plots for spring burns. After one growing season, the amount of crown mortality for saplings was reduced with increasing height and root collar diameter. Height growth of saplings after one growing season following fires was not different between burned and control plots. Fall burns may be less detrimental to white pine regeneration because of reduced mortality to saplings and by providing microsite conditions during the period of seed rain that are conducive to recover seedling regeneration.
... Woody fuels can burn for long periods of time, sometimes even months after the passage of the fire front, increasing difficulty of fire suppression and mop-up (Cheney 1981;Lawson et al. 1997) and the potential for re-ignition following the fire (Pyne et al. 1996;Lawson et al. 1997). Combustion of woody fuel plays a significant role in determining first-order fire effects, through soil heating and tree mortality associated with the heating of tree boles and superficial roots (Burrows 1987a;Cheney 1990a;Johnson and Miyanishi 1995;Whelan 1995;McCaw et al. 1997). ...
The relationship between woody fuel consumption and fireline intensity was assessed using data collected at controlled fires and wildfires in south-western Western Australia, central Victoria and south-eastern New South Wales. The combined dataset consisted of fires in a range of dry eucalypt forests. Fire behaviour varied from slow, self-extinguishing prescribed burns to intense, fast—moving fires burning under conditions of extreme fire danger. Fireline intensity ranged from 50 kW m−l to
... Fuel consumption was measured as the difference in dry weights between pre-burn and post-burn fuel. Assuming a standard energy content for longleaf pine needle fuel (19,647 kJ/kg) (Reid and Robertson 2012), these data were used to calculate the heat released per unit area (kJ/m 2 ) (Johnson and Miyanishi 1995) for each experimental fire. We then used heat released per unit area and the flaming residence time to calculated reaction intensity (rate of energy release per unit area; kW/m 2 ) (DeBano et al. 1998). ...
The resprouting ability of woody plants in frequently burned ecosystems may be influenced by the season and method of topkill. We conducted an experiment to test for the effects of season and method of topkill on aboveground biomass, belowground biomass, and mortality of hardwoods found in a southeastern U.S. pine-grassland. We predicted that topkill occurring during the growing season and topkill by fire would have greater negative impacts on resprouting and root growth and result in greater mortality. We conducted a shadehouse experiment in north Florida in which we applied topkill treatments (burn, clip, and no-topkill) in three seasons (dormant, early growing, and mid growing) to Quercus nigra (water oak) saplings. Plants were destructively sampled 12 months post-treatment to measure aboveground and belowground biomass. Saplings topkilled in the early and mid growing seasons had reduced growth and greater mortality one-year post-treatment compared to plants topkilled in the dormant season. While there was no difference in one-year post-treatment biomass or mortality of saplings between the two methods of topkill, clipped plants had more stems and shorter average stem height than plants topkilled by fire. Root growth continued despite topkilling for all seasons and was greatest for no-topkill plants. These results suggest that while topkill reduces biomass, hardwoods have evolved to maintain belowground biomass reserves, enabling genets to resprout following subsequent topkilling and to persist through frequent disturbances.
... Understanding how fuels affect fire behavior and desired fire effects is a necessary component of using prescribed fire (Johnson and Miyanishi 1995). Fire behavior is affected by both the chemical (intrinsic) and physical (extrinsic) properties of fuels (Pyne 1984). ...
The establishment of sustainable, low-intensity fire regimes is a pressing global challenge given escalating risk of wildfire driven by climate change. Globally, colonialism and industrialisation have disrupted traditional fire management, such as Indigenous patch burning and silvo-pastoral practices, leading to substantial build-up of fuel and increased fire risk. The disruption of fire regimes in southeastern Tasmania has led to dense even-aged regrowth in wet forests that are prone to crown fires, and dense Allocasuarina-dominated understoreys in dry forests that burn at high intensities. Here, we investigated the effectiveness of several fire management interventions at reducing fire risk. These interventions involved prescribed burning or mechanical understorey removal techniques. We focused on wet and dry Eucalyptus-dominated sclerophyll forests on the slopes of kunanyi/Mt. Wellington in Hobart, Tasmania, Australia. We modelled potential fire behaviour in these treated wet and dry forests using fire behaviour equations based on measurements of fuel load, vegetation structure, understorey microclimate and regional meteorological data. We found that (a) fuel treatments were effective in wet and dry forests in reducing fuel load, though each targeted different layers, (b) both mechanical treatments and prescribed burning resulted in slightly drier, and hence more fire prone understorey microclimate, and (c) all treatments reduced predicted subsequent fire severity by roughly 2-4 fold. Our results highlight the importance of reducing fuel loads, even though fuel treatments make forest microclimates drier, and hence fuel more flammable. Our finding of the effectiveness of mechanical treatments in lowering fire risk enables managers to reduce fuels without the risk of uncontrolled fires and smoke pollution that is associated with prescribed burning. Understanding the economic and ecological costs and benefits of mechanic treatment compared to prescribed burning requires further research.
The information about physics and variables that influence a fire’s development comes from research, i.e., the fire tests provided for this reason in various scales and using various standardized and non-standardized test methods as well as advanced technologies.
The aim of this monograph was to provide theoretical knowledge about the fire investigation as a scientific discipline, the processes and methods applied in fire investigation practice in general and specifically in the Slovak Republic. We focused both, as enclosure fires as wildfires
and introduced the theoretical background of fire investigation of both.
In the monograph, there are introduced the results of research provided at the Department of Fire Protection, Faculty of Wood Sciences and Technology, Technical University in Zvolen, Slovakia, in the framework of research projects implemented. This research focuses development of new non standardized testing methods and apparatus to acquire new fire properties of material which lead to more specific and precise evaluation of those material in view of fire hazard. This information is a key input parameter into the fire modelling.
When fire hypotheses (potential fire scenarios) are identified, the process of its validation starts. To do it, computer-aided modelling is an advanced tools to test the validity of the hypotheses when changing the input parameters of material but also the environment.
To specify the hypotheses, i.e., the potential fire scenarios and to specify the reasons of fire ignition and further spread, the implementation of decision support tools is an advanced procedure, which allows to prioritize all the considered hypotheses and scientifically prove the appropriateness of the choice as well as the validity of each of the hypotheses.
This work was supported by the Slovak Research and Development Agency under the contract No. APVV-17-0005-0005 (35 %) and contract No. SK-CN-21-0002 (35 %); and project “Progressive research of performance properties of wood-based materials and products” (LignoPro); ITMS 313011T720, supported by the Operational Programme Integrated Infrastructure (OPII) funded by the ERDF (30 %).
It is published on the 25th anniversary of the Department of Fire Protection, Faculty of Sciences and Technology, Technical University in Zvolen.
Previous research has paid little attention to the multiple meanings of the concept of forest restoration. To gain a more comprehensive view of forest restoration, this paper compares the US forest restoration debate of the 1940s and 1990s, in the disciplines of ecology and forestry. The paper focuses on historical approaches to pasts and futures, and on “sociotechnical imaginaries” providing societal legitimacy to restoration ventures. Historical scientific papers constitute the paper’s empirical sources. The analysis shows that, among ecologists and foresters, forest restoration of the 1940s was oriented towards efficiency and challenges such as wood demands during World War II, whereas restoration of the 1990s was oriented towards conservation and environmental challenges. The approaches of the 1940s′ ecologists and foresters seem motivated by a sociotechnical imaginary connecting forest restoration to societal progress, whereas the approaches of their 1990s′ counterparts seem motivated by a sociotechnical imaginary connecting forest restoration to the task of mitigating society’s impacts. Based on the conclusions, it is argued that future research on forest restoration would benefit from comparing the idealized pasts of both yield- and conservation-oriented conceptions of forest restoration.
Effects of Prescribed Fire on Wildlife and Wildlife Habitat in Selected Ecosystems of North America
Fire management of California shrublands has been heavily influenced by policies designed for coniferous forests, however, fire suppression has not effectively excluded fire from chaparral and coastal sage scrub landscapes and catastrophic wildfires are not the result of unnatural fuel accumulation. There is no evidence that prescribed burning in these shrublands provides any resource benefit and in some areas may negatively impact shrublands by increasing fire frequency. Therefore, fire hazard reduction is the primary justification for prescription burning, but it is doubtful that rotational burning to create landscape age mosaics is a cost effective method of controlling catastrophic wildfires, There are problems with prescription burning in this crown-fire ecosystem that are not shared by forests with a natural surface-fire regime, Prescription weather conditions preclude burning at rotation intervals sufficient to effect the control of fires ignited under severe weather conditions. Fire management should focus on strategic placement of prescription burns to both insure the most efficient fire hazard reduction and to minimize the amount of landscape exposed to unnaturally high fire frequency. A major contributor to increased fire suppression costs and increased loss of property and lives is the continued urban sprawl into wildlands naturally subjected to high intensity crown fires. Differences in shrubland fire history suggest there may be a need for different fire management tactics between central coastal and southern California. Much less is known about shrubland fire history in the Sierra Nevada foothills and interior North Coast Ranges, and thus it would be prudent to not transfer these ideas too broadly across the range of chaparral until we have a clearer understanding of the extent of regional variation in shrubland fire regimes.
We analyzed the long-term effects of fuels reduction treatments around a wildland-urban interface located in the Blue Mountains near La Grande, Oregon. The study area is targeted for fuels reduction treatments on both private and federal lands to reduce the risk of severe wildfire and associated damage to property and homes. We modeled a number of hypothetical fuel treatment scenarios and examined the resulting changes in fuel characteristics, fire potential, and stand structure over time. Aggressive thinning alternatives showed significant reductions in stand characteristics that contribute to severe crown fires, such as height to live crown and crown bulk density for the landscape as a whole. However, simulations with extensive thinning showed larger overall flame lengths and torching compared to a no management scenario. Significant changes in stand structure and other characteristics were noted for the thinning versus no management scenarios. Work is ongoing to refine the simulation methods and test a wider range of treatment alternatives. The study motivated a discussion of the long-term problem of managing forest fuels in areas like the Blue Mountains.
We quantified the combustion characteristics of bison fecal pats following three prescribed grassland fires conducted during three different seasons on an Oklahoma tallgrass prairie. We compared heat per unit area, rate of energy consumption and duration of combustion of the burning fecal pats with fireline intensity, reaction intensity and heat per unit area of the fires. Environmental conditions at the time of burning determined the intensity of the fire in the grassland fuels. However, we found no correlation between grassland fire behavior and fecal pat combustion characteristics, suggesting that grassland fuels and fecal pats respond differently to several environmental factors. The heat released per unit area of fecal pat was extreme in each fire. The results suggest the flux of heat created by combusting bison fecal pats may potentially alter patterns of soil resources. If so, this should contribute to species richness and spatial heterogeneity in tallgrass prairie in a manner similar to other small-scale disturbances.
Genetic algorithms are useful techniques for generating statistical designs when standard factorial and response surface methods either cannot be easily applied or they perform poorly. These situations often occur when the design space is highly constrained and irregular, we are using nonstandard models, or the criteria for design evaluation are complicated. We consider statistical designs for experiments involving mixture variables and process variables, some of which are noise variables that cannot be controlled under general operating conditions. For these types of experiments, it is customary to fit a response model combining mixture, process, and noise variables and to derive a model for the mean response and a model for the slope of the response. When considering experimental designs to use for these situations, low prediction variances for the mean and slope models are desirable. We evaluate some standard mixture-process variable designs with respect to these criteria and demonstrate how an experimenter can create designs with improved scaled prediction variance (SPV) properties using a genetic algorithm.
Landowners and managers, municipalities, the logging and livestock industries, and conservation professionals all increasingly recognize that setting prescribed fires may reduce the devastating effects of wildfire, control invasive brush and weeds, improve livestock range and health, maintain wildlife habitat, control parasites, manage forest lands, remove hazardous fuel in the wildland-urban interface, and create residential buffer zones. In this practical and helpful manual, John R. Weir, who has conducted more than 720 burns in four states, offers a step-by-step guide to the systematic application of burning to meet specific land management needs and goals.
In an old-growth longleaf pine population in which all trees of at least 2 cm in dbh were mapped and tagged, the population was of uneven age and size; tree size correlated positively with tree age. Large or old trees were only loosely aggregated, forming a background matrix that filled the forest. Juvenile trees were highly aggregated, located in areas of low adult densities. Recruitment thus occurs primarily within open spaces created by the deaths of large trees. Variable time lags may occur before the colonization of open spaces, however, because of temporal variation in seed production and occurrence of summer ground fires. Recruitment within the mapped plot has occurred frequently for at least the past 250 yr. Temporal variation in adult mortality and recruitment into open spaces, coupled with strong negative interactions between cohorts of different ages, appears likely to produce alternating phases of population growth and decline that are highly variable in length and magnitude. An upper bound to population size occurs when all available space is filled with trees; but no lower bound exists, and extinction probabilities may be increased at very low densities. The population is buffered from declines to very low densities, however, by the tendency for small trees to recruit into openings created by the deaths of adults. Longleaf pine possibly maintains the environment in an open state suitable for its own regeneration by transmuting a localized disturbance (lightning) into a widespread disturbance (ground fires). Fire facilitation results in an extended, but indefinite, increase in the persistence of environmental conditions in which longleaf pine, but no other tree species, can survive and reproduce. -from Authors
A model is presented for predicting mortality of conifers after wildfire. The model requires stand data inputs and is linked with a mathematical fire behavior model that calculates fireline intensity. Fraction of crown volume killed is calculated for each species in a stand based on mensurational data. Duration of lethal heat at the base of trees is calculated from fuel consumption and burning time values. Fraction of crown volume killed and the ratio of critical time for cambial kill to duration of lethal heat are independent variables in a function that calculates probability of mortality. The model produces reasonable estimates of stand mortality for fire and site characteristics found in the northern Rocky Mountains, USA. It has a broad resolution appropriate for use in fire management planning and has potential applications for coniferous forests throughout the United States.
Fire scar and tree growth chronologies (1700 to 1905) and fire statistics (since 1905) from Arizona and New Mexico show that small areas burn after wet springs associated with the low phase of the Southern Oscillation (SO), whereas large areas burn after dry springs associated with the high phase of the SO. Through its synergistic influence on spring weather and fuel conditions, climatic variability in the tropical Pacific significantly influences vegetation dynamics in the southwestern United States. Synchrony of fire-free and severe fire years across diverse southwestern forests implies that climate forces fire regimes on a subcontinental scale; it also underscores the importance of exogenous factors in ecosystem dynamics.
It is almost dogma that the boreal forest in North America is a fire-dependent forest, yet ecologists often do not consider in any technical detail how forest fires produce effects on individual plants and on plant populations. Consequently, the causal connection between the behaviour of fire and its ecological consequences is poorly understood. This book sets out to correct this deficiency by assembling the relevant studies of fire intensity, rate of spread, fuel consumption, fire frequency and fire weather in the North American boreal forest. The central thesis is that the North American boreal forest has at least four wildfire characteristics that are important in understanding the dynamics of its plant populations: the large size of the burns with respect to dispersal distances, the short recurrence time of fire with respect to tree lifespans, the high mortality of plants due to the predominance of crown fires, and a good germination surface due to the large area of the forest floor which is covered by ash.
Fall seed-dispersing species, birch (Betulapapyrifera Marsh.), alder (Alnuscrispa (Ait.) Pursh), and black spruce Piceamariana (Mill.) B.S.P.), and summer-seeding species, aspen (Populustremuloides Michx.), balsam poplar (P. balsamifera L.), feltleaf willow (Salixalaxensis (Anderss.) Cov.), Scouler willow (Salixscouleriana Barratt), and Bebb willow (Salixbebbiana Sarg.), were artificially sown on seedbeds created by experimental burning in the upland black spruce/feather moss forest types in interior Alaska. At least 40% of the seeds dispersed in the fall had germinated before dispersal of summer seeds began. Germination occurred on moderately and severely burned seedbeds but not on scorched and lightly burned surfaces. Seedling survival occurred almost exclusively on severely burned surfaces. After 3 years, 82% of the plots containing some severely burned surfaces and sown with seeds from species seeded in the fall were stocked whereas 32% of the plots sown with species seeded in the spring and with the ...
This article deals with several ways of describing forest fires and their limitations. The simplest and oldest way is by simple verbal description. Then came the combination of rate of spread and resistance to control. The best quantitative measure of fire behaviour, however, is the rate of energy output per unit of fire front, quoted in conjunction with the linear rate of spread. If the full benefits of advances in fire control technology are to be realized, wider use of the energy output concept will probably be necessary, first among fire researchers and eventually among fire control people.
A relation between fire behavior and crown scorch height is derived from measurements on 13 experimental outdoor fires. The range of data includes fire intensities from 16 to 300 kcal/s-m, and scorch heights from 2 to 17 m. The results agree with established theory that scorch height varies with the 2/3 power of line-fire intensity. The effects of air temperature and wind speed on scorch height are treated as well. The derived relations could be useful to those interested in prescribed burning under a crown canopy, ecological response of trees to fires of varying intensity, and timber losses following forest fires.
Plant species which have survived fires for tens of thousands of years may not only have selected survival mechanisms, but also inherent flammable properties that contribute to the perpetuation of fire-dependent plant communities. This concept goes by beyond the commonly accepted fire climate-fuel moisture basis of wildland fire occurrence. Plant communities may be ignited accidentally or randomly, but the character of burning is not random. The following hypothesis treats this interaction between fire and the ecosystem: Fire-dependent plant communities burn more readily than non-fire-dependent communities because natural selection has favored development of characteristics that make them more flammable. The hypothesis was experimentally derived following laboratory combustion tests with litter of eucalyptus (Eucalyptus obliqua L'Herit), ponderosa pine (Pinus ponderosa Laws.), and tropical hardwood leaves.
To most early ecologists, the ‘natural’ ecosystem was the community that would be reached after a long period without large-scale disturbance (fire, windstrom, etc.). More recently, it has been realized that in most areas some type of large-scale disturbance is indigenous, and must be included in any realistic definition of ‘naturalness’. In some areas an equilibrium may exist in which patchy disturbance is balanced by regrowth, but in others equilibrium may be impossible because (1) individual disturbances are too large or infrequent; (2) ephemeral events have long-lasting disruptive effects; and/or (3) climate changes interrupt any movement toward equilibrium that does occur. Examples of non-equilibrium ecosystems include the African savannas, the Big Woods of Minnesota, the lodgepole pine forests of Yellowstone National Park, and possibly the old-growth Douglas-fir forests of the Pacific Northwest.Where an equilibrium does not exist, defining the ‘natural’ vegetation becomes much more challenging, because the vegetation in any given area would not be stable over long periods of time even without man's influence. In many areas it may be unrealistic to try to define the natural vegetation for a site; one must recognize that there are often several communities that could be the ‘natural’ vegetation for any given site at any given time.
Takes a process-response approach to fire behaviour and its effect on trees and tree populations, concentrating on studies which have coupled the quantitative physical understanding of fire behaviour. After the introduction, a chapter on fire and climate argues that the position of the Arctic airstreams influences the seasonal and geographical extent of fire outbreaks. The next four chapters discuss the relationships between physical processes of fire behaviour and population responses; fire spread and its dependence on fuel, weather and topography, with implications for seed dispersal and mortality; heat output from the fire front and its effect on plant mortality; consumption of organic material and its effect on recruitment and mortality; and fire recurrence and its effect on survivorship and forest age patterns. The last chapter attempts to explain observed tree age distributions in the boreal forest. -J.W.Cooper
Charcoal stratigraphic analysis and fire scars on red pine (Pinus resinosa) trees were used to determine spatial and temporal occurrence of fire in 1 km2 of old-growth mixed conifer/hardwood forests in northwestern Minnesota. Charcoal was analyzed year by year on petrographic thin sections from annually laminated sediments of three small (≤5 ha) lakes having adjacent catchments. Dated fire scars (n = 150) from recent treefalls provided an independent record of the spatial patterns of past burns. Sedimentology of the varved sediments, water-balance models that use 150 yr of instrumental temperature and precipitation data, and published data were used to identify climate changes in separate studies, and they were used in this study to examine the possible connection between changing fire regimes and climate change. Fire-history data were used to show the changing probability of fire with time since the last fire and the effects of spatial variance (slope and aspect) on the distribution of fires through time. Over the last 750 yr, fire was most frequent (8.6 ± 2.9-yr intervals) during the warm/ dry 15th and 16th centuries. Intervals were longer (13.2 ± 8.0 yr) during cooler/moister times from AD 1240 to 1440 and since 1600 (the Little Ice Age). The fire regime during the Little Ice Age consisted of periods during the mid-18th and mid-19th centuries characterized by longer fire intervals of 24.5 ± 10.4 and 43.6 ± 15.9 yr, respectively, and short-term warm/dry periods from 1770 to 1820 and 1870 to 1920 when intervals were 17.9 ± 10.6 and 12.7 ± 10.1, respectively. The probability of fire increased through time, probably in step with fuel accumulation. South- and west-facing slopes burned more frequently than did north and east aspects. Fire suppression began in 1910. During warm periods, probability of fire was sufficiently high that a continuous litter layer was all that was necessary for fire to spread and scar trees. During cool and moist times fire was most-likely to occur in years with higher moisture deficits. The combined methods for fire-history analysis provided a more detailed spatial and temporal documentation of fire regimes than has previously been possible from analysis of fire scars or of charcoal counts derived from fossil pollen preparations. Results support predictions of particle-motion physics that thin sections record a local fire history. Because climate varies continuously, the responsiveness of disturbance regime to short- and long-term climatic change suggests caution in the interpretation of fire frequencies that derive from space/time analogies or extrapolation from short-term data.
The thermal decompositions of forty-three typical forest fuels have been characterized up to 500°C. The fuels studied include foliage, wood, small stems, and bark. Evolved gas analysis gave quantitative measurements of the oxygen stoichiometry for combustion of volatile pyrolysis products. Oxygen consumption by the volatiles is highly correlated to their calculated heats of combustion. Char heats of combustion were also determined and found to be very similar for the fuels studied. These data were used to partition total heat of combustion into flaming and glowing components. Addition of combustible gas analysis to other thermal analysis techniques provides a more complete comparison of thermal behavior over a wide temperature range. Forest Sci. 28:404-420.
We have constructed a heat budget for the transient heating of cones showing that there is a logarithmic relationship between the time (sec) to serotinous cone opening, releasing viable seeds, or cone ignition and temperature (°K) in the convective column above a fire. The rate of opening at a given temperature is controlled by a thermal time constant which is the ratio of the thermal resistance of a cone to convection, to the heating capacity of a cone by conduction. The observed times to cone opening and ignition fit the logarithmic relationship as predicted by the heat budget model. In order to understand the fire behaviour that results in cone opening and ignition, we changed the variables of temperature and time to the fire behaviour variables of fire intensity (kW/m) and fire rate of spread (m/min). Cones borne high in the canopy open in fires with low rates of spread and high fuel consumption, where intensity = rate of spread × fuel consumption × heat of ignition, but not when the rate of spread is high and fuel consumption low.
Mortality in a longleaf‐slash pine stand following a winter fire
- Storey T. G.
- Green
- Cohen
- Cohen J. D.
- Green L. R.