Journal articles on the topic 'Crown fire'
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1
Ex, Seth, Frederick W. Smith, and Tara L. Keyser. "Characterizing crown fuel distribution for conifers in the interior western United States." Canadian Journal of Forest Research 45, no. 7 (July 2015): 950–57. http://dx.doi.org/10.1139/cjfr-2014-0503.
Abstract:
Canopy fire hazard evaluation is essential for prioritizing fuel treatments and for assessing potential risk to firefighters during suppression activities. Fire hazard is usually expressed as predicted potential fire behavior, which is sensitive to the methodology used to quantitatively describe fuel profiles: methodologies that assume that fuel is distributed uniformly throughout crowns have been shown to predict less severe fire behavior than those that assume more realistic nonuniform fuel distributions. We used crown fuel data from seven interior western United States conifer species to characterize within-crown fuel distributions. Fuel was shifted upward and concentrated in crowns in crowded stands compared with crowns in open stands, which suggests that the vertical distribution of fuel is shaped by foliage concentration in favorable light environments near the top of crowns and echoes the predictable relationship between crown ratio and stand density. However, unlike crown ratio, the relationship between within-crown foliage distribution and stand density was independent of the shade tolerance of a species. This implies that there is a general relationship between stand density and within-crown fuel distribution for conifers and that species differences in fuel profiles related to shade tolerance are expressed primarily in the relationship between stand density and crown ratio.
2
Rodríguez y Silva, Francisco, Mercedes Guijarro, Javier Madrigal, Enrique Jiménez, Juan R. Molina, Carmen Hernando, Ricardo Vélez, and Jose A. Vega. "Assessment of crown fire initiation and spread models in Mediterranean conifer forests by using data from field and laboratory experiments." Forest Systems 26, no. 2 (July 24, 2017): e02S. http://dx.doi.org/10.5424/fs/2017262-10652.
Abstract:
Aims of study: To conduct the first full-scale crown fire experiment carried out in a Mediterranean conifer stand in Spain; to use different data sources to assess crown fire initiation and spread models, and to evaluate the role of convection in crown fire initiation.Area of study: The Sierra Morena mountains (Coordinates ETRS89 30N: X: 284793-285038; Y: 4218650-4218766), southern Spain, and the outdoor facilities of the Lourizán Forest Research Centre, northwestern Spain.Material and methods: The full-scale crown fire experiment was conducted in a young Pinus pinea stand. Field data were compared with data predicted using the most used crown fire spread models. A small-scale experiment was developed with Pinus pinaster trees to evaluate the role of convection in crown fire initiation. Mass loss calorimeter tests were conducted with P. pinea needles to estimate residence time of the flame, which was used to validate the crown fire spread model.Main results: The commonly used crown fire models underestimated the crown fire spread rate observed in the full-scale experiment, but the proposed new integrated approach yielded better fits. Without wind-forced convection, tree crowns did not ignite until flames from an intense surface fire contacted tree foliage. Bench-scale tests based on radiation heat flux therefore offer a limited insight to full-scale phenomena.Research highlights: Existing crown fire behaviour models may underestimate the rate of spread of crown fires in many Mediterranean ecosystems. New bench-scale methods based on flame buoyancy and more crown field experiments allowing detailed measurements of fire behaviour are needed.
3
Cohn, Gregory M., Russell A. Parsons, Emily K. Heyerdahl, Daniel G. Gavin, and Aquila Flower. "Simulated western spruce budworm defoliation reduces torching and crowning potential: a sensitivity analysis using a physics-based fire model." International Journal of Wildland Fire 23, no. 5 (2014): 709. http://dx.doi.org/10.1071/wf13074.
Abstract:
The widespread, native defoliator western spruce budworm (Choristoneura occidentalis Freeman) reduces canopy fuels, which might affect the potential for surface fires to torch (ignite the crowns of individual trees) or crown (spread between tree crowns). However, the effects of defoliation on fire behaviour are poorly understood. We used a physics-based fire model to examine the effects of defoliation and three aspects of how the phenomenon is represented in the model (the spatial distribution of defoliation within tree crowns, potential branchwood drying and model resolution). Our simulations suggest that fire intensity and crowning are reduced with increasing defoliation compared with un-defoliated trees, regardless of within-crown fuel density, but torching is only reduced with decreasing crown fuel density. A greater surface fire intensity was required to ignite the crown of a defoliated compared with an un-defoliated tree of the same crown base height. The effects of defoliation were somewhat mitigated by canopy fuel heterogeneity and potential branchwood drying, but these effects, as well as computational cell size, were less pronounced than the effect of defoliation itself on fire intensity. Our study suggests that areas heavily defoliated by western spruce budworm may inhibit the spread of crown fires and promote non-lethal surface fires.
4
Raymond, Crystal L., and David L. Peterson. "Fuel treatments alter the effects of wildfire in a mixed-evergreen forest, Oregon, USA." Canadian Journal of Forest Research 35, no. 12 (December 1, 2005): 2981–95. http://dx.doi.org/10.1139/x05-206.
Abstract:
We had the rare opportunity to quantify the relationship between fuels and fire severity using prefire surface and canopy fuel data and fire severity data after a wildfire. The study area is a mixed-evergreen forest of southwestern Oregon with a mixed-severity fire regime. Modeled fire behavior showed that thinning reduced canopy fuels, thereby decreasing the potential for crown fire spread. The potential for crown fire initiation remained fairly constant despite reductions in ladder fuels, because thinning increased surface fuels, which contributed to greater surface fire intensity. Thinning followed by underburning reduced canopy, ladder, and surface fuels, thereby decreasing surface fire intensity and crown fire potential. However, crown fire is not a prerequisite for high fire severity; damage to and mortality of overstory trees in the wildfire were extensive despite the absence of crown fire. Mortality was most severe in thinned treatments (80%100%), moderate in untreated stands (53%54%), and least severe in the thinned and underburned treatment (5%). Thinned treatments had higher fine-fuel loading and more extensive crown scorch, suggesting that greater consumption of fine fuels contributed to higher tree mortality. Fuel treatments intended to minimize tree mortality will be most effective if both ladder and surface fuels are treated.
5
Ritter, Scott M., Chad M. Hoffman, Mike A. Battaglia, Rodman Linn, and William E. Mell. "Vertical and Horizontal Crown Fuel Continuity Influences Group-Scale Ignition and Fuel Consumption." Fire 6, no. 8 (August 18, 2023): 321. http://dx.doi.org/10.3390/fire6080321.
Abstract:
A deeper understanding of the influence of fine-scale fuel patterns on fire behavior is essential to the design of forest treatments that aim to reduce fire hazard, enhance structural complexity, and increase ecosystem function and resilience. Of particular relevance is the impact of horizontal and vertical forest structure on potential tree torching and large-tree mortality. It may be the case that fire behavior in spatially complex stands differs from predictions based on stand-level descriptors of the fuel distribution and structure. In this work, we used a spatially explicit fire behavior model to evaluate how the vertical and horizontal distribution of fuels influences the potential for fire to travel from the surface into overstory tree crowns. Our results support the understanding that crown fuels (e.g., needles and small-diameter branchwood) close to the surface can aid in this transition; however, we add important nuance by showing the interactive effect of overstory horizontal fuel connectivity. The influence of fuels low in the canopy space was overridden by the effect of horizontal connectivity at surface fire-line intensities greater than 1415 kW/m. For example, tree groups with vertically continuous fuels and limited horizontal connectivity sustained less large-tree consumption than tree groups with a significant vertical gap between the surface and canopy but high-canopy horizontal connectivity. This effect was likely the result of reduced net vertical heat transfer as well as decreased horizontal heat transfer, or crown-to-crown spread, in the upper canopy. These results suggest that the crown fire hazard represented by vertically complex tree groups is strongly mediated by the density, or horizontal connectivity, of the tree crowns within the group, and therefore, managers may be able to mitigate some of the torching hazard associated with vertically heterogenous tree groups.
6
McCaskill, George. "The Hungry Bob Fire & Fire Surrogate Study: A 20-Year Evaluation of the Treatment Effects." Forests 10, no. 1 (December 28, 2018): 15. http://dx.doi.org/10.3390/f10010015.
Abstract:
The Hungry Bob fuels reduction project was part of a 12-site National Fire and Fire Surrogate (FFS) network of experiments conducted across the United States from the late 1990s through the early 2000s to determine the regional differences in applying alternative fuel-reduction treatments to forests. The Hungry Bob project focused on restoration treatments applied in low elevation, dry second-growth ponderosa pine (Pinus ponderosa subsp. ponderosa (Douglas ex C. Lawson) and Douglas-fir (Pseudotsuga menziesii subsp. glauca (Beissn.) Franco forests of northeastern Oregon. Treatments included a single entry thin from below in 1998, a late season burn in 2000, a thin (1999) followed by burning (2000), and a no-treatment control. This paper represents results 20 years after treatments and focuses on the treatment effects upon tree diameter growth, crown health, and ladder fuel conditions within the dry eastside stands. The Thin + Burn units produced the best diameter growth in ponderosa pine trees, whereas the Thin units had the best growth for Douglas-fir. The Burn treatment did not improve diameter growth over the Controls. The Thin + Burn treatments also produced trees with the highest tree crown ratios. The Burn unit trees had lower crown ratios compared to the Control trees. The crown reduction (reduction in tree crown ratio since 2004) was largest in the Burn-only units and smallest in the Thin + Burn units. Finally, the heights to the lower tree crowns were highest in the Thin + Burn trees and lowest in the Burn unit trees. Based upon the 20-year responses, the Thin + Burn treatments produced the best conditions for stand growth, while limiting fire stress upon residual tree crowns. It also proved most effective at reducing ladder fuels as represented by higher tree crown heights.
7
Cruz, Miguel G., Martin E. Alexander, and Ronald H. Wakimoto. "Development and testing of models for predicting crown fire rate of spread in conifer forest stands." Canadian Journal of Forest Research 35, no. 7 (July 1, 2005): 1626–39. http://dx.doi.org/10.1139/x05-085.
Abstract:
The rate of spread of crown fires advancing over level to gently undulating terrain was modeled through nonlinear regression analysis based on an experimental data set pertaining primarily to boreal forest fuel types. The data set covered a significant spectrum of fuel complex and fire behavior characteristics. Crown fire rate of spread was modeled separately for fires spreading in active and passive crown fire regimes. The active crown fire rate of spread model encompassing the effects of 10-m open wind speed, estimated fine fuel moisture content, and canopy bulk density explained 61% of the variability in the data set. Passive crown fire spread was modeled through a correction factor based on a criterion for active crowning related to canopy bulk density. The models were evaluated against independent data sets originating from experimental fires. The active crown fire rate of spread model predicted 42% of the independent experimental crown fire data with an error lower then 25% and a mean absolute percent error of 26%. While the models have some shortcomings and areas in need of improvement, they can be readily utilized in support of fire management decision making and other fire research studies.
8
Karna, Yogendra K., Trent D. Penman, Cristina Aponte, and Lauren T. Bennett. "Assessing Legacy Effects of Wildfires on the Crown Structure of Fire-Tolerant Eucalypt Trees Using Airborne LiDAR Data." Remote Sensing 11, no. 20 (October 20, 2019): 2433. http://dx.doi.org/10.3390/rs11202433.
Abstract:
The fire-tolerant eucalypt forests of south eastern Australia are assumed to fully recover from even the most intense fires; however, surprisingly, very few studies have quantitatively assessed that recovery. The accurate assessment of horizontal and vertical attributes of tree crowns after fire is essential to understand the fire’s legacy effects on tree growth and on forest structure. In this study, we quantitatively assessed individual tree crowns 8.5 years after a 2009 wildfire that burnt extensive areas of eucalypt forest in temperate Australia. We used airborne LiDAR data validated with field measurements to estimate multiple metrics that quantified the cover, density, and vertical distribution of individual-tree crowns in 51 plots of 0.05 ha in fire-tolerant eucalypt forest across four wildfire severity types (unburnt, low, moderate, high). Significant differences in the field-assessed mean height of fire scarring as a proportion of tree height and in the proportions of trees with epicormic (stem) resprouts were consistent with the gradation in fire severity. Linear mixed-effects models indicated persistent effects of both moderate and high-severity wildfire on tree crown architecture. Trees at high-severity sites had significantly less crown projection area and live crown width as a proportion of total crown width than those at unburnt and low-severity sites. Significant differences in LiDAR -based metrics (crown cover, evenness, leaf area density profiles) indicated that tree crowns at moderate and high-severity sites were comparatively narrow and more evenly distributed down the tree stem. These conical-shaped crowns contrasted sharply with the rounded crowns of trees at unburnt and low-severity sites and likely influenced both tree productivity and the accuracy of biomass allometric equations for nearly a decade after the fire. Our data provide a clear example of the utility of airborne LiDAR data for quantifying the impacts of disturbances at the scale of individual trees. Quantified effects of contrasting fire severities on the structure of resprouter tree crowns provide a strong basis for interpreting post-fire patterns in forest canopies and vegetation profiles in Light Detection and Ranging (LiDAR) and other remotely-sensed data at larger scales.
9
Cruz, Miguel G., Bret W. Butler, and Martin E. Alexander. "Predicting the ignition of crown fuels above a spreading surface fire. Part II: model evaluation." International Journal of Wildland Fire 15, no. 1 (2006): 61. http://dx.doi.org/10.1071/wf05045.
Abstract:
A crown fuel ignition model (CFIM) describing the temperature rise and subsequent ignition of the lower portion of tree crowns above a spreading surface fire was evaluated through a sensitivity analysis, comparison against other models, and testing against experimental fire data. Results indicate that the primary factors influencing crown fuel ignition are those determining the depth of the surface fire burning zone and the vertical distance between the ground/surface fuel strata and the lower boundary of the crown fuel layer. Intrinsic crown fuel properties such as fuel particle surface area-to-volume ratio and foliar moisture content were found to have a minor influence on the process of crown fuel ignition. Comparison of model predictions against data collected in high-intensity experimental fires and predictions from other models gave encouraging results relative to the validity of the model system.
10
Putnam, T., and B. W. Butler. "Evaluating fire shelter performance in experimental crown fires." Canadian Journal of Forest Research 34, no. 8 (August 1, 2004): 1600–1615. http://dx.doi.org/10.1139/x04-091.
Abstract:
Fire shelters are critical safety items required for use by most wildland firefighters in the United States. Most testing of fire shelters, clothing and other personal protective equipment (PPE) has been limited to prescribed fires or laboratory based studies. This study reports results from experiments where lined and unlined stainless steel or aluminum and glass fabric shelters were tested under high intensity crown fire conditions in and adjacent to experimental burn plots. Firefighter clothing and standard (pre-2003) fire shelters were also tested. Measured shelter surface and air temperatures and thermal impact on firefighter personal protective equipment were used to deduce the survivability of shelter designs and deployment location. Multiple glass and aluminum layered shelters show more promise than stainless steel shelters for improving overall fire shelter survivability. Data collected outside the burn plots generally indicate decreased heating as distance from forest edge increases, supporting the importance of maximizing distance from vegetation for survivability. It is recommended that common experiment protocols be adopted so that future research into fire shelter and PPE performance builds on work-to-date and provides a common basis from which analyses can be completed.
11
Baysal, İsmail. "Vertical Crown Fuel Distributions in Natural Calabrian Pine (Pinus brutia Ten.) Stands." Croatian journal of forest engineering 42, no. 2 (January 14, 2021): 301–12. http://dx.doi.org/10.5552/crojfe.2021.800.
Abstract:
Calabrian pine (Pinus brutia Ten.) is the most widely distributed coniferous species in Turkey. Forests mostly composed of Calabrian pine constitute the most flammable forests in fire sensitive regions of the country. Especially, regenerated and immature stands of this species have the most fire-prone fuel type. This study evaluates the results of vertical crown fuel distribution and develops some crown fuel models to explain canopy fuel characteristics in natural Calabrian pine stands. A total of 35 trees were cut down and crown fuels were determined vertically. The highest crown fuel load was generally situated in the middle part of tree crown. The percentage of needles in each crown section increased gradually from the beginning of lower parts to the upper parts of tree crowns for three stand types. Total crown fuel loads were determined as 5.66 kg for regenerated stands, 11.57 kg for immature stands and 17.44 kg for middle age stands, respectively. Correlation and regression analyses were performed to determine the relationship between needles, branches, available fuels, total crown fuels and tree properties. The results of crown fuel distribution and the allometric equations developed in this study can be used to predict vertical fuel load at any height from ground to the top of Calabrian pine stands. The results of this study will contribute to the verification and evaluation of fuel load prediction models in use, and enhance the understanding of crown fire behavior mechanism in forest fires.
12
Cruz, Miguel G., Martin E. Alexander, and Ronald H. Wakimoto. "Assessing the probability of crown fire initiation based on fire danger indices." Forestry Chronicle 79, no. 5 (October 1, 2003): 976–83. http://dx.doi.org/10.5558/tfc79976-5.
Abstract:
The initiation of crown fires in conifer stands was modelled through logistic regression analysis by considering as independent variables a basic physical descriptor of the fuel complex structure and selected components of the Canadian Forest Fire Weather Index (FWI) System. The study was based on a fire behaviour research database consisting of 63 experimental fires covering a relatively wide range of burning conditions and fuel type characteristics. Four models were built with decreasing input needs. Significant predictors of crown fire initiation were: canopy base height, wind speed measured at a height of 10 m in the open, and four components of the FWI System (i.e., Fine Fuel Moisture Code, Drought Code, Initial Spread Index and Buildup Index). The models predicted correctly the type of fire (i.e., surface or crown) between 90% and 66% of the time. The C index, a statistical measure, varied from 0.94 to 0.71, revealing good concordance between predicted probabilities and observed events. A comparison between the logistic models and Canadian Forest Fire Behaviour Prediction System models did not show any conclusive differences. The results of a limited evaluation involving two independent experimental fire data sets for distinctly different fuel complexes were encouraging. The logistic models built may have applicability in fire management decision support systems, allowing for the estimation of the probability of crown fire initiation at small and large spatial scales from commonly available fire environment and fire danger rating information. The relationships presented are considered valid for free-burning fires on level terrain in coniferous forests that have reached a pseudo steady-state and are not deemed applicable to dead conifer forests (i.e., insect-killed stands). Key words: Canadian Forest Fire Danger Rating System, crown fire initiation, fire behaviour, fire danger indices, logistic regression
13
Cruz, Miguel G., Martin E. Alexander, and Ronald H. Wakimoto. "Modeling the Likelihood of Crown Fire Occurrence in Conifer Forest Stands." Forest Science 50, no. 5 (October 1, 2004): 640–58. http://dx.doi.org/10.1093/forestscience/50.5.640.
Abstract:
Abstract The unknowns in wildland fire phenomenology lead to a simplified empirical model approach for predicting the onset of crown fires in live coniferous forests on level terrain. Model parameterization is based on a data set (n = 71) generated from conducting outdoor experimentalfires covering a significant portion of the spectrum of burning conditions associated with the initiation of crown fires. A logistic model is developed to predict the likelihood of crown fire occurrence based on three fire environment variables, namely the 10-m open wind speed, fuel stratagap (equivalent to live crown base height in some stands), estimated moisture content of fine dead fuels, and one fire-behavior descriptor–surface fuel consumption. The model correctly predicts 85% of the cases in the data set used in its development, and the receiver operatingcharacteristic statistic is 0.94. The model is evaluated for its sensitivity to its inputs, and its behavior is compared with other models used in decision support systems to operationally predict crown fire initiation. The results of a limited test of the model against two independent experimentalfire data sets for distinctly different fuel complexes is encouraging. FOR. SCI. 50(5):640–658.
14
Cobian-Iñiguez, Jeanette, Amir Hessam Aminfar, Shusmita Saha, Kyle Awayan, David R. Weise, and Marko Princevac. "The Transition and Spread of a Chaparral Crown Fire: Insights from Laboratory Scale Wind Tunnel Experiments." Journal of Combustion 2022 (July 20, 2022): 1–13. http://dx.doi.org/10.1155/2022/5630594.
Abstract:
Fire occurring in the chaparral behaves as a crown fire, a dual-layer fire that typically ignites in a dead surface fuel layer and transitions to an elevated live crown layer where it continues to spread. In chaparral fuels including chamise, a dominant species in southern California, flame transition to live crown fuels is associated with higher spread rates and greater fire intensity. Despite the relative importance of surface-to-crown transition and crown fire spread, most fire models represent chaparral fire as surface fire, therefore omitting key behavior processes driving this fire system. The purpose of this study was to characterize transition and spread behavior in chaparral fires modeled experimentally as crown fires. We examined heat release rate in the surface and crown fuel layers, time to transition, flame height, and rate of spread in wind-driven and nonwind-driven fires at two crown base heights. Our results showed that wind increased heat release rate, rate of spread, and flame height. A marked increase in heat release rate was observed in wind-driven fires, where adding wind produced an increase from 328 kW to 526 for a crown base height of 0.6 m and from 243 kW to 503 kW for a crown base height of 0.7 m. Further, crown base height served to decrease heat release rate and rate of spread for wind-driven and nonwind-driven fires.
15
Schaaf, Mark D., David V. Sandberg, Maarten D. Schreuder, and Cynthia L. Riccardi. "A conceptual framework for ranking crown fire potential in wildland fuelbedsThis article is one of a selection of papers published in the Special Forum on the Fuel Characteristic Classification System." Canadian Journal of Forest Research 37, no. 12 (December 2007): 2464–78. http://dx.doi.org/10.1139/x07-102.
Abstract:
This paper presents a conceptual framework for ranking the crown fire potential of wildland fuelbeds with forest canopies. This approach extends the work by Van Wagner and Rothermel, and introduces several new physical concepts to the modeling of crown fire behaviour derived from the reformulated Rothermel surface fire modeling concepts proposed by Sandberg et al. (this issue). This framework forms the basis for calculating the crown fire potentials of Fuel Characteristic Classification System (FCCS) fuelbeds (Ottmar et al., this issue). Two new crown fire potentials are proposed (i) the torching potential (TP) and (ii) the active crown potential (AP). A systematic comparison of TP and AP against field observations and Crown Fire Initiation and Spread (CFIS) model outputs produced encouraging results, suggesting that the FCCS framework might be a useful tool for fire managers to consider when ranking the potential for crown fires or evaluating the relative behaviour of crown fires in forest canopies.
16
Sandberg, David V., Cynthia L. Riccardi, and Mark D. Schaaf. "Fire potential rating for wildland fuelbeds using the Fuel Characteristic Classification SystemThis article is one of a selection of papers published in the Special Forum on the Fuel Characteristic Classification System." Canadian Journal of Forest Research 37, no. 12 (December 2007): 2456–63. http://dx.doi.org/10.1139/x07-093.
Abstract:
The Fuel Characteristic Classification System (FCCS) is a systematic catalog of inherent physical properties of wildland fuelbeds that allows land managers, policy makers, and scientists to build and calculate fuel characteristics with complete or incomplete information. The FCCS is equipped with a set of equations to calculate the potential of any real-world or simulated fuelbed to spread fire across the surface and in the crowns, and consume fuels. FCCS fire potentials are a set of relative values that rate the intrinsic physical capacity of a wildland fuelbed to release energy and to spread, crown, consume, and smolder under known or benchmark weather and fuel moisture conditions. The FCCS reports eight component fire potentials for every fuelbed, arranged in three categories: surface fire behaviour (reaction intensity, spread rate, and flame length), crown fire potential (torching and active crown fire), and available fuel potential (flaming, smouldering, and residual smouldering). FCCS fire potentials may be used to classify or compare fuelbeds that differ because of location, structure, passage of time, or management action, based on expected fire behavior or effect outcomes. As a classification tool, they are offered as an objective alternative to categorizing bulk properties of fuelbeds or stylized model inputs.
17
Whight, Sandra, and Ross Bradstock. "Indices of fire characteristics in sandstone heath near Sydney, Australia." International Journal of Wildland Fire 9, no. 2 (1999): 145. http://dx.doi.org/10.1071/wf00012.
Abstract:
The relative sensitivity and performance of post-hocindices of fire characteristics were examined in a heathland area burnt in1994. Sites burnt at differing times before 1994 were selected andqualitatively allocated to classes of high and low crown damage. Subsequentmeasures were made of height of consumption of crowns, length of the deadportion of Xanthorrhoea resinifera leaves, and minimumtip diameters of burnt branches of the shrubs,Banksia oblongifolia andBanksia ericifolia. Results indicated that significantdifferences in mean, minimum tip diameter corresponded to contrasting classesof crown damage (larger mean tip diameters in high crown damage sites). Meanminimum branch tip diameter in B. oblongifolia was notsignificantly correlated with fuel age but significant correlations were foundwith estimates of rate of spread and Byram fire intensity at the study sites.The minimum branch tip diameter method has potential for further developmentand use as an indicator of fire intensity in heathland vegetation.
18
de Groot, W. J., P. M. Bothwell, S. W. Taylor, B. M. Wotton, B. J. Stocks, and M. E. Alexander. "Jack pine regeneration and crown fires." Canadian Journal of Forest Research 34, no. 8 (August 1, 2004): 1634–41. http://dx.doi.org/10.1139/x04-073.
Abstract:
The effect of crown fires on Pinus banksiana Lamb. regeneration was studied in separate forest- and cone-burning experiments. Nine plots (0.562.25 ha) of jack pine trees near Fort Providence, Northwest Territories, were burned using crown fires to determine the effects of fire intensity, rate of fire spread, depth of burn, and postfire duff depth on seed viability and regeneration. Fire intensities were 36 902 93 476 kW/m, and fire spread rates were 2470 m/min. Depths of burn were low (2.03.6 cm), and postfire duff depths averaged 2.05.5 cm. Postfire seed rain was highly variable (64634 seeds/m2), but seed viability was near 67% on all plots. Jack pine regeneration was also highly variable (779 seedlings/m2). In the cone-burning experiment, the germination rate increased from 41% (unheated cones) to 64% after 10 s of burning but decreased sharply after 30 s. Flame temperature did not significantly affect viability. Cone-burning results suggest that the postfire seed rain originated from the upper canopy, where flame duration was 515 s, and seed in the lower canopy was consumed by fire. Seed rain and regeneration were primarily influenced by understory fine fuel consumption (and therefore, fire intensity), tree height, and live crown base height.
19
Tachajapong, Watcharapong, Jesse Lozano, Shankar Mahalingam, and David R. Weise. "Experimental modelling of crown fire initiation in open and closed shrubland systems." International Journal of Wildland Fire 23, no. 4 (2014): 451. http://dx.doi.org/10.1071/wf12118.
Abstract:
The transition of surface fire to live shrub crown fuels was studied through a simplified laboratory experiment using an open-topped wind tunnel. Respective surface and crown fuels used were excelsior (shredded Populus tremuloides wood) and live chamise (Adenostoma fasciculatum, including branches and foliage). A high crown fuel bulk density of 6.8kgm–3 with a low crown fuel base height of 0.20m was selected to ensure successful crown fire initiation. Diagnostics included flame height and surface fire evolution. Experimental results were compared with similar experiments performed in an open environment, in which the side walls of the wind tunnel were removed. The effect of varying wind speed in the range 0–1.8ms–1, representing a Froude number range of 0–1.1, on crown fire initiation was investigated. The suppression of lateral entrainment due to wind tunnel walls influenced surface fire behaviour. When wind speed increased from 1.5 to 1.8ms–1, the rate of spread of surface fire and surface fire depth increased from 5.5 to 12.0cms–1 and 0.61 to 1.02m. As a result, the residence time of convective heating significantly increased from 16.0 to 24.0s and the hot gas temperature at the crown base increased from 994 to 1141K. The change in surface fire characteristics significantly affected the convective energy transfer process. Thus, the net energy transfer to the crown fuel increased so the propensity for crown fire initiation increased. In contrast, increasing wind speed decreased the tendency for crown fuel initiation in an open environment because of the cooling effect from fresh air entrainment via the lateral sides of surface fire.
20
de Groot, William J., Chelene C. Hanes, and Yonghe Wang. "Crown fuel consumption in Canadian boreal forest fires." International Journal of Wildland Fire 31, no. 3 (February 28, 2022): 255–76. http://dx.doi.org/10.1071/wf21049.
Abstract:
Predictive crown fuel consumption models were developed using empirical data from experimental burning projects. Crown fuel load for foliage, bark, branchwood and stemwood were calculated for live overstorey and understorey trees in each plot using nationally derived tree biomass algorithms. Standing dead tree branchwood and stemwood biomass were similarly calculated. Crown bulk density values were calculated for all non-stemwood fuel components. Factors that affect the initiation and spread of crown fires (live crown base height, foliar moisture content, surface fuel consumption, critical surface fire spread rate, critical surface fire intensity) and components of the Canadian Forest Fire Weather Index System were not statistically significant variables. Crown bulk density was moderately correlated with crown fuel consumption but was not an influential factor. A new crown fuel consumption model was developed by regression analysis using fuel load of overstorey tree foliage and standing dead tree branchwood, and fire rate of spread through crown fraction burned. A simpler model was developed using only overstorey tree foliage fuel load and fire rate of spread. Both models provide forest and fire management agencies with enhanced ability to determine crown fuel consumption, fire behaviour and carbon emissions in boreal fires using basic forest inventory or biomass/carbon datasets.
21
Zhou, Kuibin, and Albert Simeoni. "An analytical model for predicting the flame length of fire lines and tree crown scorching." International Journal of Wildland Fire 31, no. 3 (January 24, 2022): 240–54. http://dx.doi.org/10.1071/wf21087.
Abstract:
In forest fires, the fire plume can heat tree crowns and cause the mortality of live vegetation, even though the surface fire spread is of low burning intensity. A lot of empirical or semi-empirical correlations have been built to link the fire intensity and flame height to the crown scorch height. These correlations lack the basic physical processes of heat transfer and thermal response of needles and leaves. Besides the flame height, the fire plume temperature and velocity are also of great importance to quantify the heat transfer to the tree crown. Accordingly, an analytical model, derived from a system of differential equations, describing the conservation of mass, momentum, energy, and chemical composition, is proposed to predict the properties of a fire plume from a line fire. The flame height predicted by the analytical model matches experimental measurements of small, medium, and large line fires, showing a considerable robustness of the proposed model. With an assumption of the lethal temperature of live vegetation, the analytical model can also predict the crown scorch height against available empirical correlations and experimental data. In addition, an analysis of the effect on the flame length of the distance between the fire and the ground surface indicates that it would be better to simulate the wildland fire front by a gaseous line fire above the ground surface. The effect of ambient air temperature and fireline residence time (or heating time of foliage) on the crown scorch height is also quantified. It is found that the hot plume can heat the live foliage to reach a lethal temperature of 60°C under a heating time of 60 s.
22
Cruz, Miguel G., and Martin E. Alexander. "Assessing crown fire potential in coniferous forests of western North America: a critique of current approaches and recent simulation studies." International Journal of Wildland Fire 19, no. 4 (2010): 377. http://dx.doi.org/10.1071/wf08132.
Abstract:
To control and use wildland fires safely and effectively depends on creditable assessments of fire potential, including the propensity for crowning in conifer forests. Simulation studies that use certain fire modelling systems (i.e. NEXUS, FlamMap, FARSITE, FFE-FVS (Fire and Fuels Extension to the Forest Vegetation Simulator), Fuel Management Analyst (FMAPlus®), BehavePlus) based on separate implementations or direct integration of Rothermel’s surface and crown rate of fire spread models with Van Wagner’s crown fire transition and propagation models are shown to have a significant underprediction bias when used in assessing potential crown fire behaviour in conifer forests of western North America. The principal sources of this underprediction bias are shown to include: (i) incompatible model linkages; (ii) use of surface and crown fire rate of spread models that have an inherent underprediction bias; and (iii) reduction in crown fire rate of spread based on the use of unsubstantiated crown fraction burned functions. The use of uncalibrated custom fuel models to represent surface fuelbeds is a fourth potential source of bias. These sources are described and documented in detail based on comparisons with experimental fire and wildfire observations and on separate analyses of model components. The manner in which the two primary canopy fuel inputs influencing crown fire initiation (i.e. foliar moisture content and canopy base height) is handled in these simulation studies and the meaning of Scott and Reinhardt’s two crown fire hazard indices are also critically examined.
23
Storey, Michael, Owen Price, and Elizabeth Tasker. "The role of weather, past fire and topography in crown fire occurrence in eastern Australia." International Journal of Wildland Fire 25, no. 10 (2016): 1048. http://dx.doi.org/10.1071/wf15171.
Abstract:
We analysed the influence of weather, time since fire (TSF) and topography on the occurrence of crown fire, as mapped from satellite imagery, in 23 of the largest wildfires in dry sclerophyll forests in eastern Australia from 2002 to 2013. Fires were analysed both individually and as groups. Fire weather was the most important predictor of crown consumption. TSF (a surrogate for fuel accumulation) had complex nonlinear effects that varied among fires. Crown fire likelihood was low up to 4 years post-fire, peaked at ~10 years post-fire and then declined. There was no clear indication that recent burning became more or less effective as fire weather became more severe. Steeper slope reduced crown fire likelihood, contrary to the assumptions of common fire behaviour equations. More exposed areas (ridges and plains) had higher crown fire likelihood. Our results suggest prescribed burning to maintain an average of 10 years’ TSF may actually increase crown fire likelihood, but burning much more frequently can be effective for risk reduction. Our results also suggest the effects of weather, TSF and slope are not adequately represented in the underlying equations of most fire behaviour models, potentially leading to poor prediction of fire spread and risk.
24
Kwon, Kyeongnam, Sungyon Kim, Sunjoo Lee, Chungeun Kwon, Kyunngwon Seo, and Seongkyun Im. "Analysis of Crown Fire Transition and Spread over Various Pine Trees Using Wildland–Urban Interface Fire Dynamic Simulator." Journal of the Korean Society of Hazard Mitigation 21, no. 4 (August 31, 2021): 31–38. http://dx.doi.org/10.9798/kosham.2021.21.4.31.
Abstract:
The crown fire of various pine trees was investigated using a wildland–urban interface fire dynamics simulator (WFDS). The effects of wind speeds and the spatial distances between fuels on crown fire ignition and spread were investigated. The average 30-year values of atmospheric conditions in March and April were used as the reference conditions to represent the climatic conditions for the wildfire season. As the wind speed increases, crown fire initiation is promoted, and the intensity and spread rate of the crown fire increase. The effects of the spatial distance on the crown fire depend on the wind speed and fuel conditions. The results show that a computational fluid dynamics tool using physics-based models, such as the WFDS, can predict the crown fire ignition and spread behaviors for domestic pine trees. However, further studies are required for other vegetation and domestic atmospheric conditions to validate the applicability of the WFDS on domestic fuels.
25
Nelson, Kellen N., Monica G. Turner, William H. Romme, and Daniel B. Tinker. "Simulated fire behaviour in young, postfire lodgepole pine forests." International Journal of Wildland Fire 26, no. 10 (2017): 852. http://dx.doi.org/10.1071/wf16226.
Abstract:
Early-seral forests are expanding throughout western North America as fire frequency and annual area burned increase, yet fire behaviour in young postfire forests is poorly understood. We simulated fire behaviour in 24-year-old lodgepole pine (Pinus contorta var. latifolia) stands in Yellowstone National Park, Wyoming, United States using operational models parameterised with empirical fuel characteristics, 50–99% fuel moisture conditions, and 1–60kmhr−1 open winds to address two questions: [1] How does fireline intensity, and crown fire initiation and spread vary among young, lodgepole pine stands? [2] What are the contributions of fuels, moisture and wind on fire behaviour? Sensitivity analysis indicated the greatest contributors to output variance were stand structure mediated wind attenuation, shrub fuel loads and 1000-h fuel moisture for fireline intensity; crown base height for crown fire initiation; and crown bulk density and 1-h fuel moisture for crown fire spread. Simulation results predicted crown fire (e.g. passive, conditional or active types) in over 90% of stands at 50th percentile moisture conditions and wind speeds greater than 3kmhr−1. We conclude that dense canopy characteristics heighten crown fire potential in young, postfire lodgepole pine forests even under less than extreme wind and fuel moisture conditions.
26
Splawinski, T. B., D. F. Greene, S. T. Michaletz, S. Gauthier, D. Houle, and Y. Bergeron. "Position of cones within cone clusters determines seed survival in black spruce during wildfire." Canadian Journal of Forest Research 49, no. 2 (February 2019): 121–27. http://dx.doi.org/10.1139/cjfr-2018-0209.
Abstract:
It has recently become clear that the regeneration density of serotinous species within a burned area declines with local fire intensity. It is assumed that this occurs because variation in local fire intensity leads to variation in incident heat fluxes and, ultimately, seed necrosis. We argue here that this same relationship between incident heat flux and seed necrosis is important at the scale of individual plant crowns. Using Picea mariana (Mill.) B.S.P. (black spruce), we show that postfire seed viability increases with crown height, depth into the crown, and angle from wind direction (with the windward side enjoying greater viability). All three effects are what one would expect given the physics of buoyant plumes, interactions of moving fire lines with wake flow around cylinders, and heat transfer in porous bodies such as a tree crown. We conclude by discussing the broader consequences of cone cluster size and global change on regeneration in serotinous species.
27
Page, Wesley, and Michael J. Jenkins. "Predicted Fire Behavior in Selected Mountain Pine Beetle–Infested Lodgepole Pine." Forest Science 53, no. 6 (December 1, 2007): 662–74. http://dx.doi.org/10.1093/forestscience/53.6.662.
Abstract:
Abstract Using custom fuel models developed for use with Rothermel's surface fire spread model, we predicted and compared fire behavior in lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stands with endemic, current epidemic, and postepidemic mountain pine beetle (Dendroctonus ponderosae Hopkins) populations using standardized sets of wind speeds and fuel moistures. We also compared our fire behavior results with those from standard fuel models. Results indicated that for surface fires both rates of fire spread and fireline intensities were higher in the current epidemic stands than in the endemic stands owing to increases in the amounts of fine surface fuels. In the postepidemic stands, rates of surface fire spread and fireline intensities were higher than in the endemic stands owing to decreased vegetative sheltering and its effect on mid-flame wind speed. Total heat release of surface fires, including postfrontal combustion, was also higher in the postepidemic stands owing to heavy accumulations of large diameter fuels. Crown fires were more likely to initiate in the postepidemic stands owing to greater fireline intensities and lower crown base heights. However, the critical rate of spread needed to sustain an active crown fire was higher in the postepidemic stands owing to decreased aerial fuel continuity. We suggest here that crown fire initiation in the current epidemic stands was also greater because of an abundance of dead aerial fuels; although this relationship is unclear.
28
Mc Alpine, RS, and MW Hobbs. "Predicting the Height to Live Crown Base in Plantations of Four Boreal Forest Species." International Journal of Wildland Fire 4, no. 2 (1994): 103. http://dx.doi.org/10.1071/wf9940103.
Abstract:
A critical parameter for the initiation and propagation of a crown fire in the boreal forest is the height to the base of the live crown. The initiation of a crown fire requires that the surface fire intensity must be sufficient to ''jump'' the gap between the forest floor and the live crown and ignite crown fuels. The greater the height of the live crown base, the more intense the surface fire must be to induce a crown fire. Plantation forest fuels tend to be more structured and have less variability than naturally regenerated areas, allowing prediction of the height of the live crown base to be made from commonly available stand parameters. Plantations of four commonly planted boreal forest species were sampled over a variety of age classes to determine a predictive relationship for height to live crown base. Height to live crown base can be predicted from stand height and density for Pinus banksiana (jack pine), Pinus resinosa (red pine), Picea mariana (black spruce), and Picea glauca (white spruce). In addition to predicting the height to live crown base, parameters within the equations lead to other observations. Crown foliar fuel loading does not change with stand height following crown closure in red pine but in the other three species crown fuel load increases as the stand grows taller.
29
Kim, Taehyun, Yugyeong Kim, Jeman Lee, Choongshik Woo, and Sangjun Im. "Post-Fire Changes in Canopy Solute Leaching in Pinus densiflora Forests." Forests 14, no. 10 (October 4, 2023): 1996. http://dx.doi.org/10.3390/f14101996.
Abstract:
Fires can burn canopy fuel and replace leafy crowns with charred branches and trunks, thereby affecting hydrological flow and water chemistry. However, little is known about the effects of fire on throughfall volumes and chemical fluxes in temperate forests. Therefore, we aimed to monitor the volume and chemistry of throughfall in pine trees (Pinus densiflora) damaged by the 2022 Gangneung-Donghae Forest fire in the Republic of Korea. Immediately after the forest fire, funnel-type measurements were performed to collect the throughfall beneath five trees at foliage necrosis and crown consumption sites. The amount of water that penetrated in a specified period was continually measured and analyzed in terms of the water quality components. Crown consumption resulted in the passage of more water due to the removal of the tree canopy; however, the ratio of throughfall to total rainfall remained constant as the rainfall amount increased. The throughfall volume was not significantly different owing to the fire damage. The solute concentrations of Ca and TOC at the crown consumption site were higher than those at the foliage necrosis site after the fire; however, no significant difference was observed three months after the fire. In this study, the changes in the amount and water quality of throughfall due to fire were examined over a relatively short period, providing fundamental data for nutrient cycling management of wildfire-damaged soil.
30
Johnston, D. C., M. R. Turetsky, B. W. Benscoter, and B. M. Wotton. "Fuel load, structure, and potential fire behaviour in black spruce bogs." Canadian Journal of Forest Research 45, no. 7 (July 2015): 888–99. http://dx.doi.org/10.1139/cjfr-2014-0334.
Abstract:
Boreal peatlands in Canada comprise a substantial store of soil organic carbon (peat), and this peat is vulnerable to extensive burning during periods of extended drying. Increased frequency of extreme weather events in boreal regions is expected with future climate change, and the conditions that would support sustained smouldering peat combustion within peatlands may be more common. Organic soils tend to burn by smouldering combustion, a very slow-moving process in fuels such as those found in peatlands. Thus the most extreme conditions for carbon loss to the atmosphere due to the burning of peat likely occur when widespread propagation of flaming combustion leads to widespread initiation of smouldering. To investigate the potential for large-scale, high-intensity fire spread across forested bogs, we examined the fuel conditions in forested bogs necessary to support active crown fire. We measured surface and canopy fine fuels (those available to contribute to the propagating energy flux of the main flaming front) across a postfire chronosequence of forested boreal bog from central Alberta, Canada. We found that fuel load of fine surface material remained relatively constant across the chronosequence and at levels large enough to support crown fire initiation. Black spruce (Picea mariana (Mill.) B.S.P.) regeneration begins to fill in the crown space with increasing time since disturbance and achieves crown bulk densities similar to black spruce upland forests. We estimated that after about 80 years, the black spruce canopy has developed enough available fuel to support active crown fire on between 10% to 40% of days in a typical fire season in central Alberta, Canada. Broad-scale propagation of high-intensity fire across a peatland when coincident with drought-induced lower moisture in deep peatland layers has the potential to lead to a substantial release of stored terrestrial carbon.
31
Cohen, Jack D. "Relating flame radiation to home ignition using modeling and experimental crown fires." Canadian Journal of Forest Research 34, no. 8 (August 1, 2004): 1616–26. http://dx.doi.org/10.1139/x04-049.
Abstract:
Wildlandurban fire destruction depends on homes igniting and thus requires an examination of the ignition requirements. A physicaltheoretical model, based on severe case conditions and ideal heat transfer characteristics, estimated wood wall ignition occurrence from flame radiation heating and piloted ignition requirements. Crown fire experiments provided an opportunity for assessing model reliability. The crown fire experiments were specifically instrumented with wood wall sections and heat flux sensors to investigate direct flame heating leading to home ignition during wildland fires. The experimental results indicated that the flame radiation model overestimated the structure-to-flame distance that would result in wood wall ignition. Wall sections that ignited during the experimental crown fires did not sustain flaming after crown fire burnout. The experiments also revealed that the forest canopy attenuated the flame radiation as the crown fire spread within the forest plot. Ignition modeling and the associated crown fire experiments described the flame-to-structure distance scale associated with flame heating related to wall ignition.
32
Taylor, Jennifer E., Vaughan Monamy, and Barry J. Fox. "Flowering of Xanthorrhoea fulva: the Effect of Fire and Clipping." Australian Journal of Botany 46, no. 2 (1998): 241. http://dx.doi.org/10.1071/bt96100.
Abstract:
Xanthorrhoea fulva (A.Lee) Bedford is a dominant plant of wet heath at Myall Lakes National Park, New South Wales, Australia. As for many other members of the genus, fire is the main stimulus for flowering of X. fulva. The stimulus to flowering provided by fire and by crown removal (clipping) of X. fulva was compared in two different seasons and for two different between-fire intervals. The percentage of X. fulva crowns flowering was greater following: (i) summer disturbance when compared with winter disturbance; (ii) short between-fire intervals (3.75 or 5.25 years) when compared with long between-fire intervals (9.3 or 16.9 years); and (iii) burning when compared with clipping. This demonstrates that the stimulus to floral induction in X. fulva is a combination of a seasonal component and crown removal, a component related to the interval since the last fire, and perhaps some other factor(s) not tested for in this study. This variation in flowering response of X. fulva shows the importance of considering immediate and historic characteristics of fire and other disturbances when management decisions are being made.
33
Roos, Christopher I., and Andrew C. Scott. "A comparison of charcoal reflectance between crown and surface fire contexts in dry south-west USA forests." International Journal of Wildland Fire 27, no. 6 (2018): 396. http://dx.doi.org/10.1071/wf17139.
Abstract:
The historical and modern importance of crown fires in ponderosa pine and dry mixed-conifer forests of the south-west USA has been much debated. The microscopic reflectance of charcoal in polished blocks under oil shows promise as a semiquantitative proxy for fire severity using charcoal from post-fire landscapes. We measured the reflectance of 33 modern charcoal samples to evaluate (1) whether charcoal reflectance can distinguish between crown fires and surface fires in these forests; and (2) whether surface fires with masticated fuels burn with severities similar to surface fires in grass, litter and duff fuels. The charcoal analysed was primarily collected after wildland fires under two different conditions: (l) wildfires with moderate to high severity and crown fire behaviour (n = 17), and (2) prescribed fires with low to moderate severity but no crown fire behaviour (n = 16). Statistical analysis indicates that charcoal reflectance produced in crown fires significantly differs from surface fire charcoal, particularly surface fire charcoal formed in grass, duff and litter fuels. However, charcoal produced from surface fires in masticated fuels is indistinguishable from crown fire charcoal, suggesting that fires in areas that have experienced in situ mastication may have soil impacts similar to crown fires.
34
Alexander, Martin E., and Miguel G. Cruz. "Evaluating the 3-m tree crown spacing guideline for the prevention of crowning wildfires in lodgepole pine forests, Alberta." Forestry Chronicle 96, no. 02 (July 2020): 165–73. http://dx.doi.org/10.5558/tfc2020-021.
Abstract:
A 3-m between crown spacing is a commonly cited criterion found in the wildland-urban interface fire literature for minimizing the likelihood of a fully-developed crown fire from occurring in a conifer forest on level terrain. The validity of this general recommendation is examined here in light of our current state-of-knowledge regarding crown fire propagation in relation to canopy bulk density. Given the characteristics of the overstory structure for 20 lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) stands located in Alberta, as sourced from the literature, the canopy fuel properties following a virtual thinning to a 3-m crown spacing and then to a targeted canopy bulk density of 0.05 kg/m3 were computed. On the basis of these computations, crown fire potential was then analyzed and interpreted. The conclusion reached is that, in the majority of cases, a less widely spaced stand would be adequate for preventing crown fire development in lodgepole pine forests.
35
Alexander, Martin E., and Miguel G. Cruz. "Interdependencies between flame length and fireline intensity in predicting crown fire initiation and crown scorch height." International Journal of Wildland Fire 21, no. 2 (2012): 95. http://dx.doi.org/10.1071/wf11001.
Abstract:
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.
36
Alexander, Martin E., and Miguel G. Cruz. "Corrigendum to: Interdependencies between flame length and fireline intensity in predicting crown fire initiation and crown scorch height." International Journal of Wildland Fire 30, no. 1 (2021): 70. http://dx.doi.org/10.1071/wf11001_c1.
Abstract:
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.
37
Alexander, Martin E., and Miguel G. Cruz. "Corrigendum to: Interdependencies between flame length and fireline intensity in predicting crown fire initiation and crown scorch height." International Journal of Wildland Fire 26, no. 4 (2017): 345. http://dx.doi.org/10.1071/wf11001_co.
Abstract:
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.
38
Cruz, Miguel G., Bret W. Butler, Martin E. Alexander, Jason M. Forthofer, and Ronald H. Wakimoto. "Predicting the ignition of crown fuels above a spreading surface fire. Part I: model idealization." International Journal of Wildland Fire 15, no. 1 (2006): 47. http://dx.doi.org/10.1071/wf04061.
Abstract:
A model was developed to predict the ignition of forest crown fuels above a surface fire based on heat transfer theory. The crown fuel ignition model (hereafter referred to as CFIM) is based on first principles, integrating: (i) the characteristics of the energy source as defined by surface fire flame front properties; (ii) buoyant plume dynamics; (iii) heat sink as described by the crown fuel particle characteristics; and (iv) energy transfer (gain and losses) to the crown fuels. Fuel particle temperature increase is determined through an energy balance relating heat absorption to fuel particle temperature. The final model output is the temperature of the crown fuel particles, which upon reaching ignition temperature are assumed to ignite. CFIM predicts the ignition of crown fuels but does not determine the onset of crown fire spread per se. The coupling of the CFIM with models determining the rate of propagation of crown fires allows for the prediction of the potential for sustained crowning. CFIM has the potential to be implemented in fire management decision support systems.
39
Cruz, Miguel G., and Martin E. Alexander. "Modelling the rate of fire spread and uncertainty associated with the onset and propagation of crown fires in conifer forest stands." International Journal of Wildland Fire 26, no. 5 (2017): 413. http://dx.doi.org/10.1071/wf16218.
Abstract:
Crown fires are complex, unstable phenomena dependent on feedback mechanisms between the combustion products of distinct fuel layers. We describe non-linear fire behaviour associated with crowning and the uncertainty they cause in fire behaviour predictions by running a semiphysical modelling system within a simple Monte Carlo simulation framework. The method was able to capture the dynamics of passive and active crown fire spread regimes, providing estimates of average rate of spread and the extent of crown fire activity. System outputs were evaluated against data collected from a wildfire that occurred in a radiata pine plantation in south-eastern Australia. The Monte Carlo method reduced prediction errors relative to the more commonly used deterministic modelling approach, and allowed a more complete description of the level of crown fire behaviour to expect. The method also provides uncertainty measures and probabilistic outputs, extending the range of questions that can be answered by fire behaviour models.
40
Engle, David M., Jimmy F. Stritzke, and P. Larry Claypool. "Effect of Paraquat Plus Prescribed Burning on Eastern Redcedar (Juniperus virginiana)." Weed Technology 2, no. 2 (April 1988): 172–74. http://dx.doi.org/10.1017/s0890037x00030347.
Abstract:
Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) was evaluated as a pretreatment for eastern redcedar (Juniperus virginiana L. # IUPVI) before spring burning in tallgrass prairie. Wetting sprays of paraquat at 0.3 g ai/L or 0.6 g/L were applied to crowns of small (0.8 to 1.5 m), medium (1.5 to 2.5 m), and large (2.5 to 5.0 m) eastern redcedar trees in August 1983 and 1984 before prescribed burns in the springs of 1984 and 1985. Paraquat alone at the 0.6 g/L concentration killed about 90% of the crown of small trees but as little as 30% of the crown of large trees. Paraquat pretreatments increased post-fire damage to small- and medium-size trees and partially compensated for light fine fuel loading.
41
Barker, Jason S., Andrew N. Gray, and Jeremy S. Fried. "The Effects of Crown Scorch on Post-fire Delayed Mortality Are Modified by Drought Exposure in California (USA)." Fire 5, no. 1 (February 2, 2022): 21. http://dx.doi.org/10.3390/fire5010021.
Abstract:
Accurately predicting the mortality of trees that initially survive a fire event is important for management, such as planning post-fire salvage, planting, and prescribed fires. Although crown scorch has been successfully used to predict post-fire mortality (greater than one-year post-fire), it remains unclear whether other first-order fire effect metrics (e.g., stem char) and information on growing conditions can improve such predictions. Droughts can also elevate mortality and may interact, synergistically, with fire effects to influence post-fire tree survival. We used logistic regression to test whether drought exposure, as indicated by summarized monthly Palmer Drought Severity Index (PDSI) over ten-years could improve predictions of delayed mortality (4–9 years post-fire) at the individual tree level in fire-affected forest inventory and analysis (FIA) plots in California (USA). We included crown scorch, bark thickness, stem char, soil char, slope, and aspect in the model as predictors. We selected the six most prevalent species to include in the model: canyon live oak, Douglas-fir, Jeffrey pine, incense-cedar, ponderosa pine, and white fir. Mean delayed mortality, based on tree count, across all FIA plots across all tree species and plots was 17%, and overall accuracy was good (AUC = 79%). Our model performed well, correctly predicting survivor trees (sensitivity of 0.98) but had difficulty correctly predicting the smaller number of mortality trees (specificity of 0.27) at the standard probability=0.5 mortality threshold. Crown scorch was the most influential predictor of tree mortality. Increasing crown scorch was associated with greater risk of delayed mortality for all six species, with trees exhibiting over 75% crown scorch having a probability of dying that exceeded 0.5. Increasing levels of stem char and soil char (first order indicators) were associated with increasing mortality risk but to less effect than crown scorch. We expected that greater drought exposure would increase delayed post-fire mortality, but we found that increasing drought exposure (median and minimum PDSI) was associated with a modest decrease in post-fire mortality. However, we did find that trees with high levels of crown scorch were less likely to survive with increasing drought exposure (median PDSI). Delayed mortality risk decreased as terrain slope increased. Taken together, our results suggest that trees with substantial crown damage may be more vulnerable to delayed mortality if exposed to drought and that crown scorch is an effective post-fire mortality predictor up to 10 years post-fire.
42
Fulé, P. Z., A. E. M. Waltz, W. W. Covington, and T. A. Heinlein. "Measuring Forest Restoration Effectiveness in Reducing Hazardous Fuels." Journal of Forestry 99, no. 11 (November 1, 2001): 24–29. http://dx.doi.org/10.1093/jof/99.11.24.
Abstract:
Abstract Forest restoration treatments of thinning young trees followed by prescribed burning in north-western Arizona led to significantly lower stand density, lower crown fuel load, and higher crown base height than untreated stands. Simulated fire under extreme weather conditions caused 48 percent more canopy burning and higher flame lengths, heat/area, and rate of spread in untreated stands. Wind speeds required for passive crown fire (torching) were twice as high in treated stands. Treated stands were highly heterogeneous, but restoration treatments clearly enhanced crown-fire resistance.
43
Grishin, A. M., and V. A. Perminov. "Transition of the forest ground fire to crown fire." Combustion, Explosion, and Shock Waves 26, no. 6 (November 1990): 644–51. http://dx.doi.org/10.1007/bf00786501.
44
Mansfield, Shawn D., Roberta Parish, James W. Goudie, Kyu-Young Kang, and Peter Ott. "The effects of crown ratio on the transition from juvenile to mature wood production in lodgepole pine in western Canada." Canadian Journal of Forest Research 37, no. 8 (August 2007): 1450–59. http://dx.doi.org/10.1139/x06-299.
Abstract:
Crown depth, tree spacing, and stand density have major effects on wood quality and fibre characteristics of trees. Lodgepole pine ( Pinus contorta Doug. ex Loud.) trees from a mixture of plantation and fire origin stands were employed to determine how crown ratio, a surrogate for stand density, affected mature wood production. In total, 104 trees were sampled, ranging from 24 to 110 years of age, from stands in western Alberta and interior British Columbia, Canada. Samples taken along the bole were measured for wood density, which was subject to segmented regression analysis to identify the transition point from juvenile to mature wood production. On average, the lodgepole pine trees were 31 (±17 SD) years old before mature wood production began. A mixed-effects model, in which combination of fixed effects (tree age, height of the sample disc relative to crown base, and crown length) and random effects (site, trees nested in sites, and discs nested in both trees and sites) proved to be the best predictor of years of mature wood production along the bole. The transition from juvenile to mature wood was shown to be below the crown base in trees <50 years old with deep crowns, and above the crown base otherwise.
45
Temiño-Villota, Salomé, Dante A. Rodríguez-Trejo, Domingo M. Molina Terrén, and Kevin Ryan. "Modelling initial mortality of Abies religiosa in a crown fire in Mexico." Forest Systems 25, no. 1 (April 1, 2016): 047. http://dx.doi.org/10.5424/fs/2016251-06887.
Abstract:
Aim of study: The objectives of this work were to determine which morphological and fire severity variables may help explain the mortality of adult Abies religiosa (Kunth) Schltdl. & Cham., to model the probability of this species after being affected by crown fire, and to obtain more elements to classify the sacred fir in terms of fire resistance. This type of studies are relevant to estimate the impact of crown fires on the climax forests that forms this species.Area of study: The burned forest was located in the southern Mexico City, borough.Material and methods: Morphological variables and fire severity indicators were collected for 335 Abies religiosa trees burned by a mixed severity fire. Logistic regression was used to analyze data and develop models that best explained tree mortality.Main results: Survival was 26.9%. The models for height (p≤0.0001), diameter at breast height (p=0.0082), crown length (p≤0.0001) and crown base height (p≤0.0001) were significant, with a negative relationship between each one of these variables and probability of mortality. The significant severity variables were lethal scorch height (p≤0.0001) and crown kill (p≤ 0.0001), which have a direct relationship with probability of mortality.Highlights: This species is moderately fire-resistant. Crown kill ≥ 70% markedly increases mortality. Silvicultural activities such as pruning, thinning and fuel management can reduce the risk of crown fires.
46
Stocks, B. J., M. E. Alexander, B. M. Wotton, C. N. Stefner, M. D. Flannigan, S. W. Taylor, N. Lavoie, et al. "Crown fire behaviour in a northern jack pine black spruce forest." Canadian Journal of Forest Research 34, no. 8 (August 1, 2004): 1548–60. http://dx.doi.org/10.1139/x04-054.
Abstract:
This paper reports on the behaviour of 10 experimental crown fires conducted between 1997 and 2000 during the International Crown Fire Modelling Experiment (ICFME) in Canada's Northwest Territories. The primary goal of ICFME was a replicated series of high-intensity crown fires designed to validate and improve existing theoretical and empirical models of crown fire behaviour. Fire behaviour characteristics were typical for fully developed boreal forest crown fires, with fires advancing at 1570 m/min, consuming significant quantities of fuel (2.85.5 kg/m2) and releasing vast amounts of thermal heat energy. The resulting flame fronts commonly extended 2540 m above the ground with head fire intensities up to 90 000 kW/m. Depth of burn ranged from 1.43.6 cm, representing a 25%65% reduction in the thickness of the forest floor layer. Most of the smaller diameter (<3.0 cm) woody surface fuels were consumed, along with a significant proportion of the larger downed woody material. A high degree of fuel consumption occurred in the understory and overstory canopy with very little material less than 1.0 cm in diameter remaining. The documentation of fire behaviour, fire danger, and fire weather conditions carried out during ICFME permitted the evaluation of several empirically based North American fire behaviour prediction systems and models.
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Battaglia, Mike, Frederick W. Smith, and Wayne D. Shepperd. "Predicting mortality of ponderosa pine regeneration after prescribed fire in the Black Hills, South Dakota, USA." International Journal of Wildland Fire 18, no. 2 (2009): 176. http://dx.doi.org/10.1071/wf07163.
Abstract:
Reduction of crown fire hazard in Pinus ponderosa forests in the Black Hills, SD, often focuses on the removal of overstorey trees to reduce crown bulk density. Dense ponderosa pine regeneration establishes several years after treatment and eventually increases crown fire risk if allowed to grow. Using prescribed fire to control this regeneration is hampered by the limited knowledge of fire-related mortality threshold values for seedlings (<1.4 m tall) and saplings (0.25 to 10 cm diameter at breast height). The present study was initiated to assess fire-related mortality of ponderosa pine seedlings and saplings on prescribed burns across the Black Hills. We established plots in several burn units after the first post-fire growing season to measure crown volume scorch, crown volume consumption, basal scorch, and ground char for ponderosa pine seedlings and saplings. Logistic regression was used to model the probability of mortality based on tree size, flame length, and direct fire effects. Tree size, flame length, crown damage, ground char, and basal char severity were all important factors in the prediction of mortality. Observed mortality was >70% for seedlings but was only 18 to 46% for sapling-sized trees. The differences in mortality thresholds for ponderosa pine seedlings and saplings highlight their susceptibility to different damage pathways and give managers several options when designing burn prescriptions.
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Viedma, Olga, Danilo R. A. Almeida, and Jose Manuel Moreno. "Postfire Tree Structure from High-Resolution LiDAR and RBR Sentinel 2A Fire Severity Metrics in a Pinus halepensis-Dominated Burned Stand." Remote Sensing 12, no. 21 (October 30, 2020): 3554. http://dx.doi.org/10.3390/rs12213554.
Abstract:
Tree and plant structures remaining after fires reflect well their degree of consumption, and are therefore good indicators of fire severity. Satellite optical images are commonly used to estimate fire severity. However, depending on the severity of a fire, these sensors have a limited ability to penetrate the canopy down to the ground. Airborne light detection and ranging (LiDAR) can overcome this limitation. Assessing the differences between areas that have been burned in different fire severities based on satellite images of plant and tree structures remaining after fires is important, given its widespread use to characterize fires and fire impacts (e.g., carbon emissions). Here, we measured the remaining tree structures after a fire in a forest stand burned in SE Spain in the summer of 2017. We used high-resolution LiDAR data, acquired from an unmanned aerial vehicle (UAV) six months after the fire. This information was crossed with fire severity levels based on the relativized burnt ratio (RBR) derived from Sentinel 2A images acquired a few months before and after fire. LiDAR tree structure data derived from vertical canopy profiles (VCPs) were classified into three clusters, using hierarchical principal component analysis (HPCA), followed by a random forest (RF) to select the most important variables in distinguishing the cluster groups. Among these, crown leaf area index (LAI), crown leaf area density (LAD), crown volume, tree height and tree height skewness, among others, were the most significant variables, and reflected well the degree of combustion undergone by the trees based on the response of these variables to variations in fire severity from RBR Sentinel 2A. LiDAR metrics were able to distinguish crown fire from surface fire through changes in the understory LAI and understory and midstory vegetation. The three tree structure clusters were well separated among each other and significantly related with the RBR Sentinel 2A-derived fire severity categories. Unburned and low-severity burned areas were more diverse in tree structures than moderate and high severity burned ones. The LiDAR metrics derived from VCPs demonstrated promising potential for characterizing fine-grained post-fire plant structures and fire damage when crossed with satellite-based fire severity metrics, turning into a promising approach for better characterizing fire impacts at a resolution needed for many ecological processes.
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Keyes, Christopher R., and Kevin L. O'Hara. "Quantifying Stand Targets for Silvicultural Prevention of Crown Fires." Western Journal of Applied Forestry 17, no. 2 (April 1, 2002): 101–9. http://dx.doi.org/10.1093/wjaf/17.2.101.
Abstract:
Abstract Forest managers are expressing a growing interest in proactively reducing susceptibility to crown fires, but the quantitative basis for defining specific stand targets and prescribing silvicultural regimes for this objective is lacking. A procedure is presented for creating resistant stand structures that exploits the relationship between crown fire development and characteristics of stand structure. The BEHAVE surface fire model was integrated with modified versions of the Van Wagner crown ignition and crown fire spread equations in order to quantify structural targets for mitigative silvicultural practices. The procedure tolerates an array of input data types for weather, site, and surface fuel variables so that hazard-reducing guidelines are tailored to specific site and stand conditions. Suggested strategies for achieving crown fire-resistant stand targets include pruning, low thinning, and surface fuel management. West. J. Appl. For. 17(2):101–109.
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Arseneault, Dominique. "Impact of fire behavior on postfire forest development in a homogeneous boreal landscape." Canadian Journal of Forest Research 31, no. 8 (August 1, 2001): 1367–74. http://dx.doi.org/10.1139/x01-065.
Abstract:
Although behavior of stand-replacing wildfire has significant impacts on initial tree regeneration in the fire-prone boreal landscape, the unknown behavior of most past wildfires has precluded any evaluation of these impacts on the progressive development of late-successional forest ecosystems. In this study, the effects of fire behavior on long-term ecosystem development were evaluated by linking the banding pattern of tree density in a jack pine (Pinus banksiana Lamb.) - black spruce (Picea mariana (Mill.) BSP) forest on a flat and homogeneous landform in northern Quebec to a similar, previously documented pattern of unburned strips of tree crowns. Complex wildfire-atmosphere interactions during the spread of a 1941 stand-replacing wildfire created this pattern in stem density, most likely by differentially damaging the canopy-stored seed bank between areas of contrasting fire severity. Sites with initial differences in seedling densities have followed different recovery pathways and developed markedly different forest structures, as well as differences in species abundance. Compared with areas of severe crown fire, the present-day vegetation in areas of low crown fire severity shows a higher density of living pines in the canopy layer, higher spruce and dead pine densities in the subcanopy layer, a lower pine density in the understory layer, and a higher abundance of Cladina rangiferina (L.) and Cladina stellaris Opiz (Brodo) in the lichen mat. This close spatial connection between crown fire severity and the ecological processes driving ecosystem recovery may explain large differences in vegetation among sites in the boreal landscape.