Fire intensity, fire severity and burn severity: a brief review and suggested usage

2009 ◽  
Vol 18 (1) ◽  
pp. 116 ◽  
Author(s):  
Jon E. Keeley
Keyword(s):  
Fire Severity ◽  
Empirical Studies ◽  
Fire Behavior ◽  
Radiant Energy ◽  
Energy Output ◽  
Burn Severity ◽  
Fire Intensity ◽  
Ecosystem Responses ◽  
Single Measure ◽  
Ecosystem Impacts

Several recent papers have suggested replacing the terminology of fire intensity and fire severity. Part of the problem with fire intensity is that it is sometimes used incorrectly to describe fire effects, when in fact it is justifiably restricted to measures of energy output. Increasingly, the term has created confusion because some authors have restricted its usage to a single measure of energy output referred to as fireline intensity. This metric is most useful in understanding fire behavior in forests, but is too narrow to fully capture the multitude of ways fire energy affects ecosystems. Fire intensity represents the energy released during various phases of a fire, and different metrics such as reaction intensity, fireline intensity, temperature, heating duration and radiant energy are useful for different purposes. Fire severity, and the related term burn severity, have created considerable confusion because of recent changes in their usage. Some authors have justified this by contending that fire severity is defined broadly as ecosystem impacts from fire and thus is open to individual interpretation. However, empirical studies have defined fire severity operationally as the loss of or change in organic matter aboveground and belowground, although the precise metric varies with management needs. Confusion arises because fire or burn severity is sometimes defined so that it also includes ecosystem responses. Ecosystem responses include soil erosion, vegetation regeneration, restoration of community structure, faunal recolonization, and a plethora of related response variables. Although some ecosystem responses are correlated with measures of fire or burn severity, many important ecosystem processes have either not been demonstrated to be predicted by severity indices or have been shown in some vegetation types to be unrelated to severity. This is a critical issue because fire or burn severity are readily measurable parameters, both on the ground and with remote sensing, yet ecosystem responses are of most interest to resource managers.

Calculating and interpreting forest fire intensities

1982 ◽  
Vol 60 (4) ◽  
pp. 349-357 ◽  
Author(s):  
Martin E. Alexander
Keyword(s):  
Forest Fire ◽  
International System ◽  
Unit Length ◽  
Fire Behavior ◽  
Energy Output ◽  
Fire Intensity ◽  
Linear Rate ◽  
Fire Front ◽  
Quantitative Basis ◽  
The Impact

Frontal fire intensity is a valid measure of forest fire behavior that is solely a physical attribute of the fire itself. It is defined as the energy output rate per unit length of fire front and is directly related to flame size. Numerically, it is equal to the product of net heat of combustion, quantity of fuel consumed in the active combustion zone, and a spreading fire's linear rate of advance. The recommended International System (SI) units are kilowatts per metre. This concept of fire intensity provides a quantitative basis for fire description useful in evaluating the impact of fire on forest ecosystems.

scholarly journals Remote sensing techniques to assess active fire characteristics and post-fire effects

2006 ◽  
Vol 15 (3) ◽  
pp. 319 ◽  
Author(s):  
Leigh B. Lentile ◽  
Zachary A. Holden ◽  
Alistair M. S. Smith ◽  
Michael J. Falkowski ◽  
Andrew T. Hudak ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Fire Severity ◽  
Fire Behavior ◽  
Fire Effects ◽  
Ecological Effects ◽  
Fire Intensity ◽  
Active Fire ◽  
Post Fire Effects ◽  
Remote Sensing Techniques ◽  
Fire Characteristics

Space and airborne sensors have been used to map area burned, assess characteristics of active fires, and characterize post-fire ecological effects. Confusion about fire intensity, fire severity, burn severity, and related terms can result in the potential misuse of the inferred information by land managers and remote sensing practitioners who require unambiguous remote sensing products for fire management. The objective of the present paper is to provide a comprehensive review of current and potential remote sensing methods used to assess fire behavior and effects and ecological responses to fire. We clarify the terminology to facilitate development and interpretation of comprehensible and defensible remote sensing products, present the potential and limitations of a variety of approaches for remotely measuring active fires and their post-fire ecological effects, and discuss challenges and future directions of fire-related remote sensing research.

Fuel treatments alter the effects of wildfire in a mixed-evergreen forest, Oregon, USA

2005 ◽  
Vol 35 (12) ◽  
pp. 2981-2995 ◽  
Author(s):  
Crystal L Raymond ◽  
David L Peterson
Keyword(s):  
Tree Mortality ◽  
Fire Regime ◽  
Fire Severity ◽  
Fire Behavior ◽  
Evergreen Forest ◽  
Fire Intensity ◽  
Crown Fire ◽  
Fuel Loading ◽  
Fuel Treatments ◽  
Surface Fire

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.

scholarly journals Impacts of Forest Thinning on Wildland Fire Behavior

Forests ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 918 ◽  
Author(s):  
Tirtha Banerjee
Keyword(s):  
Wind Speed ◽  
Wildland Fire ◽  
Fire Severity ◽  
Fire Behavior ◽  
Fire Intensity ◽  
Fuel Moisture ◽  
Forest Thinning ◽  
Rate Of Spread ◽  
Wide Range ◽  
Actual Fire

Key message: We have explored the impacts of forest thinning on wildland fire behavior using a process based model. Simulating different degrees of thinning, we found out that forest thinning should be conducted cautiously as there could be a wide range of outcomes depending upon the post-thinning states of fuel availability, fuel connectivity, fuel moisture and micrometeorological features such as wind speed. Context: There are conflicting reports in the literature regarding the effectiveness of forest thinning. Some studies have found that thinning reduces fire severity, while some studies have found that thinning might lead to enhanced fire severity. Aims: Our goal was to evaluate if both of these outcomes are possible post thinning operations and what are the limiting conditions for post thinning fire behavior. Methods: We used a process based model to simulate different degrees of thinning systematically, under two different conditions, where the canopy fuel moisture was unchanged and when the canopy fuel moisture was also depleted post thinning. Both of these scenarios are reported in the literature. Results: We found out that a low degree of thinning can indeed increase fire intensity, especially if the canopy fuel moisture is low. A high degree of thinning was effective in reducing fire intensity. However, thinning also increased rate of spread under some conditions. Interestingly, both intensity and rate of spread were dependent on the competing effects of increased wind speed, fuel loading and canopy fuel moisture. Conclusion: We were able to find the limits of fire behavior post thinning and actual fire behavior is likely to be somewhere in the middle of the theoretical extremes explored in this work. The actual fire behavior post thinning should depend on the site specific conditions which would determine the outcome of the interplay among the aforementioned conditions. The work also highlights that policymakers should be careful about fine scale canopy architectural attributes and micrometeorological aspects when planning fuel treatment operations.

scholarly journals Urban Fire Severity and Vegetation Dynamics in Southern California

2020 ◽  
Vol 13 (1) ◽  
pp. 19
Author(s):  
Lauren E. H. Mathews ◽  
Alicia M. Kinoshita
Keyword(s):  
Vegetation Cover ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Current Knowledge ◽  
Fire Severity ◽  
Satellite Image ◽  
Burn Severity ◽  
Native Vegetation ◽  
Riparian Areas ◽  
The Impact

A combination of satellite image indices and in-field observations was used to investigate the impact of fuel conditions, fire behavior, and vegetation regrowth patterns, altered by invasive riparian vegetation. Satellite image metrics, differenced normalized burn severity (dNBR) and differenced normalized difference vegetation index (dNDVI), were approximated for non-native, riparian, or upland vegetation for traditional timeframes (0-, 1-, and 3-years) after eleven urban fires across a spectrum of invasive vegetation cover. Larger burn severity and loss of green canopy (NDVI) was detected for riparian areas compared to the uplands. The presence of invasive vegetation affected the distribution of burn severity and canopy loss detected within each fire. Fires with native vegetation cover had a higher severity and resulted in larger immediate loss of canopy than fires with substantial amounts of non-native vegetation. The lower burn severity observed 1–3 years after the fires with non-native vegetation suggests a rapid regrowth of non-native grasses, resulting in a smaller measured canopy loss relative to native vegetation immediately after fire. This observed fire pattern favors the life cycle and perpetuation of many opportunistic grasses within urban riparian areas. This research builds upon our current knowledge of wildfire recovery processes and highlights the unique challenges of remotely assessing vegetation biophysical status within urban Mediterranean riverine systems.

scholarly journals Effects of Soil Abiotic and Biotic Factors on Tree Seedling Regeneration Following a Boreal Forest Wildfire

Ecosystems ◽  
2021 ◽  
Author(s):  
Theresa S. Ibáñez ◽  
David A. Wardle ◽  
Michael J. Gundale ◽  
Marie-Charlotte Nilsson
Keyword(s):  
Boreal Forest ◽  
Betula Pendula ◽  
Fire Severity ◽  
Tree Regeneration ◽  
Soil Biota ◽  
Fire Disturbance ◽  
Burn Severity ◽  
Soil Conditions ◽  
Tree Seedling ◽  
Seedling Regeneration

AbstractWildfire disturbance is important for tree regeneration in boreal ecosystems. A considerable amount of literature has been published on how wildfires affect boreal forest regeneration. However, we lack understanding about how soil-mediated effects of fire disturbance on seedlings occur via soil abiotic properties versus soil biota. We collected soil from stands with three different severities of burning (high, low and unburned) and conducted two greenhouse experiments to explore how seedlings of tree species (Betula pendula, Pinus sylvestris and Picea abies) performed in live soils and in sterilized soil inoculated by live soil from each of the three burning severities. Seedlings grown in live soil grew best in unburned soil. When sterilized soils were reinoculated with live soil, seedlings of P. abies and P. sylvestris grew better in soil from low burn severity stands than soil from either high severity or unburned stands, demonstrating that fire disturbance may favor post-fire regeneration of conifers in part due to the presence of soil biota that persists when fire severity is low or recovers quickly post-fire. Betula pendula did not respond to soil biota and was instead driven by changes in abiotic soil properties following fire. Our study provides strong evidence that high fire severity creates soil conditions that are adverse for seedling regeneration, but that low burn severity promotes soil biota that stimulates growth and potential regeneration of conifers. It also shows that species-specific responses to abiotic and biotic soil characteristics are altered by variation in fire severity. This has important implications for tree regeneration because it points to the role of plant–soil–microbial feedbacks in promoting successful establishment, and potentially successional trajectories and species dominance in boreal forests in the future as fire regimes become increasingly severe through climate change.

scholarly journals Predicting wildfire impacts on the prehistoric archaeological record of the Jemez Mountains, New Mexico, USA

Fire Ecology ◽  
2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Megan M. Friggens ◽  
Rachel A. Loehman ◽  
Connie I. Constan ◽  
Rebekah R. Kneifel
Keyword(s):  
New Mexico ◽  
Fire Severity ◽  
Fire Effects ◽  
Burn Severity ◽  
Fire Season ◽  
Archaeological Sites ◽  
Archaeological Record ◽  
Human Environment ◽  
Jemez Mountains ◽  
Archaeological Materials

Abstract Background Wildfires of uncharacteristic severity, a consequence of climate changes and accumulated fuels, can cause amplified or novel impacts to archaeological resources. The archaeological record includes physical features associated with human activity; these exist within ecological landscapes and provide a unique long-term perspective on human–environment interactions. The potential for fire-caused damage to archaeological materials is of major concern because these resources are irreplaceable and non-renewable, have social or religious significance for living peoples, and are protected by an extensive body of legislation. Although previous studies have modeled ecological burn severity as a function of environmental setting and climate, the fidelity of these variables as predictors of archaeological fire effects has not been evaluated. This study, focused on prehistoric archaeological sites in a fire-prone and archaeologically rich landscape in the Jemez Mountains of New Mexico, USA, identified the environmental and climate variables that best predict observed fire severity and fire effects to archaeological features and artifacts. Results Machine learning models (Random Forest) indicate that topography and variables related to pre-fire weather and fuel condition are important predictors of fire effects and severity at archaeological sites. Fire effects were more likely to be present when fire-season weather was warmer and drier than average and within sites located in sloped, treed settings. Topographic predictors were highly important for distinguishing unburned, moderate, and high site burn severity as classified in post-fire archaeological assessments. High-severity impacts were more likely at archaeological sites with southern orientation or on warmer, steeper, slopes with less accumulated surface moisture, likely associated with lower fuel moistures and high potential for spreading fire. Conclusions Models for predicting where and when fires may negatively affect the archaeological record can be used to prioritize fuel treatments, inform fire management plans, and guide post-fire rehabilitation efforts, thus aiding in cultural resource preservation.

Fire regime impacts on post-fire diurnal land surface temperature change over North American boreal forest

2021 ◽  
Author(s):  
Jie Zhao ◽  
Chao Yue ◽  
Philippe Ciais ◽  
Xin Hou ◽  
Qi Tian
Keyword(s):  
Climate Change ◽  
Regression Analysis ◽  
Land Surface ◽  
Fire Regime ◽  
Fire Severity ◽  
Linear Regression Analysis ◽  
Fire Regimes ◽  
Fire Intensity ◽  
Surface Temperature Change ◽  
One Year

<p>Wildfire is the most prevalent natural disturbance in the North American boreal (BNA) forest and can cause post-fire land surface temperature change (ΔLST<sub>fire</sub>) through biophysical processes. Fire regimes, such as fire severity, fire intensity and percentage of burned area (PBA), might affect ΔLST<sub>fire</sub> through their impacts on post-fire vegetation damage. However, the difference of the influence of different fire regimes on the ΔLST<sub>fire</sub> has not been quantified in previous studies, despite ongoing and projected changes in fire regimes in BNA in association with climate change. Here we employed satellite observations and a space-and-time approach to investigate diurnal ΔLST<sub>fire</sub> one year after fire across BNA. We further examined potential impacts of three fire regimes (i.e., fire intensity, fire severity and PBA) and latitude on ΔLST<sub>fire</sub> by simple linear regression analysis and multiple linear regression analysis in a stepwise manner. Our results demonstrated pronounced asymmetry in diurnal ΔLST<sub>fire</sub>, characterized by daytime warming in contrast to nighttime cooling over most BNA. Such diurnal ΔLST<sub>fire</sub> also exhibits a clear latitudinal pattern, with stronger daytime warming and nighttime cooling one year after fire in lower latitudes, whereas in high latitudes fire effects are almost neutral. Among the fire regimes, fire severity accounted for the most (43.65%) of the variation of daytime ΔLST<sub>fire</sub>, followed by PBA (11.6%) and fire intensity (8.5%). The latitude is an important factor affecting the influence of fire regimes on daytime ΔLST<sub>fire</sub>. The sensitivity of fire intensity and PBA impact on daytime ΔLST<sub>fire</sub> decreases with latitude. But only fire severity had a significant effect on nighttime ΔLST<sub>fire</sub> among three fire regimes. Our results highlight important fire regime impacts on daytime ΔLST<sub>fire</sub>, which might play a critical role in catalyzing future boreal climate change through positive feedbacks between fire regime and post-fire surface warming.</p>

scholarly journals COMPORTAMENTO DO FOGO EM QUEIMAS CONTROLADAS DE VEGETAÇÃO DE ESTEPE NO MUNICÍPIO DE PALMEIRA, PARANÁ, BRASIL

FLORESTA ◽  
2013 ◽  
Vol 43 (4) ◽  
pp. 557
Author(s):  
Celso Darci Seger ◽  
Antonio Carlos Batista ◽  
Alexandre França Tetto ◽  
Ronaldo Viana Soares
Keyword(s):  
Fire Behavior ◽  
Fire Risk ◽  
Fire Spread ◽  
Flame Height ◽  
Fire Intensity ◽  
Average Moisture Content ◽  
Fuel Loading ◽  
Prescribed Burns ◽  
Controlled Burning ◽  
Heat Released

As queimas controladas constituem práticas de manejo utilizadas em diferentes tipos de vegetação e difundidas em vários países. No entanto, para a realização de tais práticas com segurança e eficiência é fundamental o conhecimento do comportamento do fogo. O objetivo desse trabalho foi caracterizar o comportamento do fogo em queimas controladas de vegetação Estepe Gramíneo-Lenhosa no estado do Paraná. Para isso, foi instalado um experimento no município de Palmeira, onde 20 parcelas foram queimadas, sendo metade a favor e metade contra o vento. A carga de material combustível fino estimada foi de 2,26 kg.m-2, com teor médio de umidade de 50,45%. A quantidade de material consumido pela queima foi de 1,76 kg.m-2, com uma eficiência média de queima de 76,86%. As médias obtidas, a favor e contra o vento, foram respectivamente: velocidade de propagação do fogo de 0,049 e 0,012 m.s-1, altura das chamas de 1,34 e 0,843 m, intensidade do fogo de 210,53 e 50,68 kcal.m-1.s-1 e calor liberado de 4.067,19 e 4.508,92 kcal.m-2. Os resultados permitiram concluir que as queimas controladas em vegetação de campos naturais, realizadas dentro dos critérios estabelecidos de planos de queima, são viáveis e seguras sob o ponto de vista de perigo de incêndios.Palavras chave: Queima prescrita; material combustível; intensidade do fogo; perigo de incêndios. AbstractFire behavior of prescribed burns in grassland on Palmeira county, Paraná, Brazil. The prescribed burns are practices of management used in different types of vegetation and widespread in several countries. However, to carry out such practices safely and effectively is fundamental knowledge of fire behavior. The aim of this study was to characterize the fire behavior in controlled burning of grassland vegetation in Paraná state. For this, an experiment was conducted in Palmeira County, where 20 plots were burned, half in favor and half against the wind. The estimated fine fuel loading was 2.26 kg.m-2, with average moisture content of 50.45%. The fuel consumption by burning was 1.76 kg.m-2 with an average efficiency of burning of 76.86%. The averages, for and against the wind, were: speed of fire spread of 0.049 and 0.012 m.s-1, the flame height of 1.34 m and 0.843, fire intensity of 210.53 and 50.68 kcal.m-1.s-1 and heat released from 4,067.19 and 4,508.92 kcal.m-2. The results show that the controlled burnings of grasslands vegetation, carried out within the established criteria burning plans are feasible and safe from the aspect of fire danger.Keywords: Prescribed burns; fuel loading; fire intensity; fire risk.

Mobile X-Pol Radar: A New Tool for Investigating Pyroconvection and Associated Wildfire Meteorology

2018 ◽  
Vol 99 (6) ◽  
pp. 1177-1195 ◽  
Author(s):  
Nicholas McCarthy ◽  
Hamish McGowan ◽  
Adrien Guyot ◽  
Andrew Dowdy
Keyword(s):  
Multispectral Imaging ◽  
Doppler Radar ◽  
Fire Behavior ◽  
Time Lapse ◽  
Fire Intensity ◽  
Prescribed Burn ◽  
X Band ◽  
Turbulent Characteristics ◽  
Convective Plume ◽  
Dual Polarized

AbstractThe process of pyroconvection occurs when fire-released heat, moisture, and/or aerosols induce or augment convection in the atmosphere. Prediction of pyroconvection presents a set of complex problems for meteorologists and wildfire managers. In particular, the turbulent characteristics of a pyroconvective plume exert bidirectional feedback on fire behavior, often with resulting severe impacts on life and property. Here, we present the motivation, field strategy, and initial results from the Bushfire Convective Plume Experiment, which through the use of mobile radar aims to quantify the kinematics of pyroconvection and its role in fire behavior. The case studies presented include world-first observations from two wildfires and one prescribed burn using the University of Queensland’s portable, dual-polarized X-band Doppler radar (UQ-XPOL). The initial analyses of reflectivity, Doppler winds, polarimetric variables, and spectrum width data provide insights into these relatively unexplored datasets within the context of pyroconvection. Weather radar data are supported by mesonet observations, time-lapse photography, airborne multispectral imaging, and spot-fire mapping. The ability to combine ground-validated fire intensity and progression at an hourly scale with quantitative data documenting the evolution of the convective plume kinematics at the scale of hundreds of meters represents a new capability for advancing our understanding of wildfires. The results demonstrate the suitability of portable, dual-polarized X-band Doppler radar to investigate pyroconvection and associated plume dynamics.

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