Analysis of the prescribed burning practice in the pine forest of northwestern Portugal

The ignition of low-intensity fires in the dormant season in the pine stands of north-western Portugal seeks to reduce the existing fuel hazard without compromising site quality. The purpose of this study is to characterise this practice and assess its effectiveness, based on information resulting from the normal monitoring process at the management level, and using operational guidelines, fire behaviour models and a newly developed method to classify prescribed fire severity. Although the region's humid climate strongly constrains the activity of prescribed fire, 87% of the fires analysed were undertaken under acceptable meteorological and fuel moisture conditions. In fact, most operations achieved satisfactory results. On average, prescribed fire reduces by 96% the potential intensity of a wildfire occurring under extreme weather conditions, but 36% of the treated sites would still require heavy fire fighting resources to suppress such fire, and 17% would still carry it in the tree canopy. Only 10% of the prescribed burns have an excessive impact on trees or the forest floor, while 89% (normal fire weather) or 59% (extreme fire weather) comply with both ecological integrity maintenance and wildfire protection needs. Improved planning and monitoring procedures are recommended in order to overcome the current deficiencies.     

Fire hazard after prescribed burning in a gorse shrubland: implications for fuel management

Prescribed burning is commonly used to prevent accumulation of biomass in fire-prone shrubland in NW Spain. However, there is a lack of knowledge about the efficacy of the technique in reducing fire hazard in these ecosystems. Fire hazard in burned shrubland areas will depend on the initial capacity of woody vegetation to recover and on the fine ground fuels existing after fire. To explore the effect that time since burning has on fire hazard, experimental tests were performed with two fuel complexes (fine ground fuels and regenerated shrubs) resulting from previous prescribed burnings conducted in a gorse shrubland (Ulex europaeus L.) one, three and five years earlier. A point-ignition source was used in burning experiments to assess ignition and initial propagation success separately for each fuel complex. The effect of wind speed was also studied for shrub fuels, and several flammability parameters were measured. Results showed that both ignition and initial propagation success of fine ground fuels mainly depended on fuel depth and were independent of time since burning, although flammability parameters indicated higher fire hazard three years after burning. In contrast, time since burning increased ignition and initial propagation success of regenerated shrub fuels, as well as the flammability parameters assessed, but wind speed had no significant effect. The combination of results of fire hazard for fine ground fuels and regenerated shrubs according to the variation in relative coverage of each fuel type after prescribed burning enabled an assessment of integrated fire hazard in treated areas. The present results suggest that prescribed burning is a very effective technique to reduce fire hazard in the study area, but that fire hazard will be significantly increased by the third year after burning. These results are valuable for fire prevention and fuel management planning in gorse shrubland areas.     

Factors influencing fire behaviour in shrublands of different stand ages and the implications for using prescribed burning to reduce wildfire risk

Fire behaviour under experimental conditions is described in nine Mediterranean gorse shrublands ranging from 3-12 years of age with different fuel loads. Significant differences in the fire-line intensity, fuel load and rate of fire spread have been found to be related to the stage of development of the communities. Fire spread is correlated with fuel moisture using multiple regression techniques. Differences in fuel moisture between mature and young communities under moderate weather conditions have been found. The lower moisture content identified in the mature shrubland is due both to the decreasing moisture content of senescent shrubland in some species, mainly in live fractions of Ulex parviflorus Pour. fuel, and to a substantial increase in dead fuel fractions with low percentages of moisture content. The result is that the older the shrubland is, the greater will be the decrease in the total moisture content of the vegetation. In these moderate weather conditions, the fire intensity of the mature community was as high as the maximum intensity recommended for prescribed fires. This fact seems to indicate that, even under moderate conditions, prescribed burning as an alternative management tool in the mature shrubland must always take into account fuel control; on the other hand, this technique could be applied more easily when the shrubland is at an intermediate growth stage (4-5 years of age). Therefore, more frequent low-intensity prescribed fires are indicated to abate the risk of catastrophic fire.     

Wildfire effects on hiking and biking demand in New Mexico: a travel cost study

We use a travel cost model to test the effects of wild and prescribed fire on visitation by hikers and mountain bikers in New Mexico. Our results indicate that net benefits for mountain bikers is $150 per trip and that they take an average of 6.2 trips per year. Hikers take 2.8 trips per year with individual net benefits per trip of $130. Both hikers' and mountain bikers' demand functions react adversely to prescribed burning. Net benefits for both groups fall as areas recover from prescribed burns. Because both visitation and annual recreation benefits decrease to these two types of visitors, this gives rise to multiple use costs associated with prescribed burning. With respect to wildfire, hikers and mountain bikers both exhibit decreased visitation as areas recover from wildfires, however, only hikers indicate an increase in per trip net benefits. Bikers' demand effectively drops to zero. These results differ from previous findings in the literature and have implications for efficient implementation of the National Fire Plan and whether prescribed burning is a cost effective tool for multiple use management of National Forests. Specifically, that fire and recreation managers cannot expect recreation users to react similarly to fire across recreation activities, or different geographic regions. What is cost effective in one region may not be so in another.     

Modeling postfire conifer mortality for long-range planning

A model is presented for predicting mortality of conifers after wildfire. The model requires stand data inputs and is linked with a mathematical fire behavior model that calculates fireline intensity. Fraction of crown volume killed is calculated for each species in a stand based on mensurational data. Duration of lethal heat at the base of trees is calculated from fuel consumption and burning time values. Fraction of crown volume killed and the ratio of critical time for cambial kill to duration of lethal heat are independent variables in a function that calculates probability of mortality. The model produces reasonable estimates of stand mortality for fire and site characteristics found in the northern Rocky Mountains, USA. It has a broad resolution appropriate for use in fire management planning and has potential applications for coniferous forests throughout the United States.     

Predicted effects of prescribed burning and harvesting on forest recovery and sustainability in southwest Georgia, USA

A model-based analysis of the effect of prescribed burning and forest thinning or clear-cutting on stand recovery and sustainability was conducted at Fort Benning, GA, in the southeastern USA. Two experiments were performed with the model. In the first experiment, forest recovery from degraded soils was predicted for 100 years with or without prescribed burning. In the second experiment simulations began with 100 years of predicted stand growth, then forest sustainability was predicted for an additional 100 years under different combinations of prescribed burning and forest harvesting. Three levels of fire intensity (low, medium, and high), that corresponded to 17%, 33%, and 50% consumption of the forest floor C stock by fire, were evaluated at 1-, 2-, and 3-year fire return intervals. Relative to the control (no fire), prescribed burning with a 2- or 3-year return interval caused only a small reduction in predicted steady state soil C stocks (< or =25%) and had no effect on steady state tree wood biomass, regardless of fire intensity. Annual high intensity burns did adversely impact forest recovery and sustainability (after harvesting) on less sandy soils, but not on more sandy soils that had greater N availability. Higher intensity and frequency of ground fires increased the chance that tree biomass would not return to pre-harvest levels. Soil N limitation was indicated as the cause of unsustainable forests when prescribed burns were too frequent or too intense to permit stand recovery.     

Trying Not to Get Burned: Understanding Homeowners’ Wildfire Risk–Mitigation Behaviors

Three causes have been identified for the spiraling cost of wildfire suppression in the United States: climate change, fuel accumulation from past wildfire suppression, and development in fire-prone areas. Because little is likely to be performed to halt the effects of climate on wildfire risk, and because fuel-management budgets cannot keep pace with fuel accumulation let alone reverse it, changing the behaviors of existing and potential homeowners in fire-prone areas is the most promising approach to decreasing the cost of suppressing wildfires in the wildland–urban interface and increasing the odds of homes surviving wildfire events. Wildfire education efforts encourage homeowners to manage their property to decrease wildfire risk. Such programs may be more effective with a better understanding of the factors related to homeowners’ decisions to undertake wildfire risk–reduction actions. In this study, we measured whether homeowners had implemented 12 wildfire risk–mitigation measures in 2 Colorado Front Range counties. We found that wildfire information received from local volunteer fire departments and county wildfire specialists, as well as talking with neighbors about wildfire, were positively associated with higher levels of mitigation. Firsthand experience in the form of preparing for or undertaking an evacuation was also associated with a higher level of mitigation. Finally, homeowners who perceived higher levels of wildfire risk on their property had undertaken higher levels of wildfire-risk mitigation on their property.     

Use of prescribed burning for managing natural and historic resources in Chickamauga and Chattanooga National Military Park,USA

The purpose of this study was to provide the National Park Service with quantitative information regarding the effect of fire on fuel loads and pest species such asLonicera japonica, Ligustrum sinense, andRhus radicans.Three study areas of ten plots each were located in Chickamauga Battlefield Reservation of the Chickamauga and Chattanooga National Military Park. Fuel weights, aboveground biomass of honeysuckle, and counts of privet and poison ivy were collected both before and after prescribed fire. Additionally, one fourth of each of 14 plots was treated with glyphosate (tradename Roundup) to test for the use of fire as a herbicide pretreatment. This was a randomized block design with subsampling.Prescribed burning did significantly ( = 0.05) reduce fuel loads and the biomass of honeysuckle on burned plots. There was a statistically different response in fuel load reduction between fall and winter burns. Poison ivy significantly increased on burned plots, while privet counts did not vary significantly.Applications of glyphosate negatively impacted all three target species. Honeysuckle appeared to be damaged more readily on untreated plots, while no difference in response was noted on privet. Significantly more poison ivy growing points were killed by herbicide applications on burned plots than on unburned plots.     

Risk and cooperation: managing hazardous fuel in mixed ownership landscapes

Managing natural processes at the landscape scale to promote forest health is important, especially in the case of wildfire, where the ability of a landowner to protect his or her individual parcel is constrained by conditions on neighboring ownerships. However, management at a landscape scale is also challenging because it requires cooperation on plans and actions that cross ownership boundaries. Cooperation depends on people's beliefs and norms about reciprocity and perceptions of the risks and benefits of interacting with others. Using logistic regression tests on mail survey data and qualitative analysis of interviews with landowners, we examined the relationship between perceived wildfire risk and cooperation in the management of hazardous fuel by nonindustrial private forest (NIPF) owners in fire-prone landscapes of eastern Oregon. We found that NIPF owners who perceived a risk of wildfire to their properties, and perceived that conditions on nearby public forestlands contributed to this risk, were more likely to have cooperated with public agencies in the past to reduce fire risk than owners who did not perceive a risk of wildfire to their properties. Wildfire risk perception was not associated with past cooperation among NIPF owners. The greater social barriers to private-private cooperation than to private-public cooperation, and perceptions of more hazardous conditions on public compared with private forestlands may explain this difference. Owners expressed a strong willingness to cooperate with others in future cross-boundary efforts to reduce fire risk, however. We explore barriers to cooperative forest management across ownerships, and identify models of cooperation that hold potential for future collective action to reduce wildfire risk.     

Uncertainty and risk in wildland fire management: a review

Wildland fire management is subject to manifold sources of uncertainty. Beyond the unpredictability of wildfire behavior, uncertainty stems from inaccurate/missing data, limited resource value measures to guide prioritization across fires and resources at risk, and an incomplete scientific understanding of ecological response to fire, of fire behavior response to treatments, and of spatiotemporal dynamics involving disturbance regimes and climate change. This work attempts to systematically align sources of uncertainty with the most appropriate decision support methodologies, in order to facilitate cost-effective, risk-based wildfire planning efforts. We review the state of wildfire risk assessment and management, with a specific focus on uncertainties challenging implementation of integrated risk assessments that consider a suite of human and ecological values. Recent advances in wildfire simulation and geospatial mapping of highly valued resources have enabled robust risk-based analyses to inform planning across a variety of scales, although improvements are needed in fire behavior and ignition occurrence models. A key remaining challenge is a better characterization of non-market resources at risk, both in terms of their response to fire and how society values those resources. Our findings echo earlier literature identifying wildfire effects analysis and value uncertainty as the primary challenges to integrated wildfire risk assessment and wildfire management. We stress the importance of identifying and characterizing uncertainties in order to better quantify and manage them. Leveraging the most appropriate decision support tools can facilitate wildfire risk assessment and ideally improve decision-making.     

Exploring the ‘Issue-Attention Cycle’: Does Length of Time Since Wildfire Predict Social Acceptability of Prescribed Burning?

Environmental Management - Social acceptability of environmental management actions, such as prescribed burning used to reduce wildfire risk, is critical to achieving positive outcomes. However,...     

Fire effects on stable isotopes in a Sierran forested watershed

This study tested the hypothesis that stable C and N isotope values in surface soil and litter would be increased by fire due to volatilization of lighter isotopes. The hypothesis was tested by: (1) performing experimental laboratory burns of organic and mineral soil materials from a watershed at combinations of temperature ranging 100 to 600 degrees C and duration ranging from 1 to 60 min; (2) testing field samples of upland soils before, shortly after, and 1 yr following a wildfire in the same watershed; and (3) testing field soil samples from a down-gradient ash/sediment depositional area in a riparian zone following a runoff event after the wildfire. Muffle furnace results indicated the most effective temperature range for using stable isotopes for tracing fire impacts is 200 to 400 degrees C because lower burn temperatures may not produce strong isotopic shifts, and at temperatures>or=600 degrees C, N and C content of residual material is too low. Analyses of field soil samples were inconclusive: there was a slightly significant effect of the wildfire on delta15N values in upland watershed analyses 1 yr postburn, while riparian zone analyses results indicated that delta13C values significantly decreased approximately 0.71 per thousand over a 9 mo post-fire period (p=0.015), and ash/sediment layer delta13C values were approximately 0.65 per thousand higher than those in the A horizon. The lack of field confirmation may have been due to overall wildfire burn temperatures being <200 degrees C and/or microbial recovery and vegetative growth in the field. Thus, the muffle furnace experiment supported the hypothesis, but it is as yet unconfirmed by actual wildfire field data.     

Phosphorus release from ash and remaining tissues of two wetland species after a prescribed fire

Dead plant tissues and ash from a prescribed fire play an important role in nutrient balance and cycling in the Florida Everglades ecosystem. The objective of this study was to assess the dynamic changes in total phosphorus release (TPr) from ash or tissues of either cattail (Typha domingensis Pers.) or sawgrass (Cladium jamaicense Crantz) to water. Natural-dead (senesced-dead) and burning-dead (standing-dead due to a prescribed fire) cattail and sawgrass were collected from highly (H) and moderately (M) impacted zones in the Florida Everglades. This experiment was conducted by incubation and water-extraction of the materials in plastic bottles for 65 d at room temperature (24 +/- 1 degrees C). Results showed that 63 to 88%, 17 to 48%, 9 to 20%, and 13 to 28% of total P (TPp) were released as TPr from cattail and sawgrass ash, cattail tissues from the H zone, cattail tissues, and sawgrass tissues from the M zone, respectively. TPp means total P of plant tissues, whereas TPr is total P release from the tissues or ash. Most of the TPr was released within 24 h after burning. The quick release of TPr observed in this experiment may help explain the P surge in the surface water immediately following a fire in the marsh. These findings suggest that prescribed burning accelerates P release from cattail and sawgrass. They also imply that it is very important to keep the water stagnant in the first 24 h to maximize the benefits of a prescribed fire in the Everglades.     

Seeking knowledge of traditional Indigenous burning practices to inform regional bushfire management

ABSTRACT

A transdisciplinary review of the current academic knowledge of Indigenous traditional fire management is presented for the Mt Lofty Ranges in South Australia. For a long time, the roles of Indigenous management of the landscape have either been overlooked or discounted within environmental studies. That situation is beginning to change in many parts of Australia. However, this review of knowledge of traditional Indigenous burning practices specifically for the Mt Lofty Ranges suggests that there is very little formalised, academic knowledge available that could be utilised to inform prescribed burning practices in the region. Perhaps Indigenous peoples’ use of fire was strongly governed by individual choices, or perhaps established regimes demarcated roles across groups; perhaps some areas were burnt regularly and others were left unaltered – there is still no clear evidence from the academic literature to provide even limited understandings of such elements of pre-colonial fire regimes. That gap in knowledge will become increasingly problematic as the need for appropriate, sophisticated burning practices to respond to risk in peri-urban Adelaide increases with a changing climate. To learn from traditional Indigenous land management: (a) formal knowledge needs to be generated on past regional burning practices; and (b) understanding needs to be developed as to whether past burning practices could lead to effective hazard management and biodiversity outcomes within contemporary landscapes. Such an integration of Indigenous knowledge for effective environmental management will only be possible if the injustices of past exclusions of the importance of Indigenous biocultural practices are recognised.     

Land use planning and wildfire risk mitigation: an analysis of wildfire-burned subdivisions using high-resolution remote sensing imagery and GIS data

This paper evaluates risk factors that influence the probability that a house will burn from wildfire. A logistic regression is used to analyse data processed from pre-fire and post-fire IKONOS images and other geo-referenced data. The dependent variable is the probability that a given house will burn. A total of 12 independent variables are evaluated: vegetation density; area of defensible space; adjacency of a parcel to public lands; proximity of a house to fire station; road width; road type; parcel size; subdivision morphology; assessed value; elevation; slope and aspect. Model results generally support dominant land use planning and design strategies for wildfire risk reduction including vegetation treatments, site selection with respect to topography, and improving access to fire stations.     

The management implications of fine fuel dynamics in Bushlands Surrounding Hobart, Tasmania

Hobart's bushlands consist of eight distinct vegetation types ranging from open woodland to wet forest. Fine fuel accumulation characteristics are distinctive across this range of vegetation types and mostly seem to conform to the function W_t = W_ss(1−e^−kt)+ l·92(e^−kt), although there is considerable scatter around the lines of best fit in many types.This information contributes to determining the applicability and appropriate frequency of controlled burning as a means of reducing fuels to protect life and property from wildfire. Regular burning of grassy vegetation should ensure relatively safe zones within the urban/bush matrix. It is likely that burning heathy forest types at frequencies that would ensure safe fuel loads would be ecologically detrimental. It would be difficult and futile to use fuel reduction burning in wet forest types as a means of protecting life and property. The fuel accumulation characteristics and the existing ecological knowledge of Allocasuarina verticillata shrubland suggests that fuel reduction burning would be counter-productive in this vegetation type.     

Optimization of the Resources Management in Fighting Wildfires

Wildfires lead to important economic, social, and environmental losses, especially in areas of Mediterranean climate where they are of a high intensity and frequency. Over the past 30 years there has been a dramatic surge in the development and use of fire spread models. However, given the chaotic nature of environmental systems, it is very difficult to develop real-time fire-extinguishing models. This article proposes a method of optimizing the performance of wildfire fighting resources such that losses are kept to a minimum. The optimization procedure includes discrete simulation algorithms and Bayesian optimization methods for discrete and continuous problems (simulated annealing and Bayesian global optimization). Fast calculus algorithms are applied to provide optimization outcomes in short periods of time such that the predictions of the model and the real behavior of the fire, combat resources, and meteorological conditions are similar. In addition, adaptive algorithms take into account the chaotic behavior of wildfire so that the system can be updated with data corresponding to the real situation to obtain a new optimum solution. The application of this method to the Northwest Forest of Madrid (Spain) is also described. This application allowed us to check that it is a helpful tool in the decision-making process.     

Greenhouse Impact Due to the Use of Combustible Fuels: Life Cycle Viewpoint and Relative Radiative Forcing Commitment

Extensive information on the greenhouse impacts of various human actions is important in developing effective climate change mitigation strategies. The greenhouse impacts of combustible fuels consist not only of combustion emissions but also of emissions from the fuel production chain and possible effects on the ecosystem carbon storages. It is important to be able to assess the combined, total effect of these different emissions and to express the results in a comprehensive way. In this study, a new concept called relative radiative forcing commitment (RRFC) is presented and applied to depict the greenhouse impact of some combustible fuels currently used in Finland. RRFC is a ratio that accounts for the energy absorbed in the Earth system due to changes in greenhouse gas concentrations (production and combustion of fuel) compared to the energy released in the combustion of fuel. RRFC can also be expressed as a function of time in order to give a dynamic cumulative picture on the caused effect. Varying time horizons can be studied separately, as is the case when studying the effects of different climate policies on varying time scales. The RRFC for coal for 100 years is about 170, which means that in 100 years 170 times more energy is absorbed in the atmosphere due to the emissions of coal combustion activity than is released in combustion itself. RRFC values of the other studied fuel production chains varied from about 30 (forest residues fuel) to 190 (peat fuel) for the 100-year study period. The length of the studied time horizon had an impact on the RRFC values and, to some extent, on the relative positions of various fuels.