A Comparison of Fuel Reduction Methods for Wildfire Risk Management and Climate Change Resiliency in Mixed Conifer Forests in the Sierra Nevada PDF Download
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Author: Heather Navle
Publisher:
ISBN:
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Languages : en
Pages :
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Wildfires in the mixed conifer forests of California's Sierra Nevada have been a common and natural disturbance for thousands of years, historically occurring every 3 to 30 years. The flora and fauna of the mixed conifer forest have evolved to depend on low to moderate severity wildfires for reproduction, foraging, and habitat. However, the Sierra Nevada has experienced dramatic environmental changes over the past ~150 years as a result of three main factors: wildfire suppression, climate change, and habitat loss. Because of the threat wildfires pose to human lives, property and timber harvest, they have been suppressed to an extent that has completely altered mixed conifer ecosystems. One of the changes to these ecosystems is increased vegetative fuel density, which can result in stand-replacing mega fires. To mitigate these high-severity mega wildfires, forest managers incorporate various fuel reduction methods into forest management plans. These impacts can have negative effects on forest ecosystems, degrading ecosystem characteristics that are critical for adapting to climate change. Thus, the two main objectives of this paper are to compare and contrast four different fuel reduction methods based on their effectiveness to (I) reduce wildfire risk and (II) promote climate change resiliency. The four fuel reduction methods are: low thinning, canopy thinning, selective thinning, and prescribed fire. These four fuel reduction methods have been compared in syntheses tables for the two main objectives. Qualitative and quantitative metric data, based on a literature review, were used to compare the optimal effects of each fuel reduction method. It was found that prescribed fire or thinning with prescribed fire resulted in the most optimal effects when considering both reduced wildfire risk and climate change resilience. However, tree mortality and the risk of fire escaping controlled boundaries are increased during prescribed fire operations. Additionally, results showed that all four fuel reduction methods displayed both positive and negative effects, depending on the metric used to evaluate the objective, which suggests that appropriate application of fuel reduction methods is highly variable depending on the goals and the environment. For example, canopy thinning alone may have desirable effects when prescribed fire is financially unfeasible or unsafe due to proximity to buildings. Applying prescribed fire is the most optimal fuel reduction method in most forest conditions; however, it is recommended that forest managers evaluate forest structure, density, and tree species prior to selecting the most appropriate fuel reduction method for their situation.
Author: Heather Navle
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Wildfires in the mixed conifer forests of California's Sierra Nevada have been a common and natural disturbance for thousands of years, historically occurring every 3 to 30 years. The flora and fauna of the mixed conifer forest have evolved to depend on low to moderate severity wildfires for reproduction, foraging, and habitat. However, the Sierra Nevada has experienced dramatic environmental changes over the past ~150 years as a result of three main factors: wildfire suppression, climate change, and habitat loss. Because of the threat wildfires pose to human lives, property and timber harvest, they have been suppressed to an extent that has completely altered mixed conifer ecosystems. One of the changes to these ecosystems is increased vegetative fuel density, which can result in stand-replacing mega fires. To mitigate these high-severity mega wildfires, forest managers incorporate various fuel reduction methods into forest management plans. These impacts can have negative effects on forest ecosystems, degrading ecosystem characteristics that are critical for adapting to climate change. Thus, the two main objectives of this paper are to compare and contrast four different fuel reduction methods based on their effectiveness to (I) reduce wildfire risk and (II) promote climate change resiliency. The four fuel reduction methods are: low thinning, canopy thinning, selective thinning, and prescribed fire. These four fuel reduction methods have been compared in syntheses tables for the two main objectives. Qualitative and quantitative metric data, based on a literature review, were used to compare the optimal effects of each fuel reduction method. It was found that prescribed fire or thinning with prescribed fire resulted in the most optimal effects when considering both reduced wildfire risk and climate change resilience. However, tree mortality and the risk of fire escaping controlled boundaries are increased during prescribed fire operations. Additionally, results showed that all four fuel reduction methods displayed both positive and negative effects, depending on the metric used to evaluate the objective, which suggests that appropriate application of fuel reduction methods is highly variable depending on the goals and the environment. For example, canopy thinning alone may have desirable effects when prescribed fire is financially unfeasible or unsafe due to proximity to buildings. Applying prescribed fire is the most optimal fuel reduction method in most forest conditions; however, it is recommended that forest managers evaluate forest structure, density, and tree species prior to selecting the most appropriate fuel reduction method for their situation.
Author: Eric Murphey Winford
Publisher:
ISBN: 9781267240040
Category :
Languages : en
Pages :
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The purpose of this research is to determine whether a forest thinning project conducted with the aim of reducing wildfire risk and restoring the forest to a more resilient condition can improve the carbon stores compared to a baseline, no-thin project. A life-cycle analysis was conducted on data from a case study of a fuels-reduction thinning operation at Independence Lake, a 700-acre lake north of Truckee, California in the northern Sierra Nevada. The calculation tracks the net ecosystem carbon balance, including above and below-ground carbon pools, removals from harvesting, and disturbance by wildfire. To make assessments of in-forest carbon stores, vegetation plots and a forest growth model are utilized. Trees that are removed are used to create energy and carbon that would have been emitted from comparative fossil fuel energy sources is counted. In this case study in the Sierra Nevada, with a frequent fire return interval common to mixed-conifer forests in the historic period, thinning to reduce fuels does provide greater carbon benefits than not thinning and letting the forest grow. In all cases, potential wildfire emissions are the greatest source of emissions. Direct emissions from mechanical treatments and transportation of the biomass are each about 1% of total emissions. Emissions from the combustion of biomass are slightly less than half of total emissions but less than potential wildfire emissions. The results indicate that wildfire frequency is the greatest determinant of whether or not the project provides greater carbon sequestration potential than the baseline scenario. This suggests carbon costs and benefits of reducing fuels may need to be evaluated relative to how wildfire burn risk varies with fuel loading, forest type, and stand location.
Author:
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ISBN:
Category : Climatic changes
Languages : en
Pages : 183
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Over the past century in the western United States, warming has produced larger and more severe wildfires than previously recorded. General circulation models and their ensembles project continued increases in temperature and the proportion of precipitation falling as rain. Warmer and wetter conditions may change forest successional trajectories by modifying rates of vegetation establishment, competition, growth, reproduction, and mortality. Many questions remain regarding how these changes will occur across landscapes and how disturbances, such as wildfire, may interact with changes to climate and vegetation. Forest management is used to proactively modify forest structure and composition to improve fire resilience. Yet, research is needed to assess how to best utilize mechanical fuel reduction and prescribed fire at the landscape scale. Human communities also exist within these landscapes, and decisions regarding how to manage forests must carefully consider how management will affect such communities. In this work, three aspects of forest management are analyzed: (1) climate effects on forest composition and wildfire activity; (2) efficacy of fuel management strategies toward reducing wildfire spread and severity; and, (3) local resident perspectives on forest management. Using a forest landscape model, simulations of forest dynamics were used to investigate relationships among climate, wildfire, and topography with long-term changes in biomass for a fire-prone dry-conifer landscape in eastern Oregon. Under climate change, wildfire was more frequent, more expansive, and more severe, and ponderosa pine expanded its range into existing shrublands and high-elevation zones. There was a near-complete loss of native high-elevation tree species, such as Engelmann spruce and whitebark pine. Loss of these species were most strongly linked to burn frequency; this effect was greatest at high elevations and on steep slopes. Fuel reduction was effective at reducing wildfire spread and severity compared to unmanaged landscapes. Spatially optimizing mechanical removal of trees in areas at risk for high-severity wildfire was equally effective as distributing tree removal across the landscape. Tripling the annual area of prescribed burns was needed to affect landscape-level wildfire spread and severity, and distributing prescribed burns across the study area was more effective than concentrating fires in high-risk areas. I conclude that forest management can be used to reduce wildfire activity in dry-mixed conifer forests and that spatially optimizing mechanical treatments in high-risk areas can be a useful tool for reducing the cost and ecological impact associated with harvest operations. While reducing the severity and spread of wildfire may slow some long-term species shifts, high sub-alpine tree mortality occurred under all climate and fuel treatment scenarios. Thus, while forest management may prolong the existence of sub-alpine forests, shifts in temperature, precipitation, and wildfire may overtake management within this century. The use of PPGIS was useful for delineating the range of forest management preferences within the local community, for identifying areas of agreement among residents who have otherwise polarized views, and for generating modeling inputs that reflect views that may not be obtained through extant official channels for public participation. Because the local community has concerns about the use of prescribed fire, more education and outreach is needed. This may increase public acceptance of the amounts of prescribed fire needed to modify wildfire trajectories under future climate conditions.
Author: Jan W. van Wagtendonk
Publisher: Univ of California Press
ISBN: 0520961919
Category : Science
Languages : en
Pages : 567
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Fire in California’s Ecosystems describes fire in detail—both as an integral natural process in the California landscape and as a growing threat to urban and suburban developments in the state. Written by many of the foremost authorities on the subject, this comprehensive volume is an ideal authoritative reference tool and the foremost synthesis of knowledge on the science, ecology, and management of fire in California. Part One introduces the basics of fire ecology, including overviews of historical fires, vegetation, climate, weather, fire as a physical and ecological process, and fire regimes, and reviews the interactions between fire and the physical, plant, and animal components of the environment. Part Two explores the history and ecology of fire in each of California's nine bioregions. Part Three examines fire management in California during Native American and post-Euro-American settlement and also current issues related to fire policy such as fuel management, watershed management, air quality, invasive plant species, at-risk species, climate change, social dynamics, and the future of fire management. This edition includes critical scientific and management updates and four new chapters on fire weather, fire regimes, climate change, and social dynamics.
Author: Leda Nikola Kobziar
Publisher:
ISBN:
Category : Forest fires
Languages : en
Pages : 416
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"Throughout fire-adapted forests of the western US, and in the Sierra Nevada of California specifically, wildfire suppression has produced forest structures conducive to more severe, costly, and ecologically deleterious fires. Recent legislation has identified the necessity of management practices that manipulate forests towards less fire-hazardous structures. In the approximately 30 year old pine plantations of the Stanislaus National Forest, extensive fuels reduction procedures are being implemented. This dissertation addresses whether silvicultural and burning treatments are effective at reducing the intensity and severity of potential fire behavior, and how, along with wildfire, these treatments impact the evolution of carbon dioxide from the soil to the atmosphere. The first chapter addresses the relationships between soil respiration, tree injury, and forest floor characteristics in high and low severity wildfire burn sites in a salvage-logged mixed-conifer forest. The results indicate that fire severity influences soil CO2 efflux and should be considered in ecosystem carbon modeling. In the next chapter, fire models suggest that mechanical shredding of understory vegetation (mastication) is detrimental, and prescribed fire most effective in reducing potential fire behavior and severity in pine plantations. The third chapter documents the impact of alternative fuels treatments on soil carbon respiration patterns in the pine plantations, and shows that mastication produces short-term reductions in respiration rates and soil moisture. The final chapter further examines the relationships of fire-induced tree injuries, forest floor structure, and environmental factors to soil respiration response to fuels treatments. Each chapter is written as an independent manuscript; they collectively serve to expand the limited understanding of the effectiveness and ecological consequences of fire and fuels treatments in coniferous forests."--Abstract
Author: Brian Michael Levine
Publisher:
ISBN:
Category :
Languages : en
Pages : 184
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Author: Jens Turner Stevens
Publisher:
ISBN: 9781321213010
Category :
Languages : en
Pages :
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Montane coniferous forests in western North America are experiencing rapid environmental change, due in part to increasing fire severity and decreasing winter snowpack. Many of these forests experienced frequent low-severity fires prior to intensive logging and fire suppression during the nineteenth and twentieth centuries, which have led to increased fuel loads and increased dominance by fire-sensitive, shade-tolerant tree species. Forest managers seeking to mitigate increases in fire size and severity are increasingly implementing fuel-reduction treatments, which target small trees and surface fuels for removal. However, the ecological effects of these treatments on subsequent wildfire behavior, forest resilience, understory plant community dynamics, and plant invasions have not been well documented. In Chapter 1, I utilized a large-scale natural experiment to investigate the effects of recent fuel treatments on subsequent wildfire severity and structural resilience, in twelve different yellow pine and mixed-conifer forest sites in the mountains of eastern California. By quantifying forest structure in treated and adjacent untreated stands, both after wildfire and without wildfire, I demonstrated that treatments reduced the amount of structural change caused by wildfire, as a result of their moderating effect on fire severity. Two years post-wildfire, treated stands resembled pre-wildfire stands, in that they had greater tree litter cover, more tree seedling regeneration, less shrub cover and recruitment, and less bare soil relative to untreated stands, which generally burned at very high severity. In Chapter 2, I used the same network of twelve sites to test whether the gradient of disturbance severity, from untreated and unburned stands to high-severity wildfire stands, generated predictable patterns of understory plant community composition and diversity. I incorporated information on the evolutionary history of the native flora to show that increasing disturbance severity favored understory species with southern biogeographic affinity. Analysis of leaf functional traits indicated that increases in microclimatic water deficit in high-severity stands favored species with reduced specific leaf area relative to their leaf Nitrogen concentration. Native plant diversity at the stand scale was greatest in treated stands that subsequently burned in a wildfire, however this diversity peak was due to increased plot-scale alpha diversity relative to undisturbed stands, and increased between-plot beta diversity relative to high-severity wildfire stands. Conversely, exotic plant diversity peaked in high-severity wildfire stands that had not been previously treated. In Chapter 3, I investigated the population-level response of non-native species to interactions between forest harvesting strategies, prescribed fire, and winter snowpack depth using a transplant experiment with two non-native shrubs: Scotch broom (Cytisus scoparius L. (Link)) and Spanish broom (Spartium junceum L.). Both species had the strongest positive population growth responses to canopy thinning, rather than clearcuts or dense canopies. Despite positive effects of prescribed fire on seed germination, frequent prescribed fire was shown to decrease population growth rates for both species. However, experimental snowpack reductions led to increased winter survival by both species, which translated into strong positive effects on population growth rates. Under a future climate scenario where winter snowpack levels increase in elevation, middle-elevation forests that experience fuel treatments may therefore be at increased risk of invasion by non-native plants due to synergies between climate and management regimes.
Author: Lindsay Aney Chiono
Publisher:
ISBN:
Category :
Languages : en
Pages : 162
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Historic fire regimes in the dry conifer forests of the southern Cascade and northern Sierra Nevada regions of California were characterized by relatively frequent fires of low and mixed severity. Human management practices since the mid-19th century have altered the disturbance role of fire in these dry yellow pine and mixed conifer forest ecosystems. Fire suppression, high-grade timber harvesting, and livestock grazing have reduced the frequency of burning and caused a shift in the structure and species composition of forest vegetation. These changes, including high levels of accumulated fuel and increased structural homogeneity and dominance of shade-tolerant tree species, combined with a warming climate, have rendered many stands susceptible to high-severity fire. In many forests of the western United States, wildfires are increasingly difficult and costly to control, and human communities are regularly threatened during the fire season. Treating wildland fuels to reduce wildfire hazards has become a primary focus of contemporary forest management, particularly in the wildland-urban interface. The specific objectives of treatment are diverse, but in general, treatments address accumulated surface fuels, the fuel ladders that carry fire into the forest canopy, and surface and canopy fuel continuity. These modifications to forest fuels can alleviate the severity of a future wildfire and support suppression activities through improved access and reduced fire intensity. While fuel reduction treatments are increasingly common in western forests, the long-term structural and ecological effects of treatment remain poorly understood. This dissertation uses a chronosequence of treated stands to examine the temporal influence of treatment on forest structure, the understory plant community, and wildfire hazard. The first chapter examines the effects of fuels reduction treatment on stand structure, overstory species composition, and ground and surface fuels. The stand structures and reduced surface fuel loads created by fuels modification are temporary, yet few studies have assessed the lifespan of treatment effects. The structural legacies of treatment were still present in the oldest treatment sites. Treatments reduced site occupancy (stand density and basal area) and increased quadratic mean diameter by approximately 50%. The contribution of shade-tolerant true firs to stand density was also reduced by treatment. Other stand characteristics, particularly timelag fuel loads, seedling density, and shrub cover, exhibited substantial variability, and differences between treatment age classes and between treatment and control groups were not statistically significant. The second chapter evaluates fuel treatment longevity based on potential wildfire behavior and effects on vegetation. Forest managers must divide scarce resources between fuel treatment maintenance, which is necessary to retain low hazard conditions in treated stands, and the construction of new treatments. Yet the most basic questions concerning the lifespan of treatment effectiveness have rarely been engaged in the literature. In this study, field-gathered fuels and vegetation data were used to aid fuel model selection and to parameterize a fire behavior and effects model, Fuels Management Analyst Plus. In addition, a semi-qualitative, semi-quantitative protocol was applied to assess ladder fuel hazard in field sampling plots. Untreated sites exhibited fire behavior that would challenge wildfire suppression efforts, and projected overstory mortality was considerable. In contrast, estimated fire behavior and severity were low to moderate in even the oldest fuel treatments, those sampled 8-26 years after treatment implementation. Findings indicate that in the forest types characteristic of the northern Sierra Nevada and southern Cascades, treatments for wildfire hazard reduction retain their effectiveness for more than 10-15 years and possibly beyond a quarter century. Fuel treatment activities disturb the forest floor, increase resource availability, and may introduce non-native plant propagules to forest stands. Non-native plant invasions can have profound consequences for ecosystem structure and function. For these reasons, there is concern that treatment for fire hazard reduction may promote invasion by exotic species. Several short-term studies have shown small increases in non-native abundance as a result of treatment, but the long-term effects have rarely been addressed in the literature. The final chapter examines treatment effects on the understory plant community and on cover of the forest floor, as mineral soil exposure has been linked to invasion. Regression tree analysis provided insights into the influence of treatment and site characteristics on these variables. Treatments increased forb and graminoid cover, but temporal trends in abundance were opposite. An initial increase in forb cover in the most recently treated sites was followed by a gradual decline, while mean graminoid cover was highest in the oldest treatments. Shrubs dominated live plant abundance. Shrub cover showed few temporal trends, but was negatively associated with canopy cover. Mineral soil exposure was increased by treatment and declined slowly over time, remaining elevated in the oldest treatments. Non-native plant species were very rare in the treatment sites sampled in this study. Despite the availability of bare mineral soil and the proximity of transportation corridors, a source of non-native propagules, non-natives were recorded in only 2% of sampling plots. This study suggests that forest disturbance associated with treatment for hazardous fuels reduction may not produce significant invasions in these forest types.
Author: Shuang Liang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Sierra Nevada forests represent a major ecological and economic resource for the state of California. Changes in climate and disturbance regimes, compounded with changes in forest structure from fire-exclusion, pose a critical challenge to managing Sierran forests for sustained carbon (C) sequestration and ecosystem services. My dissertation research sought to improve our understanding of how changing climate and disturbance will affect forest ecosystems in the Sierra Nevada by accounting for species-specific dynamics and interacting spatial processes that were underrepresented in landscape projections. Given the diverse tree species and forest types that differ in their optimal climate for growth and tolerance of stressors, I simulated forest dynamics in the Sierra Nevada under projected future climate and area burned as well as alternative management strategies with a species-specific, spatially explicit forest landscape model. First, I quantified how projected climate-wildfire interactions would affect forest communities and associated C dynamics. Here, results suggest that, across the Sierra Nevada, forest communities may not change as intact unit over the 21st Century and potential exists for substantial community change and C sequestration decline beyond this century. Then, I assessed the long-term successional trajectory and the ability of the system to sequester C beyond the 21st Century. Assuming climate and wildfire distributions equilibrate at late-century conditions, the results show a committed decline in forest cover and C carrying capacity, suggesting a steep reduction in the contribution of Sierra Nevada forest to the terrestrial C sink. Finally, I quantified how large-scale restoration treatments would alter the effects of changing climate and wildfire on forest C balance. I found that widespread application of fuel treatments would confer greater forest C stock stability. This work offers an improved understanding of how changing environmental conditions will affect the forest ecosystems in the Sierra Nevada and provides insights into using large-scale management strategy to manage the Sierran landscape under novel conditions.
Author: DIANE Publishing Company
Publisher: DIANE Publishing
ISBN: 0788146793
Category :
Languages : en
Pages : 56
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Book Description
Managing wildland fire in the U.S. is a challenge increasing in complexity & magnitude. The goals & actions presented in this report encourage a proactive approach to wildland fire to reduce its threat. Five major topic areas on the subject are addressed: the role of wildland fire in resource management; the use of wildland fire; preparedness & suppression; wildland/urban interface protection; & coordinated program management. Also presented are the guiding principle that are fundamental to wildland fire management & recommendations for fire management policies. Photos, graphs, & references.
