Fire Science and Research
In the main forest belt of California, fires seldom or never sweep
from tree to tree in broad all-enveloping sheets .... Here the fires
creep from tree to tree, nibbling their way on the needle-strewn
ground.... -- John Muir, 1895
November 4, 2018
Severe fire weather and intensive forest management increase fire
severity in a multi-ownership landscape
Another recent paper also examined the role that intensive plantation forestry has on fire severity, and compared this to the relative importance of other variables known to drive fire severity (topography, weather, and fuels). The study area was the 19,000 ha Douglas Complex fire (2013) in Southwestern Oregon. Using a variety of metrics, including Landsat based estimates of fire severity (Relative differenced Normalized Burn Ratio, or RdNBR) and geospatial data on fire progression, weather, topography, pre-fire forest conditions, and land ownership, authors Harold Zald and Chrisopher Dunn were able to predict with statistical confidence that daily fire weather was the most important predictor of fire severity, but plantation stands on private industrial timberlands were more predictive of fire severity than topographic features.
This is important research because a frequent assertion made by proponents of intensive forest management is that intensively managed forests, characterized by densely planted, even-aged young trees, are less prone to high fire severity. This research paper discovered the opposite to be true.
The authors also found that intensive plantation forestry appears to have a greater impact on fire severity than decades of fire exclusion. Older forests on public, federal lands were found to have greater resilience to fire, despite long term fire exclusion.
The authors recommend further studies to answer additional compelling questions that arise from the study, such as how best to encourage forestry management that will decrease fire severity potential. Potentially, there may be issues of liability and responsibility relative to the continued expansion of plantation forestry adjacent to public forests, facilities, and other human infrastructures.
September 21, 2018
An important new review paper looks at the problems associated with reforestation in the dry interior forests of the west, in light of the current era of climate change and increased frequency and severity of fire. The paper is authored by research forest ecologist Malcolm North, with contributions by two dozen other researchers and Forest Service foresters, and is highly relevant for the Sierra Nevada.
The model for reforestation long practiced by the agency, dense and uniform plantings of "pines in lines," is increasingly recognized as unsustainable and inconsistent with the existing fire regime. Plantation trees are planted too closely, up to 300 trees per acre, and a large percentage of the plantations are never thinned, making them a significant part of the fuels problem in the West. The high cost of protecting these tree crop investments is becoming prohibitive today, as fires are increasing. The complete loss of plantations is a recurring scenario with every fire season, and has been the case for decades. It's time for a change.
The authors propose a new paradigm, "reforestation for resilience," pointing to the spatial heterogeneity of mature forests shaped by regular fire and resilient to its effects, as the appropriate model for long term plantation structure. But how to get there? Certainly not using the traditional planting methodology.
A blanket approach to replanting burned sites is no longer appropriate. New tools for identifying the acres that are appropriate for reforestation are described, and a planting spacing strategy utilizing the ICO model. Frequent-fire forests are characterized by three general components: Individual scattered trees in a matrix of shrubs and hardwoods; Clumps of trees; and Openings (ICO). The goal is a more diverse and fire resilient spatial pattern with a range of densities based on a finely tuned plan informed by a variety of biologic and geographic factors. Variation results from different inter-tree spacing within clusters, between clusters, and between clusters and individual tree seedlings.
The new model requires that forest managers also learn to apply prescribed burning early and regularly to planted sites, accepting some inevitable losses along with the multiple benefits. The authors acknowledge that first attempts should be viewed as experiments, but are necessary to gain sufficient knowledge of prescribed fire effects in young tree plantations.
The paper is the latest entry in the journal's Tamm Review series, named after forest ecologist Carl Olaf Tamm. The paper will be published in print in 2019, and we are delighted to be able to share this paper now. We are hopeful that the Forest Service in Region 5, and the California Department of Forestry and Fire Protection (CAL FIRE) will recognize the wisdom of adopting this new reforestation model and support widespread adoption of the recommendations therein.
May 4, 2017
One of the areas of research interest concerning fire effects from naturally occuring fire or prescribed fire is the effects on wildlife and native vegetation relative to the season of burning. Here are two research papers we found to be of importance to understanding plant responses to fire, both of which have an evolutionary context. In this 2007 paper, Eric Knapp, Dylan Schwilk, Jeffrey Kane, and Jon Keeley found that early-season burning did not cause long term significant impacts to plant diversity compared to late-season burning. In the presence of high fuel loading and intensely hot fires, late-season burning can result in delayed recovery of many plant species.
Knapp, E.E., Schwilk, D.W., Kane, J.M., and J.E. Keeley. 2007. Role of burning season on initial understory vegetation response to prescribed fire in a mixed conifer forest. Can. J. For. Res. 37:11-22.
In the second paper, Pausus and Keeley (2014) discuss the adaptive survival strategies of plants that evolved in fire-prone landscapes. The authors provide a "framework for understanding temporal and spatial variation in resprouting and seeding under crown-fire regimes." This paper is an important contribution to the literature concerning fire adapted plant species, and can be useful to understanding the role of fire on plant diversity.
For a summary of the ecology of prescribed fire, including impacts to wildlife, see:
April 21, 2017
Two recent research papers are especially relevant to our work to improve management of fire and forest practices. Download and read the papers in the links below.
In Hood et al (2015), the authors demonstrate that trees that have experienced low-severity fire have an increase in resin ducts. In the absence of low-intensity fire, such as currently exists due to a policy of mandatory fire suppression, resin duct production declines. Resin ducts help to discourage and repel bark beetle attacks. Bark beetles are currently at epidemic levels in the Sierra Nevada and throughout the western states, a condition that has been propelled by several years of drought and increasing temperature.
The second paper addresses the need to shift fire and fuels management policy to one that is relevant to the conditions that forests in the west are now facing due to warming climate. Forest managers have focused on fuel reduction through accelerated logging to achieve increased resilience and resistance to the effects of increasing wildfire. However, scientists have shown that this is not a successful strategy, due to the vast fire deficit and scope of overly dense forest fuels accumulation throughout national forests in the west. Schoennagel et al. (2017) argue that an adaptive resiience approach that aims to manage towards "future range of variability" rather than focusing on "historical range of variability" may be more protective and effective now. The authors also provide recommendations for the wildland-urban interface areas where community/societal actions can make a difference.
Schoennagel, T., Balch, J.K., Brenkert-Smith, H., Dennison, P.E., Harvey, B.J., Krawchuk, M.A., Mietkiewicz, N., Morgan, P., Mortiz, M.A., Rasker, R., Turner, M.G., and C. Whitlock. Adapt to more wildfire in western North American forests as climate changes. PNAS. Released for early edition. doi:10.1073/pnas. 16174641114.
Check in online at www.pnas.org.content/early/2017/04/11/1617464114 for related content.
September 17, 2015
A new paper published in Science today highlights the important role in the forest plan revision process for promoting implementation of the National Cohesive Wildlife Fire Management Strategy. Formal adoption of the NCWFMS in the forest plans would promote use of fire "to reduce fuels either intentionally (prescribed burning) or opportunistically (letting a natural ignition burn as 'managed wildfire') under moderate weather conditions. Although these burns are much less precise than mechanical thinning, in remote locations, fire is usually more efficient, cost-effective, and ecologically beneficial than mechanical treatments."
The authors discuss how entrenched attitudes and perverse monetary disincentives keep federal fire policy stagnating in the suppression/attack mode, instead of using fire to reduce fuels and restore fire and drought-resilient forests.
While fire suppression costs frequently "consume 50% of agency annual budgets," there is little funding left to conduct proactive fuels treatments.
Societal perceptions and expectations must also change, the authors caution.
"Engaged local stakeholders will need to look beyond short-term impacts of fire use (e.g., smoke, limited access, and risk of escape) to support managers working with fire and challenge suppression in remote forest zones."
North, MP., S.L. Stephens, B.M. Collins, J.K. Agee, G. Aplet, J.F. Franklin, and P.Z. Fule. 2015. Reform forest fire management - Agency incentives undermine policy effectiveness. Science 349(6254):1280-81 (625 KB PDF)
December 2011 -- New White Paper
Sierra Forest Legacy has been working closely with the Forest Service in the Sierra Nevada to understand why more fire is not being used for restoration type projects, and identifying areas where more collaboration between agencies and NGOs can help facilitate the use and acceptance of a more robust fire program in the Sierra Nevada. There is a backlog of acres needing to be burned across the Sierra Nevada and prescribed fire alone is not getting the job done. To research this issue in more detail, Sierra Forest Legacy has prepared a white paper "Ecological Burning in the Sierra Nevada: Actions to Achieve Restoration." The paper is intended for educational purposes and to aid in the development of necessary actions for land management agencies to move towards utilizing more fire to restore and promote resilient forest ecosystems.
Sierra Forest Legacy’s goal is to significantly increase the use and support of ecologically appropriate fire in the Sierra Nevada. We propose the following key actions to land management agencies in support of this goal:
- Collaboratively develop a large-scale pilot project to increase the use of managed fire in the Sierra Nevada;
- Manage fire on the landscape to produce low, moderate, and high severity fire effects within the historic range of variability;
- Utilize the Forest Service’s strategic management response policy in all fire events;
- Ensure adequate staffing year round to accomplish burns;
- Increase public awareness, education, and acceptance for the critical role fire plays in restoration efforts in the Sierra Nevada;
We hope you can take the time to review our white paper and provide us with any comments. Please direct your questions or comments to Karina Silvas-Bellanca at firstname.lastname@example.org.
2008 Fires -- Did Fuel Treatments Help?
American River Complex Fire
A study of fire severity effects in the region of the American River Complex Fire on the Tahoe National Forest was recently released by Forest Service Regional Ecologist Hugh Safford. The lightning ignited fire burned approximately 20,000 acres from June 21 through August 1, 2008. The study was undertaken to evaluate the effectiveness of previous stand treatments designed to reduce fire severity. The report confirmed the great importance of treating surface fuels with prescribed fire in order to reduce future fire severity and spread. Thinning alone was not sufficient to prevent high levels of mortality and fire spread. Stands which had been mechanically thinned, and then treated with prescribed fire to reduce the surface fuels, were significantly more resistant to severe fire effects. The report confirms earlier research conducted by Scott Stephens and Jason Moghaddas (2005) at Blodgett State Forest which predicted these very outcomes.Grapple piles, or piles of logging slash that are supposed to be burned after logging but which frequently are left unburned, also contributed to high stand mortality. The report provides additional confirmation that fuels treatments must be considered a part of every timber harvest removal, regardless of the scale or objective. These treatments must be conducted before any forest project is considered complete.
In some instances, the use of mechanical thinning alone increased fire mortality.
In addition, plantations which contained live, dense green shrubs resisted fire significantly better than plantations that had been mechanically masticated. Safford notes, "In a number of cases, the persistence of dry surface fuels in the masticated units appears to have abetted rather than resisted fire." Such surface fuels can persist in the Sierra Nevada's dry forests for decades.
The report confirms basic Sierra Nevada forest ecology principles that Sierra Forest Legacy and our partners in the conservation community have long sought to bring to national forest planning and policy making. Fire is a critical ecological driver in middle elevation Sierra Nevada forests and it has shaped these forests' structure and resilience, and species composition, for millenia. In this century, it is imperative that we move ahead with enlightened forest management policies that incorporate fundamental scientific principles at every juncture.
Fire Ecology and the Sierra Nevada
Fire is an integral, important, and inevitable part of the Sierra Nevada ecosystem. The plants and animals throughout the Sierra have developed not just to withstand fire, but in fact, many plants and animals depend on fire for their existence. The seeds of Giant Sequoia (Sequoiadendron giganteum), for instance, need fire to germinate properly. Several other tree species need the heat of fire to open up their tightly serotinous cones thus exposing the next seed crop that will grow within the soil and become the next generation of ancient trees. Native Americans used fire as part of their food gathering and hunting cycle. Over 100 years of logging old growth trees, as well as intense fire suppression policies have caused an unnatural accumulation of fuels that now threaten communities and the overall health and stability of the magnificent Sierra Nevada.
Fire ecology is a branch of ecology that concentrates on the origins, cycles, and future stages of wildland fire. It probes the relationship of fire with living organisms and their environment. Four concepts provide the basis for fire ecology:
Fire Dependence: This concept applies to species of plants that rely on the effects of fire to make the environment more hospitable for their regeneration and growth.
Fire History: This concept describes how often fires occur in a geographical area. Fire scars, or a layer of charcoal remaining on a living tree as it adds a layer of cells annually, provide a record that can be used to determine when in history a fire occurred.
Fire Regime: Fire regime is a generalized way of integrating various fire characteristics, such as the fire intensity, severity, frequency, and vegetative community.
Fire Adaptation: This concept applies to species of plants that have evolved with special traits contributing to successful abilities to survive fires at various stages in their life cycles. For example, serotinous cones, fire resistant bark, fire resistant foliage, or rapid growth and development enable various kinds of plants to survive and thrive in a fire prone environment.
The Role of Fire
From the time that forests and lightning came into existence, fire has played an essential role. As one National Park resource professional stated, “Fire is as natural to this ecosystem as sunlight and snow.” Fire creates plant and animal habitat throughout the United States. There is no question that many ecosystems would not exist in the absence of fire.
Now, after decades of fire suppression and other past management practices, the importance of reintroduction of fire to wildland ecosystems is widely accepted as essential practice. Two major events have been instrumental in turning policy and decision making around. One, scientists have observed that the recovery of forest plants and wildlife habitat since the 1980 eruption of Mount St. Helens in Oregon--now a natural laboratory for studying disturbance in western forest ecosystems--clearly demonstrates the ability of ecosystems to recover, even from devastating catastrophic disturbance. Secondly, the 1988 fires in Yellowstone National Park, where nearly 800,000 acres burned for several months and eventually were extinguished by fall rains, resulted in a robust increase in quality habitat for wildlife, and restored plant communities long suppressed by fire suppression policy. These seminal events, coupled with a growing increase in scientific research in the field of fire ecology, have informed agency decision making. This resulted in adoption in 1995 by Federal agencies of a new Federal Wildland Fire Management Policy. The policy contains direction to control the fires we do not want, while promoting those we do. However, it is also essential to understand that logging after fire--called "salvage logging"--is highly detrimental to the natural recovery processes in the post-fire environment and can reverse natural recovery processes and eliminate the benefits of fire. Read more about salvage logging here.
Few alternative treatments can compete with fire effectiveness to reduce unnatural fuel buildups, restore native plant communities, and improve fire resiliency, and fire is less costly than other types of treatments. It is also most effective at reducing long-term smoke impacts to surrounding communities. Chemicals have many environmental risks associated with their use and are expensive. Mechanical treatments have similar problems and if not conducted properly can increase fire hazards. Prescribed fire is much more affordable with much less risk to the habitat and destruction of site and soil quality.
What is Fire?
Fire is the combination of heat, oxygen, fuel and an ignition source. Fuels include grasses, needles, leaves, brush and trees. Natural ignition sources in the Sierra Nevada generally involve lightning. Fire management officials are increasingly using fire to improve forest health and to protect communities. However, sometimes people also start uncontrolled fires through carelessness or arson.
Where and how quickly a fire moves depends on the terrain, weather and types of fuel. Fires burn faster up hillsides than they do on flat ground. The heat rising from the flames pre-heats the grasses, shrubs or trees on upslope. Like sheets of paper, grasses burn quickly, up to several miles per hour under extreme conditions. Larger fuels, such as logs, may take hours or even days to burn completely. While windswept flames can leap into the crowns of trees and burn entire trees in seconds, many fires merely creep along the ground slowly burning brush and forest litter.
The diversity of plants and animals we enjoy in the forests and national parks depend upon fire. What may look at first like devastation soon becomes a panorama of new life. Fire starts critical natural processes by breaking down organic matter into soil nutrients. Soil, rejuvenated with nitrogen from ash, provides a fertile seedbed for plants. With less competition and more sunlight certain seedlings grow quickly.
About Wildland Fire
Wildland fire has great potential to change landscapes more often than volcanoes, earthquakes or even floods. Such forces of change are completely natural. Many plants and animals cannot survive without the cycles of fire or flooding to which they are adapted. If all fire is suppressed, fuel builds up and makes bigger fires inevitable. Under certain conditions, large, hot fires can threaten public safety, devastate property, damage natural and cultural resources, and be expensive and dangerous to fight.
Forest policy stresses managing fire, not simply suppressing it. This means planning for the inevitable and promoting the use of fire as a land management tool. The goal is to restore fire's role as a dynamic and necessary natural process.
Prescribed fire is one of the most important tools used to manage fire today. A scientific prescription for the fire, prepared in advance, describes its objectives, fuels, size and the ideal environmental conditions for it to burn. If it moves outside the predetermined area, the fire may be suppressed. Burning key areas in advance, thereby removing fuels from the path of future unwanted fires, can protect communities and make the forest more fire resistant.
Good Fire / Prescribed Fire
Not all fire is bad. In fact, the exclusion of naturally occurring, low intensity fire, over the last century has contributed significantly to the increased build up of surface fuels (needles, limbs, cones, brush) and increased wildfire intensity in recent decades.
On public lands, prescribed fires are used to manage vegetation instead of lightning-caused fires. Prescribed burns are ignited to reduce hazardous fuels (needles, brush, downed woody material, etc.) so that future fires do not become large, uncontrolled events that devastate the forest and threaten air quality for extended periods.
Fire management may also choose to closely monitor naturally started fires, ignited by lightning, to meet specific resource objectives like the prescribed fires. This type of fire management is called Wildland Fire Use. In the National Parks of California many lightning-caused fires have are allowed to burn and die naturally each year regenerating the forest and reducing future risks.
"Prescribed" burning is defined in A Guide for Prescribed Fire in Southern Forests as: “fire applied in a knowledgeable manner to forest fuels on a specific land area under selected weather conditions to accomplish predetermined, well-defined management objectives.” Wildland Fire Use is also considered a “prescribed” fire even though they are naturally caused (generally by lightning).
The question is, how can we better manage wildland fire so that people and communities are safe, while ecosystems are allowed to benefit from the annual seasons of flame? Most importantly, the only way fire will ever be successfully reintroduced is for the rural communities on the front lines to feel safe. Federal fire scientists have determined that it is the home and its immediate surroundings that principally determine the potential for home ignition during fires. Even so, communities will only feel safe when the land surrounding them--the community protection zone--is treated to reduce hazardous fuels through strategic thinning, brush removal, and prescribed burning.
Fire scientists have determined that mechanical thinning without prescribed fire (including fuel breaks) does not effectively reduce fire behavior under extreme conditions (Stephens 1998). They have also concluded that thinning or other mechanical treatments alone will not restore forest ecosystems (Conservation Biology, Vol. 18, no. 4, August 2004) and that prescribed fire is the most effective tool at reducing the surface fuels that contribute to surface fire spread (van Wagtendonk in SNEP 1996). The reintroduction of fire into the Sierra Nevada landscape is critical to solving the fire hazard that currently exists.
Few alternative treatments can compete with fire from the standpoint of effectiveness, cost, and reducing long-term smoke impacts to surrounding communities. Chemicals are expensive and have associated environmental risks. Mechanical treatments have the same problems. Prescribed fire is much more affordable with much less risk to the habitat and destruction of site and soil quality.
The Sierra Nevada Framework uses prescribed fire as a key management tool in reducing surface fuels and ladder fuels (brush and small trees) to protect communities and to make the forest more resilient and healthy.
Additional information about prescribed fire from the standpoint of smoke management, and our efforts to promote acceptance of short term air quality impacts from beneficial fire used to restore fire resiliency in the forests of the Sierra Nevada, can be found in the Managing Fire section of our website.
And Sometimes...Bad Fire
In recent years, fires in the Sierra Nevada have been breathlessly reported as being "catastrophic" with the entire forest being "destroyed" or burned up. On the nightly news, it is the catastrophic areas of fire that are shown because they are dramatic visual images. Unfortunately, this portrayal distorts the overall picture. On the ground, a far different picture emerges.
Within the "fire perimeter"--the farthest outside edge of the forest affected by the fire and whatever suppression efforts are being conducted--there are usually some areas that have burned so hot that all vegetation is destroyed. These are the "catastrophic" or severe areas, but within the fire perimeter are larger areas of "moderate severity," "low severity," and even areas that have not burned at all.
Fire severity and vegetation type are two variables that determine the impact a wildfire will have on the forest. Contrary to the conventional wisdom, many wildfires in the last decade in the Sierra have been primarily low-moderate in nature and are the kinds of fire we actually pay people to conduct as "fuels treatments" for forest health and fire risk reduction.
Even areas of "high severity" provide important ecological functions. The black-backed woodpecker is just one species that needs burned over areas to forage and nest successfully. In northeast Washington, black-backed woodpeckers were 20 times more abundant in burned versus unburned forests (Kreisel and Stein 1999), and often were restricted to standing dead forests created by recent stand-replacement fires (Hutto 1995, Caton 1996). More information about the increasingly threatened black-backed woodpecker can be found here. The importance of leaving sufficient acreage of burnt forests un-logged after fire cannot be underestimated - for the maintenance of this and numerous other species of plants and wildlife. So-called "salvage" logging after fire is extremely detrimental to natural forest composition and processes. Read more about the science of salvage logging impacts here.
It is also true that the fire season has expanded in California due to a number of variables including climate change. Uncharacteristic fire effects are those that negate the beneficial effects of fire and eliminate wildlife habitat that is already in short supply. These adverse impacts are made worse due to the build up of small trees that have grown during a century and a half of intensive logging and high-technology fire suppression. While Sierra Forest Legacy and our partners support the use of appropriately-scaled thinning and prescribed fire to restore fire-adapted and resilient forest structure in the Sierra, others argue that forests should not be thinned at all, and that fire can take its course without long term adverse effects (for example, 'The Myth of Catastrophic Wildfire'). This argument is based on the premise that current fire frequency and intensity are not out of sync with historical levels of burning. Sierra Forest Legacy does not agree with this perspective and we have articulated our reasons for disagreement in Susan Britting's review of Hanson.
Inappropriately Scaled Logging Increases Fire Risk to the Forest
The Sierra Nevada Ecosystem Project Report (SNEP) in 1996 stated, “Timber harvest, through its effects on forest structure, local microclimate, and fuels accumulation, has increased fire severity more than any other recent human activity.” The August 2000 Congressional Research Service report concluded, "Timber harvesting removes the relatively large diameter wood that can be converted into wood products, but leaves behind the small material, especially twigs and needles. The concentration of these ‘fine fuels’ on the forest floor increases the rate of spread of wildfires."
A 1999 General Accounting Office Report (GAO/RCED-99-65) chastised the Forest Service for operating a fuels reduction program that focused on harvesting large, commercially valuable, fire-resistant trees, rather than concentrating on high fuel hazard areas on our national forests. The revisions to the Framework plan propose a return to the failed strategies of the past by downplaying the use of prescribed fire, while tripling the logging on Sierra Nevada forests, mostly in the larger size classes. Fire scientists have suggested that the largest portion (over 80%) of the fire hazard on our forests is in the surface and ladder fuels, rather than the overstory trees.
The issues surrounding fire and appropriate levels of thinning will continue to be controversial. Sierra Forest Legacy is committed to finding the solutions to the ecological problems that have resulted from a long history of intensive logging coupled with well-intentioned, but in the end, detrimental fire suppression policies. There will be few easy answers, and they will rarely be black and white, especially since climate change and carbon accounting are now factors that must also inform decision making. Stay tuned.
Glossary of Wildland Fire Related Terms
Plant Succession: In ecology, progressive change of the plant and animal life of an area in response to environmental conditions.
Forest Stand Density: The amount of trees in a forest per unit area. Can be measured in terms of basal area and crown cover.
Growth or Vigor: The ability of plants to exhibit healthy natural growth and survival.
Stand: A group of trees with similar species composition, age, and condition that makes the group distinguishable from other trees in the area.
Silvicultural: The practice of caring for forest trees in a way that meets management objectives. For example, foresters may control the composition and quality of a forest stand for goods such as timber and/or benefits to an ecosystem.
Prescribed Fire: A forest management practice that uses fire to improve habitat or reduce hazardous fuels. A plan for the prescribed burn must be written out and approved, and specific requirements must be met.
Fire-Resilient Landscape: A natural landscape featuring plants that have adapted to local wildlife conditions, or a domestic outdoor space where appropriate actions have been taken to make it less vulnerable to wildfire and certainly less prone to causing one.
Modify Fire Behavior: Using fire-safe practices such as fuel treatments, thinning, creating firebreaks, etc., to change the way a fire will behave, with a goal of slowing it down and/or suppressing it more easily.
Crown Fire: A fire that spreads from treetop to treetop, and is characteristic of hot fires and dry conditions. Crown fires are generally more complex to control than fires on the surface.
Surface Fuels: Materials on the ground like needles or low-growing shrubs that provide the fuel for fires to spread on the ground. Surface fuels are generally considered all fuels within six feet of the ground.
Ladder Fuels: Materials such as shrubs or small trees connecting the ground to the tree canopy or uppermost vegetation layer. In forests, this allows fire to climb upward into trees.
Crown Density: A measurement of the thickness or density of the foliage of the tree crown in a stand.
Biodiversity: The abundant variety of plant, fungi, and animal species found in an ecosystem, including the diversity of genetics, species, and ecological type.
Site-Specific: Applicable to a specific piece of land and its associated attributes and conditions (e.g. microclimate, soils, vegetation).
Soil Types: Refers to the different combinations of soil particles and soil composition. Soil can vary greatly within short distances.
Forest Stand Enhancement: A combination of both silvicultural thinning practices and other forest restoration activities such as prescribed fire, which aim to increase the health, resiliency, and vigor of tree communities within a forest ecosystem.
Fuel Continuity: The amount of continuous fuel materials in a fire’s path that allows the fire to extend vertically toward the crowns of trees or horizontally into the forest or other fuels.
Fire Science Research Papers
Please note that many of the papers provided here may be categorized in one or more of the categories of fire ecology, fuels management, prescribed fire, and/or post-fire effects.
Collins, B., R. Everett, and S. Stephens. 2011. Impacts of fire exclusion and recent managed fire on forest structure in old growth Sierra Nevada mixed-conifer forests. Ecosphere 2(4) Article 5, 1-14.(1.6MB PDF)
Collins, B.M. and S.L. Stephens. 2010. Stand-replacing patches within a ‘mixed severity’ fire
regime: quantitative characterization using recent fires in a long-established natural fire area. Landscape Ecol 25:927–939. (565 KB PDF)
Collins, Brandon M., Lydersen, Jamie M., Everett, Richard G., and Scott L. Stephens. 2018. How does forest recovery following moderate-severity fire influence effects of subsequent wildfire in mixed-conifer forests? Fire Ecology 14:3, https://doi.org/10.1186/s42408-018-0004-x. (2.4 MB PDF)
Cruz, M.G., M.E. Alexander, and R.H. Wakimoto. 2003. Assessing Canopy Fuel Stratum Characteristics in Crown Fire Prone Fuel Types of Western North America. International ournal of Wildland Fire, 12, 39-50 (195KB PDF).
Dombeck, M. P., J. E. Williams, and C. A. Wood. 2004. Wildfire policy and public lands: integrating scientific understanding with social concerns across landscapes. Conservation Biology 18, 883-889 (218KB PDF).
Fiedler, C.E., et.al. 2004. A Strategic Assessment of Crown Fire Hazard in Montana: Potential Effectiveness and Costs of Hazard Reduction Treatments. U.S. Forest Service, Gen. Tech. Rep. PNW-GTR-622 (1.10MB PDF).
Graves, D.A., and L.F. Neuenschwander. 2003. Crown Fire Assessment in the Urban Intermix: Modeling the Spokane, Washington Ponderosa Pine Forests . U.S. Forest Service, Joint Fire Science Conference and Workshop (179KB PDF).
Hessberg, P.F., J.K. Agee, and J.F. Franklin. 2005. Dry Forests and Wildland Fires of the Inland Northwest USA: Contrasting the Landscape Ecology of the Pre-Settlement and Modern Eras. Forest Ecology and Management, 2005 (1.65MB PDF).
Koontz, M.J., North, M.P., Werner, C.M., Fick, S.E., and A.M. Latimer. 2020. Local forest structure variability increases resilience to wildfire in dry western U.S. coniferous forest. Ecology Letters doi: 10.1111/ele.13447. (1.14 MB PDF).
McKelvey, C.N., et.al. 1996. An Overview of Fire in the Sierra Nevada. Sierra Nevada Ecosystem Project: Final report to Congress, vol. II, Assessments and scientific basis for management options, University of California, Davis, Centers for Water and Wildland Resources, 1996 (56KB PDF).
Martin, R.E., and D.B. Sapsis. 1991. Fires and Agents of Biodiversity: Pyrodiversity Promotes Biodiversity. Proceedings of the Symposium on Biodiversity of Northwestern California, October 28-30, 1991, Santa Rosa, California (2.55MB PDF).
Minnich, R.A., M.G. Barbour, J.H. Burk, J. Sosa-Ramírez. 2000. Californian mixed-conifer forests under unmanaged fire regimes in the Sierra San Pedro Mártir, Baja California, Mexico. J. of Biogeography 27: 105-129 (1.19MB PDF).
Noss, R.F., Franklin, J.F., Baker, W.L., Schoenanagel, T., and Moyle, P.B. 2006. Ecology and Management of Fire-prone Forests of the Western United States. Society for Conservation Biology Scientific Panel on Fire in Western U.S. Forests. North American Section SCB. Arlington, Virginia.
Scott, J.H., and E.D. Reinhardt. 2001. Assessing Crown Fire Potential by Linking Models of Surface and Crown Fire Behavior. U.S. Forest Service, Rocky Mtn. Research Station, Research Paper RMRS-RP-29 (482KB PDF).
Van Mantgem, P., and M. Schwartz. 2003. Bark Heat Resistance of Small Trees in Californian Mixed Conifer Forests: Testing Some Model Assumptions. Forest Ecology and Management 178, 341–352 (236KB PDF).
Wilson, J.S., and P.J. Baker. 1998. Mitigating Fire risk to Late-successional Forest Reserves on the East Slope of the Washington Cascade Range, USA. Forest Ecology and Management 110, 59-75 (816KB PDF).
Bekker, M.F. and A.H. Taylor. 2010. Fire disturbance, forest structure, and stand dynamics in montane forests of the southern Cascades, Thousand Lakes Wilderness, California, U.S.A. Ecoscience 17(1):59-72 (1.20 MB PDF).
Brown, P.M., M.R. Kaufmann, and W.D. Sheppard. 1999. Long-term, Landscape Patterns of Past Fire Events in a Montane Ponderosa Pine Forest of Central Colorado. Landscape Ecology 14, 513–532 (408KB PDF).
Hessburg, P.F., J.K. Agee, and J.F. Franklin. 2005. Dry Forests and Wildland Fires of the Inland Northwest USA: Contrasting the Landscape Ecology of the Pre-settlement and Modern Eras. Forest Ecology and Management, 2005 (1.66 MB PDF).
Mallek, C., H. Safford, J. Viers, and J. Miller. 2013. Modern departures in fire severity and area vary by forest type, Sierra Nevada and southern Cascades, California, USA. Ecosphere 4(12):153. http://dx.doi.org/10.1890/ES13-00217 (4.94 MB PDF).
Miller, J. D., H. D. Safford, M. A. Crimmins, and A. E. Thode. 2009. Quantitative evidence for increasing forest fire severity in the Sierra Nevada and southern Cascade Mountains, California and Nevada, USA. Ecosystems 12:16–32 (580 KB PDF.)
Miller, J.D., C.N. Skinner, H.D. Safford, E.E. Knapp, and C.M. Ramirez. 2012. Trends and causes of severity, size, and number of fires in northwestern California, USA. Ecological Applications, 22(1), 184–203 (627 KB PDF).
Steel, Z. L., H. D. Safford, and J. H. Viers. 2015. The fire frequency-severity relationship and the legacy of fire suppression in California forests. Ecosphere 6(1):8. http://dx.doi.org/10.1890/ES14-00224.1(5 MB PDF).
Stephens, S.L., C.N. Skinner, and S.J. Gill, 2003. Dendrochronology-Based Fire History of Jeffrey pine – mixed conifer Forests in the Sierra San Pedro Martir, Mexico. Can. J. For. Res. 33, 1090–1101 (387KB PDF).
Stephens, S.L., R.E. Martin, and N.E. Clinton. 2007. Prehistoric Fire Area and Emissions from California’s Forests, Woodlands, Shrublands, and Grasslands. Forest Ecology and Management, 2007 (363KB PDF).
Taylor, A.H., Trouet, V., Skinner, C., and S. Stephens. 2016. Socioecological transitions trigger fire regime shifts and modulate fire–climate interactions in the Sierra Nevada, USA, 1600–2015 CE. PNAS. 113(48):13684-13689.
Arbaugh, M.J., J. Merzenich, J.W. van Wagtendonk. 1999. A Test of the Strategic Fuels Management Model VDDT Using Historical Data from Yosemite National Park. U.S. Forest Service, Joint Fire Science Conference and Workshop (91KB PDF).
Bigelow, S.W. and M. P. North. 2012. Microclimate effects of fuels-reduction and group-selection silviculture: implications for fire behavior in Sierran mixed-conifer forests. Forest Ecology and Management 264: 51-59. (1.22 MB PDF).
Carey, H., and M. Schumann. 2003. Modifying WildFire Behavior – The Effectiveness of Fuel Treatments: The Status of Our Knowledge. National Community Forestry Center Southwest Region Working Paper (730KB PDF).
Churchill, D.J., A.J. Larson, M.C. Dahlgreen, J.F. Franklin, P.F. Hessburg, and J.A. Lutz. 2013. Restoring forest resilience: from reference spatial patterns to silvicultural prescriptions and monitoring. Forest Ecology and Management 291: 442-457.
Churchill, D.J., A.J. Larson, S.M.A. Jeronimo M.C. Dalhgreen, and J.F. Franklin. 2013. The ICO [Individual, Clumps, and Openings] approach to quantifying and restoring forest spatial pattern: Implementation guide. Version 2.0. Stewardship Forestry, Vashon, Washington, USA (3 MB PDF)
Churchill, D.J., A.J. Larson, M.C. Dahlgreen, J.F. Franklin, P.F. Hessburg, and J.A. Lutz. 2013. Restoring forest resilience: From reference spatial patterns to silvicultural prescriptions and monitoring. Forest Ecology and Management 291(442-457) (1.03 MB PDF)
Cohen, J.D. 2000. What is the Wildland Fire Threat to Homes? U.S. Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Missoula, MT, Presented at Northern Arizona University, School of Forestry, Thompson Memorial Lecture Series (361KB PDF)
Collins, B.M., S.L. Stephens, G.B. Roller, and J.J. Battles. 2011. Simulating fire and forest dynamics for a landscape fuel treatment project in the Sierra Nevada. Forest Science 57:77-88 (1.3 MB PDF)
Collins, Brandon M., Lydersen, Jamie M., Everett, Richard G., and Scott L. Stephens. 2018. How does forest recovery following moderate-severity fire influence effects of subsequent wildfire in mixed-conifer forests? Fire Ecology 14:3, https://doi.org/10.1186/s42408-018-0004-x.
Crookston, N.L., W.A. Kurz, and E.D. Reinhardt. 1999. Relationships Between Models Used to Analyze Fire and Fuel Management Alternatives. U.S. Forest Service, Joint Fire Science Conference and Workshop (35KB PDF).
Fontaine, J.B. and P.L. Kennedy. 2012. Meta-analysis of avian and small-mammal response to fire severity and fire surrogate treatments in U.S. fire-prone forests. Ecological Applications, 22(5), 2012, pages 1547–1561 (2.40 MB).
Gonzáles-Cában, A. et al. 2017. Do fuel treatment costs affect wildfire suppression costs and property damages? An analysis of costs, damages avoided, and return on investment. Final Report Joint Fire Science Project ID: 14-5-01-12. (424 KB PDF)
Graham, R.T., S. McCaffrey, and T.B. Jain. 2004. Science Basis for Changing Forest Structure to Modify Wildfire Behavior and Severity. U.S. Forest Service, Rocky Mtn. Research Station Gen. Tech. Rep. RMRS-GTR-120 (2.79MB PDF).
Graham, R.T., et.al. 1999. The Effects of Thinning and Similar Stand Treatments on Fire Behavior in Western Forests. U.S. Forest Service, Pacific Northwest Research Station Gen. Tech. Rep. PNW-GTR-463 (338KB PDF).
Kobziar, L.N., J.R. McBride, and S.L. Stephens. 2009. The efficacy of fire and fuels reduction treatments in a Sierra Nevada pine plantation. International Journal of Wildland Fire 18:791-801 (247 KB PDF).
McGinnis, T.W., J.E. Keeley, S.L. Stephens, and G.B. Roller. 2010. Fuel buildup and potential fire behavior after stand-replacing fires, logging fire-killed trees and herbicide shrub removal in Sierra Nevada forests. Forest Ecol. Mgmt. 260(2010):22-35. (1.34 MB PDF)
Nitschke, C.R. 2005. Does Forest Harvesting Emulate Fire Disturbance? A Comparison of Effects on Selected Attributes in Coniferous-dominated Headwater Systems. Forest Ecology and Management 214, 305–319 (244KB PDF).
North, M., P. Stine, K.L. O'Hara, W.J. Zielinski, Sl.L. Stephens SL. 2009. An Ecosystem Management Strategy for Sierran Mixed-Conifer Forests. USDA Forest Service: Pacific Southwest Research Station. General Technical Report PSW-GTR-220.
North, M., A. Brough, J. Long, B. Collins, P. Bowden, D. Yasuda, J. Miller, and N. Sugihara. 2015. Constraints on mechanized treatment significantly limit mechanical fuels reduction extent in the Sierra Nevada. J. Forestry 113(1):40-48 (779 KB PDF).
North, MP., S.L. Stephens, B.M. Collins, J.K. Agee, G. Aplet, J.F. Franklin, and P.Z. Fule. 2015. Reform forest fire management - Agency incentives undermine policy effectiveness. Science 349(6254):1280-81 (625 KB PDF)
O’Laughlin, J. 2005. Conceptual Model for Comparative Ecological Risk Assessment of Wildfire Effects on Fish, With and Without Hazardous Fuel Treatment. Forest Ecology and Management, 2005 (301KB PDF).
Raymond, C.L. 2004. The Effects of Fuel Treatments on Fire Severity in a Mixed-Evergreen Forest of Southwestern Oregon. Master’s Thesis, University of Washington, College of Forest Resources, Seattle, Washington, 72 p. (1.14KB PDF).
Reinhardt, E.D., R.E. Keane, D.E. Calkin, and J.D. Cohen. 2008. Objectives and considerations for wildland fuel treatment in forested ecosystems of the interior western United States. Forest Ecology and Management 256:1997-2006. (191 KB PDF)
Stephens, S. L. 1998. Evaluation of the Effects of Silvicultural and Fuels Treatments on Potential Fire Behavior in Sierra Nevada Mixed-conifer Forests. Forest Ecology and Management 105, 21-35 (547KB PDF).
Stephens, S. L., and J.J. Moghaddas. 2005. Experimental Fuel Treatment Impacts on Forest Structure, Potential Fire Behavior, and Predicted Tree Mortality in a California Mixed Conifer Forest. Forest Ecology And Management 215, 21–36 (199KB PDF).Stephens, S.L. and J.J. Moghaddas. 2005. Silvicultural and reserve impacts on potential fire behavior and forest conservation: 25 years of experience from Sierra Nevada mixed conifer forests. Biological Conservation 25:369-379 (128 KB PDF).
Thompson, J.R., T.A. Spies, and L.M. Ganio. 2007. Reburn Severity in Managed and Unmanaged Vegetation in a Large Wildfire. Proceedings of the National Academy of Sciences, 104(25) 10743–10748 (1.08MB PDF).
Meyer, M.D.; Long, J.W.; Safford, H.D., eds. 2021. Postfire restoration framework for national forests in California. Gen. Tech. Rep. PSW-GTR-270. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 204 p. (22.6 MB PDF, link is offsite).
Ritchie, M.W., E.E. Knapp, and C.N. Skinner. 2013. Snag longevity and surface fuel accumulation following post-fire logging in a ponderosa pine dominated forest. Forest Ecology and Management 287 (2013) 113–122. (864 KB PDF)
van Wagtendonk, J.W., K.A. van Wagendonk, and A.E. Thode. 2012. Factors associated with the severity of intersecting fires in Yosemite National Park, California, USA. Fire Ecology 8(1):11-31. (1.63 MB PDF)
Knapp, E.E., et.al. 2005. Fuel Reduction and Coarse Woody Debris Dynamics with Early Season and Late Season prescribed Fire in a Sierra Nevada Mixed Conifer Forest. Forest Ecology and Management 208, 383–397 (395KB PDF).
Keifer, M., N.L. Stephenson, and J. Manley. 2000. Prescribed Fire as the Minimum Tool for Wilderness Forest and Fire Regime Restoration: A Case Study from the Sierra Nevada, CA. Proceedings: Wilderness Science in a Time of Chance. Proc. RMRSP- 000. Ogden, UT, U.S. Forest Service, Rocky Mountain Research Station (35KB PDF).
Mutch, L.S., and D.J. Parsons. 1998. Mixed Conifer Forest Mortality and Establishment Before and After Prescribed Fire in Sequoia National Park, California. Forest Science, 44 (2) 341-355 (191KB PDF).
North, MP., S.L. Stephens, B.M. Collins, J.K. Agee, G. Aplet, J.F. Franklin, and P.Z. Fule. 2015. Reform forest fire management - Agency incentives undermine policy effectiveness. 349(6254):1280-81 (625 KB PDF)
Opperman, T., M. Keifer, and L. Trader. 2001. Meeting Resource Management Objectives with Prescribed Fire. Proceedings of the 11th Conference on Research and Resource Management in Parks and on Public Lands, The George Wright Society, 2001 (1.14MB PDF).
Pollet, J., and P.N. Omi. 1999. Effect of Thinning and Prescribed Burning on Wildfire Severity in Ponderosa Pine Forests. The Joint Fire Science Conference and Workshop, U.S. Forest Service, 1999 (26KB PDF).
Ryan, K.C., Knapp, E.E., and J. Morgan. 2013. Prescribed fire in North American forests and woodlands: history, current practice, and challenges. Frontiers in Ecology and the Environment 11: e15–e24. (1.3 MB PDF)
Stephens, S.L., and M.A. Finney. 2002. Prescribed Fire Mortality of Sierra Nevada Mixed Conifer Tree Species: Effects of Crown Damage and Forest Floor Combustion. Forest Ecology and Management 162, 261–271 (147KB PDF).