Article

The Ecological Role of Fire in Sierran Conifer Forests: Its Application to National Park Management

October 1973
Quaternary Research 3(3):496-513

October 1973
3(3):496-513

Authors:

The impact of fire on the environment of the various Sierran conifer forests varies with intensity and frequency. Generally, however, fire (1) prepares a seedbed; (2) cycles nutrients within the system; (3) adjusts the successional pattern; (4) modifies conditions affecting wildlife; (5) influences the mosaic of age classes and vegetation types; (6) alters the numbers of trees susceptible to disease and insects; and (7) both reduces and creates fire hazards. Natural fire frequency apparently coincides with levels of fuel accumulation that result in burns of relatively low intensity at frequent intervals. This may average 8 yr in mixed conifer forests, although frequencies from 4 to 20 yr or more are found in particular sites. In all probability, giant sequoia and various pines of the Sierra survive today because of the role fire plays in the various forest types. National Park Service management policies are aimed at restoring fire, as nearly as possible, to its natural role in Sierran conifer forests. This is being accomplished by prescribed burning at lower and middle elevation types and by allowing lightning fires to burn in higher elevation forests.

Post-fire reference densities for giant sequoia seedlings in a new era of high-severity wildfires

Article

Apr 2024
FOREST ECOL MANAG

Many forests globally are experiencing increases in large, high-severity wildfires, often with increasingly inadequate post-fire tree regeneration. To identify areas that might need post-fire planting, forest managers have a growing need for seedling reference densities - the natural seedling densities expected to be adequate to regenerate a forest - to compare with observed post-fire seedling densities. The most useful reference densities will meet five criteria: they will (1) be specific to natural post-fire reproduction rather than planted seedlings (because planted seedlings can have substantially greater survival than natural seedlings, thus underestimating adequate natural reproduction), (2) apply to the first few years following fire (when management decisions and actions are most likely), (3) be specific to each of those post-fire years (because post-fire seedling densities can change rapidly with time since fire), (4) be associated with estimates of uncertainty, and (5) include consideration of novel environmental conditions during management applications (because most reference densities will be based on data collected under more environmentally benign conditions). The world’s most massive tree species, the giant sequoia (Sequoiadendron giganteum) of California’s Sierra Nevada, recently experienced historically unprecedented wildfires that killed an estimated 13-19% of mature sequoias across their native range. Seedlings germinating after these fires then experienced exceptional summer heat and the two most severe summer droughts of the 121-year historical record. To help inform management responses to these events, we used seedling censuses from past fires (mostly prescribed fires) to calculate sequoia seedling reference densities meeting the five criteria. The reference densities had three striking features, which are partly attributable to giant sequoia’s status as a pioneer species. First, despite being inherently conservative, the reference densities were quite high. For example, mean first-year reference density was 172,599 seedlings/ha. Second, reference densities declined precipitously with time since fire: the mean fifth-year reference density was only 5% of the mean first-year density. Third, the reference densities were associated with relatively substantial uncertainty, a consequence of density variations among seedling plots; for example, the 95% credible interval for first-year reference density was 64,377 to 313,438 seedlings/ha. Despite this uncertainty, a case-study sequoia grove that recently burned in a high-severity wildfire had second-year post-fire seedling densities that were significantly (and dramatically) lower than the corresponding second-year reference density, suggesting inadequate post-fire reproduction. Our results highlight the value of the five criteria for reference densities - criteria that, in current practice, are rarely all met.

Post-fire reference densities for giant sequoia seedlings

Preprint

Full-text available

Jun 2023

In some areas burned by recent wildfires, most or all giant sequoias were killed. Sequoia managers wish to know whether post-fire seedling establishment in those areas has been adequate to regenerate the locally extirpated sequoias. To provide a yardstick for interpreting sequoia seedling densities measured after the recent severe wildfires, here we calculate mean seedling densities measured one, two, and five years after several mixed-severity fires of the past. Our analyses are based on 42 sites in eight different sequoia groves in Sequoia and Kings Canyon national parks, California, which burned in 26 different fires spanning a 48-year period. Conservatively (i.e., without correcting probable errors of underestimated densities), mean sequoia seedling density the first summer following fire was 153,278/ha (Bayesian estimated median = 173,742/ha; 95% credible interval [CI] = 63,319/ha to 850,336/ha). Mean seedling densities the second and fifth summers following fire were, respectively, 34,870/ha (Bayesian estimated median = 39,562; 95% CI = 14,181/ha to 181,011/ha), and 8,601/ha (Bayesian estimated median = 9,513/ha; 95% CI = 3,827/ha to 34,057/ha). Case-study comparisons showed that measured post-fire seedling densities across the Board Camp Grove and in the severely burned portions of the Redwood Mountain Grove were significantly lower than our second-year reference seedling densities.

Contrasting prescription burning and wildfires in California Sierra Nevada national parks and adjacent national forests

Article

Full-text available

Apr 2021

History of prescription burning and wildfires in the three Sierra Nevada National Park Service (NPS) parks and adjacent US Forest Service (USFS) forests is presented. Annual prescription (Rx) burns began in 1968 in Sequoia and Kings Canyon National Parks, followed by Yosemite National Park and Lassen Volcanic National Park. During the last third of the 20th century, USFS national forests adjacent to these parks did limited Rx burns, accounting for very little area burned. However, in 2004, an aggressive annual burn program was initiated in these national forests and in the last decade, area burned by planned prescription burns, relative to area protected, was approximately comparable between these NPS and USFS lands. In 1968, the NPS prescription burning program was unique because it coupled planned Rx burns with managing many lightning-ignited fires for resource benefit. From 1968 to 2017, these natural fires managed for resource benefit averaged the same total area burned as planned Rx burns in the three national parks; thus, they have had a substantial impact on total area burned by prescription. In contrast, on USFS lands, most lightning-ignited fires have been managed for suppression, but increasing attention is being paid to managing wildfires for resource benefit.

Long-Term Effects of Fuels Treatments, Overstory Structure, and Wildfire on Tree Regeneration in Dry Forests of Central Washington

Article

Full-text available

Aug 2020

The long-term effectiveness of dry-forest fuels treatments (restoration thinning and prescribed burning) depends, in part, on the pace at which trees regenerate and recruit into the overstory. Knowledge of the factors that shape post-treatment regeneration and growth is limited by the short timeframes and simple disturbance histories of past research. Here, we present results of a 15-year fuels-reduction experiment in central Washington, including responses to planned and unplanned disturbances. We explore the changing patterns of Douglas-fir regeneration in 72 permanent plots (0.1 ha) varying in overstory abundance (a function of density and basal area) and disturbance history-the latter including thinning, prescribed burning, and/or wildfire. Plots were measured before treatment (2000/2001), soon afterwards (2004/2005), and more than a decade later (2015). Thinning combined with burning enhanced sapling recruitment (ingrowth) into the overstory, although rates of ingrowth were consistently low and greatly exceeded by mortality. Relationships between seedling frequency (proportion of quadrats within a plot) and overstory abundance shifted from weakly negative before treatment to positive after thinning, to neutral in the longer term. However, these relationships were overshadowed by more recent, higher-severity prescribed fire and wildfire that stimulated seedling establishment while killing advanced regeneration and overstory trees. Our results highlight the dependence of regeneration responses on the history of, and time since, fuels treatment and subsequent disturbance. Managers must be aware of this spatial and temporal complexity and plan for future disturbances that are inevitable but unpredictable in timing and severity.

Sierra Nevada Bioregion

Chapter

Jun 2018

Fire in California's Ecosystems, Second Edition

Book

Jun 2018

Alterations to fire regimes have resulted in many changes to the biological communities in California including changes in vegetation composition and structure and vegetation type conversions or ecosystem migrations. This text details many of these changes, explains how fire has changed as an ecosystem process, and provides insights for determining the direction that the changes might take in the future. Part I provides a foundation in fire ecology for understanding fire’s varying role in the bioregions of California and the issues confronting fire in today’s society. Part II details the role of fire in each of the nine bioregions, beginning in the humid northwest and ending in the arid southeast. It should be obvious that fire has been a dynamic force in California’s ecosystems and will continue to be so in the future. How then, must this ecological fact be reconciled with need for human society to coexist with fire? Part II addresses the issues Californians must face if they are to continue live in a fire-prone landscape.

The century-long shadow of fire exclusion: Historical data reveal early and lasting effects of fire regime change on contemporary forest composition

Article

Full-text available

Jul 2023
FOREST ECOL MANAG

Discovering Douglas-Fir Woodlands in the Historical Forests of Umatilla National Forest, Eastern Oregon and Washington

Article

Full-text available

Oct 2020

We discovered unique Douglas-fir open woodlands in the Umatilla National Forest using historical surveys. Historical ponderosa pine forests of the western United States are transitioning to denser forests comprised of a greater proportion of fire-sensitive species, including true firs. We used historical (1879 to 1887) surveys to quantify the composition and structure of the Umatilla National Forest in eastern Oregon and Washington and provided contemporary forest information for comparison. We also modeled fir and pine distributions using environmental predictors and the random forests and extreme gradient boosting classifiers. Historically, ponderosa pine and Douglas-fir comprised about 80% of all trees, with western larch relatively abundant at 10% of all trees. Currently, ponderosa pine and Douglas-fir are about 40% of all trees, while grand fir and lodgepole pine increased from rare species to about 40% of all trees. Historical density was about 165 trees/ha (trees > 12.7 cm in diameter). The wetter north unit of steep slopes and predominantly Douglas-fir was about 120 trees/ha, or open woodlands, whereas the drier, flatter south units of predominantly ponderosa pine were about 210 trees/ha, and densities of 160 and 190 trees/ha occurred on flat and gentle slopes, respectively, with predominantly ponderosa pine. Currently, Umatilla National Forest averages about 390 trees/ha; the north unit of grand fir and Douglas-fir tripled in density to 365 trees/ha, whereas the south units of ponderosa and lodgepole pines doubled in density to 410 trees/ha. Douglas-fir woodlands are an unusual combination of a relatively fire-sensitive tree species with an open structure, which may result from surface fires that remove tree regeneration, resulting in one layer of trees over an understory of herbaceous and shrubby vegetation. We interpreted that a spatially and temporally variable fire return interval favored Douglas-fir, but fires were frequent enough to allow herbaceous vegetation and shrubs to out-compete trees, maintaining the balance between trees and other vegetation in woodlands. Fire exclusion has resulted in forest-type transition and also an information deficit about circumstances under which relatively fire-sensitive Douglas-fir instead of fire-tolerant ponderosa pine would establish at low densities over large extents.

California's Fourth Climate Change Assessment--Sierra Nevada Region Report

Technical Report

Full-text available

Aug 2018

http://www.climateassessment.ca.gov/regions/docs/20180827-SierraNevada.pdf

Multi-disciplinary approach to identifying Native American impacts on Late Holocene forest dynamics in the southern Sierra Nevada range, California, USA

Article

Apr 2016

Fire is a natural disturbance component and driver of forest composition in the western United States. Cooler/wetter climates are typically associated with less frequent fires and succession of montane forests to more shade-tolerant, fire-sensitive taxa. Native Americans have lived in California since the terminal Pleistocene and used fire to alter the landscape and maximize natural resources; however, determining the extent and impact of anthropogenic burning on California's landscape is difficult because the archaeological record is mostly silent on the subject, and the region's ethnographies mention the practice from a prehistoric context only in passing. Here we show that comparing the prevalence of fire-sensitive to fire-adapted taxa in the pollen record can help distinguish periods when vegetation does not respond as expected to climate change. We argue that the prevalence of shade-intolerant/fireadapted taxa during climatically cool, wet periods such as the Little Ice Age provide evidence for anthropogenic burning. At Holey Meadow, in Sequoia National Forest, we find strong evidence for a Native Americaninfluenced landscape from 750–100 cal yr BP. We also see a strong anthropogenic effect on modern vegetation following European settlement in A.D. 1854, a period marked by a precipitous decline in traditional tribal use of the area and the inception of modern fire exclusion policies. These results indicate that anthropogenic impacts on forest composition can be distinguished from climatic drivers through the use of paleoenvironmental proxies, and further indicate that anthropogenic burning helped structure Late Holocene southern Sierra Nevada biomes.

Refining Ecological Techniques for Forest Fire Prevention and Evaluating Their Diverse Benefits

Article

Full-text available

Apr 2024

In this study, an ecological framework was developed to sort out the existing forest fire prevention techniques. The subsequent analysis involved comparing the ecological values and application prospects of these techniques developed in different time periods. As ecological applications, fire regimes reflect vegetation response to wildfires, providing valuable insights for shaping the fire risk and behaviors in forests through fuel treatment and vegetation modification. Fuel treatment and the construction of green fire barriers are both rooted in existing ecosystems and possess ecological characteristics. While fuel thinning focuses on reducing the potential fire intensity and severity, green fire barriers have been more targeted for fire prevention purposes. Among these techniques, green fire barriers demonstrate unique sustainability and have the potential to generate long-term ecological and environmental benefits. Through the comprehensive utilization of several fuel management formulas, we can effectively combine the fire prevention demands with ecological maintenance and environment protection. This integrated approach promotes the development of fire-resilient ecosystems and desirable living environments in a more realistic and sustainable manner.

Thinning Combined with Prescribed Burn Created Spatially Heterogeneous Overstory Structures in Contemporary Dry Forests: A Comparison Using LiDAR (2016) and Field Inventory (1934) Data

Article

Full-text available

Oct 2023

Restoring current ponderosa pine (Pinus ponderosa Dougl. Ex P. and C. Laws)-dominated forests (also known as “dry forests”) to spatially resilient stand structures requires an adequate understanding of the overstory spatial variation of forests least impacted by Euro-American settlers (also known as “reference conditions”) and how much contemporary forests (2016) deviate from reference conditions. Because of increased tree density, dry forests are more spatially homogeneous in contemporary conditions compared to reference conditions, forests minimally impacted by Euro-American settlers. Little information is available that can be used by managers to accurately depict the spatial variation of reference conditions and the differences between reference and contemporary conditions. Especially, forest managers need this information as they are continuously designing management treatments to promote contemporary dry forest resiliency against fire, disease, and insects. To fill this knowledge gap, our study utilized field inventory data from reference conditions (1934) along with light detection and ranging and ground-truthing data from contemporary conditions (2016) associated with various research units of Blacks Mountain Experimental Forest, California, USA. Our results showed that in reference conditions, above-ground biomass—a component of overstory stand structure—was more spatially heterogeneous compared to contemporary forests. Based on semivariogram analyses, the 1934 conditions exhibited spatial variation at a spatial scale < 50 m and showed spatial autocorrelation at shorter ranges (150–200 m) compared to those observed in contemporary conditions (>250 m). In contemporary conditions, prescribed burn with high structural diversity treatment enhanced spatial heterogeneity as indicated by a greater number of peaks in the correlograms compared to the low structural diversity treatment. High structural diversity treatment units exhibited small patches of above-ground biomass at shorter ranges (~120 to 440 m) compared to the low structural diversity treatment units (~165 to 599 m). Understanding how spatial variation in contemporary conditions deviates from reference conditions and identifying specific management treatments that can be used to restore spatial variation observed in reference conditions will help managers to promote spatial variation in stand structure that has been resilient to wildfire, insects, and disease.

The scientific value of fire in wilderness

Article

Full-text available

Jun 2023

Background Wilderness areas are important natural laboratories for scientists and managers working to understand fire. In the last half-century, shifts in the culture and policy of land management agencies have facilitated the management practice of letting some naturally ignited fires burn, allowing fire to fulfill its ecological role and increasing the extent of fire-related research opportunities. With the goal of identifying the global scientific advances enabled by this paradigm shift in wilderness fire management, we conducted a systematic review of publications that either (1) selected protected areas for investigation because of an active fire regime enabled by wilderness fire management, (2) studied modern fires or fire regimes deliberately located in a wilderness area, or (3) conducted applied research to support wilderness fire management. Results Our systematic review returned a sample of 222 publications that met these criteria, with an increase in wilderness fire science over time. Studies largely occurred in the USA and were concentrated in a relatively small number of protected areas, particularly in the Northern Rocky Mountains. As a result, this sample of wilderness fire science is highly skewed toward areas of temperate mixed-conifer forests and historical mixed-severity fire regimes. Common principal subjects of publications included fire effects (44%), wilderness fire management (18%), or fire regimes (17%), and studies tended to focus on vegetation, disturbance, or wilderness management as response variables. Conclusions This work identifies major scientific contributions facilitated by fire in wilderness, including self-limitation of fire, the effects of active fire regimes on forest and aquatic systems, barriers and potential solutions to wilderness fire management, and the effect of fire on wilderness recreation and visitor experiences. Our work reveals geographic and bioclimatic areas where more research attention is needed and highlights under-represented wilderness areas that could serve to fill these gaps. Finally, we identify priorities for future wilderness fire research, including the past and potential role of Indigenous and prescribed burning, the effects of changing climate and fire regimes on ecosystem processes, and how to overcome barriers to wilderness fire management.

Repeated burns fail to restore pine regeneration to the natural range of variability in a Sierra Nevada mixed‐conifer forest, USA

Article

Dec 2022

Fire‐exclusion has acted as a major perturbation on dry conifer forests in the western U.S., increasing tree density and, in mixed‐conifer forests, the dominance of shade‐tolerant species. Restoration efforts aim to reverse these effects by reducing stand density, restoring relative proportions of tree species, and reintroducing recurrent fire, but there are limited long‐term data on the effects of repeated burning on tree regeneration. We analyzed two decades of seedling and overstory data from the Teakettle Experimental Forest in the southern Sierra Nevada, California, USA to determine how thinning and repeated burning affect seedling establishment and overstory recruitment. Across treatments, pine seedling densities remained much lower than shade‐tolerant seedling densities. We found repeated burns led to modest increases in sugar pine (Pinus lambertiana) and substantial increases in incense‐cedar (Calocedrus decurrens) seedling densities four years post‐burn. No significant differences in seedling densities among repeated burning treatments were detected for Jeffrey pine (P. jeffreyi) or white fir (Abies concolor). Estimates of natural midstory recruitment were much higher among white fir and incense‐cedar than pines, even following treatments. However, post‐harvest planting increased rates of pine midstory recruitment in overstory thinned treatments. Our results suggest that fire‐exclusion may have shifted the ecosystem out of its initial domain of attraction, creating a forest dominated by shade‐tolerant species that exhibits hysteresis by resisting a return to a natural range of variability even after restoring structure and process. Planting pine species may be effective at overcoming this resistance to restore the forest to a pine‐dominated state. This article is protected by copyright. All rights reserved.

A Semi-Empirical Retrieval Method of Above-Ground Live Forest Fuel Loads by Combining SAR and Optical Data

Article

Full-text available

Dec 2022

Forest fuel load is the key factor for fire risk assessment, firefighting, and carbon emissions estimation. Remote sensing technology has distinct advantages in fuel load estimation due to its sensitivity to biomass and adequate spatiotemporal observations for large scales. Many related works applied empirical methods with individual satellite observation data to estimate fuel load, which is highly conditioned on local data and limited by saturation problems. Here, we combined optical data (i.e., Landsat 7 ETM+) and spaceborne Synthetic Aperture Radar (SAR) data (i.e., ALOS PALSAR) in a proposed semi-empirical retrieval model to estimate above-ground live forest fuel loads (FLAGL). Specifically, optical data was introduced into water cloud model (WCM) to compensate for vegetation coverage information. For comparison, we also evaluated the performance of single spaceborne L-band SAR data (i.e., ALOS PALSAR) in fuel load estimation with common WCM. The above two comparison experiments were both validated by field measurements (i.e., BioSAR-2008) and leave-one-out cross-validation (LOOCV) method. WCM with single SAR data could achieve reasonable performance (R2 = 0.64 or higher and RMSEr = 35.3% or lower) but occurred an underestimation problem especially in dense forests. The proposed method performed better with R2 increased by 0.05–0.13 and RMSEr decreased by 5.8–12.9%. We also found that the underestimation problem (i.e., saturation problem) was alleviated even when vegetation coverage reached 65% or the total FLAGL reached about 183 Tons/ha. We demonstrated our FLAGL estimation method by validation in an open-access dataset in Sweden.

Fire Effects In Montane Meadows

Article

Mar 2022

Rosie Deak

The impact of forest fires on downstream meadow communities across California is of great ecological interest, as meadows are an important source of biodiversity in this region. Over a century of fire suppression has led to increased forest stand densities, which in turn has resulted in less water availability due to increased transpiration of densely growing trees. This potentially has left less available water for downstream plant communities in meadows. If true, then high mortality wildfires in surrounding forest are predicted to lead to an increase in available downstream moisture where obligate and facultative-wetland taxa increase and dry-adapted upland taxa decline. Here, we test this hypothesis using a dataset of 103 California montane meadows sampled before and after fire over the last 20 years. Using long term meadow monitoring data, compositional turnover is calculated for each plot from before and after fire and then evaluated against the area of 100% mortality, postfire relative-precipitation, meadow type, and proximity of the meadow to fire. We hypothesize that mortality, post-fire precipitation, and site type influence compositional turnover in meadows, regardless of proximity to the burn area. We find that compositional turnover is influenced by mortality but not by meadow type, relative precipitation, or the proximity to fire perimeter. Specifically, turnover was greater in meadows in higher mortality catchments. We then used a combination of linear models and NMDS to determine whether specific functional groups were driving higher turnover rates, expecting increases in obligate and facultative-wetland groups following high mortality fires. However we found no evidence for this. The high variation amongst meadows and their respective fire histories yielded no consistent shifts in community composition. Our findings highlight that landscape scale fire effects can interact strongly affect plant communities outside of fire perimeters, but that this does not lead to predictable shifts in wetland community composition. As fire behavior and drought are projected to become more extreme, we can expect that meadow composition will continue to change but not in predictable ways.

Learning from the past: opportunities for advancing ecological research and practice using palaeoecological data

Article

Full-text available

May 2022
OECOLOGIA

Palaeoecology involves analysis of fossil and sub-fossil evidence preserved within sediments to understand past species distributions, habitats and ecosystems. However, while palaeoecological research is sometimes made relevant to contemporary ecology, especially to advance understanding of biogeographical theory or inform habitat-based conservation at specific sites, most ecologists do not routinely incorporate palaeoecological evidence into their work. Thus most cross-discipline links are palaeoecology → ecology rather than ecology → palaeoecology. This is likely due to lack of awareness and/or the misnomer that palaeoecology invariably relates to the “distant past” (thousands of years) rather than being applicable to the “recent past” (last ~ 100–200 years). Here, we highlight opportunities for greater integration of palaeoecology within contemporary ecological research, policy, and practice. We identify situations where palaeoecology has been, or could be, used to (1) quantify recent temporal change (e.g. population dynamics; predator–prey cycles); (2) “rewind” to a particular point in ecological time (e.g. setting restoration/rewilding targets; classifying cryptogenic species); (3) understand current ecological processes that are hard to study real-time (e.g. identifying keystone species; detecting ecological tipping points); (4) complement primary data and historical records to bridge knowledge gaps (e.g. informing reintroductions and bioindicator frameworks); (5) disentangle natural and anthropogenic processes (e.g. climate change); and (6) draw palaeoecological analogues (e.g. impacts of pests). We conclude that the possibilities for better uniting ecology and palaeoecology to form an emerging cross-boundary paradigm are as extensive as they are exciting: we urge ecologists to learn from the past and seek opportunities to extend, improve, and strengthen their work using palaeoecological data.

Develop a Landscape Scale Framework For Interagency Wildland Fuels Management Planning: Southern Sierra Geographic Information Cooperative

Technical Report

Full-text available

Sep 2003

Due to worsening hazardous fuels conditions in many areas and increasing urban encroachment into former wildlands, optimizing selection of critical areas most in need of fuels treatment has become increasingly important. Generally, managers have inadequate spatial information and analysis tools to effectively plan and implement wildland fuels treatments across agency boundaries using an ecosystem approach. Starting in 1999, southern Sierra Nevada fire and technical staffs from federal and local agencies began systematically designing and developing an interagency collaborative framework for identifying and treating fuels across landscapes. The project area included six major watersheds and an astonishing diversity of vegetation and fuel types covering an area of about 4.8 million acres in the southern Sierra Nevada Range of California. Funded through the Joint Fire Sciences Program, this initiative focused on the long-term goals of improving firefighter and public safety, reducing fiscal costs to both government agencies and the public, and achieving both ecological and hazard reduction goals across jurisdictional boundaries. Project Results After three years of diligent efforts by interdisciplinary multi-agency staffs, most of the original project goals were met and much was learned about building and maintaining successful interagency collaborative relationships. Some specific project accomplishments include the following. • Seamless geospatial datasets were developed across the entire project area with fully compliant metadata. • Continuous 24/7 access to data and analyses are now available via the internet using a web-based mapping delivery system (ssgic.cr.usgs.gov). • Collaborative analytical procedures and methods were developed to define and assess risk, hazard and values across the project's entire 4.8 million acres. • A Geographic Information Systems software tool called Asset Analyzer was developed to efficiently compare, analyze, and prioritize fuels needing treatment. • Highest priority areas needing fuels treatment were collaboratively identified across the entire project area using best available science and technology. Project Results After three years of diligent efforts by interdisciplinary multi-agency staffs, most of the original project goals were met and much was learned about building and maintaining successful interagency collaborative relationships. Some specific project accomplishments include the following. - Seamless geospatial datasets were developed across the entire project area with fully compliant metadata. - Continuous 24/7 access to data and analyses are now available via the internet using a web-based mapping delivery system (ssgic.cr.usgs.gov). - Collaborative analytical procedures and methods were developed to define and assess risk, hazard, and values across the project’s entire 4.8 million acres. - A Geographic Information Systems software tool called Asset Analyzer was developed to efficiently compare, analyze, and prioritize fuels needing treatment. - Highest priority areas needing fuels treatment were collaboratively identified across the entire project area using best available science and technology. - Written protocols and guidelines were completed to facilitate replication by other areas of the technical and analytical processes.

Drivers of understory plant communities in Sierra Nevada mixed conifer forests with pyrodiversity

Article

Full-text available

Nov 2021

Background Fire suppression in western North America increased and homogenized overstory cover in conifer forests, which likely affected understory plant communities. We sought to characterize understory plant communities and their drivers using plot-based observations from two contemporary reference sites in the Sierra Nevada, USA. These sites had long-established natural fire programs, which have resulted in restored natural fire regimes. In this study, we investigated how pyrodiversity—the diversity of fire size, severity, season, and frequency—and other environment factors influenced species composition and cover of forest understory plant communities. Results Understory plant communities were influenced by a combination of environmental, plot-scale recent fire history, and plot-neighborhood pyrodiversity within 50 m. Canopy cover was inversely proportional to understory plant cover, Simpson’s diversity, and evenness. Species richness was strongly influenced by the interaction of plot-based fire experience and plot-neighborhood pyrodiversity within 50 m. Conclusions Pyrodiversity appears to contribute both directly and indirectly to diverse understory plant communities in Sierra Nevada mixed conifer forests. The indirect influence is mediated through variability in tree canopy cover, which is partially related to variation in fire severity, while direct influence is an interaction between local and neighborhood fire activity.

Corrigendum to: Integrating remotely sensed fuel variables into wildfire danger assessment for China

Article

Oct 2021

As regulated by the ‘fire environment triangle', three major forces are essential for understanding wildfire danger: (1) topography, (2) weather and (3) fuel. Within this concept, this study aimed to assess the wildfire danger for China based on a set of topography, weather and fuel variables. Among these variables, two remotely sensed key fuel variables, fuel moisture content (FMC) and foliage fuel load (FFL), were integrated into the assessment. These fuel variables were retrieved using radiative transfer models from the MODIS reflectance products. The random forest model identified the relationships between these variables and historical wildfires and then produced a daily updated and moderate-high spatial resolution (500m) dataset of wildfire danger for China from 2001 to 2020. Results showed that this dataset performed well in assessing wildfire danger for China in terms of the ‘Area Under the Curve' value, the fire density within each wildfire danger level, and the visualisation of spatial patterns. Further analysis showed that when the FMC and FFL were excluded from the assessment, the accuracy decreased, revealing the reasonability of the remotely sensed FMC and FFL in the assessment.

Integrating remotely sensed fuel variables into wildfire danger assessment for China

Article

Full-text available

Oct 2021

As regulated by the ‘fire environment triangle’, three major forces are essential for understanding wildfire danger: (1) topography, (2) weather and (3) fuel. Within this concept, this study aimed to assess the wildfire danger for China based on a set of topography, weather and fuel variables. Among these variables, two remotely sensed key fuel variables, fuel moisture content (FMC) and foliage fuel load (FFL), were integrated into the assessment. These fuel variables were retrieved using radiative transfer models from the MODIS reflectance products. The random forest model identified the relationships between these variables and historical wildfires and then produced a daily updated and moderate-high spatial resolution (500 m) dataset of wildfire danger for China from 2001 to 2020. Results showed that this dataset performed well in assessing wildfire danger for China in terms of the ‘Area Under the Curve’ value, the fire density within each wildfire danger level, and the visualisation of spatial patterns. Further analysis showed that when the FMC and FFL were excluded from the assessment, the accuracy decreased, revealing the reasonability of the remotely sensed FMC and FFL in the assessment.

Emergence of Cross-Scale Structural and Functional Processes in Ecosystem Science

Chapter

Mar 2021

Fundamental knowledge about the processes that control the functioning of the biophysical workings of ecosystems has expanded exponentially since the late 1960s. Scientists, then, had only primitive knowledge about C, N, P, S, and H2O cycles; plant, animal, and soil microbial interactions and dynamics; and land, atmosphere, and water interactions. With the advent of systems ecology paradigm (SEP) and the explosion of technologies supporting field and laboratory research, scientists throughout the world were able to assemble the knowledge base known today as ecosystem science. This chapter describes, through the eyes of scientists associated with the Natural Resource Ecology Laboratory (NREL) at Colorado State University (CSU), the evolution of the SEP in discovering how biophysical systems at small scales (ecological sites, landscapes) function as systems. The NREL and CSU are epicenters of the development of ecosystem science. Later, that knowledge, including humans as components of ecosystems, has been applied to small regions, regions, and the globe. Many research results that have formed the foundation for ecosystem science and management of natural resources, terrestrial environments, and its waters are described in this chapter. Throughout are direct and implicit references to the vital collaborations with the global network of ecosystem scientists.

Rates, patterns, and drivers of tree reinvasion 15 years after large-scale meadow restoration treatments

Article

Jul 2021
RESTOR ECOL

Tree encroachment threatens the biodiversity and ecological functioning of grasslands worldwide. Reversing effects of encroachment requires not only removing trees, but limiting subsequent invasions, which can stall grassland reassembly. We quantified rates and patterns of conifer reinvasion of mountain grasslands (meadows) in western Oregon, 7 and 15 years after experimental tree removal with or without burning. We assessed frequency (percentage of 100 m² subplots) and density of reinvading trees in six 1‐ha plots as a function of burn treatment, abundance in the adjacent forest (a proxy for seed availability), and distance to or orientation of forest edges. After 15 years, frequency and density of colonists varied widely among plots (24–57% of subplots and 60–250 trees/ha, respectively), but burning had no effect on either measure. Abies grandis, which dominated adjacent forests, was the principal invader. Colonization by less‐common Pinus contorta and A. procera was correlated with species' density and basal area in adjacent forests, suggesting that establishment was seed limited. Annualized rates of invasion were similar between early and late sampling intervals (9‐10/trees/ha). Establishment was generally greater along the forested edges of plots (0–10 m) than in the core (10–50 m). Prominence of shade‐tolerant A. grandis along N‐facing edges suggests strong microclimatic controls on establishment. In sum, tree removal, with or without prescribed fire, is successful in reversing effects of conifer encroachment. Despite abundant seed rain, reinvasion is slow and spatially restricted. Periodic hand removal of colonizing trees, while they are small, can be done efficiently and economically. This article is protected by copyright. All rights reserved.

Spotted owls and forest fire: Comment

Article

Full-text available

Dec 2020

Western North American forest ecosystems are experiencing rapid changes in disturbance regimes because of climate change and land use legacies (Littell et al. 2018). In many of these forests, the accumulation of surface and ladder fuels from a century of fire suppression, coupled with a warming and drying climate, has led to increases in the number of large fires (Westerling 2016) and the proportion of areas burning at higher severity (Safford and Stevens 2017, Singleton et al. 2018). While the annual area burned by fire is still below historical levels (Taylor et al. 2016), some forest types in the west are burning at higher severities when compared to pre- European settlement periods (Mallek et al. 2013, Safford and Stevens 2017). As such, they face an increased risk of conversion to non-forest ecosystems (e.g., shrublands, non-native grasslands) following large, severe fires because of compromised seed sources, post-fire soil erosion and loss, high-severity re-burn, and climatic thresholds (Coppoletta et al. 2016, Stevens et al. 2017, Rissman et al. 2018, Shive et al. 2018, Wood and Jones 2019). Restoration methods such as mechanical thinning and prescribed and managed wildland fire that reduce accumulated surface and ladder fuels (e.g., removal of smalland medium-sized trees, especially non-fire adapted species) may reduce the spatial extent of severe fires and increase forest resilience to fire in a changing climate (Agee and Skinner 2005, Stephens et al. 2013, Hessburg et al. 2016, Tubbesing et al. 2019) and, in doing so, promote key ecosystem services (Hurteau et al. 2014, Kelsey et al. 2017, Wood and Jones 2019). ... The existing body of evidence suggests that spotted owls respond largely in a neutral or positive manner to lower-severity fire and smaller patches of high-severity fire that fall within the historical range of variability but that spotted owls can respond negatively to larger patches of high-severity fire. Thus, management actions that can demonstrably reduce the extent of severe fire within spotted owl habitat in a changing climate may contribute to owl conservation if those actions do not remove critical structural habitat elements positively associated with spotted owl vital rates (e.g., large, old trees) (Jones et al. 2016, 2018, Jones 2019). It is critical that future analyses examining the effects of fire on spotted owls provide sufficient context and nuance to ensure they will be beneficial to scientists and managers seeking to understand how to minimize the loss of essential owl nesting and roosting habitat to the increasing threat of high-severity fire in a changing climate.

The early years of Sequoia and Kings Canyon Science: Building a research program

Article

May 2020

David J. Parsons

Effects of Fire and Restoration on Habitats and Populations of Western Hummingbirds: A Literature Review

Technical Report

Full-text available

Mar 2020

To inform future restoration efforts, we reviewed the known effects of fire and habitat management and restoration on hummingbirds in four key habitat types in North America. We examined seven species that most commonly occur west of the Rocky Mountains: Rufous (Selasphorus rufus), Calliope (Selasphorus calliope), Broad-tailed (Selasphorus platycercus), Costa's (Calypte costae), Black-chinned (Archilochus alexandri), Anna's (Calypte anna), and Allen's (Selasphorus sasin). Our review found that most western hummingbird species respond positively to wild or prescribed fire in forested and chaparral habitats of the western United States, although some hummingbird occurrence declines following fire, possibly due to the loss of preferred nesting habitat in mature forests. Restoration practices that eradicate exotic plants, encourage the regeneration of native shrubs and flowering plants (especially understory vegetation), and promote early and mid-successional habitats connected with native stand trees will benefit hummingbirds by providing foraging habitat in migration and on breeding grounds. Restoration practices that encourage the regeneration of native shrubs, understory vegetation, and native epiphytes, while maintaining forest canopy, can also benefit hummingbirds. We also identify many critical research questions and needs which, if addressed, would improve the quantification of pre-and postfire and habitat management impacts on hummingbirds, especially Allen's and Rufous populations, which are experiencing steep population declines. _____________________________

Effects of Fire and Restoration on Habitats and Populations of Western Hummingbirds: A Literature Review

Book

Full-text available

Mar 2020

Estimation of Fuel Biomass for Grasslands Using Data Assimilation Technique

Conference Paper

Full-text available

Jul 2019

Effects of Live Fuel Moisture Content on Wildfire Occurrence in Fire-Prone Regions over Southwest China

Article

Full-text available

Oct 2019

Previous studies have shown that Live Fuel Moisture Content (LFMC) is a crucial driver affecting wildfire occurrence worldwide, but the effect of LFMC in driving wildfire occurrence still remains unexplored over the southwest China ecosystem, an area historically vulnerable to wildfires. To this end, we took 10-years of LFMC dynamics retrieved from Moderate Resolution Imaging Spectrometer (MODIS) reflectance product using the physical Radiative Transfer Model (RTM) and the wildfire events extracted from the MODIS Burned Area (BA) product to explore the relations between LFMC and forest/grassland fire occurrence across the subtropical highland zone (Cwa) and humid subtropical zone (Cwb) over southwest China. The statistical results of pre-fire LFMC and cumulative burned area show that distinct pre-fire LFMC critical thresholds were identified for Cwa (151.3%, 123.1%, and 51.4% for forest, and 138.1%, 72.8%, and 13.1% for grassland) and Cwb (115.0% and 54.4% for forest, and 137.5%, 69.0%, and 10.6% for grassland) zones. Below these thresholds, the fire occurrence and the burned area increased significantly. Additionally, a significant decreasing trend on LFMC dynamics was found during the days prior to two large fire events, Qiubei forest fire and Lantern Mountain grassland fire that broke during the 2009/2010 and 2015/2016 fire seasons, respectively. The minimum LFMC values reached prior to the fires (49.8% and 17.3%) were close to the lowest critical LFMC thresholds we reported for forest (51.4%) and grassland (13.1%). Further LFMC trend analysis revealed that the regional median LFMC dynamics for the 2009/2010 and 2015/2016 fire seasons were also significantly lower than the 10-year LFMC of the region. Hence, this study demonstrated that the LFMC dynamics explained wildfire occurrence in these fire-prone regions over southwest China, allowing the possibility to develop a new operational wildfire danger forecasting model over this area by considering the satellite-derived LFMC product.

Forest structure and pattern vary by climate and landform across active-fire landscapes in the montane Sierra Nevada

Article

Apr 2019
FOREST ECOL MANAG

Restoration of fire-dependent forests is often guided by reference conditions from forests with an active fire regime, thought to be resilient to current and future disturbances and stresses. Reference conditions are usually based on historical data or reconstruction, which greatly limits the scale and completeness of data that can be collected. In the Sierra Nevada of California, large areas with reintroduced active fire regimes coupled with extensive lidar data coverage provide the unique opportunity to develop a contemporary regional reference condition dataset across a wide gradient of biophysical conditions. We developed this dataset with a focus on three questions: (1) What is the geographic and environmental distribution of restored active-fire forest areas in the Sierra Nevada mixed-conifer zone? (2) What are the ranges of variation in forest structure and spatial patterns across reference areas? And (3) How do stand density, tree clumping, and canopy opening patterns vary by topography and climate in reference areas? We analyzed fire history and environmental conditions over 10.8 million ha, including 3.9 million ha in the Sierra Nevada mixed-conifer zone, and found 30,377 ha of restored active-fire areas. Although reference areas were distributed throughout the Sierra Nevada they were more abundant on National Park lands (81% of reference areas) than National Forest lands and were associated with higher lightning strike density. Lidar-measured ranges of variation in reference condition structure were broad, with tree densities of 6–320 trees ha⁻¹ (median 107 trees ha⁻¹), basal area of 0.01–113 m² ha⁻¹ (median 21 m² ha⁻¹), average size of closely associated clumps of trees from >1 to 207 trees (median 3.1 trees), and average percent of stand area >6 m from the nearest canopy ranging from 0% to 100% (median 5.1%). These ranges correspond well with past studies reporting density and spatial patterns of contemporary and historical active-fire reference stands in the Sierra Nevada, except this study observed greater total variation due to the much greater spatial extent of sampling. Within the montane forest zone, reference areas at middle elevations had lower density (86 vs. 121 trees ha⁻¹), basal area, (13.7 vs. 31 m² ha⁻¹), and mean clump size (2.7 vs. 4.0 trees) compared to lower- and higher-elevation reference areas, while ridgetops had lower density (101 vs. 115 trees ha⁻¹), basal area (19.6 vs. 24.1 m² ha⁻¹), and mean clump size (3.0 vs. 3.3 trees) and more open space (7.4% vs. 5.1%) than other landforms. Many of the relationships between physiography and reference structure were context-dependent, suggesting that management practices should create heterogeneous forest structure congruent with local climatic and topographic factors influencing stand conditions.

Assessing relative differences in smoke exposure from prescribed, managed, and full suppression wildland fire

Article

Full-text available

Jan 2019

A novel approach is presented to analyze smoke exposure and provide a metric to quantify health-related impacts. Our results support the current understanding that managing low-intensity fire for ecological benefit reduces exposure when compared to a high-intensity full suppression fire in the Sierra Nevada of California. More frequent use of fire provides an opportunity to mitigate smoke exposure for both individual events and future emission scenarios. The differences in relative exposure between high-intensity, low-intensity, and prescribed burn were significant (P value < 0.01). Suppressing fire not only appears to shift the health burden of the emissions to a future date but also increases the intensity and number of people exposed in a single exposure. Increased use of ecologically beneficial fire may further be optimized to reduce human exposure through advantageous use of good dispersal conditions and incorporating a mitigation strategy that includes poor dispersal when smoke is largely over wilderness or other natural areas. Accepting naturally occurring fire typical of the environmental system benefits forest health and reduces public exposure to smoke.

Near Real-Time Extracting Wildfire Spread Rate from Himawari-8 Satellite Data

Article

Full-text available

Oct 2018

Fire Spread Rate (FSR) can indicate how fast a fire is spreading, which is especially helpful for wildfire rescue and management. Historically, images obtained from sun-orbiting satellites such as Moderate Resolution Imaging Spectroradiometer (MODIS) were used to detect active fire and burned area at the large spatial scale. However, the daily revisit cycles make them inherently unable to extract FSR in near real-time (hourly or less). We argue that the Himawari-8, a next generation geostationary satellite with a 10-min temporal resolution and 0.5–2 km spatial resolution, may have the potential for near real-time FSR extraction. To that end, we propose a novel method (named H8-FSR) for near real-time FSR extraction based on the Himawari-8 data. The method first defines the centroid of the burned area as the fire center and then the near real-time FSR is extracted by timely computing the movement rate of the fire center. As a case study, the method was applied to the Esperance bushfire that broke out on 17 November, 2015, in Western Australia. Compared with the estimated FSR using the Commonwealth Scientific and Industrial Research Organization (CSIRO) Grassland Fire Spread (GFS) model, H8-FSR achieved favorable performance with a coefficient of determination (R2) of 0.54, mean bias error of –0.75 m/s, mean absolute percent error of 33.20% and root mean square error of 1.17 m/s, respectively. These results demonstrated that the Himawari-8 data are valuable for near real-time FSR extraction, and also suggested that the proposed method could be potentially applicable to other next generation geostationary satellite data.

Using Paleolandscape Modeling to Investigate the Impact of Native American–Set Fires on Pre-Columbian Forests in the Southern Sierra Nevada, California, USA

Article

Jun 2018

Ethnographic accounts document widespread use of low-intensity surface fires by California's Native Americans to manage terrestrial resources, yet the effects of such practices on forest composition and structure remain largely unknown. Although numerous paleoenvironmental studies debate whether proxy interpretations indicate climatic or anthropogenic drivers of landscape change, available data sources (e.g., pollen, charcoal) are generally insufficient to resolve anthropogenic impacts and do not allow for hypothesis testing. We use a modeling approach with LANDIS-II, a spatially explicit forest succession and disturbance model, to test whether the addition of Native American–set surface fires was necessary to approximate vegetation change as reconstructed from fossil pollen. We use an existing 1,600-year pollen and charcoal record from Holey Meadow, Sequoia National Forest, California, as the empirical data set to which we compared modeled results of climatic and anthropogenic fire regimes. We found that the addition of anthropogenic burning best approximated fossil pollen–reconstructed vegetation change, particularly during periods of prolonged cooler, wetter periods coinciding with greater regional Native American activity (1550–1050 and 750–100 cal yr BP). For lightning-caused wildfires to statistically approximate the pollen record required at least twenty times more ignitions and 870 percent more area burned annually during the Little Ice Age (750–100 cal yr BP) than observed during the modern period (AD 1985–2006), a level of natural fire increase we consider highly improbable. These results demonstrate that (1) anthropogenic burning was likely an important cause of pre-Columbian forest structure at the site and (2) dynamic landscape models provide a valuable method for testing hypotheses of paleoenvironmental change.

Climate Change, Forest Fires, and Health in California

Chapter

Jan 2018

Wildland fire is an important component to ecological health in California forests. Wildland fire smoke is a risk factor to human health. Exposure to smoke from fire cannot be eliminated, but managed fire in a fire-prone ecosystem for forest health and resiliency allows exposure to be mitigated while promoting other ecosystem services that benefit people. The California Sierra Nevada is a paragon of land management policy in a fire-prone natural system. Past fire suppression has led to extreme fuel loading where extreme fire events are much more likely, particularly with climate change increasing the length of fire season and the probability of extreme weather. We use the California Sierra Nevada to showcase the clash of increased development and urbanization, past land management policy, future scenarios including climate change, and the intertwining of ecological health and human health. Fire suppression to avoid smoke impact has proven to be an unreliable way to decrease smoke-related health impacts. Instead ecological beneficial fires should be employed, and their management should be based on smoke impacts at monitors, making air monitoring the foundation of fire management actions giving greater flexibility for managing fires. Tolerance of smoke impacts from restoration fire that is best for forest health and resiliency, as well as for human health, is paramount and preferred over the political expediency of reducing smoke impacts today that ignores that we are mortgaging these impacts to future generations.

Retrieval of forest fuel moisture content using a coupled radiative transfer model

Article

Sep 2017
ENVIRON MODELL SOFTW

Forest fuel moisture content (FMC) dynamics are paramount to assessing the forest wildfire risk and its behavior. This variable can be retrieved from remotely sensed data using a radiative transfer model (RTM). However, previous studies generally treated the background of forest canopy as soil surface while ignored the fact that the soil may be covered by grass canopy. In this study, we focused on retrieving FMC of such forestry structure by coupling two RTMs: PROSAIL and PRO-GeoSail. The spectra of lower grass canopy were firstly simulated by the PROSAIL model, which was then coupled into the PRO-GeoSail model. The results showed that the accuracy level of retrieved FMC using this coupled model was better than that when the PRO-GeoSail model used alone. Further analysis revealed that low FMC condition fostered by fire weather condition had an important influence on the breakout of a fire during the study period.

Sierra Nevada Network: Vital Signs Monitoring Plan

Technical Report

Full-text available

Jan 2007

This document describes the long-term monitoring plan for four National Park Service (NPS) units in the Sierra Nevada of central California: Devils Postpile National Monument, Sequoia and Kings Canyon National Parks, and Yosemite National Park. Together these parks make up the Sierra Nevada Network (SIEN), which the NPS created for the purpose of establishing and implementing an ecological inventory and monitoring program. Development of large-scale monitoring programs, to be carried out over long periods, requires investment in iterative strategic planning, over a period of several years. Establishment of the monitoring portion of the SIEN program is directed by national-level guidance. The monitoring plan for each of the 32 Inventory & Monitoring (I&M) networks around the country is written in “four” phases. Each phase corresponds to a phase of program development, over a period of approximately four years.

Fish life histories, wildfire, and resilience-a case study of rainbow trout in the Boise river, Idaho

Article

Full-text available

Jan 2012

Unraveling the impact of wildfires on permafrost ecosystems: Vulnerability, implications, and management strategies

Article

Apr 2024
J ENVIRON MANAGE

Permafrost regions play an important role in global carbon and nitrogen cycling, storing enormous amounts of organic carbon and preserving a delicate balance of nutrient dynamics. However, the increasing frequency and severity of wildfires in these regions pose significant challenges to the stability of these ecosystems. This review examines the effects of fire on chemical, biological, and physical properties of permafrost regions. The physical, chemical, and pedological properties of frozen soil are impacted by fires, leading to changes in soil structure, porosity, and hydrological functioning. The combustion of organic matter during fires releases carbon and ni- trogen, contributing to greenhouse gas emissions and nutrient loss. Understanding the interactions between fire severity, ecosystem processes, and the implications for permafrost regions is crucial for predicting the impacts of wildfires and developing effective strategies for ecosystem protection and agricultural productivity in frozen soils. By synthesizing available knowledge and research findings, this review enhances our understanding of fire severity’s implications for permafrost ecosystems and offers insights into effective fire management strategies.

Change Exposes the Complications of Wildland Fire Full Suppression Policy and Smoke Management in the Sierra Nevada of California, USA

Chapter

Jan 2024

Fire and climate change in the Sierra Nevada of California, USA have a complex interaction with human land management and forest ecology. Fire was an important agent of change for the fire prone forests of this landscape. Many species, such as the Giant Sequoia (Sequoiadendron giganteum) evolved to take advantage of frequent fire as this natural process sculpted the environment. Native Americans used fire widely for socioeconomic benefit and fuel reduction with moderate intensity fire encouraged to burn across the land. Euro-American settlement brought about an era of suppression that increased fuels and changed the forest composition and structure. But, suppression was and is the simple seeming solution. Even if suppression is not sustainable it will garner support. Historic suppression has currently brought an extreme fuel problem that has manifested into a greater and greater threat of destructive high intensity fire not typical of this ecosystem. Fire policy was and is slow to change due to risk aversion and lack of urgency. This is not in small part from increased smoke impacts as a result of heavy fuel loads and returning fire to the landscape. These emissions were essentially mortgaged to the current age from previous generations. Fire and land management policies collide with air regulatory policy in California because of already heavily anthropogenically polluted air with little to no capacity for an additional emission source. However, fire and the subsequent smoke are inevitable. Public smoke tolerance is low and a significant deterrent to bringing fire back to California wilderness.

Multi-modal temporal CNNs for live fuel moisture content estimation

Article

Aug 2022
ENVIRON MODELL SOFTW

Live fuel moisture content (LFMC) is an important environmental indicator used to measure vegetation conditions and monitor for high fire risk conditions. However, LFMC is challenging to measure on a wide scale, thus reliable models for estimating LFMC are needed. Therefore, this paper proposes a new deep learning architecture for LFMC estimation. The architecture comprises an ensemble of temporal convolutional neural networks that learn from year-long time series of meteorological and reflectance data, and a few auxiliary inputs including the climate zone. LFMC estimation models are designed for two training and evaluation scenarios, one for sites where historical LFMC measurements are available (within-site), the other for sites without historical LFMC measurements (out-of-site). The models were trained and evaluated using a large database of LFMC samples measured in the field from 2001 to 2017 and achieved an RMSE of 20.87% for the within-site scenario and 25.36% for the out-of-site scenario.

Multi-Modal Temporal Cnns for Live Fuel Moisture Content Estimation

Preprint

Jan 2022

A Remote Sensing and Meteorological Data-Based Methodology for Wildfire Danger Assessment for China

Conference Paper

Sep 2020

Difference in Regeneration Conditions in Pinus ponderosa Dominated Forests in Northern California, USA, over an 83 Year Period

Article

Full-text available

May 2020

Forest inventories based on field surveys can provide quantitative measures of regeneration such as density and stocking proportion. Understanding regeneration dynamics is a key element that supports silvicultural decision-making processes in sustainable forest management. The objectives of this study were to: 1) describe historical regeneration in ponderosa pine dominated forests by species and height class, 2) find associations of regeneration with overstory, soil, and topography variables, 3) describe contemporary regeneration across various management treatments, and 4) compare differences in regeneration between historical and contemporary forests. The study area, a ponderosa pine (Pinus ponderosae Dougl. ex P. and C. Law) dominated forest, is located within the Blacks Mountain Experimental Forest (BMEF) in northeastern California, United States, which was designated as an experimental forest in 1934. We used 1935 and 2018 field surveyed regeneration data containing information about three species—ponderosa pine, incense-cedar (Calocedrus decurrens (Torr.) Florin) and white fir (Abies concolor (Grod. and Glend)—and four height classes: class 1: 0–0.31 m, class 2: 0.31–0.91 m, class 3: 0.91–1.83 m, and class 4: >1.83 m and

The effectiveness of adding fire for air quality benefits challenged: A case study of increased fine particulate matter from wilderness fire smoke with more active fire management

Article

Dec 2019
FOREST ECOL MANAG

The Lion Fire 2011 (LF11) and Lion Fire 2017 (LF17) were similar in size, location, and smoke transport. The same locations were used to monitor both fires for ground level fine particulate matter (PM2.5). Ground level PM2.5 is used to determine the relative smoke exposure from fire management tactics used during LF11 and LF17. The LF11 had a defined and determined perimeter and the fire, largely, grew to the containment lines with meteorological and fire conditions often determining the fire spread and intensity. For smoke management and air quality concerns, the LF17 introduced additional fire in an effort to speed up the burn and take advantage of good dispersal conditions similar to a prescribed fire. The LF17 had 2151 ha of fire added while the LF11 had only 874 ha. While emissions of PM2.5 for the LF17 (8062 Mg) were less than half the LF11 (19,105 Mg), ground level concentrations of PM2.5 were greater for the LF17 at all smoke impacted sites. The sites of Johnsondale and Camp Nelson experienced the highest concentrations for both fires with an increase mean concentration for the entirety of the fires from 5.8 µgm⁻³ for the LF11 to 26.0 µgm⁻³ for the LF17 at Johnsondale (p = 0.003) and 4.9 µgm⁻³ (LF11) to 35.9 µgm⁻³ (LF17) at Camp Nelson (p = 0.01). The National Ambient Air Quality 98th percentile daily average increased from the LF11 to the LF17 from 35.0 µgm⁻³ to 57.3 µgm⁻³ at Johnsondale and 28.0 µgm⁻³ to 52.6 µgm⁻³ at Camp Nelson. Adding fire as a tactic for good smoke dispersal to mitigate smoke exposure, as was one of the decision parameters for LF17, increased ground concentrations and exposure of smoke to surrounding communities above what was experienced during the LF11.

Wildland Fire, Extreme Weather and Society: Implications of a History of Fire Suppression in California, USA

Chapter

Jan 2020

Wildland fire is a natural process integral to the formation and health of forest ecosystems globally. California, USA, is case study where large areas of wildland have a recent 100 plus year history of human suppression of fire that with extreme weather is combining to create large high intensity burns changing both species composition and increasing threats to life, health and property. The cool wet winters and hot dry summers in California produce a climate where fire is common and many environmental systems have evolved to rely on frequent fire for reproduction and health. Fire has been systemically removed creating a backlog of fuels as vegetation normally burned accumulates. Extreme weather enhanced by climate change is increasing the duration of the fire season and occurrence of extreme fire weather and events. The abundance of fuels and increase in probability of fire, primarily due to human-caused ignitions in the wildland–urban interface, are creating an increase of large catastrophic fires not typical of these ecosystems. These large high-intensity fires are an immediate threat to life and property, produce large amounts of smoke impacting human health far from the fire, and leave behind a burn area then susceptible to extreme rainfall events that create landslides and mudslides. Returning fire to the historic role it has played in sustaining these systems reduces the probability of catastrophic fire and the conditions where extreme rainfall can additionally cause further threats to life and property from debris flows. Exposure of the public to smoke from wildfire increases when high intensity burns occur. Wildland fire typical of this ecosystem which occurred before suppression limited the extent and amount of such exposure. There are current attempts to effect positive change to policy and give a voice to the role of fire in the ecosystem. Long-standing policy based on the unsustainable complete exclusion of fire and public pressure on air quality inhibits functional change to smoke and fire management. The collision of what current fire and smoke science advises as the appropriate action (inclusion of fire as a land management tool), and public opinion driving implementation of fire management decisions in California (the exclusion of fire) illustrates a global problem where climate change and policy driven by belief are synergistically worsening environmental and human health.

Vegetation, Fire Regimes, and Forest Dynamics

Chapter

Jan 1999

Richard A. Minnich

The San Bernardino Mountains (SBM) have remarkably diverse shrub land and conifer forest communities in association with climatic gradients produced by large elevational relief. Wildland fire also plays a vital role affecting species composition, vegetation structure, and biogeography. In evaluating the effects of air pollution in SBM, it is important to consider fire disturbance as a mediator in stand dynamics and postfire successions and, in particular, how structural changes of some ecosystems due to a century of fire exclusion may have selectively altered the fitness and competitiveness of species, thereby affecting their resistance to air pollution. This chapter serves two goals: (1) to describe the vegetation of SBM, and (2) to evaluate the fire ecology of major ecosystems.

Fire history and stand development of a Douglas-fir/hardwood forest in northern California

Article

Jan 1994
NORTHWEST SCI

Thesis (M.S.)--Humboldt State University, 1991. Includes bibliographical references (leaves 66-70). Typescript (photocopy).

Erratum to: The carbon balance of reducing wildfire risk and restoring process: an analysis of 10-year post-treatment carbon dynamics in a mixed-conifer forest

Article

Oct 2015

Forests sequester carbon from the atmosphere, helping mitigate climate change. In fire-prone forests, burn events result in direct and indirect emissions of carbon. High fire-induced tree mortality can cause a transition from a carbon sink to source, but thinning and prescribed burning can reduce fire severity and carbon loss when wildfire occurs. However, treatment implementation requires carbon removal and emissions to reduce high-severity fire risk. The carbon removed and emitted during treatment may be resequestered by subsequent tree growth, although there is much uncertainty regarding the length of time required. To assess the long-term carbon dynamics of thinning and burning treatments, we quantified the 10-year post-treatment carbon stocks and 10-year net biome productivity (NBP) from a full-factorial experiment involving three levels of thinning and two levels of burning in a mixed-conifer forest in California’s Sierra Nevada. Our results indicate that (1) the understory thin treatment, that retained large trees, quickly recovered the initial carbon emissions (NBP = 31.4 ± 4.2 Mg C ha−1), (2) the carbon emitted from prescribed fire in the burn-only treatment was resequestered within the historical fire return interval (NBP = 32.8 ± 3.5 Mg C ha−1), and (3) the most effective treatment for reducing fire risk, understory thin and burn, had negative NBP (−6.0 ± 4.5 Mg C ha−1) because of post-fire large tree mortality. Understory thinning and prescribed burning can help stabilize forest carbon and restore ecosystem resilience, but this requires additional emissions beyond only thinning or only burning. Retaining additional mid-sized trees may reduce the carbon impacts of understory thinning and burning.

Chapter 9. A Geographical Perspective on Germination Ecology

Chapter

Dec 1998

This chapter illustrates what is known about the germination ecology of plants growing in various types of vegetation throughout the world. To facilitate organization of the mass of literature, classification system of the vegetation zones has been adopted as a general outline. Vegetation is divided into two broad categories, such as tropical and subtropical zones, and next, temperate and arctic zones. This chapter discusses the germination ecology of plants in tropical and subtropical zones, whereas chapter 10 deals with the species in temperate and arctic zones. The germination ecology of plants in each of these four vegetation zones, as well as that of species on tropical mountains is covered. For each type of vegetation, a detailed discussion along with a summary on the germination of trees, shrubs, vines, and herbaceous species is made available. Weeds are also considered, and attention is given to special biotic and abiotic factors influencing germination. Although environmental conditions associated with shade on the forest floor are required for the germination of some seeds, these conditions may be favorable for the growth of seedlings and juveniles. Many canopy, as well as emergent, tree species require a gap in the canopy, and thus, an increase in light, before young individuals can grow to maturity.

Reference conditions for Giant Sequoia forest restoration: structure, process, and precision

Conference Paper

Nov 1999

Nathan L. Stephenson

National Park Service policy directs that more natural conditions be restored to giant sequoia groves, which have been altered by a century of fire exclusion. Efforts to find a reasonable and practical definition of "natural" have helped drive scientists and land managers to use past grove conditions as reference conditions for restoration. Extensive research aimed at determining reference conditions has demonstrated that past fire regimes can be characterized with greater precision than past grove structures. Difficulty and imprecision in determining past grove structure has helped fuel a debate between "structural restorationists," who believe that forest structure should be restored mechanically before fire is reintroduced, and "process restorationists," who believe that simple reintroduction of fire is appropriate. I evaluate old and new studies from sequoia groves to show that some of the arguments of both groups have been flawed. Importantly, it appears that restoration of fire without a preceding mechanical restoration may restore the pre-Euro-American structure of sequoia groves, at least within the bounds of our imprecise knowledge of past grove structure. However, the same may not be true for all forest types that have experienced lengthy fire exclusion. Our ability to draw robust generalizations about fire's role in forest restoration will depend heavily on a thorough understanding of past and present interactions among climate, fire, and forest structure. Use of reference conditions will be central to developing this understanding.

Habitat Restriction in Giant Sequoia: The Environmental Control of Grove Boundaries

Article

Full-text available

Jan 1972

Philip W. Rundel

Present boundaries of the giant sequoia groves of the Sierra Nevada appear to be remarkably stable. The maintenance of grove boundaries is controlled by an interaction of moisture availability, temperature and the tolerances of the seedling stage of giant sequoia. Measurements of soil-moisture stress and water-potential measurements of coniferous species within the Giant Forest, the largest extant giant sequoia grove, indicate that conditions of water availability for plant growth are more favorable inside the grove than outside. Although some soils outside the grove did not reach the permanent wilting point during the summer of 1968, pressure-bomb studies have shown that significant differences in water stress do occur between grove and non-grove habitats. High levels of soil moisture appear to be maintained within the Giant Forest during the dry summer months by the input of ground water whose hypothetical origin is summer thunderstorms in the High Sierra. This ground water percolates down to lower elevations where it appears in the soil profile of the grove. Outside of the grove, there is little input of ground water during the summer months and soil moisture remains low in late summer. This percolation of high-elevation ground water into the groves during the dry summer months may be the key to the continued existence of the Giant Forest.

Community Structure and Stability in the Giant Sequoia Groves of the Sierra Nevada, California

Article

Full-text available

Apr 1971

Philip W. Rundel

The vegetation of the giant sequoia groves is dominated by Abies concolor, with Pinus lambertiana as a characteristic associate. Sequoiadendron giganteum is of small importance in relative density, but includes the majority of basal area of canopy species within the groves. Despite its great basal area, crown coverage of Sequoiadendron seldom exceeds 5%. Libocedrus decurrens is an important associate in lower-elevation groves, particularly following fire disturbance. Groundcover vegetation is extremely variable. Present grove boundaries appear to be remarkably stable. There is no evidence of any change in grove boundaries during the last 500 years or longer. A great majority of groves are undergoing a gradual decrease in density of giant sequoias due to low levels of regeneration. This decline in density began long before the influence of Western civilization on the groves.

THE USE OF FIRE IN WILDLAND MANAGEMENT IN CALIFORNIA

Chapter

Dec 1967

Harold H. Biswell

Impact of prescribed burning on a sequoia-mixed conifer forest

Article

Jan 1973

B.M. Kilgore

Culture element distributions: VI. Southern Sierra Nevada

Article

H.E. Driver

Preserving nature in forested wilderness areas and national parks

Article

M. Heinselman

Fire's role in a sequoia forest

Article

Jan 1972

B. Kilgore

Weight of the fuel complex in 70-year old lodgepole pine stands of different densities

Article

Jan 1968

A. Kiil

Seedling growth on burned soils

Article

Jan 1956

Microbiological soil properties after logging and slash burning in the Douglas-fir forest type

Article

Jan 1957

Fire and birds in the mountains of southern Arizona

Article

Jan 1963

J.T. Marshall Jr

Past fire incidence in Sierra Nevada forests

Article

Jan 1961

W.W. Wagener

Fire and its relationship to ponderosa pine

Article

Jan 1967

H. Weaver

Disaster fires—why?

Article

Jan 1969

W. Towell

Mineral content and pyrolysis of selected plant materials

Article

Jan 1968

C. Philpot

Ecology of some fire type vegetation in northern California

Article

Jan 1967

J.R. Sweeney

Dynamics of forest communities in Grand Teton National Park

Article

Jan 1971

L.L. Loope

Adaptability of animals to habitat change

Article

Jan 1966

A. Leopold

Effect upon the forest of natural fire and aboriginal burning in the Sierra Nevada

Article

Jan 1959

R. Reynolds

Commentary on the natural role of fire

Article

The effects of wildfire on plant distribution in the Southwest

Article

Jan 1969

J. Sweeney

Seedling germination following fire in a giant sequoia forest

Article

Jan 1971

The Role of Fire in Managing Red Fir Forests

Article

Jan 1971

Bruce M. Kilgore

Fire has long been a major factor in the ecology of forests in North America (Ahlgren and Ahlgren, 1960). Its role in the red fir forest of the Sierra Nevada, however, has received little study. Investigations in mixed conifer forests in Sequoia, Kings Canyon, and Yosemite National Parks by Biswell (1961), Hartesveldt (1964), and Reynolds (1959) lead to the conclusion that fires have been less numerous during the past 50 years than they were in primitive forests. Estimates of frequency in such primitive forests range from a fire every year or two to one every 21 years (1961), with a generally agreed upon average of something like 8 to 10 years between fires for individual trees. A conservative estimate would be that each tree was burned every 10 to 20 years. This is confirmed by the fire scars which some of the trees bear. As such, fires were an integral and important environmental factor in the evolution and maintenance of many plant communities in the Sierra Nevada before effective and widespread fire suppression activities came into being.

Restoring fire to the sequoias

Article

B. Kilgore

Fire ecology of the giant sequoias: Controlled fires may be one solution to survival of the species

Article

Jan 1964
NAT HIST

R.J. Hartesveldt

Giant sequoia ecology

Article

Giant sequoia ecology

Article

Jan 1967

Journal of Forestry

Article

Jan 1971

Restoring fire to high elevation forests in California

Article

Jan 1972

Litter production by bigtrees and associated species

Article

Jan 1966

Fire as an ecological factor in the southwestern ponderosa pine forests

Article

Jan 1951

H. Weaver

The natural role of fire in northern conifer forests

Article

M. Heinselman

Water repellent soils: A worldwide concern in management of soil and vegetation

Article

Jan 1969

L.F. DeBano

Breeding Bird Populations of Burned and Unburned Conifer Forest in the Sierra Nevada

Article

Apr 1970

Response of Breeding Bird Populations to Habitat Changes in a Giant Sequoia Forest

Article

Jan 1971

Bruce M. Kilgore

Thirty species from the montane forest formation comprised most of the breeding bird population of a giant sequoia forest, with a density ranging from 188 to 311 pairs per 100 acres (40 ha). When some 22 tons of living and dead trees per acre in the brush or sapling layer of this forest were eliminated by cutting, piling and prescribed burning, the change in character of vegetation and the openness of the low vegetation zone led to changes in species composition but not in total biomass of the avifauna. This was true because thickets of small trees were the least important vegetation for bird feeding or nesting; the upper canopy and understory were most important, followed by the ground and trunk categories. Two species of ground-feeding and nesting birds and a third ground-nesting species disappeared after treatment. Nesting flycatchers and robins increased in numbers. Compared with results from areas where wildfires or logging operations have made substantial changes in cover type and set succession back severely, this degree of habitat modification resulted in relatively small avifaunal changes.

Describing forest fires -old ways and new

Article

Sep 1965

C. E. van Wagner

This article deals with several ways of describing forest fires and their limitations. The simplest and oldest way is by simple verbal description. Then came the combination of rate of spread and resistance to control. The best quantitative measure of fire behaviour, however, is the rate of energy output per unit of fire front, quoted in conjunction with the linear rate of spread. If the full benefits of advances in fire control technology are to be realized, wider use of the energy output concept will probably be necessary, first among fire researchers and eventually among fire control people.

Loss of nitrogen from the forest floor by burning

Article

Jun 1966

H. Knight

Burning experiments conducted in the laboratory indicated a 25-64 per cent loss of nitrogen from the forest floor at temperatures of 300-700 °C. Burning increased the nitrogen concentration of the residual material, but the total amount of nitrogen decreased. This may explain the frequent reports of an increase in nitrogen after burning.

Effect of Forest Manipulation on Deer Habitat in Giant Sequoia

Article

Apr 1972

The effects of removing the understory trees and debris in a giant sequoia (Sequoiadendron giganteum) grove on the summer forage available to mule deer (Odocoileus hemionus californicus) were studied. On areas treated by cutting, piling, and burning, the browse and other forage was more abundant, more closely utilized, and more nutritious than on untreated control areas. The vegetational responses to the forest treatment reflected the increased sunlight and openness of the canopy.

Quantitative Studies of the Removal of Litter and Duff by Fire under Controlled Conditions

Article

Jul 1961

Ecology of Vertebrate Animals in Relation to Chaparral Fire in the Sierra Nevada Foothills

Article

Mar 1966

George E Lawrence

Chaparral fire brings decided changes in the species composition and density of both plant and animal populations in the Sierra Nevada foothills. Some species decrease whereas others increase following a burn, but not species is totally eliminated, nor is there any apparent diminution of total life on a burn after plant growth resumes. These conclusions were reached in the course of a 4-year study of adjoining burnedand unburned areas near Glennville, Kern County, California. Field work began in 1953 at which time study plots were selected and plant and vertebrate population were censused. A year later part of the study area was burned, and ensuing investigation compared populations on the burned and check areas for a period of 3 years, terminating in 1957. At the time of the fire, temperatures were recorded in sites both above and below ground, and the actions of animals were observed. There was very little evidence of direct mortality among any of the vertebrates, most of them escaping the heat in one way or another. The woodrat was perhaps the most vulnerable species because of its dependence on houses made of dry twigs. However, in the bare ash after the fire many species were severely exposed to predation, and populations of the most small mammals and some brush-dwelling birds decreased rapidly. Predatory birds and mammals increased, as did some seed-eating birds that found good foraging on the exposed earth. When the rains stimulated new plant growth, a very different habitat developed in the area of burned chaparral. Most of the original trees sustained little damage, although the pitchy digger pines were largely eliminated. However, the extensive brush stands were reduced by almost 90%, and there was a corresponding increase in invading grasses and forbs. Birds and mammals that normally exhibit a strong preference for chaparral habitat were substantially reduced in numbers in the years following the burn. Conversely, some of the birds that normally prefer grassland or oak woodland increased in number. The fire resulted in an overall increase in densities of nesting birds. None of the small mammals increased in numbers but some of the larger predators, such as the coyote and badger, moved into the burn during the months following the fire.

Fire and Management Problems in Ponderosa Pine

Article

Jan 1964

Harold Weaver

THIS ARTICLE reflects the author's views, based upon his observations during 35 years of service as a professional forester in the Western Pine Region, including his active participation in pilot plant experiments with prescribed burning that have covered over 200,000 acres of Indian forest land during the past 21 years. The time is fast approaching when the forest industry of the Ponderosa Pine Region will become dependent on younger, so-called second growth stands. The large, high quality pines that have been grown for us by nature have already been harvested over extensive areas, by the saw, by insect attacks, and by fire. On the rapidly dwindling areas of virgin timber and on partially cut forest areas under sustained yield management it is presently anticipated that the remaining large trees, in excess of 150 years of age, will be mostly harvested over the next 70 to 80 years. Throughout the region there appears a general deficiency of trees in the much needed 80-150 year age classes. Future harvests, after the large trees are gone, will have to come from presently developing reproduction stands, many of which are in the 60-70 year age classes. There is evidence, over most of the region, that pines of small saw-log size can be grown in from 120 to 160 years, provided that the trees have adequate growing space and other conditions are favorable. This might indicate that it will be possible to maintain or even to increase present annual harvesting budgets. Unfortunately, there is presently no basis for such optimism. Over extensive areas the original forest has been replaced by worthless brush fields. Reclamation of these areas will be very expensive. Over even more extensive areas, reproduction stands of ponderosa pine and of associated species are far too densely stocked for optimum growth. In addition, these dense young stands are competing for limited soil moisture with the large, high quality trees that remain. Because of resulting growth rate reduction these large trees are rendered particularly

Effect of Prescribed Burning of Forest Litter on Total Soil Nitrogen1

Article

Mar 1962

The effect of prescribed burning of ponderosa pine forest floor on soil nitrogen was investigated. Standardized soil columns were placed under the forest floor and subjected to three burning treatments: no burn, light burn, and intense burn. One‐third of the columns were removed immediately after burning, one‐third 4 months later, and the remainder 16 months later. All burning and post‐burning treatments showed net gains of nitrogen, those of no‐burn and light‐burn being greater than that for intense burning. The gain of nitrogen in the first inch of soil for the no‐burn and light‐burn treatments was 11.1 pounds per acre per year. This gain is attributed to leaching of the decomposing forest floor remaining after treatment and indicates a decomposition rate of 3.0%. The combined effects of light and intense burning reduced the nitrogen in the forest floor by 124 pounds per acre.

Wildlife management in the National Parks

Article

Jan 1969

Wildland Fires and Ecosystems--A Hypothesis

Article

Nov 1970

Robert W. Mutch

Plant species which have survived fires for tens of thousands of years may not only have selected survival mechanisms, but also inherent flammable properties that contribute to the perpetuation of fire-dependent plant communities. This concept goes by beyond the commonly accepted fire climate-fuel moisture basis of wildland fire occurrence. Plant communities may be ignited accidentally or randomly, but the character of burning is not random. The following hypothesis treats this interaction between fire and the ecosystem: Fire-dependent plant communities burn more readily than non-fire-dependent communities because natural selection has favored development of characteristics that make them more flammable. The hypothesis was experimentally derived following laboratory combustion tests with litter of eucalyptus (Eucalyptus obliqua L'Herit), ponderosa pine (Pinus ponderosa Laws.), and tropical hardwood leaves.

The Fire Ecology of Sequoia Regeneration

Article

Jan 1967

The big trees and fire

Article

Jan 1961

H. H. Biswell

Heat effects on living plants

Article

Jan 1961

R. C. Hare

Seed ecology of Sequoiadendron giganteum

Article

Jan 1968

N. Stark

The role of fire in the California pine forests

Article

A Model a Small Forest Fire . . . to Simulate Burned and Burning Areas for Use in a Detection Model

Article

Jun 1971

A computer-based model of a small smouldering or creeping forest fire has been designed to simulate burned and burning areas of a fire at any time after ignition. The model assumes that a fire spreads in a grid whose squares are homogeneous fuel types. The arrangement of fuel types within each grid for a specific cover is determined by a probability distribution and a Monte Carlo sampling procedure. Rates-of-spread of fire in each fuel type vary with changes in fuel moisture. Persistence time of fire in each fuel type is considered. The minimum time required for the fire to reach any square in the fuel grid is determined by a dynamic programming algorithm. Rates of spread are allowed to vary during the life of the fire. Forest Sci. 17:163-169.

The Ecological Role of Fire in Sierran Conifer Forests: Its Application to National Park Management

Abstract

No full-text available

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