Fuel Reduction Treatments Research Articles

Pre-wildfire fuel reduction treatments result in more resilient forest structure a decade after wildfire

Increasing size and severity of wildfires have led to an interest in the effectiveness of forest fuels treatments on reducing fire severity and post-wildfire fuels. Our objective was to contrast stand structure and surface fuel loadings on treated and untreated sites within the 2002 Rodeo–Chediski Fire area. Data from 140 plots on seven paired treated–untreated sites indicated that pre-wildfire treatments reduced fire severity compared with untreated sites. In 2011, coarse woody debris loading (woody material>7.62cm in diameter) was 257% higher and fine woody debris (woody material<7.62cm) was 152% higher on untreated sites than on treated sites. Yet, in spite of higher levels of coarse woody debris on untreated sites, loadings did not exceed recommended ranges based on published literature and many treated sites fell below recommendations. By 2011, basal area and stand density on treated sites and stand density on untreated sites met management guidelines for ponderosa pine forests, but untreated sites had basal areas well below recommendations. Snags declined over this period and only three plots had snags that met minimum size and density requirements for wildlife habitat by 2011. The effects of pre-wildfire treatments are long-lasting and contribute to changes in both overstorey and understorey fuel complexes.

Quantifying the Potential Impacts of Fuel Treatments on Wildfire Suppression Costs

Modeling the impacts and effects of hazardous fuel reduction treatments is a pressing issue within the wildfire management community. Prospective evaluation of fuel treatment effectiveness allows for comparison of alternative treatment strategies in terms of socioeconomic and ecological impacts and facilitates analysis of tradeoffs across land-management objectives. Studies have yet to rigorously examine potential impacts to fire suppression expenditures associated with prior hazardous fuel reduction treatments. Such information would be helpful for federal land-management agencies struggling to contain escalating wildfire management costs. In this article we establish a methodology for estimating potential reductions in wildfire suppression costs. Our approach pairs wildfire simulation outputs with a regression cost model and quantifies the influence of fuel treatments on distributions of wildfire sizes and suppression costs. Our case study focuses on a landscape within the Deschutes National Forest in central Oregon that was selected to receive funding under the auspices of the Collaborative Forest Landscape Restoration Program. Results suggest substantial reductions in distributions of wildfire size and suppression cost on a per fire basis. Furthermore, because fewer ignitions become large fires on the treated landscape, distributions of annual area burned and annual suppression costs also shift downward because of fuel treatments. Results are contingent on four key factors: large-scale implementation of fuel treatments across the landscape, assumed treatment effectiveness over the duration of the analysis period, accuracy of wildfire and cost models, and accuracy of projected changes to fire behavior fuel models resulting from fuel treatments. We discuss strengths and limitations of the modeling approach and offer suggestions for future improvements and applications.

Quantifying the effect of fuel reduction treatments on fire behavior in boreal forests

Mechanical (e.g., shearblading) and manual (e.g., thinning) fuel treatments have become the preferred strategy of many fire managers and agencies for reducing fire hazard in boreal forests. This study attempts to characterize the effectiveness of four fuel treatments through direct measurement of fire intensity and forest floor consumption during a single prescribed burn. The treatments included (1) thinning trees and removing debris (THIN-REMOVE-1 and -2), (2) thinning trees and burning the debris onsite, (3) shearblading and leaving the debris in place (SHEAR), and (4) shearblading and piling the debris in windrows (SHEAR-ROW). Fire burned through treatments 1, 3, and 4 and one control unit. The highest fire intensities (maximum temperature of 1150 °C, maximum heat flux of 227 kW·m–2, and fire cumulative energy release of 4277 J·m–2) were measured in the control. Treatment 1 exhibited a peak temperature of 267 °C, peak heating of 16 kW·m–2, and cumulative energy release of 2600 J·m–2. Treatments 3 and 4 exhibited peak temperatures of 170 and 66 °C, peak heating of 51 and 3 kW·m–2, and cumulative energy release of 2500 and 1800 J·m–2, respectively. The thinned treatment showed the most significant impact in the context of reduced heat release.

Assessing the Potential for Log Sort Yards to Improve Financial Viability of Forest Restoration Treatments

Forest restoration and fuel reduction treatments have been widely applied in the western United States with the purpose of reducing the size and intensity of wildfires. However, the low value of small-diameter trees produced from such treatments has partly constrained the ability to treat all the areas identified as being in need of treatments. The objective of this study was to analyze the potential for log sort yards to increase the residual value of forest restoration treatments relative to a standard sort at landing in Ravalli County, Montana. We simulated log handing and transportation under two log sorting scenarios in Ravalli County: sort at landing resulting in two log products and sort at sort yard resulting in seven potential log products. Costs and value recovery in each scenario were estimated, and the residual values were compared. We found that establishment of a log sort yard in Ravalli County could increase the residual value of forest restoration treatments by 5%. However, the benefit of the sort yard varies substantially by the forest type from which logs are harvested and the available volume of and markets for high value products, such as house logs.

Understory plant community responses to hazardous fuels reduction treatments in pinyon-juniper woodlands of Arizona, USA

Although hazardous fuels reduction projects are being implemented widely in dry forests of the western United States, information concerning ecological responses of pinyon-juniper woodlands to fuels treatments is minimal. In this study we used a randomized block experimental design to investigate effects of fuels treatments on understory responses at a pinyon-juniper woodland site in northern Arizona. Treatment alternatives replicated (n=12) on 1-ha units across the 760-ha site were thinning from below (Thin), prescribed burning, (Burn), thinning followed by prescribed burning (Thin+Burn), and untreated controls (Control). We measured cover of vascular plant species, biological soil crust, and forest floor substrate prior to treatment and one year, 2years, and five years post-treatment. After five years, Thin and Thin+Burn plots showed statistically similar total plant cover but both showed significantly greater cover than Burn and Control plots. Cover increases on Thin+Burn plots were driven mainly by annual forb and nonnative species groups. Graminoid species with the C4 photosynthetic pathway showed significantly greater cover in all treatment groups compared with Control plots. Burning alone tended to reduce shrub cover whereas thinning alone tended to increase shrub cover. We found no significant effects of treatment on cover of biological soil crust or bare soil. Regression analysis showed significant negative relationships between total understory plant cover and overstory canopy cover on burned and unburned plots. We found no significant effect of treatment on species richness over the measurement period. We observed 124 taxa in total, and mean richness ranged from 31.8 to 36.8 species per 500m2 in 2011. Similar to results for plant cover, we found significantly greater numbers of annual forb species in Thin+Burn compared with Control plots and significantly greater numbers of nonnative species in Thin+Burn compared with all other treatment groups. Permutational multivariate analysis of variance showed no significant differences in overall plant community composition among treatments. These results indicate that fuel reduction treatments on woodland sites may not dramatically affect understory abundance or composition within five years. Although treatments did not significantly differ in cover of biological soil crust or bare soil – indicators of ecosystem function – our results showed that thinning treatments followed by prescribed fire led to increases in cover of nonnative plant species.

Factors influencing northern spruce engraver colonization of white spruce slash in interior Alaska

In interior Alaska, increased use of mechanical fuel reduction treatments, increased interests in the use of wood energy systems as alternatives to fossil fuels, and elevated populations of northern spruce engraver, Ips perturbatus (Eichhoff), have raised concerns regarding the impact of this bark beetle to forest resources. We conducted a large-scale field study in 2009−2011 (Study 1) to determine the effects of slash scoring (mechanical by chainsaw versus none), slash distribution (scattered versus decked), and cutting date (spring versus fall) on I. perturbatus colonization of and reproductive performance in white spruce, Picea glauca (Moench) Voss, slash, and to determine the effects of resulting treatments on adjacent levels of tree mortality caused by I. perturbatus. Unfortunately, attack densities were lower than expected, and did not provide for a very robust examination of the effects of these treatments. As a result, we reproduced several aspects of Study 1 in a second study (2011) using a baited design. Higher levels of I. perturbatus attack and emergence occurred on dispersed logs. Attack densities were highest in the dispersed, unscored treatment, and ∼70% higher than observed in the decked, scored treatment. The scoring of dispersed logs significantly reduced attack densities by ∼28%, but had no effect in decked treatments or on levels of emergence in either treatment. Higher levels of attack and emergence were observed on the tops of logs as compared to the bottoms of logs. Brood production (i.e., defined here as emergence/attacks) was also greater on the tops of logs compared to the bottoms of logs, suggesting the tops of logs are not only more attractive to I. perturbatus, but confer some advantage to brood development. Lower levels of attack and emergence occurred on small diameter logs. Higher levels of attack and emergence were observed on logs in a shaded fuelbreak (i.e., a more open condition of lower tree density) compared to the adjacent forest. Overall, our research suggests that unlike other works on Ips spp. in the western USA that promote the desiccation of slash to minimize colonization and brood production, I. perturbatus appears regulated by the apparency and accessibility of host material. This finding highlights the importance of developing management guidelines based on local science. A third study found two semiochemicals, trans-conophthorin and verbenone, reduced colonization of slash by I. perturbatus, and therefore holds promise as a tool for managing I. perturbatus populations. The implications of these and other results to the management of I. perturbatus in interior Alaska are discussed.

Ecological effects of alternative fuel-reduction treatments: highlights of the National Fire and Fire Surrogate study (FFS)

The 12-site National Fire and Fire Surrogate study (FFS) was a multivariate experiment that evaluated ecological consequences of alternative fuel-reduction treatments in seasonally dry forests of the US. Each site was a replicated experiment with a common design that compared an un-manipulated control, prescribed fire, mechanical and mechanical + fire treatments. Variables within the vegetation, fuelbed, forest floor and soil, bark beetles, tree diseases and wildlife were measured in 10-ha stands, and ecological response was compared among treatments at the site level, and across sites, to better understand the influence of differential site conditions. For most sites, treated stands were predicted to be more resilient to wildfire if it occurred shortly after treatment, but for most ecological variables, short-term response to treatments was subtle and transient. Strong site-specificity was observed in the response of most ecosystem variables, suggesting that practitioners employ adaptive management at the local scale. Because ecosystem components were tightly linked, adaptive management would need to include monitoring of a carefully chosen set of key variables. Mechanical treatments did not serve as surrogates for fire for most variables, suggesting that fire be maintained whenever possible. Restoration to pre-settlement conditions will require repeated treatments over time, with eastern forests requiring more frequent applications.

Using Fire to Increase the Scale, Benefits, and Future Maintenance of Fuels Treatments

The Forest Service is implementing a new planning rule and starting to revise forest plans for many of the 155 National Forests. In forests that historically had frequent fire regimes, the scale of current fuels reduction treatments has often been too limited to affect fire severity and the Forest Service has predominantly focused on suppression. In addition to continued treatment of the wildland urban interface, increasing the scale of low- and moderate-severity fire would have substantial ecological and economics benefits if implemented soon. We suggest National Forests identify large contiguous areas to concentrate their fuels reduction efforts, and then turn treated firesheds over to prescribed and managed wildfire for future maintenance. A new round of forest planning provides an opportunity to identify and overcome some of the current cultural, regulatory and institutional barriers to increased fire use that we discuss.

Bark beetle outbreaks, wildfires and defensible space: how much area do we need to treat to protect homes and communities?

Extensive beetle outbreaks across western North American forests have spurred debates about how to best protect communities from wildfire. Previous work has found that fuels in the wildland–urban interface and especially in the defensible space (40-m radius) around structures are the most important determinants of the flammability of structures during wildfire. We: (1) examined the extent of outbreaks in the western US and their intersection with the wildland-urban interface and its surrounding area and (2) calculated the combined area of defensible space around all wildland-urban interface housing units in the western US. This analysis indicates that: (1) >98% of areas affected by outbreaks are in remote areas rather than in the wildland-urban interface and (2) in the context of limited resources and the goal of protecting homes and communities from wildfire, the area required to create defensible space around all homes in the wildland-urban interface of the western US (which effectively reduces fire risk to structures) is substantially less than that needed to treat all beetle-affected forests (which does not reduce fire risk to structures as effectively). Thus, focussing fuel-reduction treatments in the immediate vicinity of homes and communities rather than in remote beetle-affected forests would be more effective at reducing fire risk to those structures and would incur lower financial and ecological costs.

Estimating consumption and remaining carbon in burned slash piles

Fuel reduction treatments to reduce fire risk have become commonplace in the fire adapted forests of western North America. These treatments generate significant woody debris, or slash, and burning this material in piles is a common and inexpensive approach to reducing fuel loads. Although slash pile burning is a common practice, there is little information on consumption or even a common methodology for estimating consumption. As considerations of carbon storage and emissions from forests increase, better means of quantifying burn piles are necessary. This study uses two methods, sector sampling and a form of line intersect sampling, for estimating both the percent consumption and conversion to charcoal in slash piles of ponderosa pine ( Pinus ponderosa Douglas ex P. Lawson & C. Lawson) in northern Arizona, USA. On average, burning released between 92% and 94% of the carbon in each slash pile to the atmosphere and converted between 0.05 and 0.34 Mg C·ha–1 to charcoal across the treatment area. These results demonstrate that burning slash piles converts significant quantities of carbon stored in wood to atmospheric carbon and charcoal, both of which should be considered as forest carbon accounting is further refined. Sector sampling and line intersect strategies produced similar estimates of consumption; however, the line intersect protocol was more easily and rapidly implemented.

Topographic Variation in Structure of Mixed-Conifer Forests Under an Active-Fire Regime

Management efforts to promote forest resiliency as climate changes have often used historical forest structure and composition to provide general guidance for fuels reduction and forest restoration treatments. However, it has been difficult to identify what stand conditions might be fire and drought resilient because historical data and reconstruction studies are generally limited to accurate estimates only of large, live tree density and composition. Other stand features such as smaller tree densities, dead wood, understory structure, regeneration, and fuel loads have been difficult to quantify, estimate how they may vary across a landscape, or assess how they would be affected by fire under current climate conditions. We sampled old-growth, mixed-conifer forests with at least two low-intensity fires within the last 65 years in 150 plots at 48 sample sites ranging over 400 km of the Sierra Nevada. Recent fire history had the strongest influence on understory conditions with small tree density decreasing and shrub cover increasing with the increased intensity and frequency of fire associated with upper-slope and ridge-top locations. In contrast, stand structures associated with large, overstory trees such as total basal area, canopy cover, and the abundance of large snags and logs increased in topographic locations associated with more mesic, productive sites regardless of fire history. In forests with restored fire regimes, topography, fire and their interaction influence productivity and burn intensity, creating the structural heterogeneity characteristic of frequent-fire forests.

Carbon outcomes from fuels treatment and bioenergy production in a Sierra Nevada forest

In temperate conifer forests of the Western USA, there is active debate whether fuels reduction treatments and bioenergy production result in decreased carbon emissions and increased carbon sequestration compared to a no-action alternative. To address this debate over net carbon stocks, we performed a carbon life-cycle analysis on data from a fuels reduction treatment in a temperate, dry conifer forest in the northern Sierra Nevada of California, USA. The analysis tracks the net ecosystem carbon balance over 50years for two scenarios (1) fuels reduction treatment combined with bioenergy production, and (2) a baseline scenario of no action. The study includes above and belowground carbon stocks, removals from harvesting, emissions from harvesting and transporting the removed biomass, and disturbance by wildfire. We evaluate a range of fire rotations, from an historic short rotation to a modern long rotation. In this study, when the fire rotation is 31years or less, fuels treatment and bioenergy result in a net increase in carbon stocks after 50years compared to a baseline of no action. When fire rotations exceed 31years the carbon balance shifts and the baseline scenario holds more carbon after 50years than the fuels treatment. Over the 50-year period, future wildfire is the greatest source of emissions unless fire rotations are greater than 200years, when emissions from the combustion of biomass for energy are greater. Emissions from mechanical treatments and transportation of the woody biomass are each less than 1% of total emissions. The results of this case study suggest that there is no single answer to whether fuels reduction treatments with bioenergy production create net carbon benefit. Managers will need to evaluate fuels treatments on a case-by-case or regional basis to determine net carbon outcomes. The life cycle approach presented here is a useful methodology for such determinations.

Variation in tree mortality and regeneration affect forest carbon recovery following fuel treatments and wildfire in the Lake Tahoe Basin, California, USA

BackgroundForest fuel treatments have been proposed as tools to stabilize carbon stocks in fire-prone forests in the Western U.S.A. Although fuel treatments such as thinning and burning are known to immediately reduce forest carbon stocks, there are suggestions that these losses may be paid back over the long-term if treatments sufficiently reduce future wildfire severity, or prevent deforestation. Although fire severity and post-fire tree regeneration have been indicated as important influences on long-term carbon dynamics, it remains unclear how natural variability in these processes might affect the ability of fuel treatments to protect forest carbon resources. We surveyed a wildfire where fuel treatments were put in place before fire and estimated the short-term impact of treatment and wildfire on aboveground carbon stocks at our study site. We then used a common vegetation growth simulator in conjunction with sensitivity analysis techniques to assess how predicted timescales of carbon recovery after fire are sensitive to variation in rates of fire-related tree mortality, and post-fire tree regeneration.ResultsWe found that fuel reduction treatments were successful at ameliorating fire severity at our study site by removing an estimated 36% of aboveground biomass. Treated and untreated stands stored similar amounts of carbon three years after wildfire, but differences in fire severity were such that untreated stands maintained only 7% of aboveground carbon as live trees, versus 51% in treated stands. Over the long-term, our simulations suggest that treated stands in our study area will recover baseline carbon storage 10–35 years more quickly than untreated stands. Our sensitivity analysis found that rates of fire-related tree mortality strongly influence estimates of post-fire carbon recovery. Rates of regeneration were less influential on recovery timing, except when fire severity was high.ConclusionsOur ability to predict the response of forest carbon resources to anthropogenic and natural disturbances requires models that incorporate uncertainty in processes important to long-term forest carbon dynamics. To the extent that fuel treatments are able to ameliorate tree mortality rates or prevent deforestation resulting from wildfire, our results suggest that treatments may be a viable strategy to stabilize existing forest carbon stocks.

The Effects of Forest Fuel-Reduction Treatments in the United States

The current conditions of many seasonally dry forests in the western and southern United States, especially those that once experienced low- to moderate-intensity fire regimes, leave them uncharacteristically susceptible to high-severity wildfire. Both prescribed fire and its mechanical surrogates are generally successful in meeting short-term fuel-reduction objectives such that treated stands are more resilient to high-intensity wildfire. Most available evidence suggests that these objectives are typically accomplished with few unintended consequences, since most ecosystem components (vegetation, soils, wildlife, bark beetles, carbon sequestration) exhibit very subtle effects or no measurable effects at all. Although mechanical treatments do not serve as complete surrogates for fire, their application can help mitigate costs and liability in some areas. Desired treatment effects on fire hazards are transient, which indicates that after fuel-reduction management starts, managers need to be persistent with repeated treatment, especially in the faster-growing forests in the southern United States.

Short- and medium-term effects of fuel reduction mulch treatments on soil nitrogen availability in Colorado conifer forests

Mechanical fuel reduction treatments have been implemented on millions of hectares of western North American forests. The redistribution of standing forest biomass to the soil surface by mulching treatments has no ecological analog, and this practice may alter soil processes and forest productivity. We evaluated the effects of mulch addition on soil nitrogen availability at 15 fuel reduction projects in the southern Rocky Mountains and Colorado Plateau regions of Colorado. Mulching treatments removed 38Mgha−1 of standing forest biomass on average and added 2–4cm of irregular woody fragments to the O horizon. Mulching lowered maximum summer soil temperatures and increased soil moisture. The N added in mulch was equivalent to half the amount contained in untreated O horizons, and mulch had a lower N concentration and wider C:N ratio than material of similar size in untreated areas. Plant-available soil N, measured in situ with ion exchange resins was reduced under heavily-mulched experimental plots the year mulching occurred, but the effect did not persist for a second year. The nitrogen content of freshly-applied mulch increased by 9, 24 and 55kgNha−1year−1 in plots receiving 22, 49 and 105Mgha−1 of mulch material on average. In contrast, 5-year-old mulch released N regardless of amount of mulch added. Three to five years after treatment, available N was 32% higher in mulched fuel reduction treatments compared to untreated forests. Heavy mulch application has the potential to temporarily reduce soil N availability in limited areas, but as implemented in Colorado conifer forests, fuel reduction mulch treatments increase soil N availability.

Fuel treatment impacts on estimated wildfire carbon loss from forests in Montana, Oregon, California, and Arizona

Using forests to sequester carbon in response to anthropogenically induced climate change is being considered across the globe. A recent U.S. executive order mandated that all federal agencies account for sequestration and emissions of greenhouse gases, highlighting the importance of understanding how forest carbon stocks are influenced by wildfire. This paper reports the effects of the most common forest fuel reduction treatments on carbon pools composed of live and dead biomass as well as potential wildfire emissions from six different sites in four western U.S. states. Additionally, we predict the median forest product life spans and uses of materials removed during mechanical treatments. Carbon loss from modeled wildfire‐induced tree mortality was lowest in the mechanical plus prescribed fire treatments, followed by the prescribed fire‐only treatments. Wildfire emissions varied from 10–80 Mg/ha and were lowest in the prescribed fire and mechanical followed by prescribed fire treatments at most sites. Mean biomass removals per site ranged from approximately 30–60 dry Mg/ha; the median lives of products in first use varied considerably (from <10 to >50 years). Our research suggests most of the benefits of increased fire resistance can be achieved with relatively small reductions in current carbon stocks. Retaining or growing larger trees also reduced the vulnerability of carbon loss from wildfire. In addition, modeled vulnerabilities to carbon losses and median forest product life spans varied considerably across our study sites, which could be used to help prioritize treatment implementation.

The effects of fuel reduction treatments on runoff, infiltration and erosion in two shrubland areas in the north of Spain

The immediate effects of prescribed burning, shrub clearing and shrub mastication on runoff, infiltration and erosion were evaluated in two contrasting shrubland areas in northern Spain. Rainfall simulations (67mmh(-1) for 30min) were conducted immediately after fuel reduction treatments in each runoff plot. Compared to shrub mastication and shrub clearing, prescribed burning generated the lowest infiltration rate and highest runoff and erosion rates at both study sites. However, sediment yields measured immediately after treatments were low in all cases, from 0.31 to 2.22gm(-2) after shrub clearing, 0.40-1.63gm(-2) after shrub mastication and 2.30-8.11gm(-2) after prescribed burning. Slope, type of fuel reduction treatment and the depth and cover of the soil organic layer remaining after treatment were the most important variables determining runoff and erosion during the first rainfall event following treatment. In the rainfall simulation plots subjected to prescribed burning, the maximum temperatures reached at the organic layer/mineral soil interface during burning also had a significant effect on soil loss. The findings show that good fuel management prescriptions make fire hazard reduction and soil conservation compatible in cases where the remaining soil cover is about 70%.

Effects of ungulate herbivory on aspen, cottonwood, and willow development under forest fuels treatment regimes

Herbivory by domestic and wild ungulates can dramatically affect vegetation structure, composition and dynamics in nearly every terrestrial ecosystem of the world. These effects are of particular concern in forests of western North America, where intensive herbivory by native and domestic ungulates has the potential to substantially reduce or eliminate deciduous, highly palatable species of aspen (Populus tremuloides), cottonwood (Populus trichocarpa), and willow (Salix spp.). In turn, differential herbivory pressure may favor greater establishment of unpalatable conifers that serve as ladder fuels for stand-replacing fires. The resulting high fuel loads often require silvicultural fuels reductions to mitigate fire risk, which in turn may facilitate additional recruitment of deciduous species but also additional herbivory pressure. Potential interactions of ungulate herbivory with episodic disturbances of silviculture, fire, and other land uses are not well documented, but are thought to operate synergistically to affect forest dynamics. We evaluated individual and joint effects of ungulate herbivory and fuels reduction treatments in grand fir (Abies grandis) and Douglas-fir (Psuedotsuga menziezii) forests that dominate large areas of interior western North America. We applied fuels reduction treatments of mechanical thinning and prescribed fire and then evaluated the responses of aspen, cottonwood, and willow species to these treatments (N=3) versus areas of no treatment (N=3), and to exclusion from ungulate herbivory versus areas subjected to extant herbivory by free-ranging cattle (Bos taurus), elk (Cervus elaphus), and mule deer (Odocoileus hemionus). Densities of deciduous species were >4 times higher in response to fuels reduction treatments (84.4individuals/ha) compared to areas of no treatment (19.7individuals/ha). Additionally, when ungulates were excluded from fuels treated sites, the density of cottonwood was >5 times higher (122.5individuals/ha) than fuels treated sites subjected to extant herbivory (24.3individuals/ha). Similarly, densities of Populus spp. and Salix spp. were >3 times higher (211.6individuals/ha) on fuels treated sites excluded from ungulate herbivory versus fuels treated sites subjected to extant herbivory (66.1stems/ha). Deciduous species subjected to extant ungulate herbivory also were significantly lower in height, canopy surface area, and canopy volume than the same species inside the ungulate exclosures. Recruitment and long-term survival of aspen, cottonwood, and willow species in coniferous forests of interior western North America require a combination of episodic disturbances such as silviculture and fire to facilitate deciduous plant recruitment, followed by reductions in grazing pressure by domestic and wild ungulates during the time intervals between episodic disturbances to facilitate plant establishment, growth and survival.

Fuel treatment effects on tree mortality following wildfire in dry mixed conifer forests, Washington State, USA

Fuel reduction treatments are increasingly used to mitigate future wildfire severity in dry forests, but few opportunities exist to assess their effectiveness. We evaluated the influence of fuel treatment, tree size and species on tree mortality following a large wildfire event in recent thin-only, thin and prescribed burn (thin-Rx) units. Of the trees that died within the first 3 years, most died in the first year regardless of treatment. First-year mortality was much higher in control and thin-only units (65 and 52%) than in thin-Rx units (37%). Cumulative third-year mortality followed a similar trend (78 and 64% in control and thin-only units) v. 43% in thin-Rx units. Percentage crown scorch is a strong predictor of mortality and is highly dependent on fuel treatment. Across all treatments, Pinus ponderosa had a lower probability of post-fire mortality than did Pseudotsuga menziesii. Finally, the probability of beetle attack on surviving trees was highest in large-diameter trees within thin-only treatments and lowest within thin-Rx treatments. This study contributes further evidence supporting the effectiveness of thinning and prescribed burning on mitigating post-fire tree mortality. We also present evidence that a combination of thinning and prescribed burning is associated with lower incidence of post-fire bark beetle attack.

Woody Biomass Use Trends, Barriers, and Strategies: Perspectives of US Forest Service Managers

The use of woody biomass is being promoted across the United States as a means of increasing energy independence, mitigating climate change, and reducing the cost of hazardous fuels reduction treatments and forest restoration projects. The opportunities and challenges for woody biomass use on the national forest system are unique. In addition to making woody biomass usage pencil out, national forest managers must also navigate substantial public engagement and forest planning processes that add to the complexity of fostering woody biomass use opportunities on the national forest system. We report on the results of a survey of US Forest Service managers and staff members (n = 339) about the trends in, barriers to, and strategies for fostering woody biomass use on national forests and their surrounding communities. The results highlight the economic and market challenges as well as the need for a basket of policies focused on a broad array of strategies for biomass use.