Fuel Reduction Treatments Research Articles

Could biological soil crusts act as natural fire fuel breaks in the sagebrush steppe?

Could biological soil crusts act as natural fire fuel breaks in the sagebrush steppe?

Efficacy of prescribed fire as a fuel reduction treatment in the Colorado Front Range

Prescribed fires are an important management tool for reducing fuels and returning fire to the landscape. However, rarely are changes in fuels fully quantified using pre- to post-prescribed fire measurements and those studies that do exist show variable results. In the southern Rockies, little literature exists on the impacts of prescribed fires; thus we examined multiple prescribed fires in northern Colorado to understand fire effects and changes in fuel complexes. Most prominently, prescribed fires influenced litter, duff, and rotten coarse woody debris but did not influence other surface fuels. Canopy base height increased and tree density decreased, while basal area was relatively unimpacted. Season of burning impacted fire effects as substrate burn severity, bole char, and crown volume scorch were highest in summer and fall. Continued monitoring of prescribed fires is critical to understand the influence of prescribed fire on wildfires and ultimately improve prescribed fire outcomes.

Participatory multi-criteria evaluation of landscape values to inform wildfire management

Climate change is expected to increase the number of days with meteorological conditions conducive to uncontrollable wildfires. Thus, it is necessary to strengthen the capacity of wildfire-prone regions to minimize the adverse impacts of these wildfires by creating resilient landscapes. In this paper we develop a participatory multi-criteria evaluation to identify and map landscape values and prioritize areas according to these values in the Montseny Biophere Reserve (Catalonia, NE Spain). Then, we draft a wildfire management strategy to protect the areas that have been prioritized through selected fuel reduction sectors that would reduce wildfire intensity. Finally, we emphasize the added value of a participatory multi-criteria evaluation in the adaptation to and management of expected megafires. We find that the integration of landscape values through participatory multi-criteria evaluation has the potential to alter wildfire management strategies by adding fuel reduction sectors and changing their implementation order. However, the implementation of the planned fuel reduction treatments faces socioeconomic and institutional barriers that call for a deeper engagement with transdisciplinary project design and transformative science.

Composition of inorganic elements in fine particulate matter emitted during surface fire in relation to moisture content of forest floor combustibles

The moisture content of combustible material on the forest floor is constantly changing due to environmental factors, which have a direct impact on the composition and emission intensity of particulate matter released during fire. In this study, an indoor biomass combustion analysis device was used to analyze the emission characteristics of fine particulate matter (PM2.5) from combustion of herbaceous combustible materials with different moisture contents (0%, 15%, and 30%). The composition of inorganic elements in PM2.5 (Zn, K, Mg, Ca, and other 13 measurable elements) were determined by inductively coupled plasma-mass spectrometer (ICP-MS). The results showed that the PM2.5 emission factor increased significantly with the increase of moisture content of combustible materials in the range of 11.63 ± 0.55 for dry samples to 36.71 ± 1.21 g/kg for samples with 30% moisture content. The main elemental components of PM2.5 were K, Zn, Ca, Mg, and Na and K, Ca, Mg, and Na emission factors increased with the increase of moisture content of combustibles. The proportion of macronutrients in PM2.5 released by combustion of each herb increased as the moisture content increased, but the proportion of trace elements gradually decreased. There was a good correlation between elemental composition of PM2.5 and that of herbaceous combustibles. The results provide evidence that the moisture content of combustible materials has a significant effect on the emission of inorganic elements in particulate matter, and hence cautions should be exercised during fuel reduction treatments, such as early prescribed fire.

The outsized role of California’s largest wildfires in changing forest burn patterns and coarsening ecosystem scale

Although recent large wildfires in California forests are well publicized in media and scientific literature, their cumulative effects on forest structure and implications for forest resilience remain poorly understood. In this study, we evaluated spatial patterns of burn severity for 18 exceptionally large fires and compared their cumulative impacts to the hundreds of smaller fires that have burned across California forests in recent decades. We used a burn severity atlas for over 1,800 fires that burned in predominantly conifer forests between 1985 and 2020 and calculated landscape metrics to evaluate spatiotemporal patterns of unburned refugia, low-moderate-severity, and high-severity post-fire effects. Total annual area burned, mean annual fire size, and total annual core area burned at high severity all significantly increased across the study period. Exceptionally large fires (i.e., the top 1% by size) were responsible for 58% and 42% of the cumulative area burned at high and low-moderate severities, respectively, across the study period. With their larger patch sizes, our results suggest that exceptionally large fires coarsen the landscape pattern of California’s forests, reducing their fine-scale heterogeneity which supports much of their biodiversity as well as wildfire and climate resilience. Thus far, most modern post-fire management has focused on restoring forest cover and minimizing ecotype conversion in large, high-severity patches. These large fires, however, have also provided extensive areas of low-moderate severity burns where managers could leverage the wildfire’s initial “treatment” with follow-up fuel reduction treatments to help restore finer-scale forest heterogeneity and fire resilience.

Trends in forest structure restoration need over three decades with increasing wildfire activity in the interior Pacific Northwest US

Wildfire is a keystone ecological process in many forests worldwide, but fire exclusion and suppression have driven profound shifts in forest structure (e.g., increased density, canopy cover, biomass) that have contributed to increases in large, high-severity fire in many seasonally dry forests and woodlands of the western United States. Comparisons between contemporary and historic range of variability (HRV) in forest structure can quantify the amount and types of restoration that shift landscapes toward structural conditions that have historically fostered resilience to fire. However, landscapes are dynamic over time and conditions reflect the net effects of planned actions (e.g., fuel reduction treatments) and unplanned actions (e.g., wildfire). How wildfire activity may shift landscapes toward or away from the HRV and correspondingly affect the need for restoration, has not been widely tested. Here, we quantify long-term (1986–2017), and continuous (annual resolution) trends of forest restoration need and ask how wildfire activity during this period has affected restoration need trends at three nested spatial extents: across the eastern Washington (USA) ecoregion, among fire regimes within this ecoregion, and between watersheds of a frequent/low-severity fire regime that experienced contrasting amounts of wildfire. At the broadest scale, restoration need did not change substantially during the study period, with approximately 35 % of forest area in need of disturbance restoration—despite 16.6 % of the total forested area (593,000 ha) burning from 1986 to 2016. At intermediate spatial extents (among fire regimes), forests characterized by historically frequent/low-severity fire experienced the greatest decrease in disturbance restoration need following recent fire activity. Although > 50 % of forests within this fire-regime remained in need of disturbance restoration at the end of the study period, we found a strong correspondence between forested area burned and decreased restoration need in this fire regime; relationships were equivocal or non-existent in other fire regimes. At the finest spatial scale (watersheds dominated by historically frequent/low-severity fire-regime forests), we found sharp contrasts between areas that experienced high fire activity in recent years and those that did not. At this scale, recent large fires have decreased disturbance restoration need by > 25 %. Our findings suggest that recent large wildfires have reduced the amount of forest in need of restoration, but have done so modestly and primarily at local or sub-regional extents. Overall, our approach can be applied to understanding how wildfires or other disturbances contribute to affecting forest structure and management targets in other ecosystems through time and space.

Assessing the Feasibility of Meeting Target Fuel Loadings for Wildfire Reduction in North-Central British Columbia

Wildland fire has long been recognized as an important disturbance to consider in natural resource management in British Columbia (BC), Canada. Fuel reduction treatments are conducted to achieve designated fuel load targets, measured as the weight of the remaining fuel per unit area (tonnes/hectare [t/ha]). Multiple methods are available to professionals for measuring hazard abatement, but this prevents standardization of data for comparison across the province. To promote a study based in science but through an operational lens, the authors used freely available BC Government documents and guidebooks to perform the fuel measures and fuel load tallies. Thirty-two fuel plots were established in the summer of 2021 within the Burns Lake Community Forest. Field measurements were carried out following mechanical raking treatments to determine if units within the ‘severe’ fuel hazard threshold (FHT) met the target fuel load of 1–5 t/ha. Less than one-third of the plots had a fuel load within the target range. Implications of results are discussed, and several recommendations are proposed to improve the feasibility of post-harvest fuel mitigation practices, including a streamlined fuel measurement methodology and more flexible fuel load targets that would enable better comparisons of treatment feasibility across different fuel types and ecosystems within the province.

Managing nature-based solutions in fire-prone ecosystems: Competing management objectives in California forests evaluated at a landscape scale

California’s cap-and-trade compliance offset market incentivizes forest managers to maintain elevated carbon stocks. It provides these incentives without enforcing standardized fire mitigation practices despite many projects being located in fire prone regions. Here, we evaluated the difference between management actions in California forests that participated in the carbon offset market versus those that engaged with state programs to reduce wildfire risk via fuel reduction treatments. Using remotely sensed data from the California Forest Observatory and the Moderate Resolution Imaging Spectroradiometer, we compared the vertical forest structure and vegetation canopy trends on forest offsets with forests that are receiving fuel treatment. We found California forests managed for carbon under the Improved Forest Management (IFM) program by the California Air Resources Board had higher levels of biomass than forests managed for fire risk reduction as indicated by 2016 lidar-estimated fuel loads. In addition, IFM-participating forests did not reduce their fuel loads between 2016 and 2020, whereas lands receiving grants for fuel management did, indicating that on average, the IFM projects were not engaging in fuel reduction efforts. However, despite the differences in fuel management between IFM projects and active fuel treatments, we found that both types of management saw a declining trend in vegetation greenness between 2015 and 2021. While declining greenness is expected of active fuel treatments associated with vegetation removal, such a trend in the case of IFM indicates additional wildfire risk. Managing forests for long-term carbon storage and sequestration requires consideration of fire risk mitigation. Given the little evidence of fuel reduction in the first decade of IFM projects implementation we question whether the century-long duration of carbon stocks in these offsets is realistic. We recommend that policymakers reevaluate the incentives directed at carbon stock preservation or expansion to better encompass the growing wildfire risk in California.

Classification of forest fuels in selected fire-prone ecosystems of Alberta, Canada—implications for crown fire behaviour prediction and fuel management

Key messageWe used clustering to construct fuel classes from fuel inventory data based on three stand attributes relevant to crown fire behaviour: surface fuel load (SFL), canopy base height (CBH) and canopy bulk density (CBD). Resulting fuel classes explained more of the stand-to-stand variability in predicted crown fire behaviour than fuel types of the Canadian Forest Fire Behaviour Prediction (FBP) System.ContextWildfire behaviour is partly determined by stand structure and composition. Fuel characterization is essential for predicting fire behaviour and managing vegetation. Currently, categorical fuel types based on associations with major forested or open vegetated landcovers are used nationally in Canada for fire research and management applications.AimTo provide an alternative description of selected forest fuels in Alberta, Canada, using direct classification in which fuel categories are constructed from data using analytical methods.MethodsFuel inventory data for 476 stands were used to construct fuel classes with clustering. Potential crown fire behaviour was modelled for resulting fuel class clusters (FCCs) and FCCs were compared with assigned FBP System fuel types. Tree-based modelling was used to identify stand characteristics most influential on FCC membership. Fuel treatment effects on FCC and modelled crown fire behaviour were explored for the FCC most susceptible to crown fire.ResultsFour FCCs were identified: Red (low SFL, low CBH, low CBD); Green (high SFL, low-moderate CBH, low CBD); Blue (low SFL, high CBH, low-moderate CBD); and Black (low SFL, moderate CBH, high CBD). Stand density of live conifers and FBP System fuel type were the most important variables influencing FCC membership; however, FCCs did not align directly with assigned FBP System fuel types. Fuel reduction treatments in the Black FCC were effective at shifting the stand to a less flammable FCC.ConclusionFCCs explained more of the stand-to-stand variability in predicted crown fire behaviour than assigned FBP System fuel types, which suggests FCCs could be used to improve fire behaviour predictions and aid fire managers in prioritizing areas for fuel treatments. Future technological and remote sensing advances could enable mapping FCCs across large regions.

Low-Severity Wildfire Shifts Mixed Conifer Forests toward Historical Stand Structure in Guadalupe Mountains National Park, Texas, USA

Wildfire is an important natural disturbance agent, shaping mixed conifer forest structure throughout the Southwestern United States. Yet, fire exclusion caused by late 19th century livestock grazing followed by human fire suppression has altered forest structure by increasing forest density, basal area, and canopy cover in recent decades. Changes in the abundance and vertical and horizontal continuity of fuels have increased the potential for high-severity fire, which construes a major regional forest management concern. In May 2016, the Coyote Fire burned through a network of permanent forest monitoring plots in Guadalupe Mountains National Park. This study employed a repeated-measures sampling design to quantify the effects of low- to moderate-severity wildfire on forest stand structure, species composition, fuels, and tree mortality using hierarchical cluster analysis, non-metric multidimensional scaling (nMDS), and paired t-tests. The 2016 Coyote Fire reduced live tree density in small-diameter size classes, but produced minimal changes in canopy stand structure and fuel loadings, despite nearly a century of fire exclusion and pre-fire tree densities that were four-times higher they were prior to last major wildfire in the early 1900s. Small-diameter surface fuel loadings (1 h and 10 h fuels) did not significantly change after fire, although 1000 h fuels increased significantly (p < 0.05), likely from the addition of new fuel from fire-caused tree mortality. While the wildfire reduced live tree density, the nMDS analysis indicated that the wildfire did not trigger major shifts in tree species composition. However, the wildfire triggered significant decreases in seedlings and small-diameter trees (<30 cm DBH) (p < 0.05). Although the fire thinned the forest, the persistence of fuels and increases in dead small-diameter trees heighten the need for additional fuel reduction treatments to mitigate the risk of future high-severity fire under extreme fire weather. Management of low-severity fire in this forest type may provide opportunities to reduce fuels and restore more desirable stand structure to enhance forest resilience to landscape fire.

Designing forest restoration projects to optimize the application of broadcast burning

Active forest restoration programs on western US national forests face multiple challenges to meet their broad ecological goals while designing projects that generate sufficient revenue to build and maintain private forest management capacity needed to expand the scale and scope of treatments. We explored ways to design projects where admixing of treatments along gradients of dry and moist mixed conifer forest types could maximize financial viability while including substantial area where broadcast burning could be applied in conjunction with other treatments. In general, we found that restoration treatments in dry forests that included density reduction thinning and broadcast burning resulted in a net projected cost ranging from $110 to $8000 per ha. By contrast, density reduction thinning in moist mixed conifer forests on more productive microsites generated significant commercial timber volume and projected revenue that ranged from $4000 to $20,000 per ha. We used spatial optimization methods to identify potential project areas that maximized revenue while meeting constraints to treat a minimum proportion of each project with broadcast burning. Multiple project area sizes were also explored to understand the effect of restoration scale on financial outcomes. We found that optimal projects in terms of generating revenue to subsidize density reduction and broadcast burning were 810 ha and contained >50% dry forest area. Larger projects and those with a higher percentage of dry forest area resulted in lower revenue, eliminating revenue when projects reached 2700 ha. Forest restoration programs can use these methods to plan and design restoration projects that are financially viable while addressing the broadcast burn backlog in dry forests that require relatively expensive fuel reduction treatments prior to re-introducing fire.

Ten‐year ecological responses to fuel treatments within semiarid Wyoming big sagebrush ecosystems

AbstractSagebrush ecosystems of western North America are threatened by invasive annual grasses and wildfires that can remove fire‐intolerant shrubs for decades. Fuel reduction treatments are used ostensibly to aid in fire suppression, conserve wildlife habitat, and restore historical fire regimes, but long‐term ecological impacts of these treatments are not clear. In 2006, we initiated fuel reduction treatments (prescribed fire, mowing, and herbicide applications [tebuthiuron and imazapic]) in six Artemisia tridentata ssp. wyomingensis communities. We evaluated long‐term effects of these fuel treatments on: (1) magnitude and longevity of fuel reduction; (2) Greater Sage‐grouse habitat characteristics; and (3) ecological resilience and resistance to invasive annual grasses. Responses were analyzed using repeated‐measures linear mixed models. Response variables included plant biomass, cover, density and height, distances between perennial plants, and exposed soil cover. Prescribed fire produced the greatest reduction in woody fuel over time. Mowing initially reduced woody biomass, which recovered by year 10. Tebuthiuron did not significantly reduce woody biomass compared to controls. All woody fuel treatments reduced sagebrush cover to below 15% (recommended minimum for Greater Sage‐grouse habitat), but only prescribed fire reduced cover to below controls. Median mowed sagebrush height remained above the recommended 30 cm. Cheatgrass (Bromus tectorum) cover increased to above the recommended maximum of 10% across all treatments and controls. Ecological resilience to woody fuel treatments was lowest with fire and greatest with mowing. Low resilience over the 10 posttreatment years was identified by: (1) poor perennial plant recovery posttreatment with sustained reductions in cover and density of some perennial plant species; (2) sustained reductions in lichen and moss cover; and (3) increases in cheatgrass cover. Although 10 years is insufficient to conclusively describe final ecological responses to fuel treatments, mowing woody fuels has the greatest potential to reduce woody fuel, minimize shrub mortality and soil disturbance, maintain lichens and mosses, and minimize long‐term negative impacts on Greater Sage‐grouse habitat. However, maintaining ecological resilience and resistance to invasion may be threatened by increases in cheatgrass cover, which are occurring regionally.

Fuel reduction treatments reduce modeled fire intensity in the sagebrush steppe

AbstractIncreased fire size and frequency coupled with annual grass invasion pose major challenges to sagebrush (Artemisia spp.) ecosystem conservation, which is currently focused on protecting sagebrush community composition and structure. A common strategy for mitigating potential fire is to use fuel treatments that alter the structure and amount of burnable material, thus reducing fire behavior and creating access points for fire suppression resources. While there is some recent information on the impacts of fuel treatments on ecological communities, we have little information on fuel treatment effectiveness at modifying fire behavior in sagebrush ecosystems. We present 10 years of data on fuel accumulation and the resultant modeled fire behavior in prescribed fire, mowed, herbicide (tebuthiuron or imazapic), and untreated control plots in the Sagebrush Treatment Evaluation Project (SageSTEP) network in the Great Basin, USA. Fuel data (i.e., aboveground burnable live and dead biomass) were collected in each treatment plot at Years 0 (pretreatment), 1, 2, 3, 6, and 10 posttreatment. We used the Fuel and Fire Tool fire behavior modeling program to test whether treatments impacted potential fire behavior. Prescribed fire initially removed 49% of the total fuel load and 75% of shrubs, and fuel loads remained reduced through Year 10. Mowing shifted fuels from the shrub canopy to the ground surface but did not change the total fuel amount. Prescribed fire and mowing increased herbaceous fuel by the second posttreatment year and that trend persisted through Year 10. Tebuthiuron treatments were ineffective at altering fuel loads. Imazapic suppressed herbaceous vegetation by 30% in Years 2 and 3 following treatment. The modified fuel beds in fire and mow treatments resulted in modeled flame lengths that were significantly lower than untreated control plots for the duration of the study, with shorter term reductions in reaction intensity and rate of spread. Understanding fuel treatment effectiveness will allow natural resource managers to evaluate trade‐offs between protecting wildlife habitat and reducing the potential for high‐intensity wildfire.

LiDAR as a Tool for Assessing Change in Vertical Fuel Continuity Following Restoration

The need for fuel reduction treatments and the restoration of ecosystem resilience has become widespread in forest management given fuel accumulation across many forested landscapes and a growing risk of high-intensity wildfire. However, there has been little research on methods of assessing the effectiveness of those treatments at landscape scales. Most research has involved small-scale opportunistic case studies focused on incidents where wildland fires encountered recent restoration projects. It is important to assess whether restoration practices are successful at a landscape scale so improvements may be made as treatments are expanded and their individual effectiveness ages. This study used LiDAR acquisitions taken before and after a large-scale forest restoration project in the Malheur National Forest in eastern Oregon to broadly assess changes in fuel structure. The results showed some areas where treatments appeared effective, and other areas where treatments appeared less effective. While some aspects could be modified to improve accuracy, the methods investigated in this study offer forest managers a new option for evaluating the effectiveness of fuel reduction treatments in reducing potential damage due to wildland fire.

Prescribed fire and other fuel-reduction treatments alter ground spider assemblages in a Southern Appalachian hardwood forest

Prescribed burns and understory thinnings are forest management practices aimed at reducing fuel loads to lessen wildfire threat in the Southern Appalachians, USA. Spiders play a critical role in forest ecosystems by controlling insect populations and providing an important food source for vertebrates. We used pitfall and colored pan traps to investigate how abundance, species richness, and diversity of spiders differed among three fuel reduction treatments administered repeatedly over a 15-year period and untreated controls. Additionally, we examined how spiders responded to one round (before and after) of fuel reduction treatments. We established treatments within the 15-year period as follows: mechanical understory removal (twice; M), prescribed burning (four times; B), mechanical understory removal followed one year later by high-severity prescribed burns and three subsequent burns (MB), and untreated controls (C). Our study period (2014–2016) occurred after multiple prescribed burns and two rounds of mechanical understory removal had occurred. Salticidae and Lycosidae were the two most commonly collected spider families in Southern Appalachian hardwood forests. Generally, we found increased spider abundances within all fuel-reduction treatments compared to controls. Individual spider families and species showed variable responses to treatments, but abundance of several spider families was greater in one or more fuel-reduction treatments than in controls. Additionally, abundance of several spider families and hunting/web building guilds (webs built for hunting purposes or defense) exhibited yearly differences to the last round of fuel-reduction treatments. Overall, our results suggest that changes in the overstory and understory of a forest are important drivers of regional spider abundance and assemblages, and forest management practices that modify forest structure can dramatically alter spider abundance and richness, usually in a positive manner.

Decadal Impacts of Wildfire Fuel Reduction Treatments on Ecosystem Structure and Fire Behavior in Alaskan Boreal Forests

Decadal Impacts of Wildfire Fuel Reduction Treatments on Ecosystem Structure and Fire Behavior in Alaskan Boreal Forests

Water quality and forest restoration in the Lake Tahoe basin: impacts of future management options

Land managers in the Lake Tahoe basin are considering increasing the use of prescribed fire and forest thinning to restore conditions that will be more resilient to wildfires. However, such restorative treatments also constitute disturbances that could increase sediment and nutrient loads. We examined whether the water-quality impacts from future treatments are likely to be lower compared to the potential impacts from future wildfires under various climate change scenarios. We applied an online interface for the Water Erosion Prediction Project (WEPP) model in combination with a landscape change model (LANDIS-II) to evaluate the effects of different combinations of thinning and prescribed burning on fine sediment (< 2 mm), very fine sediment (< 16 µm), and phosphorus over time. First, we generated results based on historic weather data for soil disturbance conditions, including: an undisturbed baseline, a uniform thinning treatment; a uniform prescribed fire treatment; and uniform low, moderate, and high wildfire burn severity. Residual ground cover declined in that order, and expected loads of sediment and phosphorus increased. We then combined the estimated loads from hillslopes with projected management-disturbance regimes across each decade of the next century. We found that expected sediment and phosphorus loads were lower under the scenario that emphasized thinning, whereas scenarios that increased prescribed burning resulted in loads that were comparable to scenarios that involved less treatment. These results reflect the finding from the WEPP analysis that prescribed burning is expected to reduce ground cover more than is thinning. Our analysis supports efforts to increase fuel reduction treatments to mitigate future wildfires, but it also suggests that preventative treatments may not avoid a long-term decline in water quality as wildfires increase with climate change.

Effect of recent fuel reduction treatments on wildfire severity in southeast Australian Eucalyptus sieberi forests

Climate change is increasing the area of seasonally dry forests burnt by wildfire in many parts of the world, compelling a revision of management strategies to reduce risk and improve the resilience of forest ecosystems. While prescribed burning is a common strategy used to reduce bushfire risk, mechanical thinning has not been as widely applied in Australia’s temperate forests in comparison with the USA and Europe. In this study we report results from a prescribed burning and mechanical thinning experiment in a 37-year-old naturally regenerated Eucalyptus open forest that was burnt through by wildfire in January 2020, providing an opportunity to determine how pre-wildfire fuel status and burning and thinning treatments influenced wildfire severity.Fuel hazard assessments in the experimental forest, made prior to the wildfire, indicated that untreated forest, and thinned forest, had very high to extreme fuel hazard scores, while forests treated with prescribed burning, or with thinning plus burning, had low fuel hazard scores. These fuel hazard scores explained more than 70% of the variation in wildfire severity, indicating that the fire was largely fuel driven and responsive to fuel reduction measures.Forest areas treated with thinning only recorded extreme fuel hazard, largely due to the increase in forest floor residues, which were ignited by the wildfire resulting in a high fire severity ranking. Forest areas treated with thinning and prescribed burning, or with high intensity prescribed burning, did not ignite from the advancing front of the wildfire, clearly demonstrating the effectiveness of fuel reduction management under low to moderate forest fire danger weather.Fuel hazard reduction benefits extend for at least three years after the application of fuel modification treatments in Eucalyptus sieberi forests. The results from this forest experiment demonstrate that the active management of fuels, including thinning with prescribed burning, can reduce wildfire risk and fire severity.

Prescribed fire limits wildfire severity without altering ecological importance for birds

BackgroundFire suppression and anthropogenic land use have increased severity of wildfire in western U.S. dry conifer forests. Managers use fuels reduction methods (e.g., prescribed fire) to limit high-severity wildfire and restore ecological function to these fire-adapted forests. Many avian species that evolved in these forests, however, are adapted to conditions created by high-severity wildfire. To fully understand the ecological implications of fuels reduction treatments, we need to understand direct treatment effects and how treatments modulate subsequent wildfire effects on natural communities. We studied bird population and community patterns over nine years at six study units, including unburned (2002–2003), after prescribed fire (2004–2007), and after wildfire (2008–2010). We used a before-after, control-impact (BACI) approach to analyze shifts in species occupancy and richness in treated units following prescribed fire and again in relation to burn severity following wildfire.ResultsWe found examples of both positive and negative effects of wildfire and prescribed fire on bird species occupancy depending on and largely consistent with their life history traits; several woodpecker species, secondary cavity-nesting species, aerial insectivores, and understory species exhibited positive effects, whereas open cup canopy-nesting species and foliage- or bark-gleaning insectivores exhibited negative effects. Wildfire affected more species more consistently through time than did prescribed fire. Wildfire burned units initially treated with prescribed fire less severely than untreated units, but the slopes of wildfire effects on species occupancy were similar regardless of prior prescribed fire treatment.ConclusionsOur results suggest managers can employ prescribed fire to reduce wildfire severity without necessarily altering the ecological importance of wildfire to birds (i.e., the identity of species exhibiting negative versus positive responses). Additional study of the ecological implications of various fuels reduction practices, representing a range of intensities and fire regimes, would further inform forest management that includes biodiversity objectives.

Effects of fuel reduction treatments on the sporocarp production and richness of a Quercus/Cistus mixed system

Wildfire is a recurrent factor that shapes and influences Mediterranean ecosystems where mixed oak (Quercus) forests with a rockrose (Cistus) understory are broadly represented. These ecosystems are also associated with large and diverse fungal communities. These fungal communities play essential ecological roles for the survival of vascular plant, such as the mineral and water uptaking or resistance against pathogens carried out by mycorrhizal fungi, as the saprotrophic fungi are a key factor for the recycling of the dead matter. In addition, edible fungi, such as Boletus edulis, provide a source of income for the nearby rural population. Fuel reduction treatments are applied to reduce the risk of wildfire; however, their potential impact on fungal communities is unclear. Thus, the aim of this work was to investigate the effect of different fuel reduction treatments on fungi associated with Quercus and Cistus. This aim is accompanied by the management-driven objective to obtain data from fuel reduction treatments that will enable managers to find solutions with a balanced approach to maintaining productive areas of edible mushroom production while reducing fire risks across the landscape. Sporocarps were sampled over a five-year period in stands dominated by mature or coppiced Quercus pyrenaica and accompanied by Cistus ladanifer understory. These stands had been subjected to different fuel reduction treatment levels involving moderate- or high-intensity thinning, for Q. pyrenaica, or clearing, for C. ladanifer. The goal was to determine sporocarp production, species richness, and taxonomic composition. Sporocarp production and fungal richness were drastically affected by the fuel reduction treatments but only when C. ladanifer is included in the treatment. Taxa composition was strongly correlated with the treatments applied to the rockrose understory. This was probably due to the large range of associated ectomycorrhizal fungi of C. ladanifer and their high capacity to recolonize an area after disturbances. Based on our results, we conclude that the implementation of moderate-/high-intensity fuel reduction treatments is compatible with the conservation of the fungal community present in these systems. In addition, the creation of a multi-stage mosaic of stands through mechanical management could enable fire prevention to be managed in an effective way while maintaining fungal diversity and sporocarp production, favoring the use of non-wood resources in rural areas and conserving a healthier forest ecosystem.