Fuel Reduction Treatments Research Articles

Canopy Fuel Load Mapping of Mediterranean Pine Sites Based on Individual Tree-Crown Delineation

This study presents an individual tree-crown-based approach for canopy fuel load estimation and mapping in two Mediterranean pine stands. Based on destructive sampling, an allometric equation was developed for the estimation of crown fuel weight considering only pine crown width, a tree characteristic that can be estimated from passive imagery. Two high resolution images were used originally for discriminating Aleppo and Calabrian pines crown regions through a geographic object based image analysis approach. Subsequently, the crown region images were segmented using a watershed segmentation algorithm and crown width was extracted. The overall accuracy of the tree crown isolation expressed through a perfect match between the reference and the delineated crowns was 34.00% for the Kassandra site and 48.11% for the Thessaloniki site, while the coefficient of determination between the ground measured and the satellite extracted crown width was 0.5. Canopy fuel load values estimated in the current study presented mean values from 1.29 ± 0.6 to 1.65 ± 0.7 kg/m2 similar to other conifers worldwide. Despite the modest accuracies attained in this first study of individual tree crown fuel load mapping, the combination of the allometric equations with satellite-based extracted crown width information, can contribute to the spatially explicit mapping of canopy fuel load in Mediterranean areas. These maps can be used among others in fire behavior prediction, in fuel reduction treatments prioritization and during active fire suppression.

Immediate and short-term response of understory fuels following mechanical mastication in a pine flatwoods site of Florida, USA

Mechanical fuel hazard reduction treatments are widely implemented in fire-prone ecosystems, but research evaluating their effects on fuel dynamics has focused only on woody-dominated post-treatment fuels. In the southeastern US, one of the most fire-prone regions of the world, mechanical fuels reduction is being increasingly used, yet the resulting fuelbeds have yet to be fully characterized for their fire risk. In order to broaden our understanding of the longevity and effectiveness of these treatments, mechanical mastication (“mowing”) was examined in a common pine ecosystem of the southeastern US Coastal Plain, where the post-mastication fuel environment was dominated by non-woody fuels. Fuel dynamics differed between recently burned mature stands, mature stands that had not burned for several years, and younger pine plantations. Foliar litter dominated (46–69%) the 17.1–23.1Mgha−1 of post-mastication surface fuels across these ecosystems, where pre-treatment understories were dominated by palmetto and gallberry shrubs. Although surface fuels compacted over time, the shrub layer recovered quickly, contributing to the result that stand-alone mechanical treatments did not reduce overall fuel loads. Increases in surface fuels followed by rapid shrub recovery may indicate short-term treatment efficacy, with narrow windows of opportunity for post-treatment fuel reduction burns. The fuelbed characteristics and fuel dynamics observed in these treated sites broaden our understanding of mechanical fuels reduction treatments in general, and provide the critical data for fuel model development.

Soil development in vegetation patches of Pinus ponderosa forests: Interface with restoration thinning and carbon storage

Frequent-fire conifer forests in western North America are undergoing restoration and fuel-reduction treatments to reduce chance of severe crown fire and re-balance tree and understory plant biomass. A central decision in these treatments remains where to retain trees within sites during tree thinning. To help inform thinning prescriptions by identifying patterns of soil development, we sampled and classified 48 soil pedons among three vegetation patch types (grassy openings, openings invaded by post-settlement trees <age 130years, and pre-settlement tree patches) at 8 sites in northern Arizona Pinus ponderosa forests. We found that 69% of pedons in openings were classified as Mollisols (a soil order associated with grasslands), whereas 75% of pedons in pre-settlement tree patches were Alfisols (a forest soil order). Soil differences among patches primarily related to soil morphology and development of epipedons, not necessarily reflected in analyses of properties (e.g., horizon thickness, organic C) of horizons. Turnover in soil orders occurs on a scale of meters to tens of meters within sites on this landscape, corresponding with distribution of vegetation patch types. Owing to long time periods required for these soil patterns to develop, results provide additional support for an idea that locations of tree and herbaceous patches were stable for long time periods (centuries to millennia). Results suggest that soil development patterns warrant consideration when choosing spatial locations of ‘leave’ trees during forest thinning.

Toward full economic valuation of forest fuels-reduction treatments

Our goal was to move toward full economic valuation of fuels-reduction treatments applied to ponderosa pine (Pinus ponderosa) forests. For each of five fuels-reduction projects in northern Arizona, we calculated the economic value of carbon storage and carbon releases over one century produced by two fuels-reduction treatments of thinning following by prescribed burning every one (Rx10) or two (Rx20) decades and for no treatment followed by intense wildfire once in the first 50 years (HF50) or once in the first 100 years (HF100). Our estimates include two uses of harvested wood, the current use as pallets, and multiproduct use as paper, pallets, and construction materials. Additionally, we included the economic value of damage and loss from wildfire. Results indicate that treatments increase carbon stock in live trees over time; however, the inclusion of carbon emissions from treatments reduces net carbon storage and thereby carbon credits and revenue. The economic valuation shows that the highest net benefit of $5029.74 ha−1 occurs for the Rx20 treatment with the HF50 baseline and the high estimated treatment benefits of avoided losses, regional economic benefits, and community value of fire risk reduction. The lowest net benefit of −$3458.02 ha−1 occurs for the Rx10 treatment with the HF100 baseline and the low estimated treatment benefits. We conclude that current nonmarket values such as avoided wildfire damage should be included with values of traditional wood products and emerging values of carbon storage to more appropriately estimate long-term benefits and costs of forest fuels-reduction treatments.

Effects of fuel reduction treatments on movement and habitat use of American toads in a southern Appalachian hardwood forest

Prescribed fire is a commonly used management technique for maintaining fire-adapted ecosystems, yet empirical data regarding its effects on amphibians are limited and contradictory. Anurans (frogs and toads) may be the amphibian taxa most negatively affected by fire due to their extensive use of the forest floor; however, short-term abundance studies suggest that terrestrial toads (e.g., Anaxyrus [Bufo] americanus) may benefit from fire-based ecosystem management. We used radio-telemetry to examine the effects of prescribed fire on movements, home range characteristics, mortality, and habitat selection of A. americanus in a southern Appalachian upland hardwood forest. We tracked 26 adult A. americanus between 27 January and 30 May 2012. Toads exhibited high non-breeding site fidelity and traveled 993.5m (±265.9m) mean (±SD) route distance between the breeding ponds and the last recorded location within their summer habitat. We found no evidence of direct mortality of A. americanus from a prescribed fire that occurred on 13 February 2012. Forward stepwise discriminant analysis (DA) revealed that the availability of coarse woody debris (CWD) was a significant discriminator between microhabitats used (i.e., location plots) and random plots (Wilk’s lambda=0.9852, F1, 661=9.9414, p=0.002). Forward stepwise DA revealed that burned and unburned location plots were significantly different (Wilk’s lambda=0.2713, F1, 221=593.6863, p<0.001) based on the percent of plot ground cover comprised of charred material (%char). When %char was excluded from the analysis due to its short-term nature, the percent of plot ground cover comprised of deciduous leaves, a cover item commonly used by toads in unburned locations, was the variable with the most discriminatory power (Wilk’s lambda=0.4243, F1, 221=299.8741, p<0.001). Toads maintained greater distances from CWD in the unburned (mean±SD=119.50±109.64cm) than in the burned locations (mean±SD=86.05±104.81cm; χ12=9.7055, p=0.002). Our results indicate that prescribed fire as implemented in this study did not cause direct mortality, nor did it appear to inhibit migratory movements of adult A. americanus. However, fire reduced the diversity and availability of refugia, especially deciduous leaves, though the availability of alternative cover objects (e.g., CWD) in burned treatments allowed toads to inhabit those areas, suggesting the importance of noncombustible or semi-permanent refugia for A. americanus in fire-managed forests.

Fuel reduction at a Spanish heathland by prescribed fire and mechanical shredding: Effects on seedling emergence

Traditional heathland burning has declined in Spain, leading to fuel accumulation and fuel reduction treatments have become common for severe wildfire hazard reduction. These methods need to maintain the botanical composition of those shrub communities. Prescribed fire has been widely used in the past, but we need to compare mechanical fuel reduction with prescribed fire because it is easier and safer to carry out in a wide range of weather conditions. This information could be particularly useful in flammable ecosystems all over the world where traditional anthropogenic burning has declined. In this study, we compared the effects of prescribed burning and mechanical shredding on the seedling emergence and its relation to the mature vegetation in a fire-prone heathland dominated by Erica australis L. and Pterospartum tridentatum (L.) Willk., in Galicia (NW Spain). We combined a greenhouse experiment with periodic field inventories of seedling emergence.In the greenhouse study, the seedling emergence was significantly higher in the soil samples after burning (383 seedlings m−2) than in samples before burning (242 seedlings m−2). In contrast, there was no significant difference in seedling density before and after mechanical shredding (243 compared with 261 seedlings m−2). Also, the number of seedlings that emerged after burning was significantly higher than that emerged after mechanical shredding. The maximum temperatures at the soil organic layer surface during burning were significantly and positively related to the density of Halimium lasianthum ssp. alyssoides and P. tridentatum seedlings.In the field study, the observed seedling density was very low both after prescribed burning and mechanical shredding. There was a high degree of similarity between emerged seedlings and mature vegetation in both the treated and in the untreated soils, which was probably a consequence of the dominance of resprouting species.Some consequences for the management of these shrublands are also discussed.

Competition, size and age affect tree growth response to fuel reduction treatments in mixed-oak forests of Ohio

Prescribed fire and thinning treatments are increasingly used to mitigate potential wildfire hazards, alter stand structure and restore forest functions. In this study, the effects of competition, tree size and age on tree growth following prescribed fire and thinning treatments were examined to better understand the consequences of these management tools on forest systems. Tree-ring data from 348 trees, comprising five species (white oak, black oak, chestnut oak, hickories, and yellow-poplar) were analyzed following standard dendrochronological protocols. Data were collected from 80 0.1-ha plots in two study sites, each with four treatment units (control, thin-only, burn-only, thin +burn) in mixed-oak forests of Ohio. A neighborhood analysis was used to assess the competitive status of each sampled tree. Basal area increment (BAI) and tree size were positively related, with the strongest correlation found in the burn-only treatment. Age was negatively related to BAI, though weakly. Competition was inversely correlated with BAI, with trees from the thin-only unit showing the strongest correlation. BAI was greater for larger trees when competition was low and declined at a steeper rate as competition increased. Smaller trees grew less in general but decreases in BAI were not as steep as competition increased. Overall, tree size, age, and competition explained ∼40% of total variance in BAI across all species. Values for individual tree species ranged from 30% to 57%, indicating considerable variation in the responses of species to these factors. Yellow-poplar exhibited greater sensitivity to competition than the other species analyzed. Altogether, competition was more important than size and age for tree growth in these managed stands. Variation in competitive status of trees within treatments supports the view that prescribed fire and thinning influence forest growth by creating heterogeneity among stands, and thus demonstrates the need for individual tree-based analysis to fully understand prescribed fire and thinning impacts on forest ecosystems.

Assessing Watershed-Wildfire Risks on National Forest System Lands in the Rocky Mountain Region of the United States

Wildfires can cause significant negative impacts to water quality with resultant consequences for the environment and human health and safety, as well as incurring substantial rehabilitation and water treatment costs. In this paper we will illustrate how state-of-the-art wildfire simulation modeling and geospatial risk assessment methods can be brought to bear to identify and prioritize at-risk watersheds for risk mitigation treatments, in both pre-fire and post-fire planning contexts. Risk assessment results can be particularly useful for prioritizing management of hazardous fuels to lessen the severity and likely impacts of future wildfires, where budgetary and other constraints limit the amount of area that can be treated. Specifically we generate spatially resolved estimates of wildfire likelihood and intensity, and couple that information with spatial data on watershed location and watershed erosion potential to quantify watershed exposure and risk. For a case study location we focus on National Forest System lands in the Rocky Mountain Region of the United States. The Region houses numerous watersheds that are critically important to drinking water supplies and that have been impacted or threatened by large wildfires in recent years. Assessment results are the culmination of a broader multi-year science-management partnership intended to have direct bearing on wildfire management decision processes in the Region. Our results suggest substantial variation in the exposure of and likely effects to highly valued watersheds throughout the Region, which carry significant implications for prioritization. In particular we identified the San Juan National Forest as having the highest concentration of at-risk highly valued watersheds, as well as the greatest amount of risk that can be mitigated via hazardous fuel reduction treatments. To conclude we describe future opportunities and challenges for management of wildfire-watershed interactions.

Vegetation Response to Western Juniper Slash Treatments

The expansion of piñon-juniper woodlands the past 100years in the western United States has resulted in large scale efforts to kill trees and recover sagebrush steppe rangelands. It is important to evaluate vegetation recovery following woodland control to develop best management practices. In this study, we compared two fuel reduction treatments and a cut-and-leave (CUT) treatment used to control western juniper (Juniperus occidentalis spp. occidentalis Hook.) of the northwestern United States. Treatments were; CUT, cut-and-broadcast burn (BURN), and cut-pile-and-burn the pile (PILE). A randomized complete block design was used with five replicates of each treatment located in a curl leaf mahogany (Cercocarpus ledifolius Nutt. ex Torr. & A. Gray)/mountain big sagebrush (Artemisia tridentata Nutt. spp. vaseyana (Rydb.) Beetle)/Idaho fescue (Festuca idahoensis Elmer) association. In 2010, 4years after tree control the cover of perennial grasses (PG) [Sandberg's bluegrass (Poa secunda J. Pres) and large bunchgrasses] were about 4 and 5% less, respectively, in the BURN (7.1±0.6%) than the PILE (11.4±2.3%) and CUT (12.4±1.7%) treatments (P<0.0015). In 2010, cover of invasive cheatgrass (Bromus tectorum L.) was greater in the BURN (6.3±1.0%) and was 50 and 100% greater than PILE and CUT treatments, respectively. However, the increase in perennial bunchgrass density and cover, despite cheatgrass in the BURN treatment, mean it unlikely that cheatgrass will persist as a major understory component. In the CUT treatment mahogany cover increased 12.5% and density increased in from 172±25 to 404±123trees/ha. Burning, killed most or all of the adult mahogany, and mahogany recovery consisted of 100 and 67% seedlings in the PILE and BURN treatments, respectively. After treatment, juniper presence from untreated small trees (<1m tall; PILE and CUT treatments) and seedling emergence (all treatments) represented 25-33% of pre-treatment tree density. To maintain recovery of herbaceous, shrub, and mahogany species additional control of reestablished juniper will be necessary.

Simulating avian species and foraging group responses to fuel reduction treatments in coniferous forests

Over a century of fire suppression activities have altered the structure and composition of mixed conifer forests throughout the western United States. In the absence of fire, fuels have accumulated in these forests causing concerns over the potential for catastrophic wildfires. Fuel reduction treatments are being used on federal and state lands to reduce the threat of wildfire by mechanically removing biomass. Although these treatments result in a reduction in fire hazard, their impact on wildlife is less clear. We use a multi-species occupancy modeling approach to build habitat-suitability models for 46 upland forest birds found in the Lake Tahoe Basin in the Sierra Nevada based on forest structure and abiotic variables. Using a Bayesian hierarchical framework, we predict species-specific and community-level responses to changes in forest structure and make inferences about responses of important avian foraging guilds. Disparities within and among foraging group responses to canopy cover, tree size and shrub cover emphasized the complexities in managing forests to meet biodiversity goals. Based on our species-specific model results, we predicted changes in species richness and community similarity under forest prescriptions representing three management practices: no active management, a typical fuel reduction treatment that emphasizes spacing between trees, and a thinning prescription that creates structural heterogeneity. Simulated changes to structural components of the forest analogous to management practices to reduce fuel loads clearly affected foraging groups differentially despite variability in responses within guilds. Although species richness was predicted to decrease slightly under both simulated fuels reduction treatments, the prescription that incorporated structural heterogeneity retained marginally higher species richness. The composition of communities supported by different management alternatives was influenced by urbanization and management practice, emphasizing the importance of creating heterogeneity at the landscape scale.

Projecting Impacts of Fire Management on a Biodiversity Indicator in the Sierra Nevada and Cascades, USA: The Black-Backed Woodpecker

In the Sierra Nevada and southern Cascade ranges of California and Oregon, a genetically distinct population of the black-backed woodpecker has become rare due, in part, to fire suppression. This species is considered an indicator species for its primary habitat: early successional burned forests with an abundance of standing dead trees. Fuel reduction treatments such as post-fire logging, and forest thinning prior to fire (by creating insufficient snag density and enhancing fire suppression), may further reduce this habitat, but this has not been quantified. Our goal here is to address this information gap. Specifically, we first quantified the impacts of fire suppression and fuel treatments on primary habitat for the black-backed woodpecker. Our objective in this paper was to address how fire management affects the primary habitat of the black-back woodpecker and associated species in the Sierra Nevada and Cascades. We found that fire suppression was associated with a dramatic reduction in stand-initiation processes, a proxy for tree mortality, since the 1930s on public lands. We additionally found that thinning and post-fire clear cutting each exacerbated the effects of fire suppression by reducing primary habitat at an approximately 1:1 ratio with area treated. A scenario based on thinning 20 percent of mature forests over a 20 year period, and post-fire logging in 33% of potential habitat created by fire, reduced the amount of primary habitat after 27 years to 30%of the amount that would occur without these treatments, assuming that modeled effects of the fuel treatments in controlling fire may be realized. Our results indicate that conserving the distinct population of black-backed woodpeckers in the southern Cascades and Sierra Nevada and the biodiversity for which they are an indicator will require that more unthinned area be burned by wildfires and protected after fire as critical habitat. Our results also show that restoration of fire to an extent closer to historical levels would considerably increase black-backed woodpecker habitat and have minimal tradeoff with conservation of mature forest.

Bird response to fire severity and repeated burning in upland hardwood forest

Prescribed burning is a common management tool for upland hardwood forests, with wildlife habitat improvement an often cited goal. Fire management for wildlife conservation requires understanding how species respond to burning at different frequencies, severities, and over time. In an earlier study, we experimentally assessed how breeding bird communities and species responded to fuel reduction treatments by mechanical understory reduction, low-severity prescribed fires, or mechanical understory reduction followed a year later by high-severity prescribed fires in upland hardwood forest. Here, we assess longer-term response to the initial mechanical treatment (M), and a second low-intensity burn in twice burned (B2) and mechanical+twice burned (MB2) treatments and controls (C). Initial (2003) higher dead fuel loadings and consequently high-severity fires in MB2 created open-canopy structure with abundant snags, resulting in much higher species richness and density of breeding birds compared to other treatments. Relative bird density and richness remained much higher in MB2 after a second burn, but few changes were evident that were not already apparent after one burn. The initial (2003) burn in B2 had cooler, low-severity fires that killed few trees. Delayed tree mortality occurred in both burn treatments after one burn, and continued in both after a second low-intensity burn. In B2, this resulted in gradual development of a “perforated,” patchy canopy structure with more snags. Abundance of total birds and most species in B2 was similar to C, but several additional species associated with open-forest conditions occurred at low levels, increasing richness in B2. In both burn treatments, burning temporarily reduced habitat suitability for ground-nesting birds. Bird communities in M were similar to C, as shrubs recovered rapidly. Results indicate that one or two relatively low-intensity burns with patches of hotter fire may result in gradual, subtle changes to canopy cover and structure that may slightly increase bird species richness over time. In contrast, a single high-intensity, high severity fire can create young forest conditions and a heterogeneous canopy structure that can be maintained by repeated burning and increase breeding bird relative abundance and richness by attracting disturbance-adapted species while retaining most other forest species.

Effects of fuel reduction treatments on a gorse shrubland soil seed bank in the north of Spain: Comparing mastication and prescribed burning

Fuel reduction treatments are commonly used to decrease the risk of severe wildfire in shrubland areas in the North of Spain. Information about the associated environmental effects is required to help forest managers select the most appropriate treatment. Although the soil seed bank plays an important role in post-disturbance recovery and resilience of frequently disturbed shrubland communities, little is known about how it is affected by fuel reduction treatments. We carried out a combined greenhouse and field study to evaluate the effects of two fuel reduction methods (prescribed burning and mastication) on the size and composition of the soil seed bank in a fire-prone gorse shrubland area in northern Spain. Total seedling density, species richness and similarity index were the variables analyzed. We also determine the effect of the depth of the soil organic cover remaining after mastication on the soil seed bank composition.In the greenhouse experiment, significantly more seedlings emerged from the samples of the soil seed bank obtained after burning (810.6seedlingsm−2) than in those obtained before burning (608.3seedlingsm−2) and after mastication (610.1seedlingsm−2). This contrasted with the lack of differences observed before and after mastication. Species richness in the soil seed bank was not altered by either prescribed burning or mastication. The observed high degree of similarity between soil seed bank and above-ground vegetation in both pre and post-treated soils was attributed to the dominance of resprouting species.Post-burning seedling density was not significantly related to any of the soil thermal regime parameters during burning. The depth of the soil organic cover after mastication apparently did not affect the composition of the soil seed bank.The field study revealed a low rate of seed germination of all species, which along with the rapid recovery of cover by the resprouting woody species in the community, suggests that the soil seed bank makes little contribution to the recovery of shrubland communities after fuel reduction treatments.There was little opportunity to enhance vegetation recovery through the soil seed bank after prescribed burning and mastication. Mastication seems to be a more conservative technique although low intensity burnings as those conducted in the present study did not stimulate seed germination nor reduce seed bank size. In summary, prescribed burning and mastication can be considered feasible techniques for fuel management in these shubland areas.

Carbon Credit Possibilities and Economic Implications of Fuel Reduction Treatments

We determined the difference in carbon (C) stocks and C emissions between treated and untreated ponderosa pine stands over 100 years on the Apache and Sitgreaves National Forests, Arizona, USA, under assumed treatment scenarios, wildfire frequency, and annual percentage of area burned. Compared with the no-action scenario, total C stocks (live and dead biomass) were lower in the treatment scenarios because of timber removals from thinnings, whereas aboveground live C stocks were higher in the treatment scenarios. When total C stocks were used as the baseline, net present values (NPVs) of treatments were in the range of −$759.42 and −$722.58 ha−1 if timber and reduced requirement for C in a buffer pool were assumed to be creditable, and NPVs increased significantly if C in wood products was also eligible for C credit. When aboveground live C stocks were chosen as the baseline, NPVs ranged from −$759.42 to $2,700.44 ha−1 with revenues from timber stumpage value, reduced buffer pool, and/or C in wood products. C emissions from simulated wildfires were lower in the two treatment scenarios than in the no-action scenario. The heavier thinning treatment resulted in lower C emissions from wildfires than with the lighter thinning treatment.

Forest wildfire, fuel reduction treatments, and landscape carbon stocks: A sensitivity analysis

Fuel reduction treatments prescribed in fire-suppressed forests of western North America pose an apparent paradox with respect to terrestrial carbon management. Such treatments have the immediate effect of reducing forest carbon stocks but likely reduce future carbon losses through the combustion and mortality caused by high-severity wildfires. Assessing the long-term impact of fuel treatment on the carbon balance of fire-prone forests has been difficult because of uncertainties regarding treatment and wildfire impacts on any given landscape. In this study we attempt to remove some of the confusion surrounding this subject by performing a sensitivity analysis wherein long-term, landscape-wide carbon stocks are simulated under a wide range of treatment efficacy, treatment lifespan, fire impacts, forest recovery rates, forest decay rates, and the longevity of wood products. Our results indicate a surprising insensitivity of long-term carbon stocks to both management and biological variables. After 80 years, a 1600% change in either forest growth or decomposition resulted in only a 40% change in total system carbon, and a 1600% change in either treatment application rate or efficacy in arresting fire spread resulted in only a 10% change in total system carbon. This insensitivity of long-term carbon stocks is due in part by the infrequency of treatment–wildfire interaction and in part by the controls imposed by maximum forest biomass. None of the fuel treatment simulation scenarios resulted in increased system carbon.

Comparing fuel reduction treatments for reducing wildfire size and intensity in a boreal forest landscape of northeastern China

Fuel load is often used to prioritize stands for fuel reduction treatments. However, wildfire size and intensity are not only related to fuel loads but also to a wide range of other spatially related factors such as topography, weather and human activity. In prioritizing fuel reduction treatments, we propose using burn probability to account for the effects of spatially related factors that can affect wildfire size and intensity. Our burn probability incorporated fuel load, ignition probability, and spread probability (spatial controls to wildfire) at a particular location across a landscape. Our goal was to assess differences in reducing wildfire size and intensity using fuel-load and burn-probability based treatment prioritization approaches. Our study was conducted in a boreal forest in northeastern China. We derived a fuel load map from a stand map and a burn probability map based on historical fire records and potential wildfire spread pattern. The burn probability map was validated using historical records of burned patches. We then simulated 100 ignitions and six fuel reduction treatments to compare fire size and intensity under two approaches of fuel treatment prioritization. We calibrated and validated simulated wildfires against historical wildfire data. Our results showed that fuel reduction treatments based on burn probability were more effective at reducing simulated wildfire size, mean and maximum rate of spread, and mean fire intensity, but less effective at reducing maximum fire intensity across the burned landscape than treatments based on fuel load. Thus, contributions from both fuels and spatially related factors should be considered for each fuel reduction treatment.

Pre-wildfire management treatments interact with fire severity to have lasting effects on post-wildfire vegetation response

Land managers are routinely applying fuel reduction treatments to mitigate the risk of severe, stand-replacing fire in ponderosa pine communities of the southwestern US. When these treatments are burned by wildfire they generally reduce fire severity, but less is known about how they influence post-wildfire vegetation recovery, as compared to pre-fire untreated areas. We re-measured existing plots on the 2002 Rodeo–Chediski Fire 8years after the wildfire to track plant community and exotic species response, as well as patterns of pine regeneration. We compared areas that experienced high- and low-severity burning, and also examined how pre-fire treatment (cutting in an uneven-aged harvesting system with prescribed fire) modified vegetation response. We detected persistent differences between low- and high-severity areas for nearly all variables measured. In high-severity areas overall understory plant cover was 40.6%, nearly three times that observed in low-severity areas; shrub cover was 18.4%, four and a half times greater than that observed in low-severity areas. We also detected significantly higher exotic forb cover in high-severity areas, although overall exotic response was generally quite low (<2%). Although this represents a slight decrease in exotic cover since the initial 2004/2005 measurements, the frequency of several exotic species did increase through time (particularly Tragopogon dubius and Verbascum thapsus). Pre-fire treatment resulted in significantly higher pine regeneration frequency in treated versus untreated areas. Within low severity areas, mean pine regeneration frequency was 0.17 in pre-fire untreated areas versus 0.06 in areas that were not treated before the fire. Within high severity burned areas, mean pine regeneration frequency was 0.67 in pre-fire treated areas, but was only 0.19 in pre-fire untreated areas. This treatment effect in high-severity areas may be linked to reduction in the overall patch size of high burn severity in pre-fire treated areas, which resulted in a more heterogeneous mixture of low and moderate severity burning in the neighborhood. This pattern decreased distance to seed source, which likely facilitated the more frequent pine regeneration observed. In addition to the well-documented benefits of fuel reduction treatments in reducing subsequent fire severity, these data suggest that even where treated areas do burn severely the size of severely burned patches is limited in extent, which is likely to have important ramifications for future reforestation and retention of foundation species.

Shrub resprouting response after fuel reduction treatments: Comparison of prescribed burning, clearing and mastication

Fuel reduction treatments are commonly used to reduce the risk of severe wildfire. However, more information about the effects on plant resprouting is needed to help land managers select the most appropriate treatment. To address this question, we evaluated the resprouting ability of five shrub species after the application of different types of fuel reduction methods (prescribed burning, clearing and mastication) in two contrasting shrubland areas in northern Spain. The shrub species were Erica australis, Pterospartum tridentatum and Halimium lasianthum spp. alyssoides, Ulex gallii and Erica cinerea.For most of the species under study (E. australis, P. tridentatum, H. lasianthum spp. alyssoides and U. gallii), neither plant mortality nor the number nor length of sprouted shoots per plant differed between treatments, although in E. cinerea the number of shoots was more negatively affected by prescribed burning than by clearing or mastication.The pre-treatment plant size did not affect plant mortality or plant resprouting response, suggesting that this parameter alone is not a good indicator of plant resprouting after fuel reduction treatments. Stem minimum diameter after treatments, a proxy of treatment severity, was not related to plant mortality, number or length of resprouted shoots. The duration of temperatures higher than 300 °C during burning in plant crown had a negative effect on the length of resprouted shoots, only in E. cinerea.The results show that fuel reduction treatments did not prevent shrub response in any case. Some reflections on the applicability of treatments are discussed.

Short-term effects of fuel treatments on fisher habitat in the Sierra Nevada, California

The characteristics of western forests have changed as a result of fire suppression and fuel reduction treatments have become a public land management priority. The effects of these treatments on wildlife habitat, however, have received limited attention. The fisher (Martes pennanti) is a species of concern in California and is vulnerable to fuels treatments due to its association with dense forests and use of large and old trees as resting sites. We evaluated the effect of fuels treatments by estimating predicted resting and foraging habitat at two sites in the Sierra Nevada that are part of the national Fire and Fire Surrogate Study. One site included three treatments (mechanical harvest, prescribed fire, and mechanical harvest plus prescribed fire) and the other included early and late-season prescribed fire; both sites included control treatments. We sampled vegetation before and after treatment application to estimate variables that were included in resource selection probability functions. Predicted resting habitat was significantly lower for mechanical plus fire treatments, but the control did not differ from the fire only or the mechanical only treatment. Late, but not early, season burns had significant impact on predicted resting habitat. Reductions in canopy cover affected predicted resting habitat directly. Fisher foraging habitat, unlike resting habitat was unaffected by treatments at either site. Within a stand, a number of management actions can mitigate the potentially negative short-term effects of fuels treatments on fisher habitat. Evaluating the effects of fuels management at the resting site, home range and landscape scales will be necessary to administer a treatment program that can address fuel accumulation while also restoring and maintaining fisher habitat.

Pre‐fire fuel reduction treatments influence plant communities and exotic species 9 years after a large wildfire

AbstractQuestionsHow did post‐wildfire understorey plant community response, including exotic species response, differ between pre‐fire treated areas that were less severely burned, and pre‐fire untreated areas that were more severely burned? Were these differences consistent through time?LocationEast‐central Arizona, southwestern US.MethodsWe used a multi‐year data set from the 2002 Rodeo–Chediski Fire to detect post‐fire trends in plant community response in burned ponderosa pine forests. Within the burn perimeter, we examined the effects of pre‐fire fuels treatments on post‐fire vegetation by comparing paired treated and untreated sites on the Apache‐Sitgreaves National Forest. We sampled these paired sites in 2004, 2005 and 2011.ResultsThere were significant differences in pre‐fire treated and untreated plant communities by species composition and abundance in 2004 and 2005, but these communities were beginning to converge in 2011. Total understorey plant cover was significantly higher in untreated areas for all 3 yr. Plant cover generally increased between 2004 and 2005 and markedly decreased in 2011, with the exception of shrub cover, which steadily increased through time. The sharp decrease in forb and graminoid cover in 2011 is likely related to drought conditions since the fire. Annual/biennial forb and graminoid cover decreased relative to perennial cover through time, consistent with the initial floristics hypothesis. Exotic plant response was highly variable and not limited to the immediate post‐fire, annual/biennial community. Despite low overall exotic forb and graminoid cover for all years (&lt;2.5%), several exotic species increased in frequency, and the relative proportion of exotic to native cover increased through time.ConclusionsPre‐treatment fuel reduction treatments helped maintain foundation overstorey species and associated native plant communities following this large wildfire. The overall low cover of exotic species on these sites supports other findings that the disturbance associated with high‐severity fire does not always result in exotic species invasions. The increase in relative cover and frequency though time indicates that some species are proliferating, and continued monitoring is recommended. Patterns of exotic species invasions after severe burning are not easily predicted, and are likely more dependent on site‐specific factors such as propagules, weather patterns and management.