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Large wild fires occurring in forests, grasslands, and chaparral in the last few years have aroused much public concern. Many have described these events as \"catastrophes\" that must be prevented through aggressive increases in forest thinning. Yet the real catastrophes are not the fires themselves but those land uses, in concert with fire-suppression policies that have resulted in dramatic alterations to ecosystem structure and composition. The first step in the restoration of biological diversity (forest health) of western landscapes must be to implement changes in those factors that have caused degradation or are preventing recovery. This includes changes in policies and practices that have resulted in the current state of wildland ecosystems. Restoration entails much more than simple structural modifications achieved though mechanical means. Restoration should be undertaken at landscape scales and must allow for the occurrence of dominant ecosystem processes, such as the natural fire regimes achieved through natural and/or prescribed fires at appropriate temporal and spatial scales.

Over the past several decades, the management of historically frequent-fire forests in the western United States has received significant attention due to the linked ecological and social risks posed by the increased occurrence of large, contiguous patches of high-severity fire. As a result, efforts are underway to simultaneously reduce potential fire and fuel hazards and restore characteristics indicative of historical forest structures and ecological processes that enhance the diversity and quality of wildlife habitat across landscapes. Despite widespread agreement on the need for action, there is a perceived tension among scientists concerning silvicultural treatments that modify stands to optimally reduce potential fire behavior (fuel hazard reduction) versus those that aim to emulate historical forest structures and create structurally complex stands (restoration). In this work, we evaluated thinning treatments in the Black Hills National Forest that exemplify the extremes of a treatment continuum that ranges from fuel hazard reduction to restoration. The goal of this work was to understand how the differing three-dimensional stand structures created by these treatment approaches altered potential fire behavior. Our results indicate that restoration treatments created higher levels of vertical and horizontal structural complexity than the fuel hazard reduction treatments but resulted in similar reductions to potential crown fire behavior. There were some trade-offs identified as the restoration treatments created larger openings, which generated faster mean rates of fire spread; however, these increased spread rates did not translate to higher levels of canopy consumption. Overall, our results suggest that treatments can create vertical and horizontal complexity desired for restoration and wildlife habitat management while reducing fire hazard and that they can be used in concert with traditional fuel hazard reduction treatments to reduce landscape scale fire risk. We also provide some suggestions to land managers seeking to design and implement prescriptions that emulate historical structures and enhance forest complexity.

Background: Wildfire is known to reduce forest carbon stocks, but the influence of antecedent disturbance on wildfire related carbon stock losses is not as well understood. Disturbances such as logging and wildfire may increase the vulnerability of remaining carbon stocks to subsequent wildfire. Conversely, these disturbances may reduce the impact of subsequent wildfire, resulting in lower carbon stock losses. Methods: We measured above ground carbon stocks in productive resprouting Eucalypt dominated forests before and after a mixed severity fire that burned during the 2019/20 ‘Black Summer’ fire season in south-eastern Australia. The initial surveys were stratified by time since logging and time since wildfire, allowing for an assessment of how these disturbance histories influence above ground carbon stock losses caused by subsequent wildfire. Results: Above ground carbon stock losses varied substantially; however, there was a weak decrease in losses associated with time since logging but not time since wildfire. Variance in carbon stock losses associated with logging were greater than that caused by the severity of the 2019/20 wildfire itself. Carbon losses and predicted effects of disturbance may be underestimated in some cases due to the accumulation of carbon at sites between pre- and post-fire surveys. Conclusions: This study presents the largest published dataset of direct carbon stock changes resulting from wildfire in eucalypt forests. Our findings indicate that logging reduces the stability of above ground carbon stocks in resprouting eucalypt forests. This information will be critical for land managers looking to manage forests for carbon sequestration.

Fuel hazard reduction treatments such as prescribed fire and mastication are widely used to reduce fuel hazard. These treatments help protect people from wildfire, yet may not be mutually beneficial for people and ecosystems in areas adapted to infrequent crown fire. Short-term studies indicate that some fuel hazard reduction treatments can be detrimental to biodiversity and ecosystem function, suggesting that land managers face an acute dilemma between protecting people or ecosystems. However, the long-term ecological trajectories and fuel hazard outcomes of fuel treatments are poorly understood. Using a 13-year replicated experimental study, we evaluated how shrub cover, non-native species abundance, native species diversity, and an obligate seeder responded to fuel treatments in California’s northern chaparral. The fuel hazard reduction treatments (fire and mastication) and their seasons of implementation (fall, winter, and spring) had unique influences on plant communities. Untreated controls had continuous shrub canopy with no understory throughout the study. Recovery of shrubs after mastication was slower than recovery after fire. Ten years after treatment, shrub cover in fire treatments and spring mastications produced 1 % to 2 % less cover than the control, whereas fall mastications produced 8 % less cover than the control. The number of non-native plants, including non-native annual grasses, was higher after mastication treatments compared to fire treatments after 10 years. Surprisingly, mastication treatments also increased cover of an uncommon native shrub that is an obligate seeder. The season of treatment also influenced these outcomes, but to a lesser extent than treatment type. Long-term shrub species composition did not follow the trends of short-term species composition of shrub recruitment. Based on these findings, we concluded that fuel hazard reduction treatments only reduce shrub cover for approximately 10 years, and can change plant community composition, suggesting that thorough consideration of the decision to use fuel hazard reduction treatments is warranted.

Many historically fire-adapted forests are now highly susceptible to damage from insects, pathogens, and stand-replacing fires. As a result, managers are employing treatments to reduce fuel loadings and to restore the structure, species, and processes that characterized these forests prior to widespread fire suppression, logging, and grazing. However, the consequences of these activities for understory plant communities are not well understood. We examined the effects of thinning and prescribed fire on plant composition and diversity in Pinus ponderosa forests of eastern Washington (USA). Data on abundance and richness of native and nonnative plants were collected in 70 stands in the Colville, Okanogan, and Wenatchee National Forests. Stands represented one of four treatments: thinning, burning, thinning followed by burning, or control; treatments had been conducted 3-19 years before sampling. Multi-response permutation procedures revealed no significant effect of thinning or burning on understory plant composition. Similarly, there were no significant differences among treatments in cover or richness of native plants. In contrast, nonnative plants showed small, but highly significant, increases in cover and richness in response to both thinning and burning. In the combined treatment, cover of nonnative plants averaged 2% (5% of total plant cover) but did not exceed 7% (16% of total cover) at any site. Cover and richness of nonnative herbs showed small increases with intensity of disturbance and time since treatment. Nonnative plants were significantly less abundant in treated stands than on adjacent roadsides or skid trails, and cover within these potential source areas explained little of the variation in abundance within treated stands. Although thinning and burning may promote invasion of nonnative plants in these forests, our data suggest that their abundance is limited and relatively stable on most sites.

Creating more defensible neighborhoods in the wildland-urban interface requires better understanding of local preferences for residential landscaping meant to reduce wildland fire risk and of the motivation of residents to undertake action at home. A survey of local residents within two areas of fire-prone pitch pine ecosystem in the northeastern United States used a photo questionnaire depicting scenes of different residential landscaping, as well as written items about residents’ plans for creating more defensible space. The results indicate a low to mid-level perception of wildfire risk to homes and property, despite the participants’ experience with wildfires in the area. Participants showed higher preference for scenes showing a balance of native plants and ornamental lawns than for those with lawn only or entirely native forest plantings. Despite their perceptions, residents engaged in defensible space strategies. In particular, those with a higher degree of natural areas knowledge were more likely to thin trees or vegetation than were other residents. The desire to retain mature trees around residential homes is a challenge to creating more defensible space. The connection between landscape preference and willingness to engage in residential landscaping may both benefit local ecosystems and contribute to their resistance to fire.

Changes in vegetation and fuels were evaluated from measurements taken before and after fuel reduction treatments (prescribed fire, mechanical treatments, and the combination of the two) at 12 Fire and Fire Surrogate (FFS) sites located in forests with a surface fire regime across the conterminous United States. To test the relative effectiveness of fuel reduction treatments and their effect on ecological parameters we used an information-theoretic approach on a suite of 12 variables representing the overstory (basal area and live tree, sapling, and snag density), the understory (seedling density, shrub cover, and native and alien herbaceous species richness), and the most relevant fuel parameters for wildfire damage (height to live crown, total fuel bed mass, forest floor mass, and woody fuel mass). In the short term (one year after treatment), mechanical treatments were more effective at reducing overstory tree density and basal area and at increasing quadratic mean tree diameter. Prescribed fire treatments were more effective at creating snags, killing seedlings, elevating height to live crown, and reducing surface woody fuels. Overall, the response to fuel reduction treatments of the ecological variables presented in this paper was generally maximized by the combined mechanical plus burning treatment. If the management goal is to quickly produce stands with fewer and larger diameter trees, less surface fuel mass, and greater herbaceous species richness, the combined treatment gave the most desirable results. However, because mechanical plus burning treatments also favored alien species invasion at some sites, monitoring and control need to be part of the prescription when using this treatment.

AIM: Prescribed fire is a common land management for reducing risks from unplanned fires. However, the universality of such effectiveness remains uncertain due to biogeographical variation in fuel types, climatic influences and fire regimes. Here, we explore biogeographical patterns in the effectiveness of prescribed fire by calculating leverage (the reduction in unplanned area burnt resulting from recent previous area burnt) across south‐eastern Australia over a 25 year period. LOCATION: The 30 bioregions of south‐eastern Australia. METHODS: We quantified leverage in each bioregion from fire records from 1975–2009, controlling for variation in annual weather. We also identified potential drivers of variation in leverage by relating the bioregional leverage values to measures of fuel type and growth, climate, and weather extremes. RESULTS: Leverage was inferred in four bioregions while in the other 26 bioregions no leverage was detected or prescribed fire had the opposite effect (fire‐follows‐fire). Leverage occurred in the forested eastern section of the study area, where rainfall, fuel load and fire activity is high and fire weather is mild. In all bioregions, weather was a stronger predictor than past‐fire extent of area burnt in a particular year. MAIN CONCLUSIONS: Our analysis of leverage shows that the effectiveness of prescribed fire varies regionally in predictable ways, which means that fuel management strategies applied in one region are not necessarily applicable in another. In most bioregions prescribed burning is likely to have very little effect on subsequent extent of unplanned fire, and even in regions where leverage occurs, large areas of treatment are required to substantially reduce the area burned by unplanned fire.

Various studies have established a link between household fuel use and diverse health conditions. However, research examining the impact of household fuel use on migraine remains scarce. Therefore, the objective of this study was to explore the association between household fuel use and the risk of migraine, as well as the potential modifying effects of sleep duration. Utilizing a nationwide representative cohort from the China Health and Retirement Longitudinal Study (CHARLS) from 2011 to 2015, we included 9,160 participants aged 45 years and older who did not have migraine at baseline. Household fuel use was categorized into two groups: clean fuel and solid fuel. Migraine was defined based on self-reports using the ID-Migraine questionnaire. Sleep duration was classified into two groups: Non-ideal sleep duration (<7 hours/d or >8 hours/d) and ideal sleep duration (7-8 hours/d). Cox proportional hazards regression models were utilized to assess the associations of solid fuel use and sleep duration with migraine. The modifying effect of sleep duration was analyzed. During a 4-year follow-up period, 520 migraine cases were identified. The use of solid fuels was associated with an increased risk of migraine compared to the use of clean fuels. The hazard ratio (HR) and 95% confidence interval (CI) was 1.34 (1.06-1.69) for heating and 1.29 (1.06-1.58) for cooking with solid fuels, compared to the use of clean fuels. The use of solid fuels for heating and cooking simultaneously was also associated with an elevated risk of migraine (HR: 1.53, 95% CI: 1.16-2.01), compared with the simultaneous use of clean fuels. Additionally, compared with consistent solid fuels users, those switching from solid to clean fuel and consistently using clean fuels for heating and cooking showed a decreased risk of migraine. For heating, the HR was 0.66 (95% CI: 0.49-0.90) for switching from solid to clean fuel and 0.54 (95% CI: 0.38-0.77) for consistently using clean fuels; for cooking, the corresponding HRs were 0.74 (95% CI: 0.57-0.97) and 0.68 (95% CI: 0.53-0.86), respectively. Ideal sleep duration modified the association between solid fuel use and migraine. Among individuals with non-ideal sleep duration, the use of solid fuels for heating (HR: 1.47, 95% CI: 1.09-1.97, P = 0.010) and cooking (HR: 1.31, 95% CI: 1.02-1.68, P value = 0.034) was significantly associated with an increased risk of migraine. In contrast, these associations were not statistically significant among those with ideal sleep duration (heating: HR: 1.13, 95% CI: 0.77-1.65, P = 0.537; cooking: HR: 1.28, 95% CI: 0.90-1.81, P = 0.165). Household solid fuel use was associated with an increased risk of migraine, and this association was modified by ideal sleep duration. Reducing exposure to household air pollution from solid fuel use and promoting healthy sleep behaviors may help to reduce the burden of migraine in areas where solid fuel use is prevalent.

The Natura 2000 network is crucial to conserve biodiversity in the European Union and provides hotspots for certain ecosystem services. Grazing, a common land use in different Natura 2000 habitat types, may contribute to the maintenance of protected plant communities and reduce fuel loads and wildfire hazard. Our study aims to assess the effects of grazing on plant composition and conservation status of calcareous shrub-grassland Natura 2000 habitat types, as well as its effects on fire hazard reduction and aboveground carbon storage. We surveyed plant communities grazed by goats in fenced (ungrazed) and open (grazed) plots in a mosaic of calcareous shrub-grassland habitat types and assessed plant species composition and habitat conservation status. We also assessed aboveground plant biomass in grazed and ungrazed plots and modelled potential fire behaviour in those plots for each habitat. With the exception of cryptogams, grazing did not affect plant cover, but positively affected species richness (mean ± SD: 26.80 ± 11.65 vs. 29.37 ± 8.59, P = 0.01; fenced vs. unfenced) and Shannon diversity (2.11 ± 0.81 vs. 2.33 ± 0.55, P < 0.01) in the habitat mosaic. Furthermore, grazing did not affect the conservation status of two out of three of the studied habitat types. Additionally, grazing decreased the fire hazard in grass and dwarf shrub communities without reducing aboveground carbon stocks significantly. Our results show that moderate grazing is a management practice that effectively contribute to the conservation of Natura 2000 shrub-grassland habitat types through reduction of wildfire hazard and maintenance of habitat conservation status.