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Climate change is altering fire regimes globally, leading to an increased incidence of large and severe wildfires, including gigafires (>100,000 ha), that homogenise landscapes. Despite this, our understanding of how large, severe wildfires affect biodiversity at the landscape scale remains limited.We investigated the impact of a gigafire that occurred during the unprecedented 2019–20 Australian 'Black Summer' on terrestrial fauna. We selected 24 study landscapes, each 0.785 km2 in size, that represented a gradient in the extent of high severity fire, unburnt vegetation, and the diversity of fire severity classes ('pyrodiversity'). We used wildlife cameras to survey biodiversity across each landscape and quantified species activity, community and functional diversity, and predator–prey network metrics. We used Bayesian mixed‐effects models to assess the influence of fire‐induced landscape properties on these measures.Most native species showed resilience to the 2019–20 wildfires, displaying few relationships with fire‐induced properties of landscapes, including the extent of high severity fire, unburnt vegetation, or pyrodiversity.Community and functional diversity and measures of predator–prey networks were also largely unaffected by fire‐induced landscape properties, although landscapes with a greater proportion of high severity fire had higher abundance and richness of introduced animal species.Synthesis and applications: Despite prevailing narratives of widespread ecological destruction following the 2019–20 wildfires, our findings suggest widespread resilience, potentially facilitated by evolutionary adaptations of animals to fire. Interventions aimed at helping such species recover may not be necessary and could instead focus on the subset of species that are vulnerable to severe fire. While mixed‐severity fires are often advocated to promote biodiversity through pyrodiversity, our results suggest that such management efforts might not be necessary in our study region. Given that severe fire favours introduced animal species, invasive species management could focus on large, severely burnt areas. [ABSTRACT FROM AUTHOR]

This study introduces a methodology that integrates SHAP (SHapley Additive exPlanations) analysis with Random Forest (RF) classification to enhance the prediction accuracy of fire severity across diverse forested regions in Türkiye. Leveraging a comprehensive forest fire database spanning from 2018 to 2022 and utilizing the Google Earth Engine (GEE) platform, 436 fire events ranging from 9 to 53,764.1 hectares were automatically detected and mapped using the difference Normalized Burn Ratio (dNBR). Subsequently, a robust fire severity model was developed by incorporating 19 variables, including biophysical, topographic, climatic, and vegetation-related factors. The RF classification achieved noteworthy performance metrics, with an overall accuracy of 0.75, a Kappa value of 0.61, and a macro-average AUC value of 0.88. Furthermore, the integration of SHAP analysis provided insightful contributions to the RF classification model, elucidating the impacts of individual input features. Notably, variables such as NDMI (Normalized Difference Moisture Index), LAI (Leaf Area Index), and LWVI (Land Water Vegetation Index) emerged as significant influencers, followed by WSPD (Wind Speed) and LST (Land Surface Temperature). Additionally, an analysis of fire severity distribution across fuel types (FMT) revealed intricate patterns, underscoring the complex relationships between vegetation composition and fire behavior. The findings of this study have implications for forest management and wildfire risk assessment, offering valuable insights for decision-making processes. Furthermore, the integration of SHAP analysis with RF classification enhances the interpretability and transparency of machine learning-based fire severity prediction models, contributing to the advancement of fire management strategies. [ABSTRACT FROM AUTHOR]

This study investigates the role of prescribed grazing as a sustainable fire prevention strategy in Mediterranean ecosystems, with a focus on Sardinia, an area highly susceptible to wildfires. Using FlamMap simulation software, we modeled fire behavior across various grazing and environmental conditions to assess the impact of grazing on fire severity indicators such as flame length, rate of spread, and fireline intensity. Results demonstrate that grazing can reduce fire severity by decreasing combustible biomass, achieving reductions of 25.9% in fire extent in wet years, 60.9% in median years, and 45.8% in dry years. Grazed areas exhibited significantly lower fire intensity, particularly under high canopy cover. These findings support the integration of grazing into fire management policies, highlighting its efficacy as a nature-based solution. However, the study's scope is limited to small biomass fuels (1-h fuels); future research should extend to larger fuel classes to enhance the generalizability of prescribed grazing as a fire mitigation tool. [ABSTRACT FROM AUTHOR]

Background. Wildfire on rangelands in the mixed grassland can severely disrupt livestock operations. Understanding how fire severity impacts post-fire production recovery is important for grazing management. Aims. We examined how topography and other environmental factors influence wildfire severity, or the consumption of biomass and exposure of soil, under extreme (>120 km h-1) wind conditions in native mixed grass prairie in western Canada. We also examined how variation in fire severity impacts grassland production recovery. Methods. Fire severity and production recovery were measured using the bare soil index (BSI) and normalised difference vegetation index (NDVI). Impacts of topography, wind exposure, and site capability on fire severity and production recovery were assessed using generalised additive models. Key results. Fire severity varied as a function of slope, wind exposure and fuel load. Severity peaked at NDVI between 0 and 0.4, values associated with high litter content and minimal green vegetation. Interactions between slope and aspect with respect to dominant wind direction generated very high fire severity on slopes greater than 15° that faced into the wind. Production recovery increased moderately with higher fire severity and recovery was generally higher on sites with lower potential productivity. Implications. Post-fire production recovery was rapid; fire severity and site capability had only modest impacts on recovery rates demonstrating the resilience of grassland ecosystems to even severe wildfire. [ABSTRACT FROM AUTHOR]

Rising global fire activity is increasing the prevalence of repeated short‐interval burning (reburning) in forests worldwide. In forests that historically experienced frequent‐fire regimes, high‐severity fire exacerbates the severity of subsequent fires by increasing prevalence of shrubs and/or by creating drier understory conditions. Low‐ to moderate‐severity fire, in contrast, can moderate future fire behavior by reducing fuel loads. The extent to which previous fires moderate future fire severity will powerfully affect fire‐prone forest ecosystem trajectories over the next century. Further, knowing where and when a wildfire may act as a landscape‐scale fuel treatment can help direct pre‐ and post‐fire management efforts. We leverage satellite imagery and fire progression mapping to model reburn dynamics within forests that initially burned at low/moderate severity in 726 unique fire pair events over a 36‐year period across four large fire‐prone Western US ecoregions. We ask (1) how strong are the moderating effects of low‐ to moderate‐severity fire on future fire severity, (2) how long do moderating effects last, and (3) how does the time between fires (a proxy for fuel accumulation) interact with initial fire severity, day‐of‐burning weather conditions, and climate to influence reburn severity. Short‐interval reburns primarily occurred in dry‐ and moist‐mixed conifer forests with historically frequent‐fire regimes. Previous fire moderated reburn severity in all ecoregions with the strongest effects occurring in the California Coast and Western Mountains and the average duration of moderating effects ranging from 13 years in the Western Mountains to >36 years in the California Coast. The strength and duration of moderating effects depended on climate and initial fire severity in some regions, reflecting differences in post‐fire fuel accumulation. In the California Coast, moderating effects lasted longer in cooler and wetter forests. In the Western Mountains, moderating effects were stronger and longer lasting in forests that initially burned at higher severity. Moderating effects were largely robust to fire weather, suggesting that previous fire can mediate future fire severity even under extreme conditions. Our findings demonstrate that low‐ to moderate‐severity fire buffers future fire severity in historically frequent‐fire forests, underlining the importance of wildfire as a restoration tool for adapting to global change. [ABSTRACT FROM AUTHOR]

Background: Many fires in north Australian savannas are severe enough to cause canopy scorch, tree death and removal of stags. Better fire management may increase carbon sequestration in trees, perhaps including stags. Aims: To describe and analyse dynamics of stags in tropical savannas (600–1000 mm annual rainfall) in relation to fire and better understand their role in biomass sequestration. Methods: We monitored marked populations of live and dead trees over 12 years. Statistical models describing influences on stag creation and loss are applied in stag dynamics simulations. Key results: Immediately following severe fire, stag biomass increases acutely because many more live trees are killed than stags removed. Between severe fires, stag losses exceed tree deaths, so peaks are quite short. Many 'new' stags are lost (fallen or consumed) quickly. Conclusions: Between fires, stags comprise ~7.5–8.9% of standing above-ground biomass, more under dry conditions and during recovery from severe fire or other drivers of increased tree mortality. Fire management is unlikely to increase proportions of total woody biomass in stags unless it also reduces live biomass. Implications: Reducing frequency of severe fires can increase total carbon sequestration in dry tropical savannas. Prediction uncertainties and management risks around sequestration present daunting challenges for policy-makers and fire management practitioners. Fire creates stags by killing trees and also removes them. Proportions of stags lost usually exceed per capita mortality rates except after severe fire, when tree deaths greatly outnumber stag losses. Fire management is unlikely to increase the proportion of biomass in stags unless live biomass declines. This article belongs to the Collection Savanna Burning. [ABSTRACT FROM AUTHOR]

Wildfire strongly influences permafrost environment and soil organic carbon (SOC) pool. In this study, we reviewed the effects of fire severity, time after a fire, and frequency on SOC in boreal permafrost regions. This review highlighted several key points: the effect of wildfires on SOC increased with an increase of fire severity, and the amount of vegetation returned and surface organic matter replenished was less in a short term, which resulted in a significantly lower SOC content compared to that of before the fire. Within a short period after fire, the SOC in near‐surface permafrost and the active layer decreased significantly due to the loss of above ground biomass, permafrost thaw, and increased microbial decomposition; as the years pass after a fire, the SOC gradually accumulates due to the contributions of litter layer accumulation and rooting systems from different stages of succession. The increase in fire frequency accelerated permafrost thawing and the formation of thermokarst, resulting in the rapid release of a large amount of soil carbon and reduced SOC storage. Therefore, the study on the effects of wildfires on SOC in the boreal permafrost region is of great significance to understanding and quantifying the carbon balance of the ecosystem. [ABSTRACT FROM AUTHOR]

In August, 2022, forest fires occurred in Jiangjin District, Banan District, and Beibei District in Chongqing, respectively, with a total burned area of approximately 35 km2. After the wildfire, an ash layer with a thickness of 1～5 cm was deposited on the slope, and the vegetation and soil structure of the burned area were devastated. Affected by concentrated rainfall, it will pose a serious threat to the infrastructure of nearby villages and towns and residents’ lives and properties once the post-fire debris flow occurs. Based on the remote sensing, field investigation, and in-situ tests, the distribution characteristics of burned areas after the fire were identified. The measured data including the thickness of the ash layer, and the saturated hydraulic conductivity of the soil were derived. The severe, moderate, and low burned areas accounted for 9.6%, 34.0%, and 56.4% of the entire area, respectively, with the corresponding average thickness of ash and soil disturbance layer of 15.10 cm, 3.28 cm, and 1.15 cm. According to the prediction model based on expert experience, a total of 95 potential debris flow gullies in burned areas were evaluated for the susceptibility of post-fire debris flow, of which 1 was of high susceptibility, 43 were of medium susceptibility, 44 were of low susceptibility, and 7 were not prone to occur, contributing to 1.05%, 45.26%, 46.32%, and 7.37% of the total, respectively. Considering that a large number of loose solid sources besides ash and sediment still exist in the moderate and severe burned areas within watersheds under the current conditions, with strong water repellency of burned soil, once the medium and high susceptibility gullies are affected by concentrated rainfall in the rainy season, there is a relatively high probability for the post-fire debris flow occurrence. This study provides basic information for the prevention and risk management of post-fire debris flows.

In the summer of 2021, Türkiye experienced unprecedented forest fire events. Throughout that fire season, a total of 291 fire incidents, covering an area of 202,361 hectares, dominated the public agenda. This study aimed to document and analyze the 30 large fires (affecting over 100 hectares) of 2021 using remote sensing and GIS techniques. A comprehensive fire database was established, encompassing information on burned areas, fire severity, and fuel types, determined from forest-stand types and topographical properties including slope, elevation, and aspect (in eight directions). Sentinel-2 satellite images were utilized to calculate dNBR values for assessing fire severity, analyzed in the Google Earth Engine platform. Three GIS-integrated Python scripts were developed to construct the fire database. In total, 164,658 hectares were affected by these large fires, occurring solely in three regions of Türkiye: the Mediterranean, Aegean, and Eastern Anatolian. The majority of the burned area was situated in the Mediterranean region (59%), with only 3% in Eastern Anatolia. The burned areas ranged from a minimum of 150 hectares to a maximum of 58,798 hectares. Additionally, 679 hectares of residential areas and 22,601 hectares of agricultural land were impacted by the fire events. For each fire, 21 fuel types and their distribution were determined. The most prevalent fire-prone class, "Pure Turkish pine species (Pr-Çz)," accounted for 59.56% of the total affected area (99,516 hectares). Another significant fire-prone pine species, the "Pure Black pine species (Pr-Çk)," covered 7.67% (12,811 hectares) of the affected area. Fuel types were evaluated by considering both forest-stand development stages and canopy closure. Regarding forest-stand development stages, the largest area percentage burned belonged to the "Mature" class (26.48%). [ABSTRACT FROM AUTHOR]

Wildfires and logging play an important role in regulating soil carbon fluxes in forest ecosystems. In Siberia, large areas are disturbed by fires and logging annually. Climate change and increasing anthropogenic pressure have resulted in the expansion of disturbed areas in recent decades. However, few studies have focused on the effects of these disturbances on soil CO2 efflux in the vast Siberian areas. The objective of our research was to evaluate differences in CO2 efflux from soils to the atmosphere between undisturbed sites and sites affected by wildfire and logging in Scots pine forests of southern Siberia. We examined 35 plots (undisturbed forest, burned forest, logged plots, and logged and burned plots) on six study sites in the Angara region and four sites in the Zabaikal region. Soil CO2 efflux was measured using an LI-800 infrared gas analyzer. We found that both fire and logging significantly reduced soil efflux in the first years after a disturbance due to a reduction in vegetation biomass and consumption of the forest floor. We found a substantially lower CO2 efflux in forests burned by high-severity fires (74% less compared to undisturbed forests) than in forests burned by moderate-severity (60% less) and low-severity (37% less) fires. Clearcut logging resulted in 6–60% lower soil CO2 efflux at most study sites, while multiple disturbances (logging and fire) had 48–94% lower efflux. The soil efflux rate increased exponentially with increasing soil temperature in undisturbed Scots pine forests (p < 0.001) and on logged plots (p < 0.03), while an inverse relationship to soil temperature was observed in burned forests (p < 0.03). We also found a positive relationship (R = 0.60–0.83, p < 0.001) between ground cover depth and soil CO2 efflux across all the plots studied. Our results demonstrate the importance of disturbance factors in the assessment of regional and global carbon fluxes. The drastic changes in CO2 flux rates following fire and logging should be incorporated into carbon balance models to improve their reliability in a changing environment. [ABSTRACT FROM AUTHOR]

Indigenous communities throughout California, USA, are increasingly advocating for and practicing cultural fire stewardship, leading to a host of social, cultural, and ecological benefits. Simultaneously, state agencies are recognizing the importance of controlled burning and cultural fire as a means of reducing the risk of severe wildfire while benefiting fire‐adapted ecosystems. However, much of the current research on the impacts of controlled burning ignores the cultural importance of these ecosystems, and risks further marginalizing Indigenous knowledge systems. Our work adds a critical Indigenous perspective to the study of controlled burning in California's unique coastal grasslands, one of the most biodiverse and endangered ecosystems in the country. In this study, we partnered with the Amah Mutsun Tribal Band to investigate how the abundance and occurrence of shrubs, cultural plants, and invasive plants differed among three adjacent coastal grasslands with varying fire histories. These three sites are emblematic of the state's diverging approaches to grassland management: fire suppression, fire suppression followed by wildfire, and an exceedingly rare example of a grassland that has been repeatedly burned approximately every 2 years for more than 30 years. We found that Danthonia californica was significantly more abundant on the burned sites, whereas all included shrub species (Baccharis pilularis, Frangula californica, and Rubus ursinus) were significantly more abundant on the site with no recorded fire, results that have important implications for future cultural revitalization efforts and the loss of coastal grasslands to shrub encroachment. In addition to conducting a culturally relevant vegetation survey, we used Sentinel‐2 satellite imagery to compare the relative severities of the two most recent fire events within the study area. Critically, we used interviews with Amah Mutsun tribal members to contextualize the results of our vegetation survey and remote sensing analysis, and to investigate how cultural burning contrasts from typical Western fire management approaches in this region. Our study is a novel example of how interviews, field data, and satellite imagery can be combined to gain a deeper ecological and cultural understanding of fire in California's endangered coastal grasslands. [ABSTRACT FROM AUTHOR]

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Fire, invasive predators and low rainfall are key disturbances that interact to negatively impact wildlife. Reptiles are a highly threatened group, yet they have rarely been the focus of threat interaction research. Research assessing the impacts of disturbance on wildlife have typically focussed on changes in species richness and abundance. However, these metrics largely overlook the non‐lethal effects on individuals and populations persisting within disturbed landscapes. Body condition is an individual‐level response metric that is easily obtainable and provides insight into the cumulative behavioural and morphological changes within a population. We used a landscape‐scale natural experiment in southern Australia to investigate the impacts of prescribed fire severity, invasive red fox (Vulpes vulpes) control, low rainfall conditions and their interactive effects on reptile body condition. Low rainfall had pervasive negative effects on body condition, while prescribed fire had negative effects on the larger, viviparous species. We found a three‐way interactive effect, whereby the negative effects of fire and low rainfall were greater in areas where red foxes were controlled. These results indicate that there are complex ecological interactions at play, potentially including intra‐specific competition and interspecific interactions. Lower body condition in disturbed environments could have lasting implications for individual fitness and population persistence. For instance, species with lower body condition one‐year post‐fire could be more vulnerable to another fire event, compared to species that are able to maintain condition in post‐fire landscapes. With reptile body condition lower in a drier year, we advise minimising additional disturbance (e.g. avoid prescribed fires) during low rainfall years and drought periods. Along with research into ecological interactions, understanding how body condition indices relate to altered fitness is a priority knowledge gap. Such research could improve the ability to predict how species and populations will respond to future disturbances, a key challenge in wildlife disturbance research. [ABSTRACT FROM AUTHOR]

Wildfires are hazards of increasing significance in recent decades. Our ability to forecast the evolution of fire regimes is inhibited by the lack of records of key fire parameters such as fire severity. Boron isotopes in the soil clay fraction have been shown to vary with fire severity, where increased δ 11B coincides with higher fire severity. To elucidate the relationship between the B isotope composition of soil clays and fire events, we performed adsorption experiments by reacting rainwater with combusted leaves to analyse how B isotopes are fractionated during processes leading to the imparting of boron from plants to clay minerals in soil during and following combustion. We find that < 5% of B is volatilised during combustion of leaves and barks, where 11B is preferentially volatilised. No isotopic fractionation was detected during the leaching of leaves ash with rainwater, possibly due to the large water:clay ratio in our experiments. Adsorption of B from leaching solutions onto clay minerals shows isotopic fractionation, and hysteresis of the adsorbed B fraction. For experiments at pH between 7 and 9, the isotope fractionation between adsorbed and dissolved B (Δ 11B adsorbed-dissolved) ranges from −8.8 to −14.5 ‰ , indicating preferential adsorption of 10B onto clays compared to 11B. For experiments at pH > 10, the Δ 11B adsorbed-dissolved values range from +11.2 to +19.4 ‰ , indicating a preferential adsorption of 11B over 10B. Irregardless of pH, clay fractions in all experiments show increases in δ 11B, as the leaching solutions have high δ 11B relative to the soil clay minerals prior to their interaction. Ash of leaves combusted at 550 °C (highest temperature in our experiments) induce the greatest increase in solution pH and δ 11B in clays. Our experiments suggests that the higher B isotope composition of clays following a high severity fire is likely imparted by solutions that leach isotopically heavy B from the combusted canopy. [ABSTRACT FROM AUTHOR]

Ecosystem engineers modify their environment and influence the availability of resources for other organisms. Burrowing species, a subset of allogenic engineers, are gaining recognition as ecological facilitators. Burrows created by these species provide habitat for a diverse array of other organisms. Following disturbances, burrows could also serve as ecological refuges, thereby enhancing ecological resistance to disturbance events. We explored the ecological role of Common Wombat (Vombatus ursinus) burrows using camera traps in forests of southeastern Australia. We compared animal activity at paired sites with and without burrows, from the same fire severity class and habitat. We examined how animal activity at Common Wombat burrows was affected by the 2019–20 Black Summer bushfires in Australia. We predicted that burrows would serve as hotspots for animal activity and as refuges in burned areas. The activity of several species including Bush Rat (Rattus fuscipes), Agile Antechinus (Antechinus agilis), Lace Monitor (Varanus varius), Painted Button-quail (Turnix varius), and Grey Shrike-thrush (Colluricincla harmonica) increased at sites where Common Wombat burrows were present, while other species avoided burrows. Species that were more active at burrows tended to be smaller mammal and bird species that are vulnerable to predation, whereas species that avoided burrows tended to be larger mammals that might compete with Common Wombat for resources. Species composition differed between sites with and without burrows, and burrow sites had higher native mammal species richness. The association of several species with burrows persisted or strengthened in areas that burned during the 2019–20 Black Summer bushfires, suggesting that Common Wombat burrows may act as ecological refuges for animals following severe wildfire. Our findings have relevance for understanding how animals survive, persist, and recover following extreme wildfire events. [ABSTRACT FROM AUTHOR]

Context: Fire regimes are changing with ongoing climate change, which is leading to an increase in fire frequency and severity. Australia's Black Summer wildfires burned >12 million hectares in 2019–2020, affecting numerous threatened animal species. One of the species predicted to be most impacted was the threatened southern greater glider, an arboreal, hollow-dependent folivore, endemic to eastern Australia's eucalypt forests. Aims: This study aimed to assess how the 2019–2020 wildfires affected greater glider abundance and the resources they depend on in Woomargama National Park, New South Wales, Australia. Methods: We categorised 32 sites into four fire severity treatments with eight sites for each treatment: unburned (continuous unburned vegetation); refuges (unburned patches within the fire's perimeter); low-moderate severity; and high severity. We carried out two spotlight surveys per site using the double-observer method, beginning 21 months after the fires. We also conducted vegetation assessments on the same transects. To analyse the data, we used Generalised Linear Models to compare habitat differences based on fire severity, and N-mixture models to model greater glider detectability and abundance in relation to habitat and fire severity. Key results: We found that fire severity depleted several habitat variables including canopy cover and the number of potentially hollow-bearing trees, a resource that greater gliders rely on. Greater glider abundance also decreased in all burn categories, with the greatest decline experienced in areas burned at high severity. We also found that greater glider abundance was much lower in fire refuges than unburned habitat outside of the fire zone. Conclusions: Greater glider declines following severe wildfire can be at least partly attributed to the level of vegetation loss and the associated loss of key habitat resources. The contribution of direct mortality to population declines remains unknown. Implications: Greater glider conservation will rely heavily on protecting expansive unburned areas of suitable habitat and maintaining hollow-bearing trees. This study aimed to assess the impact of the 2019–2020 wildfires on the abundance of the southern greater glider in Woomargama National Park, New South Wales, Australia. Our results indicated that southern greater glider populations were lower in areas that burned during the fires, as well as in small, unburned refuges. These declines were linked to the loss of critical resources, such as an intact canopy and hollow-bearing trees. Photograph by Mikayla Green. [ABSTRACT FROM AUTHOR]

Coastal Maulino Forest, a biodiversity hotspot, is increasingly threatened by frequent and higher-severity wildfires. Endangered tree species, including Nothofagus spp., inhabit small, isolated native forest fragments surrounded by extensive Pinus radiata plantations, a non-native species that often colonises fire-affected areas. However, the seedling density of the native Chilean wineberry, Aristotelia chilensis, negatively correlates with the abundance of P. radiata seedlings in post-fire areas. This pattern emerged across areas burned at varying fire severities, sampled 8 and 24 months following the 2017 “Las Máquinas” megafire in Chile. The high proportion of plots lacking P. radiata seedlings, coupled with this negative relationship, suggests that A. chilensis may play a role in limiting P. radiata invasion. The negative relationship was most pronounced in areas with moderate fire severity, likely reflecting differences in shade tolerance between the species. While A. chilensis, a light-demanding species with some shade tolerance, can persist in partially shaded environments, P. radiata, a strictly light-demanding species, struggles under significant shade. In low-severity areas, no significant relationship was observed since the substantial native canopy remaining likely limits P. radiata establishment by shading. Conversely, in high-severity fire areas, the absence of a significant relationship might result from the detrimental effects on both species, including potential microbiome dependence for A. chilensis. Given the successful establishment of A. chilensis at low fire severity, enhancing its post-fire recruitment, particularly in moderately burned areas, could be a valuable strategy for mitigating P. radiata invasion and restoring fire-affected Mediterranean ecosystems.

Forest fires are the main threat to ecosystems and human life. The frequency, seasonality, extent and severity of fires affect ecosystems and the physical and chemical properties of the soil by direct (heating) and indirect (ash) effects. This could affect biodiversity and forest residency in the face of climate change. In this study, we evaluated the impact of fire severity on soil physical and chemical properties caused by forest fires in a high Andean area of Peru. For this purpose, the severity levels, the degree of hydrophobicity, and the physical and chemical properties of the soil were analyzed by sampling in affected areas (Pinus radiata D. Don plantation and shrubland) and unaffected areas. The results showed a very low severity in soil components, with a strong hydrophobicity, more persistent in the forest plantation area than in the shrubland. The physical properties of the soil did not show variations; however, in the Pinus plantations they showed variations in their chemical properties such as pH, electrical conductivity, organic matter, nitrogen and cation exchange capacity compared to areas not affected by the forest fires. Likewise, in the study area an adequate regeneration process was evidenced; in fact, it is important to apply mechanisms to accelerate the restoration of the vegetation cover and the physical and chemical quality of the vegetation.

Forty years of increasing fire size and severity in California’s Sierra Nevada were embodied by the 2021 Dixie Fire, which burned 389,837 ha between July and October, making it one of the largest, most destructive fires in California’s history. Historical fire regimes burned substantial areas annually, but primarily at low and moderate severities. Studies of the implications of fires like the Dixie Fire, which burn largely at higher severities, have focused on habitat change in the burned area; much less is known about potential edge effects. The hermit warbler (Setophaga occidentalis) and western bluebird (Sialia mexicana) have previously been characterized as species with dramatic, opposing post-wildfire responses: hermit warblers display a strongly negative response to fires while western bluebirds display a strong positive response. We conducted passive acoustic monitoring pre- and post-Dixie Fire inside and outside the burned area and analyzed the audio with the machine learning animal identification tool BirdNET. We then used a multi-season occupancy modeling framework to characterize both species’ site extinction and site colonization responses as a function of fire and habitat variables. We found no influence of edge effects, though this may have been a function of the low density of our recorders relative to the home range of these species. We did, however, observe contrasting relationships between the species. Hermit warbler site extinction was elevated in burned areas, particularly those burned at higher severities, while site colonization in unburned habitat was positively associated with canopy cover. Western bluebirds displayed the exact opposite pattern (elevated colonization in areas of high-severity fire, elevated extinction in unburned areas with high canopy cover). These results suggest contrasting trajectories for fire-influenced bird species under contemporary fire regimes and could guide hypothesis generation for broader studies of biodiversity responses to fire in this ecosystem.

The area burned in Spain exceeded historical records in 2022, when exceptionally warm conditions influenced wildfire events. The predicted intensification of wildfire regimes includes an increase in frequency, severity, and size. Therefore, a study of the wildfires that occurred in 2022 is necessary to understand their behaviour and possible environmental impacts. The objective of this study is to analyse the applicability of using spectral indices and Geographic Information System (GIS) approaches to map the spatial distribution and estimate potential soil losses using Sentinel-2 imagery and fire severity field data. Soil losses were estimated using an empirical model based on soil burn severity data collected in the field after wildfire. The relationship between the Normalized Difference Infrared Index (NDII), Difference Normalized Wildfire Ash Index (dNWAI), and the Blue Normalized Difference Vegetation Index (BNDVI) with the estimated soil losses was then evaluated. In addition, the influence of different time scales of the satellite images was analysed. The first period considered (Date I) ranges from 8 to 20 days after the beginning of the wildfire, which coincides with the field data collection. The second period considered (Date II) ranges from 28 to 35 days after the start of the wildfire. The results obtained showed a significant dependence relationship between the BNDVI index (using satellite images of Date I) and the estimated soil losses (R2 = 0.756), while the results of the NDII (R2 = 0.31) and dNWAI (R2 = 0.061), showed no spatial relationship with the estimated soil losses. Three of the largest wildfires in 2022 in Spain were analysed, and the results showed strong correlations of BNDVI index for Folgoso do Courel (R2 = 0.808), for Carballeda de Valedorras (R2 = 0.906), and for Sierra de la Culebra (R2 = 0.939). In addition, these results allowed the mapping and quantification of potential soil losses in areas where fire severity was high, totalling ∼2,50,000 Mg ha−1 in Folgoso do Courel, ∼3,70,000 Mg ha−1 in Carballeda de Valdeorras, and ∼4,70,000 Mg ha−1 in Sierra de la Culebra. Moreover, BNDVI values for estimating soil loss vary by vegetation type, and there is a positive correlation between severity classes and the BNDVI index. This approach can inform post-fire land management decisions in future wildfires and could be applied to other regions.

The Hengduan Mountains in Southwest China are currently facing a recurring and escalating threat of forest fires, posing a significant challenge to vegetation restoration efforts given the ecological value of this region. However, the effects of artificial restoration compared to natural regeneration on vegetation recovery dynamics have been less explored. This study focused on two sites in the Hengduan Mountains, primarily composed of conifer forests. One site employed a mix of artificial restoration measures, including tree planting, aerial grass seeding, and fertilizer application. The other site, which is relatively drier and colder, relied on natural regeneration. Four fire events in these two sites were compared to examine the effects of artificial restoration on vegetation recovery using remotely sensed data from Landsat and MODIS. Fire severity was classified using the differenced Normalized Burn Ratio (dNBR) and validated with field samples. Vegetation greenness loss and recovery trajectory were quantified using the near-infrared reflectance of vegetation (NIRv). The effects of artificial restoration were further analyzed after employing unburnt controls to minimize the impact of climate fluctuations. Results showed that fire severity mapping achieved an overall accuracy of 82%. The average NIRv loss across the four fires was 30%, 49%, and 69% in areas of low, moderate, and high severity, respectively. In low severity areas, natural and artificial recovery rates were similar, at 21% and 26% respectively, three years post-fire. In moderate severity areas, artificial restoration achieved a 46% recovery rate compared to 31% for natural recovery. In high severity areas, artificial restoration resulted in a 63% recovery rate versus 45% for natural recovery. Although the differences in recovery patterns may also be attributed to inherent variations in the vegetation composition, physical environment, and their interactions, this study suggests that high severity areas benefit significantly from artificial intervention for rapid recovery. Future studies should include more controlled experiments at the plot scale to further elucidate the processes of vegetation response to different artificial restoration measures.

Abstract This study examines the convergence between traditional and scientific knowledge regarding the use of fire and its potential to trigger wildfires, with possible impacts on ecosystems and human well-being. The research encompasses three distinct natural regions of Ecuador: the coast, the highlands, and the Amazon. Data on traditional fire use were collected through semi-structured interviews with 791 members from five local communities. These data were compared with climatic variables (rainfall (mm), relative humidity (%), wind speed (km/h), and wind direction) to understand the climatic conditions conducive to wildfires and their relationship with human perceptions. Furthermore, the severity of fires over the past 4 years (2019–2022) was assessed using remote sensing methods, employing the Normalized Burn Ratio (NBR) and the difference between pre-fire and post-fire conditions (NBR Pre-fire–NBR Post-fire). The results revealed a significant alignment between traditional knowledge, climatic data, and many fires, which were of low severity, suggesting potential benefits for ecosystems. These findings not only enable the identification of optimal techniques and timing for traditional burns but also contribute to human well-being by maintaining a harmonious balance between communities and their environment. Additionally, they provide valuable insights for the development of more inclusive and effective integrated fire management strategies in these natural areas of Ecuador.

This study examines the convergence between traditional and scientific knowledge regarding the use of fire and its potential to trigger wildfires, with possible impacts on ecosystems and human well-being. The research encompasses three distinct natural regions of Ecuador: the coast, the highlands, and the Amazon. Data on traditional fire use were collected through semi-structured interviews with 791 members from five local communities. These data were compared with climatic variables (rainfall (mm), relative humidity (%), wind speed (km/h), and wind direction) to understand the climatic conditions conducive to wildfires and their relationship with human perceptions. Furthermore, the severity of fires over the past 4 years (2019–2022) was assessed using remote sensing methods, employing the Normalized Burn Ratio (NBR) and the difference between pre-fire and post-fire conditions (NBR Pre-fire–NBR Post-fire). The results revealed a significant alignment between traditional knowledge, climatic data, and many fires, which were of low severity, suggesting potential benefits for ecosystems. These findings not only enable the identification of optimal techniques and timing for traditional burns but also contribute to human well-being by maintaining a harmonious balance between communities and their environment. Additionally, they provide valuable insights for the development of more inclusive and effective integrated fire management strategies in these natural areas of Ecuador. [ABSTRACT FROM AUTHOR]

Fires impact ecosystems globally and due to climate change, the frequency of high-severity fires has increased. As ecosystems change with altered fire regimes, changes in the communities that provide ecosystem services, such as pollination, have been reported. We studied fires with mixed-severity types that burned >20 years ago and compared insect floral visitor communities by focusing on an important floral resource, wax currant (Ribes cereum). Simultaneously, we conducted a pollinator exclusion experiment to determine how floral visitors impact fruit production of wax currant. Importantly, the pollinator community of wax currant is virtually unknown with only a single study that was conducted in a riparian ecosystem. We found that there was no difference in the floral visitor communities or fruit production of wax currant plants across fire severity, but our sample sizes were small. Notably, we found that the pollinator exclusion treatment had a significant impact on fruit production of wax currant plants, especially early season pollinators, which demonstrates the importance of insect pollinators across all fire severities for wax currant plants. Resumen Los incendios impactan los ecosistemas a nivel mundial y debido al cambio climático, hay aumentos en la frecuencia de aquellos de alta gravedad. A medida que los ecosistemas cambian con regímenes de incendios alterados, se han reportado efectos en las comunidades que brindan servicios ecosistémicos, como la polinización. Estudiamos incendios de gravedad mixta que ardieron hace más de 20 años y comparamos comunidades de insectos visitantes de flores en diferentes niveles de gravedad del incendio, centrándonos en un importante recurso floral, la grosella cera (Ribes cereum). Simultáneamente, llevamos a cabo un experimento de exclusión de polinizadores para determinar cómo los visitantes florales impactan el amarre de la grosella cera. La comunidad polinizadora de la grosella cerosa es prácticamente desconocida y solo se ha realizado otro estudio en un ecosistema ribereño. Descubrimos que no había diferencias en las comunidades de visitantes florales o en el amarre de frutos de las plantas de grosella cera según la gravedad del incendio, pero los tamaños de nuestras muestras fueron pequeños. Encontramos que el tratamiento de exclusión de polinizadores tuvo un impacto significativo en amarre de frutos de las plantas de grosella cera, especialmente en los polinizadores tempranos, lo que demuestra la importancia de los insectos polinizadores en todas las severidades de los incendios para las plantas de grosella cera. [ABSTRACT FROM AUTHOR]

Increasing frequency of droughts and wildfire are sparking concerns that these compounded disturbance events are pushing forested ecosystems beyond recovery. An improved understanding of how compounded events affect tree physiology and mortality is needed given the reliance of fire management planning on accurate estimates of postfire tree mortality. In this study, we use a toxicological dose-response approach to quantify the impact of variable-intensity drought and fire on the physiology and mortality of Pinus monticola and Pseudotsuga menziesii saplings. We show that the dose-response relationship between fire intensity and mortality shifts toward increased vulnerability under drought, indicating higher mortality with increasing drought at any fire intensity. The trajectory we observed in postfire chlorophyll fluorescence, an indicator of photosynthetic efficiency and stress, was an effective early warning sign of impending tree death. Postfire mortality modeling shows that accurate mortality classification can be achieved using prefire physiology and morphology metrics combined with fire intensity. Variable importance measures indicate that physiological condition and fire intensity have greater influence on the classification accuracy than morphological metrics. The wide range in drought and fire responses observed between this study and others highlights the need for more research on compound disturbance effects. Study Implications : An improved understanding of how drought and fire affect tree physiology and mortality is needed by natural resource managers looking to predict postfire tree mortality. This study advances our compound disturbance understanding by subjecting conifer saplings to variable drought and fire intensities and quantifying and modeling moderate-term recovery and mortality. The results show reduced physiological recovery and amplified mortality in saplings exposed to greater drought and fire intensity. Overall, this study highlights the importance of physiological condition when modeling tree mortality and could potentially be used to inform current postfire tree mortality models. [ABSTRACT FROM AUTHOR]

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The New Zealand bottlebrush, Metrosideros excelsa (Myrtaceae), was introduced into South Africa in the 1940s as an ornamental plant and subsequently naturalized in coastal parts of the Cape Floristic Region. Knowledge of M. excelsa's propagule pressure and response to fire in South Africa can inform evaluation of the species' invasion potential and management. We assessed M. excelsa's canopy and soil seed banks in burnt and unburnt stands; and post‐fire regeneration via reseeding and resprouting in relation to fire severity and tree size. Soil seed banks were assessed using an emergence technique, but no seedlings emerged from soil collected under burnt or unburnt plants suggesting that the species does not maintain a viable soil‐stored seed bank or germination triggers were not met (though unlikely). The annual seed crop in the canopies of unburnt trees was approximately 0.5–23 million seeds per tree. Viability, assessed through tetrazolium stain testing, of canopy‐borne seeds on unburnt trees was 18%, whereas a canopy fire, ranging in severity from low to extreme, killed all canopy‐borne seeds. Fifteen months post‐fire, the seedling to pre‐fire (live) tree ratio was 0.01, whereas 43% of burnt trees survived via basal resprouting. Fire severity had a non‐linear effect on tree survival (survival was highest after medium and high fire severity and lowest after low and extreme fire severity), while larger trees were more likely to survive fire. These results suggest that even low‐severity (safe) burning may be a useful control measure as it kills canopy‐borne seeds and causes substantial mortality, particularly of smaller trees. An opportunistic evaluation of an uncontrolled (no comparison with untreated individuals) foliar herbicide application to post‐fire resprouting individuals also showed considerable (91%) mortality. However, rigorous herbicide trials (also with herbicide in conjunction with burning) are required to inform the management of M. excelsa. [ABSTRACT FROM AUTHOR]

Temperate pine-oak forests provide multiple ecosystem goods and services; however, they are exposed to a great diversity of natural disturbances, such as forest fires. The objective of this study was to determine the post-fire effect on the residual structure, regeneration and forest floor. In the year 2021, 12 sites were established using selected sampling in three areas with different fire severity conditions (high, medium and low). The tree and forest floor dasometric inventory was carried out to determine and differentiate its biomass stored by NSI, the coordinates (X, Y) of natural regeneration were recorded to determine its spatial distribution. The severity levels were differentiated using the generalized linear model and comparison of means (Duncan, 0.05). Aboveground biomass accumulation (humus and litter, and soil specific gravity) did not show significant differences (P > 0.05) between severity levels (978.26 t ha-1). Sites with high levels of severity have a greater accumulation of necromass (287.91 t ha-1), which makes it difficult to establish natural regeneration. The best-preserved residual tree structure of the burned stand was found in sites with medium severity level since they accumulate biomass amounts of 134.3 t ha-1. In the same sense, these sites with medium severity contain the highest regeneration density (1,237 plants ha-1), which is reduced by up to 79 % in sites with high severity. The distribution of regeneration corresponds to an aggregate pattern across the three levels. The forest presents contiguous positive and negative post-fire changes. [ABSTRACT FROM AUTHOR]

We investigated the influence of fire severity, logging of burnt wood, local ecological factors and their interaction on the natural regeneration, survival and growth of maritime pine (Pinus pinaster Ait.), following a fire that took place in 2005. During the period 2006–2020, a sample of 1900 seedlings were monitored, in which three post-fire treatments were applied: (1) Early logging (before seedling emergence); (2) Delayed logging (after emergence); and (3) No management. Multivariate semi-parametric and non-parametric techniques were used to model seedling survival, estimated density and growth of natural pine regeneration. Seedling survival was 31% with a mean density of more than 2000 seedlings/ha at the end of the study period. Logging before seedling emergence was positively related with pine survival and density. Delayed logging resulted in the lowest seedling density and regeneration. Fire severity had a negative influence on regeneration density. The findings indicate that site conditions and fire severity have a stronger influence on natural regeneration of maritime pine than subsequent post-fire management treatments. In order to ensure the presence of maritime pine in pure or mixed stands, silvicultural work is required to control competition from other species and reduce the risk of new wildfires. [ABSTRACT FROM AUTHOR]

This study investigates the role of prescribed grazing as a sustainable fire prevention strategy in Mediterranean ecosystems, with a focus on Sardinia, an area highly susceptible to wildfires. Using FlamMap simulation software, we modeled fire behavior across various grazing and environmental conditions to assess the impact of grazing on fire severity indicators such as flame length, rate of spread, and fireline intensity. Results demonstrate that grazing can reduce fire severity by decreasing combustible biomass, achieving reductions of 25.9% in fire extent in wet years, 60.9% in median years, and 45.8% in dry years. Grazed areas exhibited significantly lower fire intensity, particularly under high canopy cover. These findings support the integration of grazing into fire management policies, highlighting its efficacy as a nature-based solution. However, the study’s scope is limited to small biomass fuels (1-h fuels); future research should extend to larger fuel classes to enhance the generalizability of prescribed grazing as a fire mitigation tool.

Climate change is driving increases in forest fire activity around the world. Consequently, recent and future research into the implications for affected biota, and its translation into policy and management, is of vital importance for the conservation of forest biodiversity. The dry sclerophyll forests of south-eastern Australia are affected by changing fire regimes, including having recently been extensively burnt. In this review, we synthesise contemporary research into the responses of dry sclerophyll forest birds to fire regimes, with a focus on contrasts in levels of time since fire, fire severity, fire frequency, and their interactions. We identify and discuss high-priority knowledge gaps and management issues in this domain. Recent studies have gained insights into the complexity of the effects of fire on birds by, for example, showing how avian fire responses are influenced by climate variability. In dry sclerophyll forests, most species that responded to time since fire were less likely to occur where it was short. There were mixed positive and negative responses to increasing fire severity and/or frequency among species in these forest bird assemblages. Given that quantification of the risk of extinction of rare and uncommon birds under increased fire activity is challenging, options for investigating their fire response are proposed. Availability of habitat for birds that flourish where fire is recent, severe and/or regular is unlikely to decline given current trends. We present a management approach that conceptualises large blocks of biologically connected forest with longer fire ages, but otherwise differing fire histories, as biodiversity reservoirs. Synthesis of contemporary research into the effects of fire on dry eucalypt forest birds is imperative, given that wildfire activity is increasing across south-eastern Australia. Recent studies have gained insights into the complexity of avian fire responses. We identify and discuss high-priority knowledge gaps and management issues in this domain. [ABSTRACT FROM AUTHOR]

Background. Fire regimes in many biomass-rich ecosystems worldwide are dominated by highseverity fires. Many of these systems lack fire-resistant traits or post-fire regeneration strategies. Understanding under which environmental and weather conditions they experience less severe fire is crucial for maintaining their persistence in the landscape. Aims. Understand the spatial and temporal conditions that allow burn severity attenuation across Patagonia's productivity gradient. Methods. We modelled burn severity as a function of topography, weather, vegetation and productivity. Key results. Low severity was a rare phenomenon, affecting only 8% of the areas burned. The probability of burning with high severity followed a hump-shaped relationship with productivity. Low severity occurred in fires that burned under cool and wet summer conditions in areas with sparser fuels or in wetter and more productive environments but with discontinuous and wet fuels. Conclusions. Across the regional gradient, ecosystems of intermediate productivity generally lack conditions for low burn severity. Temporally, low burn severity occurs in smaller fires burning in productive ecosystems during cool and wet summers. Implications. Future climate scenarios of increasing aridity and temperature in the region will disfavour conditions for low burn severity, thus promoting fire-mediated transitions from forests to alternative states dominated by more fire-adapted flammable species (e.g. shrublands). [ABSTRACT FROM AUTHOR]

Wildfires represent a significant threat to both ecosystems and human assets in Mediterranean countries, where fire occurrence is frequent and often devastating. Accurate assessments of the initial fire severity are required for management and mitigation efforts of the negative impacts of fire. Evapotranspiration (ET) is a crucial hydrological process that links vegetation health and water availability, making it a valuable indicator for understanding fire dynamics and ecosystem recovery after wildfires. This study uses the Mapping Evapotranspiration at High Resolution with Internalized Calibration (eeMETRIC) and Operational Simplified Surface Energy Balance (SSEBop) ET models based on Landsat imagery to estimate fire severity in five large forest fires that occurred in Spain and Portugal in 2022 from two perspectives: uni- and bi-temporal (post/pre-fire ratio). Using-fine-spatial resolution ET is particularly relevant for heterogeneous Mediterranean landscapes with different vegetation types and water availability. ET was significantly affected by fire severity according to eeMETRIC (F > 431.35; p-value < 0.001) and SSEBop (F > 373.83; p-value < 0.001) metrics, with reductions of 61.46% and 63.92%, respectively, after the wildfire event. A Random Forest machine learning algorithm was used to predict fire severity. We achieved higher accuracy (0.60 < Kappa < 0.67) when employing both ET models (eeMETRIC and SSEBop) as predictors compared to utilizing the conventional differenced Normalized Burn Ratio (dNBR) index, which resulted in a Kappa value of 0.46. We conclude that both fine resolution ET models are valid to be used as indicators of fire severity in Mediterranean countries. This research highlights the importance of Landsat-based ET models as accurate tools to improve the initial analysis of fire severity in Mediterranean countries. [ABSTRACT FROM AUTHOR]

The quantitative assessment of forest fire severity is significant for understanding the changes in ecological processes caused by fire disturbances. As a novel spectral index derived from the multi-objective optimization algorithm, the Analytic Burned Area Index (ABAI) was originally designed for mapping burned areas. However, the performance of the ABAI in detecting forest fire severity has not been addressed. To fill this gap, this study utilizes a ground-based dataset of fire severity (the composite burn index, CBI) to validate the effectiveness of the ABAI in detecting fire severity. First, the effectiveness of the ABAI regarding forest fire severity was validated using uni-temporal images from Sentinel-2 and Landsat 8 OLI. Second, fire severity accuracy derived from the ABAI with bi-temporal images from both sensors was evaluated. Finally, the performance of the ABAI was tested with different sensors and compared with representative spectral indices. The results show that (1) the ABAI demonstrates significant advantages in terms of accuracy and stability in assessing fire severity, particularly in areas with large numbers of terrain shadows and severe burn regions; (2) the ABAI also shows great advantages in assessing regional forest fire severity when using only uni-temporal remotely sensed data, and it performed almost as well as the dNBR in bi-temporal images. (3) The ABAI outperforms commonly used indices with both Sentinel-2 and Landsat 8 data, indicating that the ABAI is normally more generalizable and powerful and provides an optional spectral index for fire severity evaluation. [ABSTRACT FROM AUTHOR]

Fire related to household items poses a threat to life safety and residential property. In this study, the fire characteristics of single household items are established as a fundamental of risk assessment for performance-based design. Information on peak heat release rate, time to peak heat release rate and total heat released are collected from full-scale fire experiments in the literature. The household items are individually classified by their dimension: Television, Chair, Table, Armchair, Cabinet and Bed for statistical and probability distribution analyses. The analysis generally exhibits an increasing trend in the fire characteristics against the item dimension increment. A linear fit with a strong correlation value is achieved for the peak heat release rate and total heat released, while a weak correlation is observed to linearly fit the time to peak heat release rate. The ranked order of fitting statistics suggests Gamma, Log-Normal and Logistic distribution as the best-fit distribution respectively for the peak heat release rate, time to peak heat release rate and total heat released. The distribution parameters are provided and can be used for probabilistic fire assessment related to household items. [ABSTRACT FROM AUTHOR]

Climate change and human activities have disrupted historical fire regimes, leading to complex and far‐reaching impacts on global ecosystems. Despite extensive research in fire ecology, studies exploring vertebrate responses to megafires, and to nuanced fire characteristics, remain limited.We collected camera trap data 3–27 months following Australia's 2019–20 'Black Summer' megafires from 30 burnt sites and 10 unburnt sites. Our data included 14 animal species/groups, encompassing mammalian predators, small and medium‐sized mammals, large herbivores, and birds. We used generalised additive mixed models to assess the influence of time‐since‐the‐fires, burn status, fire severity, proportional area burnt, and vegetation type on species' activity.Models that included fire variables were well‐supported for all species. The proportional cover of low‐moderate or high‐extreme severity fire had substantial support for five species, particularly herbivores, which generally showed a preference for burnt sites but at differing fire severities. The proportional area burnt, disregarding severity, was well supported for four species. At highly burned sites fox activity peaked shortly after the fires while small to medium‐sized mammal activity increased more gradually. Vegetation type strongly influenced the response of four species to fire; in particular, wet forest birds preferred unburnt areas.Policy implications. We document variable short‐ to medium‐term responses of a range of species to fire which could help guide management interventions. We demonstrate that animal species' responses to fire are diverse and better captured using broader landscape scale fire variables. We found that species were strongly influenced by proportional area burnt, fire severity and vegetation type. Introduced foxes were attracted to recently burnt areas, so timely predator control may benefit vulnerable prey species. Wet forest species were sensitive to fires and could benefit from preservation and restoration of these habitats. Some species exploited low‐moderate severity burnt areas, while others preferred high‐severity burns. This suggests that species will face diverse challenges and opportunities in future extreme fire events. We emphasise the importance of using multi‐faceted approaches to account for the complex responses of co‐occurring species to fire events. [ABSTRACT FROM AUTHOR]

Bushfires are a natural component of the ecology of many landscapes, but megafires such as those experienced in Australia between July 2019 and April 2020 have substantial direct and indirect impacts on wildlife. Following these megafires, bushfires have begun to be considered a significant emerging threat to the vulnerable grey-headed flying-fox (Pteropus poliocephalus). In this study, we quantified the impact of the 2019–20 megafires on all known roost locations of the species by (1) determining the number of roosts within burnt areas represented by three fire severity mapping products, (2) classifying burnt roosts according to the severity with which they burnt, and (3) examining the distribution of distances to the nearest burnt areas for unburnt roosts. Our findings indicate that the impacts of the 2019–20 megafires on roosting habitat of the grey-headed flying-fox have hitherto been underestimated. Of 874 known grey-headed flying-fox roosts, we found that 134 roosts were situated within burnt areas, equating to 15 % of the species’ roost locations. Depending on the mapping products applied, part or all canopy vegetation was severely burnt in 27–36 % of burnt roosts, while in 11–14 % of burnt roosts, the canopy vegetation was burnt entirely. Of the 740 unburnt roosts, 50 % were located within 6.85 km from burnt areas, suggesting that, at a substantial number of roosts, flying-foxes were also indirectly affected by the fires, through the effects of smoke on roosting and locally foraging individuals, and through destruction of local foraging resources from burning. We discuss the implications of these findings for the conservation management of this vulnerable species.

The frequency of large, high-severity "mega-fires" has increased in recent decades, with numerous consequences for forest ecosystems. In particular, small mammal communities are vulnerable to post-fire shifts in resource availability and play critical roles in forest ecosystems. Inconsistencies in previous observations of small mammal community responses to fire severity underscore the importance of examining mechanisms regulating the effects of fire severity on post-fire recovery of small mammal communities. We compared small mammal abundance, diversity, and community structure among habitats that burned at different severities, and used vegetation characteristics and small mammal functional traits to predict community responses to fire severity three years after one mega-fire in the Sierra Nevada, California. Using a model-based fourth-corner analysis, we examined how interactions between vegetation variables and small mammal traits associated with their resource use were associated with post-fire small mammal community structure among fire severity categories. Small mammal abundance was similar across fire severity categories, but diversity decreased and community structure shifted as fire severity increased. Differences in small mammal communities were large only between unburned and high-severity sites. Three highly correlated fire-dependent vegetation variables affected by fire and the volume of soft coarse woody debris were associated with small mammal community structures. Furthermore, we found that interactions between vegetation variables and three small mammal traits (feeding guild, primary foraging mode, and primary nesting habit) predicted community structure across fire severity categories. We concluded that resource use was important in regulating small mammal recovery after the fire because vegetation provided required resources to small mammals as determined by their functional traits. Given the mechanistic nature of our analyses, these results may be applicable to other fire-prone forest systems, although it will be important to conduct studies across large biogeographic regions and over long post-fire time periods to assess generality.

Crown fire damage is a mixture of three principal fire-related components: charred material, scorched foliage, and unaltered green canopy. This study estimated the abundance of these physical alterations in two immediate post-fire Mediterranean forest contexts (Portugal and Italy) by applying linear spectral mixture analysis (LSMA) on Sentinel-2 imagery. The tree crowns fire damage was subsequently mapped, integrating fractional abundance information in a random forest (RF) algorithm, comparing the accuracy resulting from the adoption of generic or image spectral libraries as the primary investigative goal. Although image-derived endmembers resulted in more effectiveness in terms of fire-related components abundance quantification (LMSA-derived RMSE

Wildfires and logging play an important role in regulating soil carbon fluxes in forest ecosystems. In Siberia, large areas are disturbed by fires and logging annually. Climate change and increasing anthropogenic pressure have resulted in the expansion of disturbed areas in recent decades. However, few studies have focused on the effects of these disturbances on soil CO2 efflux in the vast Siberian areas. The objective of our research was to evaluate differences in CO2 efflux from soils to the atmosphere between undisturbed sites and sites affected by wildfire and logging in Scots pine forests of southern Siberia. We examined 35 plots (undisturbed forest, burned forest, logged plots, and logged and burned plots) on six study sites in the Angara region and four sites in the Zabaikal region. Soil CO2 efflux was measured using an LI-800 infrared gas analyzer. We found that both fire and logging significantly reduced soil efflux in the first years after a disturbance due to a reduction in vegetation biomass and consumption of the forest floor. We found a substantially lower CO2 efflux in forests burned by high-severity fires (74% less compared to undisturbed forests) than in forests burned by moderate-severity (60% less) and low-severity (37% less) fires. Clearcut logging resulted in 6–60% lower soil CO2 efflux at most study sites, while multiple disturbances (logging and fire) had 48–94% lower efflux. The soil efflux rate increased exponentially with increasing soil temperature in undisturbed Scots pine forests (p < 0.001) and on logged plots (p < 0.03), while an inverse relationship to soil temperature was observed in burned forests (p < 0.03). We also found a positive relationship (R = 0.60–0.83, p < 0.001) between ground cover depth and soil CO2 efflux across all the plots studied. Our results demonstrate the importance of disturbance factors in the assessment of regional and global carbon fluxes. The drastic changes in CO2 flux rates following fire and logging should be incorporated into carbon balance models to improve their reliability in a changing environment.

Climate warming, land use change, and altered fire regimes are driving ecological transformations that can have critical effects on Earth's biota. Fire refugia—locations that are burned less frequently or severely than their surroundings—may act as sites of relative stability during this period of rapid change by being resistant to fire and supporting post‐fire recovery in adjacent areas. Because of their value to forest ecosystem persistence, there is an urgent need to anticipate where refugia are most likely to be found and where they align with environmental conditions that support post‐fire tree recruitment. Using biophysical predictors and patterns of burn severity from 1180 recent fire events, we mapped the locations of potential fire refugia across upland conifer forests in the southwestern United States (US) (99,428 km2 of forest area), a region that is highly vulnerable to fire‐driven transformation. We found that low pre‐fire forest cover, flat slopes or topographic concavities, moderate weather conditions, spring‐season burning, and areas affected by low‐ to moderate‐severity fire within the previous 15 years were most commonly associated with refugia. Based on current (i.e., 2021) conditions, we predicted that 67.6% and 18.1% of conifer forests in our study area would contain refugia under moderate and extreme fire weather, respectively. However, potential refugia were 36.4% (moderate weather) and 31.2% (extreme weather) more common across forests that experienced recent fires, supporting the increased use of prescribed and resource objective fires during moderate weather conditions to promote fire‐resistant landscapes. When overlaid with models of tree recruitment, 23.2% (moderate weather) and 6.4% (extreme weather) of forests were classified as refugia with a high potential to support post‐fire recruitment in the surrounding landscape. These locations may be disproportionately valuable for ecosystem sustainability, providing habitat for fire‐sensitive species and maintaining forest persistence in an increasingly fire‐prone world. [ABSTRACT FROM AUTHOR]

A global trend of increasing tree cover in savannas has been observed and ascribed to a range of possible causes, including CO2 levels, changing rainfall and fire frequency. We tested these explanations in the Australian tropical savanna, taking 96 savanna 'cool burning' projects from Australia's emissions offset scheme as case studies. We obtained readings of tree cover and explanatory variables from published remote sensing or spatial data sources. These were analysed using time-series linear regression to obtain coefficients for the influence of severe fire occurrence, annual rainfall and prior percentage tree cover. Although statistically significant coefficients for the key variables were found in only half (severe fire) or one quarter (rainfall) of the individual project models, when comparing all the model coefficients across the rainfall gradient, ecologically coherent explanations emerge. No residual trend was observed, suggesting rising CO2 levels have not influenced tree cover over the study period. Our approach models tree cover change by separating ecological drivers from human-controlled factors such as fire management. This is an essential design feature of national emissions inventories and emissions offsets programs, where crediting must be additional to the expected baseline, and arise from human activity. [ABSTRACT FROM AUTHOR]

Wildfires strongly influence forest ecosystem processes, including carbon and nutrient cycling, and vegetation dynamics. As fire activity increases under changing climate conditions, the ecological and biogeochemical resilience of many forest ecosystems remains unknown.To investigate the resilience of forest ecosystems to changing climate and wildfire activity over decades to millennia, we developed a 4800‐year high‐resolution lake‐sediment record from Silver Lake, Montana, USA (47.360° N, 115.566° W). Charcoal particles, pollen grains, element concentrations and stable isotopes of C and N serve as proxies of past changes in fire, vegetation and ecosystem processes such as nitrogen cycling and soil erosion, within a small subalpine forest watershed. A published lake‐level history from Silver Lake provides a local record of palaeohydrology.A trend towards increased effective moisture over the late Holocene coincided with a distinct shift in the pollen assemblage c. 1900 yr BP, resulting from increased subalpine conifer abundance. Fire activity, inferred from peaks in macroscopic charcoal, decreased significantly after 1900 yr BP, from one fire event every 126 yr (83–184 yr, 95% CI) from 4800 to 1900 yr BP, to one event every 223 yr (175–280 yr) from 1900 yr BP to present.Across the record, individual fire events were followed by two distinct decadal‐scale biogeochemical responses, reflecting differences in ecosystem impacts of fires on watershed processes. These distinct biogeochemical responses were interpreted as reflecting fire severity, highlighting (i) erosion, likely from large or high‐severity fires, and (ii) nutrient transfers and enhanced within‐lake productivity, likely from lower severity or patchier fires. Biogeochemical and vegetation proxies returned to pre‐fire values within decades regardless of the nature of fire effects.Synthesis. Palaeorecords of fire and ecosystem responses provide a novel view revealing past variability in fire effects, analogous to spatial variability in fire severity observed within contemporary wildfires. Overall, the palaeorecord highlights ecosystem resilience to fire across long‐term variability in climate and fire activity. Higher fire frequencies in past millennia relative to the 20th and 21st century suggest that northern Rocky Mountain subalpine ecosystems could remain resilient to future increases in fire activity, provided continued ecosystem recovery within decades. [ABSTRACT FROM AUTHOR]

Fire severity classifications determine fire damage and regeneration potential in post-fire areas for effective implementation of restoration applications. Since fire damage varies according to vegetation and fire characteristics, regional assessment of fire severity is crucial. The objectives of this study were: (1) to test the performance of different satellite imagery and spectral indices, and two field—measured severity indices, CBI (Composite Burn Index) and GeoCBI (Geometrically structured Composite Burn Index) to assess fire severity; (2) to calculate classification thresholds for spectral indices that performed best in the study areas; and (3) to generate fire severity maps that could be used to determine the ecological impact of forest fires. Five large fires in Pinus brutia (Turkish pine) and Pinus nigra subsp. pallasiana var. pallasiana (Anatolian black pine)—dominated forests during 2020 and 2021 were selected as study sites. The results show that GeoCBI provided more reliable estimates of field—measured fire severity than CBI. While Sentinel-2 and Landsat-8/OLI images performed similarly well, MODIS performed poorly. Fire severity classification thresholds were determined for Sentinel-2 based RdNBR, dNBR, dSAVI, dNDVI, and dNDMI and Landsat-8/OLI based dNBR, dNDVI, and dSAVI. Among several spectral indices, the highest accuracy for fire severity classification was found for Sentinel-2 based RdNBR (72.1%) and Landsat-8/OLI based dNBR (69.2%). The results can be used to assess and map fire severity in forest ecosystems similar to those in this study. [ABSTRACT FROM AUTHOR]

This study explored, for the first time, the drivers shaping large fire size and high severity of forest fires classified as level-2 in Spain, which pose a great danger to the wildland–urban interface. Specifically, we examined how bottom-up (fuel type and topography) and top-down (fire weather) controls shaped level-2 fire behavior through a Random Forest classifier at the regional scale in Galicia (NW Spain). We selected for this purpose 93 level-2 forest fires. The accuracy of the RF fire size and severity classifications was remarkably high (>80%). Fire weather overwhelmed bottom-up controls in controlling the fire size of level-2 forest fires. The likelihood of large level-2 forest fires increased sharply with the fire weather index, but plateaued at values above 40. Fire size strongly responded to minimum relative humidity at values below 30%. The most important variables explaining fire severity in level-2 forest fires were the same as in the fire size, as well as the pre-fire shrubland fraction. The high-fire-severity likelihood of level-2 forest fires increased exponentially for shrubland fractions in the landscape above 50%. Our results suggest that level-2 forest fires will pose an increasing danger to people and their property under predicted scenarios of extreme weather conditions. [ABSTRACT FROM AUTHOR]

Background. Charcoal increases in reflectance with increased intensity and/or duration of heating, and this has been proposed as a potential quantitative metric for fire severity. Because fuel properties also influence reflectance, relationships between heat exposure and reflectance must currently be considered fuel-specific, limiting the application of the method. Aims. We assessed the effect of wood density on charcoal reflectance, to test whether it could be used as a proxy for overall variation in wood properties. Methods. Wood samples from 25 tree species were charred under constant conditions in a microcalorimeter, and reflectance measured by microphotometry. Key results. A positive linear relationship was found between wood density and charcoal reflectance (r = 0.53). Wood density was highly correlated with total heat release per unit volume (r = 0.94). Conclusions. Wood density accounts for a substantial component of the variation in charcoal reflectance under constant heat exposure. Implications. The relationship of density to reflectance shown here is relevant to the assessment of charcoals formed anaerobically, where endogenous heating (combustion of the sample itself) does not occur. In fire-produced chars, an additional increase in reflectance from endogenous heating should produce a stronger correlation, and density might account for a large component of the variation in reflectance under such conditions. [ABSTRACT FROM AUTHOR]

Fire activity during 2020 to 2021 in California, USA, was unprecedented in the modern record. More than 19,000 km2 of forest vegetation burned (10× more than the historical average), potentially affecting the habitat of 508 vertebrate species. Of the >9,000 km² that burned at high severity, 89% occurred in large patches that exceeded historical estimates of maximum high-severity patch size. In this 2-y period, 100 vertebrate species experienced fire across >10% of their geographic range, 16 of which were species of conservation concern. These 100 species experienced high-severity fire across 5 to 14% of their ranges, underscoring potentially important changes to habitat structure. Species in this region are not adapted to high-severity megafires. Management actions, such as prescribed fires and mechanical thinning, can curb severe fire behavior and reduce the potential negative impacts of uncharacteristic fires on wildlife. [ABSTRACT FROM AUTHOR]

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