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Treed peatlands exhibit both crown and smouldering fire potential; however, neither are included in Canadian wildfire management models and, as such, they are not formally represented in management decision-making. The lack of smouldering fire risk assessment is a critical research gap as these fires can represent heavy resource draws and are predominant sources of smoke, air pollutants and atmospheric carbon. Here, for the first time, we combine existing knowledge of the controls on smouldering peat fire with expert opinion-based weightings through a multi-criteria decision analysis, to map the smouldering fire potential (i.e. hazard) of treed peatlands in the Boreal Plains, Alberta, Canada. We find that smouldering potential varies considerably between treed peatlands and that areas of sparser peatland coverage may contain high smouldering-potential peatlands. Further, we find that treed peatlands are a common feature in the wildland–human interface and that proportionally, the area of high smouldering potential is greater closer to roads compared with farther away. Our approach enables a quantitative measure of smouldering fire potential and evidences the need to incorporate peatland–wildfire interactions into wildfire management operations. We suggest that similar frameworks could be used in other peatland dominated regions as part of smouldering fire risk assessments.

As regulated by the ‘fire environment triangle', three major forces are essential for understanding wildfire danger: (1) topography, (2) weather and (3) fuel. Within this concept, this study aimed to assess the wildfire danger for China based on a set of topography, weather and fuel variables. Among these variables, two remotely sensed key fuel variables, fuel moisture content (FMC) and foliage fuel load (FFL), were integrated into the assessment. These fuel variables were retrieved using radiative transfer models from the MODIS reflectance products. The random forest model identified the relationships between these variables and historical wildfires and then produced a daily updated and moderate-high spatial resolution (500m) dataset of wildfire danger for China from 2001 to 2020. Results showed that this dataset performed well in assessing wildfire danger for China in terms of the ‘Area Under the Curve' value, the fire density within each wildfire danger level, and the visualisation of spatial patterns. Further analysis showed that when the FMC and FFL were excluded from the assessment, the accuracy decreased, revealing the reasonability of the remotely sensed FMC and FFL in the assessment.

Biomass fires in Indonesia emit high levels of greenhouse gases and particulate matter, key contributors to global climate change and poor air quality in south-east Asia. In order to better understand the drivers of biomass fires across Indonesia over multiple years, we examined the distribution and probability of fires in Sumatra, Kalimantan (Indonesian Borneo) and Papua (western New Guinea) over four entire calendar years (2002, 2005, 2011 and 2015). The 4 years of data represent years with El Niño and La Niña conditions and high levels of data availability in the study region. Generalised linear mixed-effects models and zero-inflated negative binomial models were used to relate fire hotspots and a range of spatial predictor data. Geographic differences in occurrences of fire hotspots were evident. Fire probability was greatest in mixed-production agriculture lands and in deeper, degraded peatlands, suggesting anthropogenic activities were strong determinants of burning. Drought conditions in El Niño years were also significant. The results demonstrate the importance of prioritising areas of high fire probability, based on land use and other predisposing conditions, in effective fire management planning.

Future changes in society and climate are expected to affect wildfire activity in the south-eastern United States. The objective of this research was to understand how changes in both climate and society may affect wildfire in the coming decades. We estimated a three-stage statistical model of wildfire area burned by ecoregion province for lightning and human causes (1992–2010) based on precipitation, temperature, potential evapotranspiration, forest land use, human population and personal income. Estimated parameters from the statistical models were used to project wildfire area burned from 2011 to 2060 under nine climate realisations, using a combination of three Intergovernmental Panel on Climate Change-based emissions scenarios (A1B, A2, B2) and three general circulation models. Monte Carlo simulation quantifies ranges in projected area burned by county by year, and in total for higher-level spatial aggregations. Projections indicated, overall in the Southeast, that median annual area burned by lightning-ignited wildfire increases by 34%, human-ignited wildfire decreases by 6%, and total wildfire increases by 4% by 2056–60 compared with 2016–20. Total wildfire changes vary widely by state (–47 to +30%) and ecoregion province (–73 to +79%). Our analyses could be used to generate projections of wildfire-generated air pollutant exposures, relevant to meeting the National Ambient Air Quality Standards.

Regulatory and certification agencies need historical fire pattern information across the Canadian boreal forest to support natural disturbance-based management. Landsat-derived spectral indices have been used extensively to map burn severity in North America. However, satellite-derived burn severity is difficult to define and quantify, and relies heavily on ground truth data for validation, which hinders fire pattern analysis over broad scales. It is therefore critical to translate burn severity estimates into more quantifiable measurements of post-fire conditions and to provide more cost-effective methods to derive validation data. We assessed the degree to which Landsat-derived indices and ancillary data can be used to classify canopy mortality for 10 fires in the boreal forest of Alberta and Saskatchewan, Canada. Models based on two and three mortality classes had overall accuracies of 91 and 72% respectively. The three-level classification has more utility for resource management, with improved accuracy at predicting unburned and complete canopy mortality classes (93 and 66%), but is relatively inaccurate for the partial mortality class (56%). The results presented here can be used to assess the suitability of different canopy mortality models for forest fire management goals, to help provide objective, consistent and cost-effective results to analyse historical fire patterns across the Canadian boreal forest.

Fuel loading estimates from planar intersect sampling protocols for fine dead down woody surface fuels require an approximation of the mean squared diameter (d2) of 1-h (0–0.63 cm), 10-h (0.63–2.54 cm), and 100-h (2.54–7.62 cm) timelag size classes. The objective of this study is to determine d2 in ponderosa pine (Pinus ponderosa) forests of New Mexico and Colorado, USA in natural, partially harvested, and partially harvested and burned sites to improve fine woody fuel loading estimates. Resulting estimates were generally higher in the 1- and 10-h classes and lower in the 100-h classes when compared with previously published values from other regions. The partially harvested and burned values for 1- and 100-h classes were also significantly lower than in the other stand conditions. Using bootstrap analysis, it was determined that 35 samples would be sufficient to create an accurate estimate of d2 values.

The relative importance of various drivers of fire regimes in savanna ecosystems can be location-specific. We utilised satellite-derived time-series burned area (2001–13) to examine how spatiotemporal variations in burned area and fire frequency were determined by rainfall, vegetation morphology and land use in semiarid savanna. Mean precipitation of the rainy season (Nov–Apr) had a strong and positive relationship with burned area in the following dry season (variance explained 63%), with the relationship being strongest inside protected areas (variance explained 73%). Burned area and fire frequency were higher in vegetation types with higher herbaceous cover, indicating a causal link between herbaceous load and fire. Among land use, fire frequency was highest in protected areas and lowest in farms and ranches. Spatial models (generalised linear models with Poisson and negative binomial distribution) accounting for spatial autocorrelation showed that land-use classes and vegetation types together explained approximately half of the deviance in null model (48%). Existence of fences and boreholes resulted in finer-scale spatial differences in fire frequency. There was minimal dependence of vegetation types on land-use classes in determining fire frequency (interaction between the two predictors was minimal). These results have significant implications for understanding drivers of fire activity in savanna ecosystems.

We examined the seasonal distribution of lightning- and human-caused wildfires ≥ 2ha in Canada for two time periods: 1959–2018 and 1981–2018. Furthermore, we investigated trends in seasonality, number of fires per year and number of days with fire starts per year for human- and lightning-caused fires. Nationally, lightning fires peaked from June to August, whereas human fires peaked during May. There was, however, notable variation in the seasonal distributions of human- and lightning-caused fires between ecozones. Likewise, trends in season start and end dates varied among ecozones and time series, with trends generally being stronger for human-caused fires. Trends in the number of fires from 1959 to 2018 suggested significant increases in the number of lightning-caused fires and days with lightning ignitions across almost all ecozones, while from 1981 to 2018 there was a significantly decreasing trend in the number of human-caused fires and days with human ignitions in almost all ecozones. The highest densities of human-caused fires occurred in the Montane Cordillera and Atlantic Maritime, while the highest density of lightning-caused fires occurred in the Boreal Shield West. The Montane Cordillera and Taiga Shield West showed significant increases in the number of lightning fires and days with lightning ignitions across both time series.

The Weather Research and Forecasting (WRF) model was used to simulate fire weather for the south-west of Western Australia (SWWA) over multiple decades at a 5-km resolution using lateral boundary conditions from the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA)-Interim reanalysis. Simulations were compared with observations at Australian Bureau of Meteorology meteorological stations and the McArthur Forest Fire Danger Index (FFDI) was used to quantify fire weather. Results showed that, overall, the WRF reproduced the annual cumulative FFDI at most stations reasonably well, with most biases in the FFDI ranging between –600 and 600. Biases were highest at stations within the metropolitan region. The WRF simulated the geographical gradients in the FFDI across the domain well. The source of errors in the FFDI varied markedly between the different stations, with no one particular variable able to account for the errors at all stations. Overall, this study shows that the WRF is a useful model for simulating fire weather for SWWA, one of the most fire-prone regions in Australia.

The simultaneous occurrence of wildfire can hinder firefighting effectiveness via multiple mechanisms that might explain historical resource demand trends. We validate this hypothesis by using data from the Monitoring Trends in Burn Severity (MTBS) project to determine if simultaneous wildfire occurrence is correlated with preparedness levels and examine potential changes in simultaneous wildfire activity over the 1984–2015 record. We explore patterns that are helpful for predicting simultaneous wildfire, such as seasonal variability in simultaneity, cross-regional correlations and models of simultaneous wildfire occurrence based on dryness and lightning indicators. We show that simultaneous wildfire is at least as correlated with preparedness levels as other burned area measures and identify changes in simultaneous wildfire occurrence within the western and southern United States. Seasonal variation and spatial autocorrelation in simultaneous wildfire occurrence provide evidence of coupling of wildfire activity in portions of the western United States. Best-approximating models of simultaneity suggest that high levels of simultaneous wildfire often coincided with low fuel moisture and high levels of lightning occurrence. Model uncertainty was high in some contexts but, with only a few exceptions, there was strong evidence that the best model should include both a dryness and lightning indicator.

High temporal resolution information on burnt area is needed to improve fire behaviour and emissions models. We used the Moderate Resolution Imaging Spectroradiometer (MODIS) thermal anomaly and active fire product (MO(Y)D14)asinputtoakriginginterpolationtoderivecontinuousmapsofthetimingofburntareafor16largewildland fires. For each fire, parameters for the kriging model were defined using variogram analysis. The optimal number of observations used to estimate a pixel's time of burning varied between four and six among the fires studied. The median standarderrorfromkrigingrangedbetween0.80and3.56daysandthemedianstandarderrorfromgeolocationuncertainty was between 0.34 and 2.72 days. For nine fires in the south-western US, the accuracy of the kriging model was assessed using high spatial resolution daily fire perimeter data available from the US Forest Service. For these nine fires, we also assessed the temporal reporting accuracy of the MODIS burnt area products (MCD45A1 and MCD64A1). Averaged over the nine fires, the kriging method correctly mapped 73% of the pixels within the accuracy of a single day, compared with 33% for MCD45A1 and 53% for MCD64A1. Systematic application of this algorithm to wildland fires in the future may lead to new information about vegetation, climate and topographic controls on fire behaviour. Additional keywords: carbon emissions, fire growth, fire propagation, fire spread.

Several large Swedish wildfires during recent decades were caused by forestry machinery in operation, fires for which there is still no characterisation. We combined 18 years of data on dispatches, weather and fire danger and interviewed forestry workers to understand the spatial, temporal and weather distributions of these fires, and their underlying mechanisms. We estimate the average annual number of ignitions from forestry machinery in Sweden at 330–480 (2.0±0.4 ignitions per 1000ha clear-felling) of which 34.5 led to firefighter dispatches, constituting 2.2% of all forest fire dispatches and 40% of area burnt. Soil scarification causes the most ignitions and the main mechanism is likely high-inertia contact between discs and large stones, causing sparks igniting dry humus or moss, countering reports suggesting that such metal fragments cannot fulfil ignition requirements. We found a spatial relationship between forestry machine ignitions and abundance of large stones, represented by a Boulder Index generated from a nationwide dataset. Further, 75% of the dispatches occurred on days with relative humidity 26 and Fire Weather Index >12. 75% of the area burned when Fire Weather Index was >20. Results suggest machine-caused forest fires can be largely avoided by cancelling operations in stony terrain during high-risk weather.

This study evaluates the effects of the large 2007 Peloponnese (Greece) wildfires on changes in broadband surface albedo (α), daytime land surface temperature (LSTd) and night-time LST (LSTn) using a 2-year post-fire time series of Moderate Resolution Imaging Spectroradiometer satellite data. In addition, it assesses the potential of remotely sensed α and LST as indicators for fire–burn severity. Immediately after the fire event, mean α dropped up to 0.039 (standard deviation = 0.012) (P

Climate change will drive significant changes in annual area burned (burning rates) in the boreal forest although the trends, which are highly variable among studies, which may be caused by model specifications. In order to investigate this, we used 100 models predicting burning rates that are based on two predictor datasets (annual or 30-year averages) and five statistical algorithms (generalised linear model (GLM), random forest, gradient-boosted model (GBM), regression trees, multivariate adaptive regression splines (MARS)) to build a consensus model projecting future burning rates in boreal Canada with three global climate models (GCMs) (CanESM2, HadGEM and MIROC) and three anthropogenic climate forcing scenarios (RCP 2.6, RCP 4.5 and RCP 8.5). Results of the ensemble models were then used to quantify and map the uncertainty created by model specifications. The consensus model projects strong increase (>4-fold by 2080s) in burning rates, particularly under high climate-forcing scenarios. Even with very high goodness-of-fit in the consensus model, the model-specification uncertainty for future periods (>200%) could still be much higher than that of different GCMs and RCP scenarios. When tallied, we show that the total uncertainty could greatly hinder our ability to detect significant trends in burning rates for much of Canada at the end of the 21st century.

Increased fire frequency, extent and severity are expected to strongly affect the structure and function of boreal forest ecosystems. In this study, we examined 213 plots in boreal forests dominated by black spruce (Picea mariana) or jack pine (Pinus banksiana) of the Northwest Territories, Canada, after an unprecedentedly large area burned in 2014. Large fire size is associated with high fire intensity and severity, which would manifest as areas with deep burning of the soil organic layer (SOL). Our primary objectives were to estimate burn depth in these fires and then to characterise landscapes vulnerable to deep burning throughout this region. Here we quantify burn depth in black spruce stands using the position of adventitious roots within the soil column, and in jack pine stands using measurements of burned and unburned SOL depths. Using these estimates, we then evaluate how burn depth and the proportion of SOL combusted varies among forest type, ecozone, plot-level moisture and stand density. Our results suggest that most of the SOL was combusted in jack pine stands regardless of plot moisture class, but that black spruce forests experience complete combustion of the SOL only in dry and moderately well-drained landscape positions. The models and calibrations we present in this study should allow future research to more accurately estimate burn depth in Canadian boreal forests.

Samples of Scots pine (Pinus sylvestris L.) humus were burned under different moisture and fuel load scenarios to model humus consumption. For moisture levels below 120% on a dry mass basis, a parabolic increase of humus remaining with increasing moisture content was observed while, for higher moisture levels up to 300%, humus was reduced by a constant 10–15% on a dry mass basis. Both fuel load and humus moisture had a highly significant influence on humus consumption. Humus gross calorific value of Scots pine (19 509 KJ kg–1) is lower than that of other pine species. We found a desorption time-lag for humus moisture of 85 h in this study. Field data show a steady accumulation of humus in Central European Scots pine stands (up to 45 t ha–1 in 120-year-old stands). Amounts of litter remain constant over the different stand ages (~15 t ha–1). This study provides important information to predict humus consumption in Scots pine stands. The results can be used to build a fire severity and post-fire succession model for Scots pine stands in Central Europe.

McArthur’s Forest Fire Danger Index (FFDI) incorporates the Keetch–Byram Drought Index (KBDI) estimate of soil dryness. Improved approaches for estimating soil moisture now exist, with potential for informing the calculation of FFDI. We evaluated the effect, compared with KBDI, of two alternative methods of estimating soil moisture: the rainfall-based Antecedent Precipitation Index and soil moisture from the Soil Moisture Ocean Salinity satellite mission. These methods were used to calculate FFDI over a sample period of 5years (2010–14) at seven locations around Australia. The effect of substituting the alternatives for KBDI, and of entirely replacing the Drought Factor (DF) (a measure of fuel availability in FFDI) with the alternatives was explored by studying the effect on magnitude, distribution and timing of FFDI and associated Fire Danger Rating (FDR). Both approaches predicted drier soil conditions than KBDI, resulting in fewer Low–Moderate FDR days and more days of High FDR and above. The alternative methods replacing KBDI had little effect on seasonal patterns of FDR. Of all approaches, replacing DF entirely with the soil moisture alternatives most closely mimicked McArthur’s FFDI. Overall, if alternative measures of soil moisture are adopted for FFDI, the entire replacement of the DF term should be considered.

There is considerable variation in the degree of burn severity in boreal fires. One approach that has been used to capture this variation from field and remote sensing perspectives for western Canadian boreal forests is the Composite Burn Index (CBI) and differenced Normalized Burn Ratio (dNBR). Of interest was how well these methods may perform for fires in eastern Canada. This study investigated the CBI-dNBR relationship for selected fires in the eastern boreal forests of Canada, with a view towards contributing to the generalisation of a Canada-wide model. Results for the sampled region showed no difference in the CBI-dNBR relationship between black spruce- and jack pine-dominated stands, whereas this relationship was best described by a Generalised Additive Model (GAM). The dNBR-derived maps would also be useful in support of research and post-fire management in burns outside the studied territory and time frame covered by the existing burn severity mapping system already used in this region. The Saturated growth model proposed for the western boreal region also performed well for our eastern boreal region, thus further supporting the development of a national model.

This study documents cone opening and natural regeneration of jack pine (Pinus banksiana Lamb.) after burning live and dead stands similar to those killed by the mountain pine beetle (Dendroctonus ponderosae). Trees were killed by girdling in May and were burned in late July, 26 months later. Pairs of live and dead plots were simultaneously burned using three types of fire: surface, intermittent crown and continuous crown fires. Each type of fire was replicated three times; the nine pairs of burns were completed in a 4-day period. After fire, more cones were opened on dead trees than live trees. On dead trees, there was cone opening even when fire charred only the lower part of the bole. Three years after burning, dead stands with continuous crown fires had some of the densest regeneration and the highest rates of stocking. Across all burns in this study, seedling regeneration was best in shallow residual duff and in the more intensely burned plots. Without burning, there was virtually no regeneration 5 years after mortality. The results also show that burning, especially under continuous crown fire, could be used to promote regeneration in dead stands.

We applied logistic regression and Random Forest to evaluate drivers of fire occurrence on a provincial scale. Potential driving factors were divided into two groups according to scale of influence: ‘climate factors’, which operate on a regional scale, and ‘local factors’, which includes infrastructure, vegetation, topographic and socioeconomic data. The groups of factors were analysed separately and then significant factors from both groups were analysed together. Both models identified significant driving factors, which were ranked in terms of relative importance. Results show that climate factors are the main drivers of fire occurrence in the forests of Fujian, China. Particularly, sunshine hours, relative humidity (fire seasonal and daily), precipitation (fire season) and temperature (fire seasonal and daily) were seen to play a crucial role in fire ignition. Of the local factors, elevation, distance to railway and per capita GDP were found to be most significant. Random Forest demonstrated a higher predictive ability than logistic regression across all groups of factors (climate, local, and climate and local combined). Maps of the likelihood of fire occurrence in Fujian illustrate that the high fire-risk zones are distributed across administrative divisions; consequently, fire management strategies should be devised based on fire-risk zones, rather than on separate administrative divisions.

Prescribed burning is frequently advocated as a means of managing habitat for threatened species. We studied effects of fire on the quokka (Setonix brachyurus), a species currently used as a focal species for planning prescribed burns in the southern forests of Western Australia. We examined (i) the recolonisation of burnt areas; (ii) the refuge value of unburnt vegetation; and (iii) fire prediction variables that may help to guide fire planning to achieve desired habitat management outcomes. We hypothesised that fire regimes promoting vegetation structure and patchiness of burnt and unburnt vegetation would result in more rapid recolonisation of burnt areas by quokkas. Occupancy modelling identified the most important variables for recolonisation as retention of vertical vegetation structure and multiple unburnt patches across >20% of the total area. These outcomes were associated with high surface moisture, low soil dryness and slow fire rates of spread. Intense wildfire resulted in complete loss of vegetation structure and a lack of unburnt patches, which contributed to these areas remaining uncolonised. Burning with high moisture differentials, maximising the effectiveness of edaphic barriers to fire, retaining unburnt vegetation and maintaining vegetation structure were found to be important elements of fire regimes in this region.

Burn severity products created by the Monitoring Trends in Burn Severity (MTBS) project were used to analyse historical trends in burn severity. Using a severity metric calculated by modelling the cumulative distribution of differenced Normalized Burn Ratio (dNBR) and Relativized dNBR (RdNBR) data, we examined burn area and burn severity of 4893 historical fires (1984–2010) distributed across the conterminous US (CONUS) and mapped by MTBS. Yearly mean burn severity values (weighted by area), maximum burn severity metric values, mean area of burn, maximum burn area and total burn area were evaluated within 27 US National Vegetation Classification macrogroups. Time series assessments of burned area and severity were performed using Mann–Kendall tests. Burned area and severity varied by vegetation classification, but most vegetation groups showed no detectable change during the 1984–2010 period. Of the 27 analysed vegetation groups, trend analysis revealed burned area increased in eight, and burn severity has increased in seven. This study suggests that burned area and severity, as measured by the severity metric based on dNBR or RdNBR, have not changed substantially for most vegetation groups evaluated within CONUS.

Several post-wildfire debris flows and other landslides occurred after the extreme wildfire season of 2003 in the southern interior of British Columbia. Such events had not been previously reported in Canada, although they are common in lower latitudes. Severe wildfire seasons also were experienced in 2007 and 2009, and additional events were observed in four fires. Post-wildfire landslides have occurred in spring, summer and fall (autumn); events have been triggered by spring snowmelt, high-intensity summer rainstorms and low-intensity fall rainstorms. Of a total of 36 documented events, 23 were debris flows, and the most common initiating mechanism was high peak flow in channels. Most sediment in these events was derived from the channels, not from erosion in burned areas. Seven of the events were infiltration-triggered debris slides, and six events were debris floods. A variety of hydrologic changes can contribute to the prevalence of post-wildfire landslides and floods, including an increase in snowmelt rate. High-severity burn in catchment headwaters above steep channels is a topographic factor favouring debris flow occurrence. These observations demonstrate that the likelihood of debris flows and other mass-movement events in susceptible terrain is significantly increased following severe wildfire in this snow-dominated environment.

Sagebrush steppe of North America is considered highly imperilled, in part owing to increased fire frequency. Sagebrush ecosystems support numerous species, and it is important to understand those factors that affect rates of post-fire sagebrush recovery. We explored recovery of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) and basin big sagebrush (A. tridentata ssp. tridentata) communities following fire in the northern Columbia Basin (Washington, USA). We sampled plots across 16 fires that burned in big sagebrush communities from 5 to 28 years ago, and also sampled nearby unburned locations. Mixed-effects models demonstrated that density of large–mature big sagebrush plants and percentage cover of big sagebrush were higher with time since fire and in plots with more precipitation during the winter immediately following fire, but were lower when precipitation the next winter was higher than average, especially on soils with higher available water supply, and with greater post-fire mortality of mature big sagebrush plants. Bunchgrass cover 5 to 28 years after fire was predicted to be lower with higher cover of both shrubs and non-native herbaceous species, and only slightly higher with time. Post-fire recovery of big sagebrush in the northern Columbia Basin is a slow process that may require several decades on average, but faster recovery rates may occur under specific site and climate conditions.

Forests deliver a number of important ecosystem services, including clean water. When forests are disturbed by wildfire, the timing, quantity and quality of runoff are altered. A modelling study was conducted in a forested watershed in California, USA, to determine the risk of wildfire, and the potential post-fire sediment delivery from ~4-ha hillslope polygons within a 1500-km2 basin following a wildfire event. Wildfire intensity was estimated with fire spread models. The estimation of soil burn severity was based on predicted flame length. Sediment delivery was estimated from each hillslope polygon using a Geographic Information System erosion model. Polygons that generated the greatest amount of sediment, affected other values at risk in the basin, or were critical for reducing fire spread were ‘treated’ by reducing the amount and type of fuel available for a wildfire. The fire and erosion models were run a second time for treated conditions to see whether the treatment resulted in a reduced fire intensity and probability, and hence a reduced erosion rate. The estimated erosion rates the first year after the fire dropped from 46 Mg ha–1 before treatment to 26 Mg ha–1 for polygons that had received fuel treatments.

Variable-retention harvesting in lodgepole pine offers an alternative to conventional, even-aged management. This harvesting technique promotes structural complexity and age-class diversity in residual stands and promotes resilience to disturbance. We examined fuel loads and potential fire behaviour 12 years after two modes of variable-retention harvesting (dispersed and aggregated retention patterns) crossed by post-harvest prescribed fire (burned or unburned) in central Montana. Results characterise 12-year post-treatment fuel loads. We found greater fuel load reduction in treated than untreated stands, namely in the 10- and 100-h classes (P = 0.002 and 0.049 respectively). Reductions in 1-h (P

Forest die-offs associated with drought and heat have recently occurred across the globe, raising concern that associated changes in fuels and microclimate could link initial die-off disturbance to subsequent fire disturbance. Despite widespread concern, little empirical data exist. Following forest die-off in the Northern Jarrah Forest, south-western Australia, we quantified fuel dynamics and associated microclimate for die-off and control plots. Sixteen months post die-off, die-off plots had significantly increased 1-h fuels (11.8 vs 9.8 tonnes ha–1) but not larger fuel classes (10-h and 100-h fuels). Owing to stem mortality, die-off plots had significantly greater standing dead wood mass (100 vs 10 tonnes ha–1), visible sky (hemispherical images analysis: 31 vs 23%) and potential near-ground solar radiation input (measured as Direct Site Factor: 0.52 vs 0.34). Supplemental mid-summer microclimate measurements (temperature, relative humidity and wind speed) were combined with long-term climatic data and fuel load estimates to parameterise fire behaviour models. Fire spread rates were predicted to be 30% greater in die-off plots with relatively equal contributions from fuels and microclimate, highlighting need for operational consideration by fire managers. Our results underscore potential for drought-induced tree die-off to interact with subsequent fire under climate change.

Using Landsat imagery, this study was conducted to evaluate a fire disturbance that occurred in Canada’s Grasslands National Park on 27 April 2013. We used spectral indices (e.g. Normalised Burn Ratio (NBR) and Mid-infrared Burn Index (MIRBI)) derived from Landsat images to evaluate burn severity and to analyse the vegetation recovery process. A field survey was conducted to assess burn severity, which we used to evaluate the performance of spectral indices. Responses of the vegetation community to the fire disturbance were also investigated during the field campaign. Results show that the selected spectral indices performed differently for evaluating burn severity, but MIRBI performed best, likely due to its ability to discriminate post-fire residuals. Severely burned areas were distributed along a river where a larger amount of senesced biomass had accumulated before the fire. The semiarid grasslands showed a strong resilience to fire disturbance, and vegetation recovery was likely influenced by burn severity and water availability. Different vegetation types (e.g. grass, trees and shrubs) had distinct recovery rates and, thus, fire influences plant community development. The fire disturbance changed the composition of grass species in the burned area and also promoted invasion by non-native species.

The savanna biome has the greatest burned area globally. Whereas the global distribution of most biomes can be predicted successfully from climatic variables, this is not so for savannas. Attempts to dynamically model the distribution of savannas, including a realistically varying tree : grass ratio are fraught with difficulties. In a simulation study using the dynamic vegetation model LPJ-GUESS we investigate the effect of fire on the tree : grass ratios as well as the biome distribution on the African continent. We performed simulations at three spatial scales: locally, at four sites inside Kruger National Park (South Africa); regionally, along a precipitation gradient; and for the African continent. We evaluated the model using results of a fire experiment and found that the model underestimates the effect of fire on tree cover slightly. On a regional scale, high frequencies were able to prevent trees from outcompeting grasses in mesic regions between ~700 and 900 mm mean annual precipitation. Across the African continent, incorporation of fire improved notably the simulated distribution of the savanna biome. Our model results confirm the role of fire in determining savanna distributions, a notion that has been challenged by competing theories of tree–grass coexistence.

A recent study by Davies et al. sought to test whether winter grazing could reduce wildfire size, fire behaviour and intensity metrics, and fire-induced plant mortality in shrub–grasslands. The authors concluded that ungrazed rangelands may experience fire-induced mortality of native perennial bunchgrasses. The authors also presented several statements regarding the benefits of winter grazing on post-fire plant community responses. However, we contend that the study by Davies et al. has underlying methodological errors, lacks data necessary to support their conclusions, and does not provide a thorough discussion on the effect of grazing on rangeland ecosystems. Importantly, Davies et al. presented no data on the post-fire mortality of the perennial bunchgrasses or on the changes in plant community composition following their experimental fires. Rather, Davies et al. inferred these conclusions based on their observed fire behaviour metrics of maximum temperature and a term described as the ‘heat load’. However, we contend that neither metric is appropriate for describing the heat flux impacts on plants. This lack of post-fire data, several methodological errors and the use of inappropriate thermal metrics limit the authors’ ability to support their stated conclusions.

Fire can result in hydro–geomorphic changes that are spatially variable and difficult to predict. In this research note we compile 294 infiltration measurements and 10 other soil, catchment runoff and erosion datasets from the eastern Victorian uplands in south-eastern Australia and argue that higher aridity (a function of the long-term mean precipitation and net radiation) is associated with lower post-fire infiltration capacities, increasing the chance of surface runoff and strongly increasing the chance of debris flows. Post-fire debris flows were only observed in the more arid locations within the Victorian uplands, and resulted in erosion rates more than two orders of magnitude greater than non-debris flow processes. We therefore argue that aridity is a high-order control on the magnitude of post-wildfire hydro–geomorphic processes. Aridity is a landscape-scale parameter that is mappable at a high resolution and therefore is a useful predictor of the spatial variability of the magnitude of post-fire hydro–geomorphic responses.

Several aspects of wildland fire are moderated by site- and landscape-level vegetation changes caused by previous fire, thereby creating a dynamic where one fire exerts a regulatory control on subsequent fire. For example, wildland fire has been shown to regulate the size and severity of subsequent fire. However, wildland fire has the potential to influence other properties of subsequent fire. One of those properties – the extent to which a previous wildland fire inhibits new fires from igniting and spreading within its perimeter – is the focus of our study. In four large wilderness study areas in the western United States (US), we evaluated whether or not wildland fire regulated the ignition and spread (hereafter occurrence) of subsequent fire. Results clearly indicate that wildland fire indeed regulates subsequent occurrence of fires ≥ 20 ha in all study areas. We also evaluated the longevity of the regulating effect and found that wildland fire limits subsequent fire occurrence for nine years in the warm/dry study area in the south-western US and over 20 years in the cooler/wetter study areas in the northern Rocky Mountains. Our findings expand upon our understanding of the regulating capacity of wildland fire and the importance of wildland fire in creating and maintaining resilience to future fire events.

Hydrologic response to rainfall on fragmented or burnt hillslopes is strongly influenced by the ensuing connectivity of runoff and erosion processes. Yet cross-scale process connectivity is seldom evaluated in field studies owing to scale limitations in experimental design. This study quantified surface susceptibility and hydrologic response across point to hillslope scales at two degraded unburnt and burnt woodland sites using rainfall simulation and hydrologic modelling. High runoff (31–47 mm) and erosion (154–1893 g m–2) measured at the patch scale (13 m2) were associated with accumulation of fine-scale (0.5-m2) splash-sheet runoff and sediment and concentrated flow formation through contiguous bare zones (64–85% bare ground). Burning increased the continuity of runoff and sediment availability and yield. Cumulative runoff was consistent across plot scales whereas erosion increased with increasing plot area due to enhanced sediment detachment and transport. Modelled hillslope-scale runoff and erosion reflected measured patch-scale trends and the connectivity of processes and sediment availability. The cross-scale experiments and model predictions indicate the magnitude of hillslope response is governed by rainfall input and connectivity of surface susceptibility, sediment availability, and runoff and erosion processes. The results demonstrate the importance in considering cross-scale structural and functional connectivity when forecasting hydrologic and erosion responses to disturbances.

No records exist in the scientific literature about lightning fires in the eastern Mediterranean (EM). Although thunderstorms are frequent in winter, if spontaneous fire is ignited, it will immediately be extinguished by rain. No thunderstorms occur in summer, and therefore no favourable weather conditions for natural ignitions exist. In October 2014, the synoptic conditions over the EM comprised a Red Sea Trough (RST) with an easterly axis (a less frequent version of this system). A convective storm, accompanied by thunderstorms with intense local rains developed rapidly. Simultaneously, six wildfires were reported from different locations in northern Israel (in the EM). Lightning activity documented by the Israel Electric Co. was at the same time and locations as the reported wildfires. To the best of our knowledge, this is the first case recorded in recent history of wildfires in the EM as a result of lightning. Moreover, in the literature, the RST is associated with fires only when its axis is in a western position, thus driving very hot and dry air masses. A different way of thinking is needed on the potential of lightning in autumn as a possible cause of fires under different situations of the RST.

This paper presents a series of improvements to the quantitative modelling of burned areas in Europe under historical climate. The Standalone Fire Model (SFM) based on a state-of-the-art large scale mechanistic fire modelling algorithm is used to reproduce historical burned areas reported in the two publicly available datasets – European Forest Fire Information System (EFFIS) and Global Fire Emissions Database (GFED). The most recent versions of these sources allow a broader validation of SFM’s modelled burned areas at a country level. Our analysis is carried out for the years 2000–2008 for 17 European countries utilising both EFFIS and GFED datasets for model benchmarking. We suggest improving the original model by modifying the fire probability function reflecting fuel moisture. This modification allows for a dramatic improvement of accuracy in modelled burned areas for a range of European countries. We also explore in detail a pixel-level parametrisation of firefighting efficiency in SFM along with modifications of the biomass map. In comparison with the aggregated country-level approach, the advantages of the finer calibration are quite minor for the most recent version of the GFED dataset. Overall, the annual burned areas modelled by this improved SFM version are in good agreement with historical observations.

A lack of independent, quality-assured data prevents scientists from effectively evaluating predictions and uncertainties in fire models used by land managers. This paper presents a summary of pre-fire and post-fire fuel, fuel moisture and surface cover fraction data that can be used for fire model evaluation and development. The data were collected in the south-eastern United States on 14 forest and 14 non-forest sample units associated with 6 small replicate and 10 large operational prescribed fires conducted during 2008, 2011, and 2012 as part of the Prescribed Fire Combustion and Atmospheric Dynamics Research Experiment (RxCADRE). Fuel loading and fuel consumption averaged 6.8 and 4.1 Mg ha–1 respectively in the forest units and 3.0 and 2.2 Mg ha–1 in the non-forest units. Post-fire white ash cover ranged from 1 to 28%. Data were used to evaluate two fuel consumption models, CONSUME and FOFEM, and to develop regression equations for predicting fuel consumption from ash cover. CONSUME and FOFEM produced similar predictions of total fuel consumption and were comparable with measured values. Simple linear models to predict pre-fire fuel loading and fuel consumption from post-fire white ash cover explained 46 and 59% of variation respectively.

Fire suppression has altered the historical mixed-severity fire regime and homogenised forest structures in Jasper National Park, Canada. We used dendrochronology to reconstruct fire history and assess forest dynamics at 29 sites in the montane forests. Based on fire scars and even-aged post-fire cohorts, we determined 18 sites had mixed-severity fire histories through time, and 11 sites had evidence of high-severity fires only – yielding a mixed-severity fire regime for the study area. Lodgepole pine, hybrid spruce and Douglas-fir established simultaneously after low- and high-severity fires. Regardless of fire history, forest canopies were mixed in composition and subcanopies were strongly dominated by shade-tolerant hybrid spruce. Despite their size, subcanopy trees were similar in age to the canopy trees. Current stand composition and age structures largely reflect the effects of high-severity fires that burned ~110 years ago at 18 of 29 sites. In the absence of fires after 1905, forests have matured simultaneously, homogenising the landscape and resulting in forest structures that are more conducive to high-severity fire than are fires of a range of severities. Proactive fire management is justified to restore fire as a vital ecological process and promote forest resilience by countering the effects of a century of fire suppression.

In this paper we analyse the extent of fire-induced forest degradation in Mato Grosso State, Brazil. We utilise a sample based approach used in a previous pan-tropical deforestation survey to derive information on land cover and burned areas in the two major biomes of Mato Grosso: Amazon and Cerrado. Land cover and burned area are mapped for three years (2000–2005–2010) over 77 sample sites (10 000 ha each) distributed systematically throughout the state which covers 90.337 Mha. Our results indicate continuing forest degradation by fires in the state and potentially increasing fire susceptibility of the Amazon forests, regardless of the decrease in deforestation. 2010 witnessed the most extensive fire-induced forest degradation (~300 000 ha) in the forests of the Amazon biome among the study years, regardless of the fact that the fire season was less severe than in 2005. Deforestation in the Amazon biome in Mato Grosso dropped from 590 000 ha year–1 in the 2000–2005 period to 190 000 ha year–1 in the second half of the decade. The findings of this study advocate the inclusion of forest fire effects into carbon accounting initiatives.

Wildland fire rate of spread (ROS) and intensity are determined by the mode and magnitude of energy transport from the flames to the unburned fuels. Measurements of radiant and convective heating and cooling from experimental fires are reported here. Sensors were located nominally 0.5 m above ground level. Flame heights varied from 0.3 to 1.8 m and flaming zone depth varied from 0.3 to 3.0 m. Fire ROS derived from observations of fire transit time between sensors was 0.10 to 0.48 m s–1. ROS derived from ocular estimates reached 0.51 m s–1 for heading fire and 0.25 m s–1 for backing fire. Measurements of peak radiant and total energy incident on the sensors during flame presence reached 18.8 and 36.7 kW m–2 respectively. Peak air temperatures reached 1159°C. Calculated fire radiative energy varied from 7 to 162 kJ m–2 and fire total energy varied from 3 to 261 kJ m–2. Measurements of flame emissive power peaked at 95 kW m–2. Average horizontal air flow in the direction of flame spread immediately before, during, and shortly after the flame arrival reached 8.8 m s–1, with reverse drafts of 1.5 m s–1; vertical velocities varied from 9.9 m s–1 upward flow to 4.5 m s–1 downward flow. The observations from these fires contribute to the overall understanding of energy transport in wildland fires.

An increase in mega-fires and wildfires is a global issue that is expected to become worse with climate change. Fuel treatments are often recommended to moderate behaviour and decrease severity of wildfires; however, the extensive nature of rangelands limits the use of many treatments. Dormant-season grazing has been suggested as a rangeland fuel treatment, but its effects on fire characteristics are generally unknown. We investigated the influence of dormant-season (winter) grazing by cattle (Bos taurus) on fuel characteristics, fire behaviour and area burned in Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis) shrub-grassland communities in south-eastern Oregon, USA. Winter grazing was applied for 5 years before burning and compared with ungrazed areas. Winter grazing decreased fine fuels and increased fine fuel moisture, which reduced flame height and depth, rate of spread and area burned. Winter-grazed areas also had lower maximum temperature and heat loading during fires than ungrazed areas, and thereby decreased risk of fire-induced mortality of important herbaceous functional groups. These results suggest that winter grazing may be a fuel management treatment that can be applied across vast shrub-grasslands to decrease wildfire risk and fire intensity to mediate climate change effects on wildfire activity.

The hydrological consequences of wildfires are among their most significant and long-lasting effects. As wildfire severity affects post-fire hydrological response, fuel treatments can be a useful tool for land managers to moderate this response. However, current models focus on only one aspect of the fire–watershed linkage (fuel treatments, fire behaviour, fire severity, watershed responses). This study outlines a spatial modelling approach that couples three models used sequentially to allow managers to model the effects of fuel treatments on post-fire hydrological responses. Case studies involving a planned prescribed fire at Zion National Park and a planned mechanical thinning at Bryce Canyon National Park were used to demonstrate the approach. Fuel treatments were modelled using FuelCalc and FlamMap within the Wildland Fire Assessment Tool (WFAT). The First Order Fire Effects Model (FOFEM) within WFAT was then used to evaluate the effectiveness of the fuel treatments by modelling wildfires on both treated and untreated landscapes. Post-wildfire hydrological response was then modelled using KINEROS2 within the Automated Geospatial Watershed Assessment tool (AGWA). This coupled model approach could help managers estimate the effect of planned fuel treatments on wildfire severity and post-wildfire runoff or erosion, and compare various fuel treatment scenarios to optimise resources and maximise mitigation results.

Wildfires pose complex challenges to policymakers and fire agencies. Fuel break networks and area-wide fuel treatments are risk-management options to reduce losses from large fires. Two fuel management scenarios covering 3% of the fire-prone Algarve region of Portugal and differing in the intensity of treatment in 120-m wide fuel breaks were examined and compared with the no-treatment option. We used the minimum travel time algorithm to simulate the growth of 150 000 fires under the weather conditions historically associated with large fires. Fuel break passive effects on burn probability, area burned, fire size distribution and fire transmission among 20 municipalities were analysed. Treatments decreased large-fire incidence and reduced overall burnt area up to 17% and burn probability between 4% and 31%, depending on fire size class and treatment option. Risk transmission among municipalities varied with community. Although fire distribution shifted and large events were less frequent, mean treatment leverage was very low (1 : 26), revealing a very high cost–benefit ratio and the need for engaging forest owners to act in complementary area-wide fuel treatments. The study assessed the effectiveness of a mitigating solution in a complex socioecological system, contributing to a better-informed wildland fire risk governance process among stakeholders.

We present a case study of the Las Conchas Fire (2011) to explore the role of previously burned areas (wildfires and prescribed fires) on suppression effectiveness and avoided exposure. Methodological innovations include characterisation of the joint dynamics of fire growth and suppression activities, development of a fire line effectiveness framework, and quantification of relative fire line efficiencies inside and outside of previously burned areas. We provide descriptive statistics of several fire line effectiveness metrics. Additionally, we leverage burn probability modelling to examine how burned areas could have affected fire spread potential and subsequent exposure of highly valued resources and assets to fire. Results indicate that previous large fires exhibited significant and variable impacts on suppression effectiveness and fire spread potential. Most notably the Cerro Grande Fire (2000) likely exerted a significant and positive influence on containment, and in the absence of that fire the community of Los Alamos and the Los Alamos National Laboratory could have been exposed to higher potential for loss. Although our scope of inference is limited results are consistent with other research, suggesting that fires can exert negative feedbacks that can reduce resistance to control and enhance the effectiveness of suppression activities on future fires.

A recent commentary by Smith et al. (2016) argues that our study (Davies et al. 2016) contained methodological errors and lacked data necessary to support our conclusions, in particular that winter grazing may reduce the probability of fire-induced mortality of bunchgrasses. Carefully reading Davies et al. (2016) and relevant literature provides strong evidence that the comments of Smith et al. are unfounded. Most notably, Smith et al. (2016) state that thermocouples placed in the air have no correlation to temperatures experienced by vegetation. However, in our study, thermocouples were placed inside the centre of meristematic crowns of bunchgrasses, as was clearly stated in the methods. Nowhere in the manuscript does it say that thermocouples were placed in the air. Duration of elevated temperatures has been repeatedly linked to an increased risk of fire-induced mortality of vegetation in the literature, contrary to claims by Smith et al. (2016) that no evidence of a relationship exists. The conclusion that winter grazing may decrease the likelihood of perennial bunchgrass mortality was not based solely on data collected in this experiment, but also Davies et al. (2009), where post-fire bunchgrass density and production in ungrazed areas were less than half those of grazed areas.

We conducted bird surveys in 10 of the first 11 years following a mixed-severity fire in a dry, low-elevation mixed-conifer forest in western Montana, United States. By defining fire in terms of fire severity and time-since-fire, and then comparing detection rates for species inside 15 combinations of fire severity and time-since-fire, with their rates of detection in unburned (but otherwise similar) forest outside the burn perimeter, we were able to assess more nuanced effects of fire on 50 bird species. A majority of species (60%) was detected significantly more frequently inside than outside the burn. It is likely that the beneficial effects of fire for some species can be detected only under relatively narrow combinations of fire severity and time-since-fire. Because most species responded positively and uniquely to some combination of fire severity and time-since-fire, these results carry important management implications. Specifically, the variety of burned-forest conditions required by fire-dependent bird species cannot be created through the application of relatively uniform low-severity prescribed fires, through land management practices that serve to reduce fire severity or through post-fire salvage logging, which removes the dead trees required by most disturbance-dependent bird species.