International Journal of Wildland Fire最新文献

Calculating greenhouse gas emissions from fires relies on estimation of available fuels at time of burn. Fuel accumulation and decomposition occur throughout the year, with seasonality of decomposition poorly researched in monsoonal Australia.

We investigate the decomposition and accumulation of litter fuels (leaves, twigs), and coarse woody debris (CWD >6 mm–<5 cm diameter) across a full monsoonal cycle.

The study was undertaken at three sites in long unburned (10 years+) eucalypts-dominated mesic savanna woodland. For measuring decomposition, twelve 50 g samples of leaves and twigs were placed in situ on the soil surface, with one sample removed and dried each month; one sample of CWD was tested after 12 months. Fine fuel accumulation was recorded monthly.

Significant statistical relationships were observed between soil moisture and leaf decomposition. Across the study period 66% of leaves, 35% of twig, and 27.2% of CWD decomposed. Fine fuel accumulation was consistent with previous studies and peaking in August. Combining monthly rates of accumulation and decomposition, net fine fuel loads were observed to be much greater late in the dry season.

The present study provides enhanced fine fuel load calculations by including seasonality of decomposition which allows for better estimates of emissions from savanna fires.

Wildfire fuels are commonly mapped via manual interpretation of aerial photos. Alternatively, RGB satellite imagery offers data across large spatial extents. A method of individual tree detection and classification is developed with implications to fuel mapping and community wildfire exposure assessments.

Convolutional neural networks are trained using a novel generational training process to detect trees in 0.50 m/px RGB imagery collected in Rocky Mountain and Boreal natural regions in Alberta, Canada by Pleiades-1 and WorldView-2 satellites. The workflow classifies detected trees as ‘green-in-winter’/‘brown-in-winter’, a proxy for coniferous/deciduous, respectively.

A k-fold testing procedure compares algorithm detections to manual tree identification densities reaching an R² of 0.82. The generational training process increased achieved R² by 0.23. To assess classification accuracy, satellite detections are compared to manual annotations of 2 cm/px drone imagery resulting in average F1 scores of 0.85 and 0.82 for coniferous and deciduous trees respectively. The use of model outputs in tree density mapping and community-scale wildfire exposure assessments is demonstrated.

The proposed workflow automates fine-scale overstorey tree mapping anywhere seasonal (winter and summer) 0.50 m/px RGB satellite imagery exists. Further development could enable the extraction of additional properties to inform a more complete fuel map.

Sustainable rangeland management balances production and conservation. While a broad literature describesthe conservation benefits of prescribed fire, benefits for livestock production have emerged more slowly. Mineral nutrition is important for livestock health and performance, but the impact of prescribed fire on mineral concentration of forages, especially in the northern US Great Plains, remains unknown.

We investigated how burning affects the mineral concentration of forage early and late in the growing season.

Data were collected on mixed-grass prairie in south-central North Dakota, USA. Vegetation was clipped from recently burned, 1 year post-fire, 2 years post-fire, and not-yet-burned patches at the same sampling points in spring and late summer. Samples were analysed for calcium, phosphorus, magnesium, potassium, copper, iron, manganese, and zinc concentration.

Burning increased forage mineral concentration across most minerals. Phosphorous, potassium, copper and zinc were higher in burned areas in late spring and summer; calcium, magnesium and manganese were only higher during the late summer; Late-season iron levels increased with time since fire.

Prescribed fire has a positive effect on forage mineral content.

Prescribed fire has the potential to reduce mineral supplementation costs and improve cow performance.

Assessment of fuel hazard has become the dominant method of describing Australian forest fuel complexes, despite a lack of evidence supporting the veracity of its underpinning assumptions.

To analyse and discuss the merits of fuel hazard ratings and scores in representing measurable fuel characteristics, such as fuel load and fire behaviour potential.

Published findings were reviewed, and available data analysed to investigate the validity of the Australian fuel hazard assessment concepts.

Multiple published studies showed the Australian fuel hazard assessment methods to be subjective and non-replicable. All available evidence shows no relationship between fuel hazard ratings and fuel quantity. No relationship between the ratings and fire behaviour potential was found.

The principles underpinning the use of fuel hazard ratings for fuel assessment were shown to be unfounded. The ratings cannot be converted into physical fuel characteristics or fire behaviour potential, and its application in Australian fire management is unwarranted.

The prediction of the propagation of wildland fires is an important socio-technical problem. Wildland fires are often initiated by small spot ignition sources and then spread to larger burning areas.

Experiments are conducted for the spotting ignition of a forest surface fuel (pine needles) in a relatively large (up to 1 m²), horizontal laboratory bed, and the subsequent fire spread without wind. The spotting ignition sources are a cluster of steel particles, an ember and a small pilot flame.

Wildfire spread has an initial acceleration phase, with the growth of the burned area in the fuel bed following a power law dependence in time, almost independent of the ignition source. Comparison with previous larger-scale experiments and FARSITE modelling of the fire spread over similar fuel beds shows that the power function with time describes well the combined results of the initial wildfire growth and the transition to larger fire propagation for relatively long times.

The Rothermel equation under different environmental conditions may be extended to describe the initial accelerative growth of a spot fire. This work supports the modelling of fire propagation that currently is geared to a later time in the development of a wildfire.

Live fuel comprises a significant portion of the fuel consumed in forest and scrub crown fires. However, its flammability remains poorly understood. Although live fuel differs from dead fuel in moisture content, chemical composition, cellular structure and physiological characteristics, its higher moisture content masks the effect of other characteristics on its flammability.

The aim of the study was to delineate and assess the effects of live/dead condition, moisture content and particle size on flammability of gorse (Ulex europaeus L.).

Live and dead gorse material of three size classes (0–3, 3–6, and 6–10 mm in diameter) at six moisture contents (0, 10, 25, 50, 75 and 100%) was tested in a cone calorimeter to evaluate its flammability using new sample preparation and moisture conditioning techniques.

On average, live fuel ignited 21% slower, reached 11% higher peak heat release rate, and had a 12% shorter burn duration than dead fuel of the same moisture content. These differences were most pronounced in coarser material.

For gorse, fine dead fuels increase the likelihood of ignition, fine live fuels contribute to high burning intensities, and coarser live and dead fuels prolong combustion.

These findings highlight the need to account for flammability differences between live and dead fuels in fire behaviour models beyond those driven by variations in moisture content.

Climate projections signal longer fire seasons and an increase in the number of dangerous fire weather days for much of the world including Australia.

Here we argue that heatwaves, dynamic fire–atmosphere interactions and increased fuel availability caused by drought will amplify potential fire behaviour well beyond projections based on calculations of afternoon forest fire danger derived from climate models.

We review meteorological dynamics contributing to enhanced fire behaviour during heatwaves, drawing on examples of dynamical processes driving fire behaviour during the Australian Black Summer bushfires of 2019–20.

Key dynamical processes identified include: nocturnal low-level jets, deep, unstable planetary boundary layers and fire–atmosphere coupling.

The future scenario we contend is long windows of multi-day fire events where overnight suppression is less effective and fire perimeters will expand continuously and aggressively over multiple days and nights.

Greater overnight fire activity and multi-day events present strategic and tactical challenges for fire management agencies including having to expand resourcing for overnight work, manage personnel fatigue and revise training to identify conditions conducive to unusually active fire behaviour overnight. Effective messaging will be critical to minimise accidental fire ignition during heatwaves and to alert the community to the changing fire environment

Every year, people in Canada are evacuated due to wildland fires to avoid death, injury, and illness from fire and smoke events.

In this paper, we provide an overview of evacuations recorded in the Canadian Wildland Fire Evacuation Database between 1980 and 2021.

Our analysis covers evacuations in Canada from 1980 to 2021. We provide summary statistics including number of evacuations and evacuees, evacuation duration, seasonality, evacuation causes, community types, structure losses, and fatalities. We also investigate temporal and spatial patterns.

Between 1980 and 2021, there were 1393 wildland fire evacuation events with 576,747 people evacuated. During this period, there was an overall increase in frequency of evacuations, number of evacuees, and duration of events. Structure loss occurred during 194 evacuation events, with 4105 homes burned. We estimate wildland fire evacuations cost at least CAD3.7 billion (excluding structural losses), jumping to CAD4.6 billion if we include productivity losses. Indigenous peoples are disproportionately impacted in wildfire evacuations compared to the general Canadian population.

Wildland fire evacuations continue to occur across Canada and are increasing.

The findings from this study give us a better understanding of the characteristics of wildland fire evacuations, which can help guide emergency management.

Global environmental and social change are pushing wildfire activity and impact beyond known trajectories. Here, we conducted a targeted review to distill five wildfire challenges that we argue form opportunities for their governance (research aim 1). We exemplified our arguments by drawing from the case of Cyprus (research aim 2), a small island country in the south-east European Mediterranean Basin at risk of extreme wildfire impact. Findings indicate that burning for social and ecological resource benefits, innovative management paradigms and anticipatory governance systems offer actionable solutions to the wildfire paradox and the limits of suppression. Local adaptive institutions and a reconceptualisation of wildfire as a risk and process beyond technocratic interpretations are necessary to account for broader social conditions shaping wildfire regimes and community impact. Governance systems that accommodate collective action have proven suitable to address multiple wildfire complexities linked with different socio-economic systems and values. A systematic literature review, policy review, and qualitative data collection on wildfire management in Cyprus track back to the initial framing. Our case study offers insights for tackling wildfires with actionable steps through overarching governance systems, and illustrates the potential for change in thinking of and acting on wildfire in flammable landscapes globally.

Reptile responses to fire may differ between remnants and contiguous vegetation but this is poorly understood.

We aimed to explore long-term (≤15 years) post-fire responses of reptiles in an urban Banksia woodland remnant.

We trapped reptiles for 10 nights in November and December each year between 2009 and 2023 inclusive (except 2014 and 2019) to estimate relative abundance. We used mixed models to explore differences between unburnt and burnt sites and changes in both over time.

The reptile community showed short-term negative responses to fire, but communities had returned to their pre-fire state within 3 years. Two species showed short-term (3 and 5 years respectively) negative responses to fire while two species showed positive responses; one in the first year post-fire only, and the other in sites >8 years post-fire. There did not appear to be consistent differences in fire responses between this study and studies conducted in contiguous Banksia woodlands, although differences in study designs renders this conclusion equivocal.

Reptile communities in Banksia woodland remnants, and the species they contain appear to be relatively robust to a wide range of fire regimes.