EISSN : 25716255
Current Publisher: MDPI (10.3390)
Total articles ≅ 168
Latest articles in this journal
Fire, Volume 3; doi:10.3390/fire3040058
Algeria has high wildfire activity, albeit restricted to the northern coastal fringe. However, no study has investigated why fire is restricted to that area, and what combination of factors explains the occurrence of wildfires. Here, we describe the current fire regime of Northern Algeria from 2000 to 2019 and we correlate fire activity to a range of environmental and anthropic drivers. We found a strong north–south gradient in fire occurrence: it is maximal in the high-fueled (productive) oak forests of Northern Algeria with high annual rainfall amount, whereas it is fuel-limited in the South due to semi-arid conditions. We determined that fire is nearly absent where the bioclimate is subarid or arid, due to the steppic vegetation with summer Normalized Difference Vegetation Index (NDVI) values below 0.35. Therefore, fire occupies a narrow niche in space (the humid and subhumid areas with high productivity) and in time as most fires occur in summer after the high rainfalls from fall to spring that promote fuel growth. Humans also play a role as fire hotspots are concentrated in croplands and in built-up areas with high human density and infrastructures mixed with shrublands and forests. We discuss how the ongoing climate changes and the desertification progressing towards the North of Algeria may finally restrict forests to a narrow fringe providing less and less ecological services to the Algerian people.
Fire, Volume 3; doi:10.3390/fire3040057
On 17 June 2017, one of the most dramatic and destructive wildfires in Portugal’s History started, formed by a complex of at least five wildfires that merged together burning more than 45,000 hectares. In its aftermath, 66 persons lost their lives, most of them trying to run away from the fire, more than 250 were injured, and over 1000 structures (including 263 residential homes) were damaged or destroyed, with direct losses estimated at around 200 million euros. Shortly after the fire was extinguished, and as part of a larger analysis, the authors performed exhaustive field work to assess the fire impact on all manmade structures in the area of the Pedrógão Grande fire. A specific geodatabase was built, accounting for an extensive set of parameters aimed at characterizing: (i) The structure, (ii) the surroundings of the structure, and (iii) the arrival and impact of the fire. A total of 1043 structures were considered for the analysis, mostly support structures, like sheds or storage (38.6%), but also around 25% of dwellings (13.3% primary and 11.9% secondary). Regarding the ignitions, more than 60% of the structures were ignited due to the deposition of firebrands in different weak points. In addition, more than 60% of these ignitions occurred on the roofs, mainly because of the vulnerability associated with the structures and materials supporting them. Despite these results, and from what we observed on the structures that were not destroyed, we still consider that for the Portuguese reality houses are a good refuge, providing that they and their surroundings are managed and kept in good conditions.
Fire, Volume 3; doi:10.3390/fire3040056
The combination of drought and fire can cause drastic changes in forest composition and structure. Given the predictions of more frequent and severe droughts and forecasted increases in fire size and intensity in the western United States, we assessed the impact of drought and different fire intensities on Pinus ponderosa saplings. In a controlled combustion laboratory, we exposed saplings to surface fires at two different fire intensity levels (quantified via fire radiative energy; units: MJ m−2). The recovery (photosynthesis and bud development) and mortality of saplings were monitored during the first month, and at 200- and 370-days post-fire. All the saplings subjected to high intensity surface fires (1.4 MJ m−2), regardless of the pre-fire water status, died. Seventy percent of pre-fire well-watered saplings recovered after exposure to low intensity surface fire (0.7 MJ m−2). All of the pre-fire drought-stressed saplings died, even at the lower fire intensity. Regardless of the fire intensity and water status, photosynthesis was significantly reduced in all saplings exposed to fire. At 370 days post-fire, burned well-watered saplings that recovered had similar photosynthesis rates as unburned plants. In addition, all plants that recovered or attempted to recover produced new foliage within 35 days following the fire treatments. Our results demonstrate that the pre-fire water status of saplings is an important driver of Pinus ponderosa sapling recovery and mortality after fire.
Fire, Volume 3; doi:10.3390/fire3040055
Firebrands are an important agent of wildfire spread and structure fire ignitions at the wildland urban interface. Bark flake morphology has been highlighted as an important yet poorly characterized factor in firebrand generation, transport, deposition, and ignition of unburned material. Using pine species where bark flakes are the documented source of embers, we conducted experiments to investigate how bark structure changes in response to diurnal drying. Over a three-day period in a longleaf pine (Pinus palustris Mill.) stand in Florida, we recorded changes in temperature, moisture content, and structure of bark across different facing aspects of mature pine trees to examine the effects of varying solar exposure on bark moisture. We further compared results to bark drying in a pitch pine (Pinus rigida Mill.) plantation in New Jersey. Under all conditions, bark peeled and lifted away from the tree trunk over the study periods. Tree bole aspect and the time of day interacted to significantly affect bark peeling. General temperature increases and moisture content decreases were significantly different between east and west aspects in pitch pine, and with time of day and aspect in longleaf pine. These results illustrate that bark moisture and flakiness is highly dynamic on short time scales, driven largely by solar exposure. These diurnal changes likely influence the probability of firebrand production during fire events via controls on moisture (ignition) and peeling (lofting).
Fire, Volume 3; doi:10.3390/fire3040054
Disentangling the relative importance of habitat filtering and dispersal limitations at local scales (2) in shaping species composition remains an important question in community ecology. Previous studies have examined the relative importance of these mechanisms using topography and selected soil properties. We examined both topography and edaphic properties from 160 locations in the recently burned 25.6 ha Yosemite Forest Dynamics Plot (YFDP) in Yosemite National Park, California, USA. In addition to eight soil chemical properties, we included phosphatases and urease enzymes in a definition of habitat niches, primarily because of their rapid changes with fire (compared to soil nutrients) and also their role in ecosystem function. We applied environmental variables to the distributions of 11 species. More species–habitat associations were defined by soil properties (54.5%) than topographically-defined habitat (45.4%). We also examined the relative importance of spatial and environmental factors in species assemblage. Proportions explained by spatial and environmental factors differed among species and demographic metrics (stem abundance, basal area increment, mortality, and recruitment). Spatial factors explained more variation than environmental factors in stem abundance, mortality, and recruitment. The contributions of urease and acid phosphatase to habitat definition were significant for species abundance and basal area increment. These results emphasize that a more complete understanding of niche parameters is needed beyond simple topographic factors to explain species habitat preference. The stronger contribution of spatial factors suggests that dispersal limitation and unmeasured environmental variables have high explanatory power for species assemblage in this coniferous forest.
Fire, Volume 3; doi:10.3390/fire3030053
Wildfires are a common disturbance in boreal regions and have the potential to affect the waterborne export of organic matter and nutrients from burned catchments. To understand the effect of fire on shallow groundwater chemistry in a forested peatland in northern Alberta, Canada, shallow groundwater monitoring wells were sampled before and after a prescribed burn. The samples were collected from control and treatment wells between May and August 2019. The results indicate no differences in dissolved organic matter concentration and chemical composition between wells in burned and unburned sections but substantially increased nutrient concentrations were found in the burned section. Here, the levels of phosphorus increased and did not return to pre-fire levels at the end of the monitoring period, while the levels of inorganic nitrogen increased and returned to pre-fire levels within a few months. With increasing wildfire activity, or as a result of prescribed burns in the Boreal Plains, we may see implications for downstream water quality, including lake trophic status.
Fire, Volume 3; doi:10.3390/fire3030052
Escape routes keep firefighters safe by providing efficient evacuation pathways from the fire line to safety zones. Effectively utilizing escape routes requires a precise understanding of how much time it will take firefighters to traverse them. To improve this understanding, we collected GPS-tracked travel rate data from US Interagency Hotshot “Type 1” Crews during training in 2019. Firefighters were tracked while hiking, carrying standard loads (e.g., packs, tools, etc.) along trails with a precisely-measured terrain slope derived from airborne lidar. The effects of the slope on the instantaneous travel rate were assessed by three models generated using non-linear quantile regression, representing low (bottom third), moderate (middle third), and high (upper third) rates of travel, which were validated using k-fold cross-validation. The models peak at about a −3° (downhill) slope, similar to previous slope-dependent travel rate functions. The moderate firefighter travel rate model mostly predicts faster movement than previous slope-dependent travel rate functions, suggesting that firefighters generally move faster than non-firefighting personnel while hiking. Steepness was also found to have a smaller effect on firefighter travel rates than previously predicted. The travel rate functions produced by this study provide guidelines for firefighter escape route travel rates and allow for more accurate and flexible wildland firefighting safety planning.
Fire, Volume 3; doi:10.3390/fire3030051
Quaking aspen is found in western forests of the United States and is currently at risk of loss due to conifer competition at within-stand scales. Wildfires in these forests are impactful owing to conifer infilling during prolonged fire suppression post-Euro-American settlement. Here, restoration cuttings seek to impact wildfire behavior and aspen growing conditions. In this study, we explored how actual and hypothetical cuttings with a range of conifer removal intensity altered surface fuel and overstory structure at stand and fine scales. We then simulated wildfires, examining fire behavior and effects on post-fire forest structures around aspen trees. We found that conifer removal constrained by lower upper diameter limits (
Fire, Volume 3; doi:10.3390/fire3030050
With climate-driven increases in wildfires in the western U.S., it is imperative to understand how the risk to homes is also changing nationwide. Here, we quantify the number of homes threatened, suppression costs, and ignition sources for 1.6 million wildfires in the United States (U.S.; 1992–2015). Human-caused wildfires accounted for 97% of the residential homes threatened (within 1 km of a wildfire) and nearly a third of suppression costs. This study illustrates how the wildland-urban interface (WUI), which accounts for only a small portion of U.S. land area (~10%), acts as a major source of fires, almost exclusively human-started. Cumulatively (1992–2015), just over one million homes were within human-caused wildfire perimeters in the WUI, where communities are built within flammable vegetation. An additional 58.8 million homes were within one kilometer across the 24-year record. On an annual basis in the WUI (1999–2014), an average of 2.5 million homes (2.2–2.8 million, 95% confidence interval) were threatened by human-started wildfires (within the perimeter and up to 1-km away). The number of residential homes in the WUI grew by ~32 million from 1990–2015. The convergence of warmer, drier conditions and greater development into flammable landscapes is leaving many communities vulnerable to human-caused wildfires. Cumulatively, ~60 million homes were at high fire risk (1992–2015), meaning they were within historic wildfire perimeters or up to 1 km away. On average, 2.5 million homes were considered high fire risk each year. Our analysis explored the consequences and costs of wildfire ignitions along a gradient from urban to wildlands between 1992–2015. This study illustrates how the WUI, a small portion of U.S. land area that contains homes within flammable wildland vegetation, acts as a major source of wildfires, almost exclusively human-started. These areas are a high priority for policy and management efforts that aim to reduce human ignitions and promote resilience to future fires, particularly as the number of residential homes in the WUI grew by ~32 million across this record and are expected to continue to grow in coming years.
Fire, Volume 3; doi:10.3390/fire3030049
Frequent and severe droughts typically intensify wildfires provided that there is enough fuel in situ. The extent to which climate change may influence the fire regime and long time-scale hydrological processes may soften the effect of inter-annual climate change and, more specifically, whether soil-water retention capacity can alleviate the harsh conditions resulting from droughts and affect fire regimes, are still largely unexplored matters. The research presented in this paper is a development of a previous investigation and shows in what way, and to what extent, rainfall frequency, dry season length, and hydraulic response of different soil types drive forest fires toward different regimes while taking into consideration the typical seasonality of the Mediterranean climate. The soil-water holding capacity, which facilitates biomass growth in between fire events and hence favors fuel production, may worsen the fire regime as long dry summers become more frequent, such that the ecosystem’s resilience to climate shifts may eventually be undermined.