Extreme Fire Severity Patterns in Topographic, Convective and Wind-Driven Historical Wildfires of Mediterranean Pine Forests

Abstract

Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR) from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1) determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together) and (2) ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires). The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires) showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn as extreme severity wildfires.

Development of a New Daily-Scale Forest Fire Danger Forecasting System Using Remote Sensing Data

“…These findings were found acceptable as the fire occurrences would not only depend on the PW but also other factors, e.g., temperature, precipitation, wind regimes, topography, fuel types, source of ignitions, etc. [8,26,[61][62][63]. In addition, we observed that other input variables of the FFDFS (i.e., TS, NMDI, and NDVI) demonstrated similar results (i.e., 50.60%, 65.50%, and 61.95% of the fire spots fell under the "high danger" category for TS, NMDI, and NDVI respectively during 2009-2011).…”

Examining Spatial Variation in the Effects of Japanese Red Pine (Pinus densiflora) on Burn Severity Using Geographically Weighted Regression

“…However, the cause of this non-stationary effect of red pine trees on burn severity is unclear. In the literature, numerous variables are involved in determining the burn severity at certain locations during fire events, such as meteorological conditions [21,22], pre-fire forest structure [19,28,31], fuel type and characteristics [25,26] and topography [21,22]. On a broader level, the presence of non-stationary effects of red pine trees on burn severity is due to the dynamics and complexity of the interactions of these relevant variables.…”

“…According to the literature, the degree of burn severity is largely determined by various environmental factors, including meteorological conditions [20][21][22], pre-fire forest vegetation type [19,23,24], fuel moisture [25,26], tree stand density [27,28], composition and configuration of pre-fire forest [19,[29][30][31][32][33], tree characteristics [34], and topography [19][20][21][22][23][24]28,30,33], as well as the interactions among relevant variables [22,24]. Considering that meteorological conditions and topological characteristics are not manageable factors, controlling susceptible fuels might be the only practical tool for lowering burn severity.…”

Wildland fire typologies and extreme temperatures in NE Spain

“…Moreover, fire agencies invested heavily in suppression resources and improved remarkably their training and fire behavior knowledge. MWFs were classified into three different fire spread patterns: topography-driven fires, wind-driven fires and convective fires (Lecina-Diaz et al 2014, Duane et al 2015. Lázaro et al (2014) and Lázaro-Palacios et al (2016) made a characterization of fire typologies in this region based on synoptic weather condition analysis across the study area.…”

“…Depending on the spread scheme, fires have been usually classified into three different fire spread patterns according to the dominant spread factor: topography (topography-driven fires), wind (wind-driven fires) or fuel accumulation that could be related to convective fires (Lecina-Diaz et al 2014, Duane et al 2015. Topography-driven fires are characterized by local convective winds caused by differential solar heating of the land surface.…”