Factors influencing the pattern of fire severities in a large wildfire under extreme meteorological conditions in the Mediterranean basin

Abstract

In Mediterranean ecosystems, large fires frequently burn under extreme meteorological conditions, but they are usually characterized by a spatial heterogeneity of burn severities. The way in which such mixed-severity fires are a result of fuels, topography and weather remains poorly understood. We computed fire severity of a large wildfire that occurred in Catalonia, Spain, as the difference between the post- and pre-fire Normalized Difference Vegetation Index (NDVI) values obtained through Landsat images. Fuel and topographic variables were derived from remote sensing, and fire behavior variables were obtained from an exhaustive reconstruction of the fire. Results showed that fire severity had a negative relationship with percentage of canopy cover, i.e. green surviving plots were mainly those with more forested conditions. Of the topographic variables, only aspect had a significant effect on fire severity, with higher values in southern than in northern slopes. Fire severity was higher in head than in flank and back fires. The interaction of these two variables was significant, with differences between southern and northern aspects being small for head fires, but increasing in flank and back fires. The role of these variables in determining the pattern of fire severities is of primary importance for interpreting the current landscapes and for establishing effective fire prevention and extinction policies.

Landscape – wildfire interactions in southern Europe: Implications for landscape management

“…1978/79 and 1994in Spain, 1998, 2000in Greece, 2005in Portugal, 2003 helped to highlight the importance of LF in the Euro-Mediterranean (e.g. Oliveras et al, 2009;Piñol et al, 1998;Pausas, 2004;Xanthopoulos, 2007a). LFs represent a small fraction of the total number of fires, but are responsible for a large percentage of the total land area burned in the Mediterranean basin (e. g. Bermudez et al, 2009;DiazDelgado et al, 2004).…”

Microclimate and Modeled Fire Behavior Differ Between Adjacent Forest Types in Northern Portugal

“…Fuel and vegetation types influence fire behavior and severity, but the role of differences in micrometeorology between forest types is difficult to ascertain empirically, partly because of confounded effects between topography, fire spread patterns, and stand structure [16,22,35]. Fire modeling with typical fuel and weather inputs [36,37] potentially accomplishes a better understanding of the relative importance of the factors driving fire behavior.…”

“…Empirical studies generally indicate mitigation of fire behavior or fire severity in more mature stands [16,17] and in deciduous broadleaved forest [18][19][20][21][22] and short-needled conifers [22] in comparison with pine forests. Modification of fire behavior characteristics is expected to disturb or disrupt landscape fire growth, directly, by delaying or impeding fire spread and, indirectly, by allowing successful fire suppression operations, hence, translating into less area burned and differential burning rates among vegetation types.…”

Modeling Relationships among 217 Fires Using Remote Sensing of Burn Severity in Southern Pine Forests

“…Previous studies in other regions have used dNBRs to calibrate severity levels to specific forest types [10,15,16,19], compare severity levels between fire events [12,19], interpret the effects of fuel management techniques on severity levels [20], and to monitor changes in vegetation over time [17,21] and across topography [11,22]. The multi agency project, Monitoring Trends in Burn Severity (MTBS) is currently using dNBRs to map burn severity and the perimeters of wildfires greater than 405 ha in the western US and 202 ha in the eastern US [23].…”