Fuel loading and flammability in the Mediterranean Basin woody species with different post-fire regenerative strategies

Abstract

The flammability and combustibility of plant communities are determined by species features related to growth-form, structure and physiology. In some ecosystems, such as the Mediterranean ones, these characteristics may contribute to the existence of fire-prone species. We measured several parameters associated with the flammability and fuel loading of dominant woody species with different post-fire regenerative strategies (seeders and non-seeders) in shrublands in the western Mediterranean Basin. Overall, seeder species show lower fuel load but are more prone to burning owing to a higher dead-to-live fuel ratio, live fine-fuel proportion and dead fine-fuel proportion. Moreover, they burst into flame at lower temperatures than non-seeders. In the Mediterranean Basin, most seeder species emerged mainly during the Quaternary, under a highly fluctuating Mediterranean climate and during recurrent fires. We propose that properties related to the combustibility and flammability of seeders may be the result of selective pressures associated with both fire and climate. These results suggest that ecosystems dominated by seeder species are more susceptible to fire risk than those dominated by non-seeder species in the Mediterranean Basin. Therefore, the proportion of these types of species resulting from previous fire or management history is likely to determine the characteristics of future fire events.

Have plants evolved to self-immolate?

“…Thinner leaves, which have a high surface area to volume ratio and high specific leaf area, and larger leaves, appear to be more ignitable (Gill and Moore, 1996; Saura-Mas et al, 2010; Murray et al, 2013). However, species with small leaves tend to have narrow, frequently branched twigs and dense wood, which burn more intensely (Westoby and Wright, 2003; Pickup et al, 2005), potentially counteracting the lower flammability of small individual leaves.…”

“…A feature of the discussion about the evolution of flammability is that flammability traits have been conflated with strategies that enable plants to recover following fire, such as resprouting from basal or aerial bud banks, and storing seeds in aerial or soil seed banks (Saura-Mas et al, 2010; Clarke et al, 2013). Such strategies manifestly increase the fitness of individual plants in fire prone landscapes.…”

Wildfire frequency varies with the size and shape of fuel types in southeastern France: Implications for environmental management

“…Actually, shrubby fuels are long acknowledged fireprone in many MTEs throughout the world (Moreira et al, 2001;Mouillot et al, 2002;Baeza et al, 2006;Syphard et al, 2007;Saura-Mas et al, 2010). Many shrubs common to MTEs (Quercus coccifera, Erica arborea, Cistus spp., Ulex) have been proved highly flammable due to a high amount of fine and dead fuel particles, low fuel moisture content during summer, and chemical compounds (Baeza et al, 2006;Saura-Mas et al, 2010). In addition, shrublands of Provence contain high proportion of flammable grasses such as Brachypodium retusum which favour ignition (Curt and Delcros, 2010;Curt et al, 2011).…”

Fire Hazard and Flammability of European Forest Types

“…Combustibility indicates how plants burn after they have been ignited. Sustainability indicates the capacity of a fuel to burn over time (fl ame duration) (Saura-Mas et al 2010 ) . Martin et al ( 1993 ) added one more component, consumability , defi ning it as "the degree to which a fuel is consumed by fi re".…”