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

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. Moreover, different post-fire regenerative strategies may present different degrees of recovery, depending on the particular fire regime. Thus, differences in the flammability of species with distinct post-fire regenerative strategies can be the key to the establishment of a mutual link between fire regime and vegetation. We measured several parameters associated with the flammability and fuel loading of the dominant woody species in shrublands in the western Mediterranean Basin. We then analyzed the differences between these parameters in species with different post-fire regenerative strategies: seeders and non-seeders. Overall, seeder species show lower fuel load but are more prone to burning due to higher dead-tolive 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.