Assessing the flammability of surface fuels beneath ornamental vegetation in wildland–urban interfaces in Provence (south-eastern France)

Abstract

The objectives of this paper are to assess in laboratory conditions the flammability of undisturbed litter sampled beneath plants of seven species that are among those most frequently planted in hedges in Provence (south-eastern France). The variability in litter flammability recorded during burning experiments was partly explained by the proportions of the different litter components of each species. Phyllostachys sp. and Nerium oleander litters were the quickest to ignite whereas Prunus laurocerasus litter had the lowest bulk density and long time-to-ignition, but high flame-propagation. Photinia fraseri litter ignited frequently and had a high flame spread whereas Pittosporum tobira litter ignited the least frequently and for the shortest duration. Cupressus sempervirens litter had the highest bulk density and the longest flaming duration but the lowest flame propagation. Pyracantha coccinea litter was the slowest to ignite and flame propagation was low but lasted a long time. Co-inertia analysis identified species with the same flammability characteristics according to the composition of their litter. Hierarchical cluster analysis ranked the seven species in four distinct clusters from the most flammable (Photinia fraseri and Prunus laurocerasus) to the least flammable (Pittosporum tobira), the other species displaying two groups of intermediate flammability. These latter species should not be used in hedges planted in wildland–urban interfaces in south-eastern France.