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

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 (southeastern France). Results were the variability in flammability recorded during burning experiments performed on undisturbed litter samples were 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. The assessment of litter flammability of the seven species enabled them to be ranked in four clusters from poorly flammable (Pittosporum tobira) to highly flammable (Photinia fraseri and Prunus laurocerasus). These latter species should not be used in hedges planted in wildland–urban interfaces in south-eastern France. The flammability of the undisturbed litter of seven species, among those most frequently planted in hedges in Provence (south-eastern France), was assessed in laboratory conditions. The flammability variables were partly explained by the proportions of the different litter components of each species. These species were ranked in four distinct clusters from the most flammable to the least flammable. Additional keywords: flammability variables, hedge, litter composition, undisturbed litter Introduction In France, the south-east is the area the most affected by wildfires (55% of the total number of fires in France for the period 2006–08 according to the French forest fire database Prométhée), mostly in the wildland–urban interface (WUI). These WUI fires are a serious threat to communities in many Author produced version of the article published in International Journal of Wildland Fire, 2012, 22(3) 333-342 Original publication available at www.publish.csiro.au/nid/114.htm doi:10.171/WF12006 ha l-0 08 60 79 2, v er si on 1 11 S ep 2 01 3 Author manuscript, published in "International Journal of Wildland Fire 22, 3 (2012) p. 333 p. 342" DOI : 10.1071/WF12006