Leaf litter flammability in some semi‐arid Australian woodlands

Abstract

Summary 1.Wildfires strongly influence the biotic composition and carbon cycle of many ecosystems. Plant species provide the fuel for wildfires, but vary widely in their flammability. This study aimed to determine what plant characteristics control leaf litter flammability and to clarify how they are related to other functional traits. 2. Litter flammability varied across 14 tree species occurring in a mosaic of five floristic associations. 3. Differences in heat-release rate between species were driven by leaf size, from smallleaved conifers, casuarinas and acacias to large-leaved eucalypts and Brachychiton . 4. Large leaves created an open litter-bed structure that burned more rapidly because it was better ventilated. The results on heat-release rate were partitioned according to fundamental principles for the transport of oxygen through a packed fuel bed, showing that heat-release rate scaled linearly with estimated gas-flow rates, as expected in ventilation-controlled fires. 5. Species that were able to resprout after fire had litter that burned more intensely and was more likely to sustain a spreading fire than litter from obligate seeders, and were correspondingly larger-leaved. 6. Many fire-prone wooded ecosystems in the region consist of large-leaved resprouting tree species co-occurring with small-leaved obligate seeders.

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

“…Scarff and Westoby (2006) reported that large leaves created an open litter bed structure which burned more rapidly because it was better ventilated. Leaf size was shown to be the most important trait influencing both the intensity and sustainability of litter fires, more than chemical factors known to influence flammability, such as oils and lignin content (Vines 1981;Parker and LeVan 1989).…”

“…The litters of each species presented their own flammability mainly depending on their composition and bulk density because this variable, which determines fuel compaction in space, controls the rate of oxygen that can flow through the fuels as well as the heat transfer between fuel particles (Scarff and Westoby 2006). The moisture content of the oven-dried litter samples was assumed to not affect the flammability as it was very low.…”

“…Flammability also depends on the characteristics of the whole litter, in particular litter depth and bulk density (Pyne et al 1996), and ventilation of the litter bed plays an important role in the burning process (Scarff and Westoby 2006). Regarding ornamental vegetation, Long et al (2006a) provided flammability data for horticultural beds by evaluating the effect of the type of mulch, planting composition and drought conditions on fire spread and heat release in both field and controlledenvironment conditions.…”

“…The importance of non-woody surface-fuel in wildfire has been addressed in numerous studies in terms of the effects of its arrangement (Bradstock and Cohn 2002) and morphology (Scarff and Westoby 2006), for instance. The flammability of the leaves or needles of the main Mediterranean species regarded as fuel or firebrand involved in spot fires has already been assessed in several studies (Valette 1990;Dimitrakopoulos and Papaioannou 2001;Ganteaume et al 2009Ganteaume et al , 2011aGanteaume et al , 2011b but the flammability of litters sampled under vegetation planted in hedges remains to be assessed.…”

“…Methods to assess and compare the flammability of litter and wildland fuels vary (Petriccione et al 2006;Pellizzaro et al 2007;Ormeño et al 2009;Scarff and Westoby 2006); some use different burning devices such as fire benches (for dead fuels) and different types of ignition sources, usually calibrated samples of dead leaves of a given species (disturbed litter samples). The flammability of non-reconstructed litter samples, which are hypothesised to represent field conditions (as opposed to reconstructed litters that are typically studied (Jappiot et al 2007)), has been studied in south-eastern Author produced version of the article published in International Journal of Wildland Fire, 2012, 22(3) [333][334][335][336][337][338][339][340][341][342] Original publication available at www.publish.csiro.au/nid/114.htm doi:10.171/WF12006…”