The relationship between terpenes and flammability of leaf litter

Many studies have assumed that plant terpenes favor fire due to their enormous flammability. However, only a few of them, all performed on green leaves, have demonstrated this. In the present work we investigated the question of whether litter terpene content can be used to estimate flammability and temperatures reached during fire. Epiradiator and burn table tests were used to compare flammability of leaf litter of P. pinaster, P. halepensis, P. pinea, C. albidus, C. ladanifer, C. laurifolius and the mixture of litter of P. pinaster with that of the other five species (e.g. P. pinaster + P. halepensis). Tests with burn table showed increasing spread rates and shorter combustion times under higher terpene contents. Flame height was triggered both with higher a terpene content and bed thickness, whereas the percentage of burned biomass was only significantly correlated to bed height. Epiradiator tests indicated that terpene concentration in leaf litter was positively correlated to flame height and negatively correlated to both flame residence time and ignition delay. Flammability was high for P. pinaster, P. halepensis, and hence for P. pinaster + P. halepensis, intermediate for C. albidus, P. pinea and P. pinaster combined with each of these species, and low for C. laurifolius, C. ladanifer and P. pinaster combined with them. Accordingly, their terpene content was high, intermediate and low. We concluded that plants might influence fire intensity, by having stored terpenes in their dead leaves, in addition to having developed traits to survive fire. Thus, a correct management of dead aboveground fuels rich in terpene concentrations, such as those of P. pinaster and P. halepensis, could prove helpful in reducing the hazard of fire.

[1]  E. Salinero.  Remote sensing of large wildfires in the European Mediterranean Basin , 1999 .

[2]  J. A. Rodríguez-Añón,et al.  Energetic study of residual forest biomass using calorimetry and thermal analysis , 2005 .

[3]  C. White.  Monoterpenes: Their effects on ecosystem nutrient cycling , 1994, Journal of Chemical Ecology.

[4]  F. Rego,et al.  A New Method to Estimate Fuel Surface Area-to-Volume Ratio Using Water Immersion. , 1998 .

[5]  A. P. Dimitrakopoulos,et al.  A statistical classification of Mediterranean species based on their flammability components , 2001 .

[6]  Pierpaolo Duce,et al.  Seasonal variations of live moisture content and ignitability in shrubs of the Mediterranean Basin , 2007 .

[7]  Alan J. Long,et al.  Flammability of native understory species in pine flatwood and hardwood hammock ecosystems and implications for the wildland–urban interface , 2004 .

[8]  Eric Rigolot,et al.  The fire ecology and management of maritime pine (Pinus pinaster Ait.) , 2007 .

[9]  M. Owens,et al.  Seasonal Patterns of Plant Flammability and Monoterpenoid Content in Juniperus ashei , 1998, Journal of Chemical Ecology.

[10]  H. Gali-Muhtasib,et al.  Seasonal changes in the composition of the essential oil extract of East Mediterranean sage (Salvia libanotica) and its toxicity in mice. , 2001, Toxicon.

[11]  D. Richardson,et al.  Effects of Invasive Alien Plants on Fire Regimes , 2004 .

[12]  J. Peñuelas,et al.  Implications of foliar terpene content and hydration on leaf flammability of Quercus ilex and Pinus halepensis. , 2008, Plant biology.

[13]  M. Estiarte,et al.  Influence of water and terpenes on flammability in some dominant Mediterranean species , 2008 .

[14]  Robert W. Mutch,et al.  Wildland Fires and Ecosystems--A Hypothesis , 1970 .

[15]  I. S. Regina.  Litter fall, decomposition and nutrient release in three semi‐arid forests of the Duero basin, Spain , 2001 .

[16]  Luis Gil,et al.  Canopy seed banks in Mediterranean pines of south‐eastern Spain: a comparison between Pinus halepensis Mill., P. pinaster Ait., P. nigra Arn. and P. pinea L. , 2001 .

[17]  N. Allsopp,et al.  Litterfall and Decomposition Processes in the Coastal Fynbos Vegetation, South-Western Cape, South Africa , 1986 .

[18]  K. R. Montgomery,et al.  Effect of Leaf Thickness on Ignitibility , 1971 .

[19]  J. Pausas,et al.  2 The role of fire in European Mediterranean Ecosystems , 1999 .

[20]  M. Westoby,et al.  Leaf litter flammability in some semi-arid Australian woodlands , 2006 .

[21]  A. Marpeau,et al.  Effects of wounding on the terpene content of twigs of maritime pine (Pinus pinaster Ait.) , 1989, Trees.

[22]  R. A. Bradstock,et al.  Fire regimes and biodiversity in semi-arid mallee ecosystems. , 2002 .

[23]  D. Schwilk.  Flammability Is a Niche Construction Trait: Canopy Architecture Affects Fire Intensity , 2003, The American Naturalist.

[24]  R. Adams,et al.  Identification of Essential Oil Components By Gas Chromatography/Mass Spectrometry , 2007 .

[25]  Paul-Antoine Santoni,et al.  The contribution of radiant heat transfer to laboratory-scale fire spread under the influences of wind and slope , 2001 .

[26]  Ran Nathan,et al.  Reproductive traits of Pinus halepensis in the light of fire – a critical review , 2004, Plant Ecology.

[27]  V. Isidorov,et al.  HS-SPME analysis of volatile organic compounds of coniferous needle litter , 2003 .

[28]  J. Peñuelas,et al.  Seasonal patterns of terpene content and emission from seven Mediterranean woody species in field conditions. , 2000, American journal of botany.

[29]  E. Ormeño,et al.  Plant coexistence alters terpene emission and content of Mediterranean species. , 2007, Phytochemistry.

[30]  M. Juhren,et al.  Cistus and its response to fire , 1954 .

[31]  L. Salvador,et al.  Regiones de procedencia Pinus pinaster Aiton , 1996 .

[32]  I. Cañellas,et al.  Litter fall in Mediterranean Pinus pinaster Ait. stands under different thinning regimes , 2005 .

[33]  D. Chagné,et al.  What can nuclear microsatellites tell us about maritime pine genetic resources conservation and provenance certification strategies , 2002 .

[34]  D. R. Hanson,et al.  Volatile organic emissions from the distillation and pyrolysis of vegetation , 2005 .

[35]  F. A. Rutigliano,et al.  Preliminary studies on litter flammability in Mediterranean region , 2006 .

[36]  A. Gill,et al.  Flammable Australia: The Fire Regimes and Biodiversity of a Continent , 2009 .

[37]  P. Proksch,et al.  Ecological significance of the chemistry of the leaf resin of elytropappus rhinocerotis , 1982 .