The influence of leaf water content and isoprenoids on flammability of some Mediterranean woody species
Manuela De Lillis A C , Pietro Massimiliano Bianco A and Francesco Loreto BA Dipartimento di Scienze e Tecnologie per l’Ambiente ed il Territorio (DSTAT), Università del Molise, I-86170 Isernia, Italy.
B Consiglio Nazionale delle Ricerche (CNR) – Istituto di Biologia Agroambientale e Forestale (IBAF), I-00015 Monterotondo Scalo, Roma, Italy.
C Corresponding author. Email:delillis@unimol.it
International Journal of Wildland Fire 18(2) 203-212 https://doi.org/10.1071/WF07075
Submitted: 30 May 2007 Accepted: 11 June 2008 Published: 2 April 2009
Abstract
The impact of water content and isoprenoids on leaf flammability was studied. Field and laboratory experiments were carried out on monoterpene-emitting evergreen broad-leaved species (Quercus ilex, Quercus suber); a needle-leaved species (Pinus halepensis) that emits and stores monoterpenes; an evergreen species (Myrtus communis) that emits isoprene but stores monoterpenes; and a deciduous species (Quercus pubescens) that emits isoprene. Photosynthesis, leaf water content (LWC) and isoprenoid emission were measured. Isoprenoid content was calculated. Temperatures of visible smoke, incandescence and flame appearance were recorded. The LWC significantly correlated with both photosynthesis and isoprenoid emissions. Linear correlation and factorial analysis revealed a positive correlation between temperature of flame appearance and LWC and a negative relationship between temperature of flame appearance and isoprenoid emission. Multiple regression analysis indicated that the temperature of flame appearance was reduced in broadleaved monoterpene-emitting species. In monoterpene emitters, the temperature of flame appearance depended for ~65% on LWC, whereas monoterpene emissions explained ~35% of the dependency. P. halepensis and M. communis, storing high levels of isoprenoids, ignited at high humidity. The results may be explained if isoprenoids indeed facilitate leaf ignition but, being dissolved in water, isoprenoids are also an indicator of a high water content that decreases flammability.
Additional keywords: fire, flammability phases, monoterpenes, photosynthesis, temperature of flame appearance.
Acknowledgements
The work was supported by the Marie Curie Research and Training Network ‘Ecological and Physiological Functions of Biogenic Isoprenoids and their Impact on the Environment’ (ISONET, MRTNCT–2003–504720). Giorgio Arturo Alessio is acknowledged for helping with field measurements. Silvano Fares is also acknowledged for helping with the preparation of the manuscript.
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