Does the temporal variation of leaf terpene and moisture content trigger leaf flammability over time?

Anne Ganteaume; Bastien Romero; Elena Ormeño; Caroline Lecareux; Catherine Fernandez

doi:10.1071/WF24190

RESEARCH ARTICLE (Open Access)

Previous Contents Vol 34(9)

Does the temporal variation of leaf terpene and moisture content trigger leaf flammability over time?

Anne Ganteaume ^A ^* , Bastien Romero ^A , Elena Ormeño ^B , Caroline Lecareux ^B and Catherine Fernandez ^B

+ Author Affiliations

- Author Affiliations

^A Aix-Marseille Université, INRAE, UMR RECOVER, Aix-en Provence, France.

^B Aix-Marseille Université, CNRS- IRD- Avignon, UMR IMBE, Marseille, France.

^* Correspondence to: anne.ganteaume@inrae.fr

International Journal of Wildland Fire 34, WF24190 https://doi.org/10.1071/WF24190

Submitted: 5 November 2024 Accepted: 8 August 2025 Published: 27 August 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of IAWF. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Background – aims

It is widely assumed that plant flammability in the Mediterranean region peaks during the summer fire season. We currently lack data that could evaluate these assumptions and have not assessed the mechanisms, e.g. fuel moisture content (FMC) or terpenes, that might drive these patterns.

Methods

To determine the mechanistic drivers of species flammability, we used leaf burning experiments coupled with foliar chemical analyses focusing on Aleppo pine (Pinus halepensis) and three introduced cypresses commonly found at the wildland–urban interface (WUI) in southeastern France.

Key results

Terpenes, FMC and flammability varied over time and across the species studied, with contrasting patterns for each. Rare correlations between FMC and flammability occurred, in only one season and differing among species, while correlations between flammability and terpene compounds were diverse. The best flammability drivers were terpenes (mainly diterpenes), often changing among and within seasons, and their effect on flammability also differed. Overall, FMC was not a significant explanatory parameter of leaf flammability.

Conclusions – implications

Highlighting the temporal variation between flammability and its drivers revealed that species flammability could also be enhanced by terpenes outside the fire season; this should be accounted for in fire prevention, especially at the WUI.

Keywords: flammability drivers, fuel moisture content, leaf flammability, leaf terpene content, Mediterranean region, Pinus halepensis, terpene temporal variation, wildland–urban interface vegetation.

References

Adams R (2007) ‘Identification of Essential Oils by Gas Chromatography/Mass Spectrometry.’ (Carol Stream: Allured Publishing Corporation: Carol Stream, IL, USA)

Adams RP (1970) Seasonal variation of terpenoid constituents in natural populations of Juniperus pinchotii Sudw. Phytochemistry 9, 397-402.
| Crossref | Google Scholar |

Adams RP, Bartel JA, Price RA (2009) A new genus, Hesperocyparis, for the cypresses of the western hemisphere. Phytologia 91(1), 160-185.
| Google Scholar |

Agee JK, Wright CS, Williamson N, Huff MH (2002) Foliar moisture content of Pacific Northwest vegetation and its relation to wildland fire behavior. Forest Ecology and Management 167, 57-66.
| Crossref | Google Scholar |

Alessio G, De Lillis M, Brugnoli E, Lauteri M (2004) Water sources and water-use efficiency in Mediterranean coastal dune vegetation. Plant Biology 6, 350-357.
| Crossref | Google Scholar | PubMed |

Alessio G, Peñuelas J, De Lillis M, Llusià J (2008a) Implications of foliar terpene content and hydration on leaf flammability of Quercus ilex and Pinus halepensis. Plant Biology 10, 123-128.
| Crossref | Google Scholar |

Alessio G, Peñuelas J, Llusià J, Ogaya R, Estiarte M, De Lillis M (2008b) Influence of water and terpenes on flammability in some dominant Mediterranean species. International Journal of Wildland Fire 17, 274-286.
| Crossref | Google Scholar |

Anderson HE (1970) Forest fuel ignitibility. Fire Technology 6, 312-319.
| Crossref | Google Scholar |

Bernard-Degan C (1988) Seasonal variations in energy sources and biosynthesis of terpenoids in maritime pine. In ‘Mechanisms of Woody Plant Defenses Against Insects’. (Eds WJ Mattson, J Levieux, C Bernard-Degan) pp. 93–116. (Springer: New York, NY, USA)

Bertin N, Staudt M (1996) Effect of water stress on monoterpene emissions from young potted holm oak (Quercus ilex L.) trees. Oecologia 107, 456-462.
| Crossref | Google Scholar | PubMed |

Blanch J-S, Peñuelas J, Sardans J, Llusià J (2009) Drought, warming and soil fertilization effects on leaf volatile terpene concentrations in Pinus halepensis and Quercus ilex. Acta Physiologiae Plantarum 31, 207-218.
| Crossref | Google Scholar |

Bloomfield KJ, Cernusak L, Eamus D, Ellsworth DS, Prentice IC, Wright IJ, Boer MM, Bradford M, Cale P, Cleverly JR, Egerton J, Evans B, Hayes L, Hutchinson M, Liddell MJ, Macfarlane C, Meyer WS, Prober SM, Togashi FH, Wardlaw T, Zhu L, Atkin O (2018) A continental-scale assessment of variability in leaf traits: within species, across sites and between seasons. Functional Ecology 32, 1492-1506.
| Crossref | Google Scholar |

Boving I, Celebrezze J, Salladay R, Ramirez A, Anderegg LDL, Moritz M (2023) Live fuel moisture and water potential exhibit differing relationships with leaf‐level flammability thresholds. Functional Ecology 37, 2770-2785.
| Crossref | Google Scholar |

Brofas G, Karetsos G, Dimopoulos P, Tsagari C (2006) The natural environment of Cupressus sempervirens in Greece as a basis for its use in the Mediterranean region. Land Degradation and Development 17, 645-659.
| Crossref | Google Scholar |

Cappelli M, Bonani S, Conci I (1983) Sul grado d’infiammabilità di alcune specie della macchia Mediterranea. Collana Verde 62, 1-52 [In Italian].
| Google Scholar |

Cawson JG, Burton JE, Pickering BJ, Demetriou V, Filkov AI (2023) Quantifying the flammability of living plants at the branch scale: which metrics to use? International Journal of Wildland Fire 32(10), 1404-1421.
| Crossref | Google Scholar |

Centritto M, Brilli F, Fodale R, Loreto F (2011) Different sensitivity of isoprene emission, respiration and photosynthesis to high growth temperature coupled with drought stress in black poplar (Populus nigra) saplings. Tree Physiology 31, 275-286.
| Crossref | Google Scholar | PubMed |

Chetehouna K, Barboni T, Zarguili E, Simeoni A, Fernandez-Pello A-C (2009) Investigation on the emission of volatile organic compounds from heated vegetation and their potential to cause an accelerating forest fire. Combustion Science and Technology 181(10), 1273-1288.
| Crossref | Google Scholar |

Chuvieco E, Deshayes M, Stach N, Cocero D, Riaño D (1999) Short-term fire risk: foliage moisture content estimation from satellite data. In ‘Remote Sensing of Large Wildfires in the European Mediterranean Basin’. (Ed. E Chuvieco) pp. 17–38. (Springer-Verlag: New York, NY, USA)

Clarke PJ, Prior LD, French BJ, Vincent B, Knox KJE, Bowman DMJS (2014) Using a rainforest-flame forest mosaic to test the hypothesis that leaf and litter fuel flammability is under natural selection. Oecologia 176, 1123-1133.
| Crossref | Google Scholar | PubMed |

Cornelissen JHC, Lavorel S, Garnier E, Diaz S, Buchmann N, Gurvich DE, Reich PB, Ter Steege H, Morgan HD, Van der Heijden MGA, Pausas JG, Poorter H (2003) ) Handbook of protocols for standardized and easy measurement of plant functional traits worldwide. Australian Journal of Botany 51, 335-380.
| Crossref | Google Scholar |

Cornwell WK, Elvira A, van Kempen L, Van Logtestijn RSP, Aptroot A, Cornelissen JHC (2015) Flammability across the gymnosperm phylogeny: the importance of litter particle size. New Phytologist 206, 672-681.
| Crossref | Google Scholar | PubMed |

Correia OA, Oliveira G, Martins-Loucão MA, Catarino FM (1992) Effects of bark stripping on the water relations of Quercus suber L. Scientia Gerundensis 18, 195-204.
| Google Scholar |

Courty L, Chetehouna K, Halter F, Foucher F, Garo J-P, Mounaïm-Rousselle C (2012) Flame speeds of α-pinene/air and limonene/air mixtures involved in accelerating forest fires. Combustion Science and Technology 184(10–11), 1397-1411.
| Crossref | Google Scholar |

De Lillis M, Bianco PM, Loreto F (2009) The influence of leaf water content and terpenoids on flammability of some Mediterranean woody species. International Journal of Wildland Fire 18, 203-212.
| Crossref | Google Scholar |

Della Rocca G, Madrigal J, Marchi E, Michelozzi M, Moya B, Danti R (2017) Relevance of terpenoids on flammability of Mediterranean species: an experimental approach at a low radiant heat flux. iForest 10, 766-775.
| Crossref | Google Scholar |

de Magalhães RMQ, Schwilk DW (2012) Leaf traits and litter flammability: evidence for non-additive mixture effects in a temperate forest. Journal of Ecology 100, 1153-1163.
| Crossref | Google Scholar |

Di Castri F (1973) Climatographical comparisons between Chile and the western coast of North America. In ‘Mediterranean-type Ecosystems’. (Eds F Di Castri, HA Mooney) pp. 21–36. (Springer Verlag: Berlin, Germany)

Engber EA, Varner JM (2012) Patterns of flammability of the California oaks: the role of leaf traits. Canadian Journal of Forest Research 42, 1965-1975.
| Crossref | Google Scholar |

Fajardo A, Siefert A (2016) Phenological variation of leaf functional traits within species. Oecologia 180, 951-959.
| Crossref | Google Scholar | PubMed |

Gambiel HA, Cates RG (1995) Terpene changes due to maturation and canopy level in Douglas fir (Pseudotsuga menziesii) flush needle oil. Biochemical Systematics and Ecology 5, 469-476.
| Crossref | Google Scholar |

Ganteaume A (2018) Does plant flammability differ between leaf and litter bed scale? Role of fuel characteristics and consequences for flammability assessment. International Journal of Wildland Fire 27, 342-352.
| Crossref | Google Scholar |

Ganteaume A, Jappiot M, Lampin C (2013) Assessing the flammability of surface fuels beneath ornamental vegetation in wildland–urban interfaces in Provence (south-eastern France). International Journal of Wildland Fire 22, 333-342.
| Crossref | Google Scholar |

Ganteaume A, Romero B, Fernandez C, Ormeño E, Lecareux C (2021) Volatile and semi-volatile terpenes impact leaf flammability: differences according to the level of terpene identification. Chemoecology 31, 259-275.
| Crossref | Google Scholar |

Gilmore AR (1977) Effects of soil moisture stress on monoterpenes in loblolly pine. Journal of Chemical Ecology 3, 667-676.
| Crossref | Google Scholar |

Grootemaat S, Wright I, Van Bodegom P, Cornwell W (2015) Burn or rot: leaf traits explain why flammability and decomposability are decoupled across species. Functional Ecology 29, 1486-1497.
| Crossref | Google Scholar |

Guerrero F, Carmona C, Hernández C, Toledo M, Arriagada A, Espinoza L, Bergmann J, Taborga L, Yañez K, Carrasco Y, Muñoz AA (2022) Drivers of flammability of Eucalyptus globulus Labill leaves: terpenes, essential oils, and moisture content. Forests 13, 908.
| Crossref | Google Scholar |

Guerrero F, Espinoza L, Carmona C, Blackhall M, Quintero C, Ocampo-Zuleta K, Paula S, Madrigal J, Guijarro M, Carrasco Y, Bustamante-Sánchez MA, Miranda A, Yáñez K, Bergmann J, Taborga L, Toledo M (2024) Unravelling the chemistry of plant flammability: exploring the role of volatile secondary metabolites beyond terpenes. Forest Ecology and Management 572, 122269.
| Crossref | Google Scholar |

Hernando-Lara C (2000) Combustibles forestales: inflamabilidad. In ‘La defensa Contra Incendios Forestales, Fundamentos y Experiencias’. (Ed. R Vélez Muñoz) pp. 3–6. (McGraw-Hill: New York, NY, USA)

Kainulainen P, Oksanen J, Palomäki V, Holopainen J, Holopainen T (1992) Effect of drought and waterlogging stress on needle monoterpenes of Picea abies. Canadian Journal of Botany 70, 1613-1616.
| Crossref | Google Scholar |

Keeley JE, Bond WJ, Bradstock RA, Pausas JG, Rundel PW (2012) ‘Fire in Mediterranean Ecosystems: Ecology, Evolution and Management.’ (Cambridge University Press: Cambridge)

Kummerow J (1981) Carbon allocation to root systems in Mediterranean evergreen sclerophylls. In ‘Components of productivity of Mediterranean-climate regions, basic and applied aspects’. (Eds NS Margaris, HA Mooney). pp. 115–120. (Dr W. Junk Publishers, The Hague: Boston, London)

Langenheim JH (1994) Higher plant terpenoids: a phytocentric overview of their ecological roles. Journal of Chemical Ecology 20, 1223-1280.
| Crossref | Google Scholar | PubMed |

Llusià J, Peñuelas J (1998) Changes in terpene content and emission in potted Mediterranean woody plants under severe drought. Canadian Journal of Botany 76, 1366-1373.
| Crossref | Google Scholar |

Llusià J, Peñuelas J (2000) Seasonal patterns of terpene content and emission from seven Mediterranean woody species in field conditions. American Journal of Botany 87, 133-140.
| Google Scholar | PubMed |

Llusià J, Peñuelas J, Alessio GA, Estiarte M (2006) Seasonal contrasting changes of foliar concentrations of terpenes and other volatile organic compound in tour dominant species of a Mediterranean shrubland submitted to a field experimental drought and warming. Physiologioa Plantarrum 127, 632-649.
| Crossref | Google Scholar |

Loreto F, Ciccioli P, Cecinato A, Brancaleoni E, Frattoni M, Tricoli D (1996) Influence of environmental factors and air composition on the emission of α-pinene from Quercus ilex leaves. Plant Physiology 110, 267-275.
| Crossref | Google Scholar | PubMed |

Madrigal J, Hernando C, Guijarro M (2013) A new bench-scale methodology for evaluating flammability of live forest fuels. Journal of Fire Science 31(2), 131-142.
| Crossref | Google Scholar |

Marchese JA, Ferreira JFS, Rehder VLG, Rodrigues O (2010) Water deficit effect on the accumulation of biomass and artemisinin in annual wormwood (Artemisia annua L., Asteraceae). Brazilian Journal of Plant Physiology 22, 1-9.
| Crossref | Google Scholar |

Marino E, Guijarro M, Hernando C, Madrigal J, Díez C (2011) Fire hazard after prescribed burning in a gorse shrubland: implications for fuel management. Journal of Environmental Management 92, 1003-1011.
| Crossref | Google Scholar | PubMed |

Martin RE, Gordon DA, Gutierrez M, Lee DS, Molina DM, Schroeder RA, Sapsis DB, Stephens SL, Chambers M (1993) Assessing the flammability of domestic and wildland vegetation. In ‘Proceedings of the Proceedings of the 12th conference on fire and forest meteorology’. pp. 26–28. (Society of American Foresters Publication 94-02: Bethesda, MD, USA)

Massari G, Leopaldi A (1998) Leaf flammability in Mediterranean species. Plant Biosystems 132(1), 29-38.
| Crossref | Google Scholar |

McKenzie D, Gedalof ZE, Peterson DL, Mote P (2004) Climatic change, wildfire, and conservation. Conservation Biology 18(4), 890-902.
| Crossref | Google Scholar |

Murray BR, Hardstaff LK, Phillips ML (2013) Differences in leaf flammability, leaf traits and flammability-trait relationships between native and exotic plant species of dry sclerophyll forest. PLoS One 8, e79205.
| Crossref | Google Scholar | PubMed |

Muzica RM, Pregitzer KS, Hanover JW (1989) Changes in terpene production following nitrogen fertilization of grand fir [Abies grandis (Dougl.) Lindl.] seedlings. Oecologia 8, 485-489.
| Crossref | Google Scholar |

NIST (2011) ‘X Ray photoelectron spectroscopy database, Version 3.5.’ (National Institute of Technology: Gaithersburg, MD, USA)

Ormeño E, Baldy V, Ballini C, Fernandez C (2008) Production and diversity of volatile terpenes from plants on calcareous and siliceous soils: effect of soil nutrients. Journal of Chemical Ecology 34, 1219-1229.
| Crossref | Google Scholar | PubMed |

Ormeño E, Cespedes B, Sanchez IA, Velasco-García A, Moreno JM, Fernandez C, Baldy V (2009) The relationship between terpenes and flammability of leaf litter. Forest Ecology and Management 257, 471-482.
| Crossref | Google Scholar |

Ormeño E, Ruffault J, Gutigny C, Madrigal J, Guijarro M, Hernando C, Ballini C (2020) Increasing cuticular wax concentrations in a drier climate promote litter flammability. Forest Ecology and Management 473, 118242.
| Crossref | Google Scholar |

Owens MK, Lin C-D, Taylor CA, Whisenant SG (1998) Seasonal patterns of plant flammability and monoterpenoid content in Juniperus ashei. Journal of Chemical Ecology 24, 2115-2129.
| Crossref | Google Scholar |

Page WG, Jenkins MJ, Runyon JB (2012) Mountain pine beetle attack alters the chemistry and flammability of lodgepole pine foliage. Canadian Journal of Forest Research 42, 1631-1647.
| Crossref | Google Scholar |

Pausas JG, Moreira B (2012) Flammability as a biological concept. New Phytologist 194, 610-613.
| Crossref | Google Scholar | PubMed |

Pausas JG, Alessio GA, Moreira B, Segarra-Moragues JG (2016) Secondary compounds enhance flammability in a Mediterranean plant. Oecologia 180, 103-110.
| Crossref | Google Scholar | PubMed |

Pellizzaro G, Duce P, Ventura A, Zara P (2007) Seasonal variations of live moisture content and ignitability in shrubs of the Mediterranean Basin. International Journal of Wildland Fire 16, 633-641.
| Crossref | Google Scholar |

Pellizzaro G, Ventura A, Arca B, Arca A, Duce P (2009) Weather seasonality and temporal pattern of live and dead fuel moisture content in Mediterranean shrubland. In ‘European Geosciences Union General Assembly 2009’, 19-24 April 2009, Vienna, Austria. p. 12100. Available at http://meetings.copernicus.org/egu2009

Peñuelas J, Llusià J (1997) Effects of carbon dioxide, water supply, and seasonality on terpene content and emission by Rosmarinus officinalis. Journal of Chemical Ecology 23, 979-993.
| Crossref | Google Scholar |

Peñuelas J, Llusià J (2001) The complexity of factors driving volatile organic compound emissions by plants. Biologia Plantarum 44, 481-487.
| Crossref | Google Scholar |

Popović Z, Bojović S, Marković M, Cerdà A (2021) Tree species flammability based on plant traits: a synthesis. Science of The Total Environment 800, 149625.
| Crossref | Google Scholar | PubMed |

Rice CL, Martin RE (1985) Live fuel moistures of California North coast scrub species. In ‘Eighth Conference on Fire and Forest Meteorology’. pp. 263–269. (Society of American Foresters: Detroit, MI; Bethesda, MD, USA)

Rodriguez Añon JA, Fraga López F, Proupín Castiñeiras J, Palacios Ledo J, Núñez Regueira L (1995) Calorific values and flammability for forest wastes during the seasons of the year. Bioresource Technology 52, 269-274.
| Crossref | Google Scholar |

Romero B, Fernandez C, Lecareux C, Ormeño E, Ganteaume A (2019) How terpene content affects fuel flammability of wildland–urban interface vegetation. International Journal of Wildland Fire 28, 614-627.
| Crossref | Google Scholar |

Romero B, Scotti I, Fady B, Ganteaume A (2023) Fire frequency, as well as stress-response and developmental genes control serotiny level variation in a widespread pioneer Mediterranean conifer. Ecology and Evolution 13(3), e9919.
| Crossref | Google Scholar | PubMed |

Rothermel RC (1972) A mathematical model for predicting fire spread in wildland fuels. Res. Pap. INT-115. 40 p. (USDA Forest Service, Intermountain Forest and Range Experiment Station: Ogden, UT)

Sampedro L, Moreira X, Zas R (2011) Costs of constitutive and herbivore-induced chemical defences in pine trees emerge only under low nutrient availability. Journal of Ecology 99, 818-827.
| Crossref | Google Scholar |

Santoni PA, Bartoli P, Simeoni A, Torero J (2014) Bulk and particle properties of pine needle fuel beds – influence on combustion. International Journal of Wildland Fire 23, 1076-1086.
| Crossref | Google Scholar |

Scarff FR, Westoby M (2006) Leaf litter flammability in some semi-arid Australian woodlands. Functional Ecology 20, 745-752.
| Crossref | Google Scholar |

Schwilk DW, Caprio AC (2011) Scaling from leaf traits to fire behaviour: community composition predicts fire severity in a temperate forest. Journal of Ecology 99, 970-980.
| Crossref | Google Scholar |

Tingey DT, Manning M, Grothaus LC, Burns WF (1980) Influence of light and temperature on monoterpene emission rates from slash pine. Plant Physiology 65, 797-801.
| Crossref | Google Scholar | PubMed |

Valette JC (1990) Inflammabilités des espèces forestières méditerranéennes. Revue Forestière Française 42, 76-92.
| Crossref | Google Scholar |

Van Wagner CE (1967) ‘Seasonal variation in moisture content of eastern Canadian tree foliage and the possible effect on crown fires.’ p. 1204. (Canadian Department of Foreign Affairs, Department of Public Works)

Varner JM, Kane JM, Kreye JK, Engber E (2015) The flammability of forest and woodland litter: a synthesis. Current Forestry Reports 1, 91-99.
| Crossref | Google Scholar |

Viegas DX, Piñol J, Viegas MT, Ogaya R (2001) Estimating live fine fuels moisture content using meteorologically based indices. International Journal of Wildland Fire 10, 223-240.
| Crossref | Google Scholar |

Wagner MR, Clancy KM, Tinus RW (1990) Seasonal patterns in the allelochemicals of Pseudotsuga menziesii, Picea engelmannii and Abies concolor. Biochemical Systematics and Ecology 18, 215-220.
| Crossref | Google Scholar |

Weise DR, White RH, Beall FC, Etlinger M (2005) Use of the cone calorimeter to detect seasonal differences in selected combustion characteristics of ornamental vegetation. International Journal of Wildland Fire 14, 321-338.
| Crossref | Google Scholar |

White CS (1994) Monoterpenes: their effects on ecosystem nutrient cycling. Journal of Chemical Ecology 20, 1381-1406.
| Crossref | Google Scholar | PubMed |

White RH, Zipperer WC (2010) Testing and classification of individual plants for fire behaviour: plant selection for the wildland–urban interface. International Journal of Wildland Fire 19, 213-227.
| Crossref | Google Scholar |

Zou JP, Cates RG (1995) Foliage constituents of Douglas fir (Pseudotsuga menziesii (Mirb) Franco (Pinaceae) - their seasonal resistance and silviculture management. Journal of Chemical Ecology 21, 387-402.
| Crossref | Google Scholar | PubMed |