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

Le résumé fourni par la source

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.

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