Interpreting shoot flammability experiments: from fire behaviour to plant evolution

Abstract

Interpreting shoot flammability experiments: from fire behaviour to plant evolutionWildfires are a natural phenomenon in many terrestrial ecosystems. However, human activity is changing fire regimes. Some argue that the frequency of extreme wildfire events, characterized by very high intensities and rates of spread, may be increasing (Duane et al., 2021). Ecologists have sought to clarify whether differences in species traits may affect such patterns of fire behaviour by assessing fuel flammability. Experimental quantifications of leaf flammability have become widely available. However, they have been largely confined to measurements under laboratory conditions. This hinders extrapolation into real wildfire events, especially under conditions leading to extreme blazes. Despite such limitations, this research has awakened public interest. It is now common to read headlines in major media outlets, stating that species identity is a major driver underlying forest fire behaviour. This is particularly the case where tree plantations with non-native species are widespread, such as the Southern Cone or the Iberian Peninsula (Ames, 2017). This has important implications for the current discussions on creating fire-smart landscapes. These are landscapes that lead to low-intensity and less severe fires. In an article published in this issue of New Phytologist, Cui et al. (2023; 105-113) take this research one step further and examine the extent to which shoot flammability is affected by climatic drivers. A key question arising from these measurements is whether shoot-level measurements inform on actual fire behaviour. In other words, whether and how does fire intensity and rate of spread scale with flammability, as we move from leaves to shoots, to stands, to landscapes and beyond.