Quantifying the flammability of living plants at the branch scale: which metrics to use?

Background Plant flammability is an important factor in fire behaviour and post-fire ecological responses. There is consensus about the broad attributes (or axes) of flammability but little consistency in their measurement. Aims We sought to provide a pathway towards greater consistency in flammability research by identifying a subset of preferred flammability metrics for living plants. Methods Flammability was measured at the branch scale using a range of metrics for 140 plant specimens in an apparatus that simulates an approaching fire front. Key results We identified a subset of preferred metrics, which quantify the axes of flammability for living plants, including time to ignition (ignitability), peak heat release rate (combustibility), flaming duration (sustainability) and consumption (consumability). Flaming duration was strongly correlated with heat release rate, so could be a proxy for combustibility. Flammability was higher for species with greater surface area and biomass per branch. Conclusions We identified a subset of preferred metrics for quantifying the flammability of living plants. These metrics quantify the key axes of flammability and are measurable using different experimental apparatus and across multiple scales, making them suitable for widespread use. Implications The inclusion of these flammability metrics in future studies has the potential to enhance consistency and comparability between studies.