Leaf flammbility and volatiles of Ginkgo, Agathis, and Dicksonia

The Triassic-Jurassic Boundary marks the third largest mass extinction
event in the Phanerozoic, characterised by a rise in CO2-concentrations
from ~600 ppm to ~2100 – 2400ppm, coupled with a ~3.0 – 4.0°C temperature
rise. This is hypothesized to have induced major floral turnover, altering
vegetation structure, composition and leaf morphology, which in turn are
hypothesized to have driven changes in wildfire. However, the effects of
elevated CO2 on fuel properties, such as chemical composition of leaves,
are also important in influencing fire behaviour, but yet have not been
considered. We test this by selecting three Triassic analogue species
grown experimentally in different atmospheric compositions, and analyse
variations in leaf chemistry, and leaf level flammability. These data were
used to inform a fire behaviour model. We find that all three species
tested showed a reduction in their volatile component, leading to lower
flammability. Accounting for these variations in a model, our results
suggest that leaf intrinsic flammability has a measurable impact on
modelled fire behaviour. If scaled up to ecosystem level, periods of
elevated CO2 may therefore be capable of inducing both biochemical and
morphological changes in fuel properties, and thus may be capable of
influencing fire behaviour.