Fire is increasingly being recognised as an important evolutionary driver in fire-prone environments. Biochemical traits such as terpene (volatile isoprenoid) concentration are assumed to influence plant flammability but have often been overlooked as fire adaptations. We have measured the leaf-level flammability and terpene content of a selection of Pinus species native to environments with differing fire regimes (crown fire, surface fire and no fire). We demonstrate that this biochemical trait is associated with leaf-level flammability which likely links to fire-proneness and we suggest that this contributes to post-fire seedling survival. We find that surface-fire species have the highest terpene abundance and are intrinsically the most flammable, compared to crown-fire species. We suggest that the biochemical traits of surface fire species may have been under selective pressure to modify the fire environment at the leaf and litter scale to moderate fire spread and intensity. We indicate that litter flammability is driven not only by packing ratios and bulk density, but also by terpene content.

Global warming events have coincided with turnover of plant species at intervals in Earth history. As mean global temperatures rise, the number, frequency and duration of heat-waves will increase. Ginkgo biloba was grown under controlled climatic conditions at two different day/night temperature regimes (25/20 °C and 35/30 °C) to investigate the impact of heat stress. Photosynthetic CO₂-uptake and electron transport were reduced at the higher temperature, while rates of respiration were greater; suggesting that the carbon balance of the leaves was adversely affected. Stomatal conductance and the potential for evaporative cooling of the leaves was reduced at the higher temperature. Furthermore, the capacity of the leaves to dissipate excess energy was also reduced at 35/30 °C, indicating that photo-protective mechanisms were no longer functioning effectively. Leaf economics were adversely affected by heat stress, exhibiting an increase in leaf mass per area and leaf construction costs. This may be consistent with the selective pressures experienced by fossil Ginkgoales during intervals of global warming such as the Triassic - Jurassic boundary or Early Eocene Climatic Optimum. The physiological and morphological responses of the G. biloba leaves were closely interrelated; these relationships may be used to infer the leaf economics and photosynthetic/stress physiology of fossil plants.

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Here, we explore how charcoal formation under different heating regimes and circumstances leads to chars of different physical properties. In order to do this, we have undertaken (1) carefully controlled laboratory experiments that replicate the different heating regimes that might be experienced during a wildfire and (2) two experimental wildfires where heat variations were monitored across the burn from which resulting charcoal has been studied. The charcoal properties were assessed using charcoal reflectance that measures the light reflected back from the charcoals structure and which links to changes in its structural properties. We find that increased total heat released during combustion positively correlates with increased charcoal reflectance and that this is evidenced from both our laboratory experiments and experimental wildfires. Charcoals that related to lower total heat release were found to have more lignin remaining than those subjected to greater heating indicating that charcoals formed in lower energy regimes are likely to be more susceptible to post-fire degradation. We conclude that charcoal reflectance may make a useful metric with which to determine the distribution of energy delivery across a burned area and that this may be utilized to inform both variations in fire severity and enable the prediction of long-term C budgeting for different types of wildfire.