Palaeobotanists use the charred remains of ancient flowering plants found in the fossil record to study the evolution of the first angiosperms. These charred remains are left over from wildfires but the field is only now realising that what is accessible in the record is possibly only a fraction of the first flowering plants on earth due to the nature of fire itself.
When fires burn coolly it produces charcoal which can be preserved in fossils for millions of years. High intensity fires on the other hand incinerate plant matter to ash, destroying evidence of their existence on earth.
Published recently in Geology, Victoria Hudspith and Claire Belcher have demonstrated that different plants caused fires to burn differently, with some resulting in hotter fires while others burned much more coolly. The also found that the floral structure of different plants made them more likely to either be preserved as charcoal or entirely burned away into ash.
Grayscale photographs of post-burn residues containing char and ash from flowers and associated vegetative material. A: Spikes of Anemopsis californica. B: Spadix of Spathiphyllum wallisii flowers. C: Laurus nobilis flowers clustering in leaf axils (see arrows). D: Differential charcoal production of small isolated charred Cinnamomum camphora flowers compared to ashed leaves, tested under the same conditions. E: Intact charred Schisandraceae: Calycanthus occidentalis flowers; even detached tepals remain as char post-burn (see arrows). F: Intact charred Schisandraceae: Illicium cf. henryi flower. Scale bar in all images is 20 mm.
The results are important for those studying the evolution of flowering plants, as the structure of flowers that were likely to be preserved for us to find them millions of years later might only show us a fraction of the diversity that existed at the time.