New research in Geography at the University of Exeter is developing a charcoal reflectance methodology into a novel metric with which to assess fire severity and the amount of energy that has been delivered across burned areas in the UK, USA and Brazilian Amazon.
The ability to better understand the effects of fires on ecosystems is critical for future policy and management strategies especially as in some regions of the Earth fire is predicted to become a more prevalent and catastrophic disturbance. For example, the number of fires in Amazonia has had a sharp increase over the past year. Current work by Brazilian post-graduate students in the Amazon Fire Project is evaluating how fire affects tropical forest vegetation and how tree and liana regenerate post-fire (Prestes et al. 2020 and Santos et al. in prep.) in areas of southern Amazonia. The new charcoal reflectance method could help to understand how fire behaviour varied across the burned areas and improve understanding of drivers of variation in post-fire vegetation regrowth.
The work was part of PhD research by Dr Stacey New, with laboratory work in the WildFIRELab at the University of Exeter, under the supervision of Professor Claire Belcher and Dr Ted Feldpausch. Using reflected-light microscopy (Photo 1) in the laboratory Dr New analysed charcoal to improve the understanding of fire behaviour. Charcoal is a key product of wildfire, resulting from the incomplete combustion of fuel. During its creation, charcoal undergoes various phases in which cells are eventually re-ordered to a more graphite-like structure. This re-ordering of cells alters the reflective properties of the charcoal i.e. there is an increase in the quantifiable amount of light reflected from the surface of the charcoal thus allowing researchers to study the reflectance properties of charcoal (Photo 2). It has been suggested that charcoal properties may be capable of capturing evidence of the heat distribution throughout a wildfire. As such, charcoal may provide a way to assess fire severity and the amount of energy that has been applied to fuel to create charcoal.
In this research, Dr New developed the measurement of charcoal reflectance to study charred remains of vegetation from a number of varied ecosystems, including different fire regimes and fuel types. The current multi-biome analysis builds on previous work using reflectance analysis to study fire properties in heathlands (New et al. 2018). Ultimately, developing charcoal reflectance into a post-fire assessment tool has the potential to assist in future policy and management decisions, and in predictions of carbon budgeting for ecosystems.
Picture 1: Image of the reflectance microscope being used by Dr Stacey New to analyse a resin block which contains embedded charcoal from fires (photo credit: Dr Chris Boulton).
Picture 2: Images of charcoal reflectance under the reflectance microscope. The reflectance values for the pieces of charcoal are: a) 0.15%, b) 0.71, c) 2.33%. These charcoal samples were taken from a heathland fire in Carn Brea, a study site in Cornwall UK (photo credit: Dr Stacey New).
Text: Stacey New and Ted Feldpausch