The taphonomy of charcoal following a recent heathland fire and some implications for the interpretation of fossil charcoal deposits

In May 1995, fire burnt an area of heathland with stands of pine and birch trees in the Frensham Common Country Park near Tilford in Surrey, southeast England. Extensive areas were burnt by a rapidly spreading surface fire, and charcoal was produced from both the living plants and plant litter. Flames reached a height of no more than 2 m so that whilst much of the low growing vegetation was destroyed, the trees generally survived the burn. Samples were taken of unburnt living plants and unburnt litter as well as charcoal from heathland and adjacent woodland and small channels running through the locality. Much of the heathland charcoal was produced from living vegetation and included wood, leafy shoots, flowers and fruits of Calluna vulgaris (common heather) and rachises and pinnae of the fern Pteridium aquilinum (bracken). The surface peaty layer here was only charred to a depth of 1 or 2 mm. In contrast, the bulk of the charcoal from the Pinus sylvestris (scots pine) and Betula pendula (silver birch) trees was from litter, none of the lower branches of the trees having caught alight. Only a few fallen logs produced much wood charcoal. Fallen P. sylvestris female cones were typically only charred upon their upward-facing surface. Strong winds across the heathland following the fire gathered the charred C. vulgaris small leafy shoots, flowers and fruits into ripple concentrates. Movement of the charcoal by water following rain storms was also tracked from the heathland onto bare crossing paths and into depressions and channels as well as into a small nearby lake. Water transport resulted in selective bias in favour of wood charcoal. None of the other charred organs reached the lake. Scanning electron microscopy shows that a wide range of plant taxa and organs may be anatomically preserved by charcoalification, and plants covered with fungal hyphae (possibly indicating decomposition) were also found charred. Studies of samples in polished blocks show that all plant organs have increased reflectance under oil. Mean random reflectance under oil of all samples was 1.53 (range 0.13–6.22), which indicates that if preserved in the fossil record, they would be classified as the coal maceral semifusinite. Comparisons with fossil deposits are made, and this study may contribute to our understanding of charcoalified flower concentrates (e.g the late Cretaceous of Sweden and the USA) and deposits rich in fern charcoal (e.g. of the early Cretaceous of southern England)