Area-volume relationships for fossil charcoal and their relevance for fire history reconstruction

Sedimentary charcoal is a widely used tool for reconstructing past fire histories. These fossil charcoals are normally quantified as the number or area of particles present in a sediment sample, but it is not known how well either measure is correlated with their volume. Areal measurements are often treated as the true measure of quantity, which may introduce bias to fire histories. The relationship of measured area to volume is a function of shape, and if this relationship can be understood, areal measurements may be adjusted to better reflect volume. We show that particle elongation may be particularly important when making such adjustments. We also establish a high degree of correlation between volume and area in a mid-Holocene mesocharcoal assemblage, which indicates that the bias may be small in similar cases.