Laboratory production of Vouchered reference charcoal from small wood samples and non‐woody plant tissues

Abstract

Taxonomic identification of small fragments of burned plant tissue in lake sediment profiles can enhance reconstructions of past vegetation, fire regimes, and climate. Vouchered reference collections of charcoal prepared from both soft and woody plant tissues, analogous to modern pollen reference collections, will be required for making rigorous identifications and for knowing the level of certainty achieved. Published methods of laboratory production of charcoal may only poorly mimic pyrolysis as it occurs in wildfires, and tend to require large volumes of plant material. We present a method for preparing reference charcoal from dried plant specimens that is simple, provides a high degree of control, yet requires only small tissue samples. Based on results of a series of experiments, we recommend placing dried samples in 25 cm3 perforated‐base porcelain Gooch filtering crucibles, surrounded by 250–500 μm sand; saturating the sand with water and draining; and placing for eight to nine minutes in a furnace heated to 550°C. The wet sand delays heating so that temperature rise is steep. Pyrolysis is brief and occurs under hypoxic conditions due to temporary oxygen flushing by water vapor. Using our method we achieved excellent results on both woody and soft tissues from a variety of plant taxa.