Charcoal chemistry : developing a proxy for paleofire regimes.

Wildfires have occurred over geologic time since the evolution of land plants and affect global biogeochemical cycling and ecosystem processes. Charcoal particles in the geological record may contain information on several aspects of paleowildfire regimes. The fire intensity, the energy produced during a fire, is poorly understood for fires that occurred in the past. I propose that the organic chemical composition of charcoal may be used to approximate the fire temperature. To test this, I used 13C nuclear magnetic resonance (NMR) to quantify the carbon bonding environments in charcoal particles derived from specimens burned during a prescribed fire at the Lake Waco Wetland in Waco, Texas. I compared the NMR data for charcoal to fire temperatures measured by thermocouples and was able to predict the temperature within 89°C. The intrinsic relationship between pyrolysis temperature and charcoal structure may allow for a better understanding of past conditions during fires.