Calibrating Oxygen-Isotope Values of Plant Char to Pyrolysis Temperatures
Abstract
Our objective was to improve a model that relates d18O of plant char to burn temperatures to understand forest fire intensity, by considering species effects. Wood, bark and leaves from different tree species were charred for 30 min at 200-900˚C. Lignin and holocellulose were extracted from each tissue and species to determine their weight percent. Overall, d18O of char decreased with increasing temperature. This trend was not a result of exchange with water vapor because d18O of char from dried and undried wood were not significantly different. The proportions of holocellulose and lignin in different tissues or the same tissues among different species did not consistently influence the loss of 18O from char with increasing temperature. However, the differential thermal stability of biochemicals contributed to the decrease in d18O with increasing temperature. The d18O of plant char can serve as a tool to identify forest fire intensity qualitatively.