Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Geology

Supervisor

Dr. Elizabeth A. Webb

Abstract

This study assessed whether variations in the oxygen-isotope compositions of char formed from biomass burning could be related to burning severity. Ground samples of oak (Quercus alba), pine (Pinus resinosa), and grass (Andropogon gerardii) were charred for 5 and 30 minutes at constant temperatures between 200 and 900°C under oxygenated versus anaerobic conditions. Char oxygen-isotope values became progressively depleted of 18O by up to 25.8‰ for wood and 16.5‰ for grass as temperature, duration of burning, and amount of oxygen increased. The primary reason for the decrease in oxygen-isotope values is the loss of 18O-enriched compounds such as cellulose at lower temperatures (300-600°C). The large shifts in oxygen-isotope values observed in this study for charred plant species suggest there is potential to use the oxygen-isotope values of char to estimate fire severity and reconstruct paleo-fire dynamics (e.g., spreading rates, fuel types, degree of burning, etc.) from char preserved in soils.


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