SEASONAL VARIATION IN FLAMMABILITY CHARACTERISTICS OF QUERCUS MARILANDICA AND QUERCUS STELLATA LEAF LITTER BURNED IN THE LABORATORY

Historically, the Cross Timbers forest of Oklahoma, Kansas, and Texas burned frequently. Fire managers in the region often have varied success when conducting prescribed fires, with one hypothesis being that fuel quality varies with litter age. This study was designed to determine the time-since-leaf-fall flammability characteristics of the two dominant tree species in the Cross Timbers, Quercus marilandica and Q. stellata. Principal components analysis indicated that the burn characteristics of both species are strongly influenced by time since the onset of leaf fall. The percent consumption of leaf litter and flame time of the two species began to diverge at 123 days after leaf fall and continued throughout the remainder of the study. There was no difference between the other flammability characteristics of ember time, total burn time, average temperature, and maximum temperature. Fuel consumption and fire behavior in hardwood leaf litter fuels can vary considerably, possibly as result of fuel mass loss from decomposition, which may due to a loss of flammable material. Our results show that the longer the time period from leaf fall to burn, the greater the change in burn characteristics of these two Quercus species. By identifying these similarities and differences between the leaf litter of dominant tree species, fire managers can adjust fire prescriptions to better meet burn objectives.