BARK PROPERTIES AND FIRE RESISTANCE OF SELECTED TREE SPECIES FROM THE CENTRAL HARDWOOD REGION OF NORTH-AMERICA

Some physical, thermal, and chemical properties of bark of 16 tree species native to the central hardwood region were measured to determine their potential to protect the vascular cambium from damage by fire. The relationship between DBH and bark thickness for each of 16 species was determined. For purposes of monitoring seasonal trends, two species (Quercus macrocarpa Michx. and Acer saccharinum L.) were sampled periodically during one growing season. Temperature response to bark surface heating of 11 species was monitored at the cambial layer during simulated fires conducted in the field. Bark samples were analyzed for moisture content, specific gravity, dry weight, volatile matter content, and time until ignition. Overall, during simulated fires, temperature gradients were decreased and maximum cambial temperatures were reduced as bark thickness increased. Thick-barked species had lower maximum cambial temperatures, longer times to reach peak temperatures, slower rates of heat loss, and shorter time until surface ignition. Populus deltoides Marsh. was the most heat resistant among species tested, while Acer saccharinum was the least. Higher specific gravities were associated with higher rates at which cambial temperatures rose as well as with increased time required for surface ignition.