Fuel consumption and fire characteristics during understory burning in a mixed white pine-hardwood stand in the Southern Appalachians.
We characterized tire behavior and fuel consumption resulting from an understory prescribed burn in a mixed eastern white pine-hardwood stand in the Southern Appalachians. These stands were used for the treatment. Flame lengths, ranging from 0.3 to 1.5 meters (m) for backing fires and from 1.2 to 4.5 m for head fires, reached maximum heights where evergreen understory was found. Rates of spread ranged from 1.8 to 3.0 m per minute for head tires and 0.3 m per minute for backing tires. Fire intensity, measured with ceramic tiles painted with heat-sensitive paint, varied across stands. Mean peak flame temperature ranged from 129 to 290 ?C. Pre-burn mass totals were similar among stands, except for stand 1, which had substantially greater humus mass than the other stands. Consumption of litter and humus layers in the forest floor was positively correlated with flame temperature. Small wood (c8 cm diameter) consumption was not correlated with temperature. Over all stands, 50 percent of the mass in small wood and litter was lost during burning, and 20 percent of the humus layer was consumed. The losses in the humus layer represent about 40 percent more humus mass consumption than would have occurred in a fell-and-burn treatment. The humus layer is an important nutrient reservoir for plant growth. Maintaining this layer through careful selection of burning conditions will minimize losses during burning and maintain long-term site productivity.