Lightning Fires in Southern Appalachian Forests

The purpose of this study was to describe characteristics of lightning fires, including frequency, size, season and severity, and to determine their effects on the composition of pine-hardwood stands in the Appalachian Mountains of Tennessee and North Carolina.

An analysis of fire reports from Great Smoky Mountains National Park and from Cherokee, Nantahala and Pisgah National Forests, an area of 800,000 ha, shows that during 1960-1971 there was an average of six lightning fires per year per 400,000 ha (one million acres). The median size of lightning fires was 0.8 ha and the largest 33 ha. More than 90 percent of all lightning fires occurred during April through August with the highest frequency in May. Lightning fires tended to be much less severe than man-caused fires. No lightning fire on record was crowning when the fire crew arrived.

An analysis of the effect of 13 fires on the composition of pine-hardwood stands in Cherokee National Forest and Great Smoky Mountains National Park suggests that lightning fires generally caused small changes in the pine/hardwood basal area ratio, due primarily to differential survival of pine and hardwoods. Southern pine beetles (Dendroctonus frontalix Zimm.) attacked pine on two of the sites of lightning fires, reducing the percent pine in the total basal area from 70 percent to about 25 percent.

If lightning fires were permitted to burn in Great Smoky Mountains National Park, the probably would not maintain the widespread pine forests which now clothe southern slopes at lower elevation. However, such fires may permit enough new pine reproduction on dry ridges to preserve Table-Mountain (Pinus pungens Lamb.), pitch (P. rigida Mill.), shortleaf (P. echinata Mill.) and Virginia pine (P. virginiana Mill.) as fugitive species in the Park.