Tree mortality following a drought-year lightning ignition in the Ouachita Mountains, Arkansas: 2 years postburnThis article is part of a larger document. View the larger document here.
Increasingly, fire managers are using natural ignitions in conjunction with prescribed burns to restore and maintain fire-adapted ecosystems. Increased fuel loading from fire suppression and increasing drought indices associated with climate change, however, may cause natural ignitions to burn with greater intensity and severity. Managers must weigh risk factors versus benefits before allowing a lightning ignition to burn under these conditions. During the severe drought of 2011, the Ouachita National Forest had more lightning ignitions than any year in recorded history. While most were fully suppressed, one lightning ignition occurred in a particularly remote and rugged location that made suppression difficult and unsafe. Managers decided to use “less than full suppression” techniques and allowed this fire to burn within a designated containment area (~700 ha). Given the drought conditions, there was concern that significant overstory mortality would occur. We installed 32 randomly placed 10-m-radius circular plots directly after the fire in three community types: hardwood forest, pine-oak forest, and pine plantation. We identified and measured all trees =2.5 cm diameter at breast height (dbh) and determined scorch height and percentage, char height, and live or dead status. Plots were remeasured 1 and 2 years postburn to determine mortality. Overstory (>15.0 cm dbh) and midstory (=15.0 cm dbh) stem densities were reduced significantly 1 year postburn by 5 and 64 percent respectively, but not significantly between 1 year postburn and 2 years postburn. The long-term outlook for the Southern Region includes hotter and drier conditions. This study provides resource managers with information on tree mortality following a lightning ignition during a drought in the High Peak area of the southeastern United States, and will allow more informed decisions to be made on the necessity of suppressing wildfires versus using them to restore and maintain forest structure and composition.