Tornadoes and Fire

A flight over the park revealed the wide swath of downed forest after the tornado.

NPS photo.

Tall trees uprooted, tossed, and broken in half like twigs. Main park trails piled head-high with a tangle of debris, mile upon mile. And an entire forest changed: these are the widespread impacts that resource managers at Great Smoky Mountains National Park discovered following a tornado and violent storms that ripped across the park April 27, 2011.

The tornado—a Category 4, packing winds from 166 to 200 mph—shut off recreational access to large areas of the park’s northwest corner for months. But the storm’s changes to park forests may last for decades or even centuries to come. If you’ve ever been to the western side of the Smokies, you would recognize the drier soils and towering, fluffy-crowned pines of its higher, sunny ridges. This is a forest type that thrives with regular fire: its yellow pines and chestnut oaks, among other species, have thick gnarled bark to withstand regular scorching, and its trees grow best in an uncrowded, fire-cleared understory.

Following decades of fire exclusion in National Parks and Forests, these xeric, or dry habitat, pine-oak forests have been disappearing. To restore them, fire managers began using controlled burns, and over the past decade have planned and set low-intensity, controlled fires in special long-term burn units. The relatively low-temperature fires smolder and creep along the ground, drawing down piled debris, undergrowth, and encroaching plants without harming large, fire-adapted trees. The result is a healthier native forest.

 

Controlled burns create a lot of smoke, but the flames creep along the ground as seen in this grassland burn unit.

NPS photo.

In the northwestern area of the park, the first stages of fire reintroduction had been going well. Pitch and Virginia pines were maturing, and would soon drop seeds to sprout in the newly opened, sun-drenched habitat. The tornado, however, changed everything. To a forest, a tornado is neither good nor bad: it is a natural weather event. To park managers, however, a tornado presents many different types of challenges. Foremost among these is the ability to fulfill the National Park Service’s mission to preserve and protect ecological systems while providing for the enjoyment of visitors. In the Smokies, massive amounts of human-power, in the form of trail crews from around the country, restored visitor access to trails. Long-term restoration of this area’s native forest communities is harder to put back on track.

The future of fire
The park’s fire reintroduction programs will continue park wide, though the role of fire over the coming years is less clear in areas hardest hit by the tornado. As the fire management team scrambled over debris at Beard Cane and Hatcher Mountain, two fire units that had responded well to controlled burns, they noted many challenges. Using controlled fire means planning within a very strict set of weather and fuel (such as leaf litter) moisture conditions. The tornado has left us with acres of fallen, drying debris piles, huge canopy openings where large trees once stood, and large, loose piles of dirt called “tip-up mounds” exposed as tree roots were wrenched from the ground. These conditions are hard to work in and harder to plan for because they are so varied. In addition, few mature pines or oaks still stand, limiting regeneration, and more sunshine reaches newly exposed soil, encouraging a new plant layer to sprout. Future treks into the tornado-affected area will provide answers to what species will move into these areas, as will simply waiting to see how the forest responds naturally. What fire managers do know is that as rare as tornadoes may be in the Appalachian Mountains, they reveal just one of many complexities in efforts to restore fire-dependent, disappearing native forests.

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