A few times a year, when the humidity and the temperature and the wind are just right, Brian Hahn and Jeff Ulrick set fire to the N.C. Museum of Natural Sciences.
Not the four-story building downtown, of course, where thousands of schoolchildren go each year to see shark skeletons and a two-toed sloth. Hahn and Ulrick perform their pyro magic at the museum’s 45-acre outpost in far west Raleigh called the Prairie Ridge Ecostation.
Since the museum acquired the land in the mid-2000s, it has been working to restore some of the former N.C. State University pastureland to the way it might have looked to Native Americans and early European settlers. Along with forest, ponds and a stream, the acreage includes land that museum scientists say was likely a Piedmont prairie, dotted with the occasional longleaf pine or other indigenous tree, and covered in tall grass.
Concentrating on plots of 2 to 3 acres at a time, workers have removed cultivated fescue grass and other non-native plantings and sown the seeds of prairie grasses that belong here: switchgrass, Indiangrass, big bluestem and purpletop. Each plot is then managed in a repeating three-step pattern. One year, the grass gets mown down. The next near, it’s left fallow. The year after that, it’s burned.
That’s where Hahn and Ulrick come in with their drip torches and fire rakes, tools of the prescribed burn. Hahn, natural resources manager for the museum, works closely on the burns with Ulrick, who’s a ranger and a fire equipment manager for the N.C. Forest Service.
They demonstrated their technique Saturday to a handful of members of the Friends of the Museum. In January, the pair had an audience of about 60, including home-school groups, when they burned an entire section.
“Want to set something on fire?” Ulrick asked Saturday, picking up a can of a diesel-and-gas mixture and applying it to a pile of cut grass at the corner of a field. Hahn went behind him with a lighter.
Over the past couple of decades, forest managers have touted the use of low-burning controlled fire to promote healthy forests. The occasional fire reduces fuel on the forest floor that feeds wildfire, advocates say; it lets in sunlight so new growth can sprout, providing food for foraging wildlife; and in some ecosystems, it provides the heat required for certain seeds to open and grow.
At the Prairie Ridge Ecostation, Hahn said, it’s an expedient way to clear the land, while the ash puts nutrients into the soil.
“It’s one of the healthiest things you can do to rejuvenate the prairie, or the forest,” Hahn said. To make sure flames stay low and the fire behaves according to the “prescription,” Hahn and Ulrick limit the fire’s access to at least one of the three things it must have: fuel, oxygen and heat. Fire breaks, lines where bare earth has been exposed, help to control access to fuel. A rubber flap on the end of a pole cuts off oxygen, suffocating wayward embers. A handheld water can with a pressurized nozzle, and a truck with a water tank parked nearby, can be used to reduce heat.
After Saturday’s demonstration, Hahn invited children in the group to try their skill with the small watering can, called an Indian pack. Seungkwon Kang, 7, and his sister, Seungjoo, 5, aimed the stream at painted flames on a board – hinged from behind, like targets in a carnival shooting gallery – and knocked them down.
Controlling a real fire isn’t always as simple. The January burn jumped a fire break and ended up burning a section of grassland where Hahn and Ulrick had not meant to work.
When the museum isn’t torching the prairie land, it hosts other activities at the ecostation such as weekly science walks on Saturday mornings and nature stories on Thursday mornings. The site includes Nature Play Space, a playground featuring a “groundhog tunnel,” a mini-maze and places for digging and water play, climbing over logs and rocks and rolling in the grass.