JOINT BASE LEWIS-MCCHORD, Wash., Sept. 8, 2011 -- The site of a fire burning across a stretch or prairie is usually one that would inspire panic. The fire on Roger's Drop Zone last week was all part of a plan, however. Prescribed burns, or small, controlled fires set by professionals, take place each year on Joint Base Lewis-McChord's 12,000 acres of prairie.

"Typically the prairie ecosystem is evolved with fire as part of the process," JBLM Fish and Wildlife Program Manager David Clouse said.

It seems counterintuitive -- setting something on fire to preserve it. In fact, many of the native plant species on Washington's prairies depend on seasonal fires to survive. The burns reduce the fuel load (and the risk of future fires) and stimulate seed germination for the future, creating hardier plants.

They also kill off non-native plants, like the yellow Scotch broom that's become so common in the area.

"Fire is a natural process," explained Bob Wilken, a burn boss with the Nature Conservancy.

Wilken was in charge of burning 140 acres on the drop zone on Aug. 25. He oversees three to four prescribed burns each week on JBLM, as conditions allow.

The hope is to rotate through training areas so each part has a fire about once every three years. This not only keeps the prairies healthy, it keeps them clear of debris and ready for training.

The process isn't always a simple one, however. The conditions surrounding the fire must be just right in order for it to be a safe, productive experience.

Burns never take place when there are burn bans related to air quality, but frequently occur when there are bans because it's been hot and dry. For the controlled fires, the less moisture the better. But that's just the beginning of the science that goes into the process.

Wilken and his team also have to factor in wind and weather, how much smoke each fire could produce and where it could end up. They also have to make sure the fire stays within a specific area.

"We don't do any fire activity without things in place and a plan," he said.

The fires are a collaboration between JBLM Fish and Wildlife, the Nature Conservancy and the Department of Natural Resources, and take place each summer as soon as it's dry enough to burn. They'll continue until the opposite happens, and the weather becomes cool and damp in fall.

Following a pre-burn briefing, the team (usually made up of at least 10 to 12 people) went to their designated locations, some taking torches to the outer edge of the space, others burning setting fires in the middle.

Each group worked in a specific pattern. Those on the edges hooked the fire in toward the middle, created vortices of smoke spiraling above the prairie.

"By itself, fire is a very slow, gentle animal," Wilken said before going out to watch the process from the top of a truck.

Burning 50 to 80 thousand acres across the country each year for 36 fire seasons has taught him that enough fuel and a slight change in circumstances can make that change in an instant, however. He loves his job -- but knows he has every reason to take it seriously.

The prairie changed almost as soon as the fire hit. Dry brown grass shriveled up instantly, leaving behind native bushes in a bed of charcoal.

By next year, though, the area will be ready to be re-inhabited with the huge number of plant and animal species that live in the area -- and the process of burning and growing will start all over again.