A landscape-scale experiment in restoring Ozark glades

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By Diana Lutz  January 27, 2012

A giant experiment is under way at the Tyson Research Center, Washington University in St. Louis’ 2,000-acre outdoor laboratory for ecosystem studies.

The experiment, led by Tiffany Knight, PhD, associate professor of biology in Arts & Sciences, will test three different variables in 32 glades with the goal of establishing best practices for restoring not just degraded glade habitats but degraded ecosystems in general. 

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“These glade restorations are going to be a really significant scientific resource, not just for people at Washington University but for people both nationally and internationally,” says Barbara Schaal, PhD, professor of biology and director of the Tyson Research Center. 

“The opportunity to do giant manipulations and experiments is really rare, and we expect this experiment is going to draw researchers from all over the world,” Schaal says.

Missouri glades, which ecologists sometimes call sunlit islands in a forested sea, are areas of exposed bedrock in the Ozark woodlands that create their own hot, dry, desert-like microclimates and have their own unique mixture of species, including tarantulas, scorpions, and prickly pear cactus. 

Before people settled the area, glades covered the Ozark mountain hilltops and oaks nestled in the valleys between ridges. When fires were suppressed after World War II, eastern red cedar — once confined to river bluffs — and rock outcrops invaded the glades, completely altering the character of these habitats and the mixture of species that lived there.

Knight’s group prepared for restoring the Tyson glades by surveying about 30 other glade restorations elsewhere in the state. “We expected smaller stored glades to have fewer species than larger glades, but we found that they had even fewer than we expected and they were also more impoverished in rare species than we expected,” Knight says.

So they decided to find out why by running the restoration of 32 glades at Tyson as a scientific experiment, complete with treatment groups and control groups.

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“We’re manipulating glade shape, we’re manipulating glade size, and we’re manipulating whether or not plant species are seeded or allowed to establish on their own,” Knight says. “Those are our three big treatments, and then we’ll judge the outcome by measuring the biodiversity and composition of plants.

“Glades are biodiversity treasure chests,” Knight says. “This study focuses on a unique Ozark glade ecosystem that has been a home to many rare and endangered species found nowhere else in the world. 

“Our results will have important implications for understanding and trying to mitigate biodiversity loss from small habitats, especially loss of rare species.”

On the way to the fire

In 2009, areas at the Tyson Research Center that had historically been glades were cleared by ax and chainsaw. These openings are now being maintained — as they traditionally were — by fire. 

The prescribed burns began the week of Jan. 9, 2012. With weather conditions perfect, the glades were being burned, at the rate of about two a day. Knight picked up the videographer and reporter at the research center to drive them to the fire site. (See movie below).

Tiffany Knight explains the glade restoration experiment on the day of a prescribed burn.
“Usually there are several clues that an area was a glade,” Knight said over the rumble of the pickup. “When you’re driving along, you’ll see big boulders and rocks right on the surface of the soil. What that tells us is the soil is really shallow, which is characteristic of a glade habitat.

“Another thing you’ll notice, especially in aerial photographs taken in winter, is eastern red cedar. The southwestern corner of the Tyson Research Center is covered with it. Eastern red cedar is the first plant to encroach on glades in the absence of fire. If fire is suppressed, eastern red cedar comes in, gets established, and allows the glade habitat to succeed into a forest.

“Another telltale sign is plants that are remnants of glades. I’d be walking through the forest doing other research,” Knight says, “and I would notice plant species like cactus in the middle of the forest. It was clearly a species just trying to hang on, waiting for the day when the habitat became a glade again.

“All of these are good indicators that an area was a glade historically,” she says.

By now we had arrived at the next glade to be burned, a big, round glade with a southern exposure that had been strewn with the seeds of glade-favoring species.

At the fire

“Fire travels uphill,” Knight says as we get out of the pickup, “so they burn the top of the hill first — a small, low-intensity burn — so that when they light the bottom and the fire moves up, there’s no way for it to ignite the slash (piles of timber and brush) left over from glade clearing.”

The crews are motley: half pros, half students. One of the teams is led by John Timmerman, a retired firefighter who now does prescribed burns. Another is led by John Wingo, a contractor whose business is ecological restoration. They wield the drip torches and leaf blowers (used to extinguish small flames).

Even though it’s winter break students are scraping out the fire break around the glade and are raking embers back into burning piles of vegetation.

“The research involves scientists at all levels: faculty, postdoctoral associates, graduate students, undergraduates and high school interns,” Knight says. 

“My only job at these fires,” Knight says, “is to look outside the fire circle and make sure flying sparks haven’t set anything alight. 

“This glade was seeded,” Knight says, walking by the flaming stalks of wooly mullein, “by a striking plant that is adapted to live in disturbed landscapes, but will eventually be outcompeted by returning glade species.

“We put in 50 species, and we went to extra effort to get some of the rarest species in there, some that are listed by the state or federal government as threatened and others that grow only in glade ecosystems.”