SIGHTLINE

WINTER/SPRING 2002
Vol. 3 No. 1

Cades Cove

What Might Have Been

Trapped in the Cove

Field and Stream

Cove's Changing Landscape

Combating Alien Invaders

Crunching Numbers, Counting Bugs

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Editor: David Brill; Assistant Editor: Constance Griffith; Writers: Kris Christen, Lisa Byerley Gary, Elise LeQuire, Dennis McCarthy, and Becky Nichols. Graphic Designer: Lisa Byerley Gary.

SIGHTLINE is published on behalf of
Great Smoky Mountains National Park
by the
Energy, Environment and Resources Center (EERC)
at the
University of Tennessee.

EERC conducts research designed to promote real-world solutions to problems in the fields of energy, environment, technology, and economic development.

For additional information, write EERC, 311 Conference Center Building, The University of Tennessee, Knoxville, TN 37996-4134, call 865-974-4251, or visit our Web site at http://eerc.ra.utk.edu.

SIGHTLINE is sponsored by:

and

Combating Alien Invaders

Humans aren't the only species whose presence has changed the appearance of Cades Cove.

BY Kris Christen

By pulling, cutting, spraying, and burning, the National Park Service (NPS) hopes to rid Cades Cove, and the rest of Great Smoky Mountains National Park (GSMNP), of non-native species while taking steps to restore its historical vegetative diversity. And that's no easy job, as anyone who has ever tried to maintain a lawn free of dandelionsalso an exotic plant could tell you.

Exotic, alien, introduced, non-indigenous, and non-native are all synonyms for species that humans have intentionally or unintentionally introduced into an area outside a species' natural range. The NPS considers invasions by such species one of the most serious threats facing the parks today.

Second only to roadsides in the Park, Cades Cove hosts the densest population of exotic species in GSMNP, says Jenny Beeler, an NPS biological science technician. In the open areas of the Cove, non-native grasses and weeds such as fescue, lespedeza, clover, and European orchard grass cover close to 95 percent of the land area, Beeler says. In the Cove's wooded areas, another exotic called Microstegium vimineum, or Japanese stilt grass, rules; in fact, Microstegium inhabits as much as 50 to 60

percent of these areas. In all, more than 380 different kinds of nonnative plants currently live in the Park, according to Beeler, and the NPS is actively controlling 50 of the most invasive.

Biggest Threats

Exotics are ranked depending "on the invasiveness of a particular species, how abundant it is in the Park, and how difficult it is to control given what we know about control methods, if anything," Beeler says.

Severe threats, according to the Southeast Exotic Pest Plant Council, include species that spread easily into native plant communities, displace native vegetation, and have the potential for becoming widespread. Significant threats include plant species that don't presently spread quite as easily as those in the severe-threat category, and lesser threats include exotic plant species that spread in or near disturbed areas, but aren't presently considered a threat to native plant communities.

Fescue, lespedeza, and Japanese stilt grass rank as the biggest threats in the Cove as far as exotics go (see box for top 10 list). So far, the Park Service has put a lot of resources into gaining an upper hand over the first two, but nothing has been done yet to counteract Microstegium's advance.

"That's because we're still in the dark about the best way to control it," Beeler says (see boxed story on page 18).

Some of the really bad exotics, though, can be found in the more pristine backcountry, and these are the Park's highest priority, Beeler says. Take the Chinese yam, for instance. It's a vine with aerial tubers similar to tiny potatoes that, when they break off, can fall anywhere and start rooting into a new plant or be transported to another place by animals or unsuspecting hikers, Beeler says.

Many of the exotic inhabitants that threaten the Park's native plant communities were brought in by early settlers. For example, "They brought grass species they were familiar with, as well as a variety of horticultural species, including honeysuckle and ornamental roses," says Kris Johnson, a Park Service supervisory forester. They also brought apple trees, corn, wheat, and sorghum, none of which are a threat.

Still other exotic species were brought in by federal agencies when the Park Service began taking over the land. In the 1930s, "they actually brought in some of the European grassestimothy, orchard grass, and lespedeza because they wanted to make these areas into meadows to lease to farmers for cattle grazing or to mow for hay," Beeler says.

Then, throughout the 1950s, 1960s, and 1970s, the Park Service followed Soil Conservation Service guidelines for ditching and draining wetlands and planting pasture species to increase the amount of available farmland, as well as farm productivity. "That's when most of the lespedeza and fescue were planted," Johnson says, to feed the 600 head of cattle living in the Cove at that time.

R & R: Removal and Restoration

About eight years ago, the Park Service began restoring wetlands and getting rid of exotics in an effort to return Cades Cove to its former vegetative posture. Using study plots to determine the most effective methods for removing various species, Park personnel "worked on multiflora rose, Japanese honeysuckle, and several exotic trees, including tree of heaven, privet, and periwinkle," Johnson says. "This year we really started working hard on the lespedeza."

The Park Service expects its new greenhouse at the Twin Creeks Natural Resource Center to hasten the process of restoring native grasses and wildflowers to the Cove. Because of a mandate to use only species that originated in the Park, seeds for replanting have to be collected within the Park itself, with genotypes from different areas of the Park kept separate, Johnson says.

In the past, the Park sent its collected seeds to the Natural Resource Conservation Service's plant materials center in Beltsville, MD, to be cleaned and propagated. The plugs were then sent back for planting in the Cove. This arrangement placed restrictions on the number of species and the amount of seed that could be sent, Beeler says. "Now we can do all that on our own, and we can do more species and think about more projects that we'd like to produce plants for."

Top 10 Most Severe Exotic Threats Facing Cades Cove

Top 10 Most Severe Exotic Threats Facing GSMNP

The Park now has enough stored seed to begin restoring several acres in the Cove next year, according to Beeler, and that's in addition to the 5000-square-foot demonstration meadow already planted near the old red wolf overlook on the Cove's loop road. So far, this plot holds six different native grass species and five wildflower species. "We planted them like you see them out in the wild," Beeler says. "Some species clump together, and others seem to scatter and go everywhere."

The Park Service is also using the new greenhouse to grow plants for revegetation in areas where there has been construction, Johnson says. "Before the work on the tunnels began on Highway 441, we collected seed from the siteVirginia creeper, virgin's bower, asters, and hydranga and we also salvaged a lot of plants that we're keeping in our shade house." Once the construction project is finished, the seeds and plants will be replanted at the site.

The restoration work will also make life a lot easier for the large number of rare plants inhabiting the Cove, says Janet Rock, the Park's botanist. "We continually monitor rare plant populations in the Park, and although they aren't currently showing any new declines, they're not getting bigger and better, either," Rock says.

Two rare plants that have probably been extirpated from Cades Cove include the purple fringeless orchid and the Virginia chain fern, Rock explains. Other rare plants in the Cove include the marsh bellflower, marsh fern, and American columbo. Threats to these plants are constant, and include such habitat changes as forest succession, deer overbrowsing, and hiker trampling, in addition to non-native plant invasions, she says.

Habitat Renaissance

The Cove's wildlife also stand to benefit from the removal of exotics, especially fescue, Beeler says. Like lawn grass, fescue is a mat-forming grass that makes passage difficult for small mammals and birds. Fescue offers little in the way of nesting opportunities for such animals; however, native warm-season grasses do, says Beeler. And in an ideal meadow, bare ground between these bunch grasses offers travel paths and a means of escape from predators while providing ideal nesting spots for small wildlife.

Moreover, vegetation studies in the Cove have shown that areas of native grasses and wildflowers harbor much more diversity than do fescue fields, fostering an increase of organisms such as insects, small mammals, birds, and others along the food chain, Beeler says. "So all in all, converting fescue fields in the Cove to native species will be beneficial to the entire ecosystem."

One of the biggest problems the Park faces with its Cove restoration work, however, is public perception, Beeler says. "People come through and see all the tall grasses and think we're just letting it go, that we'll be letting the trees grow up; they don't realize how native grasses will benefit wildlife and basic diversity in the Cove."

For more information, contact Jenny Beeler, Great Smoky Mountains National Park, 107 Park Headquarters Road, Gatlinburg, TN 37738, 865-430-4748.

To volunteer to collect seeds, plant native-plant plugs, or pull exotic plants, contact NPS Volunteer Coordinator Babette Collavo at 865-436-1265.

Microstegium Vimineum:

The Dark Invader

• A tough, wiry grass typically found in moist, wooded areas is currently ranked as one of the biggest threats to Great Smoky Mountains National Park. The plant, called Microstegium vimineum but commonly known as Japanese stilt grass, is ranked in the top 20 biggest threats for Tennessee as a whole, according to Jake Weltzin, an assistant professor in the University of Tennessee Department of Ecology and Evolutionary Biology. In addition, Microstegium is on the federal invasive-plants list, Weltzin says.

• Although Japanese stilt grass has spread widely throughout the entire eastern United States, nothing is known about its potential impacts on natural systems. Likewise, because Microstegium leaves few clues to the environmental variables that influence where it's most likely to establish itself, effective control measures have been difficult to determine.

• Through greenhouse and field experiments, Weltzin and Patrice Cole, a UT doctoral student in Ecology and Evolutionary Biology, have found that light seems to be the most important environmental factor. In fact, Microstegium can tolerate low light conditions that would destroy many other plants, yet the grass grows bigger and produces more seeds when given more light in greenhouse experiments, the researchers say.

• An additional factor complicating the search for effective control measures is that "you very often see a striking boundary or edge to the patches," Cole says. "One spot will support a big patch, and three feet away, there won't be any Microstegium at all. Why? Is it a patch that's just beginning to spread? Is it actually a patch that's shrinking? Or is it a very stable edge being maintained by one or more environmental factors such as light, water, soil texture, or nitrogen?" Cole asks.

• The biggest uncertainty however, is whether Microstegium is crowding out natives. Actually, says Cole, "It's pretty hard to imagine that it's not having some sort of impact because there's just so much of it."

Kris Christen