—by Marilyn Davis

Big bluestem, switchgrass, purple coneflower, rattlesnake master. The names may be familiar to us from books, nature preserves, and even home gardens. But in their native habitat, these and dozens of other prairie plants gave way to farm fields long ago.

Only remnants are left of the expansive grasslands that amazed early pioneers. Illinois once boasted a quarter of North America's tallgrass prairie. Today, for every thousand acres that grew here before European settlement, only one remains—most often in the form of small strips bordering railroads. And across the Great Plains, less than 5 percent of native prairie survives.

Now, many groups are trying to restore prairie on worn-out agricultural land. "The interest from the government's perspective is conserving soil and water resources. Then there are a lot of private organizations, like The Nature Conservancy, interested in restoring and protecting biodiversity. And it begins with the plants," says Sara Baer, an SIUC biologist with expertise in prairie plants and soils.

Baer and David Gibson, a fellow SIUC professor of plant biology, study prairie restoration for its own sake and for what it can tell them about ecological principles: how communities of plants are assembled; what factors affect the balance of species, filtering out some while enabling others to dominate; and how diversity affects ecosystem functioning.

Most prairie restoration sites rely on cultivars: seed from prairie grasses that the U.S. Department of Agriculture collected and then bred over the years. The USDA selected for certain traits, such as robust growth, that may or may not be what's optimal for restoring a diverse prairie. And the breeding process itself inevitably changes the plants from their native counterparts, which also may affect restoration efforts.

With a five-year, $445,000 National Science Foundation grant, Baer and Gibson are carrying out experimental restorations at three sites. Multiple plots at each site will allow them to compare the effects of planting cultivars and wild seeds for three common prairie grasses—big bluestem, little bluestem, and Indian grass—under the same soil and climate conditions.

Several years ago, Baer (then doing doctoral research at Kansas State University) and Gibson were separately uncovering evidence that cultivars varied in potentially important ways from native-grown grasses. In Southern Illinois, one of Gibson's students was finding genetic differences between cultivars and wild seed. Another student, studying cultivar and non-cultivar prairie grasses on reclaimed mine land, was finding differences in photosynthesis rates. And Baer, studying sites restored with cultivars, was finding "much higher productivity and higher biomass than we measured in native prairie."

That's not necessarily a good thing. Prairie plants are typically slow to get established. Grasses that grow faster and taller than normal may outcompete non-grass species, such as wildflowers, important for a diverse, healthy, sustainable prairie.

"It's easy to restore productivity," Baer says, "but restoring diversity is very difficult."

The number of species at a site, called species richness, is half of the biodiversity equation. The other half is "evenness": the relative abundance of those species.

"You need them both," Gibson says. "An agricultural field might have a lot of different sorts of weeds, but it's still low diversity because it's mostly corn or wheat." Native prairies are very diverse, and provide habitat for a wide range of creatures, because many plant species are abundant.

Small-scale grassroots prairie restorations by local volunteers have given rise to rules of thumb about best practices, such as using wild seed collected within so many miles of the site to be restored. But little research has explored their validity.

"From a practical standpoint, we're hoping to provide some scientific basis for making better decisions about restoration practices," Gibson says. "From a theoretical standpoint we hope to learn more about how plant communities are assembled. What we find with tallgrass prairie may have relevance for other ecosystems."

Baer, Gibson, and a cadre of students are restoring sites near Carbondale, near Belleville, Ill., and at the Konza Prairie Long-Term Ecological Research site in Kansas. At each of the sites, they've planted plots with cultivated or wild seeds for the three grasses they're studying, along with different pools of wildflower seeds.

Some years previously, Gibson, doctoral student Danny Gustafson, and SIUC plant biologist Dan Nickrent did a study of restored prairie sites in Illinois. That research supported the idea that using locally collected grass seeds, rather than seeds from other regions, is beneficial. "Where the seeds came from made a huge difference in how they grew," Gibson says.

But using native seed collected locally may not be a realistic option for many restorations, Baer says. "It took us months to collect a small amount of local native seeds, with low germination rates. Maybe the diversity of the mixture you put in is more important than the grass sources. For example, maybe if you put a cultivar in at a very low seeding rate [to compensate for its high productivity], you could establish a diverse prairie."

To test that idea, plots at Konza and Belleville will incorporate different proportions of cultivated seed in the total mix—from 4 percent to 97 percent—with the rest made up of equal numbers of non-grass species.

As the plants grow, the team will measure things like species cover at different times of the summer, soil nitrogen availability, and so forth. Master's student Allison Lambert will compare photosynthesis rates of the cultivars and non-cultivars. Master's student Lewis Reed will selectively remove grass species from various plots to test the theory that cultivars choke out other species because of their high growth rate.

Another master's student, Ryan Klopf, is studying root biomass. And Ryan Campbell, who collected most of the wild seeds for the project as an undergraduate, has stayed on as a master's student to study root colonization by fungi.

"When you go from prairie to cropland, you go from a fungal-dominated [soil] community to one dominated by bacteria," Baer explains. "Fungi are critical in restoring the aggregate structure of soil—a key measure of soil quality—that's lost in tilling."

Undergraduates in plant biology, zoology, and forestry also are an integral part of this large project, which runs the gamut from roots and leaves to the overall ecosystem. The team is studying the growth of individual plants and how that affects species biodiversity, but they're also looking at how biodiversity affects ecosystem-scale processes such as nutrient use and soil enrichment.

After just one growing season so far, Gibson says, "It appears already that cultivars are coming in quicker—establishing more and bigger plants. They've got a head start. The establishment of native seeds is not great so far."

Wild seeds may be getting shut out, he says, or they may simply take more than one year to germinate. Baer speculates that wild seeds "may be allocating more energy belowground at first. Cultivars, like crops, may allocate more aboveground." That would explain why they overtop other species.

What goes on in the soil, however, is more important in the long run to creating and sustaining a diverse prairie.

"In a prairie there's more biomass belowground than aboveground," Gibson says. "There's lots of activity belowground; it just hasn't been studied properly." Restoring a sustainable prairie depends on how well these perennial plants take root and rebuild soil organic matter and nutrients.

Baer holds a three-year, $286,000 fellowship from the Andrew W. Mellon Foundation—only one is awarded per year, to a promising junior researcher—to study long-term recovery of carbon, nitrogen, and microbial pools in the soil of restored prairie sites.

In four different areas, two in western Nebraska and two in northwestern Illinois, she's identified a number of small restored prairie sites ranging from two to 18 years old, along with patches of native prairie. These so-called "chronosequences" provide a timeline—a way to get a handle on long-term changes in soil quality. Baer will be able to compare sites across regions with climate differences (Illinois gets much more rain) and across soil types. Postdoctoral fellow Clinton Meyer is working with her on a total of 80 sites.

"We're hoping to expand this research to South Africa, where another prairie chronosequence has been identified," Baer says. "They have some native grassland left and have done some restorations, so we can look for global generalities."

Prairies are unquestionably good for the planet. They enrich the soil. They sustain a rich fauna. They build up and store large amounts of carbon—and the more carbon sequestered in the soil, the less carbon dioxide in the atmosphere to contribute to global warming.

But another reason for restoring prairies is, simply, to restore part of our heritage—to see for ourselves the same beauty that our forebears did.