Embattled Curtis Prairie a test bed for new restoration techniques

To the ordinary eye, the world’s oldest restored tall-grass prairie is an idyllic postcard picture. Long, slender grasses sway in the breeze, and playful blackbirds swoop everywhere.

But for restoration ecologist Joy Zedler, the poetry of the scene masks an unavoidable truth: The present day Curtis Prairie, a star attraction of the University of Wisconsin–Madison Arboretum, is hardly the pristine place it once was.

Storm waters from nearby development sites have for years coursed through the land, carrying in outside soils and unwanted nutrients. Invasive reed canary grass has blanketed the prairie area as a result, steadily snuffing out native plants as it spreads.

Following in the footsteps of the visionary conservationist Aldo Leopold, UW–Madison scientists have for more than six decades used Curtis Prairie as a testing site for a variety of restoration techniques. But few of them had to contend with the modern-day ecological threats that Zedler, who directs restoration research at the Arboretum, is facing now.

To fight new problems, she has spent several years crafting new solutions. Starting this year at Curtis Prairie, and with $120,000 from the Environmental Protection Agency, Zedler and other researchers are finally putting those solutions to the test. “We need a paradigm shift,” Zedler says.

Her preferred approach – what she calls “adaptive restoration” – rests on recognizing that you can’t fix a piece of land unless you figure out how it works. Rigorous, multidisciplinary experiments can generate such data and inform restoration decisions, Zedler says. Ecologists can then test a variety of restoration strategies in small patches of the restoration site, moving to larger areas with tactics that work best.

In the past, “people tried different things to see what works, but they often tested one idea on an entire site,” says Mike Healy, a land resources graduate student working with Zedler. “[With adaptive restoration] you can keep the costs and effort low, and if a certain treatment works, you can apply it to a larger portion of site.”

“We’re discovering that successful restoration is more than putting our desired plants in the landscape,” agrees soil scientist Kevin McSweeney, the Arboretum’s acting director. “We need fundamental scientific insight into physiological and biological processes if we want a desired condition, and that means an integrated understanding of hydrology, the role of soil, microbes and plants.”

Beginning at the northern edges of a big patch of reed canary grass within Curtis Prairie, Zedler and her students are exploring this summer several restoration treatments that might squelch the hardy invasive and give native plants, such as sedges and the Ohio spiderwort, a fighting chance.

The scientists have set aside 48 small plots – measuring 2 by 4 meters – in each of which Healy is applying eight different treatment cocktails. In one plot, for instance, he’ll plant native seeds and add a grass-killing herbicide, while in another he might apply several doses of herbicide but no seeds.

“Adaptive restoration attempts to demonstrate many restoration approaches at once so that we learn by doing,” says Zedler, “no need to put off restoration until the experiments are complete.”

Still, it took several years of experimentation just to get to this moment, with every discovery opening yet another floodgate of questions. “It takes time to identify all the things you don’t know,” says Zedler. “And there is no cookbook approach to restoration.”

In the case of reed canary grass, for instance, researchers needed to understand exactly what makes it so hard to beat. At the present time, the invader dominates over 40,000 hectares of Wisconsin lands, according the Wisconsin Department of Natural Resources.

Early on, Roberto Lindig-Cisneros, a doctoral student of Zedler’s, discovered that reed canary grass loves light. The seedlings of the wily species can spring up wherever the sun pokes through the prairie’s dense grassy cover.

Another telling experiment by graduate student Suzanne Kercher, explored how “disturbances” such as storm-water flooding affect the growth of reed canary grasses. She set up 150 barrel-size tubs outdoors, planting each with at least 20 native plants to simulate a natural wet prairie. After two years, she introduced reed canary grass seedlings into the tubs, charting their growth in the presence of additional nutrients, sediments and floods-all byproducts of storm water. The result was shocking: storm water nutrients and flooding can nearly double the rate at which the invasive grass grows. And with time, it choked out more than six native plants.

“Of all the invasives in Wisconsin wetlands, reed canary grass is the worst,” says Zedler.

As restoration kicks off in Curtis Prairie, other researchers will continue myriad explorations of the prairie’s many dimensions. Post-doctoral weed ecologist Lynn Sosnoskie, for instance, is studying prairie soil samples to learn what types of seeds are buried underground. “If the seed bank is dominated by desirable species, it may not be necessary to artificially introduce certain native plants,” as those plants can come up on their own, she says.

Meanwhile, Cynthia Stiles, a UW–Madison assistant professor of soil science, is beginning to explore the soil itself to understand whether buried sediments carried in by storm water – layered for years on the prairie’s own soil – can support the reemergence of native plants. If not, all that soil will have to be exhumed. “I was amazed to find that there is no real information on the characteristics of buried soil,” says Stiles. “No one has looked at it in the context of restoration ecology.”

Building slightly raised earthy mounds that mimic natural soil clumps, known as tussocks, might also play a big role in supporting native plants. At least two Zedler students want to explore the merits of the potential strategy.

Adaptive restoration makes a lot of intellectual sense, but it’s unclear how readily the idea will take hold outside research settings, where land owners, land managers and engineers typically make most restoration decisions. The primary bottleneck, of course, is money.

“[Land managers] don’t always have the time, money, manpower, and other resources needed to study a system, experiment on it, and then implement a management strategy,” says Sosnoskie, who worked for several years at arboretums in Pennsylvania. “Yet we need the data that many are unable to collect. By developing, implementing, and reporting experimental methods, Joy is providing an important service to land managers and theoretical ecologists.”

The Arboretum’s high public visibility is also giving restoration ecology students a taste of working in the real world, McSweeney adds. “This facility is open to the public in a way that no other university research facility is, so the work here does broaden into the social and economic issues of what we can or cannot do,” he says.

Zedler has also heard all the arguments before. “If we don’t do these experiments we’ll end up wasting more of the public’s money. There shouldn’t be a stigma attached to the word ‘experiment’,” she says. Zedler doesn’t expect all the native species to bounce back for at least another decade, but if all goes well at Curtis Prairie, she is hoping it will reflect the merit of her approach, most notably at the Society for Restoration Ecology International Conference, slated to take place in Madison in the year 2009.

And, most importantly, if the Curtis Prairie restoration project produces useful advice for others, says Stiles, “we will have created a successful model that can one day have broader implications for regional and even international work.”

• Paroma Basu, (608) 262-9772, basu1@wisc.edu