Spring 2008

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Long-term interdisciplinary buffer project improves water quality, explores biomass potential

by Laura Miller

High above the central Iowa landscape, even untrained observers can spot the area. Deep green strips hug the curves of a creek, forming irregular shapes that fade into the tidy patchwork of corn and soybean fields.

When Dick Schultz ('65 forestry, M.S. '68, Ph.D. '70 forest biology) flies over this area, he sees a wildlife corridor, home to a growing number of pheasants, deer and quail for hunting and many more species of song birds that can provide insect controls for neighboring crops as well as excitement for bird enthusiasts. He envisions a healthy stream corridor of diverse perennial plants that provides ecosystem services to both the aquatic and terrestrial communities that lie along it.

Producers might imagine potential future income generated from the harvest of biomass for production of renewable fuel. And environmentalists might foresee the crucial role this area could play in sequestering carbon and offsetting greenhouse gases.

These are just some of the many possibilities arising from the Bear Creek demonstration project, the crown jewel in pioneering research begun by Iowa State's Leopold Center for Sustainable Agriculture to design and manage streamside buffers to improve the state's water quality. In 1990 when the first buffer system was planted along Bear Creek on Ron Risdal's Story County farm, it was one of the first such restorations in the United States.

"The Bear Creek buffer project was unique because most of Iowa's native vegetation—tallgrass prairie and wetlands—have been removed," says Schultz, a professor in natural resource ecology and management. He leads the Agroecology Issue Team that coordinates Bear Creek research from across the college including agricultural and biosystems engineering; agronomy; animal science; ecology, evolutionary and organismal biology; economics; geological and atmospheric sciences; and sociology.

"Riparian research projects in other parts of the country had native plantings that had been in place for a long time," Schultz recalls. "But here was an opportunity to see how we could design native vegetation corridors that could provide water quality and wildlife habitat benefits in a landscape dominated by agriculture."

Today thousands of miles of streams throughout the United States are protected by buffers, and farmers can participate in government cost-share programs to use this conservation practice.

The Bear Creek project includes 10 continuous miles of buffers along both sides of the stream. The buffer design consists of rows of trees and shrubs, and a wide grass filter of switchgrass or other native grasses and forbs to trap nutrients and sediment in the surface water runoff from adjacent crop fields. The system also includes constructed wetlands, examples of streambank bioengineering to stabilize eroding banks, and in-stream structures to improve channel conditions.

Much has been learned at Bear Creek and the project has placed Iowa in the national spotlight and sparked international interest.

But Schultz says the fascinating part is how research continues to evolve, such as a current project on biomass production. When the Bear Creek project began, analyses showed that markets for biomass just weren’t there. Nineteen years later, the silver maple, green ash, willow and poplar planted on the buffer strips have matured and offer another avenue for research on the economic viability of generating income from biomass.

Other projects seek to quantify the potential of buffers for carbon sequestration and measure the amount of nitrous oxide, a greenhouse gas, contributed by the buffer as compared to crop fields. Another recent project tackles streambank erosion, a major source of in-stream sediment.

The value of buffers for wildlife habitat has not been overlooked by the nine landowners whose land is part of the Bear Creek project. They use the area for hunting deer and pheasant and one landowner has released quail in hopes of establishing a population. Aquatic life also has flourished in the protected streams.

A song bird survey in the Bear Creek Watershed showed 43 species in the riparian forest buffer after 10 years of growth, compared to nine in the narrow grass and weed strips typically left along unbuffered streams. Researchers are conducting a 2008 survey to update the information.

The Bear Creek project also has been a valuable teaching tool. At least seven Iowa State classes regularly visit the area, and more than 30 graduate students have conducted their research projects at Bear Creek. Visitors have come from more than 30 countries, including four visiting professors from South Korea and Venezuela.

Iowa ranks third among all states in use of riparian buffers with more than 64,000 acres. This accounts for eight percent of all the acres currently classified by the USDA as protecting streams.

"We think the high use of buffers in Iowa is partially due to work at Bear Creek," Schultz says. "It's so visible and concrete, a place you can visit. We've been able to keep this issue on the front burner for a long time, and I hope for a long time to come."

Lessons Learned from Bear Creek

Buffers can...

• Cut sediment in surface runoff as much as 90 percent
• Cut nitrogen and phosphorus in runoff by up to 80 percent
• Entice and support five times as many bird species as row-cropped or heavily grazed land
• Allow water to infiltrate five times faster than row-cropped or heavily grazed land
• Remove up to 90 percent of groundwater nitrate under the right geological settings
• Cut streambank erosion by as much as 80 percent from row-cropped or heavily grazed land
• Reach maximum efficiency for sediment removal in as little as five years
• Reach maximum nutrient removal efficiency in 10 to 15 years
• Increase soil organic carbon up to 66 percent
• Produce less nitrous oxide, a greenhouse gas, than adjacent crop fields
• Tree, shrub and grass communities are needed to provide the maximum ecosystem services
• Be most effective at upper reaches of a watershed

Schultz Named Friend of Conservation

Dick Schultz, professor of natural resource ecology and management, was named a 2007 Friend of Conservation by the Iowa Chapter of the Soil and Water Conservation Society. Schultz received the award at the chapter’s annual conference in August in honor of his contributions and achievements in soil and water conservation.

Online Extra

Find a link to a virtual tour of the demonstration sites in the Bear Creek project at this site. The site has a photo gallery, extension publications, research abstracts and links to related information and resources.