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Where the bison roam …

By Staff | Apr 29, 2011

With more than 8,600 acres, including some native prairie and savannah remnants, the Neal Smith National Wildlife Rufuge near Prairie City offers plenty of room for the 72 bison and 16 elk that currently live at the refuge.

PRAIRIE CITY – In the landmark 1949 book “A Sand County Almanac,” Aldo Leopold wrote, “What a thousand acres of Silphium (compass plant) looked like when they tickled the bellies of the buffalo is a question never again to be answered, and perhaps not even asked.”

Leopold would be delighted to know that not only are Iowa scientists asking these questions, but they are using the Neal Smith National Wildlife Refuge near Prairie City to find answers that can help guide modern grassland management.

“The prairie is a very complex ecosystem, and it’s the reason why we have good farmland in Iowa,” said Pauline Drobney, a U.S. Fish and Wildlife Service biologist, who notes that the wildlife refuge includes former farm fields, pastures and Conservation Reserve Program acres, along with some native prairie.

“Since 99.9 percent of the state’s native prairies are gone, we need to understand the natural processes that occurred in these areas so we can manage reconstructed prairies and grasslands to the best of our abilities.”

An 8,600-acre prairie and savanna ecosystem makes up the wildlife refuge, which was created by an act of Congress in 1990 to re-create the native plant and animal communities that existed in central Iowa prior to Euro-American settlement in the mid 1800s.

Seeds of native grasses and plants can become trapped in bisons’ thick, rough coats. Pete Eyheralde, an ISU graduate student, uses this example at the Neal Smith National Wildlife Rufuge's visitor center to explain how seeds can be dispersed when a bison sheds its coat in the spring and summer.

Today, the refuge is home to 72 bison, which were a key species of the prairie.

They are of particular interest to W. Sue Fairbanks, an associate professor of natural resource ecology and management at Iowa State University, and her students, including Pete Eyheralde.

“Bison were important ecological players when it comes to seed dispersal, and we want to understand what role they can play in a functional prairie reconstruction,” said Eyheralde, an ISU graduate student in Natural Resource Ecology and Management.

“Can we heal the prairie without the bison, or do they play a key role?”

Studying a hairy issue

Emily Artz, a junior at Iowa State University majoring in animal ecology, studies the various seeds of native prairie grasses, like these at the Neal Smith National Wildlife Refuge near Prairie City.

Animals’ roles in seed dispersal have attracted the attention of scientists around the globe in recent years, said Fairbanks, who noted that a better understanding of the process is important not only in Iowa, where prairie reconstructions are taking place, but in areas of South America, where fragmented rain forests are being reconstructed.

“Seeds generally don’t go too far by themselves,” said Fairbanks, who noted that most seeds aren’t dispersed more than 10 meters (approximately 11 yards), from the parent plant.

“Our research may uncover novel ways to get plant species established in prairie reconstructions.”

Bison have become a focus of the ISU research, since they were nomadic animals that could move great distances.

More than 90 percent of their diet is comprised of grasses, which leads to one form of seed dispersal through the animals’ digestive systems.

In addition, bison’s distinctive hair offers another effective method for transporting seeds across the prairie.

“A bison’s coat is very thick and curly and is quite a bit different from the hair on cattle,” said Eyheralde, who used to raise cattle and bison on his farm in Monroe County.

“As the bison graze, they brush against prairie grasses and plants, which dislodges seeds from the plants.

In the area where the bison’s fur meets the skin, it can be almost solidly packed with seeds.”

Emily Artz, a junior at Iowa State University who is majoring in animal ecology, has collected the seeds that are trapped in the clumps of hair that the bison shed in the spring and summer.

She has found seeds for Indian grass and big bluestem, while her fellow researchers have also found the seeds of forbs like asters, goldenrod and sunflowers.

Prairie reconstructions

The ISU researchers are not taking random samples as they study the bison and analyze viable seeds. They use global positioning system technology to help pinpoint transects that are evenly distributed so they can track seed dispersal patterns in the wildlife refuge.

“We want to get a better idea of what is already growing in these areas at certain times of the year and be able to compare these plants to the seeds we find,” Artz said.

Eyheralde is integrating this field data into a computer model that will allow users to access seed dispersal information for land areas of various sizes.

The scientists’ findings may break new ground in effective grassland management, Fairbanks said, because very little research has been conducted on bison and seed dispersal patterns in reconstructed prairies.

“We don’t want just a nice-looking prairie – we want a functional prairie reconstruction.”

You can contact Darcy Dougherty Maulsby by e-mail at yettergirl@yahoo.com.

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