UNL Study: Nebraska's Sandhills Dunes May Be More Stable Than Thought

UNL Study: Nebraska's Sandhills Dunes May Be More Stable Than Thought

May 4, 2007

Two years after removing the vegetation from several Sandhills dunes, University of Nebraska-Lincoln researchers are just now beginning to see signs of erosion. That indicates the dunes may be a lot more stable than researchers originally thought.

"In some ways that's surprisingly long, if you think of the Sandhills as a very fragile ecosystem," said Dave Wedin, grassland ecologist with the School of Natural Resources who heads a team of UNL researchers studying the history of grassland destabilization and how long- and short-term climate changes might affect their stability.

"We hurt the grass big time, and the dunes still had enough integrity, mainly because of the roots and the soils, to hold on for a couple years" before beginning to show signs of erosion, he said.

"We wanted to carefully measure and document some pieces of Sandhills landscape, and then kill the vegetation. Once the living plants are out of the story, we could see how long the landscape holds on," he said. "How long do the dunes stay intact? How long before sand starts moving? What are the factors controlling stability — whether sand stays in place or starts to move?"

Wedin's experiments are being conducted on about 30 acres of the former Barta Brothers Ranch near Rose, a 6,000-acre Sandhills ranch donated to UNL in 1996 by brothers Jim and Clifford Barta. Researchers began their research by creating 10 circular plots, each 120 meters in diameter, or somewhat larger than a football field, and then using herbicide to kill all the vegetation on several of them. The plots continued to be treated with herbicide and kept free of vegetation for one to two years.

Researchers monitored such information as the coverage of live and dead plants, root mass, organic matter in the soil, and sand movement to determine stability of the plots.

The results, Wedin said, indicate the Sandhills may be more stable than previously believed. Vegetation was allowed to return to one set of plots initially treated with herbicide after one year. These plots showed a large amount of weed growth, but no soil erosion.

While the research made significant progress in studying the balance between soil, vegetation and water in the Sandhills, Wedin said additional study is needed to determine what happens when sand dunes begin to erode, or become mobile. He also said future studies on the roles grassland grasses and shrubs play on the fields and dunes is needed since most comparable dune systems in other regions of the world are covered with shrubs and trees, which are rare in the Sandhills.

The ongoing research began three years ago as part of the SandHills Biocomplexity Project, a $1.8 million National Science Foundation-funded project.

"The project is about sand, grass, and water, their interactions, and the stability of the Nebraska Sandhills over the last few thousand years," Wedin said. Fifteen co-researchers from several scientific disciplines at UNL, such as geology, hydrology and ecology, have studied such issues as drought, dune movement, groundwater recharge and climate change.

Wedin's research is designed to study what would happen to the Sandhills if something such as climate change caused a loss of vegetation on the sand dunes, a primary focus of the biocomplexity project's grassland destabilization experiment that Wedin heads.By focusing closely on dune destabilization, this research also is shedding new light on Sandhills history, as told by ancient soils, sand ripples and animal burrows buried in the dunes themselves, Wedin said.

Another goal of the biocomplexity project is to lay groundwork and infrastructure for future UNL studies in the Sandhills.

"I think we've done a very good job of that," he said. "Was it worth killing 17 acres of UNL's Sandhills property to understand how grasslands keep this vast dunefield under control in the face of changing climate? As project leader, it's my responsibility to see that those pieces of native Sandhills prairie did not die in vain and how critical it is that this experiment provide new insight into the stability of this valuable landscape for both scientists and local stakeholders."

Part of the research's value is in the learning opportunity it has provided to researchers, graduate students, high school science teachers and student interns that have worked on the project since 2004, he added.The Sandhills are the largest sand dune area in the Western Hemisphere and the stability of the area not only affects cattle ranchers and farmers, but also recharge of the High Plains Aquifer, a vast groundwater resource reaching into eight High Plains states, including Nebraska, Colorado, Kansas and Wyoming. Today the Sandhills are nearly completely stabilized by native grasses, but Wedin said previous research shows a history of destabilization. The biocomplexity project has helped show how active this landscape has been in the last 1,000 years.

The biocomplexity project is being conducted in cooperation with UNL's Institute of Agriculture and Natural Resources, Agricultural Research Division and College of Arts and Sciences. The Institute of Agriculture and Natural Resources includes UNL Extension, the Agricultural Research Division and the College of Agricultural Sciences and Natural Resources.

A 2007 study by an independent organization found IANR annually returns at least $15 in benefits to Nebraskans for every dollar of state support, making it a primary engine for economic and social sustainability (See more about what IANR is going for Nebraska at http://atworkfornebraska.unl.edu).

Steven W. Ress
Communications Coordinator
UNL Water Center

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