Research Aiding Saline Wetlands Management

by Jason Grotelueschen

(Grotelueschen is a student and editorial assistant for NU's Conservation and Survey Division in Lincoln).

A rare and vanishing type of plant and animal habitat in southeast Nebraska is better understood due to a University of Nebraska researcher's findings.

Saline wetlands, characterized by salt-tolerant plants that grow in salty soils and water, have been reduced to about 10 percent of their original coverage in Nebraska. Only 1,200 acres of the unique wetlands remain in the state.

Groundwater geologist Jerry Ayers of NU's Conservation and Survey Division in Lincoln is studying the Rock Creek watershed in north Lancaster and south Saunders Counties with an eye to preserving and better understanding these wetlands.

"The number of saline wetlands has decreased substantially, partly because we've never known much about them," Ayers said. "You can't manage anything if you don't know how it works."

These wetlands, sometimes called salt marshes, are home to many plant and animal species specially adapted to them, said Randy Stutheit of the Nebraska Game and Parks Commission. Some of these are saltwort and sea blite plants and the rare Salt Creek tiger beetle, that makes its home only in the saline environs of the Salt Creek watershed.

But there are two types of saline wetlands in Nebraska.

Eastern salines are in the southeast part of the state and their saltiness is thought to come primarily from sodium salts that were probably deposited by an ancient sea that once covered the state.

Western alkalines are found in western Nebraska. Their salinity is thought to come from magnesium, sodium and calcium salt deposits, said Stutheit.

Part of Ayers' research has focused on discovering the source of the salinity in wetlands along Rock Creek in the Jack Sinn Wildlife Management Area near Ceresco.

The answer most likely lies below the surface of the wetland.

Below the surface of the Rock Creek site is a top layer of silt 35 feet deep, a sand and gravel layer 10-40 feet deep and an 82-120 foot deep layer comprised of silt and clay over coarse sand and fine gravel. This later layer is what geologists refer to as the "Dakota group."

- About half to two-thirds of America's wild ducks
hatch in the prairie pothole wetlands of North Dakota,
South Dakota, Minnesota and Iowa.

In examining apparent movement of the underlying groundwater in this Dakota group, Ayers has found water in a layer of sand that is moving rapidly toward the surface.

This "Dakota sand" is probably the main source of the wetland's salinity, he said.

Saline wetlands are also known to exist in Kansas, North Dakota, South Dakota, Oklahoma, Wisconsin and other states, Ayers said.

"They are rapidly disappearing due to changes in land use," he said. Examples of these changes are channeling streams, changing watershed management and suburban encroachment.

In addition to his groundwater geology research, plant and soil surveys are also being conducted at the Rock Creek site.

The Rock Creek wetland site was acquired by The Nature Conservancy, a nonprofit group that turned control of the site over to the Nebraska Game and Parks Commission.

The commission then asked for help from the USDA's Natural Resources Conservation Service in managing and researching the wetland. They turned to Ayers and Anne Matherne, a former NU surface water researcher, to help find out how the wetland formed.