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Harder Downpours Likely to Spur Woody Plant Growth say USU Scientists

Thursday, Jun. 20, 2013

USU faculty member Andrew Kulmatiski and group in South Africa

In South Africa's Kruger National Park, USU scientist Andrew Kulmatiski, right, and park employees construct a rainout shelter. With USU ecologist Karen Beard, Kulmatiski published research findings in 'Nature Climate Change.’

an African elephant

Land managers at Kruger National Park, where Kulmatiski and Beard conducted research, are concerned about the effects of climate change on the availability of forage for elephants and other large mammals that inhabit the vast game reserve.

Current climate change models suggest rain events will become more intense over much of the globe and that will affect plants as well as people, say Utah State University scientists.

“We don’t really know how fewer, yet larger, precipitation events will affect plant growth,” says Andrew Kulmatiski, assistant research professor in USU’s Ecology Center and Department of Plants, Soils and Cliimate. “It’s quite possible increasing storm intensity could convert vast grasslands to shrublands. This is something ranchers definitely want to know.”

Kulmatiski and Ecology Center colleague Karen Beard, associate professor in USU’s Department of Wildland Resources, published findings from research that tries to address this issue in May 26, 2013, online edition of Nature Climate Change. Their research, funded by the Andrew Mellon Foundation, was conducted in South Africa’s Kruger National Park.

“Land managers at Kruger are keen to predict how climate change may affect forage growth for zebras and browse growth for elephants,” Kulmatiski says.

To investigate the effects of increased precipitation intensity, Kulmatiski and Beard constructed six large rainout shelters, about 26 by 26-feet each, in the sub-tropical savannah ecosystem of the vast game reserve.

“Rainout shelters are designed to protect a plot of land from precipitation, allowing researchers control the amount of precipitation received and observe the effects,” Beard says. “We used the shelters to create large, intense precipitation events and measured the results. We compared these results with control plots that received no treatment.”

The researchers found big storms ‘pushed’ water deeper into the soil. Woody plants such as shrubs and trees were better able to grow their roots down far enough to capture the deeper soil water. This resulted in increased woody plant growth and decreased grass growth.

During the past 50 years, woody plants have invaded similar grasslands, causing researchers to surmise such “shrub encroachment” was the result of increases in wildfire, grazing and atmospheric carbon dioxide concentrations.

“Our research suggests increasing precipitation intensity may also be causing this change,” Beard says.

In the paper, she and Kulmatiski note if climate change models are correct, shrublands will likely continue to invade grasslands around the world.

“This is likely to decrease forage value and increase fire intensity,” Kulmatiski says. “But it may also increase carbon sequestration and water recharge to aquifers.”

Related links:

Contact: Andrew Kulmatiski, 435-770-9646,

Contact: Karen Beard, 435-797-8220,

Writer: Mary-Ann Muffoletto, 435-797-3517,

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