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Research Shows Wind Is A Defining Characteristic Of The Great Plains Grasslands

A mixture of green grass and taller brown grass make up a rolling landscape under a blue sky with a few clouds.
Rick Bohn
The Great Plains Grasslands are closely tied to fire regimes.

Scientists still aren't sure what maintains the Great Plains Grasslands and keeps them separate from forests. A very common hypothesis is that there are climatic differences between the areas where each type of ecosystem forms.

"You know, trees can't grow in the Great Plains because it's too dry or something like that," explained Brice Hanberry, a research ecologist with the U.S. Forest Service.

But the boundaries between the two ecosystems have been slowly disintegrating since around 1850, which caused Hanberry to wonder if something else was responsible for keeping them separate. So, she gathered a variety of historical data related to climate variables like precipitation, evaporation, and vapor pressure. But she was also interested in the role fire played.

"We have great climate data, but we don't have much fire data or any way to look at historical fire regimes. But we do have a proxy for that and that is wind speed because wind carries fires," said Hanberry.

Hanberry used a computer model to determine which variables had the most influence on boundaries, but the most influential variable wasn't a great surprise to her.

"Just looking at the images of wind speed, it really to me wasn't even necessary to model because the wind speeds of about four to four and a half meters per second really just delineated the Great Plains," said Hanberry, "Whereas, if you tried to take the climate variables and delineate the Great Plains, you'd have to kind of take this, take this little section here, and then maybe take a little bit from these variables here, and then something from here. Eventually, you might be able to kind of hodgepodge a bunch of variables together to make something, but each variable on its own could not explain or delineate that Great Plains region."

The reason wind speed, and thus, fire, is important for the Great Plains, according to Hanberry, is because fire generally prevents trees from establishing.

"There are only a couple mechanisms that can reduce vegetation biomass or tree biomass on a small [scale] like understory biomass, and one of them is fire. Low severity surface fire removes that understory or small diameter of biomass. The other mechanism for that is herbivory," said Hanberry.

But, she argues, the huge historic megafauna that used to be found in North America have since gone extinct, leaving us with less efficient animals like deer, elk, and bison to try to control dry grass and small understory vegetation. This adds another piece of evidence in the argument for prescribed burns, said Hanberry.

"If you prescribed burns, it removes the small diameter trees big before they get big, and that's the fuel," she said. "And also, if you can remove those small diameter trees, and then instead look at herbaceous growth, and how tall those grasses get - not very tall, so the height of those fires is pretty low. They can't spread up and create severe fires."

Hanberry plans to continue research in this area to pinpoint best management practices for encroaching trees and preventing severe wildfires.

Ivy started as a science news intern in the summer of 2019 and has been hooked on broadcast ever since. Her internship was supported by the Wyoming EPSCoR Summer Science Journalism Internship program. In the spring of 2020, she virtually graduated from the University of Wyoming with a B.S. in biology with minors in journalism and business. When she’s not writing for WPR, she enjoys baking, reading, playing with her dog, and caring for her many plants.
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