Curious Iowa: How do prairie burns work?

Prescribed burns have been happening for thousands of years.

From prairies to woodlands, prescribed burns have been a conservation staple for managing habitats.

But how are they conducted? And how do they benefit Iowa’s ecosystems?

That’s what one Iowan asked The Gazette’s Curious Iowa, a series that answers readers’ questions about our state, its people and the culture.

We spoke to experts, conservationists and attended a prescribed prairie burn ourselves to learn more about this long-standing practice.

What’s the history of prairie burns?

Prescribed burns date back far before European colonization, said Mitch Ahrendsen, natural resources manager for Linn County Conservation.

Ahrendsen said Indigenous peoples used prescribed burns to manage natural landscapes in the area that would become the state of Iowa years later.

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“Through trial and error, they saw the benefit that prescribed burns left behind,” Ahrendsen said.

Years ago, Iowa’s landscape was about 80 to 85 percent tall grass prairie. Now, Ahrendsen said, tall grass prairie makes up less than 1 percent.

“We’ve plowed about 99.99 percent of it up,” he said. “It’s significantly limited now.”

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What happens during a prescribed burn?

Rich and Marion Patterson of Cedar Rapids burned sections of the prairie in their front and back yards in December to help stimulate new plant growth in the spring and to weed out invasive species.

The Pattersons started their prairie burn by igniting a few of the prairie grasses with a lighter and bringing more prairie stalks to the flame with a rake to fuel the fire.

They continued raking more of the prairie grass toward the flame, guiding the fire around their prairie to let the flame burn the plants.

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Burns often take place in the spring or fall, but they can happen even when snow is on the ground, Rich Patterson said.

He said it’s best to wear long-sleeved shirts and long pants that are made of fire-resistant materials — like 100 percent cotton or wool — when conducting a burn, and to avoid wearing materials like nylon.

In Linn County, anyone planning to conduct a prescribed burn must get a permit from the county. While the Pattersons’ property has a Cedar Rapids address, it is not inside city limits. Open burning is prohibited within the city limits of Cedar Rapids, Marion, and Hiawatha.

What are the benefits of a burn?

Ahrendsen said one key reason Iowa has such rich, healthy soil is because of years of prescribed burns. The fire shifts soil nutrients around to a state that is more favorable for prairie species to thrive.

He said when fire comes through and burns the tall prairie grass, it weeds out invasive plants, removes old vegetation and creates more pockets of land for sunshine to penetrate to stimulate new growth.

“The root systems in prairie plants are very deep — sometimes up to five or six feet deep — which allows for that fire to come burn through and basically kill the plant or the grass,” Ahrendsen said. “But that deep root is able to withstand that and then re-sprout.“

Ahrendsen said one of the reasons Iowa has some of the highest quality Black Walnut trees is because the soil benefited from prescribed burns.

Lisa Fischer Walter, president of the Iowa Prairie Network, said prairie land has living tissue under the ground “all the time.”

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Fischer Walter said that when new prairie grows in the spring, there is a layer of litter, or “thatch,” that builds up between the soil and the plant. This layer of thatch makes it difficult for a growing prairie to get all the photosynthesis it needs to thrive.

“If a fire comes through that area and removes that litter, then there's greater light penetration to the soil,“ Fischer Walter said. ”So you get faster regrowth ... a lot of these perennial, native prairie plants are stimulated by periodic fire.“

She said that a prairie management plan — even if it’s not using fire — is essential to maintaining a prairie, or other plants will dominate the prairie species.

Jason Dykstra, a park ranger with the Iowa Department of Natural Resources said it can be hard for some people to wrap their minds around prescribed burns because of the dark, ashy-looking plants that are left behind.

“It can look pretty dramatic, but it’s important to remember that fire has always been a part of this landscape, whether it was naturally set or set by Indigenous folks that were here prior to us; our native vegetation is adapted to that,” Dykstra said. “It helps keep the competition of other plants away. It’s a benefit even though it doesn’t quite seem like it is when [the fire] first rolls through.”

Dykstra said prescribed burns are beneficial for woodlands, in addition to prairie.

Specifically, he said the burns are a helpful tool because they can treat more land quicker than conservationists could do by hand.

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How can Iowans capture the benefits of prairie burns?

Because seeing tall flames from a prescribed burn can be daunting to some, Dykstra said Iowans interested in prairie burns should learn more.

“Don’t be alarmed, it does look kind of scary when you first look at the flames, but I’d encourage people to come by and take a look at what these burns look like,” he said.

Fischer Walter said that not everyone can have an open burn to treat their prairie.

“Sometimes people can’t burn in the situation they are in, so they think they can’t have a prairie. But burning isn’t the only method,” she said. “There's no absolutely perfect solution to replace burning but if you think about the function, it removes litter, and it suppresses woody plants, so mowing can do some of that.”

Fischer Walter said that conservationists can also hay their prairie, meaning cut the tall grasses and use them as hay for animals rather than burning it.

When it comes to how often a prairie should be burned, Fischer Walter said there isn’t a perfect answer. But she said the Iowa Prairie Network recommends burning prairie every two to three years.

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Bailey Cichon and Nick Rohlman of The Gazette contributed to this report

Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

Comments: (319) 398-8370; olivia.cohen@thegazette.com