Nebraska's Unique Habitats: Indian Cave Oak Woodlands

A burned area of Indian Cave State Park, where sunflowers are coming back in. (Photo by Chris Helzer, The Nature Conservancy)
An unburned area, overgrown with vegetation. (Photo by Chris Helzer, The Nature Conservancy)
Oak seedlings are well-adapted to survive fire, which opens up the forest canopy and allows sunlight to reach them so they can grow. (Photo by Chris Helzer, The Nature Conservancy)
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December 25, 2017 - 6:45am

This week, we’ve been hearing about Nebraska’s unique landscapes and the work of people across the state to conserve them. For our last story, we head into the woods.

We’re standing waist-deep in greenery, under a forest canopy so dark we can’t see the sun. Combined with mid-summer humidity, it almost feels like a jungle. We’re on the far eastern edge of Nebraska, at Indian Cave State Park.

“This is what a lot of the park was like before we started managing it,” says Gerry Steinauer, a botanist with Nebraska Game and Parks Commission. “Very shady, so there's little sunlight hitting the forest floor.”

Steinauer explains that oak trees need at least 40 percent open canopy to grow from little seedlings to saplings to mature trees. “Here, the canopy closure is probably 95 percent. So little sunlight is hitting those seedlings that they just cannot grow,” he says.

Because many plants require a lot more sunlight than this canopy provides, Steinauer says the plant diversity in this part of the forest is far lower than what it should be. An 1813 painting of the Missouri River bluffs by Karl Bodmer offers a reference to what the landscape was like 200 years ago, Steinauer says.

“Historically this area probably had denser woodlands in the cool and wet north and east slopes and in bottoms. A lot of the south and west facing slopes were probably open prairie or just scattered oak woodlands,” Steinauer says. “Now, if you look at Indian Cave, it's just this solid forest. We've lost the prairie, we've lost the open oak woodlands and savannas, plant species diversity, our animal diversity.”

As a companion to this story, our 360-production team captured immersive video and audio to give you a taste of these habitats. You can view these on your smartphone or on your desktop. For desktop viewing, we recommend the latest version of the Chrome browser for the best experience (Safari and older versions of Internet Explorer do not support 360 video at this time). And we also recommend you view with headphones to get the full effect of the 360 audio. 

“It's important to understand that oak woodlands are not just an accident of geography and climate,” says biologist Kent Pfeiffer of Northern Prairies Land Trust. “They were actually, to some extent, created by Native Americans through the management that they used on this landscape over the last five, ten thousand years. The management tool that they used the most was fire.” All that fire created rich biological diversity. But as we’ve removed fire from the landscape in the last 100 years, we’ve lost much of that.

Three of the at-risk species benefiting from management at Indian Cave State Park: (from top) the Turks cap lily, the timber rattler, and the yellow lady slipper. The Nebraska Natural Legacy project seeks "to refine and implement a blueprint for conserving Nebraska’s flora, fauna and natural habitats through the proactive, voluntary conservation actions of partners, communities and individuals."

(Photos courtesy NEBRASKAland Magazine/Nebraska Game and Parks Commission)

“You have oak trees in these kinds of woodlands, but they're just persistent on the landscape. They grew up a century ago and they've been here ever since and they've survived because oak trees live a long time. There's no small oak seedlings in the understory. As the oaks go, the whole suite of species that are dependent on woodlands go with them,” Pfeiffer says.

About a decade ago, Pfeiffer says they started realizing that without management, Nebraska’s oak woodlands were likely to disappear.

“The prairies were kind of choked with brush, the woods were choked with brush. There was a lot of bare soil in the woods.”

Steinauer and Pfeiffer are part of a long-term effort to improve the diversity of the woodlands at Indian Cave. Krista Lang, also of Northern Prairies Land Trust, has been working on restoration at the park since 2011. We move to a different area, where she shows the difference their management has made. The woodland in front of us is much more open, partly, Lang says, because it’s south and west facing, which means it’s sunnier and drier.

“We've also done some thinning through here, so that's really helped to open up the understory of the woodland. But mostly, a lot of this is fire,” Lang says. “We've had some pretty good rip roaring fires through here, which were pretty exciting. It's doing amazing things already,” she says, pointing to sunflowers growing in the open area.  

To thin, they use a technique called hack and squirt to deliver herbicide to non-desired tree species. But bringing fire back to the landscape is their best tool, Lang says, in part because oaks have evolved to withstand fire much better than other tree species. Fire also cleans up the forest floor. They do large burns in the winter months, and try to burn the whole park—about 3,000 acres, each year.

“We never thin without burning because everything likes sunlight. The oak seedlings really need the sunlight to be able to grow, but all the other seedlings of the other kinds of trees like sunlight, too. They grow a lot faster than the oak trees do. We have to have the fire to sort of weed out the other tree species,” Lang says.

And Steinauer says it’s working. “Just looking around, we’ve seen three oak saplings that are about this big now,” he says, gesturing to calf-height. “Previous to our fire and thinning, you would've never saw that.”

We hike into another spot, walking along a ridgeline. Steinauer points out native prairie plants that have started coming back in.

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“We're finding that as we open these woodlands with fire and thinning these ridge top prairies are expanding somewhat down slope, and we're starting to see more of these species. More big bluestem, more Indian paintbrush, more purple prairie clover,” he says.

Though the park isn’t home to any endangered plant species, more rare plants are making a comeback. Steinauer says recreating the diversity of habitats that used to exist here is important.

“A lot of people look at conservation, and what they hear in the news is about endangered and threatened species. But if you take a broader approach and look at these ecosystems, these oak woodlands at Indian Cave State Park and along the Missouri River Bluffs probably harbor thousands of species when you start talking about insects, plants, mosses. By protecting ecosystems, you're protecting huge number of species,” Steinauer says.

Pfeiffer says if we want oak woodlands in the future, we have to figure out how to manage them so they can sustain themselves.

“The question is never to be what they used to be like. It's what are they going to be. And the past provides a frame of reference but really what matters is if we can pass them on to future generations,” Pfeiffer says.

On a ridge above the Missouri River with a wide view of the forest below, he reflects on the years of work behind and ahead. Like any kind of land management, the work will never end.

“We have a lot to learn but it all seems to be moving in a positive direction. If we can sustain that I think there's a chance that these woodlands will still be here in a 100 years,” Pfeiffer says.

Pfeiffer, Steinauer, Lang and others have been sharing their work, helping landowners and state parks across southeast Nebraska manage their woodlands, so those, too, will be around in the future.

This story is part of an in-depth report looking at unique habitats of Nebraska, as part of the forthcoming documentary “RARE: Creatures of the Photo Ark,” which follows renowned Nebraska photographer Joel Sartore’s quest to photograph 12,000 species and create worldwide awareness about threats facing animals in Africa, Asia, Europe, North America and Oceania.

Editor's note: This story is part of our "Best of 2017" Signature Story report.  The story originally aired and was published in July.



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