On top of a high sandy ridge, I looked south and west across the broad St. Croix River valley, toward the forested bluffs of Wild River State Park on the other side. Surrounding me was the scrubby vegetation and open landscapes of the Sterling Barrens State Natural Area, north of St. Croix Falls, Wis. It was mid-morning and already hot.

Many people have mistaken this sandy ground for worthless, sterile soil. No crop could grow here. Settlers gave it the name for something the opposite of fertile: barren. But on high hills of sediment left by roaring Ice Age rivers, there is an abundance of life, a crowded community of plants and animals who call it home.

I walked through this secretly lush landscape with Derek Anderson of St. Croix Falls, a botanist by profession and passion. He surveys plants as a Minnesota Department of Natural Resources employee, and, in his free time, has been part of an ambitious project to document the flora of the unique sand barrens in northwest Wisconsin.

It was the height of the growing season, and Anderson was looking for a few more plants to formally document, while pointing out the numerous native species growing there. They are remarkably specialized to survive and thrive in this difficult environment. The sun is intense and the soil is dry, but life finds a way.

As we walked down a disused two-track trail, our feet sunk into the soft, sandy ground. Despite this difficult environment, a mosaic of plants fought for the sun on either side of the trail, many flowering, many clearly thriving in the sun and the sand. If the rolling sand barrens are a little like walking through Saharan dunes, these rolling hills of sand are covered in a hardy green crust of life.

Harsh habitat

The Northwest Sands are the remnants of deposits from raging rivers of glacial meltwater. The sand is piled hundreds of feet above the bedrock in many places. In some spots, it is perfectly flat, the effect of settling out evenly. In other places, it is hilly, caused by depressions created by huge chunks of ice that were buried under the sand, and slowly melted.

The barrens can be harsh. The sun beats down with little to stop it, the soil and the air are dry, the openness disorienting. Farmers, largely defrauded by land speculators, briefly tried to cultivate the barrens in the early 20^th century. The land refused to be used, seemed to reject settlement, and there are few human residents here now.

Yet the barrens are anything but bare, are in fact bountiful. Indigenous people have long known the landscape provides valuable resources even in the harshest seasons. They are especially rich in berries, including beloved blueberries, and are home to many kinds of birds and other animals.

As soon as we stepped off the road, we encountered our first rare species, silky prairie clover (Dalea villosa). Designated as a species of special concern in Wisconsin, it is highly specialized to sandy prairies. The plant prefers deep sand soil, sending its roots down as far as five feet. It can survive in areas receiving less than a foot of rain each year, including deserts. It was easy to understand why silky prairie clover was growing at the sunny and dry site.

Sterling Barrens is a “stronghold” for it in Wisconsin, Anderson told me. It is at the eastern fringe of its range here, where the west’s vast prairies cross the St. Croix. But the barrens are still on the edge of the East. Another species seen here is Canada frostweed, a plant of sandy soils east of the Mississippi. It reaches its western extreme here.

The barrens are an intersection and a tension zone, where east meets west, north meets south, where grasslands meet woodlands.

“Barrens are a play between forest and prairie,” Anderson said. The plants reflect these intersections, representing numerous ecosystems. It makes for an uncommonly high number of diverse species.

And it’s what makes the study Anderson and his partners have undertaken so interesting. Working with Ashland, Wis. botanist Paul Hlina, Rick Haug, and others, their multi-year project has carefully surveyed several large tracts of public land in Wisconsin’s “Northwest Sands” ecological region. Much of this landscape is in the St. Croix River watershed.

Documenting diversity

The sun was high in the sky as we cut a vague circle through the untracked barrens. Sometimes, Anderson stopped to identify or study a plant, pointing out its unique features to me. We were seeing familiar friends of his, as he and his partners have spent more than three years exploring, collecting samples of hundreds of species (with permits), and carefully recording their findings.

Last August, I met Anderson and Hlina on the Namekagon Barrens Wildlife Management Area, where we went looking for rare plants, this time with a northern forest influence. But it was late summer during a historic drought and the pickings were slim. They said it appeared many plants had basically given up on growing, saving their energy for next spring. I’ll share more about that area in the future.

By documenting a lot plants, Anderson, Hlina and their collaborators have created a database of what is living where. One clear finding has been that the Northwest Sands spans a spectrum, ranging from the prairie-influenced southwestern sites like Sterling Barrens, to northern sites that have species reflecting their higher latitude.

Sterling has turned out to be one of the most botanically diverse sites in the Northwest Sands. With 180 native plant species identified, it has the third highest number of species of any of the sites, trailing only Fish Lake and Crex Meadows Wildlife Areas, vastly larger properties. Sterling also has the lowest percentage of non-native species of all the properties studied.

Bumblebees and butterflies toured the flowers, feasting on nectar, carrying pollen. Dragonflies zipped by occasionally, hunting other insects like fighter pilots. Birds sang from unseen perches, with numerous species having been observed at the site.

Identifying all the plants means not just the brightly-colored flowers, but the grasses too, and the tiniest stems. A lot of surveying was done on hands and knees. “I’ve found many interesting things getting lost or falling down,” Anderson said.

Natural value

The barrens are a fraction of what they were historically, and what’s left is largely public land. Research into the rich web of life in this habitat can help land managers take care of what they have, and perhaps expand it. Anderson and Hlina’s survey helps makes sense of the intricate ecosystem and how to protect it.

Sterling Barrens is managed by the Wisconsin DNR as part of the Governor Knowles State Forest, with a bottomland area along the river owned by the National Park Service also included.

Much of what was once barrens is now planted in dense rows of red pine plantations, providing lumber and jobs, but almost no natural value.

“The negative impacts of red pine plantations on native species diversity is now well-understood, and there are many areas where this type of management is ecologically inappropriate because of the likely impacts to local biodiversity,” the latest state forest management plan says. “

One thing that has repeatedly been seen is that barrens need regular fires to remain healthy. Without fire, it will slowly turn to forest, possibly losing rare species and valuable habitat. Another conservation practice being encouraged is creating corridors of barrens habitat to connect disparate sites, effectively enlarging the habitat and deepening the gene pool for wildlife populations.

Our first loop ended with us crashing through a tight stand of young aspen, a colonizing colony of cloned saplings — another component of the barrens, which represents the need for careful management. Aspen will either begin the landscape’s transition to forest, or be suppressed by fire.

Messy mosaic

Emerging from the thicket, we returned to the road, where I enjoyed a long drink of water. Then we headed a mile to another part of the site. The barrens were more mature here, actively managed with logging and prescribed fire used to mimic natural processes.

On a sandy ridge atop a southwest-facing slope, Anderson pointed out a species of fame flower, Phemeranthus rugospermus, a species of special concern in both Minnesota and Wisconsin. It was not blooming — but rarely does. Each of its delicate pink flower opens just once for a few hours, during the hottest part of the year and hottest part of the day. Each plant may have multiple flowers, but each one blooms for one afternoon only.

A succulent, fame flowers are made to survive drought and direct sun. Sterling Barrens is at the extreme northern end of a range that stretches to Texas. It was first found by Europeans in what’s now Minnesota in 1832, a few miles south in Taylors Falls, by a scientist accompany Henry Schoolcraft on his government expedition seeking the source of the Mississippi.

We also saw other sand prairie specialists like prairie larkspur (Delphinium carolinianum virescens), large-flowered beardtongue (Penstemon grandiflorus), hairy puccoon (Lithospermum caroliniense), and green comet milkweed (Asclepias viridiflora) — which is unique because each plant can have one of two types of leaves, either long and skinny or shorter and crinkled.

On a knoll overlooking the river, a big bur oak with a high spreading canopy stood as a sentinel. It was a rare spot of shade, a good spot to cool off while admiring the view of the barrens and the broader valley.

Here, I could see how the barrens are not just one thing. It’s a patchwork of grassy openings and stands of scrub pine and oak, prairie openings, smaller than an acre, dominated by grasses and forbs. full-size trees scattered throughout, sometimes even open sand exposed to the air.

As Anderson told me, there is no pure ecological definition of “barrens.” Instead, it’s a specific, delicate mix of lands.

We break off the botanizing around midday. I’m soaked in sweat and coated in dust. I think of the farmers who gave so much trying to grow crops in this sun-blasted sand — and how the barrens already have so much to give.

Reference

Anderson, Derek & Hlina, Paul. (2022). 2021 Report on the Barrens Flora of the Northwest Sands Region of Wisconsin. 10.13140/RG.2.2.31246.84800.