Five things everyone should know about . . . The Soils of Wisconsin

1 l Wisconsin’s soils were first mapped more than a century ago. The first soil map of Wisconsin was also the first ever made in the United States. It was produced in 1882 by geologist T.C. Chamberlin. In 1926, CALS soils professor Andrew Whitson created the second state soil map for his book Soils of Wisconsin. The third map followed 50 years later, compiled by eminent CALS soils professor Francis Hole. Since that time much new information and many insights have been gained, and these have been summarized in a fresh edition of The Soils of Wisconsin.

2 l The soils of Wisconsin are highly diverse. Nearly 80 percent of the state is covered with glacial deposits that differ in texture, composition, thickness and age (the Driftless Area, in western Wisconsin, was not glaciated in the most recent glacial period). There is a strong relationship between the soils and parent materials. The history of human impacts on soils in Wisconsin extends back 13,500 years but became intensified during the Late Woodland period (1,600 to 500 years Before Present) when fires were used to clear land, and further intensified in the mid-1800s when European settlers arrived and land clearing and large-scale crop production began.

3 l Many of Wisconsin’s soils are unique. There are more than 700 soil series (groups of soils with similar properties) in Wisconsin, and of these, 20 percent are considered endemic, having developed here through a unique combination of geology, plant communities and other factors. The “tension zone” between Wisconsin’s northern and southern forests contains 40 percent of these endemic soils while covering just 13 percent of the state’s land area. This zone also marks a transition not just in vegetation but in soil. The soils of the prairie, or Mollisols, mainly occur below the tension zone, and acid Spodosols, which often are forested, exist above it.

4 l Soils are affected by changes in climate. The melting of glaciers 11,000 years ago is a climatic event that affected Wisconsin’s soils, depositing millions of tons of glacial till and windblown, silty soil. For the future, we expect rising temperatures and increasing rainfall that will affect our soils and land use. In the winter, soils will cool more because of thinner snowpacks and less protection from freezing. The warming up will result in land use changes. Corn and soybean, for example, might be grown in areas that previously were unsuitable.

5 l Our soils yield profits. The soils in Wisconsin have a high yield potential and support an $88 billion industry. We observe highly significant correlations between the soil and such economic parameters as agricultural land value sales and adjusted gross income in every county of the state.

Layered features of vertically exposed prairie soil are pictured during a soil science class field trip to the University of Wisconsin-Madison’s Arlington Agricultural Research Station on May 27, 2014.
Photo credit: Jeff Miller/UW-Madison Communications

To the Ends of the Earth

In April 2011, James Bockheim led a small team of researchers to a rocky spit of land called Cierva Point, a habitat protected by the Antarctic Treaty as a “site of special scientific interest.” Home to breeding colonies of bird species like Gentoo penguins, as well as a remarkably verdant cover of maritime plants, Cierva Point is also one of the most rapidly warming places on Earth.

Bockheim and his crew were beginning another field season on the Antarctic Peninsula, the long finger of rock and ice that snakes past Palmer Station, the United States’ northernmost Antarctic research station, and curls out in the Southern Ocean (see map, page 25). They’d been deposited onshore, along with their gear, by the Laurence M. Gould, a research vessel that wouldn’t return until late May. As the ship sailed back into the frigid sea, Bockheim turned his attention not to penguins or polar grasses, but to the ground beneath his feet.

Every year there was more and more of that ground as glaciers drained into the Southern Ocean, revealing soils and bedrock that had been covered in ice for millennia. Bockheim wanted to know what was going on underneath the newly exposed surface and had brought along a soil and bedrock coring tool, a device that looks like a cartoonishly oversized power drill, to get to the bottom of it.

His crew fitted the drill with its two-meter-long impact hammer bit. Graduate student Kelly Wilhelm pointed the drill at the ground and pulled the trigger.

It wouldn’t be the first time that Antarctica caught Bockheim by surprise. Bockheim, a CALS professor of soil science, has spent his career studying polar and alpine soils. From field sites north of the Arctic Circle to mountain passes in the Andes and the dry valleys of Antarctica, Bockheim has worked to classify and understand how soils are formed in the Earth’s coldest climates.

Bockheim first set foot on Antarctic soil in 1969 as a Ph.D. candidate at the University of Washington. Although his dissertation was on alpine soils in the Cascades, his advising professor had a project in Antarctica and invited him to come along.

“And that was it,” Bockheim recalls. “It just got in my blood.” Startled by the “peace, solitude and stark beauty,” he knew he would have to return.

Six years after that first trip, Bockheim got his chance. He had recently accepted a position at the University of Wisconsin–Madison when a call came in asking if he’d like to join a glacial geologist from the University of Maine on a multiyear research project in Antarctica’s dry valleys. Bockheim’s reply was succinct: “Absolutely.”

Over the next 12 years, Bockheim returned to Antarctica each year for a two-month stint of digging out soil profiles, collecting samples and boring holes into the continent’s surface, especially in the largest ice-free region of Antarctica, the McMurdo Dry Valleys.

It was during this time that Antarctica presented Bockheim with its first riddle. The dry valleys are a “polar desert,” a system that rarely gets above freezing and, even when it does, contains precious little water.

As in other places with permafrost—soils that stay at or below freezing for two or more years at a time—soils there are primarily formed by cryoturbation. Also called “frost churning,” cryoturbation is a process by which what scant ice there is freezes and then thaws year after year, breaking up bedrock, working surface particles down into the ground and bringing buried particles up. Such mixing is never a quick process, but in the dry valleys of Antarctica it occurs at an especially glacial pace.

The resulting material didn’t exactly fit what Bockheim knew to be the generally accepted definition of soil. While the weathered substrate had been eroded and deposited in layers over millions of years, it often looked more like a combination of loose pea gravel and sand. What’s more, only lichen and mosses were found growing in it, not the “higher plants” usually considered a prerequisite for soil status.

But to Bockheim, that requirement was a relic of soil taxonomy’s tendency to classify soils based on what human uses they could sustain, like crop production or road building. In Antarctica, such endeavors were a moot point.

In a 1982 paper published in the journal Geoderma, Bockheim made his first mention of these polar soils in the scientific literature. The journal’s editor, anticipating pushback from other soil scientists, urged him to first define the word “soil” for his readers. Bockheim produced a definition similar to the existing one, with one small change— “higher plants” were nowhere to be found. It was the opening salvo in a scientific debate that would simmer for more than a decade.

By 1987, after 12 uninterrupted years of spending field seasons in Antarctica, Bockheim decided he needed a break. He was tired of leaving his wife and five young daughters back in Madison for two months at a time and wanted to stay closer to home. While the move shifted his focus to the forest soils of northern Wisconsin, Bockheim continued to publish papers on his research on Antarctic soils.

Then, in 1992, the Soil Conservation Service (now the Natural Resources Conservation Service) took note of Bockheim’s argument that the existing classification system didn’t do polar soils justice. He was asked to lead a committee discussing the need for a new order of soil. The result, after a few years of lively debate, was the addition of Gelisols, or “permanently frozen soils,” to the USDA catalog of soil types.

“These soils were far away, poorly researched, and people thought they might be insignificant because we couldn’t grow anything on them,” says Bockheim’s colleague, CALS soil science professor Alfred Hartemink. “But with time came knowledge, and it was recognized that this is a large part of the world, and soils were being classified there incorrectly.”

The soil classification system had been set at 10 distinct orders of soil for so long, Hartemink says, that the change “was a bit like adding another month to the year. But Jim was able to build that body of knowledge, consolidate it and pull it off. That was an immense deal.”

It was an impressive first half of a career. In fact, it would be an impressive list of accomplishments for any scientist’s entire career.

But Bockheim isn’t just any scientist. He has spent 20 tours of scientific duty in Antarctica, 19 field seasons in the Arctic Circle and several in alpine ecosystems across the world’s mountain ranges. He recently returned from a two-month trip to South America, where he’d received a Fulbright grant to teach classes on Antarctic soils in Chile and a special invitation to teach a similar class in Brazil. During that visit he took a side trip to the Andes, where one of his graduate students deployed tiny temperature probes, called thermistors, into the frigid soils.

Even in more domestic climes—say, the stairwells of King Hall, home of the Department of Soil Science on the UW–Madison campus—Bockheim bounds down the stairs from his office to his lab. “Fit college students sometimes have a hard time keeping up with him in the field,” says Kelly Wilhelm, who has spent two field seasons with Bockheim in the Antarctic.

That energy carries over into the more cerebral part of his profession. Bockheim has authored 170 scientific articles, and his work is cited by other scientists at a rate almost unheard of in soil science circles.

“Jim wrote three books in two years,” notes Hartemink. “Who does that? Most scientists write one every five, maybe 10 years. I can’t think of anyone else who could do that.”

The books—Soil Geography of the U.S.A., Cryopedology and The Soils of Antarctica, the latter two coming from the publishing house Springer within the next year—promise to serve as definitive works in the field.

So it’s not just fit college students who can’t keep up. Bockheim is considered by many to be one of the top cryopedologists—scientists who study frozen soils—in the world.

Ironically, after all of his painstaking work describing how polar soils had come into their ancient, frozen state and, quite literally, putting them on the map, many of the Gelisols Bockheim had worked to have reclassified began changing—their defining characteristics melting away.

“We’re literally losing these soils,” says Hartemink. “There are soils disappearing just like there are species disappearing.”

The question now is: What happens when the world’s “permanently frozen” soils begin to thaw?

Bockheim first began asking that question nearly 20 years ago, when he again received an offer he couldn’t refuse. This time, however, it was an invitation to study the opposite pole.

In 1995, after several years focused on his growing family and the soils of Wisconsin, Bockheim returned to polar soils, assuming command of a project focused on permafrost 320 miles north of the Arctic Circle, near Barrow, Alaska. Knowing where different soil types were located and how they’d gotten there, Bockheim knew, was the first step in trying to predict what they’d do as they warmed.

Understanding the fate of permafrost in a warmer world may be one of the most crucial pieces of the climate change puzzle. For millennia, the hard layer of frozen soil has contained vast amounts of carbon and methane, which contribute to greenhouse gas levels when they are released into the atmosphere. As Earth warms, so does this soil, pushing the permafrost line deeper and freeing up more and more soil to release carbon and methane via processes like erosion or microbial activity.

In 2004, the New Zealand Antarctic program was starting a mapping project and wanted Bockheim’s expertise to help add Antarctic soils to their efforts.

Bockheim jumped at the chance to reconnect with the continent he’d first fallen for, but Antarctica surprised him again. The place he returned to looked nothing like the one he remembered.

Handheld GPS devices didn’t exist during Bockheim’s first foray into Antarctic fieldwork in the 1970s. Scientists instead relied on landmarks like mountain peaks, glaciers or snowbanks to lead them back to their annual field sites. Bockheim’s team relied on snowbanks that dotted the dry valley landscape, set down in distant, less arid eras. Using aerial photographs and topographic maps, the team could work out roughly where each site was located.

But 30 years after those pictures had guided him, they’d been rendered obsolete by more than updated technology. “I had taken a picture of snowbanks from the helicopter in 1975,” Bockheim recalls, “and it’s just by chance that, when I went back in 2004, I took a picture from the exact same spot in the air. But the snowbanks were gone.”

Of course Bockheim wasn’t caught completely off guard by these developments. Like any scientist studying the poles, he knew that temperatures over the last four decades had been rising. In fact, at Antarctica’s Palmer Station, the mean annual air temperature was up three and a half degrees Celsius. In winter, the mean temperature during that span had risen nearly 10 degrees Celsius, or 18 degrees Fahrenheit. Even so, the magnitude of the observed changes was startling. “There was water everywhere,”

Bockheim remembers. “I’ve got a whole shelf of field books and I take notes on things like the weather and conditions. In December it would always still be extremely cold.”

During his first 12 years working in Antarctica, he says, “there was always a stream in one of the valleys and maybe some smaller lateral streams that would run in the warmest time of the year, from mid-December to mid-January. But when we went back in 2004, it was so warm that there was just water everywhere, even on the high mountain slopes. There were wet patches of snowmelt coming down the slopes.”

Where areas on the Antarctic Peninsula had once thawed for two months of the year, they were now above freezing for up to five months. That warmth and the water had rejuvenated processes like the pattern of ground freeze from cryoturbation, Bockheim recalls. There was highly developed soil becoming exposed.

The only thing that was as he had left it 17 years prior was Bockheim’s own energy and enthusiasm for Antarctic fieldwork.

Malcolm McLeod, now a soil scientist with the New Zealand–based institute Landcare Research, spent three field seasons on the project mapping Antarctic soils with Bockheim. Bockheim soon became McLeod’s doctoral advisor. “Because of his wealth of Antarctic experience, he was able to focus on the important bits of the soils puzzle that told a story,” McLeod recalls. “He worshiped data, and he had this line—‘Soils never lie.’”

During their project, that mantra led Bockheim to make what McLeod calls “big advances” in scientists’ understanding of how Antarctic soils form. Antarctic glaciers are “cold glaciers,” meaning they don’t melt. They advance when large chunks break off the leading edge, and they retreat by ablation, or evaporating straight from their frozen state into the cold, dry air. As a result, the Antarctic landscape has none of the usual telltale signs glaciers leave behind to provide a history of the region’s geology. Bockheim showed that soils could tell the story.

Bockheim’s wealth of experience also carried over into field camp. “His breakfast bacon and hash browns couldn’t be beat,” says McLeod. “I also remember his ‘hot towel’ dispensed airline-style each morning by dipping a paper towel into a billy of hot water.”

Nearing the two-decade mark of fieldwork in the Antarctic, Bockheim had become both an accomplished scientist and a veteran polar explorer. But after so many years in the polar desert, his mind began to wander to greener pastures.

“I’d done all my work in Antarctica in the dry valleys in the interior mountains, and I kept hearing that the peninsula was quite a different environment,” Bockheim says. “On the peninsula, it’s a whole different world. You have rain, whereas, historically, no one has ever experienced rain in the dry valleys. That rain causes accelerated soil formation and there are plants, a lot of lichens and mosses, but also there are two higher plants, one a grass and the other a member of the pink flower family.”

What would this greener landscape mean? Was Antarctic soil seeing an increase in the “active,” or unfrozen, layer of soil? Was the permafrost being pushed deeper below ground? Bockheim knew that the peninsula would be the best place to study how the warming he was witnessing was impacting Antarctica.

“So I wrote a proposal and decided to strike out on my own rather than being under someone else’s research priorities,” he says. That proposal led Bockheim to Cierva Point with a gigantic power drill in 2011. It was the reason Kelly Wilhelm was bent over the soil driving a two-meter-long bit into the ground. And it was the beginning of addressing yet another Antarctic riddle.

“We are trying to be one cog in looking at how climate change is affecting the Antarctic Peninsula,” says Wilhelm. “There are people looking at air temperature and changes in weather patterns. Other people are looking at how far south the vascular plants grow, or migration patterns of seals and penguins. But permafrost—on the peninsula, at least—has pretty much been one of the last things to be examined.”

When Bockheim headed to the Antarctic Peninsula, the only prior information his team had to go on was a soil survey conducted in the 1960s during April, the warmest month of Antarctica’s short summer. On that survey, researchers dug 40 centimeters into the soil, or less than half a meter, before hitting hard permafrost.

Bockheim’s team knew that the permafrost would now be deeper, as surface soils warmed with the surrounding air temperatures. They had prepared for the change by bringing drill bits that would bore into the soil more than four times deeper than the last known permafrost.

It wasn’t enough.

“Not one of our holes hit permafrost,” Wilhelm recalls. What’s more, the temperature at the bottom of every hole was well above freezing, suggesting that the permafrost was located several meters beyond the reach of their drill.

If soils never lie, what is the unexpectedly warm peninsula trying to say? “That is the grand unsolved question,” Bockheim says. “Based on the latitude, we expected the active layer to be thinner,” which would have meant a much shallower permafrost table. Bockheim says that the distribution of sea ice and westerly flows of air and sea- water may play a role, but—so far—they can’t explain it.

“It’s what we’re writing papers on right now,” says Wilhelm. “People don’t even know about this. It’s a pretty new thing.”

Whatever the answer, one fact is undeniable. The seasonal thaw, or “active” layer of polar soils, is increasing. That means that more and more soil near the Earth’s poles is being grown over with plants, worked over by microbes and eroded by wind and rains. In the Arctic, this activity will undoubtedly lead to the release of carbon and methane, making it a huge source of those greenhouse gases.

In the Antarctic, though, the picture is still fuzzy and may in fact produce an effect that is, well, the polar opposite. The plants beginning to carpet Antarctic soils could end up pulling carbon dioxide out of the atmosphere instead of adding to the problem like the Arctic’s melting permafrost.

“In the Antarctic, with its increased land mass, increased plant cover and, presumably, increased photosynthesis, one could easily argue that it could become a sink for atmospheric carbon,” says Bockheim. And, in fact, that’s exactly what Bockheim thinks will occur—at least temporarily.

Beyond that, the man who wrote the book on Antarctic soils is content to wait and see. The soils don’t lie, but they may yet have one more surprise in store.