Science fiction meets fact with bog enclosures in experimental forest

BOVEY — Over a mossy bog in an experimental forest, polycarbonate platforms sit on aluminum docks that form three branching boardwalks. The boardwalks connect octagonal structures rising 26 feet above the ground. Each structure is walled in transparent panes and adjoined by an array of equipment controlling its interior environment.

Inside each of the 10 enclosures, foliage domes automatically tip closed at regular intervals for gas sampling, then reopen. Tree trunks are wrapped in silver to measure water use, and robots maneuver through underground tunnels to photograph root systems. There are wires and antennae everywhere, including on an instrument-laden tower at the center of each enclosure.

Does anyone ever mention that the SPRUCE experiment — the acronym stands for Spruce-Peatland Responses Under Changing Environments — feels like something out of science fiction?

"I've heard all that," scholar Paul Hanson acknowledged, "but it's science reality."

Although there's nothing imaginary about the SPRUCE experiment, its investigators do have something in common with the creators of science fiction. Typically, science fiction stories extrapolate future scenarios from what we know about the present and try to imagine what life will be like under those conditions.

In the SPRUCE experiment, scientists are simulating conditions in a range of possible futures with varying degrees of climatic warming. In the most extreme case, they're subjecting the natural vegetation found in a northern Minnesota bog to persistent warming of 9 degrees Celsius.

"Twenty-four hours a day, 365 days a year, we've added 16 to 17 degrees Fahrenheit on top of what you're measuring, which as you imagine, in August gets to be pretty hot," Hanson explained about that condition. "This experiment is designed to have an enclosure system that gives us a glimpse at a possible future."

The genesis of the SPRUCE experiment goes back two decades, to conversations among staff at the Oak Ridge National Laboratory in Tennessee. Hanson is a corporate fellow there, though he's originally from Minnesota and maintains a lake home here.

"Many other, very useful, studies of warming are done in petri dishes, in jars on laboratory shelves, or using different methods in smaller plots," Hanson explained. "Oak Ridge National Lab's goal was to take on an experimental system that encompassed the diversity of the system it was studying."

Minnesota already had an "experimental forest" containing peatlands, a type of terrain that's especially salient to envisioning the future of a warming planet.

"Peatlands," said Hanson, "store one-third of the terrestrial carbon in the globe. So the question becomes: If we're changing the climates under which these peatland stocks were stored and developed since the last glaciation ... what's going to be their fate? Are they going to stay there, or are they going to be released to the atmosphere as greenhouse gases?"

The Marcell Experimental Forest, a 2,819-acre research site located about 25 miles north of Grand Rapids within the Chippewa National Forest, was designated in 1962 with an eye to the study of peatland watersheds. The SPRUCE experiment — run by Oak Ridge and funded by the U.S. Department of Energy — was established with the permission of the U.S. Forest Service.

The enclosures went into operation in fall 2015, for an experiment that will run ten years. After the study ends in 2025, the chambers will be disassembled and the peatland will return to its natural state. "They may choose to keep these boardwalks because it's a nice way for them to access the bog for future work," said Hanson.

Given the scope of the experiment, which will ultimately have a total cost of over $20 million, scientists aren't wasting a single datum. Inside a control enclosure — one that's not heated, to establish a baseline — Hanson explained the purposes of numerous devices positioned among the foliage to monitor the ecosystem's status. Each instrument is replicated in each of the 10 enclosures, which are subjected to varying degrees of heating as well as carbon dioxide elevation.

The site administrators are serious about safety. When News Tribune journalists arrived on-site, Hanson's colleague Kyle Pearson led a briefing that accounted for scenarios up to and including the unlikely, but conceivable, possibility that an enclosure's carbon dioxide level could become unsafe for human respiration.

"There is an audible siren and a visual strobe light," Pearson explained. "It's not like you need to run out because your life is in grave danger, but you will want to exit the enclosure in an orderly fashion."

Although the enclosures may appear reminiscent of "biodome" experiments, they're actually open on top: Simulating real-world conditions in completely enclosed environments would simply be too complex, explained Hanson.

"In order to do ecological study, you have to get snowfall and precipitation," he said. "That adds a tremendous level of complexity because there's chemistry to the rainfall, not to mention the dynamics of making snowflakes." Although dividers extend about 10 feet, or more, into the ground under each enclosure perimeter, some wild animals still find their way inside.

"Birds can fly in if they choose to. Insects fly in and out. We see frogs, snakes and the occasional mink," said Hanson. "I don't know exactly where they get in, but they can get into your house, too."

It will take years for all the study's findings to be processed and published, but with respect to global warming, the news so far isn't good. "All the levels of warming we have lead to lost carbon from this system," said Hanson. In other words, as the planet warms, carbon escaping the world's peatlands will only compound the problem.

Much of that effect is due to changing microbial activity below the bog's surface, but you don't need fancy instruments to see the effect a changing climate might have on Northland bogs. In the warmest chamber, shrubs have proliferated and it's become difficult to discern the protecting layer of sphagnum moss so visibly prevalent in the non-heated control chamber. "The sphagnum moss does not like the warming treatments whatsoever," said Hanson.

"The other thing you see in this warming treatment is that some of the trees have died," added Hanson. One ominous event occurred in 2016, during the experiment's first spring thaw.

After some spring weather, a late cold snap hit the forest. The unheated trees, including those outside the enclosures, survived because they hadn't yet come out of winter dormancy. Some of the trees in the warmer chambers, on the other hand, had come out of dormancy and became vulnerable to a deadly freeze that chilled even the temperature-elevated enclosures.

The Oak Ridge scientists initially considered other locations for the elaborate experiment, including the Appalachian Mountains near their lab. In the end, it was the combination of Minnesota's rich peatland environment and the experimental forest — set aside for science — that landed the project in the Northland.

"We were told to be bold, innovative and 'make failure a large percent of your possibility,'" said Hanson. While the SPRUCE experiment has uncovered some troubling information about the future of Earth's climate, as a scientific project it's been a resounding success so far.

During a recent review by Department of Energy representatives, said Hanson, even professionals used to the wonders of 21st century science were amazed by the scale of the project. "They said, 'We'd seen the pictures, we'd seen the description, we'd seen some of the publications — and we had no idea.'"

For more information on the SPRUCE experiment, including opportunities to visit the research site, see mnspruce.ornl.gov.