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VOL. 45 | NO. 36 | Friday, September 3, 2021

Dishing the dirt on top ORNL scientist

Iverson searches for climate change solutions underground

By Nancy Henderson

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Summer vacations came with a given for Colleen Iversen and her family: Every time they spotted a road cut while driving to their destination, her geologist parents would undoubtedly pull off the busy highway to survey the exposed layers of rock in the ground.

“But while we were out looking at rock faces and monuments and national parks, I was always way more fascinated by all of the living things that are lush and green, or things that moved,” says Iversen, 42, senior staff scientist at the Climate Change Science Institute at Oak Ridge National Laboratory.

In some respects, the personable, down-to-earth biologist did follow in her parents’ footsteps by choosing a career that keeps her peering into what lies underground. Deemed one of the world’s most-cited researchers on Web of Science (an academic subscription database), Iversen purposefully digs up correlations between plant roots, soil and global warming and shares the information with audiences from colleagues to kindergarteners in a way everyone can understand.

A few years ago, the Ecological Society of America named her an Early Career Fellow for leadership in her field.

Verity Salmon, a research and development associate at the Climate Change Science Institute, first met Iversen in 2015 when she was finishing her Ph.D. dissertation and now works in her mentor’s research group at ORNL.

“Colleen’s greatest strength is her willingness to tackle hard problems in science,” Salmon says. “The world of roots is notoriously understudied compared to aboveground plant parts, but plant roots provide the nutrients and water plants need to grow. Without them, there would be nothing aboveground. … Plant roots are hard to study, though. I think that Colleen is exceptional because her root ecology work requires both creativity and hard work.”

Colleen Iversen, a senior staff scientist in the Climate Change Science Institute and Environmental Sciences Division at the Oak Ridge National Laboratory, digs up a tiny root in the woods at the UT Arboretum in Oak Ridge. “I love getting my hands dirty,” she says.

-- Photo By Michael Patrick |The Ledger

Growing up “way out in the country” near Lansing, Michigan, Iversen attended a small agricultural school and often picked up rocks from the long gravel driveway at her house to ask her mom what they were. Thanks to her good memorization skills, she later won a medal in a rocks, minerals and fossils competition at the state Science Olympiad.

But she was most in her element digging in the dirt and flipping logs to see what was under them on the 25 acres where her parents had, even before their children were born, planted spruces to harvest each Christmas.

Initially, Iversen wanted to study biochemistry but soon switched to biology, partly because her botany professor made up amusing limericks about various plant families to keep his students engaged. She went on to graduate school, she admits, not really grasping what she was supposed to accomplish there.

“I just knew I really liked learning about things, about science,” she says. “So I ended up there by happenstance. I feel like that’s my whole career. The next thing just happens.”

While earning her master’s degree in biological sciences from the University of Notre Dame, she studied peatlands – acidic, waterlogged wetlands in the world’s coldest places – in Michigan’s Upper Peninsula. Thousands of years ago, glaciers scooped out large depressions that filled with aquatic plants that didn’t decompose when they died. As more and more plants grew atop the accumulated plant material, the sites became major harbingers of carbon. Iversen and her team wanted to know how the peatlands might change if they added nitrogen or phosphorous such as that from farm water runoff.

“The big roots hold the tree in place, but they don’t take up any water or nutrients,” Iverson says. “It’s these little guys that are doing that.”

-- Photo By Michael Patrick |The Ledger

“They only cover less than 3% of the global land surface,” Iversen explains. “But they store more than a third of global soil carbon. What happens if we warm them up or dry them out? Is the carbon released back to the atmosphere as carbon dioxide or methane?”

Her adviser’s connections led her to the University of Tennessee, where in conjunction with nearby ORNL she researched the effects of rising carbon dioxide levels on sweetgum trees by giving them more of the gas through giant PVC pipes. Until then, she had no idea what the Oak Ridge lab even was.

Because plants thrive on carbon dioxide, Iversen and the other researchers expected the sweetgums, with their prickly round seed pods, to grow taller or fatter. “They did grow more,” she adds. “But what they did was grow more roots, and deeper in the soil. … That was where I got interested in what was happening below ground.”

The attraction sprouted from the root photos she observed. “When [plants] die, they contribute to the accumulation of carbon in the soil,” Iversen says. “That was so fascinating, and it also happens to be one of the biggest responses that we saw for climate change.”

The sweetgum forest experiment was drawing to a close just as Iversen started looking for a suitable post-doctorate fellowship, a sort of apprenticeship required of all Ph.D. science graduates before they can spearhead their own projects. After interviewing across the country, she was offered the opportunity to stay with ORNL and dig up the samples she and her peers had been so careful not to disturb for more than a decade.

“I’ve had these boots for 10 years,” Coleen Iversen says of the Xtratuf insulated neoprene boots she uses as she researches in the wild in Minnesota and Alaska to study the impact of greenhouse emissions and climate change on plants.

-- Photos By Michael Patrick |The Ledger

“Maybe that doesn’t sound super-exciting,” she points out. “But it’s very exciting to me to actually dig it out and put my hands on it and see what was happening outside of the pictures.”

A permanent job at ORNL was waiting for her when her studies wrapped up in 2010. She now leads task forces in several major projects, including an Alaskan tundra experiment designed to help scientists understand the rapidly-changing permafrost and another one in a rural Minnesota bog where she and her colleagues review photos supplied by underground robots and perform tests in the waterlogged soil system.

Last year, she became group leader of a new four-person plant-soil interactions team of scientists working on these and other projects.

Before the pandemic, Iversen eagerly looked forward to weekly “Root Picking Thursdays,” which allowed her to mingle with interns and postdoctoral students. Huddled around a table together, they used tweezers to carefully disentangle roots from soil samples while wearing “giant jeweler’s glasses like in a heist movie, except our diamonds are roots,” she says. “Some of the roots that we’re removing from the soil are finer than a human hair. The big roots hold the tree in place, but they don’t take up any water or nutrients. It’s these little guys that are doing that.”

These days, Iversen divides her time between overseeing projects, writing scientific papers and organizing conferences and, several times a year, traveling to the Minnesota and Alaska research sites. She also does a lot of public speaking, which surprises even Iversen given her shyness as a youngster.

Colleen Iversen shows off the root system of a Lace Leaf plant from her garden. 

-- Photo By Michael Patrick |The Ledger

“I tested as an introvert on the Myers-Briggs testing [back then],” she recalls. “And recently we had to retake those tests for leadership training, and I tested as an extrovert. And I about fell off my chair.”

Iversen feels driven, even obligated, to talk to others about what she does.

“All of the work that I do is funded by taxpayer dollars, and it doesn’t feel like it’s enough to me to just put my findings into scientific papers that wouldn’t be acceptable or understandable to ‘normal’ people. So it seemed important to me to be able to communicate what we’re finding to people of all backgrounds. That could be schoolchildren or it could be senators or it could be my grandmother.”

Students make the best scientists, she says. “They’re already using the scientific method. They are the best observers of the world around them and they are always asking questions.”

One way she reaches new audiences is through “Skype a Scientist,” a virtual program created by a graduate student before the pandemic to match teachers and students with experts like Iversen. It has since allowed her to visit classrooms across the U.S. and Canada.

She is also quite active on Twitter. “Sometimes early career folks will look at someone who has an amazing resume´ and say, ‘Boy, they must not have struggled. And since I’m struggling, that means that I’m not cut out to be here.’

“I don’t want people to think that. Everybody struggles, even the people with fabulous resume´s. So I’ve tried to be pretty straightforward about telling the challenges on Twitter or when I speak to people. It’s not about if you struggled. It’s about how you make it through that time.”

She says her favorite part of the job is interacting with interns and post-doc students. She understands just how nervous they get around established scientists; in her early days at ORNL, she got nervous too, just thinking about her role in the trajectory of their budding careers.

Iversen says she believes in giving her mentees room to grow, occasionally nudging them in the right direction.

Take, for example, the time that two of her students named a new global database designed to differentiate between types of roots.

“They had named it the Fantastic Root Ecology Database. They were calling it FRED,” she recalls. “And I was like, ‘Well, we want to publish this, guys, so maybe ‘fantastic’ wouldn’t fly with the reviewer. But since the tiny roots that are doing all the work are less than two millimeters in diameter – narrower than the cord that is connecting my headphones to my phone – and are called fine roots, we changed ‘fantastic’ to ‘fine.’ So the Fine Root Ecology Database was born.”

When asked about her strong points, Iversen quickly replies, “I care about people and connections and collaborations. The things that make me happiest are bringing together people to solve problems.” Currently, she is part of a 20-member working group spanning seven countries with a shared goal of tackling tough global questions.

COVID-19 brought its own set of challenges, of course, including the forced pause of Iversen’s cherished Root Picking Thursdays and the need to continue yearslong scientific measurements while keeping the researchers safe. On a personal level, Iversen contracted the virus in December and ended up in the hospital emergency room with pleurisy. During her recovery period, she took up a new hobby: embroidering trees, mushrooms and roots, along with the FRED logo, for friends across the country.

Her COVID symptoms are not completely gone but she considers herself one of the lucky long-haulers. “I feel pretty good most days and glad for the opportunities I’ve been given, like the science leadership, getting to see the big picture and how all the puzzle pieces fit together. The further I move along in my career, the more of the big picture I’m getting to see. And I’m really enjoying that.”

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