Student researcher measuring trees in the Itasca ForestGEO plot near Itasca Biological Station.
How and why does the mix of trees in a forest shift over time? How do variations in soils, precipitation and other environmental factors make a difference? What will it take to sustain forest ecosystems as Earth’s climate changes?
These are just a few of the dozens of questions researchers are hoping to answer through long-term studies underway at a network of forest research plots around the world — now including one near Itasca Biological Station, at the College of Biological Sciences (CBS) field station inside Itasca State Park.
“Our inference about forests and how they're changing really does need to be global, given that so many of these factors are happening at that scale,” says Peter Kennedy, who is principal investigator at the Itasca site. “I'm quite excited to see how Itasca can contribute.”
In 1980, scientists established a protocol for measuring forest composition and how it changes over time, an essential ingredient in the development of the Forest Global Earth Observatories (ForestGEO) network. This involves identifying, tagging and measuring every woody stem one centimeter in diameter or more, then repeating measurements every five years. These measurements create context for a spectrum of specific research projects aimed at everything from understanding differential mortality to exploring the role of the soil microbiome in above-ground growth.
Originally focused on tropical forests, ForestGEO has expanded to temperate and boreal ecosystems as well and now comprises 85 long-term research plots in 29 countries around the world. Department of Plant and Microbial Biology faculty members are leading studies at three of them: Distinguished McKnight University Professor George Weiblen in Papua New Guinea, Assistant Professor Chris Smith-Martin in Puerto Rico and Kennedy in Minnesota.
“I'm proud of the kind of confluence that we have currently with our shared research interests,” Kennedy says. “Even if it means George travels all the way to Papua New Guinea and Christina does the same in Puerto Rico, we're all looking at similar research questions.”
Where temperate and boreal meet
The newest CBS-affiliated site, located in Itasca State Park, joined the network late last year after researchers completed the years-long initial survey of more than 37,000 woody stems over 16 hectares located deep within the station’s mixed temperate-boreal forest. Kennedy first proposed the project in 2019.
“At the time, there was a real gap in the ForestGEO data set in North America,” he says. “There was one site in Alaska that was a conifer-dominated forest that represents what a lot of the northern boreal forest looks like. The one closest to us in Wisconsin was a deciduous-dominated plot. But there really wasn't anything in the middle. And I felt like Itasca” — which includes elements of both types of forest — “had this unique opportunity to bridge that gap.”
Kennedy’s research at the site aims to yield insights into how above-ground community dynamics connect to what’s going on in the microscopic world beneath the surface of the soil. But he’s equally enthusiastic about providing the opportunity for others to pursue answers to their own research questions at the site — especially questions related to how forests can thrive as our planet warms in the decades ahead.
“It’s really meant to be a place where you can come with your questions,” he says. “We have this background data where people can come in, and they don’t have to be experts in tree identification.”
Kennedy is enthusiastic about the contribution the Itasca site will make to the big-picture understanding of forest structure and function.
“While it's neat to know what the composition is now, what I think is ultimately the most interesting is how it will change over time,” he says. “Having Itasca be part of that larger network is something I'm quite excited to see.”
Tracking trees, shaping lives
The Wanang tropical forest research site in Papua New Guinea joined the ForestGEO network under Weiblen’s direction in 2010.
To join ForestGEO, sites must be at least 16 hectares — the equivalent of about 30 football fields. At 50 hectares, with more than 450 tree species and nearly 270,000 individual trees, the Wanang site is also among the largest. Over the years, studies conducted here have focused on subjects as diverse as insect population dynamics, fungal decomposition, avian ecology and medicinal chemistry. The current emphasis is on validating the use of remote sensing as a tool for future research.
“We have a team from Belgium coming over to map the three-dimensional structure of the forest using Lidar, and linking that up with remotely sensed data,” Weiblen says. “This is happening all across the network to open up new ways of measuring what’s happening in forests at larger scales.”
At Wanang, scientists partner with Indigenous people while also providing educational opportunities that enhance capacity for future stewardship of the resource. Native people own and operate the site, and some have gone on to careers in forest management elsewhere.
Plans to introduce agroforestry to boost the local economy while protecting natural resources and preserving Indigenous knowledge of the forest were recently curtailed by changes in U.S. federal funding. Weiblen hopes to find other resources to carry them on, as well as to sustain the forest’s integrity for the long term.
“I would like to see the product of this international collaboration recognized as a national park and sustained into the future,” he says. “Wanang is Papua New Guinea's Itasca. If you want to see what an unlogged forest looks like on Papua New Guinea in a couple of decades, you’ll have to go to Wanang.”
Tolerating drought
Smith-Martin, whose research focus is on how environmental factors affect trees, is carrying out two field studies affiliated with the Itasca ForestGEO site. In addition, she is also leading a research initiative at another tropical ForestGEO site — this one in Puerto Rico. The 16-hectare Luquillo Experimental Forest, established in 1990, comprises 163 species of trees and a total of 165,089 stems at last count.
Smith-Martin began working at the site as a Columbia University postdoctoral fellow, studying how various tree species responded after being devastated by Hurricane Maria in 2017. She and her colleagues discovered that the storm wreaked greater havoc on drought-tolerant species than on drought-resilient ones, leaving the regenerating forest more vulnerable to moisture scarcity than the pre-hurricane ecosystem.
Today her work at the site continues with a focus on how trees distribute water to their tissues and how they respond to stress from heat and water stress. A project currently underway involves building roofs under trees to simulate drought, then observing how their stems and leaves respond to drought.
“Basically, we are getting rid of the rainfall and tracking how these trees are responding with their distribution of starch storage and sap low,” Smith-Martin says. “We’re tracking how stressed these trees are, which ones are doing worse and which ones are doing better.”
Educational angle
All three sites offer abundant opportunities for students and early-career investigators to hone their research skills.
At the Itasca site, CBS Dean Saara DeWalt is using data from the ForestGEO plot to teach about forest ecology for her module during the Nature of Life program at Itasca. Each summer, Nature of Life offers incoming CBS first-year students an opportunity to begin building connections to faculty, staff and peers while exploring biology topics over several days at the station. The ForestGEO connection gives them hands-on experience with world-class research, making their first experiences as a CBS student all the more meaningful.
“During my module, we spend a little time in the classroom talking about what biodiversity is, how you might measure it, and how diversity is measured in forest ecosystems using data from the ForestGEO plot,” DeWalt says. Then students go out to the forest to see how a ForestGEO plot works and make their own observations about the forest. “The students were really engaged. They were impressed that we are part of this global network.”
Kennedy underscores the opportunities the Itasca initiative offers to connect students with research in real time. CBS students have been instrumental in developing census tools for the Itasca site and in doing the actual mapping and measuring.
“A couple of graduate students and an undergraduate were absolutely essential in figuring out how to actually map out the locations of all the trees,” Kennedy says. “We had to do a fair amount of our own coding to make that come together.”
Erica Houser began working for Kennedy at the Itasca plot as an undergraduate and is now continuing work there as a Plant and Microbial Biology graduate student. “ForestGEO was my first-ever fieldwork job,” she says. “It definitely set me on the path to continue studying ecology and working in the field.”
In addition to the education and field research value for CBS students, the Itasca site is serving to pique interest in forest ecology among younger learners as well. Several from Waubun High School, which is located near the Itasca station, have spent a few weeks each summer helping with the tree censuses.
“That’s been a really successful program,” Kennedy says. “It allows graduate students to be mentors. And it allows high school students to see what science actually looks like” — students who might one day find themselves attending the University of Minnesota, majoring in CBS and perhaps even being an investigator at a ForestGEO site. –Mary Hoff