CORINTH — Three researchers from Dartmouth College and the University of Vermont wound their way up a logging road at the Clement Woodlot in Corinth on Friday morning. They carried multicolored wire, laptops and tools; they’d come to the remote Dartmouth-owned forest to turn on sensors they had installed earlier in August.
The calcium-rich soil underfoot had enabled the ash trees around them to flourish. The tall trees demand ample nutrients. Dave Lutz, a Dartmouth environmental scientist, said ash trees make up roughly 40% of the canopy, an unusually high percentage for Vermont.
But the emerald ash borer is a green, jewel-like beetle that preys on ash trees, and after decimating ash populations in 34 states, it is progressing through Vermont and closer to the 509-acre woodland in Corinth. Lutz said that they were walking through a healthy ash forest, which is increasingly rare in North America.
A medley of researchers and foresters have worked together to monitor the Clement Woodlot, with the help of Kevin Evans, Dartmouth College’s forestry director. Their goals are twofold: to record the threatened ecosystem with the ash — a genus of tree that has long been an integral element of northern hardwood forests — and to develop the best strategies to manage a forest to be resilient.
Lutz said the sensors that he was wiring with Emma Hazard, an undergraduate research assistant, and Karin Rand, a UVM research technician, were a “last shot” at memorializing an ash forest.
“I know from history that whenever we see a big invasive something come through — chestnut blight, elm — this kind of ecosystem vanishes. It’s gone; it never returns,” Lutz said. “I wanted to monitor and capture the particular unique ecosystem that will never exist again. We have a couple of years before it all changes.”
No other tree will be able to perfectly replace the ash tree in the forest, said Tony D’Amato, who directs the UVM forestry program and is leading the experimental treatments in the Clement Woodlot. Their uniquely nutritious leaves fall to the forest floor, nourishing the animals living in the understory and altering soil. The large cavities that form in their trunks become homes for nesters, and their tall, abundant crowns provide cover for a wide range of forest animals.
But the emerald ash borer is nearby. It was found in central Vermont in 2018, and is now just 5 miles away, having yet to “jump” a mountain ridge. Once in an ash forest, the beetles can prove deadly, working their way beneath the bark and chewing around the circumference, essentially girdling the tree and restricting the flow of water in the trunk.
Recording a threatened ecosystem The sensors that Lutz, Hazard and Rand wired and turned on last Friday will capture a wide range of data, ranging from air temperature, the water available to trees and plants, solar radiation, snow depth and the amount of carbon released from the soil into the air.
These sensors will connect to nine stations that dot the forest. Each station has a solar panel, a battery and a computer mounted in a protective wooden box. Lutz and several of his students built these adaptable, “do-it-yourself” stations in his garage with support of funding from organizations including the National Science Foundation (which is funding similar sensors in other New England forests) and the Neukom Institute for Computational Science at Dartmouth College.
Hazard programmed the computers to record data from the sensors every 15 minutes.
“Long story short, the data is mountainous,” Lutz said. “This sort of data collection does not exist. You don’t have this except in well-funded sites with line power out, which biases our knowledge towards individual cases.”
The abundance of data will allow for wide-ranging questions, from ash-specific queries to more generalized ones about how forests function — how do habitats shift with climate change? What are the differences between the temperature systems of the forest and an open field?
For Lutz, however, the project is about more than the science. He described how chestnut blight wiped out one of the most abundant tree species along the East Coast early in the 20th century.
“They’re gone. They’re invisible,” Lutz said. “We have no documented evidence of what the soil was like, what birds, what wildlife — we’ll never return to that, ever. It’s gone.
“These ash forests are the same. I want to document this forever. We have a window. Let’s take every measurement we can. … This is our last chance in the history of humans to remember this.”
Managing a resilient forestThe sensors will also capture how different forestry management strategies may alleviate or exacerbate the impact of the emerald ash borer on the wider ecosytem. Working with state agencies and forestry groups, D’Amato has overseen three forestry strategies, or “treatments,” at the Corinth property. The sensors will capture the differences in real time.
D’Amato and his team divided part of the woodlot into 12 plots of about 15 acres apiece. They will leave three untouched so that they can serve as a control group
In three other plots, they have worked with Allard Lumber Co. to aggressively cut out the ash tree. They are mimicking a common path that landowners take as the emerald ash encroaches. The wood is of high value before it is infected, and once infected, the wood becomes brittle and dangerous to remove, he explained.
“The human response is often more impactful than the insect itself,” D’Amato said. If allowed to rot in the forest, the dying ash benefits the wider forest ecosystem in part because it provides wildlife with habitats and nutrients.
In the remaining three plots, D’Amato and his colleagues are implementing “resilience treatments” that both “give future options for the white ash,” and prepare the forest to absorb future shocks, including the next invasive that will attack a native tree species.
D’Amato said that leaving female ash trees in the forest had to be a priority. There is only one female ash for every seven males. They bear the seeds, and with them, the possibility of reproduction. He also recommends leaving the ash trees with the most robust crowns, since a healthier tree has a better chance of surviving the beetle.
D’Amato prioritizes managing the entire forest, not just one species. Colored flags dotted the plot where Lutz, Hazard and Rand were wiring the sensors. Each color represented another species and a step toward an increasingly diversified forest better able to withstand an invasive that targets one kind of tree.
Matt Ayres, a Dartmouth biologist, studies insects and conducts research in the Hubbard Park Experimental Forest, in New Hampshire’s White Mountains, where the emerald ash borer has already been found. He has little hope for the ash, although he said its demise may add urgency to proposed policies to limit the imported wooden pallets and plants that carry in invasive insects.
“All we can really do is watch,” he said. Chemical treatments are expensive and labor-intensive to apply to a forest, and tinkering with the genus’ genetics would be like putting “a man on the moon.”
D’Amato describes himself as a realist, and he said he knows of many examples of trees being killed en masse. Yet he has not despaired about the ash. After the emerald ash borer progressed through Michigan — the first hotspot of the U.S. invasion — most ash trees died. But researchers at Michigan State University found some white ash survived.
“I do have hope,” he said. “And there’s evidence for hope.”
Claire Potter is a Report for America corps member. She can be reached at cpotter@vnews.com or 603-727- 3242.