By Joe Rankin
Forests for Maine’s Future writer
Forests aren’t static. They’re dynamic. Since trees colonized the rubble left by the glaciers’ retreat 12,000 years ago, the forest has shifted and reshaped itself many times.
Now the planet is heating up and scientists are trying to anticipate how things will change. Some change is already occurring. Some deciduous tree species in the Midwest are moving westward as climate change alters precipitation patterns. In the Great Basin, limber pines are rapidly climbing the mountains.
Scientists are using computer models to predict the shifting forest landscape. But models have their limitations.
In Maine, scientists at many of the state’s universities are trying to get a handle on how select species might respond by observing the trees themselves.
The three-year study, known as the Common Campus Tree Experiment, is the brainchild of Nicholas Fisichelli, the director of science and education with the Schoodic Institute of Acadia National Park in downeast Maine.
The study involves the Schoodic Institute, four campuses of the state university system and three private colleges and universities. It involves planting 288 trees of 12 species at eight sites across Maine, from Biddeford on the southern coast to Fort Kent at the tip of the state and from Farmington in west central Maine to Machias in far eastern Maine.
“Maine has an amazing climate gradient, from south to north and coastal to inland,” notes Fisichelli. It’s that variability that he hopes will help researchers tease out more conclusions.
The tree species selected for the study are ones that grow in Maine already or reach either the southern or northern portions of their range in the state, or grow just to the South.
They include red maple and white pine, nearly ubiquitous in Maine; balsam fir and white spruce and black cherry; and red oak. Also, red cedar and black and chestnut oaks, which occur in southern Maine. And three that grow to the south of the state: loblolly and Virginia pines and tulip poplar.
While the variability of the state’s climates, from relatively balmy along the southern coast to punishing winters in the far north, was considered a plus, the researchers did everything they could to eliminate or control for other variables.
The sites are all in the open, thus getting the same amount of sun, and adjacent to natural forest. At each site half the seedling trees are planted in existing soil, the other half in a standardized commercial soil to see if that has any effect on survival. All were planted in the same two or three-week period in the spring of 2018.
Over three years their growth and mortality, and the times of bud-break and leaf-out, their phenology, will be tracked.
The study is really “getting at the range limits of tree species,” and trying to isolate climate change as a factor in their range, said Fisichelli. “We don’t understand range limits all that well,” he added. He notes that there are southern species growing on the campuses that are hosting the experimental plots, planted there as ornamentals decades ago. At the University of Maine in Orono there are chestnut oak and magnolia trees, he said. “There’s a lot of fundamental questions about what these trees are responding to.”
Of course climate change comes with a suite of variables as well, not just rising temperatures: precipitation timing and amounts, length of growing season and so on. Climate models generally predict milder winters and longer growing seasons for Maine in the future, with more frequent droughts and slightly more precipitation, but coming in more intense bursts in the spring and fall.
Climate models are “really good at modeling temperature, but not as good at precipitation,” said Fisichelli. And, he notes, things can change as the decades pass. For instance, what happens if humans get serious about cutting greenhouse gases, or deploy some really effective carbon-capture tech. The variables are many and, well, variable.
In April of 2019 forest ecologists Andrew Barton and Jim Shaffer visited their two plots on a hill near Farmington. A brisk wind was scouring the field and snow still lay in patches after a winter marked by heavy snowfall.
They discovered that the native trees were doing pretty well: the black cherries had grown like crazy. The white pines were live and standing up. So were the white spruces. The loblolly and Virginia pines, and the red cedars, however, were beaten down. Some had broken stems.
“Some of our trees apparently didn’t like the snowpack,” Shaffer remarked dryly.
By fall things looked a little better.
“We’ve had pretty good survival overall, and, in fact, some seedlings, such as red cedar, that were struggling, have bounced back. Our big winners so far are cherry and tulip tree, with red maple not too far behind,” said Barton, a biology professor at the University of Maine at Farmington. It will be interesting to see if the tulip trees can sustain their growth, he said.
Shaffer, a Ph.D candidate at the University of Kentucky who is helping Barton oversee the Farmington plots, noted that some of the Virginia and loblolly pines did die, but the ones that made it “put on nice growth this summer.” But another heavy snow winter “might continue to lower their survival.” White pine, spruce and fir did fine during a summer that was never too hot or dry. The red, black and chestnut oaks appeared to be putting their energy into their roots rather than stems.
Fisichelli said it will be a little while before complete reports from all eight sites are available and the numbers get crunched. At the Schoodic site the southern pine species “had somewhat low survival rates” because of snowfall. “They don’t invest in the structure to handle that heavy snow,” Fisichelli said.
Also at Fisichelli’s Schoodic plots, the oaks appeared to be putting their energy into getting established, as did the balsam fir and white pine. Some of the white spruces died, others grew like crazy, he said. Black cherry and red maple had high survival and growth rates.
Fisichelli is looking forward to a complete data set.
The Common Campus Tree Experiment has limitations. It involves growth and survival of seedlings, not mature trees. And the three-year timeframe, with 2020 the last official year of data collection, is pretty limited. “This is one study, one part of a large body of emerging scientific research,” said Fisichelli. “it’s one effort to understand early phases of seedling life.”
He has other studies that dovetail with the CCTE, looking at other phases of tree life. It’s all an attempt to get a handle on what the future forest might look like. For Maine, where the forest products industry is a linchpin of the economy, a heads-up would be crucial.
“Society demands a lot from forests, including lumber and livelihoods, and healthy and productive forests with tree species adapted to the climatic conditions of the future are absolutely necessary to ensure this continued provision of services,” Fisichelli said.
Joe Rankin writes on forestry, nature and sustainability. He lives in New Sharon.