By ERICA HAMLING
Capital News Service
LANSING — The population of Michigan’s state tree has reduced drastically during the past two centuries, and ecologists are trying to repopulate the white pine despite significant hurdles.
At their peak, white pine forests covered about 32 million acres in the northeastern United States. Today, stands of white pine cover only about 17 million acres.
That loss threatens forestry diversity, vital habitats and one of the Great Lakes region’s most beneficial trees, scientists say.
Old-growth white pines form a supercanopy, rising 32 to 50 feet above the general hardwood canopy. Credit: Robert Fahey, Morton Arboretum
It’s a problem not only for the ecosystem but also for the pride of the Great Lakes states, said Joshua Cohen, an ecologist with the an ecologist with the Michigan Natural Features Inventory.
White pines, the tallest tree species in the state, can live 500 years and contribute greatly to the organisms around them, Cohen said, adding that the eventual restoration of the forests would be “an aesthetic value for people.”
Dwindling quantity isn’t the only problem.
“It’s not necessarily overall abundance that’s the issue because there’s a lot of white pine in the landscape,” said Robert Fahey, a forest ecologist with the Morton Arboretum in Illinois. “You should drive up to northern Wisconsin, upper Michigan, Minnesota – there’s a lot of white pines.”
The real problem in Fahey’s view: “It’s not in all the places it once was.”
Fewer white pines mean the landscape is more uniform, causing plant and animals to become less resilient to climate change and invasive pests and pathogens.
A functioning forest relies heavily on old-growth white pines because they are one of the few tree types that form a supercanopy layer in hemlock-hardwood forests, he said. Supercanopies rise about 32 to 50 feet above the general hardwood canopy and support wildlife.
A supercanopy provides nests for several bird species, including the bald eagle, according to Fahey’s research, while brush at the base of the trees provides resting beds for pregnant black bears.
Old-growth white pines were the target of intensive logging in the mid-19th century, not because they provided the best lumber but due to their height and ability to float down rivers to sawmills.
Most white pine were logged from the forest after harvesting. Loggers then started slash fires to pave the way for agriculture or settlement. Some slash fires became so intense that they damaged the soil beyond recovery so new trees couldn’t grow.
More recently white pines have suffered from a germ called Cronartium ribicola, which causes white pine blister rust, Fahey said. Blister rust is most severe in moist conditions during late summer and early fall and has the potential to kill a tree’s branches, weakening it and leading to more severe problems.
And that’s not all there is to worry about, the experts say.
For example, expanding deer herds are eating more seedlings, limiting the capacity for new white pines to grow.
Researchers are unsure whether the white pine can be restored naturally. But Cohen sounds enthusiastic about its future and said patience is the key to natural restoration.
“There’s a lot of responsible forestry going on right now that is supporting the white pines and there’s a lot more we can, but time is one of the critical factors,” Cohen said.
And Fahey said there have been successful cases of active restoration in the Great Lakes region.
Active restoration means physically planting seeds, while passive restoration means no human action is taken except to stop environmental stressors, like grazing. However, active restoration is difficult because the white pine can’t compete well against other species, even in perfect growing conditions.
“Most of the pines that people are planting into these situations either die or are not competitive with the sugar maple or birch that fills these gaps,” said Fahey.
Although planting white pines from seed is occasionally successful, it takes a long time for them to grow at the rate of about eight to 12 inches per year.
Even the possibility that restoration can fully reestablish the white pine has ecologists pushing forward with their research.
“There has been a drastic reduction, but I’m optimistic and think things are on the up and up,” Cohen said.
Erica Hamling writes for Great Lakes Echo.
© 2012, Capital News Service, Michigan State University School of Journalism. Nonmembers cannot reproduce CNS articles without written permission.