ESPERANCE, N.Y. - If a grandmother suddenly started growing, something would be amiss. Now research has found that something similar is happening to the nation's oldest trees.
Clues found in old-growth tree rings from Michigan to Maine show an increasing growth spurt during the last century, possibly from global climate change, according to Neil Pederson, an assistant professor at Eastern Kentucky University.
Normally, trees, like people, slow growth as they age, said Pederson. But ring patterns in oaks, poplars and cedars -- some up to 400 years old -- instead show trees started growing faster in recent decades.
"It is like my grandmother suddenly growing taller and dunking a basketball or playing football," said Pederson. "It's not supposed to happen."
He said it is likely that global warming is behind the change. "The most important factor to limit growth in trees is low winter temperature," he said.
Since starting his research while at the Lamont-Doherty Earth Observatory of Columbia University in New York City, Pederson has collected more than 1,600 tree ring samples. In New York state, some specimens came from Fred Breglia, horticulture and operations director of Landis Arboretum in Esperance.
Winter has been gradually retreating from New York and neighboring states for four decades, according to research by Cameron Wake, a professor at the Climate Change Research Center at the University of New Hampshire.
In the 1970s, there was an average of 87 days with snow on the ground -- two weeks longer than now. Average winter temperatures have climbed 4.5 degrees.
Warmer weather also means more rain to fuel tree growth. Snow now accounts for about 70 percent of winter precipitation, down from 80 percent, according to Wake.
In looking at rings from 230 Atlantic white cedars from Maine to North Carolina, he found trees from New Jersey and north showed accelerated growth rates for the last 80 years, while trees south of that were unchanged.
Breglia agreed with Pederson's view. He said he has also seen similar growth spurt patterns in 600-year-old black gums that he sampled in Saratoga County, N.Y., which is the northernmost edge of the species range.
Pederson's ring research also shows that younger trees are growing faster at the same stage of life compared to their old-growth ancestors, said Pederson. It's hard to say what that might mean for tree longevity, but both researchers say it is possible that sped-up trees might die sooner.Albany Times Union via Star Tribune
