Showy red maples threaten stands of mightiest oaks

Historic shift under way in Pennsylvania and New Jersey

November 20, 2003|By Bob Fernandez | Bob Fernandez,KNIGHT RIDDER/TRIBUNE

PHILADELPHIA -- On hillsides and valleys across the region, scarlet-tinged forests herald the arrival of autumn and signal an epic transformation in the woodlands of the Eastern United States.

The red maple -- a star of the leaf-watching season -- is crowding out the oaks and other hardwood species that have dominated the forests since the end of the Ice Age.

The change may be a boon for foliage watchers, but it spells trouble for the oaks and animals that thrive in oak forests, biologists say.

Loggers and woodworkers prefer oak, too; its dramatic grain, honey color and hardness make it more valuable than red maple.

The historic shift in the forests of Pennsylvania, New Jersey and other Eastern states is caused by several factors:

Deer prefer oak seedlings to maple. Burgeoning deer populations are devouring the next generation of oaks.

Red maples are highly susceptible to fire. A lack of forest fires, both natural and man-made, in the last century has given red maples an unprecedented growth opportunity.

Red maples grow faster than oaks. As roads and other construction create openings, red maples crowd out oaks and other tree species.

Loggers have harvested more oak than maple. Favored as a better furniture wood and commanding a higher price, oak has been cut more extensively.

Once marginal species

Once a marginal species relegated to swamps, the red maple is now the second-largest hardwood tree species in Pennsylvania, measured by volume, behind only the oak. And it is undergoing something of a baby boom. The red maple unleashes a blizzard of whirly-bird seeds and dominates the forest understory with seedlings and smaller-diameter trees.

Of all small trees in Pennsylvania forests that are between 1 and 5 inches in diameter -- a good indicator of the future composition of forests -- there are 1.3 billion red maples and only 366 million oaks, the U.S. Forest Service says.

Of trees that are 5 inches in diameter and larger, there are about equal numbers of red maples and oaks in Pennsylvania -- 523 million red maples and 548 million oaks.

(Though red maples already outnumber oaks in Pennsylvania, oaks remain the dominant tree species because of their larger size. The total wood volume of oaks in Pennsylvania was 7.6 billion cubic feet in 2002, compared with 5.8 billion cubic feet for red maple. This is an indicator of how much wood is available for board, pulp, and other commercial products.

Ecologists warn that there are likely consequences of this "species shift." Oaks, which include the white, northern red, chestnut, black and scarlet types, support wildlife by producing acorns for squirrels and other animals and attracting birds with coarse bark that supports insect life.

`Not an invasion'

"It's not an invasion," said Robert K. Peet, professor of biology at the University of North Carolina at Chapel Hill, who compares the red maple to algae. "It's an explosion. It's a bloom of one species of tree, a red maple."

The red maple has "increased enormously" in the Piedmont area of North Carolina at the expense of oak and hickory trees, he said. Others say the red maple has expanded its range west to the Plains and Upper Midwest.

"I have nothing against the red maple, it's a fine tree," Peet said. "But the trouble is that we are moving closer to a monoculture, with one species dominating the landscape if you value biodiversity, that's being lost. People won't be aware of the transition; it will simply sneak up on them."

Not everyone is convinced this red maple invasion is bad.

More red maples could help the Pennsylvania tourism industry as part of the autumnal draw in the Poconos and central Pennsylvania.

"It has added to our aesthetics," said Dan Devlin, chief of resource planning and information with the Pennsylvania Bureau of Forestry. "We can be viable competition for the New England states," where sugar maples put on a spectacular show.

Marc D. Abrams, professor of forestry at Pennsylvania State University, one of the nation's top experts on red maples, said the species has been advancing for some time, but only in the past 10 or 15 years has it become apparent how damaging it has been to oaks.

"It takes time for things to express themselves in forests because succession in forests takes a long time," Abrams said. "On every level this is turning out to be a negative."

Abrams said the red maple explosion is unprecedented. Oak and hickory trees have been the dominant tree species in the Eastern forests for 10,000 years or so. He believes that was because Native Americans burned forests regularly as a forest- and wildlife-management tool. Later settlers set fires as a result of logging or land clearing.

Both practices controlled the spread of the red maple, which has relatively shallow roots and thin bark and couldn't survive the heat of uncontrolled forest fires, Abrams said. The red maple was limited to swampy and shaded areas, leaving most of the forest to the oaks, which could better withstand fires.

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