The forests of the Eastern United States are turning increasingly red, and the growing brilliance of color signals a historic change in the ecological character of a vast region stretching from the Great Lakes to the Atlantic and from Canada well into the South.

Eastern deciduous woodlands are famous, of course, for their bright fall yellows, oranges and russets. Now red is coming to the fore, and not only in autumn; much of the forest is acquiring a pervasive rosy blush in the spring as well.

The reason is that the soft green springtime hues of hardwoods like oaks and hickories, and the darker greens of northern conifers like pines, are being replaced by the blazing red buds, flowers and fruits of another, more adaptable and aggressive species of native tree: the red maple.

Its fruits, small whirlybirds, rain down profusely in the spring, producing new little trees whose early start gives them a competitive advantage over other hardwood species, which do not drop their seeds until the fall.

These arboreal hard-chargers are taking over the woods. Long viewed as the maple family's poor relations, they were once confined almost exclusively to low, wet areas. Now they have burst out of the swamps and are marching into the uplands in strength.

There they are starting to flaunt a new-found dominance that, if it continues, could signal the downfall of the majestic oaks that have been a mainstay of the deciduous forest for most of the last 10,000 years. A wide range of creatures that adapted to the oak-hickory habitat could suffer as a result.

Larger transformation

The rise of the red maple is part of a larger, continuing transformation of the Eastern forest. The transformation has many causes, all related to humans' impact on the forest ecosystem, but in the case of the maple two stand out.

First, people have suppressed fire. Before European settlement, forest fires routinely killed the thin-barked red maples while oaks and hickories were protected by their thicker bark. Fire also created open spaces ideal for the oaks' light-loving seedlings. Now those spaces are closing up; it so happens that red maple thrives in shade, and its seedlings and saplings are proliferating.

Second, red maples spread like weeds on disturbed ground, and people have disturbed the forest in many ways, not least by chopping it up into a patchwork quilt of disconnected woodland fragments and cleared fields. The maples take enthusiastically to both the forest fragments and the deforested patches between.

In fact, they can grow about anywhere -- in rich soil or poor, on dry land or wet or in between, in open sunlight or deep shade, in young forests or older, mature ones. In contrast, the sugar maple is a prima donna that thrives only in a relatively narrow range of moderately moist soil conditions.

'Super generalist'

The upshot is that the red maple not only can colonize fresh ground easily, it can also grow in the shadow of an established forest. It is a "super generalist" among plants, and its ability to thrive in a wide range of soil conditions, especially, "is a real rarity in the plant world," said Dr. Marc Abrams, a forest ecologist and plant physiologist at Pennsylvania State University in State College.

Abrams has been studying the ecology of the Eastern forest for the last 15 years and has zeroed in on the advance of the red maple.

Liberated from their swamps, red maples have become abundant in the understory -- the carpet of saplings and smaller plants under the canopy -- of many forested stretches in the mid-Atlantic states, the Northeast, the Midwest, the Great Lakes region and in higher Southern elevations like the Appalachians and Piedmont.

When the oaks and other species of older trees die, red maples will replace them, Abrams said. In some spots, that has already happened.

This is all the more remarkable, he said, because the red maple, though versatile, is not especially robust. In the conventional terms of plant physiology, the faster a plant converts sunlight to energy and the better it is at sucking up nutrients, adapting to drought and "breathing" efficiently, the better it can compete with other plants.

The red maple is not particularly good at any of these; it is "toward the low side of average" in such measures, Abrams said. "It's leading me to believe that studies at the physiological level don't tell us very much about the ecological success" of a plant, he said.

The red maple advertises itself partly by the bright, silvery color of its smaller branches and its saplings and by the smooth gray bark of a mature tree's trunk (much like that of a beech). Its leaf shape is classic maple, with three to five serrated lobes attached to a long, slender red stalk.

Seeing red

It usually has something red about it in any season. Its leaves in fall are a brilliant scarlet or crimson. Many of the tree's twigs are red, especially in late summer and fall, as are its buds in winter and its flowers in spring.

From the flowers sprout long, drooping red stalks to which the whirlybird seeds are attached. All of this adds up to a kind of beauty that, along with the tree's ability to grow almost anywhere, has made it a favorite shade tree in the suburbs. It can grow to 100 feet tall or more, with a trunk three or four feet thick, and lives for up to 250 years. Old trees have rougher bark.

Historically, the red maple was found throughout most of the Eastern United States, and was the country's most widely distributed maple. In any given locality, however, it was a minor ecological player, limited mostly to flood plains, wet, low-lying woodlands and swamps.

It has not been considered as valuable a timber tree as other hardwoods, since its wood weighs about the same but is only about three-quarters as strong. Even so, Abrams said, the red maple's increasing abundance is forcing the timber industry to adapt. "Nobody is very happy about it," he said, "but it is replacing much more valuable hardwood species."

Changing forests

Its rise comes in the midst of a wide variety of other changes in the mixed deciduous-evergreen forests of the East, and particularly in the Northeast, where the forest is resurgent in terms of tree abundance.

What exists today is a remnant of a continuous deciduous band that encircled the earth 10 million years ago. Since then the forest has been disturbed almost constantly, first by the comings and goings of ice ages and then, within the last 10,000 years, by the clearings and burnings of Indians.

What greeted the first European arrivals was not unbroken forest, but rather a mosaic of woodland and oak-studded open stretches. Europeans in the Northeast proceeded to cut over all but about 2 percent of the remaining forest to make way for farms in the 18th and 19th centuries. By the 20th century, farmers were moving en masse to better lands in the Midwest, and the Northeastern forest started to regrow.

But as the forest expanded, its composition changed. Disease reduced the elms and chestnuts to ecological insignificance. Many exotic species from abroad, such as the well-known ailanthus, or tree of heaven, along with the bittersweet, the Norway maple and the Japanese honeysuckle, have invaded parts of the forest.