"Liberated from their swamp ghettos, red maples have become abundant in the understory -- the carpet of saplings and smaller plants under the canopy -- of many forested stretches in the Middle 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, Dr. 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, Dr. 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."