The Red Maple Paradox What explains the widespread expansion of red maple in eastern forests

O ne of the most dramatic changes that has occurred in forests of eastern North America during the twentieth century is the increase in the dominance of red maple (Acer rubrum L.; Lorimer 1984, Abrams 1992). Red maple has become nearly ubiquitous across sites of widely varying light, moisture, and nutrient availability. This distribution is in stark contrast to the limited distribution of red maple reported in pre-European settlement forests, where it occurred mainly in poorly drained areas. Red maple has increased after a wide range of disturbances and as a late successional species in many forest types. It now dominates the understory and mid-canopy of many oak (Quercus), pine (Pinus), and northern hardwood forests; moreover, it will probably continue to increase in dominance in the overstory during the next century, causing widespread replacement of the historically dominant trees of the forests of the eastern United States. Surprisingly, red maple exhibits rather modest levels of leaf physiological responses (e.g., gas exchange and osmotic adjustment) to various environmental conditions and has leaf structural characteristics and nitrogen levels that are not particularly conducive to a robust leaf physi-