Response of Native and Exotic Maple Seedling Banks to Removal of the Exotic, Invasive Norway Maple (Acer platanoides)

Abstract

WEBB, S. L., T H. PENDERGAST IV, AND M. E. DWYER (Drew University, Biology Department, Madison, NJ 07940.) Response of native and invasive maple seedling banks to removal of the exotic, invasive Norway maple (Acer platanoides). J. Torrey Bot. Soc. 128:000-000. 2001.-Acer platanoides is an exotic, invasive tree in eastern deciduous forests of North America where past research shows it to thrive in the forest interior and to suppress understory diversity. To test the efficacy of restoration strategies and to probe dynamics of this tree's seedling bank, trees and seedlings of Acer platanoides were removed in 1997 from a mixed maple forest carpeted by an even mix of exotic Acer platanoides and native Acer saccharum seedlings. The treatments were removal of trees (height > 1.5 m) and removal of small seedlings (height < 1.5 m), using a crossed design with a total of 80 permanent plots, all sampled before removals and two years later. After two years, removal of Acer platanoides trees had caused an increase in native Acer saccharum seedling densities over those in control areas and had caused a decrease of new Acer platanoides recruitment. Conversely, removal of Acer platanoides seedlings initiated far more new Acer platanoides than Acer saccharum seedlings. The Acer platanoides seedling bank was partially, but not fully, replenished two years after its removal. Although removal of canopy trees appears effective as a restoration tool, other exotic species (especially Lonicera japonica, Alliaria petiolata, and Robinia pseudoacacia) proliferated where tree removals opened the canopy. Restoring the pre-invasion community will thus require future intervention.