Above- and belowground interactions on growth between the invasive Norway maple (Acer platanoides L) and native Red maple (Acer rubrum L)

Invasive species continue to change the plant communities that have historically been components of forests in the eastern United States.  The successful spread of invasive plants has generally been attributed to population and community mechanisms (e.g., allelopathy, soil alteration, greater growth rates) and human actions (e.g., urbanization, globalization).  In this study, we investigated some of the above- and below-ground interactions between the invasive Norway maple (Acer platanoides L.) and its native congener, red maple (Acer rubrum L.).  A greenhouse experiment used Acer seedlings collected from a post-agricultural, mature suburban forest in central New Jersey (USA).  Two different forest soil types from this forest (soil beneath a monospecific Norway maple canopy; soil beneath a mixed oak-maple-elm canopy) were used to test whether soil from below an invasive canopy would affect biomass (leaf, stem, and root) of each Acer species differently from soil from the native community.  We also tested competition between these two species at the root, shoot, and whole-plant levels, through the use of pot barriers in a greenhouse setting.  We found highly significant affects of soil from the Norway maple stand, reducing leaf, stem and root biomass of red maple seedlings.  However, the Norway maple seedlings showed no significantly different biomass values between the two soil types.  This study adds to our understanding of how invasive species are impacting native plant communities and informs restoration practitioners of cryptic ecosystem impacts of invasive tree species, as realistic goals for ecological restoration in forests with an invasive species history are developed.