The ecological effects of Norway maple (Acer platanoides ) on local plant diversity

As ecosystem engineers, trees are important for structuring forest ecosystems and shaping local patterns of biodiversity within the understory. Norway maple (Acer platanoides) is an invasive tree species in Southern Ontario that is responsible for limiting native tree species growth and potentially facilitating further invasive species spread throughout forest communities in North America. The extent of invasion by this species in Ontario is not known. Both spatial patterns and species composition were investigated at multiple scales and lifestages to determine the impact of A. platanoides on local biodiversity and the extent of invasion in the region. Furthermore, diversity resistance hypothesis was investigated as a potential mechanism of inhibiting woody invasive species establishment and invasion into forests. Diversity of tree genera did not seem to provide any resistance to invasion of A. platanoides as spatial patterns and densities mirrored those of native species and A. platanoides in its native range. Furthermore, A. platanoides demonstrated the ability to increase its populations size at a greater rate than native congeners, potentially replacing native species in the canopy over time. Surveys of understory species composition and overstory impacts showed that though understory diversity had little impact on seedling establishment of either native or invasive Acer species. A. platanoides did, however, seem to facilitate conspecific seedlings and invasive understory species beneath its canopy.