Invasive Plants of Canadian Woodlands – Scientific Challenges

About 28% of the Canadian flora are non-indigenous species (NIS). What is their impact on woodlands? While some spectacular introduced invasive plants in North America function as keystone species, altering ecosystem structure and function, most NIS simply increase the species richness of an area. We have found that some so-called invasive plant species are likely not having a major impact on plant communities, and that ecosystem and landscape-level disturbances are of much greater significance in determining plant community composition. Predicting which introduced species may become a problem remains a challenge, although, in keeping with the literature, we have found that one problem species, Japanese Barberry, was deliberately introduced as a garden plant and then escaped. Additionally, we also found that human-induced disturbance is associated with the spread of non-native plants.