The impact of an exotic invasive tree species, Acer platanoides, on the community and ecosystem dynamics of an eastern deciduous forest

Biological invasion is an important component of global change. Changes in diversity and ecosystem function associated with invasions are often implied to result from competitive suppression, but this implication is rarely explicitly tested and the mechanisms are poorly understood. This dissertation research addressed these issues using an exotic invasive tree species Norway maple, Acer platanoides, in comparison with its native congener red maple, A. rubrum.; There are four coherent components in this study. A spatially explicit descriptive study was first conducted to supply and support testable hypotheses. Inferences were made on the population dynamics of Norway maple and the dynamics of native species over time and space under the influence of Norway maple invasion. The second component was two manipulative field experiments conducted in Norway maple heavily infested areas and their adjacent natural woodlands. The purpose was to test the possibility of competitive displacement of red maple by Norway maple. The third component was a manipulative asymmetric competition experiment between maple adults and transplanted seedlings of 8 common species from various functional types. The purpose was to assess the impact of Norway maple invasion on the community, and to test the mechanisms of Norway maple's putative competitive superiority. It also tested the idea of functional group and species indigenousness (native vs. exotic) as meaningful units of community component. The fourth component was on the ecosystem dynamics undergoing in the last experiment. The purpose was to assess the impact of Norway maple invasion on the ecosystem processes, and test an alternative mechanism of the impact of Norway maple on the system other than competitive superiority.; This research is one of the first few experimental studies that explicitly test a unifying hypothesis on the impact of invasive species at multiple organizational levels. The results of this study will enrich our conceptual understanding on the mechanism of invasion effects, form a basis for exploring the effects of invasive species and offer much needed information for resource management. It will also contribute to our understanding on the fundamental role of single novel species on shaping its ecological environment when interacting with the existing systems.