Investigation of allelopathy in an invasive introduced tree species, Norway maple (Acer platanoides L.)

Plants and their propagules have been deliberately and accidentally transported around the world by human activity since human populations began to migrate. Occasionally an introduced species will behave invasively in a new region and replace native species, possibly to the point of local extirpation or even extinction. Several mechanisms for successful invasion have been identified. Among them is allelopathy, which occurs when a plant interferes with the growth of its neighbors via chemicals. A plant that is not apparently allelopathic in its home range may become so in a new region.; A. platanoides is an invasive introduced tree in many parts of the United States, including Pennsylvania and New Jersey. There are few other plants growing under its canopy and very few of them are native species. In this study, I looked at species richness and diversity of native and introduced species as a function of A. platanoides influence and found that native species richness diminished in response to increasing A. platanoides influence, while introduced species were unaffected.; I also looked for signs of allelopathy occurring in A. platanoides at three different life stages using three native shade tolerant species as phytometers. The experiments took place in a forest, a mesocosm and a greenhouse. The native species were grown in close proximity to A. platanoides with and without activated carbon in the soil. Activated carbon was used to neutralize potential allelochemicals by adsorption. The life stages of A. platanoides studied were seedling, sapling and mature. The experiment took place during a summer that had unusually high temperatures and little rainfall. This stress has been shown to enhance allelopathic effects in some cases. Despite the wide range of experimental conditions, no evidence of growth interference by allelopathy on the part of A. platanoides was detected. Though these experiments do not completely eliminate the possibility of allelopathy occurring, they do demonstrate that any allelopathic effect on plant growth is probably very small.