Date of Award

Spring 2009

Document Type

Restricted Thesis

Terms of Use

© 2009 Nicholas Buttino. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Biology Department

First Advisor

José-Luis Machado


Norway maple (Acer platanoides) populations are rapidly displacing sugar maple (Acer saccharum) stands across the northeastern United States. Earlier studies have suggested that norway maple trees create understories that influence the performance of other seedlings by casting deep shade and emitting allelopathic chemicals. There are more norway maple seedlings, growing under more diverse conditions, than sugar maple seedlings in the Crum Woods of Swarthmore College, PA. This study seeks to elucidate the mechanisms of norway maple invasion through comparing photosynthetic performance and biomass allocation of sugar and norway maple seedlings maintained in conspecific soils but planted in both conspecific and heterospecific canopies. Data from a transplant experiment were compared to observational data of wild seedlings to ascertain the relative importance of canopy structure to natural conditions, which combine canopy and soil environments. Seedling response to neither wild conditions nor isolated canopy conditions can explain the prevalence of norway maple seedlings. However, more pronounced effects in wild conditions suggest that soils are an important mediator of maple seedling performance. Biomass allocation and morphology confirms that wild seedlings behave as shade acclimated plants under norway maple canopies, but cannot explain the prevalence of norway maple seedlings. Photosynthetic performance across environmental conditions at this seedling size class is not a determining mechanism in invasion. Factors such as early seedling survival, photosynthesis performance in saplings, and seed production in mature trees may better describe the mechanisms of norway maple invasion.