Date of Award

Spring 2006

Document Type

Restricted Thesis

Terms of Use

© 2006 James M. Kreft. 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

Rachel Merz


Though structural engineers have developed a large dataset on the material properties of wood, these data are based on lumber (small samples of clear trunk wood). Relatively little has been done to examine the properties of living wood in situ. I examined branches of two temperate deciduous species, Sugar Maple (Acer saccharum) and Bur Oak (Quercus macrocarpa) in early spring while the trees were still dormant and in early July, when they were fully leafed out. Using a digital camera and image analysis software, we quantified changes in branch position due to a weight applied to the branch. Using the finite element method, we determined a composite Young's Modulus of Elasticity (E) for each branch, along with the stress distribution for each time point. 8 of 10 branch models indicate that due to complex branch morphologies, peak stress is generally located away from the branch attachment point. In addition, both the modulus of elasticity and the average stress under a constant load were significantly lower in July than in March in the bur oak branches, while no significant differences were seen in the sugar maple branches. This change in modulus of elasticity over time has not been seen in trees before.