Title: Exploring changes in allometric branch patterns related to variations in branch stiffness and anatomical properties along branches.

Summary: This talk will draw from three inter-related studies describing branch development in terms of two functions; hydraulic and mechanical support. Inferences will be drawn from mechanical properties and anatomical measurements that address how changes in investment at the cellular and tissue level are manifested in overall branch stiffness and form. Allometric relationships have been successfully used to model tree growth and canopy development, yet are not typically utilized by arborists. The allometric log-log relationship between length and radius is an example of one such modeling technique. As a research tool it is useful in describing how growth trends are related to mechanical stability. Yet to the practicing arborist, this theoretical model does not provide a conceptual tool for evaluating individual branch form and stability while in the field. The use of slenderness ratios (branch length / radius) offers a less complicated approach in explaining the same allometric pattern while providing meaningful information to the arborist. Branches are of two types, with different roles: sun branches that place the leaves in position to intercept solar radiation, and structural branches, upon which subordinated sun branches grow. We will explore how allometric patterns shift from a log-log curvilinear pattern to linear as branches transition from the role of flexible sun branches to stiffer structural branches. The allometric shift corresponds to a change from a positive to a negative relationship between slenderness and branch length. It appears that slenderness may provide a practical tool when evaluating branch stability in terms of wind or snow load interception and possibly canopy restoration.

Greg Dahle, BCMA, Graduate Research Assistant, Rutgers University, Department of Ecology, Evolution & Natural Resources, New Brunswick, NJ, United States

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