E.F. Gilman
Branch-to-stem diameter ratio affects strength of attachment
Journal of Arboriculture 29 (5): 291-294
Strength of branch attachment in Acer rubrum L. was related to the ratio of diameter of the branch relative to the diameter of the stem to which the branch was attached (aspect ratio). Linear correlation coefficients ranged from -0.24 to -0.90 between aspect ratio and load (force) required to separate branches from stems at the branch union. Slopes of the lines describing this relationship increased with increasing branch diameter. This indicated that larger branches required greater force to pull them from the trunk provided they were small compared to the trunk. However, diameter had less on an influence on force required to pull codominant stems apart. Force per unit of branch cross sectional area was related (r2 = 56%) to aspect ratio indicating that a branch of a given size was better secured to the tree if it was attached to a much larger stem than a stem of equal size. Angle of attachment was not related to strength of branch attachment. Codominant stems were far easier to split apart than branches that were small relative to stem size. Codominant stems broken by separating at the union; branches failed by breaking at or near the collar. This information has implications for arborists climbing trees and will help guide development of pruning strategies.
Click here for full article (PDF file)