Urban Forests and Arboriculture

Factors That Influence Branch Union Strength

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To improve structure within a tree’s crown and reduce risk of union failure, arborists must be able to identify branch unions with inherent weaknesses. Once properly identified, arborists can remove or subordinate branches to eliminate or alleviate defects. The objective of this study was to identify potential visual indicators of branch union weakness and to assess the impact of the weakness on  branch union failure stress in Acer rubrum and A. platanoides

Results indicate that the absence of a branch collar (<0.0001), the  absence of a single BBR (0.0040), and the presence of a V-shaped branch union (0.0002) were all strong predictors of branch unions with large aspect ratios,  a condition that decreased breaking stress in both species tested (max P-values 0.0002).



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