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Tree fork
A tree fork is a bifurcation in the trunk of a tree giving rise to two roughly equal diameter branches. These forks are a common feature of tree crowns. The wood grain orientation at the top of a tree fork is such that wood cells interlock to provide sufficient mechanical support. A common malformation of a tree fork is where bark has formed within the join and these bark-included junctions have a heightened risk of failure.
==Definition of a tree fork==
In arboriculture, junctions in the crown structure of trees are frequently categorised as either branch-to-stem attachments or co-dominant stems.〔Smiley, E. T. (2003) Does included bark reduce the strength of co-dominant stems?; ''Journal of Arboriculture'' 29(2) pp. 104-106〕 Co-dominant stems are where the two or more arising branches emerging from the junction are of near equal diameter and this type of junction in a tree is often referred to in layman's terms as 'a tree fork'.〔Harris, R.W. Clark, J. R. and Matheny, N. P. (1999) ''Arboriculture: Integrated Management of Landscape Trees, Shrubs and Vines''; 3rd Ed.; Prentice Hall〕〔Lonsdale, D.(2000) ''Hazards from Trees: A general guide''; Forestry Commission Practice Guide; TSO〕
There is actually no hard botanical division between these two forms of tree junction: they are topologically equivalent, and from their external appearance it is only a matter of the diameter ratio between the branches that are conjoined that separates a tree fork from being a branch-to-stem junction.〔Slater, D. and Harbinson, C. J. (2010) Towards a new model for branch attachment; ''Arboricultural Journal'' 33 (2) 95-105〕
However, when a small branch joins to a tree trunk there is a knot that can be found to be embedded into the trunk of the tree, which was the initial base of the smaller branch. This is not the case in tree forks, as each branch is roughly equal in size and no substantial tissues from either branch is embedded into the other, so there is no reinforcing knot to supply the mechanical strength to the junction that will be needed to hold the branches aloft.〔Slater, D. and Harbinson, C. J. (2010) Towards a new model for branch attachment; ''Arboricultural Journal'' 33 (2) 95-105〕
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