Bifurcation types tested, research related to each type, numbers of replicates for each type, year of modification, and associated growing seasons prior to mechanical testing.
| Name of bifurcation type | Description | Factor assessed | No. of replicates | Year of artificial modification | Growing seasons between modification and testing |
|---|---|---|---|---|---|
| Bark-included | Naturally-occurring bifurcations with bark found to be incorporated within the apex of the bifurcation (Figure 6). | Effect of bark obstructing the normal anatomical connection at a bifurcation. | 70 | Not modified | N/A |
| Braced | Normally-formed bifurcations modified by the conjoining of the two branches above the bifurcation with a 3 mm steel rod fitted through both branches, with a 7 mm washer and nut fitted at each end of the rod. These were left to grow within the tree’s crown for three years prior to testing (Figure 1A). | Effect upon remodeling by completely preventing mechanical perturbation at the apex of the bifurcation. | 25 | 2011 | 3 |
| Newly drilled | Normally-formed bifurcations drilled at their apices using a drill-size as defined in Table 1, immediately prior to mechanical testing (Figure 1B). | Effect of removing centrally placed interlocking xylem at the apex of the bifurcation. | 60 | 2015 | 0 |
| Normally formed | Naturally occurring bifurcations with no flaws observed in morphology. | To act as a benchmark for all other modifications. | 60 | Not modified | N/A |
| Pre-drilled | Normally-formed bifurcations modified by drilling at their apices using a drill-size as defined in Table 1, and left to grow within the tree’s crown for two or four years prior to testing (Figure 1B). | Effect of remodeling after the removal of the centrally placed interlocking xylem at the apex of the bifurcation. | 50 | 2010 | 2 and 4 |
| Pre-split | Normally-formed bifurcations modified by carefully splitting the apex by hand, by bending away from each other the two arising branches. These were left to grow within the tree’s crown for three years prior to testing (Figure 1C). | Effect of remodeling after the cracking of the top part of the bifurcation. | 25 | 2011 | 3 |