2.3.3 Common structural defects
The following section of the manual introduces some common tree defects .
The majority of defects have little or no impact on tree structural integrity , at least as far as a rescue is concerned . A typical mature or veteran tree would have cavities , dead branches , patches of decay , insect colonies , poor branch unions and a range of other defects . Trees like this nevertheless stand for
centuries , surviving repeated storms and huge wind loading .
The defects below are described to assist rescuers with evaluating tree structure as a component of anchor point assessment . In all but the most severe cases , it is not anticipated that the presence of the defects below would prevent tree climbing .
Fungi and decay
The presence of significant decay in any structural , loadbearing component of the tree should always be assessed carefully .
Decay in dead branches that will not be loaded or shaken during a rescue operation is not usually of concern , but decay in the main trunk and stems should be inspected carefully before loading or accessing .
Fungal fruiting bodies may appear as conks or brackets on the trunk and stem of the tree , as ‘ mushrooms ’ next to the base , or even as rust or powder spread on the bark of the decayed area .
Some fungal fruiting bodies are visible throughout the year , whilst others will only be visible for a few weeks . Just because no fruiting bodies are visible it doesn ’ t mean that the tree is free from decay .
Cracks , splits and other structural defects
that point .
Large longitudinal cracks in the structural timber of the tree should be cause for concern . Recent cracks in the trunk may severely compromise the strength of the tree at
In some cases , growth cracks may be found in the bark of the tree . These occur as the stem increases in diameter at a faster rate than normal due to good growing conditions , and do not impact the structural integrity of the tree .
Longitudinal cracks in the stem , or cracks and fractures at branch unions are of particular concern .
When assessing any crack or split it is important to observe whether reaction wood is present around the outer perimeter of the wound . This will appear as rolled , smoother wood that appears different to the adjacent bark .
Reaction wood is formed as the tree responds to injury , and provides supporting strength where the structure is compromised . The presence of reaction wood may be an indicator that the tree has been able to adapt to the injury and compensate for the loss of strength .
Any injury with no evidence of reaction wood may be recent or may be a sign that the tree is failing to adequately respond . Significant cracks or splits with no evidence of reaction wood should be assessed very carefully as the tree part may be prone to failure under comparatively low load .
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