Lightning damage
Risks
Recent or severe lightning damage may severely compromise the strength of the tree ’ s structure .
Lightning damage will vary significantly depending on the intensity of the lightning strike , the moisture content of the tree species and the path the lightning follows to the ground .
Severe lightning strikes in trees with moist tissues may travel down the cambium or through internal tissues , shattering wood in the branches and trunk . These types of lightning strike are often fatal and may severely compromise the structure of the tree . In trees with drier internal timber , the current may follow water on the outside of the bark . This type of strike may still remove a strip of bark , but in healthy trees the exposed timber will be covered by woundwood and the tree will recover .
Older lightning damage , or lightning damage that has followed the bark and not damaged the timber , may be of less concern .
Control measures
Investigate extent of damage ( probe ).
Conduct pull tests to simulate the working loads which will be placed on the tree .
Strap the split in the tree before access .
Mechanical damage
Mechanical damage occurs where human or machine activity has impacted on the tree .
Look for evidence of structural root damage , such as recently disturbed soil or new constructions . Structural root damage may severely compromise tree stability .
Mechanical damage may also occur above-ground , where machinery has impacted the trunk or structural branches .
Risks
Where structural roots of the tree have been compromised , the usual ‘ safety factor ’ of the tree having been through repeated wind loads will not be present .
The tree may fail at ground level under low and unpredictable loads .
Control measures
Investigate extent of damage .
Conduct pull tests to simulate the working loads which will be placed on the tree .
Guy or brace tree before access .
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