ch 12 - tree risk assessment - agrilife
Post on 30-Nov-2021
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Identify TargetStatic, mobile, movable
Occupancy rate: constant-Rare
Assess Target(s)
Target Assessment
Targets and Consequences of Failure
Consequences: function of target value and potential harm.
Four categories: Severe Significant Minor Negligible
Depending on Tree Part Being Assessed, Size Matters
Property Damage and Event Disruption
Site Assessment:Factors to Consider
Previous failures Terrain Wind pattern Soil characteristics Drainage Land disturbances Restricted growth conditions Land-use history
Previous FailuresPrevious failures can indicate high potential for future failures.
All trees pruned in the same manner
Consider Site History: Sidewalks
Site History: Construction
Site History: other root issues
If 1 tree is planted with circling roots, chances are…
Tree Decay• White rot• Brown rot• Soft rot• Sapwood & heartwood rot
White Rot Fungi Primarily decays lignin
Decayed wood appears white after darker colored lignin is removed
Armillaria spp. and Ganoderma spp.
Brown Rot Fungi Conifers primarily
Primarily decays the cellulose, leaving behind stiff lignin
Reduces bending strength
Tree Wood DecayHeartwood Rot Sapwood Rot
Indicators of Decay..
Now that you’ve done a tree assessment… It’s time to mitigate
MitigationTarget Based
Relocation Restricting access Can be temporary
or permanent
Tree Based Prune Cable/brace Removal Modify site
Wildlife Trees
Cabling and Bracing
Residual RiskThere will always be some level of risk remaining after mitigation.
Dependent on owners risk threshold
Remember, you can not make a tree safe, only mitigate the risk.
Target Based MitigationRelocation Exclusion
Conclusion You can not make a tree safe, only
mitigate risk If a tree has failed, it is likely to fail again Risk: likelihood of failure and
consequences of impact
Thank You
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