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Trees (Damages)
The two major sources of tree damage are biotic (from living sources) and abiotic (from non-living sources). Biotic sources would include insects which might bore into the tree, deer which might rub bark off the trunk, or fungi, which might attach themselves to the tree.
Abiotic sources include lightning, vehicles impacts, and construction activities. Construction activities can involve a number of damage sources, including grade changes that prevent aeration to roots, spills involving toxic chemicals such as cement or petroleum products, or severing of branches or roots.
Both damage sources can result in trees becoming dangerous, and the term "hazard trees" is commonly used by arborists, and industry groups such as power line operators. Hazard trees are trees which due to disease or other factors are more susceptible to falling during windstorms, or having parts of the tree fall.
The process of evaluating the danger a tree presents is based on a process called the Quantified Tree Risk Assessment.
Assessment as to labeling a tree a hazard tree can be based on a field examination. Assessment as a result of construction activities that will damage a tree is based on three factors; severity, extent and duration. Severity relates usually to the degree of intrusion into the TPZ and resultant root loss. Extent is frequently a percentage of a factor such as canopy, roots or bark, and duration is normally based on time. Root severing is considered permanent in time.
Trees are similar to people. Both can withstand massive amounts of some types of damage and survive, but even small amounts of certain types of trauma can result in death. Arborists are very aware that established trees will not tolerate any appreciable disturbance of the root system. However, lay people and construction professionals are seldom cognizant of how easily a tree can be killed.
One reason for confusion about tree damage from construction involves the dormancy of trees during winter. Another factor is that trees may not show symptoms of damage until 24-months or longer after damage has occurred. For that reason, persons uneducated in arboriculture science may not correlate the actual cause and resultant effect.
Various organizations, such as the International Society of Arboriculture, the British Standards Institute and the National Arborist Association (about 2007 renamed the Tree Industry Association), have long recognized the importance of construction activities that impact tree health. The impacts are important because they can result in monetary losses due to tree damage and resultant remediation or replacement costs, as well as violation of government ordinances or community or subdivision restrictions.
As a result, protocols for tree management prior to, during and after construction activities are well established, tested and refined. These basic steps are involved:
Review of the construction plans
Development of the related tree inventory
Application of standard construction tree management protocols
Assessment of potential for expected tree damages
Development of a tree protection plan (providing for pre-, concurrent, and post construction damage prevention and remediation steps)
Development of a tree protection plan
Development of a remediation plan
Implementation of tree protection zones (TPZ)
Assessment of construction tree damage, post-construction
Implementation of the remediation plan
International standards are uniform in analyzing damage potential and sizing TPZs (tree protection zones) to minimize damage. For mature to fully mature trees, the accepted TPZ comprises a 1.5-foot set-off for every 1-inch diameter of trunk. That means for a 10-inch tree, the TPZ would extend 15-feet in all directions from the base of the trunk at ground level.
For young/small trees with minimal crowns (and trunks less than 4-inches in diameter) a TPZ equal to 1-foot for every inch of trunk diameter may suffice. That means for a 3-inch tree, the TPZ would extend 3-feet in all directions from the base of the trunk at ground level. Detailed information on TPZs and related topics is available at minimal cost from organizations like the International Society for Arboriculture.
ABD606 01/11/2009 15:47
Trees (Damages)The two major sources of tree damage are biotic (from living sources) and abiotic (from non-living sources). Biotic sources would include insects which might bore into the tree, deer which might rub bark off the trunk, or fungi, which might attach themselves to the tree.
Abiotic sources include lightning, vehicles impacts, and construction activities. Construction activities can involve a number of damage sources, including grade changes that prevent aeration to roots, spills involving toxic chemicals such as cement or petroleum products, or severing of branches or roots.
Both damage sources can result in trees becoming dangerous, and the term "hazard trees" is commonly used by arborists, and industry groups such as power line operators. Hazard trees are trees which due to disease or other factors are more susceptible to falling during windstorms, or having parts of the tree fall.
The process of evaluating the danger a tree presents is based on a process called the Quantified Tree Risk Assessment.
Assessment as to labeling a tree a hazard tree can be based on a field examination. Assessment as a result of construction activities that will damage a tree is based on three factors; severity, extent and duration. Severity relates usually to the degree of intrusion into the TPZ and resultant root loss. Extent is frequently a percentage of a factor such as canopy, roots or bark, and duration is normally based on time. Root severing is considered permanent in time.
Trees are similar to people. Both can withstand massive amounts of some types of damage and survive, but even small amounts of certain types of trauma can result in death. Arborists are very aware that established trees will not tolerate any appreciable disturbance of the root system. However, lay people and construction professionals are seldom cognizant of how easily a tree can be killed.
One reason for confusion about tree damage from construction involves the dormancy of trees during winter. Another factor is that trees may not show symptoms of damage until 24-months or longer after damage has occurred. For that reason, persons uneducated in arboriculture science may not correlate the actual cause and resultant effect.
Various organizations, such as the International Society of Arboriculture, the British Standards Institute and the National Arborist Association (about 2007 renamed the Tree Industry Association), have long recognized the importance of construction activities that impact tree health. The impacts are important because they can result in monetary losses due to tree damage and resultant remediation or replacement costs, as well as violation of government ordinances or community or subdivision restrictions.
As a result, protocols for tree management prior to, during and after construction activities are well established, tested and refined. These basic steps are involved:
Review of the construction plans
Development of the related tree inventory
Application of standard construction tree management protocols
Assessment of potential for expected tree damages
Development of a tree protection plan (providing for pre-, concurrent, and post construction damage prevention and remediation steps)
Development of a tree protection plan
Development of a remediation plan
Implementation of tree protection zones (TPZ)
Assessment of construction tree damage, post-construction
Implementation of the remediation plan
International standards are uniform in analyzing damage potential and sizing TPZs (tree protection zones) to minimize damage. For mature to fully mature trees, the accepted TPZ comprises a 1.5-foot set-off for every 1-inch diameter of trunk. That means for a 10-inch tree, the TPZ would extend 15-feet in all directions from the base of the trunk at ground level.
For young/small trees with minimal crowns (and trunks less than 4-inches in diameter) a TPZ equal to 1-foot for every inch of trunk diameter may suffice. That means for a 3-inch tree, the TPZ would extend 3-feet in all directions from the base of the trunk at ground level. Detailed information on TPZs and related topics is available at minimal cost from organizations like the International Society for Arboriculture.