ISA ARBORIST CERTIFICATION;TREE RISK
ANSWERS|LATEST !!!!2026|GRADED A+| (EXAM
Failure potential - ANSWER is the likelihood that an entire tree, or part of a tree, will
break and fall. In evaluating a tree's failure potential, the arborist must consider a number of
factors, including the species, growth habit, quality of branch attachments, condition of the
root system, lean, and the history of the tree and site.
The arborist should consider the history of the site and how it affects tree stability. Following
are some of the factors that should be noted: - ANSWER - construction, grade
changes, and trenching within the root zone
- removal of adjacent trees that previously served as a wind buffer
- replacement of sidewalks and root loss (root pruning)
- failure of nearby trees caused by root disease
Failure Targets - ANSWER Targets are people and/or property that could be
damaged or injured if the tree failed. If there is no target, there is no risk, because if the tree
fails, no damage would occur.
tree risk management - ANSWER component of tree risk assessment. All trees have
the potential to fail. As trees grow larger and mature, and assuming there are targets
present, the degree of risk increases.
Structural defects - ANSWER that can lead to failure are not always visible, especially
those inside the tree or beneath the ground, and the forces of nature are unpredictable.
1
, It takes a trained eye to discern the difference between a minor defect and significant
weaknesses that are likely to result in tree failure. The arborist must be familiar with: -
ANSWER tree species
what is normal and abnormal growth
structure and form
species' primary failure patterns
Leaning Trees - ANSWER Many trees develop lean as they grow into open light areas
and away from larger trees or structures. In these cases, the trees develop reaction wood to
support the tree in a leaning position. Such trees are stable in normal conditions; however,
they often are more likely to fail when loaded with rain, snow, or wind than upright trees.
Taper - ANSWER having a diameter that gradually decreases from the base to the
tip, are stronger than stems with poor taper
Taper develops in response to - ANSWER movement in wind and is enhanced by
presence of lateral branches low on the stem. Trees growing in the open tend to have good
taper, while those growing in stands have poor taper.
trunk flare - ANSWER Lack of a trunk flare, discolored or loose bark, and
indentations created by circling roots, wounds, and seams are all defect indicators. It may be
necessary to dig away mulch and soil to find and inspect the root collar.
When performing a risk assessment, an indication of a significant defect is -
ANSWER codominant stems and included bark
Dead Branches - ANSWER Dead branches within the canopy of a tree are probably
most obvious sign of risk.
2
ANSWERS|LATEST !!!!2026|GRADED A+| (EXAM
Failure potential - ANSWER is the likelihood that an entire tree, or part of a tree, will
break and fall. In evaluating a tree's failure potential, the arborist must consider a number of
factors, including the species, growth habit, quality of branch attachments, condition of the
root system, lean, and the history of the tree and site.
The arborist should consider the history of the site and how it affects tree stability. Following
are some of the factors that should be noted: - ANSWER - construction, grade
changes, and trenching within the root zone
- removal of adjacent trees that previously served as a wind buffer
- replacement of sidewalks and root loss (root pruning)
- failure of nearby trees caused by root disease
Failure Targets - ANSWER Targets are people and/or property that could be
damaged or injured if the tree failed. If there is no target, there is no risk, because if the tree
fails, no damage would occur.
tree risk management - ANSWER component of tree risk assessment. All trees have
the potential to fail. As trees grow larger and mature, and assuming there are targets
present, the degree of risk increases.
Structural defects - ANSWER that can lead to failure are not always visible, especially
those inside the tree or beneath the ground, and the forces of nature are unpredictable.
1
, It takes a trained eye to discern the difference between a minor defect and significant
weaknesses that are likely to result in tree failure. The arborist must be familiar with: -
ANSWER tree species
what is normal and abnormal growth
structure and form
species' primary failure patterns
Leaning Trees - ANSWER Many trees develop lean as they grow into open light areas
and away from larger trees or structures. In these cases, the trees develop reaction wood to
support the tree in a leaning position. Such trees are stable in normal conditions; however,
they often are more likely to fail when loaded with rain, snow, or wind than upright trees.
Taper - ANSWER having a diameter that gradually decreases from the base to the
tip, are stronger than stems with poor taper
Taper develops in response to - ANSWER movement in wind and is enhanced by
presence of lateral branches low on the stem. Trees growing in the open tend to have good
taper, while those growing in stands have poor taper.
trunk flare - ANSWER Lack of a trunk flare, discolored or loose bark, and
indentations created by circling roots, wounds, and seams are all defect indicators. It may be
necessary to dig away mulch and soil to find and inspect the root collar.
When performing a risk assessment, an indication of a significant defect is -
ANSWER codominant stems and included bark
Dead Branches - ANSWER Dead branches within the canopy of a tree are probably
most obvious sign of risk.
2
