Free ISA Tree Risk Assessment Questions and Answers — Questions and Answers
Question 1: An arborist performs a Level 2 Basic Tree Risk Assessment on a mature oak in a public park. This level of assessment primarily involves which of the following activities?
- A rapid, drive-by visual survey to identify only trees with imminent failure potential.
- A 360-degree, ground-based visual inspection of the tree's roots, trunk, and crown, potentially using simple tools like a mallet or probe. (Correct answer)
- Advanced diagnostic procedures such as sonic tomography or resistance drilling to quantify internal decay.
- A comprehensive analysis of historical aerial photographs and soil survey maps for the site.
Correct answer: A 360-degree, ground-based visual inspection of the tree's roots, trunk, and crown, potentially using simple tools like a mallet or probe.
A Level 2 Basic Tree Risk Assessment, as defined by the ISA, is a detailed, 360-degree visual inspection from the ground. It goes beyond a simple limited visual check (Level 1) and may involve using basic tools to gather more information, but it does not typically include the advanced diagnostics of a Level 3 assessment.
Question 2: In the context of the ISA Tree Risk Assessment methodology, what are the three principal components that are analyzed to determine the overall risk rating of a tree?
- Tree species, age, and height.
- Soil type, site hydrology, and pest presence.
- Likelihood of failure, likelihood of impacting a target, and the consequences of impact. (Correct answer)
- Pruning history, fertilization schedule, and owner's risk tolerance.
Correct answer: Likelihood of failure, likelihood of impacting a target, and the consequences of impact.
The ISA framework for tree risk assessment is fundamentally based on evaluating three components: the likelihood of a tree or its part failing, the likelihood of that failure impacting a target (people or property), and the severity of the consequences if the target is impacted. These three factors are combined to categorize the overall risk.
Question 3: A TRAQ-qualified arborist is assessing a tree with a significant cavity at its base. The tree is located in a remote, rarely visited section of a large forest preserve with no trails or structures nearby. How does the absence of a target affect the overall risk rating?
- It increases the risk rating because the tree is unmanaged.
- It does not affect the risk rating; the presence of a defect is the only factor.
- It significantly lowers the risk rating, as risk requires a combination of a failing tree part and a target to be impacted. (Correct answer)
- It mandates an immediate Level 3 assessment regardless of other factors.
Correct answer: It significantly lowers the risk rating, as risk requires a combination of a failing tree part and a target to be impacted.
For a significant risk to exist, there must be both a tree with the potential for failure and a target (people, property, or activity) that could be affected. If there is no target, even a tree with a high likelihood of failure will have a very low overall risk rating because the 'consequences' component of the risk equation is negligible.
Question 4: Which of the following is considered a risk mitigation option that does NOT involve pruning or removing the tree?
- Crown reduction.
- Cabling and bracing.
- Moving a picnic table away from the tree's fall zone. (Correct answer)
- Subordination of codominant stems.
Correct answer: Moving a picnic table away from the tree's fall zone.
Risk mitigation involves reducing either the likelihood of failure or the consequences of failure. Moving a target, such as a picnic table or rerouting a path, is a valid mitigation strategy that reduces the consequences without altering the tree itself. The other options are all arboricultural practices performed on the tree to reduce its likelihood of failure.
Question 5: During a site assessment for a tree risk evaluation, an arborist notes the tree is on a steep slope with evidence of recent soil erosion and is fully exposed to prevailing high winds. These observations are most critical for evaluating the:
- Consequences of failure.
- Owner's risk tolerance.
- Likelihood of failure. (Correct answer)
- Tree's historical significance.
Correct answer: Likelihood of failure.
Site factors such as topography (slopes), soil conditions (erosion), and exposure to environmental loads (wind) directly influence the forces acting on a tree and the stability of its root system. These factors are primary inputs for assessing the likelihood that the tree or one of its parts will fail.
Question 6: An arborist needs to perform an advanced assessment to gather more detailed information about the internal structure of a high-value veteran tree after a basic assessment identified a potential area of significant decay. Which of the following methods corresponds to a Level 3 Advanced Assessment?
- A walk-by survey of the tree from a single vantage point.
- A 360-degree visual inspection from the ground using binoculars.
- Using a rubber mallet to sound the trunk for hollows.
- Employing sonic tomography to create a cross-sectional map of wood density. (Correct answer)
Correct answer: Employing sonic tomography to create a cross-sectional map of wood density.
Level 3 Advanced Assessments are used when a Level 2 assessment is inconclusive and more detailed information is needed. They require specialized equipment and expertise. Sonic tomography, which uses sound waves to detect decay and cavities, is a classic example of a Level 3 technique. The other options describe Level 1 or Level 2 assessment activities.
Free ISA Tree Risk Assessment Questions and Answers
An arborist performs a Level 2 Basic Tree Risk Assessment on a mature oak in a public park.
This level of assessment primarily involves which of the following activities?