Tree Risk Assessment Flashcards

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?

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.

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?

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.

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?

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.

Which of the following is considered a risk mitigation option that does NOT involve pruning or removing the tree?

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.

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:

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.

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?

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.