ISA Tree Risk Assessment Questions and Answers

Question 1

An arborist performs a detailed, 360-degree visual inspection of a tree from the ground, using a mallet to sound the trunk and a probe to investigate a potential cavity. According to ISA standards, this type of on-site evaluation is best described as which level of assessment?

Accepted Answer

Level 2 (Basic)

Answer

A Level 2 (Basic) Tree Risk Assessment involves a comprehensive, 360-degree visual inspection of the tree and its site from the ground. It often includes the use of simple tools like mallets, probes, and binoculars. A Level 1 assessment is a more limited, 'walk-by' or 'drive-by' inspection, while a Level 3 assessment involves advanced diagnostic tools and techniques like sonic tomography or aerial inspection.

Question 2

In the ISA Tree Risk Assessment Qualification (TRAQ) methodology, the final risk rating is determined by combining three primary components. Which of the following correctly identifies these components?

Accepted Answer

Likelihood of failure, likelihood of impacting a target, and consequences of failure

Answer

The ISA TRAQ methodology defines risk as the combination of the likelihood of a tree or part failing, the likelihood of that part impacting a target, and the severity of the consequences if it does. The other options list important factors that are considered during an assessment, but they are not the three core components of the final risk calculation itself.

Question 3

An arborist identifies a mature tree with a significant structural defect. However, the tree is located in a remote, fenced-off wildlife preserve with no trails or public access. Despite the defect, the arborist assigns a low overall risk rating. What is the most likely justification for this low rating?

Accepted Answer

The likelihood of the tree or its parts impacting a target is negligible

Answer

In tree risk assessment, risk only exists when a tree failure has the potential to impact a target (people, property, or activity). In a location with no targets, even a tree with a high likelihood of failure will have a low overall risk rating because the 'likelihood of impacting a target' and 'consequences' components of the risk equation are negligible.

Question 4

When assessing codominant stems, the presence of included bark in the union is a significant concern primarily because it:

Accepted Answer

Creates a weak attachment by preventing strong, interlocking wood tissue from forming.

Answer

Included bark is bark that becomes embedded in the junction between two stems, preventing the formation of a normal, strong branch union. Instead of being connected by continuous, overlapping wood grain, the stems are pushed apart as they grow, creating a weak point that is significantly more prone to failure under load.

Question 5

A Level 2 assessment of a high-value historic oak reveals suspected internal decay, but the extent cannot be determined visually. To gather more detailed, quantitative data about the amount of solid wood remaining, which of the following would be the most appropriate next step?

Accepted Answer

Proceed with a Level 3 assessment using sonic tomography.

Answer

When a Level 2 (Basic) assessment identifies a potential issue that requires more detailed information, a Level 3 (Advanced) assessment is recommended. Sonic tomography is a common Level 3 technique that uses sound waves to create a map of internal decay without significantly wounding the tree, making it ideal for gathering quantitative data on high-value trees.

(ISA) ISA Certified Arborist Practice Test

(ISA) ISA Certified Arborist Practice Test

ISA Tree Risk Assessment Questions and Answers