ISA Certified Arborist — Practice Exam
Trees and construction: practice questions
Our ISA Certified Arborist bank has 27 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.
Question 1
A mature, stressed tree has a 20-inch trunk diameter. What is its Protected Root Zone radius?
- 10 feet
- 20 feet
- 30 feet
- 40 feet
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C. 30 feet — 20 inches × 1.5 = 30 feet.
Question 2
Under the USDA Forest Service risk guidelines, when do root problems indicate a high risk of failure?
- When any surface root is visible
- When roots grow under nearby pavement or walks
- When a single small root is cut
- When over 40% of roots in the root zone are damaged
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D. When over 40% of roots in the root zone are damaged — Girdling roots constricting more than 40 percent of the root collar also count as high risk.
Question 3
What should tree protection fences have?
- No signs, to avoid attention
- Signs saying why to stay out and whom to contact
- Gates that are always open
- Only temporary flagging tape
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B. Signs saying why to stay out and whom to contact — An arborist recommends where to install them.
Question 4
When should an arborist be involved in a construction project?
- Only after the building is finished
- Only during demolition
- From the planning phase through post-construction
- Only after damage appears
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C. From the planning phase through post-construction — Minor design changes early can save trees.
Question 5
Why should fertilization be limited right after construction damage?
- Quick-release salts draw water from roots, and excess nitrogen favours top growth over roots
- Fertilizer is illegal near construction
- Roots absorb fertilizer too slowly after damage for it to have any effect
- It would make the tree grow too tall
Show the answer
A. Quick-release salts draw water from roots, and excess nitrogen favours top growth over roots — Base later fertilization on soil or foliar analysis.