ISA Cheat Sheet 2026

The 30 highest-yield ISA facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. How does tree bark protect the tree? → Protects from pests and environmental damage
2. How can tree roots be protected during construction? → By fencing off the root zone
3. What is the primary purpose of a 'static load test' on a tree? → Apply controlled force to assess structural response and root plate movement
4. Which structural defect is characterized by a union where bark is trapped between two stems, reducing wood-to-wood contact? → Included bark
5. How do trees adapt to drought conditions? → Reduce leaf growth
6. Sudden Branch Drop syndrome is most likely to occur: → On calm, hot afternoons in summer, often on seemingly healthy branches
7. Sulfur is used as a soil amendment to: → Lower soil pH in alkaline soils
8. What is the recommended mulch depth when mulching around a newly planted tree? → 2–4 inches
9. Which condition would most likely cause a previously stable tree to become a high risk after a construction project nearby? → Grade change that raises soil level over the root zone
10. What is the function of root hairs on a tree's fine roots? → Greatly increase the surface area for water and nutrient absorption
11. What is the purpose of a 'tailboard safety briefing' conducted before the start of each job? → To communicate the job plan, identified hazards, and safety measures to all crew members
12. What is the proper hand signal for 'stop' during crane-assisted tree removal? → One arm extended with a closed fist
13. Which of the following best describes 'reaction wood' in angiosperms? → Tension wood formed on the upper side of leaning stems
14. Phosphorus availability to tree roots is greatest at which soil pH range? → 6.0–7.0
15. The soil textural triangle is used to classify soil texture based on percentages of: → Sand, silt, and clay
16. Which of the following is a sign of excessive soil nitrogen in landscape trees? → Excessive succulent vegetative growth with reduced hardiness
17. A soil test reports a pH of 5.0. Which amendment would most effectively raise the pH? → Ground limestone (calcitic lime)
18. What is the function of phloem in trees? → Transferring sugars and nutrients from leaves
19. A tree leans significantly toward a high-occupancy target. The arborist finds healthy root flare and no decay. The MOST important next assessment step is: → Measure the lean angle and compare to the root plate radius to assess overturn potential
20. What is the primary function of soil organic matter for tree health? → Improves nutrient retention and soil structure
21. What is the primary benefit of high Cation Exchange Capacity (CEC) in soil for tree health? → It enhances the soil's ability to retain and supply essential nutrient cations.
22. What role does lignin play in wood cell walls? → Adds rigidity and decay resistance to cell walls
23. What is the primary mechanism by which water moves upward through the xylem in tall trees? → Cohesion-tension generated by transpiration pulls water columns upward
24. Which of the following correctly pairs a tree tissue with its primary function? → Cambium - a layer of cells responsible for secondary growth (thickening).
25. Fertilization of a newly planted tree is MOST appropriate: → After at least one full growing season of establishment
26. When performing aerial rescue of an injured arborist, what is the first priority? → Assess the scene for hazards and ensure rescuer safety before approaching the victim
27. Which tree growth form is MOST appropriate for planting in corridors beneath overhead utility lines? → Columnar or fastigiate
28. When selecting trees for a site with chronically compacted soils, which characteristic is MOST desirable? → Tolerance of reduced oxygen in the root zone
29. What diagnostic technique involves removing a section of bark to examine underlying wood for discoloration patterns? → Bark tracing
30. Anti-desiccant sprays are sometimes applied to newly planted trees primarily to: → Reduce water loss through transpiration from leaf surfaces