ISA Arborist Certification Exam Bank 2026/2027 | Certified Arborist Practice Questions, Answers & Study Guide

ISA Arborist Certification Exam Bank
2026/2027 | Certified Arborist Practice
Questions, Answers & Study Guide

ISA ARBORIST CERTIFICATION EXAM BANK 2026/2027 | CERTIFIED ARBORIST
PRACTICE QUESTIONS, ANSWERS & STUDY GUIDE



DOCUMENT OVERVIEW

• This exam bank contains 200 comprehensive practice questions designed to
prepare candidates for the ISA Certified Arborist examination, covering all major
domains and competencies tested.

• Use this material to identify knowledge gaps, reinforce understanding through
detailed rationales, and build confidence through repeated practice across all core
arboricultural topics.




SECTION 1: TREE BIOLOGY, PHYSIOLOGY & ANATOMY



1. Which of the following best describes the primary function of the cambium
layer in a tree?

A) Protection of the tree from external damage and weather

B) Storage of nutrients and carbohydrates for winter survival

C) Production of new vascular tissue (xylem and phloem) for growth

D) Absorption of water and minerals from the soil

E) Photosynthesis and production of glucose

CORRECT ANSWER: C) Production of new vascular tissue (xylem and phloem)
for growth

,RATIONALE: The cambium is the thin meristematic layer located between the
xylem and phloem. It is responsible for secondary growth, producing new xylem
cells inward and new phloem cells outward, which allows the tree to increase in
diameter. This is a fundamental function in tree development and is critical to
understanding tree physiology for arborists.



2. What is the primary role of the phloem in tree physiology?

A) Conduction of water and minerals from roots to leaves

B) Transport of photosynthetically produced sugars from leaves to all tree parts

C) Support and structural integrity of the tree

D) Protection of the tree from pathogenic organisms

E) Storage of nitrogen compounds in tree tissues

CORRECT ANSWER: B) Transport of photosynthetically produced sugars from
leaves to all tree parts

RATIONALE: The phloem is responsible for translocation of sugars and other
organic compounds produced during photosynthesis. This nutrient transport
occurs in both directions and is essential for feeding all living tissues in the tree,
including roots, branches, and growing points. Understanding phloem function is
critical for arborists working with tree health.



3. Which tissue in a tree is responsible for water and mineral transport from
the roots to the leaves?

A) Phloem and cambium

B) Xylem and sapwood

C) Bark and heartwood

D) Cortex and epidermis

E) Periderm and lenticels

,CORRECT ANSWER: B) Xylem and sapwood

RATIONALE: The xylem is the primary vascular tissue responsible for water and
mineral transport from the roots upward through the tree. The sapwood is the
living, functional portion of the xylem that actively conducts water. The heartwood,
though it contains xylem cells, is non-functional in water transport. This distinction
is important for arborists to understand tree physiology and drought stress
responses.



4. What is heartwood, and what is its primary function in a living tree?

A) The actively growing layer that produces new cells for expansion

B) The outermost protective layer composed of dead bark cells

C) The inner, non-living, chemically-changed wood that provides structural support

D) The vascular tissue responsible for nutrient transport throughout the tree

E) The layer where photosynthesis occurs to produce energy

CORRECT ANSWER: C) The inner, non-living, chemically-changed wood that
provides structural support

RATIONALE: Heartwood is the central, non-living portion of the wood that has
undergone chemical changes and contains no living cells. While it no longer
conducts water or nutrients, it remains structurally important and is resistant to
decay due to chemical compounds that accumulate in it. Understanding heartwood
is essential for assessing tree safety and structural integrity.



5. Which of the following correctly describes the bark of a tree?

A) A single layer of dead cells that provides minimal protection

B) A complex tissue composed of the cork, cortex, and phloem that protects the
tree

C) Primarily composed of xylem cells that have become inactive

, D) A growth layer that is always actively dividing

E) The outermost layer of xylem cells that conduct water

CORRECT ANSWER: B) A complex tissue composed of the cork, cortex, and
phloem that protects the tree

RATIONALE: The bark is a complex protective covering composed of multiple layers
including the periderm (cork), cortex, and inner bark (phloem). It provides
protection from pests, disease, weather, and mechanical injury. For arborists,
understanding bark structure is important for recognizing damage, assessing tree
health, and understanding how trees respond to injuries.



6. What is the primary function of lenticels in tree bark?

A) To transport sugars throughout the tree

B) To conduct water upward from the roots

C) To allow gas exchange between the tree interior and atmosphere

D) To strengthen the bark and provide rigidity

E) To store food reserves for dormancy

CORRECT ANSWER: C) To allow gas exchange between the tree interior and
atmosphere

RATIONALE: Lenticels are porous structures in the bark that allow for gas
exchange, enabling oxygen to reach living cells in the bark and roots, while allowing
carbon dioxide to exit. They are particularly important in waterlogged soils where
oxygen availability is limited. Clogging of lenticels from soil compaction or flooding
can stress trees and is a consideration in urban arboriculture.



7. Which of the following best describes apical dominance in tree growth?

A) The tendency for a tree to grow wider than it grows tall