International Society of
TSET ELPMAS · ASI
Arboriculture
PROMOTING ARBORICULTURE
ISA Certified Arborist Examination
EST. 1924
T H R O U G H R E S E A R C H · T E C H N O L O G Y · E D U C AT I O N
ISA Arborist Study Guide Sample Test Questions
T R E E B I O LO G Y · S O I L S C I E N C E · P R U N I N G · P L A N T H E A LT H C A R E · S A F E TY
INSTITUTION International Society of EXAM TYPE ISA Certified Arborist
Arboriculture (ISA) Examination
PROGRAM Professional Certification — ACADEMIC YEAR
Arboriculture
EXAM TITLE ISA Arborist Study Guide Sample TOTAL QUESTIONS 81 Questions
Test Questions
COURSE TITLE Arborist Certification FORMAT Multiple Choice — Select the
Preparation Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question.
▸ Tree biology, soil science, pruning techniques, plant health care, and safety standards are core testable
domains.
▸ ISA certification standards and ANSI A300 practices are referenced throughout.
▸ Correct answers and rationales appear below each question for self-assessment and exam preparation.
▸ All content reflects the ISA Certified Arborist examination domains and current best practices.
, SECTION I — TREE BIOLOGY · SOIL SCIENCE · PRUNING ·
Questions 1 – 81
PLANT HEALTH CARE · SAFETY
1. When cutting through a tree with a chainsaw or drilling into a tree, what is the correct
order of layers you would pass through (from outside to inside)?
A. Xylem, cambium, phloem, bark
B. Bark, phloem, cambium, xylem
C. Cambium, bark, phloem, xylem
D. Phloem, bark, cambium, xylem
CORRECT ANSWER B — Bark, phloem, cambium, xylem
RATIONALE From the outside in, the order is: bark (outer protective layer), phloem (inner bark
that transports photosynthates), cambium (thin meristematic layer responsible
for diameter growth), and xylem (wood that transports water and minerals). This
sequence is fundamental to understanding tree anatomy and the effects of
wounds, girdling, and drilling operations.
2. What happens if the terminal bud is removed during pruning?
A. The tree stops growing entirely
B. Growth may be stimulated in lateral buds
C. Only root growth is affected
D. The cambium layer dies back
CORRECT ANSWER B — Growth may be stimulated in lateral buds
RATIONALE Removing the terminal bud removes apical dominance — the hormonal
suppression of lateral buds by auxin produced at the terminal bud. This releases
lateral buds from dormancy, stimulating them to grow. This principle is used in
pruning to encourage bushier growth. The tree does not stop growing (A); rather,
growth is redistributed to lateral shoots.
,3. The growth rings of a tree are visible because of the rapid growth rate of earlywood
relative to latewood. What else can growth rings tell us?
A. They only indicate the tree's age and nothing else
B. They can be counted to approximate the tree's age and can give information about
growth conditions in previous years
C. They are only visible in conifers, not in deciduous trees
D. They indicate only the health of the phloem
CORRECT ANSWER B — They can be counted to approximate the tree's age and can give
information about growth conditions in previous years
RATIONALE Annual growth rings form because earlywood (spring growth) is less dense and
lighter in color, while latewood (summer/fall growth) is denser and darker.
Counting rings approximates age. Ring width varies with growing conditions —
wide rings indicate favorable years (good moisture, nutrients); narrow rings
indicate stress (drought, competition, defoliation). This science is called
dendrochronology.
4. Which layer of cells is responsible for the outward growth and increased girth of a tree?
A. Phloem
B. Xylem
C. Cambium
D. Bark
CORRECT ANSWER C — Cambium
RATIONALE The vascular cambium is a thin layer of meristematic cells between the phloem
and xylem. It divides to produce new xylem cells (to the inside) and new phloem
cells (to the outside), resulting in diameter growth. Phloem (A) transports
photosynthates; xylem (B) transports water; bark (D) is protective. Only the
cambium generates new cells for girth increase.
, 5. Mycorrhizae are best described as:
A. A type of root rot disease
B. A symbiotic relationship between fungi and roots
C. The fine root hairs that absorb water
D. A type of insect pest that feeds on roots
CORRECT ANSWER B — A symbiotic relationship between fungi and roots
RATIONALE Mycorrhizae are mutualistic associations between fungi and tree roots. The fungi
extend the effective surface area of roots for water and nutrient absorption
(especially phosphorus), while the tree provides carbohydrates to the fungi. This
relationship is critical for tree health — many trees cannot thrive without
mycorrhizal partners. They are beneficial, not pathogenic (A).
6. Douglas-fir (Pseudotsuga menziesii) differs from balsam fir (Abies balsamea) in that:
A. They are the same species but different varieties
B. They are not in the same genus
C. One is deciduous and the other is evergreen
D. They have identical needle arrangements
CORRECT ANSWER B — They are not in the same genus
RATIONALE Douglas-fir is in the genus Pseudotsuga, while balsam fir is in the genus Abies.
Despite the common name "fir," Douglas-fir is not a true fir (Abies spp.). Scientific
nomenclature reveals this distinction — the first part of the scientific name
identifies the genus. This is a classic example of why common names can be
misleading and scientific names provide taxonomic clarity.
TSET ELPMAS · ASI
Arboriculture
PROMOTING ARBORICULTURE
ISA Certified Arborist Examination
EST. 1924
T H R O U G H R E S E A R C H · T E C H N O L O G Y · E D U C AT I O N
ISA Arborist Study Guide Sample Test Questions
T R E E B I O LO G Y · S O I L S C I E N C E · P R U N I N G · P L A N T H E A LT H C A R E · S A F E TY
INSTITUTION International Society of EXAM TYPE ISA Certified Arborist
Arboriculture (ISA) Examination
PROGRAM Professional Certification — ACADEMIC YEAR
Arboriculture
EXAM TITLE ISA Arborist Study Guide Sample TOTAL QUESTIONS 81 Questions
Test Questions
COURSE TITLE Arborist Certification FORMAT Multiple Choice — Select the
Preparation Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question.
▸ Tree biology, soil science, pruning techniques, plant health care, and safety standards are core testable
domains.
▸ ISA certification standards and ANSI A300 practices are referenced throughout.
▸ Correct answers and rationales appear below each question for self-assessment and exam preparation.
▸ All content reflects the ISA Certified Arborist examination domains and current best practices.
, SECTION I — TREE BIOLOGY · SOIL SCIENCE · PRUNING ·
Questions 1 – 81
PLANT HEALTH CARE · SAFETY
1. When cutting through a tree with a chainsaw or drilling into a tree, what is the correct
order of layers you would pass through (from outside to inside)?
A. Xylem, cambium, phloem, bark
B. Bark, phloem, cambium, xylem
C. Cambium, bark, phloem, xylem
D. Phloem, bark, cambium, xylem
CORRECT ANSWER B — Bark, phloem, cambium, xylem
RATIONALE From the outside in, the order is: bark (outer protective layer), phloem (inner bark
that transports photosynthates), cambium (thin meristematic layer responsible
for diameter growth), and xylem (wood that transports water and minerals). This
sequence is fundamental to understanding tree anatomy and the effects of
wounds, girdling, and drilling operations.
2. What happens if the terminal bud is removed during pruning?
A. The tree stops growing entirely
B. Growth may be stimulated in lateral buds
C. Only root growth is affected
D. The cambium layer dies back
CORRECT ANSWER B — Growth may be stimulated in lateral buds
RATIONALE Removing the terminal bud removes apical dominance — the hormonal
suppression of lateral buds by auxin produced at the terminal bud. This releases
lateral buds from dormancy, stimulating them to grow. This principle is used in
pruning to encourage bushier growth. The tree does not stop growing (A); rather,
growth is redistributed to lateral shoots.
,3. The growth rings of a tree are visible because of the rapid growth rate of earlywood
relative to latewood. What else can growth rings tell us?
A. They only indicate the tree's age and nothing else
B. They can be counted to approximate the tree's age and can give information about
growth conditions in previous years
C. They are only visible in conifers, not in deciduous trees
D. They indicate only the health of the phloem
CORRECT ANSWER B — They can be counted to approximate the tree's age and can give
information about growth conditions in previous years
RATIONALE Annual growth rings form because earlywood (spring growth) is less dense and
lighter in color, while latewood (summer/fall growth) is denser and darker.
Counting rings approximates age. Ring width varies with growing conditions —
wide rings indicate favorable years (good moisture, nutrients); narrow rings
indicate stress (drought, competition, defoliation). This science is called
dendrochronology.
4. Which layer of cells is responsible for the outward growth and increased girth of a tree?
A. Phloem
B. Xylem
C. Cambium
D. Bark
CORRECT ANSWER C — Cambium
RATIONALE The vascular cambium is a thin layer of meristematic cells between the phloem
and xylem. It divides to produce new xylem cells (to the inside) and new phloem
cells (to the outside), resulting in diameter growth. Phloem (A) transports
photosynthates; xylem (B) transports water; bark (D) is protective. Only the
cambium generates new cells for girth increase.
, 5. Mycorrhizae are best described as:
A. A type of root rot disease
B. A symbiotic relationship between fungi and roots
C. The fine root hairs that absorb water
D. A type of insect pest that feeds on roots
CORRECT ANSWER B — A symbiotic relationship between fungi and roots
RATIONALE Mycorrhizae are mutualistic associations between fungi and tree roots. The fungi
extend the effective surface area of roots for water and nutrient absorption
(especially phosphorus), while the tree provides carbohydrates to the fungi. This
relationship is critical for tree health — many trees cannot thrive without
mycorrhizal partners. They are beneficial, not pathogenic (A).
6. Douglas-fir (Pseudotsuga menziesii) differs from balsam fir (Abies balsamea) in that:
A. They are the same species but different varieties
B. They are not in the same genus
C. One is deciduous and the other is evergreen
D. They have identical needle arrangements
CORRECT ANSWER B — They are not in the same genus
RATIONALE Douglas-fir is in the genus Pseudotsuga, while balsam fir is in the genus Abies.
Despite the common name "fir," Douglas-fir is not a true fir (Abies spp.). Scientific
nomenclature reveals this distinction — the first part of the scientific name
identifies the genus. This is a classic example of why common names can be
misleading and scientific names provide taxonomic clarity.
