ISA Exam (Arborist Certification)
Glossary# Pre Questions with Detailed
Answers 2026-2027 Updated.
abiotic: - Answer pertaining to the nonliving parts of an ecosystem, such as soil particles,
bedrock, air, water.
abscisic acid (ABA): - Answer a plant hormone that stimulates stomatal closure and promotes
seed and bud dormancy.
abscission zone: - Answer a wall of cells at the base of a petiole, that allows the leaf to
separate from the stem.
acceptable risk: - Answer the amount of risk that an owner is willing to accept before tree
failure.
accessibility: - Answer the establishment of a location used to enter a site.
acidic soil: - Answer having a pH les than 7.0, in contrast with alkaline which has a pH that is
higher than 7.0.
actinomycetes: - Answer microorganisms that have some characteristics of fungi and bacteria.
Soil actinomycetes are very tolerant of water stress and contribute through their actions to that
"good earth" aroma after a rain.
action: - Answer the number of distinct motions for the carabineers and snaps gate to be
opened.
action threshold: - Answer the point at which a pest requires the implementation of a
management tactic or control.
acute crotches: - Answer stronger and wider than a co-dominant crotch, they are not likely to
be a branch that will fail in high winds and are considered desirable.
adaptive growth: - Answer an increase in wood production in localized areas on a tree, in
response to a decrease in wood strength or external loading to maintain an even distribution of
forces across the structure.
,drip line - Answer a boundary on the ground delineated by the branch spread of a single tree
or group of trees.
adsorption: - Answer adhesion on contact of molecules to the surface of solids or liquids with
which they are in contact.
advanced assessment: - Answer an assessment performed to provide detailed information
about specific tree parts, defects or site conditions.
adventitious/epicormic growth: - Answer new growth arising directly from dormant or new
buds on main branches, stems, or trunks often in response to moisture and light that has no
connection to apical meristems.
adventitious root: - Answer a root arising from parts of the root or the stem, often in response
to moisture and darkness that has no connection to apical meristems.
aeration: - Answer the provision of air to the soil to alleviate soil compaction.
aerial lift device: - Answer a truck with booms and a bucket, for elevating a worker to a tree's
crown; may also be mounted on a self-propelled machine known as a mini-lift.
aerial rescue: - Answer a method of bringing an injured worker down from a tree.
aerial roots: - Answer roots that grow from stems toward the soil with the capacity to become
prop roots when they anchor in the soil.
aerobic microorganisms: - Answer these microbes require free, gaseous oxygen for growth.
aggregate: - Answer soil such as sand, silt, or clay, a cluster of soil particles and organic matter,
bonded together by exudates from microorganisms. It is often used under paved surfaces, as
backfill.
agroforestry or agro-sylviculture: - Answer is a land use management system in which trees or
shrubs are grown around or among crops or pastureland.
Air Spade™: - Answer the commonly used trade name for an air tool.
air terminal: - Answer the uppermost point of a lightning protection system in a tree. It is
usually made of copper.
,air tool: - Answer also called air excavation device, a device that uses a jet of compressed air to
excavate soil within the root zone of trees and minimize damage to tree roots.
alkaline soil: - Answer having a pH greater than 7.0, in contrast with acidic soil which has a pH
lower than 7.0.
alkaloids: - Answer substances that are produced by trees and contain nitrogen and are used
by humans for medicines.
allée: - Answer two parallel rows of trees, usually of the same species, form, and age, often
having canopies that have grown together.
allelopathy: - Answer the production of substances by one tree that adversely affect other
trees nearby. Root exudates from some trees can kill or stall growth of many soil organisms.
alternate leaves: - Answer occur when there is one bud or leaf at a node.
amylase: - Answer an enzyme that can change the starch chains back to glucose molecules.
anaerobic microorganisms: - Answer these microbes live in the absence of free oxygen.
amon-eye nut: - Answer drop-forged eye nut is used to fasten through-hardware anchor(s),
used when cabling trees.
anchor: - Answer the hardware installed to affix and/or terminate a cable or guy to the tree,
ground, or other device.
anchor-tree: - Answer a tree used to provide supplemental support in a guying installation.
angiosperms: - Answer hardwood trees that have covered seeds such as oaks and maples. The
seed is born within an ovary.
anions: - Answer negatively charged atoms or molecules in fertilizer that become available to
the plant in water.
ANSI: - Answer the American National Standards Institute.
, ANSI A300: - Answer the performance parameters established by industry consensus as a rule
for the measure of extent, quality, quantity, value, or weight used to write specifications.
ANSI Z60.1: - Answer the American Standard for Nursery Stock, 2014 edition.
ANSI Z133: - Answer the Safety Standard that provides the most current criteria in the United
States for arborists and other workers engaged in arboricultural operations.
anther: - Answer the pollen producing part of a flower.
anthocyanin: - Answer a chemical that gives the red pigments to leaves and other plant organs.
antitranspirant: - Answer a substance applied to the foliage of plants to reduce water loss.
anvil-type pruning tool: - Answer a pruning tool that has a sharp straight blade that cuts
against a flat non-cutting surface.
apical dominance: - Answer the inhibition of growth of lateral buds by the terminal or apical
bud.
apical meristem: - Answer meristems increase the length of stems and roots, and produce
flowers.
apoplast: - Answer the framework of non-living cells and cell walls in wood and bark. The
apoplast stores bound water, which does not flow.
appraisal: - Answer placing a monetary value on a tree.
approach distances: - Answer the minimum distances between energized conductors and
personnel.
arboriculture: - Answer the art, science, technology, and business of commercial, public, and
utility tree care. Arboriculture focus is on the tree while the focus of forestry is on all trees.
arborist: - Answer an individual engaged in the profession of arboriculture who, through
experience, education, and training, possesses the competence to perform the management of
trees and other woody plants.
Glossary# Pre Questions with Detailed
Answers 2026-2027 Updated.
abiotic: - Answer pertaining to the nonliving parts of an ecosystem, such as soil particles,
bedrock, air, water.
abscisic acid (ABA): - Answer a plant hormone that stimulates stomatal closure and promotes
seed and bud dormancy.
abscission zone: - Answer a wall of cells at the base of a petiole, that allows the leaf to
separate from the stem.
acceptable risk: - Answer the amount of risk that an owner is willing to accept before tree
failure.
accessibility: - Answer the establishment of a location used to enter a site.
acidic soil: - Answer having a pH les than 7.0, in contrast with alkaline which has a pH that is
higher than 7.0.
actinomycetes: - Answer microorganisms that have some characteristics of fungi and bacteria.
Soil actinomycetes are very tolerant of water stress and contribute through their actions to that
"good earth" aroma after a rain.
action: - Answer the number of distinct motions for the carabineers and snaps gate to be
opened.
action threshold: - Answer the point at which a pest requires the implementation of a
management tactic or control.
acute crotches: - Answer stronger and wider than a co-dominant crotch, they are not likely to
be a branch that will fail in high winds and are considered desirable.
adaptive growth: - Answer an increase in wood production in localized areas on a tree, in
response to a decrease in wood strength or external loading to maintain an even distribution of
forces across the structure.
,drip line - Answer a boundary on the ground delineated by the branch spread of a single tree
or group of trees.
adsorption: - Answer adhesion on contact of molecules to the surface of solids or liquids with
which they are in contact.
advanced assessment: - Answer an assessment performed to provide detailed information
about specific tree parts, defects or site conditions.
adventitious/epicormic growth: - Answer new growth arising directly from dormant or new
buds on main branches, stems, or trunks often in response to moisture and light that has no
connection to apical meristems.
adventitious root: - Answer a root arising from parts of the root or the stem, often in response
to moisture and darkness that has no connection to apical meristems.
aeration: - Answer the provision of air to the soil to alleviate soil compaction.
aerial lift device: - Answer a truck with booms and a bucket, for elevating a worker to a tree's
crown; may also be mounted on a self-propelled machine known as a mini-lift.
aerial rescue: - Answer a method of bringing an injured worker down from a tree.
aerial roots: - Answer roots that grow from stems toward the soil with the capacity to become
prop roots when they anchor in the soil.
aerobic microorganisms: - Answer these microbes require free, gaseous oxygen for growth.
aggregate: - Answer soil such as sand, silt, or clay, a cluster of soil particles and organic matter,
bonded together by exudates from microorganisms. It is often used under paved surfaces, as
backfill.
agroforestry or agro-sylviculture: - Answer is a land use management system in which trees or
shrubs are grown around or among crops or pastureland.
Air Spade™: - Answer the commonly used trade name for an air tool.
air terminal: - Answer the uppermost point of a lightning protection system in a tree. It is
usually made of copper.
,air tool: - Answer also called air excavation device, a device that uses a jet of compressed air to
excavate soil within the root zone of trees and minimize damage to tree roots.
alkaline soil: - Answer having a pH greater than 7.0, in contrast with acidic soil which has a pH
lower than 7.0.
alkaloids: - Answer substances that are produced by trees and contain nitrogen and are used
by humans for medicines.
allée: - Answer two parallel rows of trees, usually of the same species, form, and age, often
having canopies that have grown together.
allelopathy: - Answer the production of substances by one tree that adversely affect other
trees nearby. Root exudates from some trees can kill or stall growth of many soil organisms.
alternate leaves: - Answer occur when there is one bud or leaf at a node.
amylase: - Answer an enzyme that can change the starch chains back to glucose molecules.
anaerobic microorganisms: - Answer these microbes live in the absence of free oxygen.
amon-eye nut: - Answer drop-forged eye nut is used to fasten through-hardware anchor(s),
used when cabling trees.
anchor: - Answer the hardware installed to affix and/or terminate a cable or guy to the tree,
ground, or other device.
anchor-tree: - Answer a tree used to provide supplemental support in a guying installation.
angiosperms: - Answer hardwood trees that have covered seeds such as oaks and maples. The
seed is born within an ovary.
anions: - Answer negatively charged atoms or molecules in fertilizer that become available to
the plant in water.
ANSI: - Answer the American National Standards Institute.
, ANSI A300: - Answer the performance parameters established by industry consensus as a rule
for the measure of extent, quality, quantity, value, or weight used to write specifications.
ANSI Z60.1: - Answer the American Standard for Nursery Stock, 2014 edition.
ANSI Z133: - Answer the Safety Standard that provides the most current criteria in the United
States for arborists and other workers engaged in arboricultural operations.
anther: - Answer the pollen producing part of a flower.
anthocyanin: - Answer a chemical that gives the red pigments to leaves and other plant organs.
antitranspirant: - Answer a substance applied to the foliage of plants to reduce water loss.
anvil-type pruning tool: - Answer a pruning tool that has a sharp straight blade that cuts
against a flat non-cutting surface.
apical dominance: - Answer the inhibition of growth of lateral buds by the terminal or apical
bud.
apical meristem: - Answer meristems increase the length of stems and roots, and produce
flowers.
apoplast: - Answer the framework of non-living cells and cell walls in wood and bark. The
apoplast stores bound water, which does not flow.
appraisal: - Answer placing a monetary value on a tree.
approach distances: - Answer the minimum distances between energized conductors and
personnel.
arboriculture: - Answer the art, science, technology, and business of commercial, public, and
utility tree care. Arboriculture focus is on the tree while the focus of forestry is on all trees.
arborist: - Answer an individual engaged in the profession of arboriculture who, through
experience, education, and training, possesses the competence to perform the management of
trees and other woody plants.
