ISA Certified Arborist Practice Test

Correct answer: A. Roots in saturated soil could not get enough oxygen

Roots need oxygen for respiration, the process that releases energy from sugars. When soil stays saturated, water fills the pore spaces, oxygen runs short, and roots stop growing and may die. Wet soil does not stop transpiration from the leaves or dilute phloem sugars, and constant moisture does not trigger root dormancy.

• B: Soil water does not enter the phloem and dilute its sugars.
• C: Transpiration happens at the leaves and is not stopped by wet soil.
• D: Root dormancy is not triggered by constant soil moisture.

Sources: Vegetative Plant Parts (EM 9904), Oregon State University Extension Service ; Extension Gardener Handbook, Chapter 3: Botany, NC State Extension

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Correct answer: B. The bristle-tipped oak is in the red oak group, so it needs attention first

Bristle tips on the leaf lobes mark the red oak group, which includes northern red, northern pin and black oaks. A red oak that shows oak wilt symptoms usually loses most of its leaves and dies within about a month, while white oaks decline much more slowly and may survive infection. Swapping the two groups would send protective effort to the less vulnerable tree.

• A: Rounded lobes without bristle tips are typical of the white oak group, not the red oak group.
• C: Only the rounded-lobed tree fits the white oak group; the bristle-tipped tree is a red oak and is highly susceptible.
• D: Bristle-tipped versus rounded lobes is a standard way to separate red oaks from white oaks, and the groups differ sharply in oak wilt susceptibility.

Sources: Oak Wilt, Wisconsin Department of Natural Resources ; Virginia Tech Dendrology Fact Sheet: northern red oak (Quercus rubra), Virginia Tech Department of Forest Resources and Environmental Conservation ; Virginia Tech Dendrology Fact Sheet: white oak (Quercus alba), Virginia Tech Department of Forest Resources and Environmental Conservation

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Correct answer: A. Cement-based building debris mixed into the soil during construction

Urban soils often contain concrete, mortar and other cement-based materials left after construction, and these calcium carbonate-rich materials can raise soil pH well above that of nearby undisturbed soil. Acid rain and ammonium-based nitrogen fertilizers push pH down, not up, and decomposing leaf litter is not a usual cause of strongly alkaline soil.

• B: Acid rain would lower soil pH, not raise it.
• C: Nitrogen fertilizers tend to acidify soil over time.
• D: Decomposing leaf litter does not typically make a soil strongly alkaline.

Sources: Basics of Urban Soil Health (Technical Note No. 470-02, January 2024), USDA Natural Resources Conservation Service ; Soil pH and the Home Landscape or Garden (SL 256/SS480), UF/IFAS Extension

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Correct answer: A. Add soil to the bottom and firm it so the ball sits at the right height

A root ball set on loose soil sinks as that soil settles, leaving the tree too deep. UF/IFAS advises adding soil to the bottom of an over-dug hole and compacting it with your foot, and University of Maryland Extension cautions against loosening the soil at the hole's base, to keep the tree from settling. Leaving loose soil to encourage deep rooting is the tempting wrong answer; the loose layer simply compresses and the tree settles.

• B: Loose soil under the ball compresses, so the tree sinks; University of Maryland Extension says not to loosen the bottom of the hole for this reason.
• C: Setting the ball too low and adding soil on top buries the root flare.
• D: UF/IFAS fixes an over-dug hole by adding soil to the bottom and firming it, not by filling it with mulch.

Sources: Chapter 11 — Planting and Establishing Trees (ENH1061/EP314), archival copy, UF/IFAS Extension (EDIS) ; Trees Planted Too Deeply, University of Maryland Extension

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Correct answer: C. Say the flow is mostly cosmetic; next time prune after leaves mature

Birch, maple and several other species bleed sap heavily when pruned in late winter or early spring. Clemson Extension says this sap flow is not harmful, though it is unsightly, and that pruning after the leaves have matured reduces it; Colorado State University Extension also calls it a cosmetic issue. Wound dressings are not recommended, flush cuts injure the trunk, and sap flow from fresh cuts is normal rather than a sign of infection.

• A: Dressings are not recommended and are not needed for normal sap flow.
• B: Flush cuts injure trunk tissue and invite decay.
• D: Sap flow from fresh cuts on these species is normal, not a symptom of infection.

Sources: Principles & Practices for Pruning Trees (HGIC 1003), Clemson Cooperative Extension, Home & Garden Information Center ; Pruning Cuts (CMG GardenNotes #612), Colorado State University Extension

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Correct answer: C. A favorable environment

Disease develops only when a susceptible host, a pathogen, and a favorable environment come together. Here the host is susceptible and the fungus is present, so the dry spring removed the environment corner: most fungal spores need free water on the plant surface before they can germinate and infect. Vectors matter for some diseases, but they are not one of the triangle's three corners.

• A: The stem says the species is susceptible, so the host corner is present.
• B: The fungus is well established at the site, so the pathogen corner is present.
• D: Vectors appear in some expanded models, but the dry spring points to the missing environment corner.

Source: Extension Gardener Handbook, Chapter 5: Diseases and Disorders, NC State Extension

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Correct answer: B. 30 feet

The guideline sets a radius: 24 inches × 1.25 feet per inch = 30 feet from the trunk to the fence, the "good protection" level in NC State's table. The same table lists "better" and "best" zones at 1.5 and 2.5 feet per inch, which give 36 and 60 feet for this tree, but the question asks for the minimum. Twenty-four feet would allow only 1 foot per inch, below NC State's minimum.

• A: This applies 1 foot per inch, which is less than the NC State minimum of 1.25 feet per inch.
• C: Thirty-six feet is NC State's "better protection" level (1.5 feet per inch), more than the minimum the question asks for.
• D: Sixty feet is NC State's "best protection" level (2.5 feet per inch), well above the minimum.

Sources: Construction and Tree Protection (AG-685), NC State Extension ; Construction and Tree Protection (AG-685), NC State Extension

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Correct answer: A. Identifying high risk and then taking no action can be treated as negligence

The USDA guide says high-risk trees must be dealt with as soon as possible after they are identified, and that a community may be assumed negligent if it finds high risk and then does nothing. It also states that not having funds does not relieve a community of its responsibility in lawsuits. The guide adds that a community proves it took reasonable care by producing records that show its trees were not just inspected but that hazardous ones were corrected in a timely manner, so a file of known, uncorrected high-risk trees does not protect the city.

• B: A record of known, uncorrected high risk works against the city rather than protecting it.
• C: The guide puts the duty to act on the community that identified the risk, not on the inspector who rated the trees.
• D: The guide states that not having funds does not absolve a community of responsibility.

Sources: Urban Tree Risk Management: A Community Guide to Program Design and Implementation (NA-TP-03-03), USDA Forest Service, Northeastern Area State and Private Forestry ; Urban Tree Risk Management: A Community Guide to Program Design and Implementation (NA-TP-03-03), USDA Forest Service, Northeastern Area State and Private Forestry ; Urban Tree Risk Management: A Community Guide to Program Design and Implementation (NA-TP-03-03), USDA Forest Service, Northeastern Area State and Private Forestry

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Correct answer: A. With the climbing line plus a work-positioning lanyard, as two separate attachments

OSHA's tree care hazard bulletin lists, among the things climbers should be trained on, using a second means of fall protection along with the arborist climbing line, for example a work-positioning lanyard or another climbing line, and the Forest Service climbing guide requires at least two systems whenever a chain saw is used in a tree, one of which must be cut-resistant, such as a steel-core lanyard or chain. If the saw damages one attachment, the other still holds the climber. A single attachment has no backup, and anchoring to the piece being cut is never acceptable.

• B: A single climbing line has no backup if the saw contacts it.
• C: A lanyard alone is a single attachment with no backup if it is cut or fails.
• D: The anchor would fall with the limb once it is cut free.

Sources: Tree Care Work: Falls and Falling Object Hazards (Hazard Bulletin HB-3731), Occupational Safety and Health Administration (OSHA) ; National Tree Climbing Guide (2015 Electronic Edition), USDA Forest Service ; National Tree Climbing Guide (2015 Electronic Edition), USDA Forest Service

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Correct answer: D. 3.0:1

A BCR divides total benefits by total costs: $2.4 million divided by $0.8 million is 3.0, or about $3 in benefits for every $1 spent. The tempting 2.0:1 comes from dividing net benefits ($1.6 million) by costs, which is a return-on-investment figure rather than the BCR. A ratio of 0.33:1 is the BCR turned upside down, and 1.6 is the net benefit in millions, not a ratio.

• A: This divides costs by benefits, the inverse of a BCR.
• B: $1.6 million is the net benefit, not a ratio of benefits to costs.
• C: Net benefits divided by costs is a return-on-investment figure, not the BCR.

Source: Midwest Community Tree Guide: Benefits, Costs, and Strategic Planting (PSW-GTR-199), USDA Forest Service, Pacific Southwest Research Station

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