Trees and Construction Practice Questions

Correct answer: B. At the start of planning, before the site design is set

Purdue Extension and the Texas A&M Forest Service both say the arborist should be involved from the very beginning of the planning phase, because small changes in where a building, driveway or utility line goes can decide whether a tree survives. Waiting until fences go up is the tempting answer, but by then the site design is fixed and many conflicts can no longer be designed out. Arriving after clearing or after construction usually means the damage is already done.

• A: By the time clearing is finished, the layout is set and root zones may already be disturbed.
• C: Fencing comes after design decisions that the arborist should already have helped shape.
• D: After construction the arborist can only assess and treat damage that planning might have prevented.

Sources: Construction and Trees: Guidelines for Protection (FNR-463-W), Purdue Extension ; Protect Tree Roots During Construction, Texas A&M Forest Service

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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. Keep the fences until every crew, landscapers included, has left

The Texas A&M Forest Service advises that protective fences stay up until every construction worker has left the site, and landscape crews are part of that work. Mississippi State University Extension warns that sensitive root zones can still be disturbed by late-stage landscaping, like laying sod, putting in irrigation or planting beds. Taking the fences down because the heavy work is over is the common mistake; extra watering cannot undo trenching, fill or compaction.

• B: Landscaping still brings trenching, added soil and traffic that can injure roots.
• C: Flagging tape is not a physical barrier and does not keep equipment or materials out.
• D: Watering cannot make up for root damage from irrigation trenches, fill or compaction.

Sources: Protect Tree Roots During Construction, Texas A&M Forest Service ; Preserving Trees in Construction Sites (Publication 2339), Mississippi State University Extension Service

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Correct answer: C. A tree with trunk rot that leans over the planned house

The Texas A&M Forest Service lists trunk rot, poor form and a heavy lean over future buildings among the traits of trees that should not be preserved, and NC State Extension advises removing damaged or diseased trees before construction begins. A tree that needs clearance pruning is not a poor candidate, because an arborist can prune it before work starts. Young, vigorous trees and sound trees that can be protected as a group are among the best candidates to keep.

• A: A young, vigorous tree well away from the work is a good candidate to keep.
• B: Clearance pruning before construction is routine and does not make a tree a poor candidate.
• D: Sound trees that can be protected together in one zone are good candidates.

Sources: Protect Tree Roots During Construction, Texas A&M Forest Service ; Construction and Tree Protection (AG-685), NC State Extension

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Correct answer: D. Soil compaction

Minnesota DNR identifies soil compaction as the main reason trees are lost after construction, and the USDA Forest Service says it kills more trees in construction areas than any other single cause. Compaction squeezes out the pore space roots need for air and water, and it can cover large areas through equipment traffic, parking and stockpiled materials. Bark wounds are the most common above-ground injury, which makes them a tempting answer, but they are not the leading cause of tree death.

• A: Trunk wounds are the most common above-ground injury, but compaction kills more trees.
• B: Chemical spills can harm roots where they occur but are not the leading cause of loss.
• C: Sunscald can injure newly exposed thin bark, but it is not the main cause of tree loss.

Sources: BMPs to Protect Trees at the Lot Level: New Construction, Remodeling & Redevelopment, Minnesota Department of Natural Resources ; 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: D. Mostly in the upper soil, roughly the top 18 inches

Mississippi State University Extension says a tree has about 85 percent of its roots in the upper 18 inches of soil, and the USDA Forest Service adds that more than half of the root system is in the top foot. That is why scraping, filling and compacting the soil surface do so much harm. Most mature trees do not depend on a deep taproot, and their roots spread far out from the trunk instead of staying under the center of the crown.

• A: Most mature trees do not depend on a deep taproot; the bulk of the root system is shallow.
• B: Few roots grow that deep; most are in the upper foot or so of soil.
• C: Roots spread widely, often well beyond the dripline, rather than staying near the trunk.

Sources: Preserving Trees in Construction Sites (Publication 2339), Mississippi State University Extension Service ; 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: C. Symptoms often take years to appear, so keep monitoring

Purdue Extension notes that trees damaged during construction may take years to show symptoms, and Minnesota DNR says soil compaction is likely to kill affected trees within two to five years. A tree may leaf out normally for a season or more even after losing roots or growing in compacted soil, so a healthy-looking first summer proves little. That delay is why post-construction monitoring continues for several years.

• A: Normal leaf-out does not rule out root damage; decline can lag by years.
• B: Construction damage often takes years, not weeks, to show.
• D: A full crown now does not mean the tree has recovered; symptoms can still develop later.

Sources: Construction and Trees: Guidelines for Protection (FNR-463-W), Purdue Extension ; BMPs to Protect Trees at the Lot Level: New Construction, Remodeling & Redevelopment, Minnesota Department of Natural Resources

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Correct answer: C. An air-powered excavation tool (air spade)

In national cemeteries, the National Park Service has eased soil compaction around tree roots with an air-powered excavation spade, because the tool loosens soil without harming the roots and lets air and water move more freely. Tillers, subsoilers and trenchers all break up soil mechanically and cut or tear the roots in their path. A subsoiler may seem attractive because it reaches deeper compaction, but it rips through the shallow root system.

• A: Tilling chops up the shallow roots throughout the area it works.
• B: Ripping tears through the roots in the upper foot or so of soil.
• D: A trencher severs every root in each slot it cuts.

Source: Relieving Compaction around Tree Roots, U.S. National Park Service

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Correct answer: D. At least 1 inch a week, applied by deep soaking

Oregon State University Extension's advice for the period after construction is to give at least 1 inch of water a week through deep soaking whenever rainfall is not adequate. Deep watering moistens the soil where the roots are; a light daily sprinkle, the tempting option, wets mostly the surface. Waiting for wilting means the tree is already under water stress, and a single late-season soaking does nothing for the summer dry spell.

• A: Light daily sprinkling wets mostly the surface and misses much of the root zone.
• B: Wilting means the tree is already under water stress.
• C: One late soaking does nothing for drought stress during the summer.

Source: Protecting Trees on Construction and Development Sites: Best Management Practices for the Pacific Northwest (EM 8994), Oregon State University Extension Service

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Correct answer: B. Remove the loose bark and smooth the ragged edges

Mississippi State University Extension advises removing loose bark from ragged wounds and smoothing the rough edges with a saw, knife or chisel, then letting the tree seal the wound naturally. Tree paint is the tempting choice, but the same publication explains that such products impede callus formation and compartmentalization and can seal in moisture that encourages decay. Plastic wraps and foam fillers also hold moisture against the wound and do not stop decay.

• A: Wound paints impede callus formation and can seal in moisture that favors decay.
• C: Trapping moisture against the wound encourages decay rather than preventing it.
• D: Fillers do not stop decay and can interfere with the tree's own wound response.

Sources: Tree Wounds: Should They Be Repaired? (Publication 3533), Mississippi State University Extension Service ; Tree Wounds: Should They Be Repaired? (Publication 3533), Mississippi State University Extension Service

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