Certified Arborist Test Trees and Construction 2 — Questions and Answers
Question 1: What is the Critical Root Zone (CRZ) and how is it typically calculated?
- The area directly under the canopy; measured by crown drip line
- A circular area around the trunk; typically 1 foot of radius per inch of trunk diameter (Correct answer)
- The top 2 inches of soil; measured by soil tests
- The area between the trunk and the first lateral root
Correct answer: A circular area around the trunk; typically 1 foot of radius per inch of trunk diameter
The CRZ is typically calculated as 1 foot of radius for each inch of trunk diameter at breast height (DBH). This area contains the most critical structural and absorbing roots.
Question 2: What is the most common cause of tree death during construction?
- Direct trunk damage from equipment
- Root damage from excavation, grade changes, and soil compaction (Correct answer)
- Paint or chemical spills on leaves
- Dust accumulation on foliage
Correct answer: Root damage from excavation, grade changes, and soil compaction
Root damage is the #1 killer. Construction activities sever roots through trenching, suffocate them through soil compaction and grade changes, and alter drainage patterns.
Question 3: How does soil compaction from construction equipment harm trees?
- It makes the soil too cold for roots
- It reduces soil pore space, limiting oxygen and water availability to roots (Correct answer)
- It increases soil fertility
- It only affects the appearance of the lawn, not the tree
Correct answer: It reduces soil pore space, limiting oxygen and water availability to roots
Heavy equipment compresses soil, collapsing the pore spaces that hold air and water. Roots need oxygen to function; compacted soil can effectively suffocate the root system.
Question 4: What type of barrier is most effective for protecting trees during construction?
- Caution tape around the trunk
- Chain-link or sturdy wooden fencing installed at the drip line or CRZ (Correct answer)
- Orange traffic cones around the tree
- A sign that says 'Do Not Disturb'
Correct answer: Chain-link or sturdy wooden fencing installed at the drip line or CRZ
Sturdy physical barriers (chain-link or wood fencing) at the CRZ or drip line are the most effective protection. They physically prevent equipment and material storage from entering the root zone.
Question 5: A builder needs to trench through a tree's root zone for a utility line. What is the preferred alternative method?
- Dig quickly to minimize time near roots
- Use directional boring (tunneling) to go under the root system (Correct answer)
- Cut only roots smaller than 2 inches
- Trench during winter when the tree is dormant
Correct answer: Use directional boring (tunneling) to go under the root system
Directional boring (horizontal directional drilling) tunnels beneath the root zone without disturbing roots or soil. This is the preferred method when utilities must pass through a CRZ.
Question 6: A tree shows crown dieback 2 years after nearby construction. Is this construction-related?
- No, 2 years is too long for construction damage to show
- Yes, tree decline from root damage often takes 2-7 years to manifest in the crown (Correct answer)
- Only if the tree was physically struck by equipment
- Only in evergreen species
Correct answer: Yes, tree decline from root damage often takes 2-7 years to manifest in the crown
Root damage symptoms are delayed because trees have stored energy reserves. Crown dieback, reduced leaf size, and branch death from construction damage typically appear 2-7 years after the damage occurs.
Certified Arborist Test Trees and Construction 2
What is the Critical Root Zone (CRZ) and how is it typically calculated?