Certified Arborist Test Soil Science and Root Management 3

Question 1

What is the approximate percentage of a tree's root system that typically extends beyond the drip line?

Accepted Answer

Most roots remain within the drip line but a significant portion extends 2-3 times the drip line radius

Answer

Tree root systems routinely extend 2-3 times the radius of the crown drip line and sometimes much farther, meaning the critical root zone is far larger than commonly assumed from crown spread alone.

Question 2

What is the purpose of a percolation test (perc test) in tree planting site assessment?

Accepted Answer

Determining how quickly water drains through the soil to assess drainage suitability

Answer

A percolation test measures the rate at which water drains through soil — critical for tree site assessment because both excessively fast drainage (droughty sandy soils) and slow drainage (poorly drained sites with waterlogging risk) affect tree species selection and soil preparation needs.

Question 3

What is the difference between nutrient deficiency and nutrient toxicity symptoms, and which is more commonly encountered in urban trees?

Accepted Answer

Deficiency causes chlorosis or stunting from insufficient supply; toxicity causes burn or necrosis from excess — deficiency is more common but both occur in urban settings

Answer

Nutrient deficiency symptoms reflect metabolic failure from insufficient supply (chlorosis, small leaves, reduced growth), while toxicity causes cellular damage from excess accumulation (marginal burn, tip necrosis). Both occur in urban trees, but deficiency due to compaction, pH imbalance, and root restriction is more prevalent.

Question 4

What is the 'critical root zone' (CRZ) and how is it calculated for construction site tree protection?

Accepted Answer

A radius calculated as 1 foot per inch of trunk diameter (DBH), representing the minimum area requiring protection

Answer

The CRZ is calculated as a radius of 1 foot per inch of trunk DBH, establishing a minimum exclusion boundary for construction activities. This provides a practical, proportional estimate for protecting enough of the root system to sustain the tree during and after construction.

Question 5

What is the purpose of soil pH management in tree care, and what are the two most common methods for lowering soil pH?

Accepted Answer

pH management improves nutrient availability; methods are elemental sulfur and acidifying nitrogen fertilizers (ammonium sulfate)

Answer

Soil pH directly controls the chemical availability of many nutrients — particularly micronutrients like iron, manganese, and zinc that become insoluble at high pH. Elemental sulfur (oxidized to sulfuric acid by bacteria) and acidifying fertilizers like ammonium sulfate are the primary methods for lowering pH in alkaline soils.

Certified Arborist Test Practice Test

Certified Arborist Test Practice Test

Certified Arborist Test Soil Science and Root Management 3