Certified Arborist Test Soil Science and Root Management 1

Question 1

Which soil texture has the smallest individual particle size and tends to retain the most water but drains poorly?

Accepted Answer

Clay

Answer

Clay particles are the smallest of the three primary soil separates (sand, silt, clay), giving clay soils a very high surface area that holds water tightly. This poor drainage can limit oxygen availability in the root zone and impede root development.

Question 2

What is the primary purpose of a soil percolation test in arboriculture?

Accepted Answer

To determine the rate at which water drains through the soil profile

Answer

A percolation test measures how quickly water moves downward through the soil profile. This tells arborists whether a site has adequate drainage to support healthy root respiration, since waterlogged soils deprive roots of oxygen.

Question 3

What is the critical root zone (CRZ) of a tree generally defined as?

Accepted Answer

A circular area with a radius of 1 foot per inch of trunk diameter

Answer

The critical root zone is typically calculated as a circular area with a radius of 1 foot for every inch of trunk diameter measured at breast height (DBH). This defines the minimum area around a tree that should be protected from disturbance during construction or other activities.

Question 4

Which of the following best describes a 'soil horizon'?

Accepted Answer

A distinct layer within a soil profile that differs in physical or chemical properties from adjacent layers

Answer

Soil horizons are distinct layers visible in a soil profile, each with its own texture, color, structure, and chemical composition. Understanding horizons helps arborists assess rooting depth potential, drainage characteristics, and nutrient availability at a site.

Question 5

What does soil pH primarily affect in the context of tree nutrition?

Accepted Answer

The availability of nutrients to tree roots

Answer

Soil pH controls the chemical form and solubility of nutrients, directly affecting how available they are for root uptake. For example, iron and manganese become less available at high pH (alkaline soils), while aluminum and manganese can reach toxic levels at very low pH (acidic soils).

Certified Arborist Test Practice Test

Certified Arborist Test Practice Test

Certified Arborist Test Soil Science and Root Management 1