ISA Soil and Water Management Questions and Answers

Question 1

An arborist inspects a mature street tree in a heavily used urban plaza. The soil is hard-packed, and the tree exhibits stunted growth, sparse foliage, and some branch dieback. These symptoms are most likely the primary result of which soil condition?

Accepted Answer

Reduced pore space limiting oxygen and water availability

Answer

Heavy foot and vehicle traffic in urban areas leads to soil compaction. Compaction reduces total pore space, especially the large macropores responsible for air exchange and water movement. This deprives roots of the oxygen necessary for respiration and water absorption, leading to stress symptoms like stunted growth and dieback.

Question 2

Which of the following statements best distinguishes between soil texture and soil structure?

Accepted Answer

Texture refers to the proportion of sand, silt, and clay, while structure describes how these particles are arranged into aggregates.

Answer

Soil texture is an inherent property determined by the relative percentages of sand, silt, and clay particles. Soil structure refers to the arrangement and binding of these particles into clumps or aggregates. While texture is largely permanent, good soil structure can be developed or destroyed through management practices.

Question 3

A homeowner wants to ensure the survival of a newly planted tree during its first dry summer. What is the most effective irrigation practice an arborist should recommend?

Accepted Answer

Apply water deeply and infrequently, thoroughly soaking the root ball and surrounding soil.

Answer

Deep, infrequent watering encourages the tree's roots to grow deeper into the soil profile, creating a more extensive and drought-tolerant root system. Shallow, frequent watering promotes a weak, shallow root system that is more vulnerable to drying out.

Question 4

The amount of water held in the soil after the excess has drained away due to gravity, which is considered the ideal state for plant water uptake, is known as:

Accepted Answer

Field capacity

Answer

Field capacity is the term used to describe the amount of soil moisture or water content held in soil after excess water has drained away and the rate of downward movement has materially decreased. At this point, the soil's micropores are filled with water and the macropores are filled with air, which is optimal for root function.

Question 5

A client's property has a low-lying area with heavy clay soil where a maple tree is failing to thrive, showing yellowed leaves and poor growth. The ground remains saturated for several days after rainfall. Which action would provide the most effective long-term solution?

Accepted Answer

Install a French drain or grade the area to redirect surface water away from the tree.

Answer

The core problem is poor drainage causing waterlogged soil, which deprives roots of oxygen. The most effective long-term solution is to physically alter the site to remove excess water, such as by installing a French drain or regrading the surface to create a swale. Fertilizing, pruning, or adding sand will not resolve the underlying issue of soil saturation.

(ISA) ISA Certified Arborist Practice Test

(ISA) ISA Certified Arborist Practice Test

ISA Soil and Water Management Questions and Answers