ISA Soil and Water Management 2

Question 1

What is the primary concern with overwatering established landscape trees?

Accepted Answer

It saturates the root zone, displacing oxygen and creating anaerobic conditions that lead to root suffocation and disease

Answer

Overwatering fills soil pore spaces with water, displacing the oxygen that roots need for aerobic respiration. Extended saturated conditions lead to root death, root rot diseases (particularly Phytophthora), and progressive decline.

Question 2

How does a perched water table form and why is it problematic for tree root health?

Accepted Answer

It occurs at the interface between two soil layers of different texture, trapping water above the finer-textured layer and saturating roots in that zone

Answer

A perched water table forms when water moving downward through soil encounters an abrupt textural change (e.g., sand over clay), causing water to accumulate at the interface. This saturated zone suffocates roots growing at that depth.

Question 3

What is the recommended method for irrigating newly transplanted trees during their establishment period?

Accepted Answer

Deep, infrequent watering that moistens the entire root ball and surrounding soil, gradually reducing frequency as roots establish

Answer

Newly transplanted trees should receive deep watering that thoroughly moistens the root ball and surrounding backfill soil. Frequency should be higher initially (2-3 times per week) then gradually reduced to encourage root exploration into surrounding soil.

Question 4

How does road salt (sodium chloride) damage trees growing along roadways?

Accepted Answer

It increases soil sodium levels causing clay dispersion and poor drainage, draws water from roots through osmosis, and direct spray causes foliar desiccation

Answer

Road salt damages trees through multiple pathways: soil sodium causes clay particles to disperse (destroying structure), salt in soil water draws water out of roots through osmosis, and salt spray on foliage causes desiccation and tissue death.

Question 5

What is the relationship between soil texture and plant-available water holding capacity?

Accepted Answer

Loam soils hold the most plant-available water because they balance drainage and retention better than sand or clay

Answer

Loam soils (balanced mix of sand, silt, and clay) hold the most plant-available water. While clay soils hold more total water, much of it is held too tightly for roots to extract. Sandy soils drain too quickly to retain much available water.

(ISA) ISA Certified Arborist Practice Test

(ISA) ISA Certified Arborist Practice Test

ISA Soil and Water Management 2