ISA Soil Science and Management 2

Question 1

What soil pH range is generally considered optimal for most landscape trees?

Accepted Answer

5.5-7.0

Answer

Most landscape trees grow best in slightly acidic to neutral soil, with a pH range of approximately 5.5-7.0. This range allows optimal availability of essential nutrients.

Question 2

What is the primary purpose of mycorrhizal fungi in relation to tree root systems?

Accepted Answer

They form symbiotic associations with roots, dramatically extending the nutrient and water absorption network

Answer

Mycorrhizal fungi form symbiotic relationships with tree roots, extending their hyphal networks far beyond the root zone to access water and nutrients — particularly phosphorus — in exchange for carbohydrates from the tree.

Question 3

What does a soil bulk density measurement indicate about growing conditions for tree roots?

Accepted Answer

The degree of soil compaction, which affects root penetration, aeration, and water infiltration

Answer

Bulk density measures the weight of dry soil per unit volume. Higher values indicate greater compaction, which restricts root growth, reduces pore space for air and water, and limits biological activity.

Question 4

Why is vertical mulching sometimes recommended for trees in compacted urban soils?

Accepted Answer

To create channels in compacted soil that improve aeration, water infiltration, and root growth opportunities

Answer

Vertical mulching involves drilling holes into compacted soil and filling them with organic matter or porous material, creating channels that improve oxygen availability, water movement, and root exploration into otherwise impenetrable soil.

Question 5

What is cation exchange capacity (CEC) and why is it important for tree nutrition?

Accepted Answer

The soil's ability to hold and exchange positively charged nutrient ions on particle surfaces

Answer

CEC measures the soil's capacity to hold positively charged ions (cations) such as calcium, magnesium, potassium, and ammonium on clay and organic matter surfaces, making them available for root uptake.

(ISA) ISA Certified Arborist Practice Test

(ISA) ISA Certified Arborist Practice Test

ISA Soil Science and Management 2