Certified Arborist Test Urban Forestry and Tree Selection 3

Question 1

What is a urban tree inventory and how is it used in urban forest management?

Accepted Answer

A systematic data collection effort documenting individual trees' species, location, size, and condition — used for maintenance planning, budget allocation, ecosystem service valuation, and management decision-making

Answer

A complete urban tree inventory documents individual trees with geo-referenced data on species, DBH, canopy spread, structural condition, maintenance needs, and location characteristics — enabling data-driven management including maintenance prioritization, replacement planning, risk identification, and ecosystem service valuation.

Question 2

What is a 'structural soil' system (e.g., CU-Structural Soil) and why was it developed for urban tree planting?

Accepted Answer

A pavement-compatible growing medium that supports traffic loads above while providing uncompacted root growing space below — engineered to resolve the incompatibility between soil compaction requirements for pavement and soil porosity requirements for roots

Answer

CU-Structural Soil (developed at Cornell University) and similar systems blend gravel with small quantities of clay-loam soil to create a load-bearing medium that satisfies pavement subbase compaction requirements while maintaining sufficient macro-porosity for root growth — solving the fundamental conflict between impervious surface construction and tree root survival.

Question 3

What role does species diversity play in urban forest resilience, and what is the 10-20-30 rule?

Accepted Answer

Diversity reduces vulnerability to catastrophic loss from pests and diseases; the 10-20-30 rule recommends no more than 10% of trees in any single species, 20% in any genus, and 30% in any family

Answer

Species diversity is the primary hedge against catastrophic loss from host-specific pests and diseases. The 10-20-30 rule (Santamour, 1990) recommends not exceeding 10% for any single species, 20% for any genus, and 30% for any family — creating a portfolio that limits how much of the forest any single pathogen or pest can affect.

Question 4

What is a tree protection zone (TPZ) specification in development projects, and how does it differ from the critical root zone (CRZ)?

Accepted Answer

The CRZ is the calculated minimum area of root zone requiring protection; the TPZ may be larger than the CRZ, expanded based on tree species, age, health, or site conditions to provide an adequate buffer zone for preservation

Answer

The CRZ (typically 1 foot radius per inch DBH) provides a minimum calculated threshold; the TPZ is the actual exclusion zone specified in a tree protection plan, which may be larger than the CRZ when a tree's species characteristics, health, or site position justifies additional protection beyond the minimum formula.

Question 5

What are the primary considerations when selecting trees for planting under or near overhead utility lines?

Accepted Answer

Trees should be selected with mature heights that keep them below utility line clearance requirements, avoiding the need for repeated utility pruning that damages tree structure

Answer

The most effective strategy for managing tree-utility line conflicts is prevention through selection of species whose mature height remains below the required clearance threshold, eliminating the need for repeated utility pruning that disfigures tree structure and creates ongoing hazards.

Certified Arborist Test Practice Test

Certified Arborist Test Practice Test

Certified Arborist Test Urban Forestry and Tree Selection 3