ISA AM flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Stocking level

Ratio of existing public trees to total available planting spaces; used to measure how fully a street tree program is populated and to target planting budgets.

Right tree, right place

Species selection principle matching mature size, root behavior, and site tolerances to available soil volume, overhead clearance, and utility conflicts before planting.

ANSI A300

American National Standard for Tree Care Operations; sets industry consensus practices for pruning, planting, fertilization, cabling, and integrated vegetation management.

Critical root zone

Soil area around a trunk that must be protected during construction; commonly defined as a radius of one foot per inch of trunk diameter.

Genus diversity target

Guideline limiting any single genus to roughly ten percent of a municipal tree population to reduce catastrophic loss from a host-specific pest or disease.

Municipal tree inventory

Database of public trees recording species, size, condition, location, and maintenance history; supports work-order prioritization, budgeting, and risk screening.

Structural pruning cycle

Recurring pruning of young trees every two to three years to establish a dominant leader and strong branch unions, reducing future failure risk.

Cost per tree maintained

Performance metric dividing annual maintenance spending by the number of trees serviced; used to benchmark program efficiency and justify budget requests.

CODIT wall 4

Barrier zone of suberized tissue formed by the cambium after wounding; the strongest compartmentalization wall and a key defense against decay spread.

Compartmentalization

Tree's internal process of isolating wounded or infected tissue through chemical and anatomical boundaries, preventing decay organisms from spreading into healthy wood.

Transpiration pull

Negative pressure generated by water loss at leaves that draws water up the xylem; failure under drought causes cavitation and embolism in vessels.

Ectomycorrhizae

Fungi forming a sheath around root tips, common on pines, oaks, and birches; they extend water and nutrient uptake, especially phosphorus, for the host tree.

Iron chlorosis

Yellowing of leaves between green veins caused by iron unavailability, typically on high-pH soils; treated with acidification, chelates, or species replacement.

Growth regulator

Synthetic compound such as paclobutrazol that shortens internodes and reduces shoot growth; may improve drought tolerance but does not cure disease.

Stomatal closure

Guard-cell response reducing gas exchange under drought or heat stress; limits water loss but also cuts carbon uptake before visible wilting appears.

Wound wood

New tissue formed by the cambium around a wound margin; it rolls over the injury and seals it, indicating active compartmentalization and recovery.

Tree risk formula

Risk equals likelihood of failure multiplied by likelihood of impact multiplied by consequence; no target means no risk in the ISA TRAQ framework.

Level 2 basic assessment

Ground-based 360-degree visual inspection of a tree and its site, documenting defects, targets, and recommended mitigation or advanced assessment.

Level 3 advanced assessment

Detailed inspection using aerial access or diagnostic tools such as resistograph, sonic tomography, or pull testing to quantify internal decay or stability.

Imminent failure likelihood

TRAQ rating indicating failure is expected within the assessment period under normal weather; requires immediate mitigation or exclusion of the target.

Target

Person, vehicle, structure, utility, or property within the potential fall zone of a tree; target presence and occupancy drive consequence ratings.

Sonic tomography

Stress-wave device measuring sound velocity through a trunk cross-section; slower velocities indicate decay or voids, producing a two-dimensional internal map.

Resistograph

Drill-mounted instrument measuring resistance to a fine needle as it advances through wood; resistance profiles reveal decay, cavities, and growth-ring density.

Residual risk

Risk remaining after mitigation measures are applied; must be documented and communicated to the tree owner or manager along with reassessment intervals.

Tree ordinance

Local law governing planting, removal, and protection of trees on public and sometimes private land; includes permits, mitigation ratios, and penalties.

Heritage tree

Tree formally designated for exceptional age, size, species, or historical significance; removal usually requires board review, public hearing, and mitigation plan.

Mitigation ratio

Required replacement trees or fee per tree removed during development; common ratios range from two-to-one to three-to-one depending on size and species.

Tree City USA

Arbor Day Foundation recognition requiring a tree board or department, a tree care ordinance, an annual program budget, and an Arbor Day observance.

Canopy cover goal

Policy target for the percentage of a city covered by tree crowns, often thirty to forty percent; measured by i-Tree Canopy, LiDAR, or photo sampling.

Tree board

Advisory commission appointed by the governing body; reviews policy, promotes education, and oversees grants rather than directing daily field operations.

Stormwater utility credit

Fee reduction granted to property owners who plant or retain trees that intercept rainfall, used as a funding and incentive mechanism for urban forestry.

Tree protection permit

Authorization required before removing or disturbing protected trees; workflow includes site plan review, arborist inspection, conditions, and follow-up compliance checks.