ISA AM cheat sheet

Municipal tree inventory data elements typically include species, DBH, condition rating, location (address/GPS), maintenance history, and risk rating; inventories drive work-order prioritization and budget justification.

Right tree, right place: match mature canopy and root spread to planting space; minimum soil volume rules of thumb range from about 1 m³ per 1 m² of canopy projection up to 2-3 m³ per 1 m² for large shade trees in engineered soils.

ANSI A300 (Tree Care Operations) sets standard practices for pruning, fertilization, cabling, and planting; ANSI Z133 covers safety. Best Management Practices (BMP) companion documents translate standards into field procedures.

Pruning cycles: structural pruning of young trees every 2-3 years; mature tree maintenance pruning commonly on 5-7 year cycles depending on species and site.

Species diversity target: no single genus above ~10% and no single species above ~5% of the public tree population (common urban forestry guideline) to limit pest/disease catastrophe.

Stocking level = number of trees present divided by number of planting spaces available; typical municipal street stocking levels run 60-80% in well-managed programs.

Tree protection during construction: critical root zone (CRZ) radius often set at 1 foot (0.3 m) per inch DBH, or 1.5x the canopy radius; fencing must be installed before demolition/grade change.

Work-order systems should record tree ID, task code, crew hours, and completion date; cost per tree maintained and cost per tree planted are standard performance metrics reported to councils.

CODIT model: four walls - wall 1 plugs xylem vessels, wall 2 reinforces inner annual rings, wall 3 blocks ray parenchyma, wall 4 forms new barrier zone (suberin) in cambium; wall 4 is the strongest defense.

Compartmentalization is strongest in species with dense, compartmented wood (e.g., oaks, elms, ginkgo) and weakest in species that bleed or form wetwood (e.g., willows, poplars, birches).

Photosynthesis: 6CO2 + 6H2O + light → C6H12O6 + 6O2; stomata regulate gas exchange and close under drought stress, reducing carbon gain before visible wilt.

Tree water transport: transpiration pull through xylem driven by leaf water potential; cavitation/embolism risk rises when soil water drops and vapor pressure deficit is high.

Mycorrhizae: ectomycorrhizae dominate on pines, oaks, birches; arbuscular mycorrhizae on maples, sycamores, and most tropical species. They extend effective root surface for water and phosphorus uptake.

Chlorosis on high-pH soils is usually iron or manganese deficiency; treat with soil acidification, chelated iron, or species substitution rather than nitrogen fertilizer.

Growth regulators (e.g., paclobutrazol, uniconazole) reduce internode elongation and can improve drought tolerance but must be applied at labeled rates; they do not cure disease.

Bark damage from string trimmers and mowers creates entry courts for decay fungi; maintaining a 1-3 m vegetation-free ring around the trunk is a standard preventive practice.

Risk = likelihood of failure × likelihood of impact × consequence; a tree with high failure likelihood but no target has zero risk under the ISA TRAQ framework.

TRAQ levels of assessment: Level 1 limited visual (walk-by), Level 2 basic (360° visual from ground), Level 3 advanced (aerial, resistograph, sonic tomography, pull test).

Targets: people, vehicles, structures, utilities, and other trees within the potential fall zone. Target value and occupancy drive consequence rating.

Failure likelihood ratings in TRAQ: improbable, possible, likely, and imminent - each with defined probability ranges (e.g., imminent = failure expected within the assessment period under normal weather).

Tree part failure modes: whole-tree uprooting, root/soil failure, trunk buckling, branch failure (union or mid-limb), and crown loss. Each has distinct diagnostic indicators.

Mitigation options ranked: (1) move/remove target, (2) remove tree, (3) prune to reduce load or clearance, (4) support with cables/bracing, (5) monitor and reassess. Document residual risk after each.

Decay detection: resistograph (drilling resistance), sonic tomography (stress-wave velocity), and visual indicators (conks, cavities, seams, bark cracks). No single tool is definitive; combine with species failure profile.

Reassessment interval should reflect risk rating: imminent = days to weeks; likely = months; possible = annually or per cycle; document the rationale.

Tree ordinance components: purpose, definitions, jurisdiction, permit requirements for removal/pruning, tree protection during development, mitigation ratios (e.g., 2:1 or 3:1 replacement), and enforcement/penalties.

Heritage/landmark tree designation usually requires a nomination, review by an urban forestry board, and public hearing; removal typically requires council approval and mitigation plan.

Municipal tree board or commission: advisory body appointed by the governing body; typical duties include policy review, public education, and grant oversight (not day-to-day operations).

Tree canopy goals: many cities adopt 30-40% canopy cover targets; measurement via i-Tree Canopy, LiDAR, or aerial photo sampling, with equity analysis by census tract.

Funding models: general fund, stormwater utility credits, tree mitigation fees, grants (e.g., USDA Forest Service Urban & Community Forestry), and public-private partnerships.

Tree City USA recognition requires four standards: a tree board or department, a tree care ordinance, a community forestry program with annual budget of at least $2 per capita, and an Arbor Day observance/proclamation.

Permit workflow: application → site plan review → arborist inspection → decision (approve/deny/condition) → mitigation bond or fee → follow-up inspection; timelines and appeal rights must be specified.

Emergency response policy: pre-identified priority routes, mutual aid agreements, debris management contracts, and post-storm damage assessment protocols should be adopted before the event.