ISA TRAQ key terms

A structured process for identifying, analyzing, and evaluating the likelihood and consequences of a tree or tree part failing and causing harm to people, property, or targets of value.

The combination of the likelihood that a hazardous event occurs and the severity of the consequences if it does, expressed qualitatively or quantitatively for a defined time period.

A condition, tree part, or situation with the potential to cause harm, such as a cracked limb over a sidewalk or a leaning tree near a building.

A person, property, or activity that could be injured or damaged if a tree or tree part fails, including vehicles, structures, utility lines, and pedestrians.

The probability that a tree or one of its parts will fail within a specified time frame, considering species, condition, loads, and site factors.

The severity of harm or damage that would result from a failure event, influenced by target type, exposure, and the energy or mass involved.

The breaking, uprooting, or loss of structural support of a tree or tree part, such as a stem, branch, or root, under applied loads.

A categorized or numeric expression of risk, commonly low, moderate, high, or extreme, derived by combining likelihood and consequence in a risk matrix.

A table that crosses likelihood categories with consequence categories to assign a risk rating, providing a consistent and repeatable framework for comparing trees.

The level of risk that a tree owner or manager is willing to accept for a given target and time period, based on values, liability, and available resources.

The risk that remains after mitigation measures are applied, which must be reassessed and communicated to the tree owner or manager.

An action taken to reduce the likelihood or consequence of failure, such as pruning, cabling, bracing, root zone protection, target relocation, or tree removal.

A limited visual inspection of a tree or population from ground level, often from a vehicle or walkway, used to screen for obvious defects and prioritize further assessment.

A basic visual assessment performed from the ground, including a 360-degree walk-around and closer inspection of the crown, trunk, and root collar, typically recorded on a standard form.

An advanced assessment using specialized tools or techniques, such as resistograph, sonic tomography, or climbing inspection, to evaluate specific structural concerns identified in lower-level assessments.

A visible or detectable flaw in a tree's form or wood that reduces its strength, such as a cavity, crack, included bark, decay, or weak branch union.

The decomposition of wood by fungi, which can reduce strength and create cavities, often assessed by extent, location, and whether it affects load-bearing tissue.

An open or enclosed hollow area in a trunk or branch caused by decay or injury, which may reduce cross-sectional strength depending on its size and position.

A longitudinal separation in wood fibers that can indicate a split or shear failure and often requires closer assessment or mitigation because it may propagate under load.

Bark trapped inside a branch union that prevents a strong wood connection, creating a weak attachment prone to splitting under wind or snow loads.

Two or more stems of similar diameter arising from the same point, often with included bark, which may form a weak union and require assessment or mitigation.

The point where a branch attaches to a stem or another branch, whose strength depends on the presence of a branch bark ridge and branch collar.

The swollen tissue at the base of a branch formed by overlapping wood and bark, which indicates a strong union and guides proper pruning cuts.

A raised strip of bark on the upper side of a branch union that marks the boundary between branch and stem tissue and helps identify the proper pruning location.

The ratio of sound wood thickness to radius in a stem with a cavity or decay, used as an indicator of remaining strength; lower ratios suggest greater concern.

The transition zone between the trunk and the root system, where decay, girdling roots, and planting defects are commonly assessed during a basic inspection.

A root that encircles or crosses over the root collar or other roots, potentially restricting water and nutrient transport and weakening the tree over time.

The mass of roots and soil that supports a tree and resists overturning, whose size and condition affect uprooting risk, especially when soils are saturated or disturbed.

Failure in which the root plate rotates or lifts and the tree overturns, often associated with shallow roots, wet soils, root decay, or high wind loads.

A force applied to a tree or tree part, such as wind, snow, ice, or gravity, that must be resisted by the wood and root system to avoid failure.

The force exerted by wind on a tree's crown and stem, influenced by crown density, exposure, height, and wind speed, and a major driver of failure.

The proportion of time that a target is present in the area where a failure could cause harm, used to estimate the likelihood of injury or damage.

The ongoing process of inventorying, assessing, prioritizing, mitigating, and monitoring tree risk across a population to meet the owner's objectives and tolerance.

A drilling device that measures resistance to a fine needle as it penetrates wood, producing a profile used to detect decay and internal defects.

A non-invasive technique that measures sound wave travel times through a stem to map internal decay, cavities, and wood quality.

A fruiting body of a wood-decay fungus, often visible on the trunk or roots, whose presence indicates internal decay and potential loss of strength.

The decrease in risk achieved by lowering the likelihood or consequence of failure through mitigation, monitoring, or removal of the target.