12. TREE RISK ASSESSMENT WORKBOOK Flashcards
List the two components of risk.
a. Likelihood
b. Consequences
In tree risk assessment, likelihood is a combination of _______ and _______.
Likelihood of impact and likelihood of failure
List the three levels of assessment.
a. Limited Visual Assessment
b. Basic Assessment
c. Advanced Assessment
_______ are people, property, or activities that could be injured, damaged, or disrupted by a tree failure. The _______ is the area that the tree or branch is likely to hit if it fails.
Targets, target zone
Targets can be categorized by the amount of time that they are within the target zone— their _______.
Occupancy rate
Without a stated _______ _______, the rating for likelihood of failure is meaningless.
Time frame (1 to 3 years)
_______ _______ fungi primarily decay the lignin within and between cell walls in the wood, reducing the wood’s stiffness but leaving some flexibility.
White rot
_______ _______ gets its name because, after the cellulose is decayed, the remaining lignin is dark or brown in color.
Brown rot
True/False—A tree may appear to be solid and structurally sound or may have a thick, green crown yet can have significant decay inside.
True
_______ _______ is new wood produced in response to damage or loads.
Response growth
True/False—As trees grow and develop, they adapt to the various loads that they experience (gravity and wind) by developing wood where it is needed to support the loads.
True
True/False—Woundwood is less dense than and chemically different from other wood, and it resists decay better than normal wood.
False
Two advanced assessment devices/techniques of assessing internal decay are _______ _______ and _______ _______.
Resistance-recording drill, Sonic tomography
True/False—Each combination of a failure mode and a target represents a separate risk to analyze.
True
True/False—The overall tree risk is the risk of whole tree failure.
False
_______ _______ is the degree of risk that is within the owner’s/manager’s or controlling authority’s tolerance, or that which is below a defined threshold.
Acceptable risk
The risk remaining after mitigation is the _______ _______.
Residual risk
True/False—Once the highest risk factor has been mitigated, the tree risk rating goes to the next highest risk factor.
True
True/False—The tree risk assessor bears the responsibility for tree risk management.
False
Which of the following is not a type of Level 1 assessment? a. climbing the tree b. walk-by c. drive-by d. aerial patrol
a. climbing the tree
Which type of decay primarily affects the lignin within and between cell walls in the wood, reducing the tree’s strength under compression?
b. white rot
Trees that lean because of ground failure or root injury:
a. have a high potential to fail
Which of the following is the responsibility of a tree risk assessor?
b. presenting mitigation options
Known collectively as reaction wood?
Compression wood and Tension wood.
When trees sway in the wind they produce ______ _____ near the base to help support the trunk.
Flexure Wood
Most common in conifer trees and primarily decays the cellulose leaving behind stiff lignin and reducing the bending strength of a tree.
Brown Rot
Primarily decays the lignin within and between cell walls in wood. Reduces the trees stiffness and compressive strength.
White Rot
Produced in response to cambial damage and is typically denser than and chemically different from other wood. It resists decay better than normal wood.
Woundwood
Crack in a tree that forms across the short axis of the trunk, stem, or root. Often indicate that failure is imminent.
Transverse Cracks
Cracks that commonly occur when branches are overloaded by freezing rain, snow or wind, not typically prone to failure.
Shear Plane Cracks (Neutral plane failures)
Determined by examining structural conditions, defects, response growth, and anticipated loads.
Likelihood of Failure
The amount of damage depends on the part size, distance of fall and protection factors.
Consequences of Failure
Tree reaction to the presence of decay varies. The two fundamental strategies are ________ & _________.
Compartmentilzation & Growth
Symptoms or signs that decay may be present. Cracks, bulges, and wounds from old pruning cuts.
Potential Indicators
Whos bears the responsibility for tree risk management?
Tree owners or managers
Arborists often report an overall tree risk rating which identifies the failure ______/______ combinations asssesed.
Mode/Target
