12. TREE RISK ASSESSMENT WORKBOOK

Question 1

List the two components of risk.

Answer 1

a. Likelihood
b. Consequences

Question 2

In tree risk assessment, likelihood is a combination of _______ and _______.

Answer 2

Likelihood of impact and likelihood of failure

Question 3

List the three levels of assessment.

Answer 3

a. Limited Visual Assessment
b. Basic Assessment
c. Advanced Assessment

Question 4

_______ 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.

Answer 4

Targets, target zone

Question 5

Targets can be categorized by the amount of time that they are within the target zone— their _______.

Answer 5

Occupancy rate

Question 6

Without a stated _______ _______, the rating for likelihood of failure is meaningless.

Answer 6

Time frame (1 to 3 years)

Question 7

_______ _______ fungi primarily decay the lignin within and between cell walls in the wood, reducing the wood’s stiffness but leaving some flexibility.

Answer 7

White rot

Question 8

_______ _______ gets its name because, after the cellulose is decayed, the remaining lignin is dark or brown in color.

Answer 8

Brown rot

Question 9

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.

Answer 9

True

Question 10

_______ _______ is new wood produced in response to damage or loads.

Answer 10

Response growth

Question 11

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.

Answer 11

True

Question 12

True/False—Woundwood is less dense than and chemically different from other wood, and it resists decay better than normal wood.

Answer 12

False

Question 13

Two advanced assessment devices/techniques of assessing internal decay are _______ _______ and _______ _______.

Answer 13

Resistance-recording drill, Sonic tomography

Question 14

True/False—Each combination of a failure mode and a target represents a separate risk to analyze.

Answer 14

True

Question 15

True/False—The overall tree risk is the risk of whole tree failure.

Answer 15

False

Question 16

_______ _______ 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.

Answer 16

Acceptable risk

Question 17

The risk remaining after mitigation is the _______ _______.

Answer 17

Residual risk

Question 18

True/False—Once the highest risk factor has been mitigated, the tree risk rating goes to the next highest risk factor.

Answer 18

True

Question 19

True/False—The tree risk assessor bears the responsibility for tree risk management.

Answer 19

False

Question 20

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

Answer 20

a. climbing the tree

Question 21

Which type of decay primarily affects the lignin within and between cell walls in the wood, reducing the tree’s strength under compression?

Answer 21

b. white rot

Question 22

Trees that lean because of ground failure or root injury:

Answer 22

a. have a high potential to fail

Question 23

Which of the following is the responsibility of a tree risk assessor?

Answer 23

b. presenting mitigation options

Question 24

Known collectively as reaction wood?

Answer 24

Compression wood and Tension wood.

Question 25

When trees sway in the wind they produce ______ _____ near the base to help support the trunk.

Answer 25

Flexure Wood

Question 26

Most common in conifer trees and primarily decays the cellulose leaving behind stiff lignin and reducing the bending strength of a tree.

Answer 26

Brown Rot

Question 27

Primarily decays the lignin within and between cell walls in wood. Reduces the trees stiffness and compressive strength.

Answer 27

White Rot

Question 28

Produced in response to cambial damage and is typically denser than and chemically different from other wood. It resists decay better than normal wood.

Answer 28

Woundwood

Question 29

Crack in a tree that forms across the short axis of the trunk, stem, or root. Often indicate that failure is imminent.

Answer 29

Transverse Cracks

Question 30

Cracks that commonly occur when branches are overloaded by freezing rain, snow or wind, not typically prone to failure.

Answer 30

Shear Plane Cracks (Neutral plane failures)

Question 31

Determined by examining structural conditions, defects, response growth, and anticipated loads.

Answer 31

Likelihood of Failure

Question 32

The amount of damage depends on the part size, distance of fall and protection factors.

Answer 32

Consequences of Failure

Question 33

Tree reaction to the presence of decay varies. The two fundamental strategies are ________ & _________.

Answer 33

Compartmentilzation & Growth

Question 34

Symptoms or signs that decay may be present. Cracks, bulges, and wounds from old pruning cuts.

Answer 34

Potential Indicators

Question 35

Whos bears the responsibility for tree risk management?

Answer 35

Tree owners or managers

Question 36

Arborists often report an overall tree risk rating which identifies the failure ______/______ combinations asssesed.

Answer 36

Mode/Target