CATS Urban Tree Risk Assessment & Mitigation 3

Question 1

Which failure mode is described as the separation of a branch or stem at a point other than a union or attachment point?

Accepted Answer

Stem failure

Answer

Stem failure (also called mid-stem or trunk failure) occurs when wood fractures along the stem rather than at a branch union or root plate.

Question 2

When calculating the modified Mattheck ratio (t/R) for a hollow tree, what minimum wall thickness ratio is generally considered the threshold for structural concern?

Accepted Answer

0.30

Answer

A t/R ratio below 0.30 (wall thickness less than 30% of the trunk radius) is generally considered a threshold where structural integrity is compromised.

Question 3

A large Siberian elm on a residential street in Albuquerque shows signs of lion-tailing. Which risk does this create?

Accepted Answer

Weight distribution shifted to branch ends increasing failure risk

Answer

Lion-tailing removes interior foliage and shifts weight to branch tips, creating lever-arm stress that increases the risk of branch failure.

Question 4

Which type of wound closure pattern best indicates a tree's capacity for compartmentalization?

Accepted Answer

Rapid formation of reaction zone and woundwood

Answer

Rapid formation of a reaction zone and expanding woundwood callus indicates active CODIT (Compartmentalization of Decay in Trees) response.

Question 5

An arborist notes a sudden lean in a previously upright Albuquerque tree after a monsoon rainfall event. The most urgent concern is:

Accepted Answer

Root system failure

Answer

A sudden lean following soil saturation indicates possible root plate failure or soil heave, requiring immediate assessment and likely removal.

(CATS) Certified Arborist Tree Service of Albuquerque Practice Test

(CATS) Certified Arborist Tree Service of Albuquerque Practice Test

CATS Urban Tree Risk Assessment & Mitigation 3