UFOR 300 final exam

What are the two types of load? What do they do?

Dynamic: Changing, variable forces on a tree (Wind, impact forces, animals, swaying motion of tree and branches)

Static: Constant, unchanging forces on the tree (Gravity, weight on the tree itself, snow and ice, signs and other objects on the tree)

Both of these loads can cause tree failure

Formula for dynamic load

Bending moment (M) = Force (F) x Lever Arm Length (L)

Which level of tree risk assessment form is the ISA designed for?

Level 2- basic

What is the target zone radius?

1.5 x the height of the tree

Steps for risk assessment (basic, level 2)

1. 360 degree tree check

2. Target assessment (Refer to scope of work, discuss with risk manager, timeframe), identify target zone (where the tree falls), identify occupancy rate, is the target movable?

3. Site assessment (Wind exposure, recent site changes (construction, soil excavation, removal of adjacent trees), regional weather conditions, topography (slope, aspect), soil (depth, drainage) root restrictions, evidence of nearby failures (root failures)

4. Likelihood of failure (Improbable, possible, probable, imminent)

5. Likelihood of impact (Very low, low, medium, high)

6. Likelihood of failure and impact

7. Mix the results o8f likelihood of failure and likelihood of impact with consequences of failure and impact

8. Mitigation strategy

What do decay tools do?

They do not tell you if the tree is likely to fail, or how to manage risks. Rather, they help you Which is used to detect locations of decay. Which is used to analyze the health of the whoel tree

What are some risk assessment tools?

Resistance drilling- drills a hole in the tree and makes a graph based on the wood quality of the tree- gives small portion of tree

Sonic topography - hangs the device around the tree, you then hammer some nails connected to the device, and demonstrates the results of the tree on the device - gives a small portion of the tree

Static pull test - tests how wind firm a tree is by attach a elastoeter on the trunk of the tree, measuring compression + tension forces, and a pulley wire (winch) to apply a large force, simulating wind, to to determine data.

Cable

-Support systems that uses wires or ropes between branches

Brace rods

Threaded with steel rods fastened with nuts, reinforces cracks and provides additional strength

Guys

Support systems using wire or rope run from tree to soil or anchor tree

Prop

Support system using rigid structures to support weight from below

What is risk mitigation in arboriculture defined as?

An action taken to reduce risk

How does tree-based mitigiation rwork?

It reduces the likelihood of failure and/or impact

What is a way for target-based mitigation actions in the public city?

Rerouting pedestrian traffic

When is “retain and monitor” used?

When tree mitigation is not necessary

How can pruning reduce risk?

By reducing branch length and/or density

Why are support systems used?

To limit movement to reduce breakage likelihood

What is the primary goal of a cable in codominnt stems?

Restrict movement before reaching critical angles that cause failures of trees

When installing a cable in a tree, the standard attachment height is:

Two-thirds of the stem length above the union

For over-extended branches, cable should anchor aproximately

40-50% of the branch length

Extra High Strength (EHS)cable has:

-The highest tensile strength among common cable types listed

How long should fiber (rope) cabling systems be generally considered for?

Short term (<5 year) systems with annual inspection

When should brace rods be used?

Cracks are present or cables cannot be used

When should tree props be recommended?

Low, long horizontal branches are at high risk and cables are insufficient

What is a lightning protection system intended to do?

Carry electrical charge safely to the ground

A common target-based mitigation strategy is to

Move or restrict access to targets

What two things does risk mitigation do?

Involving reducing either the likelihood and/or of failure or likelihood of impact

Should dead end grips be cut

Never, since the structural integrity of it can be damaged when cut

A common threshold level of live crown ratio for conifers in our region (below which they do not respond well to land development) is...

30%

For an individual, specimen tree, the best way to estimate the size of the CRZ is based on...

Tree dbh

What is a Critical root zone

Also known as the tree protection zone, is the minimum area around a tree that must be protected to keep the tree healthy and structurally stable during construction, excavation, or site work

A  40-cm dbh red alder (Alnus rubra) that is in average condition is likely to be...

 

of low suitability for preservation because it is short lived and has low tolerance for construction

According to Table 6.2, compared to younger trees of the same size, older trees require...

larger tree protection zones (or CRZs)

A tree with a high height:diameter ratio may be likely to be...

Unstable when exposed to wind

You wish to preserve trees in Totem Park, a one-block park dominated by a stand of large evergreens. What is the primary risk of keeping a small group of trees and removing others?

 

that edge trees in this group will not be windfirm and will fail

Prior to approving a plan for land development, it is very typical for municipalities to require...

An estimate of the proportion of the site covered by tree canopy

What grows from callus tissue following root injury?

New roots

What is calus tissue

Response to mechanical stress and injury, form over the affected area to seal the wound and prevent decay, are a thickened mass of cells

What phases of site development should a arborist be in?

All of them

Which tree structure is commonly damaged during construction activities?

Root system

What is the primary purpose of ANSI A300 Part 5? 

To provide guidelines for managing trees during site planning and construction 

Which pruning method can reduce wind resistance when roots are damaged?

Crown reduction pruning

A minimum TPZ radius of 1.5 m (5 ft) is recommended for trees with DBH less than:

25cm

A one-sided root cut at 6× DBH typically does not affect tree stability in healthy, tolerant species.

True

What treatment is most important during post-construction recovery?

Irrigation

Which phase involves staking layout, demolition, and site clearing?

Preconstruction

Which actions help improve drainage post-construction?

Installation of drain pipes, drill holes, radial trenching

What is a defect in a tree?

Any condition that reduces structural strength

What are shear plane cracks?

Fractures in materials, especially trees, that occur when oppossing compression and tension forces slide past each,, occurs above ground

The “1/3 Rule” for hollow stems suggests a tree may have sufficient strength if the cavity is less than ___ of the stem diameter.

2/3rd

Included bark between co-dominant stems decreases the strength of the __________.

Union

Branch union

Where a tree branch joins the trunk

What is the likely outcome for newly exposed conifer stands with low live crown ratios (<20%)?

Probable failure of edge trees

Can girdling by roots cause possible failure before the tree actually die?

Girdling roots have potential to be fatal to a tree but also disrupt adequate formation of structural roots affecting tree stability. So, in a serious wind or excessive loading event, the tree can fail. 

Where do shear planecracks occur?

 

Along the neutral plane between tension and compression forces

Are trees with multiple stems arising close to the ground less likely to fail than those with higher attachments?

Trees with higher attachments are more likely to fail, because of gravity and higher compression and tension wood as the tree is less stable.

Risk

A state of uncertainty where there is potential for something undesirable or even catastrophic to happen.

Failure

It means a piece of the tree broke or fell down.

Defect

It means that there is a tree characteristic that might contribute to failure.

Target

Something that could be damaged/injured by a failure.

According to research, many tolerant species can survive what percentage of root loss?

25-33%

Where are roots most often locate?

In shallow soil, wide-spreading soil configurations, because they cannot grow down.

A Tree Protection Zone (TPZ) radius is calculated by multiplying DBH by a factor based on:

Species and age

Four professional organizations relevant to urban foresters/arborists

ISA = International society of arboriculture

UCFS = The urban and community forestry society

PNCISA= Pacific Northwest Chapter of the ISA

CUFN = The Canadian Urban Forest Network

Certification

A voluntary program administered by a non-governmental organization. It grants the use of credential to individuals for a specific period of time

Qualification

This is awarded for achievement of a narrow body of knowledge body of knowledge with very learning objectives.