Chapter 13: Trees and Construction

Question 1

What is one of the most common causes of tree death and decline in urban areas?

Answer 1

construction damage

Question 2

Symptoms of a tree with damaged roots due to construction activity?

Answer 2

small or yellow leaves, premature fall color, extensive watersprout (epicormic shoot) development on the trunk and main limbs, dead twigs, and eventually the death of major branches

Question 3

Examples of construction damage to trees above ground

Answer 3

breaking branches, tearing the bark, and wounding the trunk; permanent injuries even if compartmentalized

Question 4

trenching

Answer 4

linear, open excavation, often used to install utilities or structural footings; can cause tree root damage; will likely sever a portion of the roots of trees

Question 5

Where are roots of mature trees typically found?

Answer 5

one to three times the spread of the branches

Question 6

How much damage can severing one major root cause?

Answer 6

loss of 15 to 25% of the root system; if major support roots are cut on one or more sides of the tree the anchorage will be lost and the tree may fall or blow over

Question 7

soil compaction

Answer 7

compression of the soil, often as a result of vehicle or heavy-equipment traffic, that breaks down soil aggregates and reduces soil volume and total pore space, especially macropore space

Question 8

Types of intentional and unintentional soil compaction

Answer 8

intentional - to create a stable base for buildings or pavement
unintentional - by vehicles and/or heavy machinery used around the site

Question 9

How much pore space is needed for root growth in ideal soils?

Answer 9

50% pore space (spaces between soil particles filled with water and air) decreased space reduces oxygen availability to the roots and causes accumulation of carbon dioxide and other gasses

Question 10

What are some negative impacts of soil compaction?

Answer 10

reduces water infiltration and percolation and impairs drainage; ability of roots to grow and expand is reduced

Question 11

Where are as much as 90% of the fine roots that absorb water and minerals found?

Answer 11

in the upper few inches of soil because roots grow best where their requirements for space, air, and water are met, which is usually near the soil surface

Question 12

What does adding soil over the root system do?

Answer 12

suffocates the roots; causes poor drainage and aeration conditions

Question 13

What negative impacts does removing neighboring trees have?

Answer 13

lack of protection causes other trees to break from wind or ice loading, exposes tree to more sunlight and wind than accustomed to (sunburn on trunks and branches of tree)

Question 14

development

Answer 14

process of preparing the land and building structures to accommodate a variety of uses

Question 15

Phases of land development

Answer 15

planning, design, grading, construction, and maintenance

Question 16

Construction sequence of events

Answer 16

1. ) site clearing and demolition to clear the site of existing structures and vegetation that were not expressly identified to remain
2. ) rough grading to create the projects grade contours
3. ) installation of sitewide utilities and water, storm, and sanitary sewer systems
4. ) grading for establishment of finish pad, surface, and roads
5. ) construction of roads and buildings and installation of utilities
6. ) fine grading and installation of landscapes

Question 17

Professionals that arborists must be able to communicate with

Answer 17

developers, architects, planners, engineers, builders, and landscape architects

Question 18

What trees should be preserved at a construction site?

Answer 18

only healthy, structurally sound trees; not practical or desirable to preserve every tree; work with the builder and developer to determine which trees to preserve and which to remove; consider species, size, maturity, location, and condition; large mature trees are less tolerant of the construction process than young vigorous trees; try to maintain diversity of species and tree maturity

Question 19

construction design plan

Answer 19

details the location of trees and other features in relation to the buildings, roads, and infrastructure; should comply with applicable standards and show protection zones and details of all mitigation and preservation measures

Question 20

tunneling

Answer 20

digging, often with special machinery and shoring other supports, below the surface of the ground without an open trench; alternative for installation of underground utilities that avoids cutting of tree roots or damage to hardscape or existing utilities

Question 21

specifications

Answer 21

detailed plans, requirements, and statements of particular procedures and/or standards used to define and guide work; written to detail exactly what can and cannot be done to and around the trees; has fines and penalties (proportional to the potential damage to protected trees and increase for multiple infractions) for violations built in

Question 22

barriers

Answer 22

TPZ; construction fences around each tree or group of trees to remain

Question 23

possible measures to increase tree vitality prior to construction

Answer 23

water management, mulching, fertilization, pest management, and/or application of tree growth regulators

Question 24

tree protection zone

Answer 24

TPZ; defined area within which certain activities are prohibited or restricted to prevent or minimize potential injury to designated trees, especially during construction or development; area around tree or groups of trees in which no grading, excavation, or construction activity is to occur without written approval and generally under the supervision of the project arborist

Question 25

Where should the TPZ fence be placed?

Answer 25

1 foot diameter for each inch of trunk diameter for young trees or species that are tolerant of construction; distance increases for older trees and species with moderate to poor construction tolerance

Question 26

How big should the TPZ be?

Answer 26

size and shape depend on root and crown dimensions and development constraints; goal is to protect aboveground portions of the trees and their root systems which can extend much farther out than the drip line

Question 27

What should be banned from the TPZ?

Answer 27

no building materials, waste, and excess soil; no digging trenching, compaction, or other soil disturbance allowed; competitive weeds should be removed and mulch should be added to the entire area

Question 28

access route

Answer 28

defined entrance and exit route for a property during construction, tree work, or landscape operations

Question 29

How to limit access in a construction zone?

Answer 29

allow only one access route, instruct contractors where they are permitted to drive and park their vehicles; provide storage areas for equipment, soil, and construction materials; specify area for burning, cement wash out pits, and construction work zones away from protected trees

Question 30

How to reduce compaction?

Answer 30

spreading 6 to 12 inch layer of coarse mulch (such as wood chips) on the soil surface around the trees to help disperse the weight of construction equipment; place large plywood or steel sheets over mulch for additional weight dispersal [mulch should only be 2 to 4 inches deep, so remove it carefully if it has not been reduced on its own]

Question 31

ability of tree to survive a grade change depends on what?

Answer 31

the amount of the root system that will remain after grading, the tree species tolerance to root loss, the degree to which the grade is lowered, the soil conditions, and whether irrigation will be applied

Question 32

hydrology

Answer 32

study of the properties, distribution, and effects of water on the Earth’s surface, underground, and in the atmosphere

Question 33

tree island

Answer 33

enclosed planting bed surrounding a tree, often within a paved area or adjacent to a street; constructed when the grade must be lowered completely around a tree

Question 34

What types of retaining walls are preferred on tree islands?

Answer 34

vertical retaining walls to minimize grading toward the tree

Question 35

tree wells

Answer 35

aeration systems to keep soil fill far from tree trunks and minimize the percentage of the root systems covered

Question 36

preconstruction meeting

Answer 36

held by the arborist to ensure that all subcontractors understand the importance of the TPZ

Question 37

bark tracing

Answer 37

cutting away torn or injured bark to leave a smooth edge; cutting jagged edges away after bark is damaged along the trunk or major limbs

Question 38

wound dressings

Answer 38

use to accelerate wound closure and reduce decay has not been sustained by research; some beneficial effects in reducing borer attack and oak wilt infection or controlling sprout production or mistletoe; primarily used for cosmetic purposes; light coating of nonphytotoxic material

Question 39

benefits of applying mulch

Answer 39

enhance root growth, moderate soil temperatures, maintain moisture, and reduce competition from weeds and grass; benefits only apply when it is applied properly! (2-4 inches and not against the trunk)

Question 40

vertical mulching

Answer 40

an aeration or fertilization technique; drilling vertical holes in the soil and filling them with materials (organic, such as compost) to improve aeration; only effects a small percentage of the root zone

Question 41

radial trenching

Answer 41

technique for aerating the soil around a tree by removing and replacing soil (native soil/compost, that may be amended) in trenches made in a spoke like pattern (radially from the trunk) in the root zone to improve conditions for root growth

Question 42

air excavator

Answer 42

device that directs a jet of highly compressed air to excavate soil; used within the root zone of trees to avoid or minimize damage to the roots, or near underground structures such as pipes and wires to avoid or minimize damage to them

Question 43

Use of fertilizer on construction trees?

Answer 43

recommended to not use fertilizer a year after construction damage because water and mineral uptake may be reduced due to root damage

Question 44

Tasks/role of the arborist during the construction phase?

Answer 44

1. ) enforce the tree protection zone (TPZ) - space is a premium on construction sites, so open areas defined in the TPZ are attractive locations
2. ) assist with changes in the field - participate in decisions when conditions or plans change
3. ) monitor injury to trees and provide corrective action - be prepared to provide management options (pruning or irrigation) where damage has occurred
4. ) communicate with the project superintendent - help the project superintendent understand the need for tree protection while acknowledging the range of demands and challenges placed on them to complete work
5. ) facilitate completion of the project - assist in project completion in a timely manner