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  • 1. Trees and Construction Chapter 13 ISA Arborists’ Certification Study Guide – Domains: Urban Forestry & Protection and Preservation
    Mark Grueber, Urban Forester
  • 2. Describe how trees can be injured or killed as the direct result of construction damage.
    Discuss the importance of arborists’ participation in the planning stages of development if trees are to be a part of the landscape.
    Explain the steps that can be taken to preserve trees on a construction site.
    Discuss some techniques that can be used to preserve trees when the soil grade must be changed.
    Explain the limitations for treatment of trees that have been damaged by construction.
  • 3. Key Terms
    The Key Terms as listed in the Arborist’s Certification Study Guide will be defined and highlightedthroughout the presentation.
  • 4. “Trees never knew complete removal of trunks, machine compaction of soils, sudden changes in water drainage patterns due to roads, pollution, and disruption of niches for soil organisms…These actions have come suddenly. They are being repeated.” – Alex Shigo, A New Tree Biology
  • 5. Construction Damage to Trees
    One of the most common causes of tree death and decline in urban areas
    People want to “live in the trees” but most landowners, developers and builders don’t understand how to take advantage of the opportunity.
  • 6. The Missing Link: Trees are part of the community’s infrastructure
    Trees are an important and vital part of a community’s infrastructure
    What do trees require?
    What do we provide in an urban/ suburban setting?
    Planning for trees
  • 7. What’s missing?
  • 8. Elements that affect plant growth
    What we can’t impact
    Carbon Dioxide
    Soil texture (sand, silt or clay)
    What we can impact
    Available Water
    Available Nutrients
    Soil structure (how a soil hangs together)
    Available space
  • 9. …and a professional arborist or forester to tell them that.
    Trees CAN be protected and preserved on construction sites
    A professional arborist or forester MUST be involved early – during the planning stage.
  • 10. How are Trees Damaged During Construction?
    The most serious damage to trees caused by construction is underground.
    Root damage and soil disturbance.
  • 11. Roots…a review.
    Which is a more accurate representation of a trees root system?
    Fine absorbing roots are concentrated in the upper few inches of the soil
  • 12. Roots…the real picture
    Mark Grueber, Ecological Consulting Services
    Mark Grueber, Ecological Consulting Services
    Mark Grueber, Ecological Consulting Services
  • 13.
  • 14. Root Damage from Construction
    Root injury may show decline in a few months or several years
    Remember the mortality spiral?
    Common symptoms: yellowing or early fall color, watersprouts, dieback of small twigs and eventually major branches
  • 15. Construction Damage - Physical Injury to Trunk and Crown
    Damage to vascular tissues
    But trees heal…don’t they?
    Mortality spiral…again!
    Note the “tree protection fencing”
  • 16. Construction Damage - Cutting of Roots
    Digging and trenching[digging to install utilities; of concern due to root damage] will likely sever roots
    Usually due to misunderstanding of root growth habit (1-3x branch spread)
    Amount of damage depends on proximity to trunk and area of root development
  • 17. Cutting of Roots - continued
    Severing 1 root can remove 15 to 25% of root system
    Root loss may increase potential for tree failure
  • 18. Construction Damage – Soil Compaction
    [Compression of the soil resulting in a reduction of the total pore space, especially the macropores]
    Ideal soil has 50% pore space – filled with H20 and air
    O2 is reduced; CO2 and other gases increase
    Root growth is diminished; absorption reduced
  • 19. Construction Damage – Added Soil
    90% of fine roots that absorb water and minerals are in the upper few inches of soil…got it???
    Additional soil – even a few inches – can dramatically alter the infiltration of water and oxygen; fine roots die within 30 minutes
    Altering the drainage pattern may also cause significant issues
  • 20. Construction Damage – Exposure
    Trees grow in communities with other trees and/or non-turf type plants
    Types of injury: sunscald, improper taper, aforementioned root and soil issues
    It all comes back to understanding the biology of trees and “forests”
  • 21. Are there alternatives?
    Tree Protection Planning and Preservation
    Planting site improvements
    Rooting space
    Conservation development – preserving a portion of trees (not on exam!)
  • 22. Planning and Preservation
    Tree protection planning cannot wait until construction
    Must involve a professional arborist or forester who can communicate with developers and builders
    Arborist must be involved from beginning to end
  • 23. Considerations of Tree Protection Planning
    Don’t try to save every tree!
    Species, size, location and condition
    Don’t save a hazard
    Younger trees may survive the stress
  • 24. Tree Protection Planning
    Arborist – evaluates, selects and maps trees
    Landscape Architect – assists with plan preparation to consider other parts of infrastructure
    Don’t just consider the trees – remember it’s an ecosystem!
  • 25. Tree Protection Planning
    Consider design changes or construction procedure modifications to accommodate trees
    Tunneling [alternative means to trenching for installation of underground utilities] instead of trenching is one of the most common
  • 26. Specifications
    [detailed plans and statements of particular procedures and standards]
    All tree protection MUST be written into construction specifications
    All contractors (and subs!) must be made aware of these specs
    Consider fines (or incentives) using tree and landscape valuation methodology
  • 27. Construction Damage Avoidance
    Barriers [fences or other means to establish a protection zone around trees on construction sites]
    Place as far away from tree as possible…or a minimum of 1’/1” dbh
    No traffic or storage of building materials, waste or excess soil
  • 28. Avoidance - Limit Access
    Limit access to one route [means of entering and leaving a property during a construction operation] on and off property – but be realistic! Remember parking.
    Specify areas for storage of equipment, soil, building materials; as well as areas for burning, washout, etc.
  • 29. Avoidance – Compaction Reduction
    Build a “mulch road” - six to twelve inches of wood chips.
    Must be CAREFULLY removed or reused
    Plywood sheets
  • 30. Avoidance – Grade Changes
    Terracing[method used to lower the soil grade in stages]
    Maintain original grade as far from tree as possible
    Must be accompanied by root pruning and care where roots are exposed
  • 31. Avoidance – Grade Changes continued
    Tree Island[soil or landscape surrounding a tree, such as within a paved area]
    Similar to terracing
    Excellent for retaining small groves
  • 32. Avoidance – Grade Changes continued
    Aeration systems[the set of holes or trenches created in a tree’s root area to improve oxygen availability to the roots]
    Tree wells[wall constructed around a tree when the soil grade is raised to maintain the original soil level and provide oxygen to the root zone]
    Lack of supporting research
    Gravel or stone below fill does NOT improve water or oxygen flow
    Consider tree size, species, drainage patterns, soil conditions, fill depth, irrigation and future maintenance
  • 33. Avoidance – Good Communication
    The arborist must be involved during all phases of building
    Take good notes and photos
    This is where projects usually go wrong
  • 34. “We only took the fencing down for a moment.”
    A tree protection plan without monitoring by an arborist is a waste of resources
    Very few projects result in good tree protection
    Plan for post-construction tree maintenance
  • 35. Treatment of Construction Damaged Trees
    Periodic inspection and monitoring (post-construction) is a must
    A little turf can hide a hazard
    Safety first..but beware of unscrupulous contractors
  • 36. Construction Damage Treatments - Pruning
    Remove only broken, damaged, or diseased limbs
    During construction limbs may have to be pruned for equipment clearance
    DO NOT thin the canopy to “compensate” for root loss – why?
  • 37. Construction Damage Treatments – Cabling & Bracing
    Some trees can be preserved with remedial treatments
    Cables must be inspect periodically
    Inherent liability for the arborist
  • 38. Construction Damage Treatments – Wound Repair
    Wounding is common on construction sites
    No wound dressings and STOP telling people it will “heal!”
    Bark tracing[cutting away torn or injured bark to leave a smooth edge
  • 39. Construction Damage Treatment – Irrigation and Drainage
    Maintain adequate but not excessive moisture
    Monitor for changes in drainage patterns
    Most irrigation systems are inadequate and cause more harm than benefit
  • 40. Construction Damage Treatments – Mulching
    Inexpensive and very beneficial when applied properly
    Use chipped bark, wood, or pine needles if possible – why?
    Mulch as much of the root width as practical for the landscape
    No volcanoes!
  • 41. Construction Damage Treatments – Aeration (Vertical Mulching)
    [filling vertical drilled holes in the soil with materials such as gravel, perlite, peat or sand]
    Drill holes 2-4” in diameter; 1-3’ on center
    Drill holes to a 12” depth unless fill has been placed over the root system
  • 42. Construction Damage Treatments – Aeration (radial trenching)
    [means of aerating the soil in the root zone of a tree by removing and replacing soil in a spoke-like pattern]
    Air excavator [device that blows air at high force; used to remove soil from the root zone of trees]
    Mechanical trenchers should not operate within 4-8’ of trunk
    Trench at least to dripline; 1’ depth
  • 43. Construction Damage Treatments – Fertilizer? or “Let’s Feed that Sucker!”
    AGH!!! (pet peeve – this is where I go off for a while, sorry)
    Why is this not a good idea?
    If used ISA recommends a slow release to minimize risk of root injury
  • 44. One More Time!
    Monitor, monitor, monitor.
    Use your knowledge of tree biology and the site conditions to guide you
    Obviously, this should be done by a professional…not this guy
  • 45. It’s Quiz Time!
    Name 5 ways that trees can be adversely affected by construction:
    Root injury
    Soil compaction
    Injury to trunk or branches
    Grade change
    Excavation/severing root system
  • 46. When soil is compacted, the ______ _______ between soil particles is reduced.
    pore space
  • 47. Two detrimental effects of soil compaction are:
    Restriction of growth
  • 48. A technique used to reduce soil compaction around trees on a construction site is to spread a temporary, thick layer of _______.
  • 49. The overriding objective of an arborist involved in a development project is to save every tree on the site (true/false).
    False…but aren’t they cute?
  • 50. It is better to tunnel directly under a tree than to cut directly across the root system of a tree when excavating for utility lines (true/false).
  • 51. An important action that should be taken at the start of a construction project is to erect _______ around all of the trees that are to remain.
    Protective fencing or barriers
  • 52. Carefully cutting away loose, damaged bark is called _______ _______.
    bark tracing
  • 53. Soils that have been compacted or raised in grade are good candidates for soil _______.
  • 54. There is far more than an arborist can do to treat trees that have been damaged by construction than to prevent the damage (true/false).
    What a dork!
  • 55. _______ is a technique that may be employed to lower the soil grade in steps.
  • 56. (Easy) Sample Test Questions
    When soils are compacted by construction equipment, trees usually decline because:
    oxygen availability is reduced
    the ability of the roots to absorb water and minerals decreases
    root growth and expansion may be diminished
    all of the above
  • 57. (Easy) Sample Test Questions
    Arborists should be involved early in the construction planning process because:
    tree preservation measures should be in the specifications
    once construction has begun, it may be too late to save the trees
    there is often little arborists can do to treat construction damage
    all of the above
  • 58. (Easy) Sample Test Questions
    A measure that can be taken to minimize compaction on a construction site is:
    water the site thoroughly before equipment is brought in
    permanently raise the soil grade to protect tree rots
    spread a temporary, thick layer of mulch over the site
    root prune the trees in advance
  • 59. (Easy) Sample Test Questions
    If a significant portion of a tree’s root system has been removed during building construction, a step that will help preserve the tree is:
    pruning one-third of the crown to compensate for root loss
    a surface application of 10 pounds of soluble nitrogen per 1,000 square feet
    construction of a tree well
    none of the above
  • 60. (Easy) Sample Test Questions
    Digging trenches in a wheel-spoke pattern and backfilling with organic matter or a more porous soil is called:
    radial aeration
    tunnel aeration
    soil fracturing
    vertical radiation
  • 61. Challenge Question
    What actions can be taken if a tree is damaged by construction in violation of the written specifications?
  • 62. Challenge Question
    Why may tree death and decline due to construction occur several years after construction is complete?
    What are some of the signs and symptoms of construction damage that an arborist can look for following construction?
  • 63. Resources
    Trees and Development: A Technical Guide to Preservation of Trees During Land Development; Matheny and Clark, 1998.
    Root Injury and Tree Health; Watson
    Missouri Department of Conservation Urban Forester: and
    International Society of Arboriculture:
    Building with Trees Workshops – The Arbor Day Foundation: