A. Tree Physiology
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1. Tree Physiology
LHAP 305 – Urban Forestry and Arboriculture
2. What is Urban Forestry?
The collection of all trees, woody plants, and vegetation in an urban center.
It includes planning, planting, maintaining, removal, and protection.
Urban foresters – Serve communities by maintaining and improving the environment using trees and other woody plants.
Managing the costs and risks of having trees in the urban environment.
3. What is Arboriculture?
The practice and study of care, of trees and other woody plants
- ISA
International Society of Arboriculture Has different chapters all over the world
Alberta, Saskatchewan, and Manitoba is part of the Prairie Chapter
They promote the world of Arboriculture They control the process of becoming a certified arborist
4. Tree Defects
The Three D’s –Dead, Damaged, Diseased Cracks Cankers
Co-Dominate Stems Included Bark Girdling Roots Ramshorning
- Trimmer Damage
- Poor pruning practices
Total Landscape Care. (2024, April 24). Caring for hazardous trees: Identifying problems and reducing risks. Total Landscape Care. Retrieved Oct 18, 2025
5. Dead, Damaged, Diseased
- Dead
- Damaged
- Diseased
- Included in Pruning Plan
Tree people. (2018, June 27). The 4 D’s: Dead, Diseased, Damaged, or Deranged! Tree People. Retrieved Oct 18, 2025
6. Cracks
- Horizontal cracks
- Vertical Cracks
Degiovanni, J. (2013, April 30). Any way to save a large tree that's starting to split/crack down the middle? Gardening and Landscaping. Retrieved Oct 18, 2025
Beswick Tree Service. (n.d.). My TreeHas a Crack in It - What Should I Do? Beswick Tree Service. Retrieved Oct 18, 2025
7. Cankers
- Dead wood and Bark
- Sunken discoloured appearance Oozing sap
Trees by Jake. (n.d.). Tree Cankers. Trees by Jake. Retrieved Oct 18, 2025
8. Co-Dominate Stems
2 stems of close to equal diameter both trying to be the dominant stem
- The union will have included bark
Moore Cuts Florida. (2024, July 24). Understanding Co-Dominant Stems in Trees & Their Associated Risks. Moore Cuts Florida. Retrieved Oct 18, 2025
9. Girdling Roots
Roots rap around the tree trunk and inhibit its growth and causes a weak point at ground level
Iowa State University. (2024, July). How to Manage Trees Near Sidewalks. Iowa State University. Retrieved Oct 18, 2025
10. Rams Horning
When a tree is sealing off a wound it can grow in a “in-curling form”
Keslick, J. (n.d.). Oak. Keslick and Son Modern Arboriculture. Retrieved Oct 18, 2025
11. Trimmer Damage
Damage to the base of the trunk from string trimmers getting too close and cutting into the wood
Robson, D. (2016, June 06). Mower and Weed Eater Damage. Home, Yard, and Garden Pest. Retrieved Oct 18, 2025
12. Poor Pruning Practices
- Untrained people doing their own pruning
Humans tend to like to break branches and leave those open wounds
American Climbers. (2024, Dec 09). 9 Common Pruning Mistakes that Could Kill your Metrowest Trees. American Climbers. Retrieved Oct 18, 2025
American Climbers. (2024, Dec 09). 9 Common Pruning Mistakes that Could Kill your Metrowest Trees. American Climbers. Retrieved Oct 18, 2025
13. Tree Roots – They follow the water
Lateral Roots – Grow outwards.
Tap Roots – Grow down.
- Root hairs
- Root Flare
- Mycorrhizae – symbiotic relationship with roots
Huang, S. (n.d.). 3 Types of Tree Root Systems. A-Plus Tree Care and Sustainability. Retrieved Oct 18, 2025
14. Root Development site constraints
- Compaction
- Underground Barriers
- Soil type
- Poor Planting Practices
Iowa State University. (2024, July). How to Manage Trees Near Sidewalks. Iowa State University. Retrieved Oct 18, 2025
15. Tree Hormone Cycles
Seasonal Changes – due to Light and temperature changes https://www.pathwayz.org/Tree/Plain/PLANT+HORMONES
16. Tree Hormone Cycles
Gibberellins- Germination and Growth Auxins - Growth Regulator
- Cytokinin's- Promote Cell Division
Ethylene- Causes fruit ripening and leaf drop (Senescence)
Abscisic Acid – Inhibits Germination and Growth
Pathwayz. (n.d.). Plant Hormones. Pathwayz. Retrieved Oct 18, 2025
17. CODIT – Trees Defence System
Compartmentalization of Decay in Trees Trees do not HEAL, they SEAL
It uses 4 walls to contain the decay
Tylosis- When parenchyma cells “balloon” and block flow of sap. First line of defense against decay.
Eastside Tree Works. (2013, Feb 09). Recognizing Hazard Trees #1 CODIT. Eastside Tree Works. Retrieved Oct 18, 2025
18. CODIT
Wall 1 Weakest of the 4 walls
Works to contain the decay from spreading up and down the trunk into the roots or shoots
Blocks off the Xylem above and below the wound Wall 2
- Second Weakest
Works to contain the decay from spreading inwards towards the center
- Closes off the latewood cells
19. CODIT
- Wall 3
Prevents the decay from spreading around the tree (Laterally on horizontal plane)
Blocks the decay using Ray cell in the trunk.
- Wall 4 The Strongest wall
Blocks Decay from spreading outwards into the new wood that is formed after the injury
20. Which wall(s) failed and held in these examples
Auro. (2012, Feb 15). File:CODIT example 1 - Auró.JPG. Wikimedia Commons. Retrieved Oct 18, 2025
PennState. (2024, Nov 10). Understanding the Spread of Decay in Trees. PennState Extension. Retrieved Oct 18, 2025
PennState. (2024, Nov 10). Understanding the Spread of Decay in Trees. PennState Extension. Retrieved Oct 18, 2025
21. Ring Porous and Diffuse porous
- Ring Porous
- distinct earlywood and latewood vessels -high conductivity in early wood
- Quercus, Fraxinus, ulmus, Hippophae
- Diffuse porous
Vessels more evenly distributed Moderate conductivity year-round
Acer, Betula, Tilia, populus, salix, cornus, aesculus
22. Tree Morphology – Tree Structure
Includes looking at the Trunk, Branches, Leaves, and roots.
Is anything wrong with any of them?
Meriam Webster. (n.d.). Structure of a Tree. Meriam Webster. Retrieved Oct 18, 2025
23. Trunk
- Damage to the trunk
- Bends in the wood
- Leaning
- Boring Holes
- Peeling Bark
- Oozing liquids
- Co-Dominance
24. Branches
- Dead, Damaged, Diseased Rubbing Branches Co-Dominant
25. Leaves
- Discolouration
Insect damage – Leaf Miner Early Leaf drop
26. Roots
- Decaying
- Damaged
- Girdling
27. Bibliography
American Climbers. (2024, Dec 09). 9 Common Pruning Mistakes that Could Kill your Metrowest Trees. American Climbers. Retrieved Oct 18, 2025, from https://americanclimbers.com/pruning-mistakes/
Auro. (2012, Feb 15). File:CODIT example 1 - Auró.JPG. Wikimedia Commons. Retrieved Oct 18, 2025, from https://commons.wikimedia.org/wiki/File:CODIT_example_1_-_Aur%C3%B3.JPG
Beswick Tree Service. (n.d.). My Tree Has a Crack in It - What Should I Do? Beswick Tree Service. Retrieved Oct 18, 2025, from https://beswicktreeservice.com/article/my-tree-has-a-crack-in-it-what-should-i-do
Degiovanni, J. (2013, April 30). Any way to save a large tree that's starting to split/crack down the middle? Gardening and Landscaping. Retrieved Oct 18, 2025, from https://gardening.stackexchange.com/questions/24421/any-way-to-save-a-large-tree-thats-starting-to-split-crack-down-the-middle
Eastside Tree Works. (2013, Feb 09). Recognizing Hazard Trees #1 CODIT. Eastside Tree Works. Retrieved Oct 18, 2025, from https://www.eastsidetreeworks.com/blog/recognizing-hazard-trees-1-c-o-d-i-t/
Huang, S. (n.d.). 3 Types of Tree Root Systems. A-Plus Tree Care and Sustainability. Retrieved Oct 18, 2025, from https://aplustree.com/3-types-of-tree-root-systems/
Iowa State University. (2024, July). How to Manage Trees Near Sidewalks. Iowa State University. Retrieved Oct 18, 2025, from https://yardandgarden.extension.iastate.edu/how-to/how-manage-trees-near-sidewalks
Keslick, J. (n.d.). Oak. Keslick and Son Modern Arboriculture. Retrieved Oct 18, 2025, from http://treedictionary.com/DICT2003/HTMLFILES/disscoloredwood-4.htm
Meriam Webster. (n.d.). Structure of a Tree. Meriam Webster. Retrieved Oct 18, 2025, from https://www.visualdictionaryonline.com/plants-gardening/plants/tree/structure-tree.php
Moore Cuts Florida. (2024, July 24). Understanding Co-Dominant Stems in Trees & Their Associated Risks. Moore Cuts Florida. Retrieved Oct 18, 2025, from https://moorecutsflorida.com/tree-tidbits/f/understanding-co-dominant-stems-in-trees-their-associated-risks
Pathwayz. (n.d.). Plant Hormones. Pathwayz. Retrieved Oct 18, 2025, from https://www.pathwayz.org/Tree/Plain/PLANT+HORMONES
PennState. (2024, Nov 10). Understanding the Spread of Decay in Trees. PennState Extension. Retrieved Oct 18, 2025, from https://extension.psu.edu/understanding-the-spread-of-decay-in-trees#:~:text=In%20the%201970s%2C%20USDA%20Forest,such%20as%20foresters%20and%20arborists.
Robson, D. (2016, June 06). Mower and Weed Eater Damage. Home, Yard, and Garden Pest. Retrieved Oct 18, 2025, from https://hyg.ipm.illinois.edu/article.php?id=808
Total Landscape Care. (2024, April 24). Caring for hazardous trees: Identifying problems and reducing risks. Total Landscape Care. Retrieved Oct 18, 2025, from https://www.totallandscapecare.com/business/article/15042541/identifying-and-caring-for-hazardous-trees
Tree people. (2018, June 27). The 4 D’s: Dead, Diseased, Damaged, or Deranged! Tree People. Retrieved Oct 18, 2025, from https://treepeople.org/2018/06/27/dead-diseased-damaged-deranged/
Trees by Jake. (n.d.). Tree Cankers. Trees by Jake. Retrieved Oct 18, 2025, from https://treesbyjake.com/tree-cankers/
Referenced Links
- https://www.pathwayz.org/Tree/Plain/PLANT+HORMONES
- https://americanclimbers.com/pruning-mistakes/
- https://commons.wikimedia.org/wiki/File:CODIT_example_1_-_Aur%C3%B3.JPG
- https://beswicktreeservice.com/article/my-tree-has-a-crack-in-it-what-should-i-do
- https://gardening.stackexchange.com/questions/24421/any-way-to-save-a-large-tree-thats-starting-to-split-crack-down-the-middle
- https://www.eastsidetreeworks.com/blog/recognizing-hazard-trees-1-c-o-d-i-t/
- https://aplustree.com/3-types-of-tree-root-systems/
- https://yardandgarden.extension.iastate.edu/how-to/how-manage-trees-near-sidewalks
- http://treedictionary.com/DICT2003/HTMLFILES/disscoloredwood-4.htm
- https://www.visualdictionaryonline.com/plants-gardening/plants/tree/structure-tree.php
- https://moorecutsflorida.com/tree-tidbits/f/understanding-co-dominant-stems-in-trees-their-associated-risks
- https://extension.psu.edu/understanding-the-spread-of-decay-in-trees#:~:text=In%20the%201970s%2C%20USDA%20Forest,such%20as%20foresters%20and%20arborists
- https://hyg.ipm.illinois.edu/article.php?id=808
- https://www.totallandscapecare.com/business/article/15042541/identifying-and-caring-for-hazardous-trees
- https://treepeople.org/2018/06/27/dead-diseased-damaged-deranged/
- https://treesbyjake.com/tree-cankers/