1. Arboriculture J.G. Mexal Spring 2001
The Value of Trees
Arboriculture
J.G. Mexal
Spring 2001

3. Roots growing between concrete slabs

4. Arboriculture The Value of Trees/Pirone 2000
Supply Oxygen
Sequester Carbon Dioxide
Reduce Noise Pollution
Trap Particulates
Alter Microclimate
Improve Aesthetics
Enhance Outdoor Urban Spaces
Alter the Character of a Community
Provide products

5. Arboriculture J.G. Mexal Spring 2001
How a Tree Grows
Arboriculture
J.G. Mexal
Spring 2001

6. Arboriculture How a Tree Grows

7. Arboriculture How a Tree Grows-Terms
Trunk or bole
Crown
Terminal bud (scar)
Apical dominance- terminal bud
Apical control - crowns
excurrent- strong apical control
conifers, sweetgum, holly,
decurrent- weak apical control
most deciduous trees

8. Woody Stem Structure

9. Arboriculture How a Tree Grows-Terms
Excurrent
Decurrent

10. Arboriculture How a Tree Grows-Terms
Earlywood
Latewood
Sapwood
Heartwood
Tracheid-(conifers)
Vessel- (hardwoods)
Cambium
Xylem
Phloem
Bark
Periderm
Cork cambium

11. Bark
Cambium
Heartwood
Sapwood
Latewood
Earlywood

12. Forestry & Society Xylem production- earlywood vs latewood
Phloem
1,2 = Developing xylem cells
3,4 = Latewood cells
5 = Earlywood cells
L = Preceeding year

13. Forestry & Society How a Tree Grows/Diffuse vs Ring Porus
Silver Maple
White Oak
50X

14. Forestry & Society How a Tree Grows-Idealized
Annual rings
leaves
fruit
Taproot
Lateral root
Leaves
Fruit

15. Tree Growth
Year 3
Year 2
Year 1
Maximum diameter growth occurs at the base of the live crown.
As the tree grows, the crown tends to rise with increased shading.
Basal pruning raises the crown and raises the point of maximum diameter growth.

16. Tree Growth
Maximum diameter growth occurs at the base of the live crown.
As the tree grows, taper decreases, creating a more cylindrical bole.
Often there may be some flare at the butt of the bole (not illustrated).
Year 3
Year 2
Year 1

17. Arboriculture How a Tree Grows-shoots
Shoot elongation (cm)
Whorl number
Branch type
Physiol. Of Woody Plants p428

18. Forestry & Society Shoot Growth in Eastern White Pine
Terminal growth = 44 cm
Lateral branch = 26 cm
2o lateral = 12 cm
Lateral branch = 19 cm
Lateral branch = 14 cm
2o lateral = 10 cm
3o lateral = 6 cm
2o lateral = 10 cm

19. Arboriculture How a Tree Grows-Terms
Radical
Taproot
Lateral root 1o 2o
Mycorrhiza(s) [e]
ectomycorrhiza
endomycorrhiza
Root hair
Sinker root
Mother root
Actinorhiza
Russian olive
Alder
Nitrogen fixer
Legumes

20. Arboriculture How a Tree Grows-roots (7 wks)
Robinia pseudoacacia
Pinus taeda
(cm2)
(cm2)
(cm)
(cm2)
(cm2)
(cm)
Physiol. Of Woody Plants p 27

21. Arboriculture How a Tree Grows-roots
Percent
Pinus taeda
Δ = Growing tips
Physiol. Of Woody Plants p 28

22. Quercus rubra (red oak) wound
10 = Bark characteristics
9 = ‘Normal’ growth resumes
8 = Excessive growth to recover
7 = Tree harvested in spring
6 = Recovery takes 5 years
5 = “Walling-off” the injury
4 = Buckshot wound
3 = Declining growth
(competition?)
2 = Rapid early growth
1 = Pith

23. Piñon response to transplanting

24. Arboriculture How a Tree Grows
Dormancy-lack of visable growth
Ecodormancy- environmental stress induced
Endodormancy- requires chilling
Paradormancy- regulated by other buds
Cold-hardiness
Ability to survive freezing temperatures
Function of tissue, season, growth stage

25. Dormancy & Cold-hardiness Dormancy Cycle/ Fujigama and Nee 1987
Degree Growth Stage Model
Growth 90
180
270
360
Dormancy
Cold Hardiness (oC) -5
-10

26. Dormancy & Cold-hardiness Dormancy Cycle/ Fuchigama and Nee 1987
Degree Growth Stage Model
Eco-
Eco-
Endodormancy
Growth 90
180
270
360
Dormancy
Cold Hardiness (oC) -5
-10

27. Dormancy & Cold-hardiness Dormancy Cycle/Zones of Manipulation
Degree Growth Stage Model
Growth 90
180
270
360
Dormancy
Cold Hardiness (oC) -5
-10

28. Dormancy & Cold-hardiness Dormancy Cycle : intensity varies
Photoperiod
Photoperiod
36o N latitude
45o N latitude
Relative Dormancy
30o N latitude
20o N latitude

29. Red = free water (ecodormant) Blue = bound water (endodormant)
Dormancy & Cold-hardiness Dormancy Cycle: Role of Water-Grape/ Fennnel & Line 2001
Red = free water (ecodormant)
Blue = bound water (endodormant)
Yellow = intermediate
Black = no water
b = bud g = gap
p = pith ph = phloem
bs = bud scale

30. Dormancy & Cold-hardiness Factors Affecting Acclimation-Tissue
Tolerant
Pinus pinea
Shoots = -40oC
Roots = -10oC
Intolerant
Eucalyptus camaldulensis
Shoots = -10oC
Roots = -3oC

31. Dormancy & Cold-hardiness Factors Affecting Acclimation-Size
Winter
Buds = -25o
Cambium = -50o
Roots = -10o
Seedling = -30o
Spring
Buds = -3o
Cambium = -4o
Roots = -4o
Seedling = -3o
Germinant = -2o

32. Distance from runoff water (m)
Dormancy & Cold-hardiness Winter Injury Increases with Severe Water Stress- Leucaena leucocephala/ Mexal unpubl.
Dieback (% of maximum)
Distance from runoff water (m)

33. Dormancy & Cold-hardiness Cold - Hardiness of Apple Blooms
Growth Units
Chilling Units 20
1.0
0.5 15 10
-0.5 5
-1.0 5 10 15 20 25 30
Temperature (oC)

34. Dormancy & Cold-hardiness Cold - Hardiness of Apple Blooms
LT50 (oC)
Tight Cluster
12mm Green
Full Bloom
Full Pink
Green Tip
Dormant
Photos by:
Silver Tip
Growing Degree Hours (oC)