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Trees & Trees & HurricanesHurricanes
Henry MayerMiami-Dade Extension
June 25, 2009http://miami-dade.ifas.ufl.edu
South Florida is “Hurricane Country”
COULD BE YOUR CAR!!!COULD BE YOUR CAR!!!
With dedication to a management plan, your community can become a model for others
A Healthy and Wind Resistant Urban Forest:
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Perception of tree benefitsPerception of tree benefitsBroward County
Hillsborough County
Pros
Broward County
Hillsborough County
Cons1. Hurricane damage from trees
1. Hurricane damage from trees
2. Tree damage to infrastructure
2. Falling trees & branches on power lines
3. Falling branches & trees on power lines
3. Tree damage to infrastructure
4. Falling branches and trees on property
4. Block signage
1.Provide shade
Improve
2.Aesthetics
3.Provide unique community
Character
4. Increased Property values
1. Improve aesthetics
2. Provide shade
3. Increased property values
4. Provide unique community character
Urban Forests in 2007Urban Forests in 2007--20082008
Urban forests are different & constantly changing
*http://www.nrs.fs.fed.us/data/urban/state/?state=FL
Results for Miami-Dade County
• 36.7 Million trees,–83% in private lands
• 107 different tree species,• 3.7% on street right of ways,• CO2 sequestration: 564,490 t per
year,• CO2 storage: 5,496,000 t,• Avoided CO2: 35,000 t per year
A GREENPRINT FOR OUR FUTURE:MIAMI-DADE COUNTY
STREET TREE MASTER PLAN
MD Public Works RAAM
Recommendation:Establish and manage a healthy urban forest to improve wind resistance by:
� Having a comprehensive
tree management plan
� Having a structural pruning program
for young and mature trees
� Choosing more wind
resistance species
� Selecting the right species
� Designing the right place
� Planting high-quality trees
• Urban forest conditions such as overall tree canopy and composition
Urban Forest Loss Depends on:
• Tree species, age, health, and structure
• Conditions during the hurricane such as precipitation and the time to move through an area
• Site characteristics such as soil conditions (for example soil depth and moisture)
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http://treesandhurricanes.ifas.ufl.edu
Tree species that have been found to tolerate wind better than others
Species: trees that resist decay make better candidates for restoration
Laurel oakRoyal poinciana
FicusOrchid tree
Live oakMahogany
Gumbo-limboTamarind
Trees prone to decayTrees that resist decay
The higher the wind speed of the hurricane, the more likely trees will fail
0
5
10
15
20
25
30
35
40
75 95 115 135 155 175
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R2 polyn=0.7154
y = 0.0032x2 - 0.4948x + 30.57
Trees in groups survive winds better than trees growing
individually
When a tree fails or is removed, plant and maintain a new tree in
its place
0
10
20
30
40
50
60
Jeanne Ivan Charley120 mph 130 mph 145 mph
Bra
nche
s Lo
st (%
)
0000
0000
0000
0 - 8 in.
9 - 20 in.
21 - 39 in.
40 - 79 in. The larger and older a tree is,
the more branches it will lose.
Older trees are more likely to fail in hurricanes
Unhealthy trees are predisposed to hurricane damage
Common Causes of Tree Failure
�����
Well-pruned trees survive better than unpruned trees
Live Oak Black Olive Gumbo Limbo0
20
40
60
80
100
1 �����
����
Tree
s S
tand
ing
Aft
er H
urri
cane
(%)
Why do we Prune?Why do we Prune?
Weak vs. Strong
Good structureGood structure
Case Study: Weston Lakes Maintenance Association, Weston, FL
Structural Pruning of 100 Common Area and 700 Swale Mahogany Trees
Case Study: Weston Lakes Maintenance Association, Weston, FL
Structural Remediation Complete
64%survival
0 to 3 m2
(0 to 39 ft2)
Street trees,Parking lots, Yards
73%survival
91%survival
Yards,Parks
4 to 7 m2
(40 to 75 ft2)> 7 m2
(> 75 ft2#
Campuses, Parks, Yards
Trees with more rooting space survive winds better
Common Causes of Tree Failure
Lack of mature rooting space/site constraints
� Give small trees
at least 10’ by 10’
� Give medium
treesat least 20’ by 20’
� Give large trees at least 30’ by 30’
Recommendation:
Give trees enough rooting space according to their mature size
Courtesy: James Urban
Six things can happen to a tree in a hurricane:
1.Uproots
3.Main Stem Breaks2.Branches Break
6.Leaf Loss
5.NoVisibleEffects
4.Leans4.Leans
Response PlanImmediately following stormStep 1: Remove hazards
Step 2: Stake fallen trees where possible
Step 3: Clean canopies of damaged trees
Before the next visit• Allow trees to regenerate energy reserves
• Develop a tree management program in the community
RECOMMENDATION: If a large tree uproots and falls over, it is basically dead and should be removed.
UprootUproot
A small tree (under 4 inches in diameter) may be righted. Its future care needs to include staking and
watering as though it was freshly planted.
UprootUproot
How to Stand a Tree Up• Water as if the tree were
recently planted. Irrigate 3x a week with 3 gallons/inch trunk diameter. There is no
need to fertilize at this time.•Stake the tree. Adjust stakes and remove when tree is stable.
The main stem breaksThe main stem breaks
� is essentially dead as an urban tree� should be removed
Lose large or small broken branches
� Large broken branches may be able to be repaired through pruning. � Small branches can be pruned.� If a tree has lost more than ½ its crown, it may never regain its structure and health
Canopy Cleaning
Make clean cuts on stubs, breaks, and tears.
Reduce back to lateral branch if one is present.
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Bad cut-called a flush
cut
Wound wood does not develop evenly.
Lions-tailing Lions-tailing:trees with foliage concentrated at the tips of branches because inner branches were removed.• More susceptible to hurricane damage• Difficult to restore
Lions-tailed trees failed
Pruning program
Time needed
to restore:
• 4 + yrs.• four or more visits
• 3 – 4 yrs.• about threevisits
• 2 – 3 yrs. • about two visits
Mature (over 10” dbh)
Medium-aged (5-10”
dbh)
Young (under 5” dbh)
* dbh – diameter at breast height
Sproutsemerging
Reduce some- Shorten 1/3 of the sprouts. They will continue to store energy, but will eventually be removed.
Remove some- Remove 1/3 of the sprouts to allow space for the most vigorous ones to grow.
Leave some- These will develop into the new branches.
Remove or Remediate?Remove or Remediate?
Remove broken fronds that are smothering the bud
UNPRUNED ACCEPTABLE OVER PRUNED
Pines may show no immediate visible damage after a hurricane but may decline over time
No visible effects
Contract specification requirements: All trees FL grade No. 1 or better; UF-IFAS planting detail; post-plant inspection;
Planting
Root flare needs room to expand
Planting issues Planting issues –– 5 5 ”” too deeptoo deep
Pre-plant root ball inspection, excavation and preparation
Kept covered and moist, the cut ends do regenerate an amazing number of roots.
Trees with damaged root systems are more vulnerable to the wind
Common Causes of Tree Failure
Poor maintenance practices
Removed it!!
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