how a tree grows j.g. mexal h/r 302 spring 2005. forestry & society how a tree grows- trees are...
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How a Tree Grows
J.G. Mexal
H/R 302
Spring 2005
Forestry & Society
How a Tree Grows-
• Trees are the 2nd largest organism- Eucalyptus
Sequoia
• Trees are the oldest organism-bristlecone pine (5,000 yrs)
Norway spruce (9,550 yrs)
• They can grow: as much as 25 ft/yras little as 25 mm/yr (1”)
• They can survive: 10 ft of precipitation10 in of precipitation
• They can survive: >100oF temperatures<-50oF temperatures
Trees live a long time!
• Alder• White birch• Sugar maple• Oak• Douglas-fir• Bristlecone pine• Norway spruce
• 25 yrs• 50 yrs• 300 yrs• >500 yrs• >700 yrs• >2,000 yrs• >9,000 yrs
Forestry & Society
How a Tree Grows-
• What does your tree look like?– A 100 ft tree weighs about 4,000 lbs– Has > 200,000 leaves (~120 lbs)
• Will shed 3,600 lbs of leaves in a lifetime
– Produce >5,000 seeds/yr– Have 1,300 lbs of roots– Require
• 8,000 lbs of CO2
• 2,900 lbs of H2O for Ps, and 5,000,000 lbs for Ts
– Generate over 8,000 lbs O2
Source: Ed Gilman, IFAS
Trees in the forest grow with one trunk, and codominant stems toward the top of the tree
Source: Ed Gilman, IFAS
Forestry & Society
Comparison between forest tree and landscape tree
Source: Ed Gilman, IFAS
Factors affecting tree growthGenetic
InformationEnvironmental
Conditions
Physiological Processes
Tree Growth
Bark Cambium
Heartwood
Sapwood
Latewood
Earlywood
Forestry & Society
How a Tree Grows-Functions
• Seed- reproduction• Leaves- photosynthesis (carbon
capture)• Roots- water & nutrient uptake• Bark- protection• Cambium/buds-growth• Xylem- water transport (up) [dead]• Phloem- carbohydrate transport
(down)
How a Tree Grows
Our secondary growth model:
A typical hardwood tree in cross section (transverse surface).
What can you identify?
Source: Ed Gilman, IFAS
The Bark:
The bark is everything outside the vascular cambium.
As you can see, there is a lot going on in the bark.
Source: Ed Gilman, IFAS
The Bark: periderm:
Periderms form the outer bark.
They are subdivided further.
Source: Ed Gilman, IFAS
The Bark: periderm: phellogen (cork cambium):
The phellogen is the region of cell division that forms the periderm tissues.
Phellogen development influences bark appearance.
Source: Ed Gilman, IFAS
The Bark: periderm: phellem (cork):
Phellem replaces the epidermis as the tree increases in girth.
Photosynthesis can take place in some trees both through the phellem and in fissures.
Source: Ed Gilman, IFAS
The Bark: periderm: phelloderm:
Phelloderm is active parenchyma tissue.
Parenchyma cells can be used for storage, photosynthesis, defense, and even cell division!
Source: Ed Gilman, IFAS
The Bark: phloem:
Phloem tissue makes up the inner bark.
However, it is vascular tissue formed from the vascular cambium.
Source: Ed Gilman, IFAS
The Bark: phloem: sieve tube elements:
Sieve tube elements actively transport photosynthates down the stem.
Conifers have sieve cells instead.
Source: Ed Gilman, IFAS
The Bark: phloem: companion cells:
Companion cells provide sieve tube elements with needed metabolites.
Conifers have albuminous cells instead.
Source: Ed Gilman, IFAS
The cambium:
The cambium is the primary meristem producing radial growth.
It forms the phloem & xylem.
Source: Ed Gilman, IFAS
The Xylem (wood):
The xylem includes everything inside the vascular cambium.
Source: Ed Gilman, IFAS
The Xylem: a growth increment (ring):
The rings seen in many trees represent one growth increment.
Growth rings provide the texture seen in wood.
Source: Ed Gilman, IFAS
The Xylem: vessel elements:
Hardwood species have vessel elements in addition to trachieds.
Notice their location in the growth rings of this tree
Source: Ed Gilman, IFAS
The Xylem: fibers:
Fibers are cells with heavily lignified walls making them stiff.
Many fibers in sapwood are alive at maturity and can be used for storage.
Source: Ed Gilman, IFAS
The Xylem: axial parenchyma:
Axial parenchyma is living tissue!
Remember that parenchyma cells can be used for storage and cell division.
Source: Ed Gilman, IFAS
The Xylem: rays (multiserrate & uniserrate):
Rays are radial parenchyma cells.
Parenchyma cells give rise to adventitious tissues.
Source: Ed Gilman, IFAS
Forestry & Society
How a Tree Grows/Diffuse vs Ring Porous
Silver Maple White Oak
50X
Diffuse Porous
Ring Porous
Forestry & Society
How a Tree Grows-Idealized
Annual rings
leaves
fruit
Taproot
Lateral root
Leaves
Fruit
A tree can produce 200,000 leaves/yr
Woody Stem Structure
Shoot Growth
3o lateral = 6 cm2 o lateral = 10 cm
Lateral branch = 14 cm
2o lateral = 10 cm
2 o lateral = 12 cm
Forestry & Society Shoot Growth in Eastern White Pine
Terminal growth = 44 cm
Lateral branch = 26 cm
Lateral branch = 19 cm
Biomass Partitioning/ Nelda Methany 2005
Time (yrs)3 557 20
Percent100
Leaves/Roots
Wood
Fine Roots
30%
35%
35%
5%5%
90%
Forestry & Society
How a Tree Grows
• Growing regions or meristems– Buds- height, flowers, leaves, (roots)– Cambium- diameter– Cork cambium - bark
• Factors– Temperature– Light– Water
Tropics vsBoreal
Where a tree grows!!
Tropical forest
Desert Dry tropical forest
32
59
oF86
20” 80” 140”
Forestry & Society
Urban Forestry CO2 capture
Basic Photosynthetic Reaction
• CO2 + H2O CH2O + O2
• 1.47 lb 0.60 lb 1.00 lb 1.07 lb
λ
Forestry & Society
How a Tree Grows/Kozlowski & Pallardy 1999
clear day overcast day
Forestry & Society
How a Tree Grows
• Most forests are regenerated sexually – seeds are required– exceptions: aspen, oak, eucalyptus
• Environmental factors:– light (forest gap)– moisture (mineral soil)– temperature (dormancy & germination)
Forestry & Society
How a Tree Grows - Piñon
• Flower primordia (buds) form in fall (yr-1)
• Flowers develop in spring (yr-2)
• Pollination occurs
• Overwinter
• Fertilization occurs in spring (yr-3)
• Growth of cone
• Maturation of cone with seeds in fall
• Total time elapsed >24 mo.
Drought
Pine life cycle
Forestry & Society
How a Tree Grows/Reproductive Cycle of Pinus contorta (Owens & Molder 1984)
Forestry & Society
How a Tree Grows-female cones
Pinus elliotii (slash pine)
1 mo.12 mo.24 mo.
pollination
maturation
fertilization
Rachis
Viable seed
Empty seed
Bract
Forestry and Society
Pinus eldarica cone
Forestry and Society Pine seed size variation
Pinus pinea (Italian stone pine) Pinus nigra (Japanese black pine)
wing
Forestry & Society
How a Tree Grows-Germination
• Seed is dispersed• Overwinters (dormant)• Germinates• Growth commences
• 10,000,000/ac• 4,000,000/ac• 4,000/ac @ 25 yrs• 100/ac @ 100 yrs
Nothofagus in Chile
0.001%
Ponderosa pine seed rain following harvest-CO / WJAF 21(1):19:06
0
10
20
30
40
50
60
70
80
90
100
Shelterwood
Seedtree
Year
Seeds/m2
Logged ’80-’81 winter
0
2
4
6
8
10
12
14
16
18
20
Germination
Survival
Seedlings/m2
~48% of seed consumed by animals regardless of year
Dendrochronology
Forestry & Society
Xylem production- earlywood vs latewood
Phloem
5 = Earlywood cells
3,4 = Latewood cells
L = Preceeding year
1,2 = Developing xylem cells
Forestry & Society
Silviculture/Response to Thinning
Juniper/NM
10 mm
False rings
Wider rings
Competition
Forestry & Society
Dendrochronology/Skaptar Jokull Volcano eruption in Iceland causes ‘the summer that wasn’t’ in western Alaska. (http://abcnews.go.com/sections/science/DyeHard/dyehard.html)
Earlywood
LatewoodEruption occurs June 8, 1783
No Latewood, indicating very early onset of winter
Review Questions
• Define: xylem, conifer, phloem, hardwood, cambium, softwood, cord, evergreen, board foot, deciduous, basal area, MAI, CAI, PAI, closed forest, earlywood (spring wood), latewood (summer wood), dendrochronology, false ring
• What environmental factors affect seed production germination? Why does piñon have good seed crops every 4-5 years?
• Describe the basic process of photosynthesis.• Why do trees produce so many seed, yet so few
germinate?