Then…
….and Now
Old growth
Second growth
2
Stand age vs. percent of juvenile wood
When trees grow rapidly so that they are of harvestable size when relatively young, the percentage of
juvenile wood increases dramatically (data shown for Loblolly pine).
(Zobel & van Buijtenen)
influences
Forestry
Management
Options
Tree
Growth
determines
Wood
Properties
influences
Cost of management
and silviculture
influences
determines
influences
Technical
Performance
Size
Price
Acceptance
For End Use
influences
influences
Forest Management/Silvicultural options
– effects on Wood Quality
Objective
To maximize the value of a plantation over a short rotation.
Value of logs and lumber depend upon:
Logs
-
Lumber -
large diameters
long lengths
clear faces
premium lengths and widths
absence of knots and other defects
5
Softwood Lumber Pricing ($/MBF)
Product
Length (ft)
8
10
12
14
16
18
20
2x4
215
245
245
240
270
260
270
2x6
215
245
240
235
265
260
270
2x8
220
240
255
240
275
270
290
2 x 10
195
200
290
300
300
315
300
Note: Data is not from 2012
Forest management/silvicultural options and wood quality
Foresters’ options
Improve site
• Cultivate
• Irrigate
• fertilize
Manipulate crop
• Planting stock
• Planting distance
• Juvenile space
• Thin
• Prune
• Rotation age
These actions influence the growth of the crown and roots which in turn influence:
- Stem size and form
- Ring structure (relative ew/lw proportions)
- Branch size and number
- Juvenile wood (amount and proportion)
7
*
Growth rate effect on ring structure
Rapid grown
Slow grown
Ring porous
hardwoods
Diffuse porous
hardwoods
Softwoods
8
*
Effects of initial spacing distance at time of planting
Wide spacing
(400-750 stems/ha)
Narrow spacing
(1500 stems/ha)
• Increased vegetative
competition
• Trunk with large branches
• Maximize piece size
• Encourage lower density of
mature wood
• Lower % of juvenile wood
• Maximize stand volume
• Fewer and smaller branches
• Encourage higher density of
mature wood
• Higher % of juvenile wood
9
*
Effect of tree spacing on juvenile wood production
Narrow spacing
Wide spacing
Mature
wood
Juvenile
wood
10
How to overcome disadvantages
of wide spacing
• Plant genetically selected stock
• Chemical or mechanical brush control
• Plant close together initially, then thin
• Prune
11
Tree improvement programs
• Select high volume producers
• Reject low wood density selections
• Select straight trees
• Select small branches (perpendicular)
• Reject extreme spiral grain
12
Thinning
Before
After
Loblolly pine plantation – 20% stem removal
http://www.forestryforum.com/board/index.php?topic=39179.0%3Ball
13
Thinning
Take-out row for skidder
access
Skidder with grapple full of
thinnings
http://www.forestryforum.com/board/index.php?topic=39179.0%3Ball
14
*
Thinning
Schematic sizes and ring width patterns of Douglas-fir logs (sections at 4.5 feet) grown under different regimes (each
concentric circle represents six annual rings). Note on a good site, the plantation wood (B) produces wood with large rings
at the centre and faster diameter growth than from a natural stand (A). Poor sites will produce narrow rings (C) but still
juvenile wood (formed while the cambium is still within the live crown) in both natural stands and plantations. If plantations
(B) are not thinned when young, many of them will probably slow down abruptly in growth and appear as D, so that
primarily small diameter wood will be available in the future. If they are thinned by removing some of the trees when
young (at B), they can produce logs as in E or F, depending on the intensity of the thinning. Future logs such as E or F will
be produced primarily if the forest products industry can develop a market for logs such as B, so that such stands can be
thinned instead of developing into logs with characteristics such as D. (Oliver)
15
Pruning
• Reduces number of branches (knots)
• Reduces juvenile wood formation
• Reduces taper
• Possibly reduces growth rate
16
Pruning
http://trimblefoundation.org.nz/images/trimble_trees.jpg
http://www.country-works.co.uk/weblog.aspx
Pruning
Pruning
*
Old-growth log quality zones and
products value
1.
2.
3.
4.
5.
Clear
Near Clear
Appearance merch.
Structural lumber
Low grade
Maximum knot sizes allowed on the
edge and the centre-line of 2x4,
2x8 and 2x12 lumber
$1,250-4,000/Mbfm
$ 600-1,000/Mbfm
$ 450-800/Mbfm
$ 350-500/Mbfm
$ 200-350/Mbfm
(Josza)
20
Fertilizing
• Increase growth rate
• Reduce wood density
• Even out earlywood-latewood differences
in wood density
• Relatively short term effect (3-5 years)
21
Effect of fertilization on wood density
Practical consideration for wood quality control
• Economics of clear wood, high wood density,
large log diameter
• Tree improvement programs
• Control of juvenile wood
– Spacing (planting, juvenile spacing, thinning)
– Rotation age
• Develop clear wood by pruning
23