Density and Stocking
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Transcript of Density and Stocking
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Density and Stocking
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Density and Stocking
• Potential of the land to produce wood is determined mainly by its site quality.
• The actual production or growth of wood fiber achieved on a given site is determined by the number, distribution and species of trees on the site.
• Two measures of the number and distribution of trees on a given site are "density" and "stocking".
• Density is a measurable "fact".• Stocking is a "relative" assessment.
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Measures of Stand Density
1. Number of trees per acre2. Basal area per acre3. Stand Density Index4. Crown Competition Factor
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BA/ac = /
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Stand Density Index
• Based on the observed maximum size-density relationship, using1) number of trees per acre (TPA) and 2) mean quadratic tree diameter (Dq), a.k.a.
• diameter for tree of mean basal area• Incorporates both number and basal area
per acre measurements
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Stand Density Index
0
100
200
300
400
500
600
700
800
900
0 10 20 30 40 50 60
Dq
TPA
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Stand Density Index
10
100
1000
1 10 100
Dq
TPA
Slope ~ -3/2
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Stand Density Index
• Equates observed Dq and TPA to an equivalent TPA for the indexed Dq=10 in.
10
100
1000
1 10 100Dq
TPA
70060050040030020010050
1.605q
10DNSDI
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Crown Competition Factor• Reflects the area available to the
average tree relative to the maximum area it uses if it were open-grown
i21i dbhcw
10043560
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cwMCA
2i
i
a
MCACCF
i i
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Crown Competition FactorCCF < 100
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Crown Competition FactorCCF > 150
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Stocking
• Involves the comparison of a given stand to a "normal", or fully-stocked stand.– Problem: "Has anyone ever seen a normal stand?"
• Assumes that "natural" mortality is solely a result of over-stocking.
• Concept of stocking is very subjective in nature.• Stocking guides are the main method for assessing
stocking.
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Stocking
1) Stocking Guides2) Stand Density Management Diagrams
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1. Stocking Guides
1. Species Specific2. Require that you know trees per acre and basal area per acre.3. Usually have 2 or 3 lines that are important: the A-line, the
B-line, and sometimes the C-line.• Above the A-line: overstocked• Between A-line & B-line: fully stocked• Below the B-line: understocked• C-line: lower limit of “understocking” to reach the B-line
in 10 years on an average stand
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Generic Stocking Guide
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Generic Stocking Guide
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White Pine Stocking Guide
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2. Stand Density Management Diagrams
What are they?• Graphic tools which illustrate how DIAMETER,
HEIGHT, DENSITY and VOLUME change over time for pure, even-aged stands
Why use them?• Lead to understanding of stand dynamics• To plan/evaluate initial spacing and thinning regimes
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2. Stand Density Management Diagrams
Basic Concepts Involve:• Stand Dynamics• Self-thinning Theory• Langsaeter’s Curve
0.15 0.40 0.55 1.00
Relative Density
Mea
n A
nnua
l Inc
rem
ent
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Spacing effects on tree size
0 10 20 30 40 50 60
Time (years)
Ave
rage
size
of t
rees
10x108x87x76x65x54x43x32x2
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Relationship between density and tree size
100 1000 10000Ln(Trees per acre)
Ln(A
vera
ge v
olum
e pe
r tre
e)
10x108x87x76x65x54x43x32x2
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Density (log scale)
Plant
size
(mea
n tre
e volu
me, l
og sc
ale)
Baseline measurement
1st re-measurement
2nd re-measurement
9th re-measurement
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Density (log scale)
Plant
size
(mea
n tre
e volu
me, l
og sc
ale)
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Density (log scale)
Plant
size
(mea
n tre
e volu
me, l
og sc
ale)
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Density (log scale)
Plant
size
(mea
n tre
e volu
me, l
og sc
ale)
Maximum size-density lineMortality initiation line
Stands under-stocked
Zone of OptimumDensity Management
Zone of ImminentCompetition Mortality
Crown closure lineStand trajectories
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