western mensurationists meeting, kelowna, bc – june 24-26, 2007 1 looking for the plateau in...

Western Mensurationists Meeting, Kelowna, BC – June 24-26, 2007Western Mensurationists Meeting, Kelowna, BC – June 24-26, 2007

1

Looking for the Plateau in Douglas-fir Annual Volume Increment

David M. Hyink, Ph.D. (retired)

Timberlands & Raw Materials R & D

Weyerhaeuser Company


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Outline/Topics

Context and Rationale for Growth and Yield Research Biological First Principles

• “Laws” of Self-Thinning

• Langsaeter’s Hypothesis Weyerhaeuser’s Langsaeter Study

• Design

• Results & Conclusions Questions/Comments


3

Forest Growth & Yield and Wood QualityWhat do we want to know?

How stand management options…• Species, genotype, site preparation, planting spacing, non-crop competition &

animal control, thinning, fertilization, pruning

Produce key properties of crop trees…• Dbh, height, crown ratio, stem form, branches & knots, specific gravity, micro-

fibril angle, earlywood/latewood

That create value for specific end-uses.• Logs, lumber, fiber, engineered components

“Engineering-on-the-Stump”


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Forest Growth & Yield and Wood QualityScientific Approach – Data and models

Based upon “First Principles”• Dominant Height / Age / Site Index• Landform / Habitat Type• “Laws” of Self-Thinning (Reineke, Drew and

Flewelling)• Growth vs. Growing Stock Relationships

(Langsaeter)

Continuously updated as new data and experimental results become available.


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Biological First Principles / Langsaeter’s Hypothesis

The total production of cubic volume by a stand of a given age and composition on a given site is, … constant and optimum for a wide range of density of stocking. It can be decreased, but not increased, by altering the amount of growing stock to levels outside this range.


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Biological First Principles / “Laws” of Self-Thinning

Reineke Stand Density Index Relative Density Index Reineke (1933) Drew and Flewelling (1979)

0.15

0.55

0.55

0.15


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The Langsaeter Study

Superimposed on an existing DF research plantation (SI=143) Initial planting spacing: 5’x5’ (1742) and 8’x8’ (680) 4 reps of 4 treatments at each initial spacing (32 plots):

• Non-thinned

• Maintain Relative Density (D&F) 0.25 – 0.35

• Maintain Relative Density (D&F) 0.40 – 0.50

• Achieve RD (D&F) 0.50, then maintain at 0.25 - 0.35 Maintain 4 reps of initial 8’x8’ spacing 0.10 – 0.20 (4 plots) Measurement ages: 13, 15, 16, 17, 19, 22, 25, 28 ,31, 34, 37


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Self-Thinning / Reineke’s Stand Density Index

3.5 5.2 7.8 11.6 17.3

Quadratic mean dbh (in.)

2440

1480

900

550

330

200

8’x8’

5’x5’

500400

Source: Husch, Beers & Kershaw, Forest Mensuration - 4th Edition


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Self-Thinning / Relative Density Index (D&F)

221 384 665 1153 1998

Trees Per acre

Mean Tree Volume (ft3)116

39

28

13

1.4

0.5

0.15

0.55

Maximum Size-Density

0.15

0.55

0.55

0.15


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Growth vs. Growing Stock / Langsaeter’s Hypothesis

0 20 40 60 80 100 0 20 40 60 80 100

V

olum

e In

crem

ent (

Cun

its/a

c/ye

ar)

V

olum

e In

crem

ent (

Cun

its/a

c/ye

ar)

1

Vol

ume

Incr

emen

t (C

units

/ac/

year

)

2

3

4

5

1

2

3

4

5

Volume (Cunits/acre)

1

2

3

4

5

Volume (Cunits/acre) Volume (Cunits/acre)

Age 17

Age 23

Age 35

Source: USFS Research Paper PNW-RP-537


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Growth vs. Growing Stock / Langsaeter’s Hypothesis

Vol

ume

Incr

emen

t (C

u.ft.

/ac/

year

)

Volume (Cubic feet /acre)

Volume (Cubic feet /acre) Volume (Cubic feet /acre)

Age 17

Age 23

Age 35

Source: USFS Research Paper PNW-RP-537


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Langsaeter: Growth / Growing Stock – Age 23

Volume (Cubic feet per acre)

An

nu

al

Vo

lum

e I

nc

rem

en

t (C

ub

ic f

ee

t /

ac

re /

ye

ar)


13

Langsaeter: Growth / Growing Stock – Age 35

Volume (Cubic Feet Per Acre)

An

nu

al

Vo

lum

e I

nc

rem

en

t (C

ub

ic F

ee

t /

Ac

re /

Ye

ar)


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Yield Summary by Treatment: Total Age 37C

um

ula

tive

Mo

rta

lity

(ft3 )

To

tal V

olu

me

Pro

du

ced

(f

t3 )

Qu

ad

ratic

DB

H (

inch

es)

– A

ge

37

T

ota

l Ha

rve

ste

d V

olu

me

(ft3

)

Number of Thinnings 3 4 3 3 1 3 1 0 0

5

10

15

Quadratic Mean DBH 19.0 13.1 13.5 10.2 11.2 12.5 13.0 9.3 11.0


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Langsaeter Study: Observations through Age 37

No firm evidence that a growth/growing stock “plateau” (phase III) was achieved.

Reductions in growing stock, due to thinning, initially resulted in reductions in periodic growth.

More aggressive thinning treatments captured mortality and concentrated subsequent growth on fewer, larger trees (as expected).

Douglas-fir does not stagnate (Phase IV/V) – loses growing stock through aggressive mortality!

No significant “bonus wood” was produced. (i.e. total production was either reduced or stayed the same -- but not increased -- by repeated thinning). Future growth on the thinned 40-50’s?

The 8’x8’ spacing, allowed to achieve RD 0.50 followed by thinning to RD 0.25 produced a nice combination of volume and QMD!

Self-thinning “laws” were validated as useful constructs!


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Langsaeter Study: Shortcomings…

Limited (high) initial planting densities (680 & 1742 tpa)

Small plots Final thinning treatment at total age 22 Most thinning strategies not economically viable

(like LOGS) Single installation on a high site


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Questions / Comments

western mensurationists meeting, kelowna, bc – june 24-26, 2007 1 looking for the plateau in...

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