Looking for the Plateau in Douglas-fir Annual Volume Increment

David M. Hyink, Ph.D. (retired) Timberlands & Raw Materials R & D Weyerhaeuser Company 1

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

Outline/Topics

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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

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

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Forest Growth & Yield and Wood Quality

What 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”

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

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Forest Growth & Yield and Wood Quality

Scientific 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.

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

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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.

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

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Biological First Principles / “Laws” of Self-Thinning 0.15

0.15

0.55

0.55

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

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

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The Langsaeter Study

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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

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

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Self-Thinning / Reineke’s Stand Density Index

2440 1480 5’x5’ 900 8’x8’ 550 330

Source: Husch, Beers & Kershaw,

Forest Mensuration

- 4 th Edition

200 3.5 5.2 7.8 11.6 17.3

Quadratic mean dbh (in.) 8

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

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

116 Mean Tree Volume (ft 3 ) 39 28 Maximum Size-Density 0.15

13 0.55

0.15

0.55

1.4

0.5

221 0.15

0.55

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

384 665 1153 1998 Trees Per acre 9

Growth vs. Growing Stock / Langsaeter’s Hypothesis

Source: USFS Research Paper PNW-RP-537

5 4 3 2 1 Volume (Cunits/acre) Age 23 5 4 3 2 1 Volume (Cunits/acre) Age 17 0 20 40 60 80 100 5 4 3 2 1 Volume (Cunits/acre) Age 35 0 20 40 60 80 100

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

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Growth vs. Growing Stock / Langsaeter’s Hypothesis

Source: USFS Research Paper PNW-RP-537

Age 23 Volume (Cubic feet /acre) Age 17 Volume (Cubic feet /acre)

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

Volume (Cubic feet /acre) Age 35 11

Langsaeter: Growth / Growing Stock – Age 23

Volume (Cubic feet per acre)

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

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Langsaeter: Growth / Growing Stock – Age 35

Volume (Cubic Feet Per Acre)

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

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Yield Summary by Treatment: Total Age 37

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

15 10 5

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

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

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Langsaeter Study: Observations through Age 37

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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!

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

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Langsaeter Study: Shortcomings…

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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

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

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Questions / Comments

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

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