By Klaus Puettmann & Mike Saunders Department of Forest Resources, University of Minnesota A New Tool for White Spruce Management: Density Management Guides

by Klaus Puettmann & Mike Saundersby Klaus Puettmann & Mike SaundersDepartment of Forest Resources, University of MinnesotaDepartment of Forest Resources, University of Minnesota

A New Tool for A New Tool for White Spruce White Spruce Management:Management:

Density Management Density Management GuidesGuides

Density (Trees/Acre)

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A Maximum Size-Density Line

B Mortality Initiation Line

C Maximum Stand Production Initiation Line

D Crown Closure Line

Management Zone = Fully Stocked


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Management Zone = Fully Stocked

AcknowledgementsAcknowledgements This work was funded by Forest

Health Funds through the Northeastern Area State & Private Forestry branch of the U.S. Forest Service.

Special thanks goes to: Glen Erickson, N.C.F.E.S., USFS Chris Peterson, UPM-Blandin Mike Albers, MNDNR Al Jones, MNDNR Steve Katovich, S&P Forestry, USFS

OutlineOutline Basic DMD Theory

A White Spruce DMD

Methodology & Development

Preliminary Results

Application to Management

Conclusions

Q & A

Density management can Density management can be managed through:be managed through:

Planting, site preparation, # of seed trees

Release and TSI

Thinning

A cultural treatment made to reduce stand density of trees primarily to improve growth, enhance forest health, or to recover potential mortality

Den

sity

Age

Density as a function of age

Dia

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Age

Tree size as a function of age

Dia

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Density

Putting those two pieces together:

Diameter as a function of density

log

Dia

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log Density

Take log of density and diameter

log

Dia

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log Density

Lines approach a maximum line = self-thinning line

self-thinning line

A White Spruce DMD:A White Spruce DMD:

Preliminary ResultsPreliminary Results

Fully Stocked


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Management Zone

White White Spruce Spruce

DMD for DMD for the Lake the Lake StatesStates

OverstockedUnderstocked

Example Example 1: 1: Plotting Plotting

A Stand A Stand TrajectoryTrajectory

Density (Trees/Acre)100 200 500 1000 2000

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Age DBHq TPA

10 2.0 1500

20 4.0 1500

30 6.0 1000

40 7.0 800

50 8.0 600

Age 10

Age 20

Age 40

Age 30

Age 50

Stand Trajectories:Stand Trajectories:Unmanaged StandsUnmanaged Stands

Unmanaged stands can follow one of two general trajectories, depending on whether or not ingrowth is included in stand measurements.

Example Example 2: 2:

Unmanaged Unmanaged Stand Stand

TrajectoriesTrajectorieswithout without

IngrowthIngrowth


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Unmanaged Unmanaged Stand Stand

Trajectory Trajectory with with

IngrowthIngrowth


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w/o Ingrowthw/ Ingrowth

Stand Trajectories:Stand Trajectories:Unmanaged Stands (cont.)Unmanaged Stands (cont.)

Regardless of site quality or age, unmanaged stands of the same initial density will approximately follow the same stand trajectory.

However, the higher quality stand will move along a given density trajectory faster than a lower quality stand of the same initial density.

DMDs as Management Tools DMDs as Management Tools II

There are several ways that you can use DMDs for decision-making.

In the simplest case, you can use it to determine if a stand will develop to a desired minimum harvest diameter without thinning.

Example Example 4: 4: To To

Thin or Not Thin or Not to Thin?to Thin?


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Let’s say we measure a stand and find that is has a density of 500 tpa

and a DBHq

of 4.0”.




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We plot the point on the DMD.




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Now assume we are managing for pulpwood and need a mean diameter of 8” at harvest.

Do we need to thin?




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No.

This stand will have little mortality before it

reaches a DBHq

of 8”.




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Now assume we need a mean diameter of 12” at harvest.

Do we need to thin?




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Yes, the stand will develop only to about 7” before it crosses the B Line and mortality begins.




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We should schedule a thinning approximately

when the DBHq

is 7-8”.

DMDs as Management Tools DMDs as Management Tools IIII

Another way that DMDs can be used is for both scheduling and determining the intensity of a thin.

Example Example 5: 5: When When and How and How Much?Much?


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Reviewing the last example, we determined that our stand would grow to 7” before it crossed the B Line and mortality began.



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At this point, we determined that we needed to thin.

But how intense should the thin be?



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Well, as we look at the graph the B Line crosses 12” at about 175 tpa.



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Therefore, we should remove about 300 tpa.



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This will allow the stand to develop to 11” before it crosses the B Line.

We can accept the small amount of mortality beyond that.

Plotting a ThinPlotting a Thin

Low thins remove the smallest trees are from the stand, thereby

increasing the DBHq after the thin.

By the same token, a high thin will

reduce the DBHq and a mechanical

thin will have no effect on DBHq.

Plotting a Thin (cont.)Plotting a Thin (cont.)

Therefore, the type of thin will determine if the trajectory has positive, negative, or no slope, based on how it

affects DBHq.

Low thin

Mechanical thin

High thin

Plotting a Thin (cont.)Plotting a Thin (cont.)

Heavy low thin

Light low thin

The intensity of the thin then determines the length and the amount of upward or downward slope of the lines.

DMDs as Management Tools DMDs as Management Tools IIIIII

DMDs can also be used for determining initial planting density.

Example Example 6: 6: How How

many trees many trees to plant?to plant?


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To use the DMD this way, we have to work backwards from harvest.




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Let’s assume that we want a final harvest

DBHq of 10”.




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By looking where the B Line crosses 10”, we estimate final density to be about 250 tpa.




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Therefore, assuming that we will do only 1 thin and remove about 50% of the trees…




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… initial planting density should be around 500 tpa.




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If you would thin more heavily or if you accepted some mortality near harvest, planting density would increase.




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Also, you may wish to plant more if you can estimate seedling mortality (before they would show up on DMD).

DMDs as Management Tools DMDs as Management Tools IVIV

Now, we can incorporate several of these applications to look at a more complex case.


Let’s assume the following:

1. The current density is 1200 tpa (6’ X 6’)

and the current DBHq is 1.5”.

2. Our minimum harvest diameter is 14”.

3. We have a budget to allow for two thins, and one may be precommercial.

4. We can accept 10% mortality in the stand before we will thin or harvest.


So, the questions are:

1. When, in terms of DBHq, should we

schedule thinnings?

2. What type of thinnings should we use?

3. Can we make some predictions of the intensity of the thinnings required?

Going to the chart …Going to the chart …


Planning an Planning an entire entire

rotationrotation


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First, let’s plot the initial stand conditions.



rotationrotation


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This stand should develop without much mortality until it approaches the B Line.



rotationrotation


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At this point, the stand could be thinned, but the trees are still small.



rotationrotation


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We could either:

1. Thin the trees now precommercially; or

2. Wait a few years until trees are larger.

I chose #2.



rotationrotation


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We wait until the stand develops to a

DBHq of 6” and

a density of 1000 tpa.



rotationrotation


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At this size, a mechanical thin removing every other row is most appropriate.



rotationrotation


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Now, the stand will develop to

about 7” DBHq

before crossing the B Line.



rotationrotation


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Again, I am going to wait for the stand to develop further and accept some mortality.



rotationrotation


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Now, at a DBHq

of 8.5”, we have to thin, but…

What kind?What kind?

and…

How intense?How intense?



rotationrotation


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To answer these questions, we need to figure out what the final harvest density will be.



rotationrotation


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At a harvest

DBHq of 14”,

there will be about 125-150 tpa.



rotationrotation


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If we thin to about 150 tpa, we would remove about 2/3 of the trees.



rotationrotation


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This would require a very intense thin, most likely a low thin that would select for the best crop trees.



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Now, the stand should develop to a harvest

DBHq of 14”

w/o significant mortality.

CautionsCautions

Although DMD are very useful, there are some cautions about their application one should be aware of:

1. No temporal component

2. Only density-dependent mortality

3. Only as good as the data that formed them

4. Should be applied cautiously outside there intended purpose

Cautions (cont.)Cautions (cont.)

Our white spruce DMD should be Our white spruce DMD should be

primarily used to determine the primarily used to determine the

timings of 1timings of 1stst thinnings in white thinnings in white

spruce plantations.spruce plantations.

Application to larger diameter stands and to natural stands should be done cautiously.cautiously.

Conclusions:Conclusions:

Where do we go from here?Where do we go from here?

Future Development IFuture Development I

There are several things ways we are trying to improve this DMD:

1. Finding data from more stands that will improve the accuracy of the DMD

across a wider range of DBHq sizes and

densities.

Future Development IIFuture Development II


2. Installing a long-term thinning study to:

a) Refine placement of B and C lines

b) Incorporate effects of budworm on growth as well as isolate size-density combinations most prone to budworm damage

Example: Example: Elk thermal Elk thermal and hiding and hiding

cover (Smith cover (Smith and Long, and Long,

1987)1987)

Future Development IIIFuture Development III


3. Develop a computerized version of this DMD

Example: Example: ODMD developed by Dave Smith, ODMD developed by Dave Smith, Ontario Forest Research InstituteOntario Forest Research Institute

Documents

By Klaus Puettmann & Mike Saunders Department of Forest Resources, University of Minnesota A New Tool for White Spruce Management: Density Management Guides