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FSH 2409.17 - SILVICULTURAL PRACTICES HANDBOOK
R-1 SUPPLEMENT 2409.17-94-1
EFFECTIVE January 26, 1994
CHAPTER 9 - TIMBER STOCKING GUIDES AND GROWTH PREDICTIONS
9.04d - Forest Silviculturists. Forest Silviculturists shall provide direction for creating
additional stocking charts. Where Land Management Direction is unique to a Forest, or where
the expected response to stocking control is different for specific geographic areas (Forests)
and/or different habitat types, additional management zones may be needed.
9.06 - Theory and Concepts. The Regional Stocking Guides display an Average Maximum
Density (AMD) which indicates the highest densities that can be found under average forest
conditions. Stands at or above this density can generally be expected to stagnate or to suffer
stress and significant mortality. The density of managed stands should be maintained at some
level below the AMD depending upon resource objectives specified in the Forest Plan. Very
low stand densities provide each tree freedom to grow, but densities below the management zone
will not produce the maximum per acre board foot volume possible for the site over the index
period of 100 years assumed in the example charts. Resource objectives should seldom, if ever,
require stand densities less than the lower level of the management zone. Stand densities at or
above the upper level of the management zone present a dilemma because the stand will become
subject to increased stress related mortality. The curves on the stocking charts do not indicate
the course of stand development. They show the densities for any given Quadratic Mean
Diameter (QMD) that will result in a certain volume production over the index period of 100
years.
9.11b - Format. Regional stocking charts are provided for basal area by quadratic mean
diameter in addition to the standardized format required by the Washington Office.
The management zones are for a specific objective measured on a 100-year rotation. Arrows on
the stocking charts point to the nearest whole QMD value that is attained by the 100-year
rotation period.
9.12 - New Regional Stocking Guides. The stocking guides consider the variables of species
(80 percent plus by basal area), geographic areas within the Region, and habitat type groups for
each geographic area. Statistical tests were used to select curves based on Stand Density Index
(SDI) values and AMD. The AMD comes from an analysis of stands in the Region.
Management Zones on a stocking chart will vary according to the management objectives. To
provide basic Regional Guides, we assumed an objective of maximizing board foot volume at an
assumed rotation of one hundred years. This management objective was developed by using the
prognosis regeneration establishment model to create stands of various densities from R1-Edit
stand exam data. Projected volumes were compared at age 100 years.
The range of stocking levels that provided volumes within 90 percent of the maximum were used
to develop the regressions for the upper and lower zones.
Stocking charts will apply to both single and mixed species stands. In stands in which a single
species does not make up more than 80 percent of the basal area, a stocking curve will be
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selected based on the species that will be favored to leave in cultural operations. Three figures
are provided for each stocking chart; two on the standard format, and one Basal Area over QMD.
As it is difficult to interpolate for small QMDs from the figures, a table is provided for the
number of trees per acre for QMDs of 1 through 3 inches.
REGIONAL STOCKING CHARTS
- White pine
- Larch
- Idaho: Douglas-fir, habitat type group #1
- Idaho: Douglas-fir, habitat type group #2
- W. Montana: Douglas-fir, habitat type group #1
- W. Montana: Douglas-fir, habitat type group #2
- W. Montana: Douglas-fir, habitat type group #3
- Eastern Montana: Douglas-fir
- Grand fir
- Western Hemlock
- Cedar, habitat type group #1
- Cedar, habitat type group #2
- Idaho/Western Montana: lodgepole pine
- Eastern Montana: lodgepole pine
- Spruce
- Idaho: Subalpine fir
- Montana: Subalpine fir, habitat type group #1
- Montana: Subalpine fir, habitat type group #2
- Ponderosa pine
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
Appendix H
Appendix I
Appendix J
Appendix K
Appendix L
Appendix M
Appendix N
Appendix O
Appendix P
Appendix Q
Appendix R
Appendix S
NUMBERS OF TREES FOR SMALL QMDS - Appendix T
The following Forests comprise the geographic areas considered in the development of Regional
Stocking Charts:
Western Montana: Kootenai, Lolo, Flathead, and Bitterroot
Eastern Montana: Lewis & Clark, Gallatin, Helena, Deerlodge,
Custer, and Beaverhead
The following are habitat types groups used in the stocking charts. Curves were grouped where
differences were not statistically significant.
Idaho: Douglas-fir, ht grp #1
THPL/CLUN
THPL/ATFI
THPL/OPHO
TSHE/CLUN
ABGR/CLUN
530
540
550
570
520
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Idaho: Douglas-fir, ht grp #2
ABLA/CLUN
ABLA/VACA
ABLA/MEFE
ABLA/XETE
620
640
670
690
PSME/PHMA
PSME/SYAL
PSME/CARU
260
310
320
TSME/MEFE
TSME/XETE
680
710
PICEA/CLUN
420
421,422
W MT: Douglas-fir, ht grp #1
PICEA/LIBO
470
ABGR/CLUN
520
521,522,523
THPL/CLUN
530
531,532,533
TSME/CLUN
570
W MT: Douglas-fir, ht grp #2
ABLA/CLUN
620
621,622,623,624,625
ABLA/LIBO
660
662
W MT: Douglas-fir, ht grp #3
PSME/VACA
PSME/PHMA
250
260
261,262
PSME/SYAL
310
312,313
PSME/CARU
320
322,324
PSME/SPBE
340
PSME/VAGL
280
281,283
PSME/CARU-CARU
323
PSME/CAGE
330
PSME/LIBO
290
291,292,293
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W MT: Douglas-fir, ht grp #3 (continued)
ABGR/XETE
ABLA/CARU
ABLA/VACA
510
750
640
641
ABLA/XETE
690
691,692
ABLA/VAGL
720
ABLA/VASC-CARU
731
ABLA/MEFE
670
ABLA/ALST
740
ABLA/LUHI-MEFE
832
TSME/MEFE
680
Cedar: ht grp #1
THPL/CLUN
THPL/ATFI
THPL/OPHO
Cedar: ht grp #2
All other
habitat types
MT: Subalpine fir, ht grp #1
PICEA/VACA
530
540
550
450
ABLA/CLUN
620
621,622,623,624,625
ABLA/VACA
640
641
ABLA/LIBO
660
662
ABLA/XETE
690
691,692
ABLA/LIBO-VASC
663
ABLA/VAGL
720
ABLA/VASC-CARU
731
MT: Subalpine fir, ht grp #2
All other
habitat types
STOCKING VALUES FOR AVERAGE MAXIMUM DENSITY
- White pine
- Larch
- Idaho: Douglas-fir, ht grp #1
- Idaho: Douglas-fir, ht grp #2
- Western Montana: Douglas-fir, ht grp #1
|
| MAX
| SDI
| BA
--------------------| 6101/ | 440
557
| 400
| 444
| 325
| 390
| 275
436
| 320
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1/ Taken from TB 323, Haig, 1932
STOCKING VALUES FOR AVERAGE MAXIMUM DENSITY
(continued)
|
| MAX
| SDI
| BA
---------------------
- Western Montana: Douglas-fir, ht grp #2
- Western Montana: Douglas-fir, ht grp #3
- Eastern Montana: Douglas-fir
- Grand fir
- Western Hemlock
- Cedar, ht grp #1
- Cedar, ht grp #2
- Idaho/Western Montana: lodgepole pine
- Eastern Montana: lodgepole pine
- Spruce
- Idaho: Subalpine fir
- Montana: Subalpine fir, ht grp #1
- Montana: Subalpine fir, ht grp #2
- Ponderosa pine
| 463
| 398
| 436
| 474
| 490
| 547
| 615
| 524
| 550
| 435
| 429
| 566
| 464
| 460
| 325
| 280
| 320
| 340
| 350
| 390
| 480
| 375
| 380
| 305
| 305
| 405
| 325
| 325
9.2 - Use of Stocking Level Charts. Optimum stocking levels are needed to identify "target
stands" for given management objectives. They are to be used in evaluating existing stands in
the diagnosis step of the silvicultural prescription process.
The management zones shown on the charts are included to meet national standards. They are
based upon certain assumptions which may not depict individual situations.
Stand history and structure must be considered in applying the stocking levels. Stocking levels
from the charts cannot be applied to "older" stands that have been overstocked for prolonged
periods of time. The response to a change in density in these stands will not have the same
results as for stands whose stocking has been within the management zone. THE STOCKING
CHARTS ARE APPROPRIATELY USED FOR EXISTING YOUNG
STANDS AND
DEFINING TARGET STAND OBJECTIVES FOR STANDS TO BE REGENERATED. THE
STANDS MUST BE EVEN-AGED HAVING A NORMAL DISTRIBUTION OF
DIAMETERS.
Example 1 - Use of stocking charts. An even-aged stand that is predominantly larch with some
Douglas-fir has a QMD of 2.8 inches with 1,359 trees per acre. This existing stocking level is
within the range identified by our stocking chart for our specified management objective. A
starting point for analysis of comparing our existing stand to our "target stand" is that "no
treatment" is a viable alternative to be considered. This alternative however excludes the
opportunities to improve species composition by making Douglas-fir a larger proportion of the
stand; to reduce the incidence of diseased or damaged trees that may be present; and to improve
the economics of the final harvest by increasing the QMD and reducing the variation in the
diameter distribution.
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An analysis of alternatives in the same frame that the Management Zone was defined can be
made using the stocking charts and the prognosis model. The stocking trajectories of two
alternatives are superimposed on the chart; one without any treatment, and one with an
immediate pre-commercial thinning to 400 trees per acre (9.2 - Exhibit 01). The table in 9.2 Exhibit 01 shows that although the pre-commercial thinning as projected by prognosis does not
provide any gain in volume (actually 3% less), it does make a difference in the QMD by the
specified rotation age.
Alternatives with commercial thinnings can be analyzed. A thinning can be made when the
stand attains a QMD of 8 inches to a residual basal area of 150 square feet. In applying the
commercial thinning by removals from below, we find the variation in diameters results in an
increase in the post thinned stand QMD of over 12 inches. For this QMD, our stand is below
our management zone. An additional alternative thinning to only 180 square feet may be more
viable. Both stand trajectories are displayed in 9.2 - Exhibit 02.
Additional alternatives such as thinning from above to 150 square feet or doing both a
pre-commercial and commercial thinning can be analyzed (9.2 - Exhibit 03). Section 9.2 Exhibit 04 displays attributes of all six alternatives considered.
For the stand being analyzed, our management objective of maximizing board foot volume by
rotation age can be met by a number of alternatives. The selection of a given alternative is
dependent upon our need to take advantage of the opportunities that stocking control treatments
present. The probability of actually achieving our target stand and carrying to the end of the
rotation will be greatly enhanced by providing greater species diversity, reducing the incidence
of damaged and diseased trees, and taking advantage of phenotypic expression of numerous
traits.
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9.2 - Exhibit 01
SEE THE PAPER COPY OF THE MASTER SET
FOR SECTION 9.2 - EXHIBIT 01
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9.2 - Exhibit 02
SEE THE PAPER COPY OF THE MASTER SET
FOR SECTION 9.2 - EXHIBIT 02
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9.2 - Exhibit 03
SEE THE PAPER COPY OF THE MASTER SET
FOR SECTION 9.2 - EXHIBIT 03
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9.2 - Exhibit 04
SEE THE PAPER COPY OF THE MASTER SET
FOR SECTION 9.2 - EXHIBIT 04
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Example 2 - Use of stocking charts. A stand that is predominantly larch has approximately
2,100 stems per acre at a QMD of 3 inches. This is above the upper limit identified by our
stocking charts (1,800 trees per acre). A pre-commercial thinning for this stand should be
considered. 9.2 - Exhibit 05 displays the stand trajectories for both no treatment and an
immediate precommercial thinning . The table in 9.2 - Exhibit 05 displays that the thinning as
projected by prognosis provided an increase in both QMD at the time of final harvest and also in
total standing board foot volume (11%) as compared to an alternative of "no treatment".
Section 9.2 - Exhibit 06 displays a number of other alternatives involving commercial thinning.
The table in 9.2 - Exhibit 07 displays the attributes taken from prognosis projections of all
alternatives examined. Since the initial stocking level of the stand was above our management
zone, a treatment can provide more than a 10 percent increase in the standing volume at the end
of the rotation. The precommercial thinning provides the maximum standing volume at the end
of the rotation. Compared to the maximum standing volume that we can produce, the
commercial thinning alternatives as projected by prognosis produce less standing volume. The
thinnings to 125 and 150 square feet of basal area are outside the management zone and result in
more than a 10 percent difference. The thinning to 125 square feet produces 83 percent and
thinning to 150 square feet produces 81 percent. Even when the removals are added in we still
do not produce as much volume as that standing at the end of the rotation with a pre-commercial
thinning only. An alternative of having both a pre-commercial and commercial thinning was
not displayed as there is not enough basal area to remove to result in a significant volume. Even
with the thinnings to 125 and 150 square feet the removals were only slightly over 3,000 board
feet.
The selection of an alternative that includes reducing the stocking level to within our
Management Zone will definitely help this stand attain our management objective. However,
the selection of an alternative that includes commercial thinning must depend on factors other
than an "increase in board foot volume yields." The opportunities to exert continued control
over species composition, stand structure, incidence of disease and damage are very viable
reasons for selecting alternatives with commercial thinnings. Additional consideration beyond
the individual stand level must be given for the need to maintain Forest wide yields via a
component other than final harvests.
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9.2 - Exhibit 05
SEE THE PAPER COPY OF THE MASTER SET
FOR SECTION 9.2 - EXHIBIT 05
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9.2 - Exhibit 06
SEE THE PAPER COPY OF THE MASTER SET
FOR SECTION 9.2 - EXHIBIT 06
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9.2 - Exhibit 07
SEE THE PAPER COPY OF THE MASTER SET
FOR SECTION 9.2 - EXHIBIT 07
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Example 3 - Use of stocking charts. Section 9.2 - Exhibit 08 displays two land management
regimes developed to attain specific objectives identified in a Forest Plan. Instead of a zone,
these objectives have been expressed as only single values over time. Both objectives plan for
essentially the same volume production. The change in resource emphasis is not planned to
make a difference in volume production. Placing the quantification of these regimes on the
stocking chart format enables a comparison. From this comparison the regime that has the
emphasis on hiding cover is within the zone for maximizing timber although it is near the upper
end. The regime for the timber-only emphasis actually drops out of the management zone on
the stocking chart. Some loss of volume might be expected as the result of increasing the stand
QMD at harvest time.
The use of the stocking chart format for comparison helps to point out the need to further analyze
the timber-only regime. Do we need to increase stocking levels to avoid any volume loss, or do
we need to reword our objectives to achieve a certain QMD at a possible loss of standing volume
at the time of final harvest?
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9.2 - Exhibit 08
SEE THE PAPER COPY OF THE MASTER SET
FOR SECTION 9.2 - EXHIBIT 08