2409.12_20
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FOREST SERVICE HANDBOOK
ROCKY MOUNTAIN REGION (REGION 2)
DENVER, CO
FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
Supplement No.: r2_2409.12-2004-1
Effective Date: March 5, 2004
Duration: This supplement is effective until superseded or removed.
Approved: LORRIE S. PARKER
Regional Directives Manager
Date Approved: 02/24/2004
Posting Instructions: Supplements are numbered consecutively by Handbook number and
calendar year. Post by document; remove entire document and replace it with this supplement.
Retain this transmittal as the first page(s) of this document. The last supplement to this
Handbook was 2409.12-2002-4 to 2409.12_70.
New Document(s):
2409.12_20
6 Pages
Superseded Document(s) by
Issuance Number and
Effective Date
2409.12_20 (supplement 2409.12-96-2, 12/09/96) 6 Pages
Digest:
20 – This is a technical supplement that converts the format and style of this chapter to the new
FSH template using the agency’s current corporate word processing software. Although some
minor typographical and technical errors have been corrected, this supplement contains no
changes to the substantive direction in this chapter.
The direction included in this chapter has been developed through the coordinated efforts of
Regions 1, 2, 3, and 4. This coordination was initiated by the leadership of each Region under
the concept of shared services. All four Regions must concur on future changes to this direction.
R2 SUPPLEMENT 2409.12-2004-1
EFFECTIVE DATE: 03/05/2004
DURATION: This supplement is effective until superseded or removed.
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FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
22.22 - Types and Use of Tree Volume and Product Estimators
Stem profile models provide a flexible and accurate framework for determining tree volume.
Their mathematical description of diameters along the bole provides opportunity to scale the tree
with cubic-foot or board-foot rules, or to consider alternative utilization standards.
While profile models require a minimum set of measurements, generally, their accuracy
increases with an increase in the number of measurements taken on the tree. Typical profile
models in use include two-point models using DBH and total height, and multi-point systems
that use additional diameter measurements along the bole.
In a three-point system, the additional measurement is a diameter taken in the upper bole. The
model dictates the height at which the upper stem diameter is taken. Many models specify this
point at about 30 percent of total height. This point is generally down out of the crown and
visible, is easily measured, is in the portion of the bole with the most volume, and serves as a
good conditioning point to predict tree form. Other models provide maximum flexibility by
allowing any number of additional diameter measurements at any height on the bole.
Multi-point models can be localized to a given area, drainage, or even stand by sampling for
upper stem measurements (that is, indication of form). Then only DBH and total height need to
be measured to apply the localized model.
22.3 - Estimating Tree Defect and Net Tree Volume
Three categories of defect, broadly based on how defects occur or how they are estimated, add
together to form total sale defect. These are the basic components used to compute net volume.
They include:
1. Visible defects - Defects that can be estimated during a cruise based on visible
indicators.
Measure and record visible defect for all cruised trees. Follow procedures described in the
"Visible Defect User's Guide."
2. Hidden defects - Internal defects that have no visible indicator to provide an indication
of the presence or extent of the defect.
Hidden-defects include internal defects which are not readily evident through external indicators.
A wide range of factors affect the presence of hidden rots and other hidden defects. Species is a
primary factor used to group trees for assigning hidden defect. Age or size, and growing-site
conditions are other common factors. Estimate hidden-defect separately for specific categories
of trees that have been shown to have similar types and amounts of hidden defect.
R2 SUPPLEMENT 2409.12-2004-1
EFFECTIVE DATE: 03/05/2004
DURATION: This supplement is effective until superseded or removed.
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FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
Estimate hidden-defect amounts by: 1) making informal estimates, 2) making formal
comparisons based on data from past studies or post-scale monitoring, or 3) conducting fallbuck-and-scale (FBS) studies within the sale area. Choose an estimation method that is as
accurate as possible, but commensurate with the variability and amount of defect expected, and
the value of the product affected.
Informal estimates include local or Regional factors based on past general experience, usually
from mill-site scaling. These estimates do not usually include formal analysis and
documentation of area-specific data. In making informal estimates, adjust mill-scaling values to
compensate for defect left on-site (increase to mill-scale values), and for defect that will be
counted as visible-defect during the cruise (reduction to mill-scale values).
Formal comparison includes area-specific analysis used to develop geographical comparisonareas based on FBS studies or post-sale monitoring conducted within the last 10 years. Structure
the boundaries to fit data and general knowledge of site and tree conditions. Break comparison
data into groups based on species, DBH class, or other factors that affect hidden-defect amounts.
Include just the hidden-defects from the FBS studies or monitoring activities. Exclude breakage
and visible-defects which may have also been recorded during the study or monitoring activities.
Document the analysis used to derive hidden-defect estimates for comparison-areas. Maintain
the records in a separate 2440 file for each comparison area. Include the following items:
a. FBS records, or other scale sheets, separated and labeled by sale or location (base
data).
b. A tabulation of each group's hidden defect, including subtotals by individual sale
area or location.
c. A short summary that provides a description of the comparison area's site and
group tree characteristics. These form points of comparison that can be used to
evaluate how well a sale area matches when making a hidden-defect estimate.
Fall, buck, and scale (FBS) studies are site-specific samples taken from the population of cruised
trees. These are relatively costly compared to other estimation methods. FBS study procedures
are described in section 22.42 of this supplement and the parent text.
3. Breakage - Defect that results from damage during felling, yarding or loading.
Breakage is the normal breakage expected to occur during the felling process. Base breakage
estimates on observation or factors derived from local studies made in conjunction with felling
activities on timber sales. Although there may be exceptions, breakage does not usually exceed
one or two percent of the gross volume for trees which have been felled within normal contract
conditions. For breakage studies, measure the percent of gross volume lost to breakage as well
R2 SUPPLEMENT 2409.12-2004-1
EFFECTIVE DATE: 03/05/2004
DURATION: This supplement is effective until superseded or removed.
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FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
as the physical features of the timber and terrain which may affect breakage. Physical features
that may affect breakage include:
a. Tree species.
b. Tree size.
c. Slope.
d. Terrain features (broken ground, rocks, and so forth).
e. Volume per acre.
22.31a - Volume Distribution in Trees
For alternative displays of the tables provided in the parent text use the Regional tables and
charts, provided in the "Visible-Defect User's Guide".
22.42 - Fall, Buck, and Scale
1. In addition to items listed in the parent text, use Fall, Buck, and Scale (FBS) studies
to:
e. Determine hidden defect where an adequate basis for comparison is not available.
f. Monitor the application of visible-defect guides.
Notify the appropriate Measurement Specialist of all planned FBS studies. Specialists may
choose to participate to collect more intensive data than would otherwise be required. Retain
FBS logs as needed to provide an opportunity for a remote check scale, and for prospective
purchasers to make their own assessment of defect. If local conditions make retention of logs
impractical, coordinate check-scale and review activities to run concurrent with the study or
immediately after its completion.
3. Sample Selection. Select FBS sample trees in an unbiased random fashion from
cruise trees that are within the targeted population. Base the number of study trees on desired
objectives, suspected level of defect, and the volume in the target population. As a guide select a
minimum of 10 samples for each 1000 CCF of the targeted population, up to a maximum of 40
samples for the sale, when the suspected hidden-defect is 20 percent or less. For sales with
suspected hidden-defect in excess of 20 percent, select a minimum of 15 trees per 1000 CCF up
to a maximum of 60 for the sale. Select additional samples if unusual or unexpected results are
found during the initial study.
R2 SUPPLEMENT 2409.12-2004-1
EFFECTIVE DATE: 03/05/2004
DURATION: This supplement is effective until superseded or removed.
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FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
4. Field Procedures. Use safe falling practices and proper techniques to prevent injury
and to minimize breakage or damage to residual trees. Use certified scalers to scale logs on FBS
studies. Objectives for most FBS studies require tracking more information than would be
needed for mill-scaling situations. Use appropriate forms.
Copy cruise data onto the FBS form before sample trees are cut down. Re-evaluate each sample
for visible-defect as a check against the cruise information, and to provide data to compare
against actually scaling results.
Use a tape to measure tree length from the butt to the tip, and to the top diameters appropriate for
local utilization specifications. Complete these measurements before bucking into segments and
record as total lengths, not increments. These measurements are used to monitor volume
estimators.
Buck logs into segments and scale according to procedures specified in FSH 2409.11a,
utilization standards specified in FSH 2409.12, chapter 10, and guidelines described below:
a. FBS studies represent a chance to critically examine the nature of defects. Except
when loss of lumber utilization would be excessive, chase out defects to determine
their exact character. This means rot showing on one end only should be chased
rather than applying a projection rule intended for yard scaling.
b. Determine log lengths with priority given to minimizing defects and secondly to
bucking trees into 16-foot segments. When the remaining merchantable length
exceeds a 20-foot piece plus trim, divide the remaining piece as prescribed in the FSH
2409.11a.
5. Records. Use the worksheet format and specific instructions provided in the Tree
Defect Guide. Include a summary of the results of a specific FBS study in the individual sale
folder. Forward a copy of the FBS worksheets to the Regional Office so the data can be used for
Regional monitoring and analysis.
Use qualified individuals to compile and analyze FBS data. Consult with a Measurement
Specialist as needed. Summarize the analysis on a cover sheet that:
a. Identifies the qualified individual(s) making the analysis.
b. Describes the general sale conditions that may be used as points of comparison on
other sales.
c. Describes the specific character of each category that was studied.
d. Provides a tabular display of the following data:
R2 SUPPLEMENT 2409.12-2004-1
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DURATION: This supplement is effective until superseded or removed.
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(1) Species.
(2) Dbh-class.
(3) Number of trees.
(4) Gross volume.
(5) Scaled visible-defect percent.
(6) Scaled hidden-defect percent.
(7) Final adjusted hidden-defect percent; footnote the reason for any adjustments
other than scientific rounding.