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FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20
– ESTIMATING TREE VOLUMEN AND WEIGHT
Supplement No.: r4_2409.12-2003-1
Effective Date: November 5, 2003
Duration: This supplement is effective until superseded or removed.
Approved: JACK G. TROYER
Regional Forester
Date Approved: 10/22/2003
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 2409.12-2002-3 to 2409.12_60.
2409.12_20 6 Pages New Document(s):
Superseded Document(s) by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
Region's 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.

R4 SUPPLEMENT 2409.12-2003-1
EFFECTIVE DATE: 11/5/2003
DURATION: This supplement is effective until superseded or removed.
FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
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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.

R4 SUPPLEMENT 2409.12-2003-1
EFFECTIVE DATE: 11/5/2003
DURATION: This supplement is effective until superseded or removed.
FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
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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

R4 SUPPLEMENT 2409.12-2003-1
EFFECTIVE DATE: 11/5/2003
DURATION: This supplement is effective until superseded or removed.
FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
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Page 4 of 6 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.

R4 SUPPLEMENT 2409.12-2003-1
EFFECTIVE DATE: 11/5/2003
DURATION: This supplement is effective until superseded or removed.
FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
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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:

R4 SUPPLEMENT 2409.12-2003-1
EFFECTIVE DATE: 11/5/2003
DURATION: This supplement is effective until superseded or removed.
FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
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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.