2409.12_20
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FOREST SERVICE HANDBOOK
GRAND MESA, UNCOMPAHGRE AND GUNNISON (R2)
NATIONAL FORESTS
FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
Supplement No.: 2409.12-2005-2
Effective Date: November 15, 2005
Duration: This supplement is effective until superseded or removed.
Approved: CHARLES S. RICHMOND
Forest Supervisor
Date Approved: 10/24/2005
Posting Instructions: Supplements are numbered consecutively by Handbook number and
calendar year. Post by document; remove the 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 2409.12-2005-1, 11-15-2005 to Chapter 10.
New Document
24.09.12 20
6 Pages
Superseded Document(s) by
Issuance Number and
Effective Date
2409.12 10 (Supplement 2409.12-93-1,
08/30/1993)
7 Pages
Digest:
22.3 – Revises the applicability of the policy to include all aspen products.
22.31a – Revises the cruising utilization standard for aspen products other than sawlogs.
Revised the table that displays the percentage distribution of tree volume.
22.31b –Removes the 50 percent minimum restriction for soft rot defect deduction. Clarifies use
of guidelines in defecting aspen displaying Phellinus tremulae conks.
22.31c – Clarifies intent of wording.
22.31d –Clarifies intent of wording.
GMUG SUPPLEMENT
EFFECTIVE DATE:
DURATION: This supplement is effective until superseded or removed.
2409.12_20
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FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
22 – TREE VOLUME DETERMINATION
22.3 – Estimating Tree Defect and Net Tree Volume
The following policy will be used for cruising and defecting aspen, which will be offered for sale
as products other than sawlogs (POL). Whether the timber products are processed as waferboard
or other products in the local area is not a consideration in determining the manner of estimating
tree defect.
The objective of cruising and defecting is to determine the net amount of usable fiber, which a
given tract of timber can produce. The cruiser should assume bucking of trees for maximum
utilization. Use instructions in section 22.31a as an aid in determining the percentage of defect
in trees. Applicable defect shall be determined for rot, voids, scars, cankers, crook and sweep.
No defect shall be deducted for stain.
The guidelines in this supplement shall be used to prepare cruise plans.
22.31a – Volume Distribution in Trees
Piece Length. Cruising aspen will be by 8 foot pieces. A piece must be at least 8 feet long to be
considered for merchantablility, but any length greater than 8 feet will also be considered.
Percent Net of Gross. The minimum piece length (8 feet) containing less than or equal to 50%
defect will be considered merchantable.
Percentage Distribution of Tree Volume by 16-Foot Segments
and Segment Position (Based on a Form Class of 80)
Log length
Number of 16’
segments
16.5’
1
Number of 16 Foot Pieces
24.5’
32.5’
40.5’
48.5’
1½
2
2½
3
Percent of Total Tree Volume
Butt
100
74
58
51
45
2nd
--26
42
36
33
rd
3
------13
22
4th
----------th
5
----------Note that the first segment contains two-8 foot pieces.
56.5’
3½
64.5’
4
72.5’
4½
39
31
22
8
---
37
28
21
14
---
33
26
20
15
6
GMUG SUPPLEMENT
EFFECTIVE DATE:
DURATION: This supplement is effective until superseded or removed.
2409.12_20
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FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
22.31b – Rots
Phellinus tremulae (fomes ignarius) is the most common fungus encountered in aspen. Rot is
deductible defect when it meets one of two criteria:
1. Rot is so well advanced that a void is present or the fiber is so loose that it may be
removed literally by the handful. When this condition is evident, an appropriate
length deduction shall be taken to reflect this defect.
2. If a cross-section of the bole would show the presence of “soft” rot. Soft rot is
defined as rot so advanced as to be easily penetrated when probed with a knife blade.
As in criteria #1, a length deduction shall be made to the affected portion of the bole.
This deduction reflects portions of the log, which would shatter when subjected to the
stress of a debarking operation.
The presence of large, well-developed conks is certainly an indicator of rot, but whether it is
deductible as stated in criteria 1 or 2 noted above is best determined by use of an increment
borer, chainsaw or the experience of the cruiser. A fall, buck and scale method of determining
defect may be necessary in high defect stands. It is appropriate for cruisers and check cruisers to
use these methods to aid in determining defect.
For example, if it is determined that the lower 2 feet of a 2 ½ segment tree (based upon 16-foot
segments) meets the above criteria, the defect for that tree is 2/16 x 51% = 6.38% or 6% defect.
The following guidelines provide uniformity in defecting aspen displaying Phellinus tremulae
conks:
1. Aspen showing one average size (approximately four inches across) or two smaller
conks per tree – no defect.
2. Aspen showing two average size conks located on separate 8-foot pieces of the bole
or several smaller conks – no defect as a general rule. Discretion may be applied for
determining defect if the cruiser warrants.
3. Aspen showing three or more average sized conks or numerous (5+) smaller conks on
the bole should be defected by making a length deduction between the conks in
addition to two feet above and below the conks.
These three guidelines are not intended to be absolute. Each tree must be examined individually
relative to these guidelines and the presence of other factors such as scars, cankers, crook, and
sweep. The magnitude of factors indicates the magnitude of defect deductions.
GMUG SUPPLEMENT
EFFECTIVE DATE:
DURATION: This supplement is effective until superseded or removed.
2409.12_20
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FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
22.31c – Sweep and Crook
Minor amounts of crook and sweep are allowable and result in no defect deduction. If a tree
contains more than a minor amount of crook or sweep, a deduction must be made in as much as
that piece of the tree is unusable.
To determine of a crook or sweep is more than minor, imagine a tape or string stretched tightly
center to center between the ends of a minimum 8-foot long piece. If the tape deviates from the
edge of the piece, excessive crook is present. This piece will not go through a debarker and must
be culled.
With sweep, when the tape is stretched tightly center to center between the ends of a minimum 8foot long piece, the tape may deviate from the edge by 2 inches and still be merchantable.
However, if bucking for maximum utilization can produce 8-foot pieces without the major crook
or sweep, no cull should be taken.
See exhibits 1 and 2 that further illustrate these points.
22.31d – Missing Wood
Voids. A deduction must be made for missing material. Use standard scaling and cruising
procedures to determine the amount of defect deduction. Use pie cuts, length cuts or portions of
a length cut to determine the percentage of defect. For example, a void affecting ½ of a four-foot
piece on the butt log of a 2-segment tree (based upon 16-foot segments) would be calculated as
follows:
4/16 X ½ X 58% = 7.25% rounded to 7%
Cankers and Burls. Only cankers caused by Ceratocystis fimbriata (black canker or target
fungus) are deductible. This canker forms successive annual rings of hard, dry callus tissue,
which is unusable. Minor cankers involving ¼ or less of the circumference of the bole may
indicate no defect. Cankers involving more than ¼ of the circumference of the bole should be
defected with a length cut. As an example: Assume a four-foot long canker at the bottom of the
second segment of a 2 ½ segment tree (based upon 16-foot segments) and a five-foot long canker
at the top of the top of the same 16-foot segment. Each canker involves more than ¼ of the
circumference of the bole, so length cuts must be taken for each canker. After taking the length
cuts, the remaining piece of the segment is less than eight feet (16’ segment – 4’ length cut – 5’
length cut = 7’ piece). Therefore the entire second segment of the tree is cull, resulting in a 36%
defect deduction.
Burls are handled in the same manner as cankers.
GMUG SUPPLEMENT
EFFECTIVE DATE:
DURATION: This supplement is effective until superseded or removed.
2409.12_20
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FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
Exhibit 1 – Crook
In this case, the lower 8 feet of the tree contains crook whose imaginary string line diverges from
the edge of the bole and is therefore unusable. However, the upper 4 feet of this piece should be
attached to the next log and the defect calculated as follows: 4/16 X 74% = 18.5% rounded to
18%. The principle of bucking for maximum utilization is applied in this illustration in that only
the lower 4 feet of the butt log will be culled, while the upper 4 feet of the butt log will remain
attached to the next log.
GMUG SUPPLEMENT
EFFECTIVE DATE:
DURATION: This supplement is effective until superseded or removed.
2409.12_20
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FSH 2409.12 – TIMBER CRUISING HANDBOOK
CHAPTER 20 – ESTIMATING TREE VOLUME AND WEIGHT
Exhibit 2 – Sweep
In evaluating sweep, the imaginary string line may diverge from the log by up to 2 inches and
still be a merchantable piece.