ASTM D5536-17(2023)

Standard Practice for Sampling Forest Trees for Determination of Clear Wood Properties

SIGNIFICANCE AND USE
4.1 This practice covers procedures of sampling for obtaining small, clear wood specimens which, when tested in accordance with Test Methods D143 and, in conjunction with full-size product tests, will provide mechanical properties for use in deriving design properties for lumber, panels, poles, house logs, and other products.  
4.2 Data obtained by testing specimens sampled in accordance with these methods also provide information on the influence on mechanical properties of such factors as density, locality of growth, position in cross section, height in the tree, and moisture content.  
4.3 Cruciform sampling is of principal value when information is desired on the influence on mechanical properties of height in the tree; of age or radial position in the tree; of rate of growth; the change from sapwood to heartwood; the relationships between mechanical properties and factors such as specific gravity; and making general comparisons between species for purposes of rating or selecting species for specific end-use products. Cruciform sampling does not provide unbiased estimates of mean values, percentile or other descriptive statistics, or a means of associating statistical confidence with estimates of descriptive statistics.  
4.4 Double sampling is used when it is desired to improve or update existing estimates of mechanical property values that are the basis for establishing allowable design stresses for stress-graded lumber, plywood, poles and piling, and other wood products. The method involves predicting one property by carefully observing a well-correlated auxiliary property that is presumably easier or cheaper to measure. A sample estimate of the auxiliary property is obtained with a high degree of precision by representatively sampling the population. A smaller independent sample or a subsample of the large sample is used to establish a relationship between the auxiliary property and the property for which an estimate is desired. As applied to sampling a f...
SCOPE
1.1 This practice offers two alternative physical sampling procedures: cruciform sampling and random sampling. The choice of procedure will depend upon the intended use for the test results, the resources available for sampling and testing, and the availability of existing data on the mechanical properties and specific gravity of the species of interest.  
1.2 A third procedure, double sampling, is included primarily by reference. This procedure applies the results of cruciform or random samples through correlation to improve or update property values.  
1.3 Units—The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2023
• ICS: 79.040 - Wood, sawlogs and sawn timber
• Technical Committee: D07 - Wood
• Drafting Committee: D07.08 - Forests

Relations

• Refers: ASTM D2555-17a(2024)e1 - Standard Practice for Establishing Clear Wood Strength Values
• Effective Date: 01-Feb-2024
• Refers: ASTM D2555-17a(2024) - Standard Practice for Establishing Clear Wood Strength Values
• Effective Date: 01-Feb-2024
• Refers: ASTM D143-23 - Standard Test Methods for Small Clear Specimens of Timber
• Effective Date: 15-Nov-2023
• Refers: ASTM D1038-19 - Standard Terminology Relating to Veneer, Plywood, and Wood Structural Panels
• Effective Date: 01-Mar-2019
• Refers: ASTM D2555-17a - Standard Practice for Establishing Clear Wood Strength Values
• Effective Date: 01-Aug-2017
• Refers: ASTM D2555-17 - Standard Practice for Establishing Clear Wood Strength Values
• Effective Date: 15-Apr-2017
• Refers: ASTM D2555-16 - Standard Practice for Establishing Clear Wood Strength Values
• Effective Date: 01-Aug-2016
• Refers: ASTM D2555-15 - Standard Practice for Establishing Clear Wood Strength Values
• Effective Date: 01-Sep-2015
• Refers: ASTM D9-12 - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 15-Oct-2012
• Refers: ASTM D1038-11 - Standard Terminology Relating to Veneer and Plywood
• Effective Date: 01-Nov-2011
• Refers: ASTM D2555-06(2011) - Standard Practice for Establishing Clear Wood Strength Values
• Effective Date: 01-Oct-2011
• Refers: ASTM E105-10 - Standard Practice for Probability Sampling Of Materials
• Effective Date: 01-Oct-2010
• Refers: ASTM D9-09ae1 - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 15-Nov-2009
• Refers: ASTM D9-09a - Standard Terminology Relating to Wood and Wood-Based Products
• Effective Date: 15-Nov-2009
• Refers: ASTM D143-09 - Standard Test Methods for Small Clear Specimens of Timber
• Effective Date: 01-Sep-2009

Overview

ASTM D5536-17(2023) - Standard Practice for Sampling Forest Trees for Determination of Clear Wood Properties - provides essential procedures for the collection and preparation of small, clear wood specimens from forest trees. Developed by ASTM International, this standard ensures reliability and consistency when obtaining mechanical property data crucial for the design and evaluation of wood products such as lumber, panels, poles, house logs, and more.

This practice outlines methods that enable researchers and industry professionals to assess how various natural factors-such as tree density, growth location, cross-sectional position, height in the tree, and moisture content-influence the mechanical properties of wood. The data gathered through this standard is vital for wood product design, grading, and quality assurance.

Key Topics

• Sampling Methods: The standard details two main physical sampling methodologies-cruciform sampling and random sampling-each suited to different research and product development needs. A third procedure, double sampling, is referenced for specialized applications to update property values.

  • Cruciform Sampling: Ideal for understanding vertical and radial variation, effects of growth changes, sapwood-to-heartwood transition, and for comparisons between species.
  • Random Sampling: Used when statistical representation and probability-based estimates of wood property distributions are required.
  • Double Sampling: Applied for refining or verifying existing data, leveraging correlations between easily measured and mechanically significant properties (like specific gravity).

• Representative Specimens: Focuses on obtaining small, defect-free samples (“clear wood”) to minimize the impact of knots and grain irregularities, facilitating accurate comparison and data analysis.

• Mechanical Property Testing: These sampling practices are frequently used in conjunction with ASTM D143, which specifies testing methods for small clear specimens of timber.

• Data Relevance: Test results aid in deriving design properties, such as allowable stresses, for a range of wood products and ensure suitability across different species and growth conditions.

Applications

• Lumber and Structural Products: Data from ASTM D5536-17 samples underpins the structural design and grading of lumber, plywood, poles, and logs.

• Species Comparison: By comparing clear wood properties across different species, industries can select optimal wood types for specific applications.

• Resource Assessment: Forest managers use this standard to evaluate the mechanical properties of timber stands and to guide sustainable harvesting strategies.

• Research and Product Development: Enables detailed study into how site, growth conditions, and age affect wood strength and behavior, informing advances in engineered wood and composite materials.

• Quality Assurance: Assists in verifying that wood products meet required mechanical property specifications, promoting safety and reliability in construction and manufacturing.

Related Standards

• ASTM D143 – Test Methods for Small Clear Specimens of Timber
• ASTM D2555 – Practice for Establishing Clear Wood Strength Values
• ASTM E105 – Guide for Probability Sampling of Materials
• ASTM D9 – Terminology Relating to Wood and Wood-Based Products
• ASTM D1038 – Terminology Relating to Veneer, Plywood, and Wood Structural Panels

These related standards complement ASTM D5536-17, ensuring thorough and consistent approaches to wood specimen sampling, testing, and property evaluation.

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With its comprehensive guidance on forest tree sampling for clear wood properties, ASTM D5536-17(2023) remains an indispensable resource for researchers and industry professionals seeking to ensure the mechanical performance of wood-based products through standardized, reliable testing methods.

Keywords: ASTM D5536-17, clear wood sampling, mechanical properties, forest trees, wood testing, wood design properties, lumber sampling, random sampling, cruciform sampling, double sampling, wood product standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D5536 − 17 (Reapproved 2023)
Standard Practice for
Sampling Forest Trees for Determination of Clear Wood
Properties
This standard is issued under the fixed designation D5536; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The everyday use of wood for many different purposes creates a continual need for data on its
mechanical properties. Small clear specimen testing to characterize a species has historically been
employed for such property determination, and related methods of test are outlined in Test Methods
D143.
Because wood is a biological material, its mechanical properties are subject to considerable natural
variation. Thus, the results of tests to evaluate the mechanical properties of a species depend to a great
extent upon how the forest trees are sampled for test material. Ideally, if the results of mechanical
property evaluations are to be representative of the forest sampled, probability sampling of materials
such as outlined in Practice E105 must be used. However, true probability sampling of the forest trees
for determination of mechanical properties can be extremely complex and expensive because of the
broad geographic range and topographic conditions under which a tree species grows. In some
instances, direct probability sampling may be impractical, necessitating the need for alternative
2,3
sampling procedures.
1. Scope responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.1 This practice offers two alternative physical sampling
mine the applicability of regulatory limitations prior to use.
procedures: cruciform sampling and random sampling. The
1.5 This international standard was developed in accor-
choice of procedure will depend upon the intended use for the
dance with internationally recognized principles on standard-
test results, the resources available for sampling and testing,
ization established in the Decision on Principles for the
and the availability of existing data on the mechanical proper-
Development of International Standards, Guides and Recom-
ties and specific gravity of the species of interest.
mendations issued by the World Trade Organization Technical
1.2 A third procedure, double sampling, is included primar-
Barriers to Trade (TBT) Committee.
ily by reference. This procedure applies the results of cruciform
or random samples through correlation to improve or update
2. Referenced Documents
property values. 4
2.1 ASTM Standards:
1.3 Units—The values stated in inch-pound units are to be
D9 Terminology Relating to Wood and Wood-Based Prod-
regarded as standard. The values given in parentheses are ucts
mathematical conversions to SI units that are provided for
D143 Test Methods for Small Clear Specimens of Timber
information only and are not considered standard.
D1038 Terminology Relating to Veneer, Plywood, and Wood
Structural Panels
1.4 This standard does not purport to address all of the
D2555 Practice for Establishing Clear Wood Strength Values
safety concerns, if any, associated with its use. It is the
E105 Guide for Probability Sampling of Materials
This practice is under the jurisdiction of ASTM Committee D07 on Wood and
3. Terminology
is the direct responsibility of Subcommittee D07.08 on Forests.
3.1 Definitions:
Current edition approved Feb. 1, 2023. Published February 2023. Originally
approved in 1994. Last previous edition approved in 2017 as D5536 – 17. DOI:
10.1520/D5536-17R23.
2 4
Bendtsen, B. A., Freese, F., and Ethington, R. L., “A Forest Sampling Method For referenced ASTM standards, visit the ASTM website, www.astm.org, or
for Wood Strength,” Forest Products Journal, Vol 20, No. 11, 1970, pp. 38–47. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Pearson, R. G., and Williams, E. J., “A Review of Methods for Sampling of Standards volume information, refer to the standard’s Document Summary page on
Timber,” Forest Products Journal, Vol 8, No. 9, 1958, pp. 263–268. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5536 − 17 (2023)
3.1.1 For definitions of terms used in this standard, refer to 5. Authentic Identification
Terminologies D9 and D1038.
5.1 The material shall be from trees selected in the forest by
one qualified to identify the species and to select the trees.
4. Significance and Use
Where necessary, herbarium samples such as leaves, fruit,
twigs, and bark shall be obtained to ensure positive identifica-
4.1 This practice covers procedures of sampling for obtain-
tion.
ing small, clear wood specimens which, when tested in
accordance with Test Methods D143 and, in conjunction with
6. Cruciform Sampling – Primary Method
full-size product tests, will provide mechanical properties for
use in deriving design properties for lumber, panels, poles,
6.1 The standard methods for preparing small, clear speci-
house logs, and other products.
mens of timber, primary method, provide for cutting the log
sections (divided into and identified as bolts) systematically
4.2 Data obtained by testing specimens sampled in accor-
1 1
into sticks of nominal 2 ⁄2 in. by 2 ⁄2 in. (64 mm by 64 mm) in
dance with these methods also provide information on the
cross section, that are later surfaced to provide the test
influence on mechanical properties of such factors as density,
specimens 2 in. by 2 in. (51 mm by 51 mm) in cross section,
locality of growth, position in cross section, height in the tree,
on which the system is based. These methods have served as a
and moisture content.
basis for the evaluation of the various mechanical and related
4.3 Cruciform sampling is of principal value when informa-
physical properties of the clear wood of different species of
tion is desired on the influence on mechanical properties of
wood. These methods have been extensively used, and a large
height in the tree; of age or radial position in the tree; of rate
amount of data based on them have been obtained and
of growth; the change from sapwood to heartwood; the
published.
relationships between mechanical properties and factors such
6.1.1 The 2 in. by 2 in. (51 mm by 51 mm) test specimen has
as specific gravity; and making general comparisons between
the advantage that it embraces a number of growth rings, is less
species for purposes of rating or selecting species for specific
influenced by earlywood and latewood differences than smaller
end-use products. Cruciform sampling does not provide unbi-
specimens, and is large enough to represent a considerable
ased estimates of mean values, percentile or other descriptive
proportion of the material.
statistics, or a means of associating statistical confidence with
6.1.2 The choice of specimen size may be influenced by the
estimates of descriptive statistics.
objectives of sampling and by the rate of growth of the
4.4 Double sampling is used when it is desired to improve material. Radial property gradients are primarily influenced by
or update existing estimates of mechanical property values that age, and large specimens that encompass several rings may
are the basis for establishing allowable design stresses for mask the age influence. Height gradients must be evaluated by
stress-graded lumber, plywood, poles and piling, and other specimens from the same annual ring because of age influence.
wood products. The method involves predicting one property Thus, small specimens are preferred for measuring both radial
by carefully observing a well-correlated auxiliary property that and height gradients. When the purpose of sampling is to
is presumably easier or cheaper to measure. A sample estimate estimate clear wood properties, large specimens that include a
of the auxiliary property is obtained with a high degree of number of annual rings are preferred. Even with 2 in. by 2 in.
precision by representatively sampling the population. A (51 mm by 51 mm) specimens, fast rates of growth will result
smaller independent sample or a subsample of the large sample in few rings per specimen. Regardless of the purpose of
is used to establish a relationship between the auxiliary sampling, the analysis and reporting of data may require
property and the property for which an estimate is desired. As careful consideration of the character of the specimen.
applied to sampling a forest, double sampling has employed
6.2 Selection of Number of Trees—For each species to be
specific gravity to predict mechanical properties. The double-
tested, select the number and the character of the trees to
sampling method provides unbiased estimates of mean me-
accomplish the purpose of the sampling. For traditional me-
chanical property values and an approximation method for
chanical property data base development, a minimum of five
estimating percentile values. Statistical confidence may be
trees have usually been selected that have been judged “rep-
associated with the estimates of the means but not the
resentative” of the trees harvested of the species. Note that if
percentile values.
unbiased estimates and statistical confidence statements are
4.5 Random sampling is used when probability estimates of required, other methods are needed (Section 4).
descriptive statistics and property distributional characteristics
6.3 Selection and Number of Bolts—The material of each
are desired as the basis for establishing allowable design
species selected for test shall be representative of the clear,
stresses for lumber and other stress-rated products. It is
straight-grained wood in the merchantable bole of the tree. A
applicable when data for a species do not exist or when existing
traditional method of selection is shown in Appendix X2. Note
estimates are believed no longer applicable because of a
that the sampling permits varying the intensity of sampling by
changing forest character. Random sampling provides better
tree (in accordance with Appendix X2) if the resulting data will
probability estimates than double sampling and is less expen-
support the anticipated analysis. X2.1 illustrates merchantable
sive and quicker if sampling and testing must be completed to
section and bolt labeling.
establish mechanical property-specific gravity regressions for
the double-sampling method. 6.4 Substitution of Flitches for Bolts:
D5536 − 17 (2023)
6.4.1 In cases where the logs or bolts are over 60 in. the 4 ft (1.22 m) sticks of one bolt shall be interchanged with
(1.52 m) in diameter, a single flitch 6 in. (15 cm) in thickness, the 4 ft (1.22 m) sticks of the next adjacent bolt from the same
taken through the pith representing the full diameter of the log, tree to form two composite bolts, each being complete and
may be substituted, in the same length, for the full log or bolt being made of equal portions of the adjacent 4 ft (1.22 m) bolts.
specified in 6.3. The sticks from one of these composite bolts shall be tested
6.4.2 Where orientation of test specimen to geographic green and those from the other shall be tested after drying.
Thus, the sticks of each composite bolt shall be regarded as if
features is considered critical, flitch shall maintain the coordi-
nates regarded as important in the specimen of 6.9. they were from the same bolt. X2.5 illustrates a method of
forming composite bolts.
6.5 Selection for Site Representation—Inferences in analysis
6.10.4 The traditional procedure provides for end-to-end
that relate to geographic distribution or site-specific features
matching (end matching) of sticks to be tested dry with those
must be anticipated in selecting both the sample numbers and
to be tested green, which is to be preferred when practicable. If,
sources. The number of trees shall conform to 6.2 and 6.3. If
because of the nature of the material, end matching is not
the analysis requires statistical inferences, random sampling
practicable, side matching may be used.
(Section 8) is one method.
6.6 Field Marking:
7. Cruciform Sampling – Secondary Method
6.6.1 Field marking procedures shall ensure identification of
7.1 The cruciform secondary method is intended for use in
trees, bolts, and shipment. Appendix X2 provides a traditional
evaluating the properties of wood only when relatively small
method.
trees, generally less than 12 in. (30 cm) in diameter when
6.6.2 If the orientation of test specimens to geographical or
measured approximately 4 ⁄2 ft (1.37 m), diameter breast
bolt features is critical, maintenance of cardinal point orienta-
height, are available to provide the test specimens and only
tion is recommended.
when such trees because of crook, cross grain, knots, or other
6.7 Field Descriptions:
defects are of such quality that the longer clear, straight-
6.7.1 Complete field notes describing the material shall be
grained specimens required by the primary method cannot
fully and carefully made by the collector. These notes shall be
reasonably be obtained. Whenever possible, the procedure for
sufficient to supply documentation similar to that in Table
the primary method shall be used regardless of the size of trees.
X1.1, with actual content chosen as appropriate for the
Since the procedure for the secondary method for many
objectives of the study.
features, such as in selection and care of material, is identical
6.7.2 Photographs of the standing trees selected should be
with the primary method, the secondary method presented
taken when practicable.
herewith are referenced to the primary method, and procedure
is given only where it differs therefrom. For convenience the
6.8 Preparation for Shipment—Maintenance of moisture
section numbers in the secondary method corresponds in the
content of the material and of all labeling documentation is a
last two digits with the numbering of the primary method.
requirement. Paragraph X2.3 provides traditional guidelines.
Thus, Section 7 for the secondary method corresponds in
6.9 Sawing and Marking of Bolts and Test Sticks—Sections
subject matter to Section 6.
of logs (consisting of two bolts) shall be marked and sawn into
7.1.1 Because of the cross-sectional size and the length of
1 1
2 ⁄2 in. by 2 ⁄2 in. (64 mm by 64 mm) sticks. Marking of bolts
specimen required for some of the tests (30 in. (76 cm) for
and sticks shall maintain continuity to the tree, and shipment.
static and impact bending) it is, however, sometimes difficult to
Consistency with 6.6 shall be maintained. X2.1 – X2.4
obtain test specimens in adequate number and entirely free of
document the traditional procedures.
defects from bolts representing smaller trees, particularly trees
6.10 Matching for Tests of Dry Material:
under 12 in. to 15 in. (30 cm to 38 cm) in diameter. With
6.10.1 If one purpose of sampling is to provide comparison increasing need for evaluating the properties of species involv-
of green and dry properties, provisions may be made for ing smaller trees, and the increasing importance of second-
matching of specimens within the tree. The traditional ap- growth timber that is expected to be harvested much before it
proach is as follows: reaches the sizes attained in virgin stands, there has developed
a need for secondary methods of test in which at least the
6.10.2 The collection of the material (Section 6) has been
arranged to provide for tests of both green and dry specimens longer test specimens are smaller than 2 in. by 2 in. (51 mm by
51 mm) in cross section.
that are closely matched by selection from adjacent parts of the
same tree. The 8 ft (2.44 m) long sections, after being marked
7.1.2 The exceedingly rapid rate of growth and correspond-
in accordance with 6.9, shall be sawn and marked in 2 ⁄2 in. by ing wide annual rings in much second-growth material, to-
2 ⁄2 in. by 8 ft (64 mm by 64 mm by 2.44 m) sticks. Each
gether with the desirability of incorporating more than a single
1 1
2 ⁄2 in. by 2 ⁄2 in. by 8 ft (64 mm by 64 mm by 2.44 m) stick year’s growth increment in a test specimen, has necessitated
shall then be cut into two 4 ft (1.22 m) pieces, making sure that
limiting the minimum cross section of test piece in these
each part carries the proper designation and bolt letter. secondary methods to 1 in. by 1 in. (25 mm by 25 mm). Data
1 1
6.10.3 Some of the 2 ⁄2 in. by 2 ⁄2 in. by 4 ft (64 mm by analysis based on these small specimens of rapid growth rate
64 mm by 1.22 m) sticks from each 8 ft (2.44 m) section are to wood is particularly vulnerable if the purpose of the sampling
provide specimens to be tested green (unseasoned) and the is to estimate total clearwood properties. See additional com-
remaining ones are to be dried and tested. To afford matching, ments in 6.1.2.
D5536 − 17 (2023)
7.2 Selection and Number of Trees—For each species to be matching of specimens within the tree. The following sections
tested, at least ten trees representative of the species shall be relate the traditional approach.
selected.
7.10.2 The collection of material has been arranged to
provide for tests of both green and dry specimens that are
7.3 Selection and Number of Bolts:
closely matched by selection from adjacent parts of the same
7.3.1 See 6.3, noting that, if using X2.1.1 as a guide, the
tree. The 8 ft (2.44 m) long sections, after being marked in
minimum number of trees is increased to ten. If information on
1 1
accordance with 7.9, shall be sawed into 2 ⁄2 in. by 2 ⁄2 in.
variation with height is desired, use of two trees is recom-
1 1
(64 mm by 64 mm) or 1 ⁄4 in. by 1 ⁄4 in. (32 mm by 32 mm) by
mended for that purpose in this secondary method.
7.3.2 From the trees not used for study of variation with 8 ft (2.44 m) sticks, and numbered and lettered in accordance
with 7.9. Each 8 ft (2.44 m) stick shall then be cut into two 4
height, take the 8 ft (2.44 m) section (c-d bolts) next above the
8 ft (2.44 m) butt log if this section falls within the merchant- ft (1.22 m) pieces, making sure that each part carries the proper
able length of the tree; otherwise, take the 8 ft (2.44 m) section designation and bolt letter. If the 8 ft (2.44 m) section is not
comprising the two highest standard bolts (multiples of 4 ft straight, it may be found more desirable to cut it into 4 ft (1.22
1 1
(1.22 m)) within the merchantable length. m) lengths before cutting the 2 ⁄2 in. or 1 ⁄4 in. (64 mm or 32
mm) square pieces. If this is done, care shall be taken to secure
7.4 Substitution of Flitches for Bolts—For the small trees to
end-matched sticks in the two 4 ft (1.22 m) bolts and to ensure
which this secondary method is applicable, bolts representing
that each part carries the proper designation and bolt letter.
the full diameter of the log are required, and flitches shall not
be substituted for bolts. 7.10.3 Composite bolts shall be formed in accordance with
the principles of 6.10.3 and 6.10.4. X2.7 may be used for
7.5 Selection for Important Species—For important species
guidance.
of wide geographical distribution, test material shall be se-
lected from two or more localities or sites. The number of trees
8. Random Sampling
of a species selected from each site or locality and within tree
sampling shall conform to the requirements of 7.2 and 7.3.
8.1 The general principles of probability sampling of mate-
rials (Practice E105), including setting sample size, collecting
7.6 Field Marking—See 6.6.
sample material in an objective way, and data analysis, apply to
7.7 Field Descriptions—See 6.7.
sampling the forest trees for determination of mechanical
7.8 Preparation for Shipment—See 6.8.
properties. Generally, sample size is dictated by the precision
desired in the property estimates. Sampling the forest trees for
7.9 Sawing and Marking of Bolts and Test Sticks—All bolts
1 1
determination of mechanical properties, however, presents
shall be marked on the top end into 2 ⁄2 in. (64 mm) or 1 ⁄4 in.
unique problems in maintaining objectivity in sampling be-
(32 mm) squares as shown in Fig. 1, and sawed into nominal
1 1
2 ⁄2 or 1 ⁄4 in. (64 or 32 mm) sticks. X2.6 may be used for cause the sample population, for practical purposes, is essen-
tially infinitely large, and because of problems associated with
guidance.
broad geographic ranges and inaccessible topography. The
7.10 Matching for Tests of Dry Material:
number of locations, their growth conditions, and the trees per
7.10.1 If one purpose of sampling is to provide comparison
location enter the picture also. For a given sample size, one
of green and dry properties, provisions may be made for
sample per tree probably provides the most precision.
However, if the cost of selecting a tree, and finding, cutting,
and bringing it out of the woods is high, then it may be more
economical to sample fewer trees but more intensively within
a tree or within a location, reflecting the need to increase the
total numbers of specimens tested to achieve the same preci-
sion. Thus, if it is desired to do a sampling experiment as
economically as possible, the sample size depends not only on
the precision of estimates desired but also on within- and
between-tree variation, within- and between-location variation,
and the cost of sampling versus the cost of testing individual
samples. The experimental design should seek the optimum
combination of sampling intensity at each stage of sa
...