ASTM D5536-94(1999)
(Practice)Standard Practice for Sampling Forest Trees for Determination of Clear Wood Properties
Standard Practice for Sampling Forest Trees for Determination of Clear Wood Properties
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 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D 5536 – 94 (Reapproved 1999)
Standard Practice for
Sampling Forest Trees for Determination of Clear Wood
Properties
This standard is issued under the fixed designation D 5536; 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 (e) 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 Methods D 143.
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 E 105 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 D 143 Methods of Testing Small Clear Specimens of Tim-
ber
1.1 This practice offers two alternative physical sampling
D 2555 Method for Establishing Clear-Wood Strength Val-
procedures: cruciform sampling and random sampling. The
ues
choice of procedure will depend upon the intended use for the
E 105 Practice for Probability Sampling of Materials
test results, the resources available for sampling and testing,
and the availability of existing data on the mechanical proper-
3. Significance and Use
ties and specific gravity of the species of interest.
3.1 This practice covers procedures of sampling for obtain-
1.2 A third procedure, double sampling, is included prima-
ing small clear wood specimens which, when tested in accor-
rily by reference. This procedure applies the results of cruci-
dance with Methods D 143 and, in conjunction with full-size
form or random samples through correlation to improve or
product tests, will provide mechanical properties for use in
update property values.
deriving design properties for lumbar, panels, poles, house
1.3 This standard does not purport to address all of the
logs, and other products.
safety concerns, if any, associated with its use. It is the
3.2 Data obtained by testing specimens sampled in accor-
responsibility of the user of this standard to establish appro-
dance with these methods also provide information on the
priate safety and health practices and determine the applica-
influence on mechanical properties of such factors as density,
bility of regulatory limitations prior to use.
locality of growth, position in cross section, height in the tree,
2. Referenced Documents and moisture content.
3.3 Cruciform sampling is of principal value when informa-
2.1 ASTM Standards:
tion is desired on the influence on mechanical properties of
height in the tree; of age or radial position in the tree; of rate
This practice is under the jurisdiction of ASTM Committee D-7 on Wood and of growth; the change from sapwood to heartwood; the
is the direct responsibility of Subcommittee D07.01 on Fundamental Test Methods
relationships between mechanical properties and factors such
and Properties.
as specific gravity; and making general comparisons between
Current edition approved May 15, 1994. Published July 1994.
Bendtsen, B. A.; Freese, Frank; Ethington, R. L., “A Forest Sampling Method
for Wood Strength,” Forest Products Journal, Vol 20, No. 11, 1970, pp. 38–47.
Pearson, R. G., and Williams, E. J., “A Review of Methods for Sampling of
Annual Book of ASTM Standards, Vol 04.10.
Timber,” Forest Products Journal, Vol 8, No. 9, 1958, pp. 263–268. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5536
species for purposes of rating or selecting species for specific specimens, and is large enough to represent a considerable
end-use products. Cruciform sampling does not provide unbi- proportion of the material.
ased estimates of mean values, percentile or other descriptive
5.1.2 The choice of specimen size may be influenced by the
statistics, or a means of associating statistical confidence with
objectives of sampling and by the rate of growth of the
estimates of descriptive statistics.
material. Radial property gradients are primarily influenced by
3.4 Double sampling is used when it is desired to improve
age, and large specimens that encompass several rings may
or update existing estimates of mechanical property values that mask the age influence. Height gradients must be evaluated by
are the basis for establishing allowable design stresses for specimens from the same annual ring because of age influence.
stress-graded lumber, plywood, poles and piling, and other Thus, small specimens are preferred for measuring both radial
wood products. The method involves predicting one property and height gradients. When the purpose of sampling is to
by carefully observing a well-correlated auxiliary property that estimate clear wood properties, large specimens that include a
is presumably easier or cheaper to measure. A sample estimate number of annual rings are preferred. Even with 2 by 2-in. (50
of the auxiliary property is obtained with a high degree of by 50-mm) specimens, fast rates of growth will result in few
precision by representatively sampling the population. A rings per specimen. Regardless of the purpose of sampling, the
smaller independent sample or a subsample of the large sample
analysis and reporting of data may require careful consider-
is used to establish a relationship between the auxiliary ation of the character of the specimen.
property and the property for which an estimate is desired. As
5.2 Selection of Number of Trees—For each species to be
applied to sampling a forest, double sampling has employed
tested, select the number and the character of the trees to
specific gravity to predict mechanical properties. The double-
accomplish the purpose of the sampling. For traditional me-
sampling method provides unbiased estimates of mean me-
chanical property data base development, a minimum of five
chanical property values and an approximation method for
trees have usually been selected that have been judged “rep-
estimating percentile values. Statistical confidence may be
resentative” of the trees harvested of the species. Note that if
associated with the estimates of the means but not the
unbiased estimates and statistical confidence statements are
percentile values.
required, other methods are needed (Section 3).
3.5 Random sampling is used when probability estimates of
5.3 Selection and Number of Bolts— The material of each
descriptive statistics and property distributional characteristics
species selected for test shall be representative of the clear,
are desired as the basis for establishing allowable design
straight-grained wood in the merchantable bole of the tree. A
stresses for lumber and other stress-rated products. It is
traditional method of selection is shown in Appendix X2. Note
applicable when data for a species do not exist or when existing
that the sampling permits varying the intensity of sampling by
estimates are believed no longer applicable because of a
tree (in accordance with A2) if the resulting data will support
changing forest character. Random sampling provides better
the anticipated analysis. X2.1 illustrates merchantable section
probability estimates than double sampling and is less expen-
and bolt labeling.
sive and quicker if sampling and testing must be completed to
5.4 Substitution of Flitches for Bolts:
establish mechanical property-specific gravity regressions for
5.4.1 In cases where the logs or bolts are over 60 in. (1.5 m)
the double-sampling method.
in diameter, a single flitch 6 in. (150 mm) in thickness, taken
through the pith representing the full diameter of the log, may
4. Authentic Identification
be substituted, in the same length, for the full log or bolt
specified in 5.3.
4.1 The material shall be from trees selected in the forest by
one qualified to identify the species and to select the trees. 5.4.2 Where orientation of test specimen to geographic
Where necessary, herbarium samples such as leaves, fruit, features is considered critical, flitch shall maintain the coordi-
twigs, and bark shall be obtained to ensure positive identifica- nates regarded as important in the specimen of 5.9.
tion. 5.5 Selection for Site Representation— Inferences in analy-
sis that relate to geographic distribution or site-specific features
5. Cruciform Sampling—Primary Method must be anticipated in selecting both the sample numbers and
sources. The number of trees shall conform to 5.2 and 5.3. If
5.1 The standard methods for preparing small clear speci-
the analysis requires statistical inferences, random sampling
mens of timber, primary method, provide for cutting the log
(Section 7) is one method.
sections (divided into and identified as bolts) systematically
1 1 5.6 Field Marking:
into sticks of nominal 2 ⁄2 by 2 ⁄2 in. (63 by 63 mm) in cross
5.6.1 Field marking procedures shall ensure identification of
section, that are later surfaced to provide the test specimens 2
trees, bolts, and shipment. Appendix X2 provides a traditional
by 2 in. (50 by 50 mm) in cross section, on which the system
method.
is based. These methods have served as a basis for the
5.6.2 If the orientation of test specimens to geographical or
evaluation of the various mechanical and related physical
bolt features is critical, maintenance of cardinal point orienta-
properties of the clear wood of different species of wood. These
tion is recommended.
methods have been extensively used, and a large amount of
data based on them have been obtained and published. 5.7 Field Descriptions:
5.1.1 The 2 by 2-in. (50 by 50-mm) test specimen has the 5.7.1 Complete field notes describing the material shall be
advantage that it embraces a number of growth rings, is less fully and carefully made by the collector. These notes shall be
influenced by earlywood and latewood differences than smaller sufficient to supply documentation similar to that in Table
D 5536
X1.1, with actual content chosen as appropriate for the therefrom. For convenience the section numbers in the second-
objectives of the study. ary method corresponds in the last two digits with the
5.7.2 Photographs of the standing trees selected should be numbering of the primary method. Thus Section 6 for the
taken when practicable. secondary method corresponds in subject matter to Section 5.
5.8 Preparation for Shipment—Maintenance of moisture
6.1.1 Because of the cross-sectional size and the length of
content of the material and of all labeling documentation is a specimen required for some of the tests (30 in. (760 mm) for
requirement. Paragraph X2.3 provides traditional guidelines.
static and impact bending) it is, however, sometimes difficult to
5.9 Sawing and Marking of Bolts and Test Sticks—Sections obtain test specimens in adequate number and entirely free of
of logs (consisting of two bolts) shall be marked and sawn into
defects from bolts representing smaller trees, particularly trees
1 1
2 ⁄2 by 2 ⁄2-in. (60 by 60-mm) sticks. Marking of bolts and under 12 to 15 in. (30 to 38 cm) in diameter. With increasing
sticks shall maintain continuity to the tree, and shipment.
need for evaluating the properties of species involving smaller
Consistency with 5.6 shall be maintained. Paragraphs A2.1 trees, and the increasing importance of second-growth timber
through A2.4 document the traditional procedures.
that is expected to be harvested much before it reaches the sizes
5.10 Matching for Tests of Dry Material: attained in virgin stands, there has developed a need for
5.10.1 If one purpose of sampling is to provide comparison
secondary methods of test in which at least the longer test
of green and dry properties, provisions may be made for
specimens are smaller than 2 by 2 in. (50 by 50 mm) in cross
matching of specimens within the tree. The traditional ap-
section.
proach is as follows:
6.1.2 The exceedingly rapid rate of growth and correspond-
5.10.2 The collection of the material (Section 5) has been
ing wide annual rings in much second-growth material, to-
arranged to provide for tests of both green and dry specimens
gether with the desirability of incorporating more than a single
that are closely matched by selection from adjacent parts of the
year’s growth increment in a test specimen, has necessitated
same tree. The 8-ft (2.4-m) long sections, after being marked in
limiting the minimum cross section of test piece in these
accordance with 5.9.1, shall be sawn and marked in 2 ⁄2 by
secondary methods to 1 by 1 in. (25 by 25 mm). Data analysis
1 1 1
2 ⁄2-in. (60 by 60-mm) by 8-ft sticks. Each 2 ⁄2 by 2 ⁄2-in. by
based on these small specimens of rapid growth rate wood is
8-ft stick shall then be cut into two 4-ft (1.2-m) pieces, making
particularly vulnerable if the purpose of the sampling is to
sure that each part carries the proper designation and bolt letter.
estimate total clearwood properties. See additional comments
1 1
5.10.3 Some of the 2 ⁄2 by 2 ⁄2-in. by 4-ft (60 by 60-mm by
in 5.1.2.
1.2-m) sticks from each 8-ft (2.4-m) section are to provide
6.2 Selection and Number of Trees— For each species to be
specimens to be tested green (unseasoned) and the remaining
tested, at least ten trees representative of the species shall be
ones are to be dried and tested. To afford matching, the 4-ft
selected.
sticks of one bolt shall be interchanged with the 4-ft sticks of
6.3 Selection and Number of Bolts:
the next adjacent bolt from the same tree to form two
6.3.1 See 5.3.1, noting that, if using A2.1.1 as a guide, the
composite bolts, each being complete and being made of equal
minimum number of trees is increased to 10. If information on
portions of the adjacent 4-ft bolts. The sticks from one of these
variation with height is desired, use of two trees is recom-
composite bolts shall be tested green and those from the other
mended for that purpose in this se
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