Revista Científica Ciencia y Método | Vol.03 | Núm.03 | Jul – Sep | 2025 | www.revistacym.com pág. 364
Physical and mechanical properties of Ochroma
pyramidale (Cav. ex Lam.) Urb. (balsa) wood growing
in three Ecuadorian locations
Propiedades físicas y mecánicas de la madera de Ochroma pyramidale (Cav. ex
Lam.) Urb. (balsa) creciendo en tres localidades ecuatorianas
Crespo-Gutiérrez, Rommel Santiago
1
Jiménez-Romero, Edwin Miguel
2
https://orcid.org/0000-0002-4013-6362
https://orcid.org/0000-0002-7411-8189
rcrespo@uteq.edu.ec
ejimenez@uteq.edu.ec
Universidad Técnica Estatal de Quevedo, Ecuador,
Quevedo.
Universidad Técnica Estatal de Quevedo, Ecuador,
Quevedo.
Anchundia-García, Jefferson Javier
3
Jara-Minaya, Jorge Manuel
4
https://orcid.org/0009-0007-1935-5775
https://orcid.org/0000-0003-3027-9631
j_anchundia22@hotmail.com
cebasgeor@gmail.com
Universidad Técnica Estatal de Quevedo, Ecuador,
Quevedo.
Universidad Técnica Estatal de Quevedo, Ecuador,
Quevedo.
Mora-Silva, Washington Fernando
5
https://orcid.org/0009-0003-7530-3567
washington.mora@gurit.com
Investigador Independiente, Ecuador
Autor de correspondencia
1
DOI / URL: https://doi.org/10.55813/gaea/rcym/v3/n3/81
Resumen: Ecuador actualmente es el primer productor de
madera de Ochroma pyramidale en el mundo,
incrementando el número de plantaciones e industrias
procesadoras de madera. En este estudio, el objetivo fue
evaluar las propiedades físicas y mecánicas de la madera
de O. pyramidale creciendo en el centro del Litoral y norte
de la Amazonia del Ecuador. Para ello, se consideraron
edades y ubicación de las muestras al interior del segmento
del árbol (basal, central y apical). Se consideraron las
directrices de la norma ASTM D143 para la preparación y
dimensionamiento de las probetas, así como para la
ejecución de los ensayos. Se empleó un ADEVA sobre un
Diseño completamente al Azar, y la prueba de Tukey para
la determinación de diferencias significativas. De acuerdo
con los resultados obtenidos, y tomando en consideración
los usos que se le da a la madera de O. pyramidale las
maderas de tres años de las provincias de Sucumbíos y
Orellana presentan mejores propiedades tecnológicas que
las de tres y cuatro años de Los Ríos, lo que sugiere que la
madera de la zona oriental puede ser aprovechada antes
que la madera de la zona costera, sin afectar las
propiedades tecnológicas de la madera de O. pyramidale.
Palabras clave: propiedades de la madera; balsa, calidad
de la madera, industria maderera.
Artículo Científico
Received: 05/Sep/2025
Accepted: 09Sep/2025
Published: 17/Sep/2025
Cita: Crespo-Gutiérrez, R. S., Jiménez-
Romero, E. M., Anchundia-García, J. J., Jara-
Minaya, J. M., & Mora-Silva, W. F. (2025).
Propiedades físicas y mecánicas de la madera
de Ochroma pyramidale (Cav. ex Lam.) Urb.
(balsa) creciendo en tres localidades
ecuatorianas. Revista Científica Ciencia Y
Método, 3(3), 364-
384. https://doi.org/10.55813/gaea/rcym/v3/n3
/81
Revista Científica Ciencia y Método (RCyM)
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© 2025. Este artículo es un documento de
acceso abierto distribuido bajo los términos y
condiciones de la Licencia Creative
Commons, Atribución-NoComercial 4.0
Internacional.
Revista Científica Ciencia y Método | Vol.03 | Núm.03 | Jul – Sep | 2025 | www.revistacym.com pág. 365
Julio – Septiembre 2025
Abstract: Ecuador is currently the first Ochroma pyramidale wood producer in the
world, increasing the number of plantations and wood processing industries. In this
study, the objective was to evaluate the physical and mechanical properties of O.
pyramidale wood growing in the center of the coast and north of the Ecuadorian
Amazon. For this, the ages and location of the samples within the tree segment
(bottom, centre and apex) were considered. The guidelines of the ASTM D143
standard were considered for the preparation and sizing of the test pieces, as well as
for the execution of the tests. An ANOVA was used on a completely Random Design,
and Tukey's test to determine significant differences. According to the results obtained,
and taking into consideration the uses that are given to O. pyramidale wood the three-
year-old woods from Sucumbíos and Orellana provinces presents better technological
properties than the three and four-year-old woods from Los Ríos, which suggests that
wood in the eastern zone can be harvested earlier than wood in the coastal zone,
without affecting the technological properties of the O. pyramidale wood.
Keywords: wood properties; balsa; wood quality, wood industry.
1. Introduction
The O. pyramidale tree (balsa) grows mainly in the equatorial area between latitude 0º
and 5º North and South. This tree is endemic from Ecuador (where more than 90% of
the world consumption is produced), and in neighboring regions. It has also been
introduced successfully to other regions of the world (Bonet et al., 2009). O. pyramidale
is a forest and timber species that is in great demand on the international market. It is
cultivated naturally and by reforestation, especially in the sub-tropical jungle of
Ecuador, where it is one of the most widely used forest and timber resources; for this
reason, it is one of the important economic items in the Ecuadorian economy
(González et al., 2010).
The Ecuadorian region around Quevedo (a city midway between Guayaquil on the
coast and Quito in the mountains) provides ideal growing conditions for the tree. The
region has a damp but well-drained layer of moist topsoil of the jungles along Ecuador's
Guayas River and its tributaries (Fletcher, 1949). Most of the commercially used O.
pyramidale wood is harvested from plantations, particularly from Ecuador. O.
pyramidale, with its low density and relatively high mechanical properties, is frequently
used as the core in structural sandwich panels, in applications ranging from wind
turbine blades to racing yachts (Borrega et al., 2015).
The wood properties of a tree are a combination of its genetic make-up and the
environment where it is grown (Moore, 2011). According to Rozenberg and Cahalan
(1997) the individual wood properties differ in the extent to which they are under
environmental or genetic control. The density of wood varies greatly within any
species. Many factors affect wood density, including age, tree vitality, location on the
tree, geographic location within the range of species, site condition such as soil, water
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and slope, genetic resource, climate, stresses growth and species. Because many of
these factors act in combination, it is difficult to separate the effects independently
(Shmulsky and Jones, 2011).
The mechanical strengths of wood are closely related to its density, since density is
the amount of woody substance present per volume unit of wood, and this amount of
woody substance is what must resist stresses (Diaz-vaz and Cuevas, 1986). According
to Senalik and Farber (2021) wood is a natural material, and the tree is subject to many
constantly changing influences, such as humidity, soil conditions, and growing space,
so its properties vary considerably, even in clean materials. Diaz-vaz and Cuevas
(1986) affirm that the mechanical resistance values of the same species are variable.
Pérez (1983) indicates that the values of the variables obtained in the static bending
test vary from one tree to another, within the same species or class of wood and within
the same tree, depending on the area where the sample is taken.
Wood characteristics often vary greatly within the range of a species, so does growth
and adaptability. Often the wood of trees does not exhibit the same properties when
they grow in considerably different environments. Environmental and genetic control
of the wood can be simultaneously important when evaluating the properties of woods
from different geographic sources within a species (Zobel and van Buijtenen, 1989).
2. Materials and methods
2.1. Material provenance
In Los Ríos province, in the littoral region, two sectors were chosen, while in the
Amazon region one locality in Sucumbíos province and one locality in Orellana
province. The locations, the provinces where they are located, and the geographic
coordinates are presented in Table 1, as well as in Figure 1.
Table 1
Sampling locations, province where they are located and geographic coordinates.
Locality
Province
Geographic coordinates
X
Y
Quevedo
Los Ríos
671231
9877600
Lago Agrio
Sucumbíos
952622
9949204
Francisco de Orellana
Orellana
963748
10019714
Note: Authors (2025).
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Figure 1
Map of continental Ecuador.
Note: The figure shows a) Los Ríos, Sucumbíos and Orellana province’s location in Ecuadorian territory.
b) Quevedo canton location in the coastal province of Los Ríos. c) Location of the Amazonian cantons
of Lago Agrio in the province of Sucumbíos and Francisco de Orellana in the province of Orellana
(Authors, 2025).
From the total number of trees in the plantations, 6 trees were randomly selected per
location, which presented excellent phytosanitary characteristics, straight and
cylindrical stems, and were representative in terms of diameter and height. The
selected trees were felled with a chainsaw. Subsequently, 3 logs were obtained from
each tree of 2.50 m in length, corresponding to the lower, middle and upper part. From
each log, 2 sections of 1.25 m in length were obtained, with a total of 36 logs per
location. From each log, between 2 and 4 joists were obtained on average.
To obtain the specimens for the physical tests, of the 3 logs per tree (1 in the basal
part, 1 in the central part and 1 in the apical part), 2 joists per section were obtained,
giving a total of 36 joists per location and 144 joists in total for all the locations. For the
mechanical tests, 2 joists were selected randomly per tree corresponding to the basal,
central and apical part, giving a total of 12 joists per location and 48 in total for all the
locations.
For the elaboration of the specimens for the tests of the physical and mechanical
properties, guidelines established in the ASTM D143 (2009) standard were followed.
For the physical tests, for each locality, 180 samples were obtained, giving a total of
720 samples for all the localities. With respect to the mechanical tests of 1 random
section beam, the specimens for the static bending tests were obtained, while the
specimens for the parallel and perpendicular compression tests to the fiber and Janka
hardness were made from the second random section joist. 6 specimens were
manufactured for each test, giving a total of 24 specimens for each location, with a
total of 96 specimens for all the locations.
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The planks from which the tests specimens for mechanical test were obtained were
kiln dried after the test specimens’ preparations, because these planks had to wait a
time to obtain the test specimens.
2.2. Physical properties tested
The physical properties such as moisture content, green and anhydrous density, total
radial, total tangential, total longitudinal and total volumetric shrinkage, and the total
tangential/radial shrinkage ratio (T/R) of the wood were determined, following the
specifications established in the ASTM D143 (2009) standards.
2.3. Mechanical properties tested
The mechanical properties evaluated in the Tinus Olsen universal testing machine,
with their respective accessories, were fiber stress at the proportional limit (SPL),
modulus of rupture (MOR) and modulus of elasticity (MOE) in static bending; SPL,
MOR and MOE in parallel compression; SPL and MOR in compression perpendicular
to the fiber; the maximum Janka hardness load on the radial, tangential and transverse
face, in accordance with the provisions of ASTM D143 (2009). For each tested piece
the moisture content was determined, since after obtaining the beams intended for the
test pieces, they were subjected to kiln drying to an average moisture content between
6 and 8%, to prevent degradation by Xylophagous fungi, since they were not
immediately tested.
2.4. Statistical analysis
Descriptive statistics were performed for the variables evaluated in the physical and
mechanical properties. To determine the significant differences among treatments (Los
Ríos 3 and 4 years; Sucumbíos 3 years and Orellana 3 years) and location of logs
under three blocking criteria (bottom, center, apex), an analysis of variance (ANOVA)
for a completely randomized block design was performed at 95% probability. For the
separation of means by homogeneous groups, the Tukey test was applied at 0.05%
probability.
3. Results
3.1. Physical properties
3.1.1 Moisture content
The percent of moisture content in green and dry state to the O. pyramidale wood of 3
and 4 years from different regions of Ecuador, as well as in accordance with the wood
position in the tree, is detailed in table 2.
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Table 2
Green and dry moisture content of O. pyramidale wood from different age and regions
of Ecuador, and three different sections of the tree.
Physical
properties
Treatment (locations
and tree age in years)
Mean value
(%)
Block (height
in the tree)
Mean
value (%)
Green
moisture
content
Los Ríos
3
266.53 a*
Bottom
250.76 a*
4
244.05 ab
Orellana
3
225.28 b
Centre
232.93 ab
Sucumbíos
3
187.25 c
Apex
208.00 b
Dry moisture
content
Los Ríos
3
72.05 a*
Bottom
70.61 a*
4
70.20 ab
Orellana
3
68.41 b
Centre
68.92 ab
Sucumbíos
3
64.24 c
Apex
66.65 b
Note: * Values with different letters are statistically different at 95% probability (Authors, 2025).
According to table 2, with respect to the moisture content in the green and anhydrous
state, the highest value was obtained in the wood from Los Ríos of three years with
266.53% and 72.45%, respectively, while the lowest record was gotten in the
Sucumbíos wood with 187.77% and 64.27%, respectively. The percentage means
show significant differences between the four analyzed localities. Regarding to wood
moisture content at different heights in the tree, according to table 2, the highest values
of green and anhydrous wood moisture content were recorded in the basal part of the
tree, while the lowest values were obtained in the apical segment of the tree. Significant
differences were found for the wood moisture content determined between the three
segments of the tested tree.
3.1.2 Density
Table 3 summarizes the means values form green and dry density of O. pyramidale
wood from different ages and Ecuadorian regions, and from the wood obtained at
different heights of the trees.
Table 3
Green and dry density of O. pyramidale wood from different regions, with different
ages, and at different tree heights.
Physical
properties
Treatment (locations
and tree age in years)
Mean value
(g.cm
-3
)
Block (height
in the tree)
Mean
value
(g.cm
-3
)
Green
density
Los Ríos
3
0.34 a
Bottom
0.38 a*
4
0.35 a
Orellana
3
0.32 a
Centre
0.32 b
Sucumbíos
3
0.36 a*
Apex
0.32 b
Dry density
Los Ríos
3
0.09 b
Bottom
0.12 a*
4
0.11 ab
Orellana
3
0.12 a
Centre
0.11 a
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Sucumbíos
3
0.13 a*
Apex
0.11 a
Note: * Values with different letters are statistically different at 95% probability (Authors, 2025).
In accordance with what is reported in table 3, there were no significant differences for
the green density values between the three analyzed localities, presenting green
densities between 0.32 g.cm
-3
to 0.36 g.cm
-3
. While for the density in anhydrous state,
there were significant differences between the three analyzed localities, determining
the highest value in the Sucumbíos wood of three-years-old with 0.13 g.cm
-3
, whilst
the lowest value was obtained in the three-year-old wood from Los Ríos with 0.09 g.cm
-
3
. Moore (2011) indicates that there is a stronger relationship between wood density
and longitude, with sites in the East having higher density than those in the West.
Analyzing the density at different heights of the tree, in relation to the density in the
green state, there were significant differences between the three analyzed segments.
The highest value of green density was obtained in the basal segment with 0.38 g.cm
-
3
, while the lowest value was gotten in the central and apical segments with 0.32 g.cm
-
3
. Concerning to the density in anhydrous state, the means do not show significant
differences between the three analyzed segments, being practically the same value in
the three segments of the tree (Table 3).
3.1.3. Shrinkage
The total tangential, radial, longitudinal and volumetric shrinkage, and the
radial/tangential shrinkage ratio from O. pyramidale wood of different ages and regions
of Ecuador, besides to the wood position in the tree, is detailed in table 4.
Table 4
Tangential, radial, longitudinal and volumetric total shrinkage, and radial/tangential
shrinkage ratio from O. pyramidale wood of different ages and regions of Ecuador, and
three different sections of the tree.
Physical properties
Treatment
(locations and
tree age in years)
Mean
value
(%)
Block
(height in
the tree)
Mean
value
(%)
Total tangential shrinkage
Los Ríos
3
5.24 ab
Bottom
6.43 a*
4
5.61 a*
Orellana
3
4.47 b
Centre
4.79 b
Sucumbíos
3
4.64 b
Apex
3.76 c
Total radial shrinkage
Los Ríos
3
1.06 b
Bottom
1.41 a*
4
1.88 a*
Orellana
3
0.69 c
Centre
1.08 b
Sucumbíos
3
1.14 b
Apex
1.08 b
Total longitudinal shrinkage
Los Ríos
3
0.29 ab
Bottom
0.28 a*
4
0.33 a*
Orellana
3
0.21 b
Centre
0.25 a
Sucumbíos
3
0.24 ab
Apex
0.28 a
Total volumetric shrinkage
Los Ríos
3
6.59 b
Bottom
8.12 a*
4
7.82 a*
Orellana
3
5.37 c
Centre
6.12 b
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Sucumbíos
3
6.01 bc
Apex
5.11 c
Radial/Tangential shrinkage
ratio (T/R) (dimensionless
value)
Los Ríos
3
3.21 b
Bottom
8.38 a
4
6.88 ab
Orellana
3
14.57 a*
Centre
9.65 a*
Sucumbíos
3
6.49 b
Apex
5.33 a
Note: * Values with different letters are statistically different at 95% probability (Authors, 2025).
According to table 4, there were significant differences for the total shrinkage in the
tangential, radial and longitudinal directions, as well as for the total volumetric
shrinkage and the tangential/radial shrinkage ratio, for O. pyramidale wood from the
three locations. The highest total tangential, total radial, total longitudinal and total
volumetric shrinkages were determined in four-year-old wood from Los Ríos province,
with 5.61%, 1.88%, 0.33% and 7.82%, respectively, while the lowest values occurred
in three-year-old wood from the Orellana province, with 4.47%, 0.69%, 0.21% and
5.37%, respectively. The highest tangential/radial shrinkage ratio was determined in
three-year-old wood from the Orellana province, with 14.57, while the lowest value was
found in wood from the Los Ríos province of three-years-old, with 3.21.
Regarding to the shrinkage of O. pyramidale wood at different heights of the tree,
significant differences were detected for the total tangential, total radial and total
volumetric shrinkage, while for the total longitudinal shrinkage and the tangential/radial
shrinkage ratio, there were no significant differences. The highest value of total
tangential shrinkage was obtained in the basal part, with 6.43%, while the lowest value
was determined in the apical part, with 3.76%. The highest value of total radial
shrinkage was obtained in the basal part (1.41%) while the lowest value was calculated
in the central and apical part (1.08%). The highest value of 8.12% from total volumetric
shrinkage was detected in the basal part, while the lowest total volumetric shrinkage
of 5.11% was found in the apical part of the tree (Table 4).
3.2. Mechanical properties
3.2.1 Moisture content of tests specimens
According to Pérez (1983), since the moisture content of the wood is highly correlated
with its resistance, it is essential that the moisture of all the specimens is obtained at
the time of the test. Failure to determine this physical property makes the results of
any test worthless for comparative purposes (Pérez, 1983). As indicated, at the time
of mechanical tests on O. pyramidale wood from different locations, the moisture
content in each test specimen to be tested was determined, and average moisture
values were obtained, which are detailed in table 5.
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Table 5
Average values of moisture content (%) in O. pyramidale wood test specimens from
different locations and ages at the time of mechanical testing.
Mechanical properties
test specimens
Moisture content
Treatment (locations and tree age in
years)
Mean
value (%)
Static bending
Los Ríos
3
5.97
4
7.63
Orellana
3
6.42
Sucumbíos
3
6,38
Compression parallel to
fibers
Los Ríos
3
5.55
4
7.75
Orellana
3
6.13
Sucumbíos
3
6.42
Compression
perpendicular to fibers
Los Ríos
3
5.55
4
7.75
Orellana
3
6.13
Sucumbíos
3
6.40
Hardness
Los Ríos
3
5.55
4
7.75
Orellana
3
6.13
Sucumbíos
3
6.40
Note: Authors (2025).
It should be noted that, according to Pérez (1983), any slight variation in moisture
content, when it is less than the PSF (approximately 28%), establishes a large variation
in the resistance of the wood. Therefore, each time the mechanical properties of wood
species are delivered, they must be accompanied by the data of the wood moisture
status to which they were determined (Pérez, 1983). In general, the lowest moisture
content values of the test specimens used for the mechanical tests were obtained in
the three-year-old wood from Los Ríos, while the highest moisture content values were
determined in the four-year-old wood from Los Ríos (Table 5).
3.2.2. Static bending
The average values of the variables calculated in the static bending tests for O.
pyramidale wood of three Ecuadorian provinces and two ages, just as at different
height in the tree, are detailed in the table 6.
Table 6
Average values of variables obtained from static bending rehearsals in O. pyramidale
wood specimens from different locations, ages and heights of the tree.
Mechanical
property
Variables
Treatment
(locations and
tree age in
years)
Mean value
(kg.cm
-2
)
Block
(height
in the
tree)
Mean value
(kg.cm
-2
)
Static
bending
Fiber
stress at
Los Ríos
3
53.75 b
Bottom
60.58 b
4
50.12 b
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the
proportion
al limit
(SPL)
Orellana
3
104.68 a
Centre
84.46 ab
Sucumbíos
3
106.56 a*
Apex
91.30 a*
Modulus of
rupture
(MOR)
Los Ríos
3
141.36 a
Bottom
173.25 a*
4
126.33 a
Orellana
3
146.69 a
Centre
140.04 ab
Sucumbíos
3
163.96 a*
Apex
120.46 b
Modulus of
elasticity
(MOE)
Los Ríos
3
157560.20 a*
Bottom
122308.70 a*
4
89722.40 a
Orellana
3
107713.70 a
Centre
143606.00 a
Sucumbíos
3
115996.30 a
Apex
87329.80 a
Note: * Values with different letters are statistically different at 95% probability (Authors, 2025).
According to table 6, there were significant differences between localities for SPL only,
while MOR and MOE did not have differences. Considering the wood position in the
tree, there were significant differences in SPL and MOR, being higher the SPL in the
apex zone, whereas MOR was higher in the bottom zone. MOE did not show
differences across the tree height.
The SPL values of O. pyramidale wood from amazon provinces (Sucumbíos and
Orellana) of the same age were statically equals, as well as the SPL of wood whit
different ages from the coastal province (Los Ríos) did not show significant differences.
The SPL values from wood of amazon provinces were higher than those determined
from wood of the coastal province. This means that the wood from Amazonia support
much more load to reach the proportional limit, in other words it is more elastic than
wood from coast region.
3.2.3. Parallel and perpendicular compression to fibers
Mean values of the variables calculated in parallel and perpendicular compression to
fibers tests, for O. pyramidale wood of 3 provinces and 2 ages, at different heights of
the tree, are detailed in the table 7.
Table 7
Average values of variables obtained from parallel and perpendicular compression to
fibers tests in O. pyramidale wood specimens from different locations from Ecuador,
ages and heights of the tree.
Mechanical
property
Variables
Treatment
(locations and
tree age in years)
Mean
value
(kg.cm
-2
)
Block
(height
in the
tree)
Mean value
(kg.cm
-2
)
Parallel
compression
to fibers
Fiber stress
at the
proportional
limit (SPL)
Los Ríos
3
51.39 a
Bottom
72.07 a*
4
67.63 a
Orellana
3
62.97 a
Centre
67.08 a
Sucumbíos
3
76.54 a*
Apex
54.75 a
Los Ríos
3
72.81 b
Bottom
105.41 a*
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Modulus of
rupture
(MOR)
4
111.31 a*
Orellana
3
98.03 ab
Centre
90.15 a
Sucumbíos
3
110.55 a
Apex
98.96 a
Modulus of
elasticity
(MOE)
Los Ríos
3
18900.41 b
Bottom
33214.85 a*
4
34146.94 a
Orellana
3
33993.52 a
Centre
31496.76 a
Sucumbíos
3
38837.83 a
Apex
29697.42 a
Perpendicular
compression
to fibers
Fiber stress
at the
proportional
limit (SPL)
Los Ríos
3
8.70 b
Bottom
11.16 a*
4
7.02 b
Orellana
3
11.94 ab
Centre
9.68 a
Sucumbíos
3
17.43 a*
Apex
12.97 a
Modulus of
rupture
(MOR)
Los Ríos
3
13.96 b
Bottom
21.52 a
4
16.30 b
Orellana
3
19.38 b
Centre
17.67 a
Sucumbíos
3
33.92 a*
Apex
23.49 a
Note: * Values with different letters are statistically different at 95% probability (Authors, 2025).
In compliance with table 7, in the test of parallel compression to fibers, the SPL did not
show significant differences among localities and different heights of the tree, whereas
the MOR and MOE showed significant differences between localities, but not between
different heights of the tree. The MOE in parallel compression to fibers was higher in
the wood from Sucumbíos and Orellana, both of three-years-old, and in the four-year-
old wood from Los Rios, this means that this wood is more flexible. The MOE of the
three-year-old wood from Los Rios was the lowest, which means that this wood is more
rigid.
With respect to the perpendicular compression to fibers, the results shown in table 7
indicate that there were significant differences in SPL and MOR between localities, but
not in different tree heights. The three-year-old wood from Sucumbíos yielded the
highest SPL, while the four-year-old wood from Los Ríos registered the lowest.
Meanwhile, the three-year-old wood from Sucumbíos reported the highest MOR,
whereas the three-year-old wood from Los Ríos registered the lowest.
3.2.3. Hardness
The Janka hardness mean values in the radial, tangential and transverse directions for
O. pyramidale wood of three locations and two ages, as well as different heights of the
tree, are shown in table 8.
Table 8
Mean values of Janka hardness tests in the radial, tangential and transverse directions
of O. pyramidale wood specimens from different locations, ages and height of the tree.
Mechanical
properties
Treatment
(locations and tree
age in years)
Mean
value (kg)
Block
(height in
the tree)
Mean
value (kg)
Radial Janka hardness
Los Ríos
3
38.83 c
Bottom
50.67 b
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4
86.17 a
Orellana
3
46.89 bc
Centre
42.67 b
Sucumbíos
3
59.89 b
Apex
80.50 a*
Tangential Janka
hardness
Los Ríos
3
22.67 c
Bottom
49.42 a
4
89.00 a
Orellana
3
34.55 bc
Centre
35.17 b
Sucumbíos
3
40.11 b
Apex
55.17 a*
Transverse Janka
hardness
Los Ríos
3
37.33 c
Bottom
79.62 a*
4
97.83 a
Orellana
3
51.22 c
Centre
59.33 b
Sucumbíos
3
74.78 b
Apex
56.92 b
Note: * Values with different letters are statistically different at 95% probability (Authors, 2025).
In compliance with table 8, there were significant differences between the Janka
hardness determined in the radial, tangential and transverse directions of O.
pyramidale wood. The highest Janka hardness value in all direction was recorded in
the four-year-old wood from Los Ríos, with 86.17 kg, 89.00 kg and 97.83 kg for radial,
tangential and transverse directions, respectively, meanwhile for the three-year-old
wood from Los Ríos the values were lower in all directions.
With respect to the Janka hardness in O. pyramidale wood at different heights of the
tree, significant differences were obtained for the three evaluated directions, being the
highest value recorded for radial and tangential directions, with 80.50 kg and 55.17 kg,
respectively, both in the apex tree section. Nevertheless, in the transverse section,
the highest Janka hardness value was for the wood extracted from the bottom tree
zone with 79.62 kg (Table 8). Furthermore, in this study it can be assumed that the
hardness was related to specimen density as all the specimen results indicated a rise
in hardness as the density becomes greater.
4. Discussion
Borrega et al. (2015) reported that the density values for O. pyramidale wood typically
range between 0.10 to 0.25 g.cm
-3
, although these can vary between 0.06 to 0.38 g.cm
-
3
. Wiselius (1998) also states that the density of O. pyramidale wood can range
between 0.09 and 0.31 g.cm
-3
at a moisture content of 12%. These density values are
similar to those reported in table 3. In O. pyramidale wood, Eddowers (2005) reported
that the density in the air-dry state ranges from 0.12 to 0.24 g.cm
-3
, while Bootle (1983)
reported for O. pyramidale wood from Ecuador an air-dry density of 0.17 g.cm
-3
.
According to Eddowers (2005) and Kotlarewski et al. (2016) the most desirable
densities for commercial use, in the dry state, range from 0.12 to 0.18 g.cm
-3
.
The anhydrous density value reported for the wood in Sucumbíos province is similar
to that reported by CIRAD (2012) for O. pyramidale wood at 12% MC of 0.14 g.cm
-3
,
as well as that reported by Bhekti et al. (2017) of 0.14 g.cm-3 basic density. Ortiz
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(2018) also reported similar density values for this species in Ecuador, with 0.16 g.cm
-
3
for wood from humid zones and 0.20 to 0.15 g.cm
-3
for wood from dry zones. This
author reported that there was a significant variation in density from one area to
another, as well as between sites in the same area. According to Ortiz (2018), the
density of wood is a very susceptible property that can vary between individuals of the
same species found in different locations. For his part, Hocker (1984) indicates that
density can be affected both by the origin of the genetic material and by environmental
factors to which each individual is exposed during their growth.
Dry density at different tree heights in the present study did not show significant
differences. These results differ from those reported by Ortiz (2018) who indicated that
the density of O. pyramidale wood behaves in a quadratic manner at different heights
of the tree. High values of density are observed in the lower section of the tree, then it
decreases in the middle, and it tends to rise again in the upper section. Thus, the
density tends to increase along with the height. According to this researcher, this may
be due to the fact that the roots and the support of the stem are both at the bottom of
the tree, causing the density to be higher at that point. In the case of the highest part
of individuals, this characteristic tends to increase due to the need to support the full
weight of the branches and leaves that form the tree's crown.
The difference in green density of the O. pyramidale wood can be attributed to the
anatomical constitution of the wood. Borrega et al. (2015) stated that fibers are the
main contributor to the large density variations in O. pyramidale wood. The volumetric
fraction of the fibers decreases slightly with increasing density, but their solid fraction
increases at least fivefold, due to the smaller cell lumen and thicker cell walls. The
increase in cell wall thickness is prevalent due to the thicker S2 layer. Thus, the
increase in cell wall thickness of the fibers with increasing density is mainly due to the
presence of a thicker S2 layer, with only a small contribution from the middle sheet,
and the S1 and S3 layers. In low-density O. pyramidale wood, the S2 layer is as thick
as S1 and S3, and represents approximately 30% of the cell wall thickness. In high-
density O. pyramidale wood, the S2 layer is 7 to 9 times thicker than S1 and S3, and
represents approximately 73% of the cell wall thickness.
CIRAD (2012) reported that O. pyramidale wood presents a total tangential shrinkage
of 5.2%, which is similar to the O. pyramidale wood from Los Ríos determined in this
research. The same author informed a total radial shrinkage of 2.2%, higher than those
showed in table 4 for localities and heights of the tree. According to these shrinkages,
CIRAD (2012) classify the O. pyramidale wood as low shrinkage. CIRAD (2012)
reported a tangential/radial shrinkage ratio of 2.4 for O. pyramidale wood, much lower
those reported in table 4. CIRAD (2012) classifies O. pyramidale wood as moderately
stable, but according to the values in table 4, for this research O. pyramidale wood
may be classified as unstable. Wiselius (1998) states that shrinkage upon seasoning
of O. pyramidale wood is low to moderate.
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Yao (1969) as cited in Ruwanpathiranal et al. (1996) observed that tangential
shrinkage decreased with increasing height in the tree, while longitudinal shrinkage
increased. This affirmation is in accordance with the tangential and longitudinal
shrinkages values reported in table 4. These trends are in line with the patterns of
variation in wood density, confirming that shrinkage and density are related. In general,
shrinkage seems to be related to factors such as rate of growth, position in the tree,
and the presence of reaction wood, as well as to wood density (Ruwanpathiranal et al.
1996).
The MOR in static bending reported in this research is in accordance with the values
reported in the literature, whereas the MOE values in static bending are greater than
those reported in previous studies. For O. pyramidale wood with an air-dry density of
0.17 g.cm
-3
from Ecuador, Bootle (1983) reported a MOE of 38749 kg.cm
-2
and a MOR
of 193.70 kg.cm
-2
. In previous studies on O. pyramidale wood there have been reported
values of MOE of 38749 kg.cm
-2
and a MOR of 193.70 kg.cm
-2
in dry wood from
Salomon islands (Eddowes, 2005). CIRAD (2012) also reported a MOE of 52413
kg.cm
-2
and a MOR of 244.70 kg.cm
-2
for O. pyramidale wood to 12% of moisture
content, they classify to O. pyramidale wood according to these values as low
resistance and MOE. In O. pyramidale wood from Papua New Guinea, Wiselius (1998)
informed a MOE ranged between 11778 - 16774 kg.cm
-2
and a MOR ranged from
86.68 - 127.5 kg.cm
-2
. Senalik and Farber (2021) affirms that O. pyramidale wood from
America, in static bending tests, have a MOE of 34670 kg.cm
-2
and a MOR of 220.30
kg.cm
-2
. Tsoumis (1991) indicated a 26003 kg.cm
-2
of MOE and 193.70 kg.cm
-2
for
MOR, for O. pyramidale wood from tropical America.
On their behalf, Kotlarewski et al. (2016) reported in static bending tests for O.
pyramidale wood with an average of moisture content of 13% and a density ranged
among 0.08 ≤ 0.12 g.cm
-3
a MOE of 12461 kg.cm
-2
and a MOR of 99.93 kg.cm
-2
, while
for wood with density range from 0.12 ≤ 0.18 g.cm
-3
a MOE of 20772 kg.cm
-2
and a
MOR of 169.30 kg.cm
-2
. They also argued that there is a relationship between the MOE
and MOR value in static bending, specimens with a high MOE generated a high MOR
value too.
According to Bhekti et al. (2017) the mean values of MOE and MOR in static bending
for O. pyramidale wood is 46193.14 kg.cm
-2
and 233.50 kg.cm
-2
respectively. The
authors emphasize that a significant positive correlation occurs between the static
bending properties (MOE and MOR) and air-dry density, suggesting that air dry density
is a good indicator for predicting mechanical properties in O. pyramidale wood.
According to the results of this research, the MOR in parallel compression to fibers
was statistically the same and higher in wood from Sucumbíos of three years old (0.13
g.cm
-3
anhydrous density) and Los Ríos of four years old (0.11 g.cm
-3
anhydrous
density), consequently this wood support more load until fracture, whilst the lowest
value was determined in three years old wood from Los Ríos (0.09 g.cm
-3
anhydrous
density) wood, which resist less load until fracture. According to Bhekti et al. (2017)
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there is a significant positive correlation between air-dry density and MOR in parallel
compression to fibers. Kollmann and Côté (1968) states that MOR in parallel
compression to fibers is highly correlated with basic density. These statements may
explain the significant differences between MOR in parallel compression to fibers
obtained in this study.
Senalik and Farber (2021) affirms that O. pyramidale wood exhibits a MOR parallel to
fibers of 151.90 kg.cm
-2
. Eddowers (2005) reported a MOR parallel to fibers of 122.40
kg.cm
-2
for O. pyramidale wood from Salomon islands. Coincidentally, for Ecuadorian
O. pyramidale wood, with an air-dry density of 0.17 g.cm
-3
, Bootle (1983) reported a
MOR parallel to fibers of 122.40 kg.cm
-2
. For their part, Tsoumis (1991) informed a
MOR value parallel to fibers for O. pyramidale wood from tropical America of 91.77
kg.cm
-2
. Bhekti et al. (2017) reported a MOR in parallel compression to fibers of 106.91
kg.cm
-2
in O. pyramidale wood. In this research the MOR in parallel compression to
fibers was higher than MOR in perpendicular compression to fibers. Goodrich et al.
(2010) affirms that the compressive strength is greater when it is parallel to the fibers
than when it is perpendicular (radial direction). In a O. pyramidale wood study from
Papua New Guinea, Kotlarewski et al. (2016) informed for parallel compression to
fibers tests in wood with 13% of moisture content and densities of 0.12 ≤ 0.18, 0.18 ≤
0.22 and ˃ 0.22 g.cm
-3
, MOR values of 93.81, 150.90 and 158.1 kg.cm
-2
, respectively.
These results, in accordance with these authors, indicate that the compressive
resistance of a specimen is greater with higher densities.
The O. pyramidale wood elasticity depends on its density, where a decrease in the
wood porosity with corresponding increase in density, increases the Young’s modulus
(Shishkina et al. 2014). Borrega et al. (2015) also states that the axial compressive
Young’s modulus and strength in O. pyramidale wood vary linearly with density,
reaching values up to 61183.00 kg.cm
-2
for modulus and 407.90 kg.cm
-2
for strength
at the highest densities. According to Bhekti et al. (2017) the dynamic Young’s modulus
(DMOE) in O. pyramidale wood of slow-growth, medium growth and fast-growth from
east Java ranged from 27226.42 kg.cm
-2
to 55268.62 kg.cm
-2
. When considering
different height of the tree, these authors informed that there was not significant
difference in DMOE, which coincides with the results obtained in this research (table
7). However, Bhekti et al. (2017) recorded a significant difference at the 5% level in
DMOE among the trees in each category, suggesting that DMOE in O. pyramidale
wood varies among trees with the same growth rate, which may account the
differences between MOE of Sucumbíos and Los Ríos both of three-years-old (table
7).
Kotlarewski et al. (2016) in perpendicular compression to fibers tests in O. pyramidale
wood from Papua New Guinea with an average moisture content of 11% and with
densities of ˂ 0.08 g.cm
-3
, 0.08 ≤ 0.12 g.cm
-3
, and 0.12 ≤ 0.18 g.cm
-3
, reported a MOR
values of 4.08, 6.12 and 11.22 kg.cm
-2
, respectively. These results, according to these
researchers, demonstrated that an increase in density does increase the compressive
resistance perpendicular to the grain, and that the compressive ability is greater
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parallel to the grain. Likewise, Tsoumis (1991) informed to O. pyramidale wood from
tropical America a MOR perpendicular to fibers of 10.2 kg.cm
-2
.
Borrega et al. (2015) pointed out that fibers in the xylem were aligned axially along the
trunk of the tree. However, some fibers showed a change in orientation in the axial–
tangential plane, particularly where rays penetrated the wood structure. These
researchers affirm that the mean fiber misalignment in O. pyramidale wood of medium
density is 6.1º, and conclude, according to the affirmations of Vural and Ravichandran
(2003) as well as Da Silva and Kyriakides (2007), that from a mechanical point of view,
fiber misalignment is important because it leads to the development of shear stresses
during compression and to initiation of failure by kinking in high-density O. pyramidale
wood.
In O. pyramidale wood, failure in compression tends to occur in the axial–tangential
plane with the failure mode transitioning from plastic buckling of fibers to kink band
formation as the density increases. Kink band formation in high-density O. pyramidale
wood is facilitated by local misalignment of fibers due to the presence of rays, which
leads to the development of shear stresses during compression. In the transverse
direction, compressive modulus and strength vary to the cube and square of density,
respectively, due to bending of the fiber cell walls. Transverse compressive modulus
and strength values are about an order of magnitude lower than those in the axial
direction. The rays act as reinforcement when O. pyramidale is loaded in the radial
direction, with this effect being more pronounced in low-density O. pyramidale (Borrega
et al., 2015).
In general, according to table 8, the O. pyramidale wood has higher values of Janka
hardness value in transverse face. Cave (1968) consider that the S2 layer in the cell
wall of fibers is the most important layer in the cell wall with respect to axial mechanical
properties of wood, and particularly with respect to stiffness. According to Barnett and
Bonham (2004) and Donaldson (2008), this is due to the greater thickness of the S2
layer, but also to its lower MFA. Bootle (1983) informed for O. pyramidale wood from
Ecuador a Janka hardness value of 40.79 kg. Tsoumis (1991) also reported a value of
40.79 kg of Janka hardness for O. pyramidale wood from tropical America. On their
behalf, Eddowes (2005) in a study on dry O. pyramidale wood from Salomon islands,
determined a Janka hardness value of 43.0 kg.
In O. pyramidale wood from Papua New Guinea, with a moisture content of 14%,
Kotlarewski et al. (2016) reported averages Janka hardness for the tangential surface
for wood density of 0.08 ≤ 0.12 g.cm
-3
of 19.99 kg, for wood density of 0.12 ≤ 0.18
g.cm
-3
of 31.30 kg, and for wood density of 0.18 ≤ 0.22 g.cm
-3
of 59.65 kg. Similarly,
the results for the radial surface in order of the density class were 23.76 kg, 29.57 kg,
56.70 kg and in the transverse surface were 31.92 kg, 43.44 kg and 69.65 kg. These
authors affirm that the transverse surface is far superior to the tangential and radial
surface by almost doubling each value presented for each density class. In the present
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research, in all ages analyzed, may be concluded that the transverse Janka hardness
is higher that radial and tangential Janka hardness (Table 7).
Borrega et al. (2015) claim that cellulose microfibrils contain both amorphous and
highly ordered crystalline regions. The relative degree of crystallinity in O. pyramidale
cellulose is about 39%, regardless the density. Considering that the cellulose content
in O. pyramidale wood is between 40 and 45%, then cellulose crystallinity was about
80 - 90%, significantly higher than the 40 - 60% determined for other hardwoods.
Besides cellulose microfibrils in the S2 are highly aligned with the fiber axis, with a
mean micro fibril angle (MFA) in the vicinity of 1.4º, and the cellulose crystallites in the
microfibrils is about 3 nm in width and 20 - 30 nm in length. The degree of cellulose
crystallinity is between 80 and 90%, significantly higher than previously reported for
other woods. The low MFA, coupled with the high crystallinity, is expected to confer
excellent axial mechanical properties to O. pyramidale wood.
5. Conclusions
The physical properties that presented significant differences were the moisture
content in the green and anhydrous state, the anhydrous density, the total tangential
shrinkage, the total radial shrinkage, the total longitudinal shrinkage and the total
volumetric shrinkage, as well as the radial/tangential shrinkage ratio.
The highest green and anhydrous moisture contents were obtained in the three-year-
old wood from Los Ríos, while the lowest values were found in the three-year-old wood
from Sucumbíos. The three-year-old wood from Orellana and Sucumbíos presented
the highest anhydrous density values, while the three-year-old wood from Los Ríos
exhibited the lowest value. The highest values of total tangential, total radial, total
longitudinal and total volumetric shrinkage were for the four-year-old wood from Los
Ríos, while the lowest values were for the three-year-old wood from Orellana. The
highest value of the radial/tangential shrinkage ratio was detected in the three-year-
old wood from Orellana, while the lowest value was found in the three-year-old wood
from Los Ríos.
Regarding the position of the wood at different heights of the tree, there were significant
differences for the moisture content in the green and anhydrous state, the density in
the green state, as well as for the total tangential, radial and volumetric shrinkage. The
highest values for these variables were detected in the bottom zone of the tree, while
the lowest values were found in the apical zone of the tree.
The mechanical properties in which significant differences were detected were the fiber
stress at the proportional limit in static bending, the modulus of rupture and the
modulus of elasticity in compression parallel to the fiber, the fiber stress at the
proportional limit and the modulus of rupture in compression perpendicular to the
fibers, the Janka hardness on the radial, tangential and transverse faces.
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The greatest value for fiber stress in the proportional limit in static bending were
detected in the three-year-old wood from Sucumbíos and Orellana, while the lowest
values were found in the three and four-year-old wood from Los Ríos.
In parallel compression to fibers, the highest values of modulus of rupture were
detected in the four-year-old wood from Los Ríos and in the three-year-old wood from
Sucumbíos. The lowest value was obtained in the three-year-old wood from Los Ríos.
The highest modulus of elasticity was gotten in the three-year-old wood from
Sucumbíos, four-year-old from Los Ríos and three-year-old from Orellana, while the
lowest value was for the three-year-old wood from Los Ríos.
In perpendicular compression to fibers, the greatest fiber stress at the proportional limit
was for the three-year-old wood from Sucumbíos, while the lowest values were
obtained in the three and four-year-old wood from Los Ríos. The highest modulus of
rupture was obtained in the three-year-old wood from Sucumbíos, while the lowest
values were gotten in the three and four-year-old wood from Los Ríos, as well as in
the three-year-old wood from Orellana.
The highest load withstood in Janka hardness on the radial, tangential and transverse
faces was found in the four-year-old wood from Los Ríos, while the lowest supported
load was detected in the three-year-old wood from Los Ríos.
Considering the location of the wood in the tree, there were significant differences for
the fiber stress at the proportional limit and for the modulus of rupture in static bending,
as well as for the Janka hardness in the radial, tangential and transverse faces. In
static bending, the highest value of fiber stress at the proportional limit was detected
in the wood of the apical zone, while the highest value of the modulus of rupture was
found in the wood of the bottom zone. In Janka hardness, the highest load recorded
on the radial face was for the wood of the apex, while for the tangential face the highest
values were calculated in the bottom and apical zone, whereas for the transverse face
the highest values were detected in the wood from the bottom zone.
According to the results obtained, and taking into consideration the uses that are given
to the wood of O. pyramidale, the three-year-old wood from Sucumbíos and Orellana
provinces gives better technological properties than the three and four-year-old wood
from Los Ríos, which suggests that the wood of the eastern zone can be used in less
time than the one of the coastal zone, without this affecting the technological properties
of the O. pyramidale wood.
In general, taking into consideration the applications of O. pyramidale wood, the three-
year-old wood from Sucumbíos and Orellana provinces has better technological
properties than the three and four-year-old wood from Los Ríos. It can be concluded
that the wood from the eastern provinces of northern Ecuador can be harvested one
year earlier than the wood from the coastal zone, without this or the age difference
affecting the technological properties of the O. pyramidale wood.
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Acknowledgments
The authors thanks to Fondos Concursables para Investigación Científica y
Tecnológica (FOCICYT) from the Universidad Técnica Estatal de Quevedo
(UTEQ) and the Gurit-Balsaflex company for funding this research.
Disclaimers
The authors declare that they have no conflicts of interest.
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