Effect of age on variation in physical and mechanical properties of Acacia mangium planted in Thai Nguyen
TNU Journal of Science and Technology
226(01): 50 - 56
EFFECT OF AGE ON VARIATION IN PHYSICAL AND MECHANICAL
PROPERTIES OF Acacia mangium PLANTED IN THAI NGUYEN
Duong Van Doan1*, Nguyen Van Thai1, Khong Van Manh2
1TNU - University of Agriculture and Forestry
2Phu Luong Administration of Forestry
ARTICLE INFO
ABSTRACT
This study aimed to investigate the effect of age on some physical and
mechanical properties of Acacia mangium planted in Thai Nguyen
province such as air-dry density (AD), modulus of rupture (MOR),
and modulus of elasticity (MOE). The small specimens with
dimensions of 20 (radial) × 20 (tangential) × 320 (longitudinal) mm
were cut at breast height of 7-, 10-, 14-year-old sample trees. The
mean values of AD at 12% moisture content of 7-, 10-, 14-year-old A.
mangium were 0.48, 0.51, and 0.53 g/cm3, respectively. The mean
values of MOR of 7-, 10-, 14-year-old A. mangium were 64.38, 71.59,
and 73.46 MPa, respectively, while these values of MOE were 7.31,
8.77, and 9.10 GPa, respectively. AD had a significant positive linear
relationship with mechanical properties at all age levels. This suggests
that AD could be a useful parameter to predict static bending strength
of A. mangium wood. AD, MOR, and MOE exhibited a considerably
increasing trend from age 7 to age 10 before stabilizing to age 14.
This result will be an important reference for forest growers whether
to extent planting time of A. mangium after 10 years or not.
Received: 08/10/2020
Revised: 06/01/2021
Published: 14/01/2021
KEYWORDS
Wood science
Acacia mangium
Air-dry density
Tree age
MOE
MOR
ẢNH HƯỞNG CỦA TUỔI ĐẾN SỰ BIẾN ĐỔI CÁC TÍNH CHẤT VẬT LÝ VÀ CƠ
HỌC CỦA GỖ KEO TAI TƯỢNG (Acacia mangium) TRỒNG TẠI THÁI NGUYÊN
Dương Văn Đoàn1*, Nguyễn Văn Thái1, Khổng Văn Mạnh2
1Trường Đại học Nông Lâm – ĐH Thái Nguyên
2 Hạt Kiểm lâm huyện Phú Lương, tỉnh Thái Nguyên
THÔNG TIN BÀI BÁO
TÓM TẮT
Nghiên cứu này nhằm điều tra ảnh hưởng của tuổi đến một số tính
chất vật lý và cơ học của gỗ Keo tai tượng trồng tại Thái Nguyên
như: khối lượng thể tích (AD), độ bền uốn tĩnh (MOR), và mô đun
đàn hồi uốn tĩnh (MOE). Các mẫu gỗ có kích thước 20 (xuyên tâm)
× 20 (tiếp tuyến) × 320 (dọc thớ) mm được cắt từ vị trí ngang ngực
của các cây mẫu ở tuổi 7, 10, và 14. Kết quả nghiên cứu đã chỉ ra
rằng: giá trị trung bình AD ở độ ẩm 12% của Keo tai tượng tuổi 7,
10, và 14 lần lượt là 0,48 g/cm3, 0,51 g/cm3, và 0,53 g/cm3. Giá trị
trung bình MOR của gỗ Keo tai tượng tuổi 7, 10, và 14 lần lượt là
64,38 MPa, 71,59 MPa, và 73,46 MPa, trong khi đó giá trị MOE lần
lượt là 7,31 GPa, 8,77 GPa, và 9,10 GPa. AD có mối tương quan
dương rõ ràng với các tính chất cơ học ở tất cả các tuổi trong nghiên
cứu này. Điều này gợi ý rằng AD có thể là một thông số hữu ích để
dự đoán được các tính chất cơ học của gỗ Keo tai tượng trồng tại
Thái Nguyên. Cả AD, MOR, và MOE đã tăng lên đáng kể từ tuổi 7
đến tuổi 10 nhưng sau đó tăng chậm dần và có xu hướng không thay
đổi đến tuổi 14. Kết quả của nghiên cứu này là tài liệu tham khảo
quan trọng cho người trồng rừng Keo tai tượng khi quyết định có nên
kéo dài thời gian trồng sau 10 năm hay không.
Ngày nhận bài: 08/10/2020
Ngày hoàn thiện: 06/01/2021
Ngày đăng: 14/01/2021
TỪ KHÓA
Khoa học gỗ
Keo tai tượng
Khối lượng thể tích
Tuổi cây
MOE
MOR
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TNU Journal of Science and Technology
226(01): 50 - 56
1. Introduction
Acacia mangium Willd. is one of the important tree species planted popularly in Vietnam
because of its wide applicability with a variety of forest sites, straight stem, and faster growth
than Acacia auriculiformis and Uro Eucalyptus [1]. According to the documentary No.
30/2018/TT-BNNPTNT of the Ministry of Agriculture and Rural Development issued on
November 16, 2018 about the list of major forestry plant species, A. mangium is classified into
the list of the main species for planting forest in Vietnam [2]. Currently, A. mangium wood is
mainly used as raw materials for pulp production, particle board, MDF board, and peeled veneers
[3]. A. mangium is a fast-growing species that produces low wood quality because of the present
of juvenile wood, which can cause serious problems [4].
Age of tree is one of the important factors affecting to variation in wood properties. The trend
of variation depends on some factors such as species, growth conditions, and age of tree. There
were some studies regarding to evaluate the effect of age on variation in wood properties of A.
mangium. Makino et al. [4] evaluated the wood properties of 5- and 7-year-old A. mangium
planted in West Java, Indonesia. The mean basic density and compression strength for 5-year-old
trees were 0.42 g/cm3 and 30.0 MPa, and for 7-year-old trees were 0.45 g/cm3 and 32.8 MPa,
respectively. Chowdhury et al. [5] studied the effects of age (10-, 15-, and 20-year-old) on
physical properties of A. mangium trees grown in Bangladesh. The authors reported that the mean
basic density of A. mangium among different age groups was 0.52-0.60 g/cm3, the maximum
being observed in wood from 20-y-old trees and the minimum in wood from 10-year-old trees. In
Vietnam, the researches reporting effect of age on variation in physical and mechanical properties
of A. mangium wood is limited. Trinh [3] reported effect of harvested age on some physical and
mechanical properties of peeled veneer of A. mangium. This study showed that the basic density
of the peeled veneers increased with the age of the trees. The mean basic density and modulus of
elasticity of A. mangium peeled veneers at the age of 6, 9, 14 were 0.39, 0.43, and 0.51 g/cm3 for
basic density, respectively and 8.66, 10.87, and 10.93 GPa for modulus of elasticity, respectively.
Information on wood structure and properties, and the influence of tree age on these, is
required for better utilisation. In this study, we assessed the effects of tree age on some physical
and mechanical properties of A. mangium trees planted in Thai Nguyen, Vietnam. The results of
this study provide information to forest growers for selecting approximate time to harvest A.
mangium wood.
2. Materials and Methods
2.1. Materials
A total of fifteen trees of 7-, 10-, and 14-year-old A. mangium planted in Phu Luong, Thai
Nguyen, Vietnam was collected in this study (5 trees/age level). The latitude and longitude of 7-,
10-, and 14-y-old planted forests are N02408224 and E00417280, N02402724 and E00414187,
N02402646 and E00414070, respectively. The sample trees were selected basing on straight
trunks, normal branching, and no signs of any diseases or pest symptoms. Diameter at breast
height (1.3 m above the ground) as well as the total stem height for each tree was measured. The
detail information of each tree is given in Table 1. The north and south sides of each tree were
marked before felling.
Method of cutting specimens for experiments is presented in Figure 1. From each tree, 50-cm-
long logs were cut from 1.05 to 1.55 m height from above the ground and air-dried in two
months. From each log, small specimens (20 20 320 mm, Radial Tangential
Longitudinal) were cut at three distances from pith (10, 50, and 90 % of the radial length from
pith) on four sides (north, south, east, west) for measuring air-dry density (AD), modulus of
rupture (MOR), and modulus of elasticity (MOE) as described in Figure 1. For 7-year-old trees,
in each radial direction, small specimens were only cut at two positions: near the pith and near
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TNU Journal of Science and Technology
226(01): 50 - 56
the bark corresponding to 10 and 90% radial positions because of small diameter. The specimens
were conditioned in a room at a constant temperature (20°C) and relative humidity (60%) to
constant weight.
Table 1. Diameter and height of sample trees
Trees
D1.3 (cm)
Hvn (m)
Age 7
1
2
3
4
5
14.0
15.6
16.6
17.2
15.9
14.0
16.0
15.0
17.5
17.0
Age 10
Age 14
6
7
8
9
10
23.1
24.6
25.3
23.9
22.7
17.5
16.8
16.2
18.6
19.8
11
12
13
14
15
18.8
24.2
27.4
24.5
23.6
16.2
16.5
17.0
21.0
20.4
Note: D 1.3 - diameter at breast height (at 1.3 m above the ground), H vn - tree height
Figure 1. Method of cutting specimens for experiment from each tree
2.2. Measuring wood properties
AD, MOR, and MOE were assessed in accordance with Vietnamese Industrial Standards
(TCVN) as described by Duong et al. [6]. AD was determined in according TCVN 8048-2:2009
(ISO 3131:1975), while MOR and MOE were measured in according to TCVN 8048-3:2009
(3133:1975) and TCVN 8048-4:2009 (ISO 3349:1975), respectively. Twenty samples were
randomly chosento test moisture content (MC) after measuring mechanical properties. The
average MC of the test specimens was 12 ± 0.18%.
2.2.Data analysis
The data in this study was analysed by using the R software (R Core Team) version 4.0.2 [7].
Tukey-Kramer HSD test was used for comparing wood properties among the age groups.
3. Results and Discussions
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TNU Journal of Science and Technology
226(01): 50 - 56
3.1.Variation in AD from the pith to bark
Table 2 presents the mean values of AD at 10, 50, and 90 % radial length from the pith to bark
in trees of Acacia mangium 7-, 10-, and 14-year-old planted in Thai Nguyen. Results of ANOVA
analysis are also presented in Table 2 to exam that there are significant differences in AD among
radial positions or not.
The mean AD for 7-, 10-, and 14-y-old trees varied from 0.45 to 0.51 g/cm3, 0.47 to 0.54
g/cm3, and 0.48 to 0.56 g/cm3, respectively (at MC 12%). The findings of the present study are in
agreement to those in literature. Phi [1] reported an AD of 0.43 – 0.56 g/cm3 of A. mangium
grown in Binh Duong, Vietnam. In addition, Chowhury et al. [5] reported the mean AD of 10-
year-old A. mangium planted in Bangladesh was 0.52 g/cm3 that is similar with AD observed for
trees of age 10 in this study.
Table 2. Mean of air-dry density (g/cm3) and results of statistical analysis among radial positions in
different ages
Radial position (%)
Age
p-value
10
50
90
7
10
14
0.45b ± 0.04
0.47b ± 0.05
0.48b ± 0.05
0.51a ± 0.02
0.54a ± 0.03
0.56a ± 0.03
***
***
***
0.53a ± 0.03
0.55a ± 0.03
Note: a,b,c Mean with different superscript within a row significant difference; ***: p < 0.001
The result of ANOVA analysis showed that AD for 7-y-old A. mangium wood was the lowest
near the pith and the highest near the bark. In 10- and 14-y-old trees, the radial variation pattern
for AD was similar. AD increased rapidly from the pith to position of 50% radial length before
becoming constant towards the bark (Table 2). The radial pattern of variation from pith to
periphery of AD has been reported for A. mangium wood. Makino et al. [4] reported the radial
variation for basic density of 5- and 7-y-old A. mangium trees planted in Indonesia. Basic density
gradually increased to about 6 cm from the pith before stabilizing. Kim et al. [8] reported a
similar pattern of AD for Acacia hybris planted in northern Vietnam. On other hand, Wahyudi et
al. [9] reported a nearly constant basic density of Azadirachta excelsa from pith to bark. Based on
the present results and previous reports, radial variation of AD depends on species.
3.2. Radial variations in mechanical properties
Table 3 presents the mean mechanical properties at 10, 50, and 90% radial length from the
pith of 7-, 10-, and 14-year-old A. mangium trees planted in Thai Nguyen. The mean MOR for 7-
year-old trees at 10 and 90% radial length was 56.73 and 73.05 MPa. The mean MOR for 10- and
14-year-old trees varied from 61.94 to 76.16 MPa and from 65.13 to 77.99 MPa, respectively.
Obtained results in the present study were similar to those in previous studies. Shari et al. [10]
investigated the static bending strength of 6-y-old A. mangium trees planted in different sites.
This study reported that the overall MORs of A. mangium planted in Indonesia, Malaysia, and
Thailand were 75.02, 68.15, and 80.54 MPa, respectively.
The mean MOE for 7-, 10-, and 14-year-old varied from 6.56 to 8.17 GPa, 7.45 to 9.55 GPa,
and 7.75 to 10.14 GPa, respectively. Shari et al. [10] also reported that the mean MOE of 6-y-old
A. mangium trees planted in Indonesia, Malaysia, and Thailand were 6.73, 6.29, and 6.17 GPa,
respectively.
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TNU Journal of Science and Technology
226(01): 50 - 56
Table 3. Mean of mechanical properties and results of statistical analysis among radial positions in
different ages
Radial position from pith (%)
Mechanical properties Age
p-value
10
50
90
7
56.73b ± 11.14
61.94b ± 14.67
65.13b ± 15.62
6.56b ± 0.71
7.45b ± 1.26
7.75b ± 1.10
73.05a ± 6.47
76.16a ± 10.00
77.99a ± 9.98
8.17a ± 0.94
9.55a ± 0.65
10.14a ± 0.88
***
**
**
***
***
***
MOR (MPa)
10
14
7
10
14
76.39a ± 11.96
77.75a ± 13.30
MOE
(GPa)
9.29a ± 1.07
9.55a ± 1.07
Note: Note: a,b,c Mean with different superscript within a row significant difference;
**: p < 0.01; ***: p < 0.001
The radial variation patterns for MOR and MOE were similar to those for AD (Table 3). In
age of 7, the result of statistical analysis showed that there was a significant difference in MOR
between two positions (near the pith and near the bark). In 10- and 14-y-old trees, MOR and
MOE increased considerably to the middle position before remaining constant value forward to
outside (Table 3). Fujimoto et al. [11] reported that the compression strength increased from the
pith to 5 cm, after which it was almost constant in 30-y-old A. mangium. This pattern is also seen
in other hardwood species. Machado et al. [12] investigated the radial variation in MOR and
MOE of Acacia melanoxylon wood. Authors showed that MOR and MOE increased rapidly from
pith to 50% radial position before stabilizing. This trend may be contributable to the thicker walls
of fibers in the mature wood than those in the juvenile wood.
3.3.Effect of age on variation in AD, MOR, and MOE
The mean AD for 7-, 10-, and 14-y-old A. mangium trees was 0.48, 0.51, and 0.53 g/cm3,
respectively (Table 4). The AD increased with increasing tree age. The average AD of 14-year-
old trees increased about 4% compared to that of 10-year-old trees and about 10% compared 7-
year-old trees. However, the analysis of variance indicated that, there is only significant
difference between AD of age 7 and AD of age 10 and 14, while no significant difference was
found between AD of age 10 and AD of age 14.
Table 4. Physical and mechanical properties in different ages, ANOVA, and Tukey test results
Age
10
Wood
p-value
properties
AD (g/cm3)
MOR (MPa)
MOE (GPa)
7
14
0.48b ± 0.04
64.38b ± 10.55
7.31b ± 1.15
0.51a ± 0.05
71.59a ± 13.92
8.77a ± 1.38
0.53a ± 0.05
73.46a ± 14.44
9.10a ± 1.43
***
**
***
Note: a,b,cMean with different superscript within a row significant difference;
**: p < 0.01; ***: p < 0.001
The mean MOR for 7-, 10-, and 14-y-old A. mangium trees was 64.38, 71.59, and 73.46 MPa,
respectively. The mean MOE for 7-, 10-, and 14-y-old A. mangium trees was 7.31, 8.77, and 9.10
GPa, respectively (Table 4). The analysis of variance also indicated that there was no significant
difference in MOR and MOE between age 10 and age 14, while tree age did have a significant
effect to MOR and MOE from 7 to 10 years. The results in this study will be an important
reference for forest growers whether to extent planting time of A. mangium after 10 years or not.
3.4. The relationship between AD and mechanical properties
Coefficients of correlations (r) for relationship between AD and mechanical properties of A.
mangium planted in Thai Nguyen are summarized in Table 5. AD had significant (p < 0.001)
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TNU Journal of Science and Technology
226(01): 50 - 56
positive linear correlations with MOR in all age levels. Correlation coefficient between AD and
MOR is 0.72 when combined ages (Figure 2). AD had also significant positive linear
relationships at the 0.001 confidence level with MOE in all age levels (Table 5). For combined
ages, the value of correlation coefficient between AD and MOE is 0.78 (Figure 3). The above
results suggest that AD can be considered to be a powerful indicator for predicting the static
bending strength of A. mangium planted in Thai Nguyen. Prediction models of mechanical
properties (MOR, MOE) for A. mangium clear wood in different ages and combined ages are
presented in Table 5.
Table 5. Prediction models of static properties (MOR, MOE) for Acacia mangium wood
Modelling
Age
7
10
14
Equation
r
p-value
***
***
***
***
***
***
***
***
MOR = 210.89 × AD – 36.05
MOR = 243.99 × AD – 53.74
MOR = 156.61 × AD – 9.54
MOR = 193.44 × AD – 28.28
MOE = 21.20 × AD – 2.78
MOE = 21.95 × AD – 2.50
MOE = 20.13 × AD – 1.57
MOE = 23.05 × AD – 3.22
0.79
0.82
0.65
0.72
0.73
0.75
0.72
0.78
MOR (MPa)
(~AD)
Combined ages
7
10
14
MOE (GPa)
(~AD)
Combined ages
Note: ***: p < 0.001
Figure 2. Relationship between air-dry density (AD)
Figure 3. Relationship between air-dry density (AD)
and modulus of rupture (MOR) for combined ages
and modulus of elasticity (MOE) for combined ages
Wood density is an important indicator of the static bending strength properties of wood. The
present results are comparable with those reported by Makino et al. [4] who found the positive
correlation of basic density with mechanical properties of A. mangium planted in Indonesia. In
other hardwood species, Duong and Matsumura [13] found strong positive correlations of AD
with MOR (r = 0.84) and MOE (r = 0.72) at MC about 12% in Melia azedarach planted in Son
La, Vietnam. Positive linear relationships between AD and mechanical properties were also
reports by Machado et al. [12] for Acacia melanoxylon wood.
4. Conclusions
a. Tree age had significantly affected on physical and mechanical properties investigated in this
study. AD, MOR, and MOE increased rapidly from age 7 to age 10 before stabilizing to age 14.
b. In radial direction, AD, MOR, and MOE were lower near the pith and higher near the bark
in all age levels. In 10- and 14-year-old, wood properties determined in this study increased
considerably from pith to the middle position before remaining constant value forward to outside.
c. AD had a significant positive linear relationship with mechanical properties (MOR, MOE).
Therefore, AD can be considered to be a powerful indicator for predicting the static bending
strength of A. mangium planted in Thai Nguyen.
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TNU Journal of Science and Technology
226(01): 50 - 56
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