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

TNU Journal of Science and Technology 226(01): 50 - 56 
 50 Email: jst@tnu.edu.vn 
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 
Received: 08/10/2020 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. 
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 
Ngày nhận bài: 08/10/2020 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 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 
DOI: https://doi.org/10.34238/tnu-jst.3689 
* Corresponding author. Email: duongvandoan@tuaf.edu.vn 
TNU Journal of Science and Technology 226(01): 50 - 56 
 51 Email: jst@tnu.edu.vn 
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 
TNU Journal of Science and Technology 226(01): 50 - 56 
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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 14.0 14.0 
2 15.6 16.0 
3 16.6 15.0 
4 17.2 17.5 
5 15.9 17.0 
Age 10 
6 23.1 17.5 
7 24.6 16.8 
8 25.3 16.2 
9 23.9 18.6 
10 22.7 19.8 
Age 14 
11 18.8 16.2 
12 24.2 16.5 
13 27.4 17.0 
14 24.5 21.0 
15 23.6 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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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 
Age 
Radial position (%) 
p-value 
10 50 90 
7 0.45b ± 0.04 0.51a ± 0.02 *** 
10 0.47b ± 0.05 0.53a ± 0.03 0.54a ± 0.03 *** 
14 0.48b ± 0.05 0.55a ± 0.03 0.56a ± 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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Table 3. Mean of mechanical properties and results of statistical analysis among radial positions in 
different ages 
Mechanical properties Age 
Radial position from pith (%) 
p-value 
10 50 90 
MOR (MPa) 
7 56.73b ± 11.14 73.05a ± 6.47 *** 
10 61.94b ± 14.67 76.39a ± 11.96 76.16a ± 10.00 ** 
14 65.13b ± 15.62 77.75a ± 13.30 77.99a ± 9.98 ** 
MOE 
(GPa) 
7 6.56b ± 0.71 8.17a ± 0.94 *** 
10 7.45b ± 1.26 9.29a ± 1.07 9.55a ± 0.65 *** 
14 7.75b ± 1.10 9.55a ± 1.07 10.14a ± 0.88 *** 
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 
Wood 
properties 
Age 
p-value 
7 10 14 
AD (g/cm3) 0.48b ± 0.04 0.51a ± 0.05 0.53a ± 0.05 *** 
MOR (MPa) 64.38b ± 10.55 71.59a ± 13.92 73.46a ± 14.44 ** 
MOE (GPa) 7.31b ± 1.15 8.77a ± 1.38 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) 
TNU Journal of Science and Technology 226(01): 50 - 56 
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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 Equation r p-value 
MOR (MPa) 
(~AD) 
7 MOR = 210.89 × AD – 36.05 0.79 *** 
10 MOR = 243.99 × AD – 53.74 0.82 *** 
14 MOR = 156.61 × AD – 9.54 0.65 *** 
Combined ages MOR = 193.44 × AD – 28.28 0.72 *** 
MOE (GPa) 
(~AD) 
7 MOE = 21.20 × AD – 2.78 0.73 *** 
10 MOE = 21.95 × AD – 2.50 0.75 *** 
14 MOE = 20.13 × AD – 1.57 0.72 *** 
Combined ages MOE = 23.05 × AD – 3.22 0.78 *** 
Note: ***: p < 0.001 
Figure 2. Relationship between air-dry density (AD) 
and modulus of rupture (MOR) for combined ages 
Figure 3. Relationship between air-dry density (AD) 
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. 
TNU Journal of Science and Technology 226(01): 50 - 56 
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