Study on within-tree variation in wood properties of melia azedarach planted in Northern Vietnam

Study on Within-tree Variation in Wood Properties of

Melia azedarach Planted in Northern Vietnam

Duong Van Doan

2018

Study on Within-tree Variation in Wood Properties of Melia azedarach

Planted in Northern Vietnam

By

Duong Van Doan

Laboratory of Wood Science, Division of Sustainable Bioresources Science,

Department of Agro-environmental Sciences, Faculty of Agriculture, Graduate

School of Bioresource and Bioenvironmental Sciences, Kyushu University, Japan

Supervisor

Professor Junji Matsumura

Advisory Committee Members

Associate Professor Shinya Koga

Associate Professor Noboru Fujimoto

2018

i

Table of Contents

Table of Contents.................................................................................................................................i

Abbreviations......................................................................................................................................v

CHAPTER 1........................................................................................................................................1

Introduction.........................................................................................................................................1

CHAPTER 2........................................................................................................................................8

Literature Review ...............................................................................................................................8

2.1 Introduction.................................................................................................................................9

2.2 Within-tree variations in wood properties ..................................................................................9

2.2.1 Growth ring width................................................................................................................9

2.2.2 Wood density and specific gravity.....................................................................................11

2.2.3 Fiber length ........................................................................................................................14

2.2.4 Microfibril angle ................................................................................................................15

2.2.5 Shrinkage properties ..........................................................................................................17

2.2.6 Mechanical properties........................................................................................................18

2.3 Nondestructive wood evaluation...............................................................................................20

2.4 Conclusion of literature review.................................................................................................21

CHAPTER 3......................................................................................................................................22

Variation in Intrinsic Wood Properties..........................................................................................22

ii

3.1 Abstract.....................................................................................................................................23

3.2 Introduction...............................................................................................................................24

3.3 Materials and methods..............................................................................................................25

3.3.1 Study site and sampling .....................................................................................................25

3.3.2 Wood specimen preparation ..............................................................................................26

3.3.3 Growth ring width..............................................................................................................26

3.3.4 Wood specific gravity........................................................................................................29

3.3.5 Fiber length and microfibril angle .....................................................................................29

3.3.6 Determination of fiber length increment (FLI)..................................................................31

3.3.7 Statistical analysis..............................................................................................................31

3.4 Results and discussion ..............................................................................................................33

3.4.1 Growth ring width..............................................................................................................33

3.4.2 Wood specific gravity........................................................................................................37

3.4.3 Microfibril angle ................................................................................................................41

3.4.4 Fiber length ........................................................................................................................41

3.4.5 Stabilizing point of fiber length increment ........................................................................46

3.4.6 Implications for wood utilization of M. azedarach in northern Vietnam..........................46

3.5 Conclusions...............................................................................................................................48

CHAPTER 4......................................................................................................................................49

Transverse Shrinkage Variations within Tree Stems....................................................................49

4.1 Abstract.....................................................................................................................................50

4.2 Introduction...............................................................................................................................51

4.3 Material and methods................................................................................................................53

4.3.1 Sampling ............................................................................................................................53

iii

4.3.2 Dynamic modulus of elasticity of log (DMOElog).............................................................54

4.3.3 Basic density and transverse shrinkage..............................................................................56

4.3.4 Data analysis......................................................................................................................57

4.3.5 Grade yield.........................................................................................................................57

4.4 Results and discussion ..............................................................................................................60

4.4.1 Basic density and transverse shrinkage..............................................................................60

4.4.2 Relationships between transverse shrinkage and basic density .........................................68

4.4.3 Prediction of transverse shrinkage .....................................................................................71

4.4.4 Grade yield of shrinkage properties...................................................................................74

4.5 Conclusions...............................................................................................................................76

CHAPTER 5......................................................................................................................................77

Within-stem Variations in Mechanical Properties ........................................................................77

5.1 Abstract.....................................................................................................................................78

5.2 Introduction...............................................................................................................................79

5.3 Material and methods................................................................................................................80

5.3.1 Sampling ............................................................................................................................80

5.3.2 Wood density and dynamic modulus of elasticity (Ed)......................................................81

5.3.3 MOR and MOE..................................................................................................................82

5.3.4 Data analysis......................................................................................................................82

5.3.5 Grade yield.........................................................................................................................84

5.4 Results and discussion ..............................................................................................................84

5.4.1 Wood density and mechanical properties..........................................................................84

5.4.2 Correlation of wood density with mechanical properties..................................................90

5.4.3 Correlation between moduli of elasticity...........................................................................94

iv

5.4.4 Prediction of bending strength...........................................................................................96

5.4.5 Grade yield of mechanical properties................................................................................96

5.5 Conclusions.............................................................................................................................100

CHAPTER 6....................................................................................................................................102

General Discussion and Conclusions.............................................................................................102

6.1 General discussion ..................................................................................................................103

6.2 Conclusions.............................................................................................................................109

References........................................................................................................................................111

Acknowledgements .........................................................................................................................126

v

Abbreviations

• BD: Basic density (g/cm3

)

• DMOElog: Dynamic modulus of elasticity

of log (GPa)

• Ed: Dynamic modulus of elasticity of clear

specimen (GPa)

• FL: Fiber length (mm)

• FLI: Fiber length increment (%)

• GRW: Growth ring width (mm)

• MFA: Mircofibril angle (

o

)

• MOE: Modulus of elasticity (GPa)

• MOR: Modulus of rupture (MPa)

• SG: Specific gravity in air-dry condition

• VL: Acoustic wave velocity (m/s)

• WD: Wood density in air-dry condition

(g/cm3

)

• αR: Radial shrinkage (%)

• αT: Tangential shrinkage (%)

• αT/αR: Tangential/radial shrinkage ratio

• ρ: Green density of log (kg/m3

)

1

CHAPTER 1

Introduction

2

All forests fulfil a range of roles and provide a variety of goods and services. The roles fulfilled

by planted forests are diverse and the goods and services produced include the production of industrial

wood, fuel wood, non-wood forest goods (eg. animal fodder, apiculture, essential oils, tan bark, cork,

latex, and food) and conservation, carbon sequestration, recreation (eg. hunting, fishing, and hiking),

erosion control, and rehabilitation of degraded lands, including landscape and amenity enhancement.

For countries with a low forest cover, the only way to obtain the multiple benefits from forests, is

creating new forests, mainly through planting.

Global planted forest area increased from 1990 to 2015 from 167.5 million ha to 277.9 million

ha with the increase varying by region and climate domain (Payn et al. 2015). Together with global

trend, Vietnam’s planted forest area increased considerably from 1985 with 0.58 million ha to 2016

with 4.13 million ha (Table 1.1) (Ministry of Agriculture and Rural Development of Vietnam 2017).

Large areas of plantation do not only supply material for pulp and paper production but also play an

important role in the protection of environment by reducing greenhouse gas and helping to reduce

poverty in rural areas (Kim 2009). Besides, with the decrease in the available wood resources and the

increase in wood processing costs have led to a significant interest in timber production from

plantation. For timber plantation, the current wood is under-utilised and poorly managed. Therefore,

there is a need for effective and sustainable utilization of the plantation forests in order to prevent

further decline of timber sources and improve quality of timber products. One of the ways of

sustainably utilizing wood resources is to study on wood properties.

Wood is a highly variable material due to its biological origin (Zobel and Van Buijtenen 1989).

For a given species, the within-tree variation is further partitioned into variation from pith to bark

(radial variation) and variation with position along the stem (axial variation). The large variability of

3

wood characteristics makes it difficult to precisely predict its performance and therefore to efficiently

process and utilize the material. On the other hand, the variability means that this material has potential

for genetic improvement and diverse end uses (Zobel and Van Buijtenen 1989, Koga and Zang 2004).

Therefore, a better understanding of the wood variability within tree is of value to both wood quality

improvement and efficient wood processing and utilization.

4

Table 1.1 The area of natural and planted forest in Vietnam from 1985 to 2016

9.31

8.25

10.20 10.30 10.17 10.24

0.58

1.05

2.50 2.90

3.88 4.13

0

2

4

6

8

10

12

1985 1995 2005 2009 2015 2016

Area (million ha)

Year

Natural forest Planted forest

5

Melia azedarach L. is a deciduous tree belonging to the family of Meliaceae. It is native to the

Himalaya region of Asia (EL-Juhany 2011). The species is well adapted to warm climates, poor soils

and seasonally dry conditions (Harrison et al. 2003). The fully-grown tree has a rounded crown, and

commonly measures 7 to 12 m tall. However in exceptional circumstances, M. azedarach can attain a

height of 45 m. The leaves are up to 50 cm long, alternate, long-petioled, two or three times compound

(odd-pinnate); the leaflets are dark green above and lighter green below, with serrate margins. The

flowers are small and fragrant, with five pale purple or lilac petals, growing in clusters. The fruit is a

drupe, marble-sized, light yellow at maturity, hanging on the tree all winter, and gradually becoming

wrinkled and almost white (Rahman et al. 2014).

M. azedarach could contribute to the prevention of global warming due to their high ability to

stock carbon (Osei et al. 2018). Together with other fast growing species, M. azedarach trees are used

as pulping materials due to their high productivity (Ministry of Agriculture and Rural Development

of Vietnam 2014). Using wood of M. azedarach as a building material (eg. posts and beams in timber

construction) to increase their value is expected (Hasegawa et al. 2015). There are some researchers

investigated the physical and mechanical properties of the M. azedarach wood. Matsumura et al.

(2006) reported the variation in wood properties of M. azedarach planted in Japan and suggested the

possibility of using it as new timber materials. Venson et al. (2008) experimented with the physical,

mechanical, and biological properties of M. azedarach planted in Mexico. They demonstrated that M.

azedarach can be used as structural lumber if the appropriate genotypes and clones were collected. In

Vietnam, M. azedarach is planted popularly in most of the provinces in northern. Most of the M.

azedarach were planted in short rotation around 5-6 years with the purpose to supply raw material for

pulp and particleboard industries. Currently the decrease in the available wood resources and the

increase in wood processing costs have led to a significant interest in wood from plantation. Hence,

wood of M. azedarach has received recently considerable attention given its relatively fine grains,

6

quite durable, resistant to termites and insects, and easy to work (Nghia 2007). However, until now

no effort has been made to investigate the within-tree variations including radial and axial directions

in wood properties of M. azedarach planted in Vietnam, despite the importance of this species and the

multiuse of its wood.

Rapid and nondestructive evaluation of wood properties has great importance to tree breeders

as well as to several other considerations in optimal timber utilization. Nondestructive evaluation is

an important tool for the characterization of wood and can be used in industry to improve quality

control process through reducing the property variation of the raw material and its by-products

(Oliveira et al. 2005). However, the properties of wood vary considerably because it is a natural

material. The large variability of wood characteristics makes it difficult to precisely predict its

performance. This is one of the most important challenges to apply nondestructive testing method in

wood quality evaluation. A number of studies suggested that nondestructive technique may be used

to assess wood properties in small wood specimens, lumber and determine the quality of logs and

standing trees (Wang et al. 2001, Carter et al. 2005, Ishiguri et al. 2006, Ishiguri et al. 2008). One of

the most widespread and accurate nondestructive techniques used to study timber is based on stress

waves. These techniques are based on the observed relations between the propagation of a wave

through a piece (velocity and attenuation) with some of the properties of the material (mechanical and

physical properties), as well as some characteristics or singularities of the piece as decays, holes or

other irregularities (Ross and Pellerin 1994, Montero et al. 2015). Therefore, it is necessary to

investigate the usefulness of a stress wave technique for evaluation wood properties of M. azedarach

planted in northern Vietnam.