6 regression and segmented linear regression. In this study, determination of
demarcation point was based on fiber length and microfibril angle MFA by using segmented regression analysis. This model has been used by some
researcher and proved to be a practical and objective method to estimate transition ring between juvenile and mature wood Abdel-Gadir and Krahmer 1993; Sauter
et al
. 1999; Bustos et al. 2003; Darmawan et al. 2013; Rahayu et al. 2014 Sengon Falcataria moluccana and jabon Anthocephalus cadamba are a
fast growing wood species widely planted by community in Indonesia. They have short cutting cycle 5 to 7 years consequently there would be high percentage of
juvenile portions in the tree stems. According to Sumarna 1961 mean annual increment MAI for sengon wood in diameter fluctuates around 4
–5 cm until the age of 6 years. At the age of 8
–9 years, the diameter increment is still high, about 3
–4 cm; it then decreases slowly thereafter. Young A. cadamba trees up to 5 years old can grow 1.2
–11.6 cm per year in diameter. In general, growth rates are about 2 cmyear in diameter Sudarmo 1957; Suharlan et al. 1975. The
microstructure of sengon and jabon were presented on Figure 1a and 1b.
Figure 1 Microstructure of 5 years old sengon a and jabon b near bark with magnitude 300x
Figure 2 Microstructure of 18 years old poplar cultivar ‘I214’ a and 26 years
old douglas-fir b near bark with magnitude 300x France is the largest grower of poplar Populus sp in Europe. Average
annual poplar harvesting between 2009 and 2013 reached 2.4 million m
3
FCBA 2015. According to FAO 2011, plywood and veneer still account for the largest
share of poplar products with 59.9 of total production. Douglas-fir
a
a b
b
7 Pseudotsuga menziesii is known by its ability to produce high wood volume in
European countries Podrazsky et al. 2013. It was categorized as fast growing species Rowell et al. 2005 which is capable of rapid early growth rate resulting
in a large portion of juvenile wood Zobel and Sprague 1998. The microstructure of poplar cultivars and douglas-fir were presented on Figure 2a and 2b. In
addition, Langum et al. 2009 reported that flexural stiffness and strength in solid douglas-fir increase with increasing distance from pith to bark. Therefore,
determination of transition area between juvenile and mature wood is very important.
The objective of this research was to analyze demarcation pointtransition age between juvenile and mature wood of sengon, jabon, poplar and douglas-fir
by segmented regression analysis.
2.2 Materials
The details information of the tree samples that were used in this study are shown in Table 2. After cutting, we took 2.5 m section in length from the bottom
part of each tree stem. Sample logs were wrapped in plastic and maintained in green condition before they were transported to the workshop for testing.
2.3 Method
The measurements of juvenility parameters were performed in three research facilities, Laboratory of Wood Anatomy and Physical Properties of Faculty of
Forestry, Bogor Agricultural University, Indonesia, LaBoMaP Laboratoire Bourguignon des Matériaux et des Procédés, Ecole National Superieure
d’Arts et Matiers ENSAM Cluny, Bourgogne, France and Laboratory INRA-
Centre de Nancy, France.
Table 2 Trees information for determination of demarcation pointtransition
age between juvenile and mature wood
Wood Species Growth Site
Age years
Diameter at breast high dbh cm
Sengon F. moluccana Sukabumi, Indonesia
5, 6 and 7 32-36
Jabon A. cadamba Sukabumi, Indonesia
5, 6 and 7 34-38
Douglas fir P. menziesii Cluny, France
26 34
Poplar cutivar I-214 P. deltoids Bartr. x P. nigra L.
Saint Nicholas la Chapelle and La Rèole, France
18 47-50
Poplar cutivar Koster P. deltoids Bartr. x P. nigra L.
Sainte Hermine and La Rèole, France
18 50-52
Poplar cutivar Lambro P. deltoids Bartr. x P. nigra L.
Sainte Hermine and La Rèole, France
18 47-53
Poplar cutivar Soligo P. deltoids Bartr. x P. nigra L.
Sainte Hermine and Saint Nicholas la Chapelle, France
18 48-54
2.3.1 Sample preparation for sengon and jabon
Discs of 2 cm thick Figure 3-A1 were cross-cut from the middle part of the log 1.3 m sampling height = diameter breast height dbh using band saw. The
rest of the cut logs Figure 3-B1 were kept as bending sample discs. From the A1 discs, flitches of 2 cm width were prepared from bark to bark through the pith
using a band saw for measurements of density, fibre length and microfibril angle
8 Figure 3-A2. The flitches were cut in segments of 1 cm thick from pith to bark
and numbered consecutively. Segments for determination of fibre length and microfibril angle were kept in green condition Figure 3-A3. From the B1 discs,
boards of 2.5 cm width were band sawn bark to bark through the pith for specimens of bending strength MOE and MOR tests Figure 3-B2. The boards
were also re-sawed in segments of 2 cm thick from pith to bark and numbered consecutively. Individual test specimens Figure 3-B3 were carefully air dried to
prevent warping.
Figure 3 Schematic drawing of the preparation of juvenility and bending test specimen for sengon and jabon
2.3.2 Sample Preparation for douglas-fir
The disks of 2 cm thick Figure 4-A1 were cross cut from the middle part 2 m above the ground of the sample log. From the A1 disks, flitches of 2.0 cm
width were prepared from pith to bark for specimens of fiber length, and MFA measurements Figure 4-A2. Douglas fir wood samples were cut according to its
annual ring segments from pith to bark they were numbered conscutively Figure 4-A3. The dimension of each douglas fir sample was 2 cm length x 2
cm width x 1 cm thickness.
Figure 4 Schematic drawing of the preparation of the tracheid length and MFA
measurement test for douglas-fir
Segmented rings from pith Wood disk
A1
B1
1 2 3 4
B2
Bending test specimen
B3 A3
Juvenility test specimen
1 2 3 4 A2
2 cm
A1 A2
Wood disk A3
Annual ring segments from pith to bark
1 2 3 4
2 cm 2 cm
A1
