Abstract
In order to promote plantation establishment of Larix gmelinii var. olgensis (syn. L. olgensis A. Henry), a ‘near threatened’ species, the wood and lumber properties were preliminary investigated for five trees from two clones of 57-year-old trees planted in Japan. The mean value of dynamic Young’s modulus of logs was 10.16 GPa. The mean values of annual ring width, latewood percentage, basic density, MOE, and MOR of five sample trees were 2.1 mm, 29.3%, 0.47 g•cm-3, 8.06 GPa, and 60.4 MPa, respectively. In addition, the MOE and MOR of 2 by 4 lumber were 10.43 GPa and 42.4 MPa, respectively. These values were similar to those obtained from other Larix species. Thus, construction lumber could be produced from the wood from plantation grown L. gmelinii var. olgensis.
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Wood and Lumber Properties of Larix gmelinii var. olgensis Planted in Japan
Futoshi Ishiguri,a,* Taiichi Iki,b Kouhei Otsuka,c Yusuke Takahashi,a Ikumi Nezu,a Bayasaa Tumenjargal,a,d,e Jyunichi Ohshima,a and Shinso Yokota a
In order to promote plantation establishment of Larix gmelinii var. olgensis (syn. L. olgensis A. Henry), a ‘near threatened’ species, the wood and lumber properties were preliminary investigated for five trees from two clones of 57-year-old trees planted in Japan. The mean value of dynamic Young’s modulus of logs was 10.16 GPa. The mean values of annual ring width, latewood percentage, basic density, MOE, and MOR of five sample trees were 2.1 mm, 29.3%, 0.47 g•cm-3, 8.06 GPa, and 60.4 MPa, respectively. In addition, the MOE and MOR of 2 by 4 lumber were 10.43 GPa and 42.4 MPa, respectively. These values were similar to those obtained from other Larix species. Thus, construction lumber could be produced from the wood from plantation grown L. gmelinii var. olgensis.
Keywords: Larix gmelinii var. olgensis; Annual ring width; Latewood percentage; Basic density; Bending property
Contact information: a: School of Agriculture, Utsunomiya University, Utsunomiya 321-8505, Japan; b: Tohoku Regional Breeding Office, Forest Tree Breeding Center, Forest and Forest Products Research Institute, Takizawa, Iwate 020-0621, Japan; c: Tochigi Prefectural Forestry Center, Utsunomiya 321-2105, Japan; d: United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan; e: Research and Training Institute for Forestry and Wood Industry, Mongolian University of Science and Technology, Ulaanbaatar, Mongolia;
* Corresponding author: ishiguri@cc.utsunomiya-u.ac.jp
INTRODUCTION
Larix gmelinii var. olgensis (syn. L. olgensis A. Henry) is a species of larch distributed widely in Olga bay, Primorskaya Oblast, Russia, the north part of the Korean peninsula, and the northeast part of China (Vasyutkina et al. 2007). This species is a ‘Near Threatened’ species in IUCN Red List, although it is considered an important forestry resource in China (Wang et al. 2006; Li et al. 2011; Peng et al. 2018). In Japan, L. gmelinii var. olgensis and other Larix species have been introduced to produce hybrid larch with L. kaempferi (Takahashi et al.1968). However, data on the properties of L. gmelinii var. olgensis is very limited (Nakagawa 1963), compared with L. kaempferi planted in Japan (Takada et al. 1992; Takata and Hirakawa 2000; Nagao et al. 2003; Koizumi et al. 2005; Nakada et al. 2005; Ishiguri et al. 2008).
Kubojima et al. (2010) pointed out that, for Picea koyamae, a ‘critically endangered’ species in the IUCN Red List, if the wood of this species from appropriate plantations can be utilized, the extinction of this species might not occur. This is also true for L. gmelinii var. olgensis that it could be a possible valuable wood resource, as the wood of the other Larix species are mainly utilized as construction lumber (Iijima 1983; Miyajima 1985; Tokumoto et al. 1997; Takeda 2000; Nagao et al. 2003; Ishiguri et al. 2008). Therefore, wood properties of the species should be clarified to enhance the establishment of plantation of this species.
In the present study, five trees from two clones of L. gmelinii var. olgensis were obtained by thinning treatment in a progeny test site located in Iwate, Japan. Available information was very limited for wood and lumber properties of this species. Thus, wood and lumber properties were preliminary investigated to consider the establishment of plantation of this species in Japan, although number of sample trees were limited.
EXPERIMENTAL
A total of five trees from two clones (three trees from one clone, and two trees from the other clone) of 57-year-old Larix olgensis A. Henry were used in the present study. The trees were planted in the progeny test site, Tohoku Regional Breeding Office, Forest Tree Breeding Center, Forestry and Forest Products Research Institute, Iwate, Japan (39°49’N, 141°08’E, 652 m above sea level) in 1960. The trees were cut down after measuring the stem diameter at 1.3 m above the ground (Table 1).
Table 1. Stem Diameter, Tree Height, and Dynamic Young’s Modulus of Logs in Sample Trees
Note: Dynamic Young’s modulus (DMOE) of logs. A and B indicate individual clones. Values in parentheses followed by mean values indicate standard deviations.
After cutting down the trees, two logs in each tree were obtained from 1.0 m to 1.5 m, and from 1.5 m to 3.5 m above the ground (Fig. 1). The shorter length logs and the longer length logs were used for measuring wood and lumber properties, respectively. Before producing lumber, dynamic Young’s modulus (DMOE) of the longer length logs was determined by the tapping method (Sobue 1986).
Fig. 1. Illustration of the experimental procedure
Radial variations of the wood properties such as annual ring width, latewood percentage, basic density, and static bending properties were evaluated. Sample specimen disks of 3 cm in thickness were obtained from the shorter length logs in order to evaluate the wood properties except static bending properties (Fig. 1). Pith to bark strip was prepared from the disk sample, and the surface of the strip was sanded. Digital images (1200 dpi) of transverse sections were obtained by a scanner (GT-9300UF, Epson). Due to narrower annual rings in some samples, small blocks were prepared, and then the transverse surface was trimmed by a sliding microtome. The transverse images were obtained by a stereomicroscope (SZX12, Olympus, Tokyo, Japan) with a digital camera. Width and latewood width at every annual ring were determined by using a software (ImageJ, National Institute of Health, USA). To determine the basic density, a wedge-shaped specimens were prepared from the disk (Fig. 1). The wedge-shaped specimens were again cut at 5-year interval until the 30th annual ring from pith. Due to narrower annual rings, the specimens could not be cut after the 35th annual ring from pith. Basic density was calculated using oven-dry weight samples divided by green volume determined by water displacement method. Small-clear specimens for static bending test (ca. 320 (L) × 20 (R) × 20 (T) mm) were prepared from bark to bark radial boards (20 mm in thickness) obtained from the shorter length logs (Fig. 1). The radial boards were air-dried in laboratory (with air-conditioner, but without humidity control), and then cut at 20-mm interval from pith. Static bending test was conducted by using a universal testing machine (MSC-5/200-2, Tokyo Testing Machine) with a span of 280 mm. The load was applied to the center of radial surface of the specimens at the load speed of 5 mm/min. Modulus of elasticity (MOE) and modulus of rupture (MOR) were calculated from the obtained data. Due to lower moisture content of the specimens (mean ± standard deviation = 6.4 ± 0.3%), the MOE and MOR values were adjusted to those at 12% moisture content (Murata 2017).
The longer logs were sawn into 12 pieces of lumber (50 mm × 100 mm in cross section) (Fig. 1). The lumber was kiln dried at 70 °C to 75 °C of dry-bulb temperature and 43 °C to 86 °C for wet-bulb temperature for 114 h. After kiln drying, the surface of lumber was planed into 38 mm × 89 mm in cross section. Before static bending test, bow, crook, and twist were determined. In addition, DMOE of lumber were also measured by the methods described above. Four-points static bending test was conducted by using a material testing machine (IPA-100R, Maekawa, Tokyo, Japan) under the following conditions: load speed of 14 to 16 mm/min, support span of 1602 mm, distance between load points of 534 mm. After bending test, small-clear specimens were collected and moisture content, density at testing, and annual ring width were measured for the lumber.
RESULTS AND DISCUSSION
The dynamic Young’s modulus of sample logs is listed in Table 1. The DMOE values of logs ranged from 9.25 to 11.08 GPa, resulting in the mean value of 10.16 GPa. Nakada et al. (2005) reported that the DMOE of logs from 472 plus trees of L. kaempefri planted in Japan ranged from 5.7 to 15.2 GPa, and the mean value was 11.4 GPa. Similar results for L. kaempefri planted in Japan were obtained by several researchers (Takata and Hirakawa 2000; Nagao et al. 2003; Ishiguri et al. 2008). On the other hand, the DMOE of logs from L. sibiricawas 7.6 to 11.2 GPa in Russia (Koizumi et al. 2003), 5.17 GPa to 9.72 GPa in five different provenances of Mongolia (Tumenjargal et al. 2018), and 6.31 GPa to 9.65 GPa in Tosontsengel, Mongolia (Ishiguri et al. 2018). It is considered that the DMOE of L. gmelinii var. olgensis used in the present study is similar to those of L. kaempferi planted in Japan, but relatively higher compared to those of L. sibirica grown in Russia and Mongolia.
Figure 2 shows the radial variation of annual ring width. Annual ring width rapidly increased from pith and then showed peak values. After that, it gradually decreased up to around 30thannual ring from pith and then became a constant value. The mean value of five trees was 2.1 mm (Table 2).
Fig. 2. Radial variations of annual ring width and latewood percentage. Solid lines indicate average values from five trees.
Latewood percentage increased from 30% to 40% at around the 15th annual ring from pith and then fluctuated from 30% to 40% (Fig. 2) with the mean value of five logs was at 29.3% (Table 2). Similar results were obtained in L. kaempferi by Takada et al. (1992): latewood percentage was 22% to 25% in core wood (pith side), and 37% to 47% in outer wood (bark side). Karlman et al. (2005) examined latewood percentage in five different Larix species (L. sibirica, L. sukaczewii, L. decidua, L. x eurolepis, and L. kaempferi) with different ages. They found that first 20 annual rings of the Larix species constituted the juvenile wood and had usually a latewood percentage less than 30%. After the period, L. decidua and L. sibirica had about 40% to 50%, and 40% of latewood, respectively. Radial variation of latewood percentage in the present study was similar to those obtained in other Larix species (Takada et al. 1992; Karlman et al. 2005; Luostarinen 2011). On the other hand, Luostarinen (2011) found no significant correlation between annual ring width and latewood percentage in L. sibirica planted in Finland. In L. kaempferi wood planted in Japan, a significant negative correlation was found between them in outer wood, but no significance in core wood (Takada et al. 1992) was observed. The obtained results in the present study (r = -0.499, p < 0.01, Fig. 3) were similar to those obtained in outer wood of L. kaempferi planted in Japan (Takada et al. 1992).
Table 2. Wood Properties of L. gmelinii var. olgensis
Note: n, number of radial positions in ‘A1 to B5’ and number of trees in ‘mean / total’; SD, standard deviation; OD, oven-dry density; MOE, modulus of elasticity; and MOR, modulus of rupture. A1 to B5 indicate individual tree. MOE and MOR values were adjusted to those at 12% MC by the methods described by Murata (2017).
Fig. 3. Relationships between annual ring width, latewood percentage, and basic density. r, coefficient of correlation; *, significance at 5% level; **, significance at 1% level; ns, no significance. Circles in those figures indicate mean values at 5 annual rings and mean values after 30 annual ring from pith in each individual tree. Number of radial positions from five trees = 30.
In L. decidua, wood density determined by X-ray densitometry was generally lower near the center of stem than in mature outer wood (Keith and Chauret 1998). Koizumi et al. (2003) reported that ring density determined by X-ray densitometry gradually increased with ring number within the heartwood region and then decreased within the sapwood region in L. sibiricagrown in Russia. In 67-year-old L. kaempferi grown in Japan, Kawaguchi et al. (1987) reported that basic density increased from pith area (0.3 g•cm-3) to about the 15th annual ring from the pith (0.4 g•cm-3), and then gradually increased until reaching the maximum value (0.5 g•cm-3). After that, it gradually decreased and showed the values from 0.43 g•cm-3 to 0.45 g•cm-3. The results obtained in the present study were similar to those obtained in other Larix species: basic density was lower near pith area and then increased to 0.4 g•cm-3 to 0.5 g•cm-3 (Fig. 4). As shown in Table 2, the mean value of five sample logs was 0.47 g•cm-3. The mean value was similar to those in L. gmelinii var. olgensis planted in Japan (Nakagawa 1963), but was relatively higher compared to L. decidua (Nakagawa 1963), and L. kaempferi (Nakagawa 1963; Kawaguchi et al. 1987; Takada et al. 1992). It has been reported that, in Larix species, the basic density is significantly correlated with latewood percentage, but not with annual ring width (Nakagawa 1963; Takada et al. 1992; Luostarinen 2011). Similar tendency was also found in L. gmelinii var. olgensis in the present study (Fig. 3). On the other hand, Cáceres et al. (2017) pointed out that basic density and oven-dry density of L. kaempferi were affected by amounts of hot-water extractives. Thus, further research is needed for evaluating the effects of extractives on basic density of this species.
Fig. 4. Radial variation of basic density. Solid and dotted lines indicate mean values. Due to narrower annual ring width after 30th annual ring from pith, the basic density values were determined for one specimen (after 30th annual ring from pith to bark side) in each individual trees.
Figure 5 shows radial variations of MOE and MOR. Both MOE and MOR increased from pith to bark side. In other Larix species, the MOE and MOR values were the lowest near the pith and then increased until certain radial position. After that these values gradually decreased or became constant (Kawaguchi et al. 1987; Ishiguri et al. 2018). Tendency of radial variations in MOE and MOR were similar to that of other Larix species, although constant values were not found at bark side in the present study. As shown in Table 2, the mean values of MOE and MOR in five sample trees were 8.06 GPa and 60.4 MPa, respectively. The mean values obtained in the present study were relatively lower compared to those of L. kaempferi planted in Japan (Kawaguchi et al. 1987; Koizumi et al. 2005), L. sibirica naturally grown in Mongolia (Ishiguri et al. 2018), L. gmelinii var. olgensis planted in China (Bao et al. 2001), and hybrid larch (L. gmelinii var. japonica x L. kaempferi) planted in Japan (Fujimoto et al. 2006). Compared to 22 to 30 years old trees of L. laricina planted in Canada, the obtained mean values in the present study were relatively higher in MOE, but lower in MOR (Beaudoin et al. 1989).
Fig. 5. Radial variations in static bending properties of small-clear specimen. Solid lines indicate mean values.
Table 3 displays the lumber properties. Mean values of crook, bow, and twist of lumber were 0.01%, 0.08%, and 1.60°, respectively. The mean values of DMOE, MOE, and MOR of lumber were 10.99 GPa, 10.43 GPa, and 42.4 MPa, respectively. Miyajima (1985) reported that MOE and MOR of 2 by 4 lumber from 53-year-old L. kaempferi planted in Japan were 8.04 GPa and 42.5 MPa, respectively.
Table 3. Lumber Properties of L. gmelinii var. olgensis
Note: n, number of lumber; SD, standard deviation; ARW, annual ring width; MC, moisture content determined by oven drying method; WD, wood density at testing; DMOE, dynamic Young’s modulus determined by the tapping method; MOE, modulus of elasticity; and MOR, modulus of rupture.
In 2 by 4 lumber from Larix species grown in Russia, mean MOE and MOR values in each grading class ranged from 8.62 GPa to 13.23 GPa, and 24.2 MPa to 61.3 MPa, respectively (Iijima 1983). In addition, the mean value of MOR for 2 by 4 lumber from L. gmelinii grown in China ranged from 46.7 MPa to 65.1 MPa (Zhong and Ren 2014). The obtained results of MOE and MOR in L. gmelinii var. olgensis were similar to those in L. kaempferi planted in Japan. It is concluded, therefore, that plantation-grown L. gmelinii var. olgensis is suitable for construction of lumber production.
CONCLUSIONS
- In L. gmelinii var. olgensis (syn. L. olgensis A. Henry), a ‘Near Threatened’ species, the dynamic Young’s modulus of logs ranged from 9.25 GPa to 11.08 GPa.
- Mean values of annual ring width, latewood percentage, basic density, MOE, and MOR of five sample logs were 2.1 mm, 29.3%, 0.47 g•cm-3, 8.06 GPa, and 60.4 MPa, respectively.
- MOE and MOR of 2 by 4 lumber were 10.43 GPa and 42.4 MPa, respectively. These obtained values were similar to those in other Larix species.
- Based on the results, it is considered that the wood resource from plantation-grown L. gmelinii var. olgensis is suitable for lumber production.
ACKOWLEDGMENTS
The authors express sincere thanks to Mr. Banzragch Norovvanjil, Student, School of Agriculture, Utsunomiya University, Japan for assistance of the experiments.
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Article submitted: May 22, 2019; Peer review completed: July 29, 2019; Revised version received: August 13, 2019; Accepted: August 14, 2019; Published: August 21, 2019.
DOI: 10.15376/biores.14.4.8072-8081