No abstract

To preliminary evaluate the potential wood utilization of Sukaczev trees naturally regenerated in Mongolia, growth characteristics (stem diameter and tree height), wood properties (annual ring width, basic density, and compressive strength parallel to grain at the green condition) of core samples, and stress-wave velocity in stems were investigated for trees grown naturally in three different sites in Selenge, Mongolia. trees, naturally grown in Nikko, Japan, were also examined to compare wood properties between the two regions. The mean values of stem diameter, tree height, stress-wave velocity of stems, annual ring width, basic density, and compressive strength parallel to grain at green condition in Mongolian were 17.6 cm, 14.1 m, 3.50 km s, 1.27 mm, 0.51 g cm, and 20.4 MPa, respectively. Basic density and compressive strength were decreased first from the pith, and then gradually increased toward the bark. The wood properties of trees grown naturally in Mongolia were similar to those in trees grown in Japan. Growth characteristics, especially stem diameter, were positively correlated with the stress-wave velocity of stems and basic density. Early evaluation of basic density in trees is possible by using wood located 2 cm from the pith. Basic density at the position from the 1st to the 15th annual ring from the pith showed significant between-site differences in Mongolian . Based on the results, it is concluded that the wood of trees grown in Mongolia may be used for industrial products as well as those from similar species in other countries.Betula platyphyllaBetula platyphyllaBetula platyphyllaB. platyphylla–1–3B. platyphyllaB. platyphyllaB. platyphyllaB. platyphyllaB. platyphylla

The modulus of elasticity (MOE) and modulus of rupture (MOR) were evaluated for 190 pieces of dimension lumber (2 by 4 lumber, 38 by 89 mm in cross-section) produced from Larix sibirica trees grown in Mongolia. The 5% tolerance limits of the MOE and MOR were 5.70 GPa and 15.1 MPa, respectively. The value of the 5% tolerance limit of the MOR exceeded the characteristic value of 2 by 4 lumber in visual grading class No. 3 of the Japanese Agricultural Standard for the D. fir-L, Hem-Tam, JS-III and S-P-F softwood species groups. A significant positive correlation was found between the MOE and MOR, although air-dry density was weakly correlated with bending properties in L. sibirica.

Wood properties were investigated for nine naturally regenerated trees of Betula platyphylla Sukaczev var. japonica (Miq.) H. Hara in Nikko, Japan to effectively utilise the wood resources. The following properties were determined: stress-wave velocity of stems in radial direction, cell length, basic density, shrinkage, dynamic Young's modulus, modulus of elasticity, modulus of rupture, absorbed energy in impact bending, and compressive strength parallel to grain. All examined wood properties increased from pith to bark. The boundary between core and outer wood determined by a 1.0% annual increment of cell lengths was well matched with that determined by radial variations of wood properties. Significant differences were found between the core and outer wood in several wood properties. Based on the results, it is concluded that when the wood of B. platyphylla is utilised as an industrial raw material, the presence of core and outer wood should be considered.

Pinus sylvestris L., Pinus sibirica Du Tour, Picea obovata Ledeb., and Larix sibirica Ledeb. are important forest tree species in Mongolia. The radial variations of wood anatomical characteristics, physical and mechanical properties were evaluated by linear or nonlinear mixed-effects models for effective wood utilization of those of conifers. Many of these wood properties either increased or decreased from the pith to the bark and then became nearly constant based on the selected models. The properties of mature wood were estimated by nonlinear mixed-effects models, suggesting that P. sylvestris and L. sibirica are suitable as structural lumber, P. sibirica can be used for furniture and other interior products, and P. obovata is suitable for structural lumber as well as for furniture or interior products.

Longitudinal and geographic variations in the green moisture content and basic density of bamboo culm were evaluated by using linear mixed-effect models for three bamboo species (Bambusa vulgaris Schrad. ex J.C., Bambusa maculata Widjaja, and Gigantochloa atter (Hassk) Kurz ex Munro) naturally grown in four locations in Lombok Island, Indonesia. The mean green moisture contents and basic densities were 74.2 % and 0.69 g cm −3 for B. vulgaris, 78.5 % and 0.65 g cm −3 for B. maculata, and 80.3 % and 0.65 g cm −3 for G. atter, respectively. No significant differences in green moisture content and basic density were found among the species. A significant negative correlation between basic density and green moisture content was found in all three species. Based on the results of model selections for longitudinal variations, the green moisture content decreased with an increase in the culm height in all three species, and basic density tended to increase from the base to the top of the culm. Relatively large geographical variation was found in the green moisture content and basic density of G. atter, although the main reasons for variation of these properties were individual culm in three species.

We examined the physical and mechanical properties of wood in Siberian larch (Larix sibirica) trees that grow naturally in five Mongolian provenances (Khentii, Arkhangai, Zavkhan, Khuvsgul, and Selenge) and the geographic variations between them. Five trees with stem diameters of 20 to 30 cm at 1.3 m above ground were collected from each provenance. The mean values of the modulus of elasticity (MOE), modulus of rupture (MOR), compressive strength parallel to grain (CS), and shearing strength (SS) ranged from 7.03 to 9.51 GPa, 79.8 to 103.9 MPa, 46.3 to 51.1 MPa, and 10.4 to 13.0 MPa, respectively. Significant differences were found in radial and tangential shrinkage, MOE, MOR, and SS in wood among the five provenances. In addition, juvenile wood had inferior physical and mechanical properties in comparison to mature wood within and among provenances. Furthermore, there were significant differences in all examined properties, except for CS, in mature wood among the five provenances. Higher correlation coefficients were also obtained in mature wood among all mechanical properties, except for SS. Larix species are one of the most productive forestry species in North America 1-4 , Europe 5-12 , Japan 13-24 , and China 25,26. To date, several studies have focused on geographic variations in the physical and mechanical properties of wood in Larix species to determine effective wood utilization and conduct appropriate tree breeding programs 1,3-5,15,18,19,23,24. For example, geographic variations have been found in the physical and mechanical properties of wood in Larix kaempferi 1,4. A similar tendency was also found for another Larix species, Larix sibirica 5. In addition to geographic and/or genetic variations in the physical and mechanical properties of wood, radial variations should also be considered for effective wood utilization 11,12,23-25,27. In general, softwood can be classified as juvenile or mature wood. Juvenile wood is characterized by a greater microfibril angle, a lower basic density, and inferior mechanical properties compared to mature wood 12-15,17,23,24,26,28,29. In a study of 31-year-old L. kaempferi trees, wood density and wood mechanical properties, such as modulus of elasticity (MOE), modulus of rupture (MOR), compressive strength parallel to grain (CS), and shearing strength (SS), showed lower values in corewood (from the pith to the 15th annual ring) than in outer wood (from the 15th annual ring to the bark) 24. Therefore, based on the nature of Larix species, (1) trees of these species with superior physical and mechanical properties of wood can be selected, and (2) the properties of juvenile wood should be considered for determining effective wood utilization. In Mongolia, the total forest area is 18.3 million ha, covering 11.9% of the country 30. Of this total area, Larix sibirica covers more than 70% of the forest. Since wood produced from Larix species is mainly utilized for structural applications, sawmilling is one of the main forest activities in Mongolia. Indeed, L. sibirica is the m...

This study aims to investigate whether it is possible to predict the modulus of elasticity (MOE) and modulus of rupture (MOR) of lumber produced from different heights using the stress-wave velocity of standing trees or the dynamic Young's modulus of logs in Siberian larch (Larix sibirica). A total of 190 pieces of lumber (38 by 89 mm in cross section) were cut from 111 logs obtained from 25 standing trees. Significant positive correlation coefficients were found between the stress-wave velocity of standing trees and MOE (r = 0.776) and MOR (r = 0.702) of this lumber. The dynamic Young's modulus of the logs also correlated significantly with MOE (r = 0.745) and MOR (r = 0.584) values. The results obtained in the present study suggest that stress-wave velocity and dynamic Young's modulus are useful for selecting superior trees in tree breeding and sorting logs for producing structural lumber.