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...
