Physical and mechanical properties of wood and their geographic variations in Larix sibirica trees naturally grown in Mongolia

Abstract

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...

Effects of radial growth rate on juvenile wood properties of Pinus sylvestris planted in Mongolia

“…Thus, further research is necessary to elucidate the relationships between microfibril angle and the mechanical properties of juvenile wood in P. sylvestris. On the other hand, correlation coefficients between mechanical properties were reported by several researchers (Pikk and Kask 2004, Tumenjargal et al 2020, Sarkhad et al 2022. Similar results were also obtained in the present study, suggesting that mechanical properties can be evaluated by other mechanical properties.…”

Radial variations of broad-sense heritability in wood properties and classification of load–deflection curves in static bending for six half-sib families of Chamaecyparis obtusa

“…The results showed that the boundary between juvenile and mature wood for each tree ranged between the 19th and 25th annual rings from the pith (Table 5). The boundary age obtained in the present study was similar to that of previous studies on other species [31][32][33]. Although the estimated boundary varies due to species, age, or methods, a nonlinear mixed-effects model based on the Michaelis-Menten equation is an alternative tool for determining the boundary between juvenile and mature wood with various random effects, such as environmental and genetic factors.…”

“…As shown in Table 4 In softwood species, wood properties differ dramatically between juvenile and mature wood [4,26,28,31]. Tracheid length has been used as a trait to determine the boundary between juvenile wood and mature wood [31][32][33]. Shiokura [32] used a logarithmic formula to describe the radial variation of tracheid length, and he also pointed out that for distinguishing between juvenile and mature wood, 1% of the increasing rate for tracheid length was desirable.…”

Classification of Principal Wood Species in China Based on the Physiomechanical Properties

“…Although statistical analysis has been used for processing complex data in wood science, the classification of wood species with respect to their physiomechanical properties is rare. The reason is twofold: 1) There are many physiomechanical properties, and these properties have certain variations among and within wood species [30]; 2) The recognition accuracy is low when extracting information from the properties [31]. Rational classification based on the physiomechanical properties is helpful for exploring the "properties-applications" relationships of wood and its rational utilizations.…”