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Summary: Betula platyphylla Sukaczev, a fast-growing pioneer tree, is an important species for wood resources in boreal regions and steppe areas in Mongolia. We examined the anatomy and maturation of wood in 30 B. platyphylla trees growing in natural populations in three different sites in Mandal, Selenge, Mongolia to clarify the relationship between tree growth and wood formation. Core samples, 5 mm in diameter, were collected from 30 trees with the mean stem diameter at each site. The radial variations in the anatomical characteristics were evaluated using linear or nonlinear mixed-effects models. Almost all measured anatomical characteristics increased from the pith to the bark. Fiber length showed an annual increase of over 1% up to about the 20th annual ring from the pith, beyond which the increase was less than 1%, suggesting that xylem maturation started around the 20th annual ring. The growth rate at the early growth stage did not affect the annual ring number where xylem maturation began. The linear mixed-effects model revealed a site variation in wood fiber wall thickness. Thus, in combination with previous research results with this species, we believe that the selection of superior trees with thicker fiber walls might be possible for future tree breeding programs aimed at improving wood quality for pulp and paper raw materials and the production of solid wood and wood-based materials. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]