Within-tree and radial variations of wood properties in naturally regenerated trees of Betula platyphylla grown in Nikko, Japan

Abstract

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.

Modeling of radial variations of wood properties in naturally regenerated trees of Betula platyphylla grown in Selenge, Mongolia

“…japonica (Miq.) H. Hara naturally grown in Japan, we recently reported that the boundary determined by radial variations of fiber length was around 1.5 to 4.2 cm from the pith or the 10th to 17th annual ring from the pith [9]. Similar results in terms of radial variations of the density and mechanical properties have been obtained in other Betula species (e.g., B. ermanii Cham., B. maximowicziana Regel, B. pendula Roth, and B. platyphylla), where the region around 5 to 8 cm from the pith has been clearly marked as a low-density and low-strength properties region [16][17][18].…”

“…Similar results in terms of radial variations of the density and mechanical properties have been obtained in other Betula species (e.g., B. ermanii Cham., B. maximowicziana Regel, B. pendula Roth, and B. platyphylla), where the region around 5 to 8 cm from the pith has been clearly marked as a low-density and low-strength properties region [16][17][18]. These radial variations of wood properties might be related to the xylem maturation process [9,[11][12][13][14][15]18]. Therefore, further research is needed to clarify the xylem maturation process for B. platyphylla trees grown in Mongolia to understand the core wood and outer wood properties.…”

“…The Betula species is distributed in the temperate to subarctic zones of northeast Asia, including western and northern China, Japan, Korea, and Mongolia [1][2][3][4][5][6]. The basic wood properties of the Betula species have been investigated by several researchers for efficient utilization of the wood from this species (e.g., [1,[7][8][9]).…”

“…In general, wood properties in hardwoods vary within the tree: unstable wood properties are found in core wood near the pith, while stable properties are found in the outer wood near the bark or cambium [10][11][12][13][14]. The radial variations in cell length are usually used to determine the boundary between these two regions in hardwood species [9,14,15]. In Betula platyphylla Sukaczev var.…”

“…The relationships between growth characteristics and wood properties have been investigated for both softwoods and hardwoods [10,11,19]. Several researchers have investigated these relationships in Betula species specifically (e.g., [2,3,8,9,20]). Heräjärvi [20] reported significant positive correlations between wood density and static bending properties, such as the modulus of elasticity (MOE) and modulus of rupture (MOR), in 60-90-year-old B. pendula and B. pubescens Ehrh.…”