WOOD RESEARCH Volume 71, Number 3, 2026
DOAN VAN DUONG and MASUMI HASEGAWA

VARIATION IN BASIC DENSITY AND TRANSVERSE SHRINKAGE AMONG SIX EUCALYPTUS CLONES PLANTED IN VIETNAM

This study examined clonal and radial variation in basic density (BD) and transverse shrinkage among six Eucalyptus clones grown under uniform conditions in north-central Vietnam. A total of 30 ramets were sampled, and 196 small clear specimens were prepared from positions near the pith and the bark. Partial and total shrinkage in tangential (Tn, T) and radial (Rn, R) directions were determined following ISO 13061-13:2017. Basic density (BD) ranged from 0.39 to 0.50 g/cm³ and increased consistently from pith to bark. Tangential shrinkage (Tn: 4.45–5.83%; T: 5.64–6.85%) showed greater variation among clones than radial shrinkage (Rn: 2.95–3.32%; R: 3.89–4.72%). Clone U1427 showed the highest BD while also presenting the lowest shrinkage values, suggesting excellent dimensional stability and considerable potential for utilization in solid wood and lumber production in northern Vietnam.

WOOD RESEARCH Volume 70, Number 4, 2025
DOAN VAN DUONG and MASUMI HASEGAWA

NONDESTRUCTIVE PREDICTION OF BENDING STRENGTH OF PINUS MASSONIANA LAMB. LOGS AND SMALL CLEAR SPECIMENS USING STRESS-WAVE MEASUREMENTS

The main objective of this study was to investigate the relationships between stress-wave velocity measured in logs and small clear specimens and the bending strength of Pinus massoniana trees planted in northern Vietnam. Stress-wave velocity (SWVL) and green wood density (WDL) were measured on logs collected from different heightlevels of 23-year-olds P. massonianatrees. Stress-wave velocity (SWVS), wood density (WDS), and bending strength (MOR) were subsequently determined on small clear specimens prepared from the logs. Regression analyses revealed significant correlations between SWVL and MOR (r = 0.73, P < 0.001) and between SWVS and MOR (r = 0.80, P < 0.001). These results show that stress-wave velocity measurements, whether taken on logs or small specimens, are effective for segregating P. massoniana lumber resources based on MOR. A more accurate prediction of strength was obtained when stress-wave velocity and log or specimen wood density were used together to calculate the dynamic modulus of elasticity of logs (DMOEL) or specimens (DMOES), respectively. The correlation coefficients were 0.82 (P < 0.001) between DMOEL and MOR, and 0.93 (P < 0.001) between DMOES and MOR.

WOOD RESEARCH Volume 70, Number 2, 2025
CHUN-WON KANG, MASUMI HASEGAWA, KAWANISHI MARIA, and HARADHAN KOLYA

Short notes. INFLUENCE OF WOOD ANATOMY ON THE DISTRIBUTION OF GUANIDINE BASED FIRE RETARDANTS IN FIVE FAST GROWING JAPANESE HARDWOODS

This study investigates the influence of wood anatomy on the distribution of fire retardant chemicals in five fast-growing Japanese hardwood species (Melia azedarach, Toona sinensis, Choerospondias axillaris, Alnus japonica, and Liriodendron tulipifera). Given Japan’s increasing demand for sustainable and locally sourced materials, fire retardant treatments are critical for enhancing fire resistance in fast-growing hardwoods used for construction. Using low vacuum scanning electron microscopy (SEM), we examined the distribution of fire retardants in cross-section, radial section, and tangential sections, comparing the effectiveness in ring-porous versus diffuse-porous species. Results revealed that diffuse-porous species (Alnus japonica and Liriodendron tulipifera) retained higher levels of fire retardants with a more even distribution. In contrast, ring-porous species (Melia azedarach, Toona sinensis, Choerospondias axillaris) showed the highest chemical concentration at the edges.

WOOD RESEARCH Volume 70, Number 1, 2025
CHUN-WON KANG, MASUMI HASEGAWA, and HARADHAN KOLYA

EFFECTS OF HOLE PERFORATION AND SURFACE CUTTING ON WOOD ELASTICITY USING ULTRASONIC AND VIBRATION METHODS

This study analyzed how hole perforation and surface cutting affect ultrasonic wave propagation velocity and resonant frequency in wood. While non-destructive evaluation techniques for wood elasticity are well-established, the specific influence of defects like holes and orthogonal cuts on wave behavior remains underexplored. This study aimed to fill this gap by assessing how these defects influence wave behavior and providing new insights into their impact on wood’s mechanical properties. Four softwood species and seven hardwood species were analyzed. In hardwood specimens, ultrasonic propagation velocity and resonant frequency were measured under increasing levels of hole perforation (9, 27, and 45 holes). In contrast, the effects of one and two orthogonal surface cuts were examined in softwood specimens. The results revealed that the ultrasonic propagation velocity decreased noticeably with an increasing number of holes. Meanwhile, resonant frequency exhibited only a slight decrease. In contrast, softwoods displayed minimal changes in ultrasonic velocity but notable reductions in resonant frequency due to surface cutting. This study highlights the differences in continuous wave propagation pathways associated with the two defect types and estimation methods, offering novel insights into wood evaluation techniques

WOOD RESEARCH Volume 70, Number 1, 2025
DOAN VAN DUONG, VAN HUNG HOANG, MASUMI HASEGAWA, and EVGENII SHARAPOV

THE INFLUENCE OF TREE AGE AND RADIAL POSITION ON THE STRESS-WAVE VELOCITY AND TIMBER PROPERTIES OF PINUS MASSONIANA LAMB. PLANTED IN VIETNAM

The main objective of this study is to investigate the influence of tree age and radial position on the structural properties, asair-dry density (AD), modulus of rupture (MOR), modulus of elasticity (MOE) and the stress-wave velocity measured on small specimens (SWVS). Results of analysis showed a highly significant effect of age and radial position on the SWVS, AD, MOR, and MOE. Stress-wave velocity and wood property traits tend to increase with increasing tree age. The SWVS and selected wood properties near the pith were significantly lower than those near the bark. Mean MOR and MOE of the timber had significantly (P<0.001) relationships with SWVS (r = 0.75 and 0.91, respectively), although in the case of MOR a model based on AD alone is slightly better (r = 0.79). There were also significant relationships of acoustic velocity measured in standing trees (SWVT) with mechanical properties measured destructively in small specimens implying that stress-wave method has a good potential for measuring static bending properties of P. massonianaplanted in Vietnam

WOOD RESEARCH Volume 69, Number 4, 2024
DOAN VAN DUONG, MASUMI HASEGAWA, MANH TUONG VU, and VAN HUNG HOANG

RADIAL AND AMONGCLONAL VARIATIONS OF TRANSVERSE SHRINKAGE AND BASIC DENSITY IN 5-YEAR-OLDACACIA AURICULIFORMIS CLONES PLANTED IN VIETNAM

This study investigatedtransverse shrinkages and wood density for Acacia auriculiformis trees from six clones planted in north-central Vietnam. Radial and among-clonal variations of partial and total shrinkages in tangential (respective to Tn and T) and radial (respective to Rn and R) directions, partial and total coefficient of anisotropy (respective to Tn/Rn and T/R), and basic density (BD) were examined. There were significant differences among clones for Rn and R, but no significant differences were found among clones for Tn and T. The lowest average Rn and R were detected in clones Clt18 and Clt26, suggesting that these clones might be more appropriate for breeding programs focused on improving shrinkage traits for sawn timber production. BD is not a good indicator for predicting transverse shrinkages. In contrasts, stress wave velocity measured in standing trees has the potential to be used as a non-destructive method for predicting the transverse shrinkage of A. auriculiformis planted in Vietnam

WOOD RESEARCH Volume 69, Number 2, 2024
HARADHAN KOLYA, MASUMI HASEGAWA, KAZUHARU HASHITSUME, and CHUN-WON KANG

EFFECTS OF CHEMICAL AND PHYSICAL TREATMENTS ON BAMBOO CELL WALL STRUCTURE FROM ENGINEERING PERSPECTIVES

This study focuses on the effects of chemical treatment using polyethylene glycol (PEG) and physical treatment via steam explosion and microwave, with a comprehensive analysis using ATR-FTIR, X-ray diffraction, Keyence VR 6000 optical profilometer, and SEM. The aim is to elucidate alterations in bamboo cell walls following these treatments compared to untreated bamboo. The results reveal significant modifications in the chemical composition and crystalline structure of bamboo cell walls post-treatment. ATR-FTIR analysis indicates changes in functional groups, suggesting chemical interactions and modifications in the molecular arrangement of cell wall components. XRD analysis further corroborates these findings by revealing shifts in crystallinity and peak intensities, signifying structural rearrangements, as evidenced by optical images and SEM micrographs