WOOD RESEARCH Volume 71, Number 3, 2026
CHUN-WON KANG, Young-Woong Lee, HEE-JUN PARK, MASUMI HASEGAWA, Shinya Koga, and HARADHAN KOLYA

Comparative Surface Roughness Evolution of 33 Japanese Hardwoods after Water and Fire-Retardant Treatments Using 3D Optical Profilometry

In this study, we assessed the surface roughness of 33 Japanese hardwood species by 3D optical profilometry (ISO 25178) and examined the influence of water and fire-retardant treatments. The surface roughness on cross, radial, and tangential sections was evaluated using the arithmetic mean height (Sa) parameter. Measurements were performed on untreated samples and repeated on the same spots after water treatment and NF300 fire-retardant treatment. Surface roughness varied widely across species and anatomical sections and tended to decrease with increasing wood density. The surface roughness increased with both treatments compared to the untreated wood. The maximum increase was on tangential surfaces after NF300 treatment, where the mean Sa value increased from 30.14 ± 17.05 μm to 42.05 ± 19.60 μm (39.5%). The statistical analysis showed a significant difference between the untreated and NF300-treated tangential surfaces (p = 0.011).

WOOD RESEARCH Volume 71, Number 3, 2026
Xingyu Shao, MING LI, SAIYIN FANG, TINGTING DENG, KUN DU, JINGGUI WANG, WENTAO XU, and HAO SHI

The Study on the Frequency Response Characteristics of Wood Orthotropy Based on Stress Wave Propagation Direction and Distance

This study investigates the frequency response of Zelkova schneideriana and Pinus sylvestris var. mongholica Litv. along longitudinal, radial, and tangential directions at different propagation distances. Sinusoidal signals from 20 to 200 kHz with 2 kHz intervals were applied using a piezoelectric device, and the responses were recorded by an acoustic emission sensor. Frequency response curves were obtained from the amplitude ratios of response to excitation signals. The results showed that attenuation in the radial direction was lower than that in the longitudinal and tangential directions between 20 and 100 kHz. Both species exhibited stable characteristic response bands around 35, 154, and 188 kHz, which showed good agreement with one-dimensional elastic wave theory, with a minimum relative error of 0.48%. Zelkova schneideriana also exhibited a characteristic frequency near 79 kHz and more stable high-frequency responses.

WOOD RESEARCH Volume 71, Number 3, 2026
EKİM ELÇİN SOYTÜRK, Muratcan Aldemir, and SAIP NAMI KARTAL

Bioremediation of Wood Treated with CCA-C, ACQ, and MCQ Wood Preservatives by Phanerochaete chrysosporium Fungal Strains

This study investigated the bioremediation of wood treated with copper–chromium– arsenic (CCA-C), alkaline copper quat (ACQ), and micronized copper quat (MCQ) using two Phanerochaete chrysosporium fungal strains. Wood flour samples were incubated in fungal liquid cultures over 1 to 10 days. Fungal treatments removed substantially more copper than distilled water controls across all preservative types. Lower preservative loadings yielded copper extraction rates exceeding 90–95% for ACQ and MCQ, whereas higher loadings reduced efficiency. The P. chrysosporium Me strain demonstrated superior performance during later remediation stages. These findings confirm that P. chrysosporium effectively mobilizes copper from soluble and micronized formulations, offering a viable strategy for detoxifying waste wood and enabling resource recovery.

WOOD RESEARCH Volume 71, Number 3, 2026
Bekir Cihad Bal

Evaluation of Some Mechanical Properties of Metal-Mesh Reinforced Poplar Laminated Veneer Lumber

This study aimed to reinforce laminated veneer lumber boards produced with poplar veneers using metal mesh. The metal mesh and poplar veneers were bonded using polyurethane adhesive. A control group (group 1) and three experimental groups were formed. The metal mesh was placed inside the two outermost adhesive layers in group 2, inside the four outermost adhesive layers in group 3, and on the bottom surface (tensile zone) of the board in group 4. The modulus of rupture, modulus of elasticity in bending, splitting strength, and adhesion strength of the produced boards were investigated. According to the data obtained, the modulus of rupture and modulus of elasticity increased in the reinforced groups. Although the reinforcement in one group reached 20%, the other groups had smaller values. Therefore, the reinforcement effect of the metal mesh on the flexural properties remained limited. The splitting strength increased significantly. Compared to the control group, the splitting strength of group 3 increased by approximately 80%. The adhesion strength decreased slightly in the reinforced groups.

WOOD RESEARCH Volume 71, Number 3, 2026
Yuxin Guo, ZIDONG GUO, Hailing Yue, and TIANWEI ZHANG

Influence of Traditional Plaster Layer on the Combustion Performance of Larch and Korean Pine Wood

This study investigated the effects of traditional plastering on the combustion behavior of timber used in historic structures. Larch and Korean pine specimens treated with the traditional one hemp fibre and five plaster layer technique were tested using a Fire Propagation Apparatus (FPA). The plaster layer shortened the time to ignition and promoted fire propagation during the early combustion stage, while markedly reducing the peak heat release rate and toxic gas production and increasing the char yield of the wood specimens. These findings clarify the dual effect of traditional plastering on timber combustion and provide experimental evidence for assessing the fire performance of traditionally plastered components in historic timber buildings.

WOOD RESEARCH Volume 71, Number 3, 2026
Fanny Hidayati, Sugeng Pudjiono, Ratna Adji Hartati, Erlangga Abdillah, Harry Praptoyo, Ananto Triyogo, Gefri Indra Hutabarat, Alfia Dewi Fadwati, Agung Prasetyo, and GANIS LUKMANDARU

Variation of Growth Characteristics and Stress-Wave Velocity of the First Generation Manglietia glauca Families Planted in Indonesia

Growth characteristics, including stem diameter (D), tree height (H), and stem volume (V), and wood property stress-wave velocity (SWV), were measured in 100 families of 7-year-old first-generation Manglietia glauca trees planted in Indonesia. Therefore, this study aimed to evaluate the variation in D, H, V, and SWV among the families and their heritability. An analysis of the correlations, principal components and selection index was also conducted. The presence of significant differences in all measured traits among the families indicate a genetic contribution to traits variation. Low to moderate narrow-sense heritability values were observed across all traits, showing that the genetic enhancement of growth and wood properties in M. glauca is achievable through selective breeding. Moderate to highly significant positive correlations were observed among the growth traits, highlighting their strong interrelationships. D and SWV showed a low significant positive correlation. H and V showed no significant correlation with SWV. Therefore, SWV should be included as selection criterion in M. glauca breeding. PCA and selection index are effectively for identified superior families of growth and strength traits, supporting their selection as candidates for future breeding programs.

WOOD RESEARCH Volume 71, Number 3, 2026
JÁN BRODNIANSKY, SILVIA MARTINKOVIČOVÁ, Jaroslav Sandanus, TOMÁŠ KLAS, JIŘÍ KUNECKÝ, JIŘÍ BLÁHA, and MICHAL KLOIBER

Experimental Investigation of Load Redistribution in a Historic-Type Timber Roof Segment Under Progressive Tie-Beam Weakening

This study examines how progressive loss of tie-beam stiffness redistributes deformation demand and internal force within an experimentally verified historic timber roof segment. A three-frame laboratory model was evaluated by close-range photogrammetry, inductive displacement sensing, post-test bending tests, and finite-element modelling. The measurements revealed clear frame-to-frame stiffness asymmetry, a distinct pre-cut settlement phase under sustained load, and accelerated deformation once the residual tie-beam section was substantially reduced. A refined model using member-specific elastic parameters reproduced the global loading response more accurately than a uniform-stiffness model. The damaged zone could also be represented by an equivalent rotational spring, although the fitted spring values remained response-dependent. The results indicate that lathing acted as a temporary redundancy path after severe weakening and that a nearly hinged residual section was not mechanically equivalent to a fully severed member within the tested configuration.

WOOD RESEARCH Volume 71, Number 3, 2026
QIANHUI HUO, LEI YAN, LILI YU, HUI LI, Jun Li, and SHU-GUANG LI

THE EFFECTS OF INTERFACIAL MODIFICATIONS ON THE PROPERTIES OF BAMBOO FIBER /WASTE TETRA PAK /PLA COMPOSITES

In this study, BF/TP/PLA ternary composite was constructed utilizing bamboo fiber (BF) as the reinforcing phase and waste Tetra Pak (TP) along with polylactic acid (PLA) as the matrix. The effects of different interfacial modification methods on the properties of the composites were systematically investigated. Bamboo fibers were modified using a silane coupling agent (KH570), nano-SiO2, and compatibilizers (MAH-g-PLA, MAH-g-PE). The composites were subsequently fabricated via hot pressing, and their mechanical properties, water absorption, chemical structure, and micromorphology were characterized. The results showed that after KH570 treatment, the flexural modulus and flexural strength of the composites increased by 15% and 32%, respectively. Following the introduction of compatibilizers, the water absorption was further reduced, and the thickness swelling rate was significantly improved. Optimal comprehensive performance was achieved at a nano-SiO2 content of 1 wt%; the flexural modulus reached 2524.1 MPa, exceeding the requirement of Chinese standard LY/T 3275-2021 for outdoor wood-plastic composites (≥2500 MPa), while the water absorption decreased to its lowest value (11.3%). Furthermore, interfacial bonding became more compact.

WOOD RESEARCH Volume 71, Number 3, 2026
SÜHEYLA ESİN KÖKSAL, ORHAN KELLECİ, and YASEMİN ÖZTÜRK

Surface Preparation for Lamination of OSB with Phenol Formaldehyde Film and Melamine Formaldehyde Decorative Paper

This study investigated the lamination of oriented strand board (OSB) surfaces using phenol formaldehyde impregnated polymer film (PF) and melamine formaldehyde impregnated decorative paper (MF). To enhance surface smoothness, OSB panels were sanded and treated with different putty systems, including commercial wood putty, polyvinyl acetate (PVAc), and polyvinyl alcohol (PVA). Ground hazelnut shell and furnace slag particles were incorporated as fillers at a 10% loading level. Results revealed that PF film laminated samples demonstrated significantly superior physical and mechanical performance compared to MF laminated boards. Among all specimens, the sample, prepared exclusively with wood putty and laminated with PF film, achieved the best overall performance, exhibiting the lowest water absorption (WA) and thickness swelling (TS) alongside the highest modulus of rupture (MOR), modulus of elasticity (MOE), abrasion resistance, and surface soundness (SS) values. Although hazelnut shell and furnace slag additions generally reduced putty system performance, their incorporation into PVAc and PVA-based formulations improved certain surface properties.

WOOD RESEARCH Volume 71, Number 3, 2026
SAIP NAMI KARTAL, EKİM ELÇİN SOYTÜRK, YUKO ITO, and WAKAKO OHMURA

Preliminary Evaluation of Copper Leaching from Commercially Available Wood Species in Japan Treated with Copper Azole Wood Preservative

This study examined copper fixation and leaching in wood treated with copper azole (CuAz) and copper sulfate (CuSO₄), emphasizing the effects of wood species and post-treatment conditions. Five Japanese softwoods, including Sugi, Hinoki, and Douglas fir, were assessed under three conditions: unfixed, ambient-fixed, and heat-treated (60°C for 3 days). Copper fixation was defined as the proportion of non-leachable copper remaining after standardized leaching, with release rates measured via leachate analysis. Results showed that post-treatment condition is the dominant factor controlling copper stabilization. Heat treatment significantly enhanced fixation and reduced leaching across all species and preservative types, indicating improved bonding between copper ions and wood components. Ambient fixation was often insufficient. Sugi sapwood showed the highest leaching, while Hinoki heartwood exhibited the greatest retention. Overall, CuAz outperformed CuSO₄, underscoring the importance of formulation in improving copper stability and durability.

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 71, Number 3, 2026
FIRDUS HAVERAJ, GERTI XHIXHA, and Dritan Ajdinaj

Short notes. COMPARATIVE STUDY OF THE IMPACT OF THERMAL MODIFICATION PARAMETERS ON THE THERMAL CONDUCTIVITY OF DIFFERENTWOOD COMPOSITE PANELS

This study examined how thermal modification influenced the thermal conductivity of plywood, oriented strand board, and medium-density fiberboard. Samples were exposed to two temperature levels, 130°C and 180°C, for 20 and 40 min, while untreated panels were retained as controls. Measurements were carried out under controlled laboratory conditions using the steady-state hot-box method. The thermal modification consistently reduced thermal conductivity across all materials, which suggests improved insulation properties. The observed reductions varied. OSB exhibited the most significant overall decrease in thermal conductivity, while plywood displayed relative stability; conversely, MDF demonstrated a marked reaction under the more rigorous treatment conditions. The type of material used had the most significant overall statistical effect. The duration of the treatment was more important than the temperature. The interaction between temperature and time did not achieve statistical significance within the parameters of the experiment; conversely, interactions involving material type were significant.