Relationship between wood specific gravity and average annual ring width of 15 Korean wood species

Abstract

The correlation between specific gravity and average annual ring width was studied for 15 major Korean tree species. In coniferous trees, species with narrower rings exhibited higher specific gravity, with strong correlations observed in Pinus densiflora (Gangwon), Larix kaempferi, and Pinus rigida. In deciduous trees, the correlation between specific gravity and annual ring width did not exhibit a consistent pattern based on the distinction between diffuse-porous and ring-porous species. The correlation of Liriodendron tulipifera (diffuse-porous species) and Quercus mongolica (ring-porous species) showed higher specific gravity with wider rings, whereas other species, such as Betula platyphylla (diffuse-porous species) and Robinia pseudoacacia (ring-porous species) exhibited the opposite trend. Therefore, the correlation in deciduous trees appears to be an inherent characteristic of each species rather than a result of porous type.

Full Article

Relationship Between Wood Specific Gravity and Average Annual Ring Width of 15 Korean Wood Species

Kug-Bo Shim,^a Min-Soon Park ,^b Yonggun Park ,^c Chul-Ki Kim ,^c and Hyun Mi Lee , ^c,*

The correlation between specific gravity and average annual ring width was studied for 15 major Korean tree species. In coniferous trees, species with narrower rings exhibited higher specific gravity, with strong correlations observed in Pinus densiflora (Gangwon), Larix kaempferi, and Pinus rigida. In deciduous trees, the correlation between specific gravity and annual ring width did not exhibit a consistent pattern based on the distinction between diffuse-porous and ring-porous species. The correlation of Liriodendron tulipifera (diffuse-porous species) and Quercus mongolica (ring-porous species) showed higher specific gravity with wider rings, whereas other species, such as Betula platyphylla (diffuse-porous species) and Robinia pseudoacacia (ring-porous species) exhibited the opposite trend. Therefore, the correlation in deciduous trees appears to be an inherent characteristic of each species rather than a result of porous type.

DOI: 10.15376/biores.20.4.8439-8455

Keywords: Specific gravity; Average annual ring width; Coniferous trees; Deciduous trees; Ring-Porous; Diffuse-porous

Contact information: a: Department of Wood and Paper Science, College of Agriculture, Life and Environment Science, Chungbuk National University, 1, Chungdae-ro, Seowon-gu, Chengju-si, Chungcheongbuk-do 28644, Korea; b: Department of Forest Product, College of Agriculture, Life and Environment Science, Chungbuk National University, 1, Chungdae-ro, Seowon-gu, Chengju-si, Chungcheongbuk-do 28644, Korea; c: Division of Wood Engineering, Forest Products and Industry Department, National Institute of Forest Science, Seoul 02455, Republic of Korea;

* Corresponding author: leehm2986@korea.kr

INTRODUCTION

The specific gravity of wood is the density of wood expressed relative to the density of water at 4 °C (Gao et al. 2017). The specific gravity of wood is an important indicator of wood quality. It is influenced by various factors such as tree species and growth environment. Within the same species, specific gravity can vary significantly depending on growth region and climate conditions (Jordan et al. 2008). Furthermore, within a single tree, specific gravity fluctuates in the radial direction from the pith to the bark (Pande and Dhiman 2012).

The microstructure of wood also affects its specific gravity. Specific gravity can be influenced by growth ring width, which reflects the growth rate of a tree. Growth rings consist of earlywood and latewood, which form due to seasonal variations in cell growth (Kwon et al. 2020). Earlywood has large lumen areas and thin cell walls, whereas latewood has smaller lumen areas and thicker cell walls (Cartenì et al. 2018). Air-dry density is negatively correlated with cell diameter but positively correlated with cell wall thickness (Chowdhury et al. 2012). Density tends to show a higher correlation with latewood than with earlywood (Pritzkow et al. 2014). The mechanical properties of wood are superior in latewood compared to those in earlywood (Büyüksarı et al. 2017). Additionally, narrower growth rings generally correspond to higher specific gravity and strength (Dahleh et al. 2018). However, in oak species, wider growth rings are associated with a higher proportion of latewood and increased density (Vavrčík and Gryc 2012). These findings suggest that the relationship between growth rings and specific gravity varies depending on the tree species.

Specific gravity is a key factor in evaluating the mechanical properties of wood. Both the modulus of elasticity (MOE) and the modulus of rupture (MOR) exhibit a strong correlation with specific gravity (Cramer et al. 2005; Missanjo and Matsumura 2016). Similarly, compressive strength and specific gravity show a positive correlation (Horáček et al. 2017). Furthermore, specific gravity is proportional to ultrasonic wave velocity (Duong et al. 2019), making it a useful indicator for determining the appropriate applications of a given wood type.

The correlation between average annual ring width and air-dry specific gravity has been investigated in various studies. However, no comprehensive research has been conducted on a wide range of tree species grown in South Korean forests. Therefore, this study aimed to analyze the correlation between average annual ring width and specific gravity in 15 representative coniferous and deciduous tree species with high forest accumulation in South Korea.

EXPERIMENTAL

Tested Wood Species

Among the tree species growing in South Korean forests, 16 species were selected based on their high forest biomass accumulation or potential for wood utilization. These included seven coniferous species (Korean red pine, Korean pine, Japanese larch, pitch pine, Rigitaeda pine, Japanese false cypress, Japanese cedar) and eight deciduous species (tulip tree, East Asian white birch, mossy locust, Sawleaf zelkova, East Asian ash, Oriental cork oak, sawtooth oak, Mongolian oak). The habitat and average age of the selected species are shown in Table 1.

Measurement of Air-dry Specific Gravity and Average Annual Ring Width

A total of 173 to 415 cubic specimens per species, each with a side length of 20 mm, were prepared without visible defects such as knots or cracks, ensuring clearly visible radial and tangential surfaces (Fig. 1). The specimens were collected at 2.4 meters from the ground level along the tree height. Measurement reference lines were drawn to ensure that length measurements were taken at the same positions regardless of changes in the moisture condition of the specimens. These lines were marked in the radial and tangential directions at the center of the transverse surface and in the fiber direction at the center of the tangential surface. For specific gravity measurements, the specimens were oven-dried at 103±2 °C until they reached a constant mass under air-dry conditions.

The condition for achieving constant mass was defined as a mass change rate of less than or equal to 0.2% over a minimum interval of 8 hours. The three-dimensional lengths () and mass ( ) of the specimens were measured under air-dry conditions. The number of growth rings intersecting the radial measurement reference line on the transverse surface of the specimen was counted. The average ring width was calculated by dividing this number by the specimen width. The air-dry specific gravity was calculated in accordance with KS F 2198 (2022).

   (1)

Table 1. Information on Habitats and Average Ages of Selected Wood Species

Fig. 1. Measurement of the number of rings in the cross-section

Data Analysis

The SPSS Statistics software (IBM, USA) was used to analyze the correlation and regression between air-dry specific gravity and average annual ring width. The average annual ring width was entered as the independent variable, while the air-dry specific gravity was set as the dependent variable. Pearson’s correlation coefficient was primarily used for correlation analysis, and statistical significance was determined at a significance level of 0.05. Regression analysis was performed using the linear regression module in SPSS. Residual analysis and diagnostic statistics were conducted to assess the model’s fit, with the significance level set at 0.05. Although R² values are reported, the interpretation of statistical significance relies on the p-values, which are directly related to the regression slopes.

RESULTS AND DISCUSSION

Relationship between the Average Annual Ring Width and Air-dry Specific Gravity of Coniferous trees

Table 2 presents the tested number of coniferous wood specimens, as well as the mean and standard deviation of their average annual ring width and air-dry specific gravity. The correlation coefficients and regression analysis results for the relationship between average annual ring width and air-dry specific gravity are shown in Table 3 and Fig. 2.

Linear regression was conducted with air-dry specific gravity as the dependent variable and average annual ring width as the independent variable. The p-value associated with the slope of the linear regression line indicates whether the relationship between air-dry specific gravity and average annual ring width is statistically significant.

Table 2. Average Annual Ring Width and Air-dry Specific Gravity of Tested Coniferous Species

Table 3. Correlation and Regression Analysis of Coniferous Species

Fig. 2. Regression analysis of average annual ring width and air-dry specific gravity of South Korean coniferous trees

The results indicate that Pinus densiflora Siebold & Zucc., Larix kaempferi (Lamb.) Carriere, and Pinus rigida Mill. exhibited a strong negative correlation between average annual ring width and air-dry specific gravity, whereas Pinus koraiensis Siebold & Zucc., Chamaecyparis obtusa (Siebold & Zucc.) Endl., and Cryptomeria japonica (Thunb. ex L.f.) D.Don showed a weak negative correlation. Among these species, Pinus densiflora (Gangwon region), Larix kaempferi, Pinus rigida, and Pinus rigida × Pinus taeda exhibited statistically significant correlations at the 0.05 significance level. Overall, coniferous species with wider average annual ring widths, indicative of faster growth, tended to have lower air-dry specific gravity.

Previous studies (Auty et al. 2014; Rodriguez et al. 2019; Wang et al. 2022) have also reported a negative correlation between average annual ring width and specific gravity in coniferous species. However, Dahlen et al. (2018) and Wimmer and Downes (2003) concluded that although a negative correlation exists, its strength is insufficient for average annual ring width to serve as a reliable predictor of wood specific gravity. This trend was also observed in Pinus koraiensis Siebold & Zucc., Chamaecyparis obtuse (Siebold & Zucc.) Endl., and Cryptomeria japonica (Thunb. ex L.f.) D.Don in the present study.

Han et al. (2016) reported that a negative correlation was observed between average annual ring width and oven-dry density in Pinus densiflora Siebold & Zucc. In this study, Pinus densiflora Siebold & Zucc. from the Gangwon region exhibited a negative correlation between average annual ring width and air-dry specific gravity, with statistical significance at the 0.05 level. However, Pinus densiflora from the Gyeongbuk region did not show a significant correlation between average annual ring width and air-dry specific gravity.

Kwon et al. (2004) reported no correlation between specific gravity and average annual ring width in Pinus koraiensis. In the study, Pinus koraiensis Siebold & Zucc did not show a significant correlation between air-dry specific gravity and average annual ring width.

Zhang et al. (2023) and Wang et al. (2022) confirmed that as the ring width decreases in Larix kaempferi L., latewood percentage increases, leading to a higher specific gravity. Similarly, in this study, Larix kaempferi L. exhibited a negative correlation between average annual ring width and air-dry specific gravity, which was statistically significant at the 0.05 level.

Pinus rigida Mill. showed a negative correlation between average annual ring width and air-dry specific gravity, with statistical significance at the 0.05 level. Rodriguez et al. (2019) reported a negative correlation between annual ring width and oven-dry specific gravity in Pinus taeda, while Dahlen et al. (2018) confirmed a negative correlation between ring width and specific gravity in Pinus taeda L. In this study, Pinus rigida × Pinus taeda exhibited a negative correlation, which was statistically significant at the 0.05 level. In this experiment, the correlation coefficient value was the highest between Pinus rigida Mill. And Pinus rigida × Pinus taeda.

Todoroki et al. (2015) reported that for Mexican cypress (Cupressus lusitanica Mill.) and Montery cypress (Cupressus macrocarpa Gordon.), juvenile wood shows a decline in wood specific gravity as ring width increases, whereas mature wood shows no correlation between ring width and specific gravity. Similarly, in this study, Chamaecyparis obtusa (Siebold & Zucc.) Endl. showed no significant correlation between air-dry specific gravity and average annual ring width.

Yasuda et al. (2024) observed that in Cryptomeria japonica D. Don, average annual ring width was associated with a distinct increase in specific gravity. However, in this study, which focused on Cryptomeria japonica D. Don grown in Jeju Island, the correlation between average annual ring width and air-dry specific gravity was the lowest among all species examined, indicating that average annual ring width is not a reliable predictor of air-dry specific gravity for this species.

Relationship between the Average Annual Ring Width and Air-dry Specific Gravity of Deciduous Trees

Table 4 presents the number of deciduous wood specimens, as well as the mean and standard deviation of their average annual ring width and air-dry specific gravity. The correlation coefficients and regression analysis results for the relationship between average annual ring width and air-dry specific gravity are shown in Table 5 and Fig. 3.

Among the diffuse-porous species, Betula pendula Roth exhibited a negative correlation between average annual ring width and air-dry specific gravity. Among the ring-porous species, Robinia pseudoacacia L., Zelkova serrata (Thunb.) Makino, Quercus variabilis Blume, Quercus acutissima Carruth., and Quercus mongolica Fisch. ex Ledeb. also showed negative correlations. In contrast, the diffuse-porous species Liriodendron tulipifera L. and the ring-porous species Quercus mongolica Fisch. ex Ledeb. exhibited positive correlations between average annual ring width and air-dry specific gravity.

Table 4. Average Annual Ring Width and Air-dry Specific Gravity of Tested Deciduous Species

Table 5. Correlation and Regression Analysis of Deciduous Species

Linear regression was conducted with air-dry specific gravity as the dependent variable and average annual ring width as the independent variable.

Giagli et al. (2018) reported that both the diffuse-porous Fraxinus excelsior L. (European ash) and the ring-porous Quercus robur L. (English oak) exhibited positive correlations between average annual ring width and oven-dry density. However, Romagnoli et al. (2014) found that Castanea sativa (European chestnut), a ring-porous species, exhibited a negative correlation between ring width and specific gravity, although this relationship varied by region. Additionally, Bouriaud et al. (2004) reported that Fagus sylvatica L. (European beech), a diffuse-porous species, exhibited a negative correlation between ring width and specific gravity. These findings suggest that the relationship between average annual ring width and air-dry specific gravity in deciduous species does not differ significantly between ring-porous and diffuse-porous wood types.

The correlation between average annual ring width and air-dry specific gravity was statistically significant at a 0.05 significance level for Betula pendula Roth, Robinia pseudoacacia L., Quercus mongolica Fisch. ex Ledeb., Quercus variabilis Blum, and Quercus acutissima Carruth. However, for Liriodendron tulipifera L. and Zelkova serrata(Thumb.) Makino, the correlation was not statistically significant at the 0.05 significance level.

The diffuse-porous Liriodendron tulipifera L. did not exhibit a significant correlation between average annual ring width and air-dry specific gravity. The diffuse-porous Betula pendula Roth exhibited a negative correlation, which was statistically significant at the 0.05 level. Jones et al. (2024) reported that for Betula pendula Roth and Betula pubescens Ehrh., average annual ring width were associated with lower wood specific gravity.

The ring-porous Robinia pseudoacacia L. exhibited a negative correlation. Adamopoulos et al. (2010) reported that in Robinia pseudoacacia L. (black locust), average annual ring width were associated with higher latewood percentage, leading to increased specific gravity. However, they also found that the correlation between average annual ring width and specific gravity varied significantly across different regions in Europe. This suggests that the relationship between average annual ring width and air-dry specific gravity in Robinia pseudoacacia L. may differ depending on the growth region.

The ring-porous Zelkova serrata (Thumb.) Makino did not show a statistically significant at the 0.05 level. The ring-porous Fraxinus excelsior L. exhibited a negative correlation and was statistically significant at the 0.05 level. However, Giagli et al. (2018) reported that Fraxinus excelsior L. exhibited a positive correlation between ring width and oven-dry density.

Among the ring-porous oak species, Quercus variabilis Blume exhibited a negative correlation between average annual ring width and air-dry specific gravity, which was statistically significant at the 0.05 level. Similarly, Quercus acutissima Carruth. exhibited a negative correlation with significance at the 0.05 level. However, Quercus mongolica Fisch. ex Ledeb. exhibited a positive correlation, which was statistically significant at the 0.05 level. Giagli et al. (2018) reported that Quercus robur (English oak) in the Czech Republic had a low correlation between average annual ring width and specific gravity. Furthermore, Knapic et al. (2007) concluded that Quercus suber (cork oak) did not exhibit a relationship between average annual ring width and specific gravity. These findings suggest that the correlation between average annual ring width and air-dry specific gravity in oak species can be either positive or negative and may vary depending on species and geographic region.

Similar to coniferous species, the relationship between average annual ring width and air-dry specific gravity in deciduous species varies by species, and in some cases, this relationship is not well-defined.

Fig. 3. Regression analysis of average annual ring width and air dry specific gravity of deciduous trees

CONCLUSIONS

1. In coniferous trees, specimens with smaller average annual ring widths tended to have higher specific gravity. However, species that exhibited a strong correlation between average annual ring width and air-dry specific gravity included Pinus densiflora Siebold & Zucc. (Gangwon region), Larix kaempferi (Lamb.) Carrière, Pinus rigida Mill., and Pinus rigida Mill. × Pinus taeda L. In contrast, Pinus koraiensis Siebold & Zucc., Chamaecyparis obtusa (Siebold & Zucc.) Endl., Cryptomeria japonica (Thunb. ex L.f.) D.Don, and Pinus densiflora Siebold & Zucc. (Gyeongbuk region) exhibited a weaker correlation. Among coniferous plantation species, both Pinus rigida Mill. and the hybrid Pinus rigida Mill. × Pinus taeda L. exhibited a strong correlation between air-dry specific gravity and average annual ring width. This indicates that managed growth conditions can significantly influence the relationship between specific gravity and ring width, likely by affecting wood formation processes and the balance between earlywood and latewood production.

2. Among deciduous species, the diffuse-porous Liriodendron tulipifera L. and the ring-porous Quercus mongolica Fisch. ex Ledeb. exhibited a positive correlation, indicating that specimens with larger average annual ring widths tended to have higher air-dry specific gravity. In contrast, the diffuse-porous Betula pendula Roth and the ring-porous Robinia pseudoacacia L., Zelkova serrata (Thunb.) Makino, Fraxinus rhynchophylla Hance, Quercus variabilis Blume, and Quercus acutissima Carruth. exhibited a negative correlation, where smaller average annual ring widths were associated with higher air-dry specific gravity. Among these species, Robinia pseudoacacia L., Quercus mongolica Fisch. ex Ledeb., Betula pendula Roth, and Fraxinus rhynchophylla Hance exhibited a very strong correlation, whereas Quercus variabilis and Quercus acutissima showed a strong correlation. However, Liriodendron tulipifera L. and Zelkova serrata (Thunb.) Makino were found to be unsuitable for evaluating air-dry specific gravity based on average annual ring width. Among diffuse-porous species, Liriodendron tulipifera L. did not exhibit a significant correlation. In contrast, Betula pendula Roth showed a significant negative correlation at the 0.05 level. For ring-porous species, Robinia pseudoacacia L., Fraxinus rhynchophylla Hance, Quercus variabilis Blume, and Quercus acutissima Carruth. all demonstrated statistically significant negative correlations at the 0.05 level. Quercus mongolica Fisch. ex Ledeb. displayed a significant positive correlation at the same significance level. Zelkova serrata (Thumb.) Makino did not show a significant correlation.

3. Excluding Liriodendron tulipifera L. and Quercus mongolica Fisch. ex Ledeb., temperate-zone coniferous and broadleaf species in South Korea generally exhibited a trend in which smaller average annual ring widths corresponded to higher air-dry specific gravity. These results suggest that the average annual ring width of temperate-zone coniferous and deciduous species can serve as a reference for evaluating air-dry specific gravity.

ACKNOWLEDGMENTS

This research was performed with the support of the National Institute of Forest Science (Assignment Number: FP0100-2021-01-2025)

REFERENCES CITED

Adamopoulos, S., Chavenetidou, M., Passialis, C., and Voulgaridis, E. (2010). “Effect of cambium age and ring width on density and fibre length of black locust and chestnut wood,” Wood Research 55(3), 25-36.

Adamopoulos, S., Passialis, C., and Voulgaridis, E. (2010). “Ring width, latewood proportion and density relationships in black locust wood of different origins and clones,” IAWA Journal 31(2), 169-178. DOI: 10.1163/22941932-90000014

Auty, D., Achim, A., Macdonald, E., Cameron, A. D., and Gardiner, B. A. (2014). “Models for predicting wood density variation in Scots pine,” Forestry: An International Journal of Forest Research 87(3), 449-458. DOI: 10.1093/forestry/cpu005

Bouriaud, O., Bréda, N., Le Moguedec, G., and Nepveu, G. (2004). “Modelling variability of wood density in beech as affected by ring age, radial growth and climate,” Trees 18(3), 264-276. DOI: 10.1007/s00468-003-0303-x

Büyüksarı, Ü., As, N., and Dündar, T. (2017). “Mechanical properties of earlywood and latewood sections of Scots pine wood,” BioResources 12(2), 4004-4012. DOI: 10.15376/biores.12.2.4004-4012

Cartenì, F., Deslauriers, A., Rossi, S., Morin, H., De Micco, V., Mazzoleni, S., and Giannino, F. (2018). “The physiological mechanisms behind the earlywood-to-latewood transition: A process-based modeling approach,” Frontiers in Plant Science 9, article 1053. DOI: 10.3389/fpls.2018.01053

Chowdhury, M., Q., Ishiguri, F., Hiraiwa, T., Matsumoto, K., Takashima, Y., Iizuka, K., Yokota, S., and Yoshizawa, N. (2012). “Variation in anatomical properties and correlations with wood density and compressive strength in Casuarina equisetifolia growing in Bangladesh,” Australian Forestry 75(2), 95-99. DOI: 10.1080/00049158.2012.10676390

Cramer, S., Kretschmann, D., Lakes, R., and Schmidt, T. (2005). “Earlywood and latewood elastic properties in loblolly pine,” Holzforschung 59, 531-538. DOI: 10.1515/HF.2005.088

Dahlen, J., Auty, D., and Eberhardt, T. L. (2018). “Models for predicting specific gravity and ring width for loblolly pine from intensively managed plantations, and implications for wood utilization,” Forests 9(60), article 292. DOI: 10.3390/f9060292

Duong, A. V., Masegawa. M., and Matsumura. J. (2019). “The relations of fiber length, wood density, and compressive strength to ultrasonic wave velocity within stem of Melia azedarach,” Journal of the Indian Academy of Wood Science 16, 1-8. DOI: 10.1007/s13196-018-0227-0

Gao, S., Wang, X., Wiemann, M. C., Brashaw, B. K., Ross, R. J., and Wang, L. (2017). “A critical analysis of methods for rapid and nondestructive determination of wood density in standing trees,” Annals of Forest Science 74, 1-13. DOI: 10.1007/s13595-017-0623-4

Giagli, K., Baar, J., Fajstavr, M., Gryc, V., and Vavrčík, H. (2018). “Tree-ring width and variation of wood density in Fraxinus excelsior L. and Quercus robur L. growing in floodplain forests,” BioResources 13(1), 804-819. DOI: 10.15376/biores.13.1.804-819

Han, Y. J., Lee, H. M., and Eom, C. D. (2016). “Physical and mechanical properties of Korean red pine wood from different growth sites and correlations between them,” J. Korean Wood Sci. Technol. 44(5), 695-704. DOI: 10.5658/WOOD.2016.44.5.695

Horáček, P., Fajstavr, M., and Stojanović, M. (2018). “The variability of wood density and compression strength of Norway spruce (Picea abies/L./Karst.) within the stem. Beskydy 10(1-2), 17-26. DOI: 10.11118/beskyd201710010017

Jones, G., Ulan, M., Liziniewicz, M., Lindeberg, J., and Adamopoulos, S. (2024). “Relating estimates of wood properties of birch to stem form, age and species,” Journal of Forestry Research 35(1), 14. DOI: 10.1007/s11676-023-01669-4

Jordan, L., Clark, A., Schimleck, L. R., Hall, D. B., and Daniels, R. F. (2008). “Regional variation in wood specific gravity of planted loblolly pine in the United States,” Canadian Journal of Forest Research 38(4), 698-710. DOI: 10.1139/X07-158

Knapic, S., Louzada, J. L., Leal, S., and Pereira, H. (2007). “Radial variation of wood density components and ring width in cork oak trees,” Annals of Forest Science 64(2), 211-218. DOI: 10.1051/forest:2006105

KS F 2198 (2022). “Determination of density and specific gravity of wood,” Korean Standards Association, Seoul, Korea.

KS F 2202 (2022). “Determination of average width of annual rings for wood,” Korean Standards Association, Seoul, Korea.

Kwon, O. K., Kim, N. H., Kim, J. S., Seo, J. W., and Chung, Y. J. (2020). Wood Anatomy, The Korean Society of Wood Science and Technology, Seoul, South Korea.

Kwon, S. M., Hwang, W. J., Kwon, G. J., and Kim, N. H. (2004). “Wood quality of Pinus koraiensis and Larix kaempferi,” Journal of Forest and Environmental Science 20, 170-181.

Missanjo, E., and Matsumura, J. (2016). “Wood density and mechanical properties of Pinus kesiya Royle ex Gordon in Malawi,” Forests 7(7), article 135. DOI: 10.3390/f7070135

Ortega Rodriguez, D. R., and Tomazello-Filho, M. (2019). “Clues to wood quality and production from analyzing ring width and density variabilities of fertilized Pinus taeda trees,” New Forests 50(5), 821-843. DOI: 10.1007/s11056-018-09702-9

Pande, P. K., and Dhiman, R. C. (2012). “Variations in wood anatomical properties and specific gravity of half sib progenies of Populus deltoides,” Journal of Forestry Research 23, 491-496. DOI: 10.1007/s11676-012-0289-6

Pritzkow, C., Heinrich, I., Grudd, H., and Helle, G. (2014). “Relationship between wood anatomy. tree-ring widths and wood density of Pinus sylvestris L. and climate at high latitudes in northern Sweden,” Dendrochronologia 32(4), 295-302. DOI: 10.1016/j.dendro.2014.07.003

Romagnoli, M., Cavalli, D., and Spina, S. (2014). “Wood quality of chestnut: Relationship between ring width, specific gravity, and physical and mechanical properties,” BioResources 9(1), 1132-1147. DOI: 10.15376/biores.9.1.1132-1147

Todoroki, C. L., Low, C. B., McKenzie, H. M., and Gea, L. D. (2015). “Radial variation in selected wood properties of three cypress taxa,” New Zealand Journal of Forestry Science 45, 1-14. DOI: 10.1186/s40490-015-0049-4

Van Duong, D., Hasegawa, M., and Matsumura, J. (2019). “The relations of fiber length, wood density, and compressive strength to ultrasonic wave velocity within stem of Melia azedarach,” Journal of the Indian Academy of Wood Science 16, 1-8. DOI: 10.1007/s13196-018-0227-0

Vavrčík, H., and Gryc, V. (2012). “Analysis of the annual ring structure and wood density relations in English oak and sessile oak,” Wood Research 57(4), 573-580.

Wang, S., Chen, D., Chu, J., and Jiang, J. (2022). “Effect of growth ring width and latewood content on selected physical and mechanical properties of plantation Japanese larch wood,” Forests 13(5), article 797. DOI: 10.3390/f13050797

Wimmer, R., and Downes, G. M. (2003). “Temporal variation of the ring width–wood density relationship in Norway spruce grown under two levels of anthropogenic disturbance,” IAWA Journal 24(1), 53-61. DOI: 10.1163/22941932-90000320

Yasuda, Y., Iki, T., Takashima, Y., Takahashi, M., Hiraoka, Y., and Mishima, K. (2024). Inheritance of growth ring components and the possibility of early selection for higher wood density in Japanese cedar (Cryptomeria japonica D. Don),” Annals of Forest Science 81(1), 5. DOI: 10.1186/s13595-023-01212-9

Zhang, F., Wang, S., Jiang, J., Chen, D., and Zhou, H. (2023). “Effects of growth ring width, height from tree base, and loading direction on transverse compression of plantation Japanese larch wood,” Forests 14(7), article 1451. DOI: 10.3390/f14071451

Article submitted: March 24, 2025; Peer review completed: May 17, 2025; Revised version received: May 22, 2025; Accepted: July 22, 2025; Published: August 4, 2025.

DOI: 10.15376/biores.20.4.8439-8455