Abstract
The objective of this study was to measure compressive strength properties perpendicular to the fiber of green Eucalyptus nitens specimens. The data was measured for clear 50 × 50 × 150 mm specimens obtained from 17-year-old trees that were harvested at the Ñuble region in Chile, and the data comprised modulus of elasticity (Ec), compressive strength (ƒc), basic density, initial moisture content, and some anatomical characteristics of the wood. The experimental design emphasized the influence of the radial position of the wood within the logs (defined as inner-wood, middle-wood, and outer-wood) on the measurements, and the results showed that the modulus of elasticity, compressive strength, and the basic density all increased from core to bark. The compressive strength of outer-wood showed a strong and positive relation with the basic density. Cell wall thickness and wall cell area showed a significant positive correlation with compressive strength.
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Variation of Perpendicular Compressive Strength Properties Related to Anatomical Structure and Density in Eucalyptus nitens Green Specimens
Natalia Pérez-Peña,a Diego M. Elustondo,b Luis Valenzuela,c and Rubén A. Ananías a,d,*
The objective of this study was to measure compressive strength properties perpendicular to the fiber of green Eucalyptus nitens specimens. The data was measured for clear 50 × 50 × 150 mm specimens obtained from 17-year-old trees that were harvested at the Ñuble region in Chile, and the data comprised modulus of elasticity (Ec), compressive strength (ƒc), basic density, initial moisture content, and some anatomical characteristics of the wood. The experimental design emphasized the influence of the radial position of the wood within the logs (defined as inner-wood, middle-wood, and outer-wood) on the measurements, and the results showed that the modulus of elasticity, compressive strength, and the basic density all increased from core to bark. The compressive strength of outer-wood showed a strong and positive relation with the basic density. Cell wall thickness and wall cell area showed a significant positive correlation with compressive strength.
Keywords: Basic density; Drying stresses; Compressive strength; Wood collapse
Contact information: a: Research Laboratory of Wood Drying and Heat Treatments, University of Bío-Bío, Concepción, Chile; b: Scion, Rotorua, New Zealand; c: Department of Forest Management and Environment, Faculty of Forestry, University of Concepción, Concepción, Chile; d: Department of Wood Engineering, Faculty of Engineering, University of Bío-Bío, Concepción, Chile;
* Corresponding author: ananias@ubiobio.cl
INTRODUCTION
Eucalyptus nitens species were introduced in Chile in the 1960s, and there are currently 270,000 hectares of plantation corresponding to approximately 12% of the total plantation area (Gysling et al. 2019). This species was originally imported to supply pulp and paper for the wood industry, but due to its natural advantages, such as fast growth and resistance to cold weather, there are currently high expectations for finding more commercial applications in the solid wood sector. There are currently scientific and technological efforts in academia and the wood industry in Chile and around the world that focus on the physic-mechanical characterization of this species towards its utilization as solid wood products (Yang and Waugh 1996; Rebolledo et al. 2013; Salvo et al. 2017).
Measurements of physical-mechanical properties are important to assess whether the characteristics of the wood materials are suitable for structural applications. The basic density is particularly important because it highly affects the manufacturing processes and provides in general a good estimation of the mechanical strength (Prado and Barros 1989). Likewise, some authors affirm that, besides the density, the compressive behavior of wood is strongly dependent on its anatomical characteristics such as cell length, cell wall thickness, fiber diameter, and microfibril angle (MFA) (Alexiou 1994; Evans and Ilic 2001; Müller et al. 2003). According to Evans and Ilic (2001), there is a strong relationship between the MFA and the modulus of elasticity (E) of Eucalyptus wood, and they point out that the MFA is the main factor that affects the E of the wood. Evans et al. (2000), who measured the MFA in 15-year-old Eucalyptus nitens, reported that MFA was between 20° and 30° near the pith and 10° near the bark. This was also reported by McKenzie et al. (2003), who obtained that MFA decreased from the pith zone to reach lowest values at the bark. Also, they reported that the MFA showed a moderate negative correlation with E, and was a weakly and negatively correlated with cell wall thickness.
Moreover, there are many studies with E. nitens in which the basic density is measured in the radial and longitudinal directions with reporting values from 400 to 550 kg/m3 (Downes et al. 1997; Evans et al. 2000; Shelbourne et al. 2002; Leandro et al. 2008). McKimm (1985) studied the variation of properties in 8.5-year-old E. nitens and concluded that in general the strength properties are lower than in wood from adult E. nitens trees, but the values are comparable with those of Pinus radiata, showing the wood materials would be suitable for structural use. This was also confirmed by Yang and Waugh’s research (1996), which considered the properties of 15- to 29-year-old plantation trees and the results suggest that wood from that type of plantation with those properties and characteristics can be used for producing sawn lumber for structural applications.
However, one of the problems for producing solid wood from E. nitens is the drying process, which is difficult because the wood tends to develop high internal stresses during drying (Pérez et al. 2018) and collapse (Ananías et al. 2009, 2014). This can greatly reduce the quality of the dried product to a level that has no practical commercial value. In general terms, collapse is an abnormal shrinkage that occurs above the fiber saturation point, and it is caused by capillary forces that arise as the free water is eliminated (Chafe et al. 1992). When these forces exceed the compressive strength of the cell walls, the flattening of cell can be produced (Yuniarti et al. 2015; Bond and Espinoza 2016). Pérez et al. (2018) measured the compression stresses as high as 9 MPa during the drying of E. nitens samples, which could explain the tendency to collapse and the development of internal checking. In this line, the stronger wood in compression perpendicular to the fiber would less prone to collapse (Chafe et al. 1992).
For this reason, the authors postulated in this study that it is important to know the perpendicular compressive strength variation and correlate with some anatomical characteristics and density, which helps to estimate the effect of these properties on the magnitude of the stresses that would cause cellular compression and collapse during drying.
EXPERIMENTAL
Materials
The testing material was obtained from 17-year-old trees that came from a plantation in Yungay, Region of Ñuble, Chile; and the samples comprised 9 trees from 3 different families of Eucalyptus nitens. One disk was cut from each tree at a height of 1.3 m, and each disk was divided into three zones based on the radial distance to the pith (Fig. 1). These areas were defined as inner-wood, referring to wood close to the pith, outer-wood, referring to wood close to the bark, and middle-wood, referring to the area between the other two. Three replicates were cut from each wood zone with 50 mm × 50 mm width and thickness in the disk radial and tangential directions, and 160 mm length in the longitudinal direction. This generated a total of 9 trees by 3 zones by 3 replicates, equal to 81 samples. The disks were kept under controlled environment at -10 °C, for 4 to 6 weeks. Specimens prepared for compression, density, and moisture content tests were kept under water and the tests were performed immediately after saturation.
Fig. 1. Extraction of the logs at 1.3 m and specimens on the radial distance to the pith of each disk
Methods
Mechanical test
The compression tests were performed in compliance with the NCh 974 (INN 1986) standard. A universal testing machine (Metrotec 200kN; TechLab Systems S.L., Lezo, Spain) with a head speed of 0.3 mm/min was used. For testing purposes, the probe dimensions were reduced to the standard size of 50 × 50 × 150 mm3, and the mechanical properties in the direction perpendicular to the sample were calculated as the average between the values measured in the radial and tangential directions. The compressive strength (ƒc) and modulus of elasticity (Ec) were calculated based on the load versus deformation curve, according to NCh 974 (INN 1986).
Determination of basic density and moisture content
Two 25 × 25 × 25 mm3 cubes for measuring basic density and moisture content were immediately cut from the opposite extremes of each probe, after measuring the mechanical properties. The basic density was determined in compliance with NCh 176/2 (INN 1988). Similarly, moisture content was determined through the oven-dry method in compliance with the NCh 176/1 standard (INN 1984).
Evaluation of anatomical characteristics
The anatomical characteristics of vessels (diameter and area) and fibers (wall thickness, diameter, and area) were measured as described by Salvo et al. (2017), in which two specimens cubes of 25 mm × 25 mm × 25 mm were prepared from each radial position. Ten slices of 20 µm thickness of each anatomical orientation of wood (transversal, radial, and tangential) of each cube were obtained for microscopic observations and image captures. The analysis of images of anatomical characteristics was realized using commercial software Wincell Pro (Regent Instruments Inc., v.2011a, Québec, Canada) and Motic Images Plus 3.0 (Motic Instruments Inc., British Columbia, Canada).
Data analysis
Normality of the data distribution and homogeneity of the variance were tested with the Kolmogorov-Smirnov and Barlett methods, respectively, and the comparison between the data sets was performed through an analysis of variance (ANOVA), and the Tukey test with a 95% confidence level. The relationships between compressive strength and density, as well as some anatomical properties, were investigated by Pearson’s correlation analysis. The computer software Statistica (Statsoft Inc., v10.0, Tulsa, OK, USA) was used to perform the statistical analysis.
RESULTS AND DISCUSSION
Table 1 reports the average and standard deviation values measured for basic density, modulus of elasticity, and compressive strength as a function of the type of wood based on the position of the wood in the radial direction. The table also reports the p-values from the ANOVA tests applied to find statistically significant differences between families, trees, and types of wood. The ANOVA test indicated that those three biological factors had statistically significant effects for the wood mechanical properties (p < 0.05), with the exception of the compressive strength, which was not significantly affected by the family.
Table 1. Average and Standard Deviation Values of Basic Density, Modulus of Elasticity, and Compressive Strength for E. nitens as a Function of the Radial Position
The average basic density measured for E. nitens was 473.7 kg/m3, with minimum and maximum values of 365.2 kg/m3 and 599.9 kg/m3, respectively, and a standard deviation of 48.9. These results are in agreement with data for 8- to 14-year-old E. nitens trees reported in the literature (Purnell 1988; Chafe 1990; Chauhan and Walker 2004; Leandro et al. 2008). Furthermore, Kibblewhite et al. (2004) reported almost the same basic density of 473 kg/m3 and also Derikvand et al. (2018) reported a close average density of 480 kg/m3 for 15- and 16-year-old E. nitens trees, respectively.
Fig. 2. Variation of (a) basic density and (b) moisture content of E. nitens as a function of the radial position
Table 1 indicates that there were no statistically significant differences between inner-wood and middle-wood, but the differences were significant with respect to outer-wood. Figure 2 shows the basic density, moisture content average, and the range of variation as a function of the wood position in the radial direction. It was observed that the basic density tended to increase from pith to bark (Fig. 2a), which is in agreement with other published literature data (Lausberg et al. 1995; Downes et al. 1997; Evans et al. 2000) as well as the common trend typically reported in the literature for the Eucalyptus genus (Raymond and Muneri 2001; McKinley et al. 2002; Wessels et al. 2016).
Similarly, moisture content did not show statistically significant differences between the inner-wood and the middle-wood (Fig. 2b), but only with respect to outer-wood. However, for moisture content, the average moisture content decreased from pith to bark, similarly to what has been reported by Lausberg et al. (1995), who measured moisture content values in E. nitens varying from 137% to 123% from pith to bark.
The average modulus of elasticity in compression perpendicular to the fiber for the E. nitens was 2.3 GPa, with minimum and maximum values of 1.1 and 3.6 GPa, respectively, and a standard deviation of 0.5. These values are much higher than those reported in literature for other older species of the Eucalyptus genus (Alexiou 1994; Nogueira et al. 2018a,b). Table 1 shows that there were statistically significant differences between inner-wood and outer-wood, but these differences were not significant as the differences between inner-wood and middle-wood, and between middle-wood and outer-wood. Additionally, the general trend was that Ec increased from pith to bark, with values from 2.1 GPa to 2.5 GPa from inner-wood to outer-wood, and which represents an increase of approximately 20%. This can be explained by the fact that the basic density increases in the outer-wood by approximately 12%, compared to the inner-wood.
The measured compressive strength ranged from 2.6 to 5.6 MPa, with an average of 4.2 MPa. These results are comparable with similar values reported in the literature for the same species (McKimm 1985) and for other species of the same Eucalyptus genus (Nogueira et al. 2018a). On the other hand, the values measured in this study were similar to those reported by Lobão et al. (2004) for Eucalyptus grandis (4.9 MPa), and the results obtained by Awan et al. (2012) for Eucalyptus camaldulensis (5.5 MPa). However, these results were obtained in mechanical tests conducted in dry conditions. The trend was that fc increased from pith to bark, with values from 4.1 MPa to 4.4 MPa from inner-wood to outer-wood. The major value in outer-wood can be explained due to a higher value of density and a lower value of MFA (Evans et al. 2000).
One important observation that can be drawn from this study is that the compressive strength perpendicular to the fiber direction of Eucalyptus nitens may not be enough to withstand the internal stresses that can induce collapse during drying. That is based on the drying stresses calculated by Pérez et al. (2018), who reported values in the range of 8 to 9 MPa. This is important for the processing of E. nitens into added value solid wood materials because this species is prone to collapse during drying. Thus, having data about the resistance to perpendicular compressive stress during drying will help researchers to develop drying schedules that can minimize the risk of collapse. Examples of strategies to help reduce the collapse would include by reducing the magnitude of drying stresses by applying lower temperatures, an intermittent drying process, or by using radio-frequency vacuum drying technology (Yang et al. 2014; Ananías et al. 2018).
Figure 3 shows the modulus of elasticity (Fig. 3a), the compressive strength averages (Fig. 3b), and ranges of values measured for E. nitens as a function of the radial position. As with the Ec results, the general trend was also that fc increased from pith to bark, and the difference between inner-wood and outer-wood was statistically significant at the 0.05 level.
Fig. 3. Compressive properties perpendicular to the fiber of E. nitens as a function of the radial position: (a) modulus of elasticity and (b) compressive strength
Table 2 shows the average measured anatomical properties grouped by the radial position and the p-value of the ANOVA test.
Table 2. Summary of Anatomical Properties of Eucalyptus nitens
The mean values of radial and tangential cell wall thickness were 2.3 and 2.5 µm, respectively, with the highest values in the middle-wood. These values were similar to the values measured by Leandro et al. (2008) and Salvo et al. (2017), and higher than those reported by McKenzie et al. (2003) and Kibblewhite et al. (2004). This difference can be explained by various factors, such as the presence of juvenile wood, provenance and site, and the high variability within and between trees in the Eucalyptus nitens families (Salvo et al. 2017). The radial and tangential fiber diameters were 11.5 and 14.2 µm, respectively, and there was no significant difference among the wood types. In contrast, the cell wall area increased from 149.3 to 151.9 µm2, although the difference between the types of wood was not statistically significant.
For vessel diameter, there was a significant difference between the three types of wood. In both cases, the mean value increased from inner-wood to outer-wood. Additionally, the variation between radial and tangential values was statistically significant at the 0.05 level. These results were in agreement with previous studies (McKenzie et al. 2003; Leandro et al. 2008; Salvo et al. 2017). Similarly, the value of vessel area increased from 15,891 µm2 in core-wood to 40,000 µm2 in outer-wood. These values were higher than those measured by Hudson et al. (1998), who reported values that increased from 500 µm2 near the pith to approximately 35,000 µm2 in the near bark zone.
The results obtained with the ANOVA indicated that the radial position only had an effect in the vessels diameter and vessel area. In both properties, significant differences were obtained between the three types of wood.
Also, the width: thickness ratio were calculated, which represent the fiber collapse potential (Kibblewhite et al. 1998). The average values obtained were 1.25, 1.24, and 1.22 for respectively inner-wood, middle-wood, and outer-wood, and showing a small decreasing trend from pith to bark. This could therefore be expected and be related with a high compressive strength near to bark.
In contrast, the relationships between compressive strength with basic density and anatomical properties were not statistically significant in inner-wood and middle-wood. However, significant relationships were found in outer-wood. The relationships between compressive strength with basic density and anatomical properties of outer-wood are shown in Fig 4. The basic density was strongly positively correlated with compressive strength, with r = 0.93 (p < 0.05). Cell wall thickness and wall cell area showed a significant positive correlation with ƒc, with r values of 0.66 and 0.65, respectively.
Fig. 4. Relationship between compressive strength and (a) basic density, (b) cell wall thickness, and (c) wall cell area
CONCLUSIONS
The objective of this study was to measure the modulus of elasticity and compressive strength perpendicular to the fiber, and then to relate it with some anatomical features and the density of green Eucalyptus nitens. The following are the conclusions that were obtained:
- The compressive strength properties increased from pith to bark and showed significant differences between the inner-wood and outer-wood.
- The modulus of elasticity ranged between 1.1 and 3.6 GPa with an average value of 2.3 GPa. The average compressive strength was 4.2 MPa with values of 4.1, 4.2, and 4.4 MPa for inner-, middle-, and outer-wood, respectively.
- The compressive strength showed a strong and significant relation with basic density of outer-wood, and significant positive relation with cell wall thickness and cell wall area.
ACKNOWLEDGMENTS
The authors appreciate the financial support of the National Commission of Scientific & Technological Research (Conicyt) of Chile (Fondecyt 1160812).
REFERENCES CITED
Alexiou, P. N. (1994). “Elastic properties of Eucalyptus pilularis Sm. perpendicular to the grain. II. In compression,” Holzforschung 48, 55-60.
Ananías, R. A., Díaz, C., and Leandro, L. (2009). “Estudio preliminar de la contracción y el colapso en Eucalyptus nitens [Preliminary study of shrinkage and collapse in Eucalyptus nitens],” Maderas: Ciencia y Tecnologia 11(3), 251-262. DOI: 10.4067/S0718-221X2009000300007
Ananías, R. A., Sepúlveda-Villarroel, V., Pérez-Peña, N., Leandro-Zuñiga, L., Salvo, L. P., Salinas, C., Cloutier, A., and Elustondo, D. (2014). “Collapse of Eucalyptus nitens wood after drying depending on the radial location within the stem,” Drying Technology 32(14), 1699-1705. DOI: 10.1080/07373937.2014.924132
Ananías, R. A., Sepúlveda, V., Cancino, F., Salvo, L., Torres, J., Pérez, N., Castillo, D., and Salinas, C. (2018). “RFV drying of Eucalyptus nitens juvenile wood,” in IAWS Annual Meeting 2018, Biosustainable Materials, Guadalajara, Mexico.
Awan, A. R., Chughtai, M. I., Ashraf, M. Y., Mahmood, K., Rizwan, M., Akhtar, M., Siddiqui, M. T. H., and Khan, R. A. (2012). “Comparison for physico-mechanical properties of farm-grown Eucalyptus camaldulensis Dehn. with conventional timbers,” Pakistan Journal of Botany 44(6), 2067-2070.
Bond, G., and Espinoza, H. (2016). “A decade of improved lumber drying technology,” Current Forestry Reports 2, 106-118. DOI: 10.1007/s40725-016-0034-z
Chafe, S. C. (1990). “Relationships among growth strain, density and strength properties in two species of Eucalyptus,” Holzforschung 44(6), 431-437. DOI: 10.1515/hfsg.1990.44.6.431
Chafe, S. C., Barnacle, J. E., Hunter, A. J., Ilic, J., Northway, R. L., and Rozsa, A. N. (1992). Collapse: An introduction, CSIRO Division of Forest Products, Melbourne, Australia.
Chauhan, S. S., and Walker, J. (2004). “Relationships between longitudinal growth strain and some wood properties in Eucalyptus nitens,” Australian Forestry 67(4), 254-260. DOI: 10.1080/00049158.2004.10674943
Derikvand, M., Kotlarewsky, N., Lee, M., Jiao, H., Chan, A., and Nolan, G. (2018). “Visual stress grading of fibre-managed plantation Eucalypt timber for structural building applications,” Construction and Building Materials 167, 688-699. DOI: 10.1016/j.conbuildmat.2018.02.090
Downes, G. M., Hudson, I. L., Raymond, C. A., Dean, G. H., Michell, A. J., Schimleck, L. R., Evans, R., and Muneri, A. (1997). Sampling Plantation Eucalypts for Wood and Fibre, CSIRO Publishing, Collingwood, Australia.
Evans, R., Stringer, S. L., and Kibblewhite, R. P. (2000). “Variation of microfibril angle, density and fibre orientation in twenty-nine Eucalyptus nitens trees,” Appita Journal 53(6), 450-457.
Evans, R., and Ilic, J. (2001). “Rapid prediction of wood stiffness from microfibril angle and density,” Forest Products Journal 51(3), 53-57.
Gysling, A. J., Álvarez, V. D. C., Soto, D. A., Pardo, E. J., Poblete, P. A., and Khaler, C. (2019). Anuario Forestal 2019 [Chilean Statistical Yearbook of Forestry 2019], Instituto Forestal [Forestry Institute], Santiago, Chile.
Hudson, I., Wilson, L., and Van Beveren, K. (1998). “Vessel and fibre property variation in Eucalyptus globulus and Eucalyptus nitens: Some preliminary results,” IAWA Journal 19(2), 111-130. DOI: 10.1163/22941932-90001514
INN (1984). “Madera – Parte 1: Determinación de humedad [Wood – Part 1: Moisture determination],” National Institute for Standardization, Santiago, Chile.
INN (1986). “Madera – Determinación de las propiedades mecánicas – Ensayo de compresión perpendicular a las fibras [Wood – Determination of mechanical properties – Compression perpendicular to the fibers test],” National Institute for Standardization, Santiago, Chile.
INN (1988). “Madera – Parte 2: Determinación de la densidad de la madera [Wood – Part 2: Determination of density],” National Institute for Standardization, Santiago, Chile.
Kibblewhite, R. P., Riddell, M. J. C., and Shelbourne, C. J. A. (1998). “Kraft fibre and pulp qualities of 29 trees of New Zealand grown Eucalyptus nitens,” Appita Journal 51(2), 114-121.
Kibblewhite, R. P., Evans, R., Riddell, M. J. C., and Shelbourne, C. J. A. (2004). “Changes in density and wood-fibre properties with height position in 15/16-year-old Eucalyptus nitens and E. fastigata,” Appita Journal 57(3), 240-247.
Lausberg, M. J. F., Gilchrist, K. F., and Skipwith, J. H. (1995). “Wood properties of Eucalyptus nitens grown in New Zealand,” New Zealand Journal of Forestry Science 25(2), 147-163.
Leandro, L. L., Ananías, R. A., Cloutier, A., Díaz-Vaz, J. E., Bermedo, M., Sanhueza, R., and Lasserre, J. P. (2008). “Estudio preliminar de las grietas internas dentro de los anillos de madera inicial y su relación con características de la estructura anatómica y densidad en Eucalyptus nitens [Preliminary study of internal checks within growth-rings and their relationship with anatomical features and density in Eucalyptus nitens],” Interciencia 33(11), 829-834.
Lobão, M. S., Marius, L., Moreira, M. S. S., and Gomes, A. G. (2004). “Caracterização das propriedades físico-mecânicas da madeira de Eucalipto com diferentes densidades [Characterization of physical and mechanical properties of Eucalyptus lumber with different specific gravities],” Revista Árvore 28(6), 889-894. DOI: 10.1590/S0100-67622004000600014
McKimm, R. J. (1985). “Characteristics of the wood of young fast-grown trees of Eucalyptus nitens Maiden with special reference to provenance variation. II. Strength, dimensional stability and preservation characteristics,” Australian Forest Research 15(2), 219-234.
McKinley, R. B., Shelbourne, C. J. A., Low, C. B., Penellum, B., and Kimberley, M. O. (2002). “Wood properties of young Eucalyptus nitens, E. globulus, and E. maidenii in Northland,” New Zealand Journal of Forestry Science 32(3), 334-356.
McKenzie, H. M., Shelbourne, C. J. A., Kimberley, M. O., McKinley, R. B., and Britton, R. A. J. (2003). “Processing young plantation-grown Eucalyptus nitens for solid-wood products. 2: Predicting product quality from tree, increment core, disc, and 1-m billet properties,” New Zealand Journal of Forestry Science 33(1), 79-113.
Müller, U., Gindl, W., and Teischinger, A. (2003). “Effects of cell anatomy on the plastic and elastic behaviour of different wood species loaded perpendicular to grain,” Iawa Journal 24(2), 117-128.
Nogueira, M. C. J. A., Almeida, D., Vasconcelos, J. S., Almeida, T. H., Araújo, V. A., Christoforo, A. L., and Lahr, F. A. R. (2018a). “Properties of Eucalyptus umbra wood for timber structures,” International Journal of Materials Engineering 8(1), 12-15. DOI: 10.5923/j.ijme.20180801.03
Nogueira, M. C. J. A., De Araujo, V. A., Vasconcelos, J. S., Da Cruz, J. N., Vasconcelos, J. C. S., Prataviera, F., Christoforo, A. L., and Lahr, F. A. R. (2018b). “Characterization of Eucalyptus maidenii timber for structural application: Physical and mechanical properties at two moisture conditions,” South-East European Forestry 9(2), 141-146. DOI: 10.15177/seefor.18-1010.15177/seefor.18-10
Pérez-Peña, N., Chávez, C., Salinas, C., and Ananías, R. A. (2018). “Simulation of drying stresses in Eucalyptus nitens wood,” BioResources 13(1), 1413-1424. DOI: 10.15376/biores.13.1.1413-1424
Prado, J. A., and Barros, S. (1989). Eucalyptus: Principios de Silvicultura y Manejo [Eucalyptus: Principles of Forestry and Management], Instituto Forestal, División silvicultura, Corporación de Fomento de la Producción [Forestry Institute, Chilean Economic Development Agency], Santiago, Chile.
Purnell, R. C. (1988). “Variation in wood properties of Eucalyptus nitens in a provenance
trial on the Eastern Transvaal Highveld in South Africa,” South African Forestry Journal 144(1), 10-22. DOI: 10.1080/00382167.1988.9630311
Raymond, C. A., and Muneri, A. (2001). “Nondestructive sampling of Eucalyptus globulus and E. nitens for wood properties. I. Basic density,” Wood Science and Technology 35(1-2), 27-39. DOI: 10.1007/s002260000078
Rebolledo, P., Salvo, L., Contreras, H., Cloutier, A., and Ananías, R. A. (2013). “Variation of internal checks related with anatomical structure and density in Eucalyptus nitens wood,” Wood and Fiber Science 45(3), 279-286.
Salvo, L., Leandro, L., Contreras, H., Cloutier, A., Elustondo, D., and Ananías, R. A. (2017). “Radial variation of density and anatomical features in Eucalyptus nitens trees,” Wood and Fiber Science 49(3), 301-311.
Shelbourne, C. J. A., Nicholas, I. D., McKinley, R. B., Low, C. B., McConnochie, R. M., and Lausberg, M. J. F. (2002). “Wood density and internal checking of young Eucalyptus nitens in New Zealand as affected by site and height up the tree,” New New Zealand Journal of Forestry Science 32(3), 357-385.
Wessels, C. B., Crafford, P. L., Du Toit, B., Grahn, T., Johansson, M., Lundqvist, S. O., Säll, H., and Seifert, T. (2016). “Variation in physical and mechanical properties for three drought tolerant Eucalyptus species grown on the dry west coast of Southern Africa,” European Journal of Wood and Wood Products 74(4), 563-575. DOI: 10.1007/s00107-016-1016-3
Yang, J. L., and Waugh, G. (1996). “Potential of plantation-grown eucalypts for structural sawn products. II. Eucalyptus nitens (Dean & Maiden) Maiden and E. regnans F. Muell,” Australian Forestry 59(2), 99-107. DOI: 10.1080/00049158.1996.10674674
Yang, L., Liu, H., Cai, Y., Hayashi, K., and Wu, Z. (2014). “Effect of drying conditions on the collapse-prone wood of Eucalyptus urophylla,” Bioresources 9(4), 7288-7298.
Yuniarti, K., Ozarska, B., Brodie, G., Harris, G., and Waugh, G. (2015). “Collapse development of Eucalyptus saligna under different drying temperatures,” Journal of Tropical Forest Science 27(4), 462-471.
Article submitted: September 26, 2019; Peer review completed: December 1, 2019; Revised version received: December 13, 2019; Accepted: December 14, 2019; Published: December 18, 2019.
DOI: 10.15376/biores.15.1.987-1000