Wood Stiffness Research Articles

Radial variation in modulus of elasticity, microfibril angle and wood density of veneer logs from plantation-grown Eucalyptus nitens

Radial variation of wood properties affects product recovery from veneer logs. In Eucalyptus nitens , the radial variation in wood density, microfibril angle and modulus of elasticity was described using non-linear models. The timing of radial change was trait-dependent, and the age at which thresholds for structural products were reached differed between sites. Eucalyptus nitens is widely planted in cool temperate regions of the world. While mainly grown for pulpwood, rotary-peeled veneer is becoming important. Threshold levels of wood stiffness are required for using this veneer for structural purposes. Stiffness is determined by wood density and microfibril angle, which improve with tree age. The nature of this radial variation affects the recovery of suitable veneer and profitability of the plantation resource. We model the radial variation of these veneer-critical wood properties and determine whether it varies with growing conditions. We used logs from three 20–22-year-old Tasmanian plantations. Radial variations in wood density, microfibril angle and modulus of elasticity (measuring stiffness) were assessed using SilviScan. Eight linear and non-linear models were examined using cambial age as the independent variable. The increases in wood density and modulus of elasticity with age were modelled by sigmoidal functions and the decrease in microfibril angle modelled by an asymptotic function. The timing of radial change was trait-dependent, and the mean ages at which thresholds for structural products were reached between sites. Radial variation varied among sites and will likely impact the recovery of structural grade veneer from plantations.

Thickness-dependent stiffness of wood: potential mechanisms and implications

Abstract When wood is split or cut along the grain, a reduction in tensile stiffness has been observed. The averaged mechanical properties of wood samples, veneers or splinters therefore change when their thickness is less than about 1 mm. The loss of stiffness increases as the thickness approaches that of a single cell. The mechanism of the effect depends on whether the longitudinal fission plane is between or through the cells. Isolated single cells are a model for fission between cells. Each cell within bulk wood is prevented from twisting by attachment to its neighbours. Separation of adjacent cells lifts this restriction on twisting and facilitates elongation as the cellulose microfibrils reorientate towards the stretching direction. In contrast when the wood is cut or split along the centre of the cells, it appears that co-operative action by the S1, S2 and S3 cell-wall layers in resisting tensile stress may be disrupted. Since much of what is known about the nanoscale mechanism of wood deformation comes from experiments on thin samples, caution is needed in applying this knowledge to structural-sized timber. The loss of stiffness at longitudinal fracture faces may augment the remarkable capacity of wood to resist fracture by deflecting cracks into the axial plane. These observations also point to mechanisms for enhancing toughness that are unique to wood and have biomimetic potential for the design of composite materials.

Effect of final temperature on charcoal stiffness and its correlation with wood density and hardness

Mechanical performance is important for charcoal used in blast furnaces as charcoal layers may support the load of iron ore within blast furnaces without breaking. Pyrolysis temperature influences charcoal quality and its chemical composition; however, the effect of temperature on physical-mechanical properties is still unknown. Thus, the aim of this study was to establish the effect of pyrolysis temperature on the density, stiffness and hardness of charcoal and the correlations among them. Four pyrolysis processes were performed at final temperatures of 300, 450, 600 and 750 °C using wood specimens from nine different tree species. Stiffness of wood and charcoal was determined by ultrasound and dynamic hardness by a portable hardness tester. In short, density, dynamic hardness and stiffness of charcoal tend to decrease with increasing temperature. Pyrolysis at 450 °C decreases charcoal stiffness by approximately 30%, while hardness is reduced from 29 MPa in wood specimens to approximately 3 MPa in charcoal pieces produced from the same specimens. Considering the wood, the highest values of stiffness were presented by the same materials which presented highest density, confirming high positive correlation between wood properties. The correlation between density and stiffness in charcoal is higher than in wood. However, correlation between density and dynamic hardness or stiffness and dynamic hardness is higher for wood than for charcoal. Ultrasound was able to determine differences in stiffness between the materials at different pyrolysis temperatures. These findings are useful to identify the best production temperature for industrial charcoal with adequate mechanical properties.

Influence of the bonding of rebar dowel with adhesive on wood–concrete composite specimens

Ensuring the quality of the connector used in wood–concrete composite systems is a critical factor affecting the performance of the system. The main objective of this research was to study the strength and stiffness of wood–concrete composite specimens with two types of rebar dowel connectors: fixed to the wood (solid timber) using epoxy adhesive and by pre-drilling on smaller diameter holes in the wood (without the use of adhesive). In the composition of the test specimens, rebar dowels of 12·7 mm dia. were used. The strength and stiffness of the connectors were determined by double shear tests, performed on composite specimens. Statistical analysis was used to compare the results obtained and regression models were proposed for estimating the stiffness parameters of the connections. The connectors glued with epoxy adhesive provided better strength and stiffness for the composite specimens when compared to the connectors fixed to the wood by pre-drilling. The differences between the strength and stiffness of the connection systems analysed were statistically significant. The regression models proposed presented a good approximation for the estimation of the Kser and Ku slip moduli of the composite specimens analysed.

Potential of Genome-Wide Association Studies and Genomic Selection to Improve Productivity and Quality of Commercial Timber Species in Tropical Rainforest, a Case Study of Shorea platyclados

Shorea platyclados (Dark Red Meranti) is a commercially important timber tree species in Southeast Asia. However, its stocks have dramatically declined due, inter alia, to excessive logging, insufficient natural regeneration and a slow recovery rate. Thus, there is a need to promote enrichment planting and develop effective technique to support its rehabilitation and improve timber production through implementation of Genome-Wide Association Studies (GWAS) and Genomic Selection (GS). To assist such efforts, plant materials were collected from a half-sib progeny population in Sari Bumi Kusuma forest concession, Kalimantan, Indonesia. Using 5900 markers in sequences obtained from 356 individuals, we detected high linkage disequilibrium (LD) extending up to >145 kb, suggesting that associations between phenotypic traits and markers in LD can be more easily and feasibly detected with GWAS than with analysis of quantitative trait loci (QTLs). However, the detection power of GWAS seems low, since few single nucleotide polymorphisms linked to any focal traits were detected with a stringent false discovery rate, indicating that the species’ phenotypic traits are mostly under polygenic quantitative control. Furthermore, Machine Learning provided higher prediction accuracies than Bayesian methods. We also found that stem diameter, branch diameter ratio and wood density were more predictable than height, clear bole, branch angle and wood stiffness traits. Our study suggests that GS has potential for improving the productivity and quality of S. platyclados, and our genomic heritability estimates may improve the selection of traits to target in future breeding of this species.

Genetic Improvement of Sawn-Board Stiffness and Strength in Scots Pine (Pinus sylvestris L.).

Given an overall aim of improving Scots pine structural wood quality by selective tree breeding, we investigated the potential of non-destructive acoustic sensing tools to accurately predict wood stiffness (modulus of elasticity, MOE) and strength (modulus of rupture, MOR) of sawn boards. Non-destructive measurements of wood density (DEN), acoustic velocity (VEL) and MOE were carried out at different stages of wood processing chain (standing trees, felled logs and sawn boards), whilst destructively measured stiffness and strength served as benchmark traits. All acoustic based MOE and VEL estimates proved to be good proxies (rA > 0.65) for sawn-board stiffness while MOETREE, VELHIT and resistograph wood density (DENRES) measured on standing trees and MOELOG and VELFAK measured on felled logs well reflected board strength. Individual-tree narrow-sense heritability () for VEL, MOE and MOR were weak (0.05–0.26) but were substantially stronger for wood density (0.34–0.40). Moreover, additive genetic coefficients of variation for MOE and MOR were in the range from 5.4% to 9.1%, offering potential targets for exploitation by selective breeding. Consequently, selective breeding based on MOETREE, DENRES or stem straightness (STR) could improve several structural wood traits simultaneously.

Wood cell wall ultrastructure The key to understanding wood properties and behaviour

ABSTRACT In the last 100 years, major advances have been made in understanding wood cell wall ultrastructure in tracheids, fibres, vessels and parenchyma and its relationship with xylem function and wood properties. This review will focus on how the development of imaging techniques and their application to wood cell walls has led to an understanding of cell wall organisation and the relationship between micro and macro scale properties in wood and wood-based materials. Topics such as wood formation, wood chemistry and reaction wood have recently been reviewed elsewhere and are considered only briefly in this review. Two features of wood cell walls have dominated the literature; orientation and layering of cellulose which determines the longitudinal stiffness of wood, and the distribution (topochemistry) of lignin which determines compression strength and pulping properties.

Phenotypic assessment of wood density and stiffness in Melia dubia plantations from three locations using non-destructive tools

Phenotyping large populations for assessing the variability for wood traits is the basic and critical step for developing improved genotypes/clones in the conventional or molecular marker-based tree improvement programmes of timber-yielding species. Melia dubia is rapidly emerging as a potential timber species with large-scale plantations being raised in different parts of India. In this study, large number of M. dubia trees (n = 940) were phenotyped for girth at breast height, wood basic density and stiffness from six plantations at three different locations, i.e. Yeshwanthpura (Kolar district), Hunsur and adjoining areas (Mysore district) and Kollegal (Mandya district) of Karnataka. Non-destructive tools namely pilodyn penetrometer and stress wave timers were used for phenotyping of wood density and wood stiffness, respectively. Across the locations, pilodyn penetration ranged from 12 to 30 mm and stress wave velocity ranged from 3.45 to 4.54 km/s. Plantations in the Hunsur area were characterized with relatively high pilodyn penetration (means low basic density), whereas stress wave velocity was uniformly distributed in all three locations. 11.68% of total number of trees (3.11% with GBH ≥ 37.5 cm from Yeshwanthpura and 8.57% trees from Kollegal) exhibiting pilodyn penetration range from 12 to 17 mm can be considered for selection for high density and 19.3% of trees (3.9% of trees from Yeshwanthpura, 4.4% trees from Hunsur and 11.02% trees from Kollegal) having stress wave velocity ranging from 4.05 to 4.46 km/s can be considered for high stiffness in the future tree improvement programmes. More than twofolds variation in pilodyn penetration and sufficiently large variation in stress wave velocity provide the opportunity for the development of trait-specific markers.

The effect of joints model to the vibration characteristics of wood

The One piece of the wooden beam has different vibration characteristics compared to the two pieces of wood with a joint. One of the parameters measured is the dynamic stiffness of wood. The method used is a technique in which the vibration excitation test using a hammer with a rubber head. The wood used in this study is Gofasa (vitex cofassus). The Properties of wood was using the data from previous studies. Vibration characteristic of a piece of wood was used for comparison purposes. Two pieces of wood have joined and secured by bolts. Cantilever beam model has used with the knock in a perpendicular direction to the wood fibres. The joints model used to excitation test is the plain scarf, hooked scarf, half lap splice, and tabled splice. All of these models were tested to determine the characteristics of vibration. The results showed the different vibration characteristics for each model. The results are used as a recommendation of the best models in distributing the vibration from the vibration source.

Temperature-humidity-time equivalence and relaxation in dynamic viscoelastic response of Chinese fir wood

Design, application and service life of modern engineered wood and its products are closely related to environmental temperature and relative humidity (RH). In this study, the frequency-dependent viscoelastic properties of Chinese fir wood were investigated under different hygrothermal conditions (temperature: 30–80 °C, RH: 0–85%), to verify the applicability of humidity-time and temperature-humidity-time equivalence principles to wood viscoelasticity (i.e., the equal effects of elevating temperature, increasing RH, or prolonging testing time on the changes of stiffness and damping). The relaxation of wood cell wall was compared under moisture equilibrium and non-equilibrium states. It was demonstrated that both the humidity-time equivalence and temperature-humidity-time equivalence principles were applicable for describing the evolution of wood stiffness. Master curves constructed by humidity-time equivalence and temperature-time equivalence principles were basically overlapped at a short-time region (frequency >0.01 Hz) when reference condition was 30 °C/0% RH. However, the humidity-time equivalence principle failed to predict wood damping properties, regardless of hygrothermal condition. The testing frequency (fc, assigned to the transition of different relaxation processes) corresponded to the local minimum value of tan δ was ranged from 8 to 30 Hz and moved to the high frequency direction with increasing RH level. The fc value at moisture equilibrium state was lower than non-equilibrium state (no matter moisture adsorption or desorption). It was attributed the higher fc value at moisture non-equilibrium state to the unstable configuration structure of wood cell wall. These findings not only help understanding the wood-water relations, but also be relevant for the utilization and production processes of engineered wood and its products in the construction and building fields.

The orthotropic viscoelastic properties of Chinese fir wood during the temperature ramping process

In this study, the orthotropic viscoelasticity of Chinese fir wood (Cunninghamia lanceolata [Lamb.] Hook) was investigated during the temperature ramping process. The storage modulus (E′) and loss modulus (E″) of longitudinal (L), radial (R), and tangential (T) specimens with six levels of moisture content (MC) ranging from 0.6 to 22.0% were determined form 20 to 280 °C. The change in E′ was influenced by the dual effects of temperature and MC; the loss of adsorbed water in the wood cell wall caused an increase in wood stiffness. The individual decline in E′ was affected by heating to different degrees and the heating exerted more influence on the transverse specimens and less contribution to the L specimens. Different relaxation processes of E′′ were observed in specimens with different MCs in the three main directions, indicating that the mechanical relaxation of wood was affected by its MC and microstructure. The β and γ-relaxation processes exhibited a conjointly circular arc shape in the transverse directions, which was attributed to the superposition of the transitions of lignin and hemicellulose. A higher α-loss peak temperature (α-TLP) and intensity of the α-relaxation process were observed in the L specimens than the transverse specimens. The β-TLP and γ-TLP decreased with increasing MC in all orthotropic directions, whereas the individual decline in TLP was affected differently by MC. In the β-relaxation process, the TLP was more sensitive to MC changes in the L direction than in the transverse directions. In addition, the individual TLP in the R and T directions was influenced by per unit adsorbed water to a similar degree for the β and γ-relaxation processes. These findings suggest that the difference in the orthotropic viscoelastic performance might cause some drying defects during the water loss process.

Multi-trait genomic selection for weevil resistance, growth, and wood quality in Norway spruce.

Plantation‐grown trees have to cope with an increasing pressure of pest and disease in the context of climate change, and breeding approaches using genomics may offer efficient and flexible tools to face this pressure. In the present study, we targeted genetic improvement of resistance of an introduced conifer species in Canada, Norway spruce (Picea abies (L.) Karst.), to the native white pine weevil (Pissodes strobi Peck). We developed single‐ and multi‐trait genomic selection (GS) models and selection indices considering the relationships between weevil resistance, intrinsic wood quality, and growth traits. Weevil resistance, acoustic velocity as a proxy for mechanical wood stiffness, and average wood density showed moderate‐to‐high heritability and low genotype‐by‐environment interactions. Weevil resistance was genetically positively correlated with tree height, height‐to‐diameter at breast height (DBH) ratio, and acoustic velocity. The accuracy of the different GS models tested (GBLUP, threshold GBLUP, Bayesian ridge regression, BayesCπ) was high and did not differ among each other. Multi‐trait models performed similarly as single‐trait models when all trees were phenotyped. However, when weevil attack data were not available for all trees, weevil resistance was more accurately predicted by integrating genetically correlated growth traits into multi‐trait GS models. A GS index that corresponded to the breeders’ priorities achieved near maximum gains for weevil resistance, acoustic velocity, and height growth, but a small decrease for DBH. The results of this study indicate that it is possible to breed for high‐quality, weevil‐resistant Norway spruce reforestation stock with high accuracy achieved from single‐trait or multi‐trait GS.

Non-Destructive Assessment of Wood Stiffness in Scots Pine (Pinus sylvestris L.) and its Use in Forest Tree Improvement

Wood stiffness is an important wood mechanical property that predetermines the suitability of sawn timber for construction purposes. Negative genetic correlations between wood stiffness and growth traits have, however, been reported for many conifer species including Scots pine. It is, therefore, important that breeding programs consider wood stiffness and growth traits simultaneously. The study aims to (1) evaluate different approaches of calculating the dynamic modulus of elasticity (MOE, non-destructively assessed stiffness) using data from X-ray analysis (SilviScan) as a benchmark, (2) estimate genetic parameters, and (3) apply index selection. In total, we non-destructively measured 622 standing trees from 175 full-sib families for acoustic velocity (VEL) using Hitman and for wood density (DEN) using Resistograph and Pilodyn. We combined VEL with different wood densities, raw (DENRES) and adjusted (DENRES.TB) Resistograph density, Pilodyn density measured with (DENPIL) and without bark (DENPIL.B), constant of 1000 kg·m−3 (DENCONST), and SilviScan density (DENSILV), to calculate MOEs and compare them with the benchmark SilviScan MOE (MOESILV). We also derived Smith–Hazel indices for simultaneous improvement of stem diameter (DBH) and wood stiffness. The highest additive genetic and phenotypic correlations of the benchmark MOESILV with the alternative MOE measures (tested) were attained by MOEDENSILV (0.95 and 0.75, respectively) and were closely followed by MOEDENRES.TB (0.91 and 0.70, respectively) and MOEDENCONST and VEL (0.91 and 0.65, respectively for both). Correlations with MOEDENPIL, MOEDENPIL.B, and MOEDENRES were lower. Narrow-sense heritabilities were moderate, ranging from 0.39 (MOESILV) to 0.46 (MOEDENSILV). All indices revealed an opportunity for joint improvement of DBH and MOE. Conclusions: MOEDENRES.TB appears to be the most efficient approach for indirect selection for wood stiffness in Scots pine, although VEL alone and MOEDENCONST have provided very good results too. An index combining DBH and MOEDENRES.TB seems to offer the best compromise for simultaneous improvement of growth, fiber, and wood quality traits.

Does Thinning Intensity Affect Wood Quality? An Analysis of Calabrian Pine in Southern Italy Using a Non-Destructive Acoustic Method

In the middle of XIX century, Calabrian pine was planted in southern Italy to increase the forest cover in mountainous areas. Many of these forest stands were never managed, since they were considered non-profitable for wood production. Therefore, in order to promote timber value, it is fundamental to study, more deeply, the characteristics and management options for this species. The acoustic technologies applied to predict the mechanical and physical properties of timber are well-established practices in forest research. In this study, we hypothesized that the tree stand density could influence the dynamic modulus of elasticity (MOEd) and, therefore, the future wood quality. We specifically aimed to verify if different management options, when applied, could influence the timber quality of Calabrian pine growing in similar environmental conditions. The study was conducted in the Aspromonte National Park (Calabria, Southern Italy). We derived the MOEd values from data obtained by the acoustic velocity measured through the TreeSonic™ timer. Calabrian pine trees were selected in stands where different intensities of thinning were applied eleven years before this study began (no thinning, thinning 25%, thinning 50%, and thinning 75%). The percentage refers to the number of trees cut with respect to the total number of occurring trees. The analyses were conducted on a total of 804 trees (201 trees for each intensity of thinning). A strong positive correlation was observed between the acoustic velocity, the thinning treatments and diameter at breast height (DBH). The thinning realized at 25% induced better tree wood quality. We also analyzed the best predictors for MOEd estimation, using variables easily measurable in the field, such as tree diameter, tree height, or their transformations (number of trees per hectare, basal area per hectare). We provide, here, a useful tool for predicting the wood stiffness in relation to stand parameters easily measurable in forest inventories.

Frequency-dependent viscoelastic properties of Chinese fir (Cunninghamia lanceolata) under hygrothermal conditions. Part 1: moisture adsorption

Abstract To elucidate the frequency-dependent viscoelasticity of wood under a moisture non-equilibrium state, changes in stiffness and damping as a function of frequency were investigated during the moisture adsorption process. The moisture adsorption processes were carried out at six temperatures (30–80°C) and three relative humidity levels (30, 60 and 90% RH). During the moisture adsorption process, the wood stiffness decreased, and damping increased with the increment of moisture content (MC). Regardless of the moisture adsorption time, the wood stiffness increased, and damping decreased with the increasing testing frequency. Based on the re-organized Williams-Landel-Ferry (WLF) model, the time-moisture superposition (TMS) relation was assumed to be applicable for developing a master curve of wood stiffness during the moisture adsorption process. The frequency ranges of the stiffness master curves spanned from 16 to 23 orders of magnitude at temperatures ranging from 30 to 80°C. However, the TMS relation was not able to predict the wood damping properties during the moisture adsorption process due to the multi-relaxation system of the wood and the non-proportional relationship between free volume and MC at transient moisture conditions.

Frequency-dependent viscoelastic properties of Chinese fir (Cunninghamia lanceolata) under hygrothermal conditions. Part 2: moisture desorption

Abstract The frequency-dependent viscoelasticity of Chinese fir (Cunninghamia lanceolata) during moisture desorption was investigated and the applicability of the time-moisture superposition (TMS) relation on wood stiffness and damping during the moisture desorption was verified. The hygrothermal conditions for the moisture desorption were set up as six constant temperatures ranging from 30 to 80°C and three relative humidity (RH) levels at 0, 30 and 60%. Due to the elimination of water during the moisture desorption, the stiffness of the Chinese fir increased, whereas the damping decreased. With the increase in frequency, increased stiffness and decreased damping were observed. Utilizing the TMS relation, it was possible to construct master curves of wood stiffness at temperatures ranging from 30 to 80°C. The linear relationship between the shift factor and the moisture content (MC) manifested a low intermolecular cooperativity between the polymers and a narrow relaxation window. However, the TMS relation was not able to predict the wood damping properties during the moisture desorption, because wood is a multi-relaxation system. The non-proportional relationship between the free volume and MC during the moisture desorption may also explain why the TMS relation failed to construct master curves of the wood damping properties.

Genetic Variation in Acoustic Time of Flight and Drill Resistance of Juvenile Wood in a Large Loblolly Pine Breeding Population

AbstractAcoustic time of flight and drill resistance (surrogates for wood stiffness and density, respectively) were measured on 11,097 standing trees from 269 pollen-mix families of loblolly pine (Pinus taeda L.) in 6- to 9-year-old progeny tests at eight sites across the southeastern United States. Specific gravity was measured on two test sites. The phenotypic correlation between specific gravity and drill resistance was moderate (r = 0.68), whereas the genetic correlation was very strong (rg = 0.96). Narrow-sense heritabilities for acoustic time of flight and drill resistance were around 0.35 for individual trees and very strong (0.90) for family means. High genetic correlations (>0.80) between pairs of sites suggested a low genotype-by-environment interaction for both traits. Genetic correlations between wood quality traits and other economic traits (growth and stem straightness) were low except for a moderate correlation between acoustic time of flight and tree slenderness (rg = –0.64). The checklot ranked near the middle for both wood quality traits, implying no inadvertent selection occurred in this population that has been selected intensively for volume productivity. This study is the first to apply these tools in a large breeding program, and results suggest they are effective for selecting genotypes for wood quality.

Proline-rich protein gene PdPRP regulates secondary wall formation in poplar

Proline-rich protein (PRP) is a plant cell wall associated protein. Its distinct patterns of regulation and localization studied in a number of plants indicate that it may play important roles in growth and development. However, the mechanism of how these genes control secondary cell wall development in tree species is largely unknown. Here, we report that a Populus deltoides (Marsh.) proline-rich protein gene PdPRP was preferentially expressed in immature/mature phloem and immature xylem in P. deltoides. PdPRP overexpression increased poplar plant height and diameter as well as the radial width of the phloem and xylem regions, facilitated secondary wall deposition, and induced expression of genes related to microfibril angle (MFA) and secondary wall biosynthesis. Downregulation of PdPRP retarded poplar growth, decreased the radial width of the secondary phloem and secondary xylem regions, reduced secondary wall thickening in fibers and vessels, and decreased the expression of genes related to MFA and secondary wall biosynthesis. These results suggest that PdPRP might positively regulate secondary cell wall formation by promoting secondary wall thickening and expansion in poplar. PdPRP-overexpressing poplar had a lower MFA, indicating that PdPRP may be useful for improving wood stiffness and properties in plants. Together, our results demonstrate that PdPRP is a proline-rich protein associated with cell wall development, playing a critical role in regulating secondary cell wall formation in poplar.

Non-destructive evaluation of wood stiffness and fiber coarseness, derived from SilviScan data, via near infrared hyperspectral imaging

Near infrared hyperspectral imaging combined with partial least squares regression analysis was used to evaluate wood stiffness (modulus of elasticity) and fiber coarseness. Five samples with normal wood and compression wood collected from two Japanese Cedar ( Cryptomeria japonica) trees were analyzed. To achieve high reliability of the prediction values, a SilviScan system (X-ray densitometry, X-ray diffractometry, and optical microscopy) with the high spatial resolution was used for measuring reference data. The measurement interval for modulus of elasticity and fiber coarseness was 1 mm and 25 µm, respectively. After spectral pre-treatment and key wavelengths selection, partial least squares analysis was applied to calibrate near infrared data to reference values. The determination coefficient ( RCV2) of modulus of elasticity was 0.66 with a root mean square error of cross validation (RMSECV) of 1.80 GPa. For the constructed fiber coarseness calibration model, RCV2 and RMSECV were 0.62 and 35.02 µm/g, respectively. Finally, modulus of elasticity and fiber coarseness mapping results show detailed information (156 µm/pixel) at the grown ring level. The differences among earlywood, latewood, and compression wood were all well identifiable.

Strength and stiffness of the reaction wood in five Eucalyptus species

Abstract Tree stems deviating from the vertical position react by the formation of tension wood (TW) or compression wood (CW), which are called in general as reaction wood (RW), in which the cells are modified chemically and anatomically. The focus of the present work is the mechanical behavior of TW in five 37-year-old Eucalyptus species, which were grown on a planting area with an average slope of 28% leading to decentralized pith in the trees, which is an unequivocal indication of the presence of RW. TW and opposite wood (OW) samples were isolated and subjected to a compression-parallel-to-grain test. It was observed that TW is less resistant and less stiff than the OW.