Las plantaciones forestales comerciales son una estrategia para proteger de la sobreexplotación a los bosques naturales, por lo que es importante, conocer las propiedades físicas de su madera. El ...objetivo del trabajo fue determinar la calidad de la madera con base en sus propiedades físicas, y la cantidad de biomasa en una plantación de Pinus engelmannii de 17 años. El diámetro normal y altura total se midió en todos los árboles encontrados en 20 sitios rectangulares de 3.0 x 6.0 m distribuidos en cuatro líneas. En cada sitio, con un taladro de Pressler se tomó un núcleo de crecimiento a 1.30 m de altura, en dos árboles dominantes. Las propiedades físicas, densidad básica (DB), contenido de humedad (CH), contracciones volumétricas totales (CVT), y punto de saturación de la fibra (PSF) se determinaron aplicando las fórmulas específicas de cada componente. La biomasa se estimó con los valores de volumen y densidad básica, además de tres ecuaciones alométricas. Los resultados indican que la DB fue de 0.379 g cm−3, CH de 199.37%, CVT de 13.63%, PSF de 39.28% y promedio de biomasa fustal de 22.79 kg. El ANOVA mostró que la sección dentro del árbol influyó de manera significativa (p < 0.05) en DB y CH, con correlación negativa (r = - 0.96). La madera de la plantación es homogénea con respecto a la DB, CH y CVT, mientras que las dos primeras variables presentaron variación radial. La biomasa presentó relación con la densidad básica y el diámetro normal.
Key Message
The original method proposed provides useful data for the analysis of ring density variations in stems, highlighting the particular behaviour observed at the base of the tree.
Tree growth ...in volume and wood density are the two factors that determine tree biomass. They are important for assessing wood quality and resource availability. Analysing and modelling the relationships between these two factors are important for improving silvicultural practices of softwoods like Norway spruce, for which a negative relationship is generally observed between ring width and ring density. We describe an original method for obtaining ring density data (
RD
) by coupling conventional ring width measurements (
RW
) and air-dry density measurements obtained with X-ray computer tomography at high-speed but with lower resolution than the
RW
data. The method was applied to 200 discs of Norway spruce trees sampled in a plantation to assess its relevance. The
RW
–
RD
relationship was analysed as a function of cambial age and disc height in the stem. Descriptive statistical models were developed and compared to models in the literature. These models made it possible to analyse the variations of
RD
as a function of height in the tree at a given cambial age or for a given calendar year and also to observe a shift in the juvenile wood–mature wood boundary between the bottom of the tree and the rest of the stem. The
RD
–
RW
relationship was observed in the juvenile wood at the base of the stem but not in the juvenile wood higher up. Furthermore, the juvenile wood formed at the base of the tree was denser than the juvenile wood formed higher up and the mature wood formed at the same height. In conclusion, the proposed method was found to be relevant, especially when wood discs are readily available, and the results obtained highlighted the importance of distinguishing juvenile wood formed at the base of the tree from that formed higher up.
The aim of this study was to determine the hardness and reduced modulus of elasticity of juvenile wood of Scots pine (Pinus sylvestris L.) using the nanoindentation method, and then to compare the ...results obtained with those of mature wood. The hardness of juvenile pine wood determined by means of the nanoindentation method was 0.444 GPa while for mature wood it was 0.474 GPa. Statistically significant differences between the values were found. The reduced modulus of elasticity in juvenile wood was 14.0 GPa and 16.4 GPa in mature wood. Thus, the hardness values obtained were about 7% higher, while the modulus of elasticity was 17% higher in mature wood. All determinations were made in the S2-layer of the secondary cell wall.
Key message
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.
Context
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.
Aims
We model the radial variation of these veneer-critical wood properties and determine whether it varies with growing conditions.
Methods
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.
Results
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.
Conclusion
Radial variation varied among sites and will likely impact the recovery of structural grade veneer from plantations.
Teak (Tectona grandis L. f) has been introduced to reforestation programs in many tropical countries for timber production. The use of teak plantations has changed the supply from large-diameter logs ...to small-diameter logs featuring a higher proportion of juvenile wood and more knots. Generally, the teak from fast-growth plantation is harvested after 15–30 years of growth, with logs ranging from 12 to 30 cm in diameter. The goal of this work was to review the factors that influence the heartwood formation, variation, quality, color, and durability in teak and to understand which factors should be controlled in fast-growth plantations. Important factors in the heartwood properties of teak trees from fast-growth plantations are as follows: the tree age, longitudinal variation, geographic location, environmental conditions, and silvicultural activities. These factors influence heartwood extractive content, color variation, and durability.
Plantation-grown juvenile wood species are extensively used as raw materials in the Chinese wood industry. The weathering performances of the wood are crucial for outdoor application. Two of the most ...important plantation-grown juvenile woods, poplar (
×
cv. ‘74/76ʼ) and Chinese fir (
Hook), were sliced into thin veneers and compared in this study to observe their weathering performance during exposure to UV alone for 504 h and UV/water for 168 h. The color difference, weight loss, and tensile strength loss of both veneers all increased with exposure time. Scanning electron microscopy showed that the initial structural deterioration originates from the corner of the middle lamella and pit, followed by cell separation, cell wall thinning, deformation, and collapse. Fourier transmission infrared spectroscopy, electron resonance spectrometry and X-ray photoelectron spectroscopy revealed a decrease in lignin-based infrared absorption intensity and radical generation, as well as an increase in O/C ratio throughout the exposure. Water spray considerably accelerated deterioration by washing away the degraded fragments, thereby exposing the fresh substrate underneath. Compared to poplar wood, Chinese fir showed durable structural integrity but more darkening during weathering. These findings reveal the anatomically structural weak phase and photo-degradation performance of two plantation-grown woods during weathering. The results of this work may facilitate the proper external use and further photo-stabilization treatment of plantation-grown juvenile wood products.
The structural use of wood from young trees requires gluing smaller timber pieces to form large elements. In young Eucalyptus timber of structural dimensions, knots do not significantly diminish the ...mechanical properties, yet their influence on wood adhesion has not been widely studied. Therefore, the aim of the study was to assess the influence of knots on the bond quality of face-glued wood from young E. grandis. Wood from seven-year-old E. grandis trees was tested in shear on the bond-line (polyurethane adhesive) using paired samples of knot-containing and clear wood samples. Knot features did not correlate with shear strength or wood failure percentage. Knot-containing samples had a lower percentage of wood failure (5.8%), but the same shear strength as clear wood samples. Below a wood density of 650 kg m
−3
, clear and knot-containing wood behaved similarly, but above this value, knots influenced wood adhesion negatively. By simulating glulam beams with high-density wood on the outer lamellas, it was possible to show that shear stress on those bond-lines is lower than the minimum shear strength observed on dense knot samples. Hence, lower adhesion caused by knots on denser wood probably does not represent a significant problem for glued laminated products from young Eucalyptus grandis trees.
Ray traits affect secondary xylem development and wood properties. Pinus massonia and Cunninghamia lanceolata, commercially important timber species, were chosen to study the differences in wood ray ...traits of juvenile versus mature wood. Seven ray traits, i.e., percentage of rays, ray spacing, ray number, uniseriate ray height, fusiform ray height, ray parenchyma cell length and ray tracheid length, as well as eight wood axial tissue traits, were investigated quantitatively. Intraspecific variations in ray traits and axial tissue traits between juvenile wood and mature wood were displayed in violin plots. The results showed that anatomical differences between juvenile wood and mature wood were significant for both ray traits and axial tissue traits. Juvenile wood generally possessed the larger percentage of rays, higher ray spacing and ray number, smaller ray height and shorter ray cells than mature wood. A positive correlation was present between the ray parenchyma cell length and ray tracheid length. Negative correlations of the ray number and ray spacing with uniseriate ray height were found. Additionally, the axial tracheid cell wall thickness all had Pearson’s correlations with ray spacing, ray number and ray parenchyma cell length.
Wood properties (annual ring width, tracheid length, microfibril angle MFA, basic density, and air-dry density) and mechanical properties (modulus of elasticity MOE, modulus of rupture MOR, bending ...work, and compressive strength) in 34-year-old
Chamaecyparis obtusa
trees of six half-sib families were measured from pith to bark to clarify radial variations in inheritance of these traits and the relationships between wood properties and mechanical properties. In addition, within-tree and among-family differences in the load–deflection curves were discussed. Radial variations of all wood properties were fitted to linear or nonlinear mixed-effects models with random effects of families. The MFA was correlated with MOE in all radial positions, whereas air-dry density correlated with all mechanical properties in mature wood. Radial variations in broad-sense heritability differed between wood properties. A relatively higher broad-sense heritability was recognized in almost all wood properties for mature wood. Based on the results, it was concluded that mechanical properties in mature wood can be effectively improved using MFA and air-dry density as criteria. In addition, the types of load–deflection curve in mature wood differed from those in juvenile wood, suggesting that not only elastic properties, but also plastic properties in
C. obtusa
are affected by genetic controls, especially in mature wood.
Wood used for structural purposes has increased in the last decade in Spain. However, as raw material, wood needs to comply with requirements that are not always present. Knowledge about the wood ...quality from the trees on the stand is essential for providing feedback to forest managers and for taking the required actions to obtain suitable silviculture treatments. Two of the main wood species used in construction in Spain, Pinus nigra and Pinus sylvestris, have been studied in order to determine the amount of juvenile wood, which has been identified as a harmful characteristic for its decrease in quality of the physical-mechanical properties of these species. Being relevant for the best quality of timber in the part along the bole where the logs are obtained, the distribution of juvenile wood at different heights and the effect of several silvicultural treatments have had on juvenile wood formation has been considered. The juvenile-mature wood boundary (transition year) was calculated through segmented linear mixed models employing as variables annual latewood density, obtained through micro X-ray densitometry, silvicultural practices, and a drought index. The results show how juvenile and mature wood is distributed along the bole and the proportion of juvenile wood. Its reduction according to the different thinning and pruning silvicultural practices is presented.
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