Growth Ring Structure Research Articles

New Methods in Digital Wood Anatomy: The Use of Pixel-Contrast Densitometry with Example of Angiosperm Shrubs in Southern Siberia.

This methodological study describes the adaptation of a new method in digital wood anatomy, pixel-contrast densitometry, for angiosperm species. The new method was tested on eight species of shrubs and small trees in Southern Siberia, whose wood structure varies from ring-porous to diffuse-porous, with different spatial organizations of vessels. A two-step transformation of wood cross-section photographs by smoothing and Otsu's classification algorithm was proposed to separate images into cell wall areas and empty spaces within (lumen) and between cells. Good synchronicity between measurements within the ring allowed us to create profiles of wood porosity (proportion of empty spaces) describing the growth ring structure and capturing inter-annual differences between rings. For longer-lived species, 14-32-year series from at least ten specimens were measured. Their analysis revealed that maximum (for all wood types), mean, and minimum porosity (for diffuse-porous wood) in the ring have common external signals, mostly independent of ring width, i.e., they can be used as ecological indicators. Further research directions include a comparison of this method with other approaches in densitometry, clarification of sample processing, and the extraction of ecologically meaningful data from wood structures.

A 3D multi-scale hygro-mechanical model of oak wood

A multi-scale framework is proposed for the prediction of the macroscopic hygro-elastic properties of oak wood. The distinctive features of the current multi-scale approach are that: (i) Four different scales of observation are considered, which enables the inclusion of heterogeneous effects from the nano-, micro-, and meso-scales in the effective constitutive behavior of oak at the macro-scale, (ii) the model relies on three-dimensional material descriptions at each considered length scale, and (iii) a moisture-dependent constitutive assumption is adopted at the nano-scale, which allows for recovering the moisture dependency of the material response at higher scales of observation. In the modeling approach, oak wood is assumed as homogeneous at the macro-scale. The meso-scale description considers the cellular structure of individual growth rings with three different densities. At the micro-scale, the heterogeneous nature of cell walls is described by the characteristics of the primary and secondary cell wall layers. Finally, the nano-scale response is determined by cellulose micro-fibrils embedded in a matrix of hemicellulose and lignin. The oak properties at the four length scales are connected via a three-level homogenization procedure, for which, depending on the geometry of the fine-scale configuration, an asymptotic homogenization procedure or Voigt averaging procedure is applied at each level to determine the effective hygro-elastic properties at the corresponding coarse scale. In addition, the moisture adsorption isotherms at each scale are constructed from a volume-weighted averaging of the moisture adsorption characteristics at the scale below. The computational results demonstrate that the macro-scale moisture-dependent, hygro-elastic behavior of oak wood is predicted realistically, thereby revealing the influence of the material density, the micro-fibril orientation, and the hygro-elastic properties from the underlying scales. The computed macro-scale properties of oak are in good agreement with experimental data reported in the literature.

Modeling of the Statistical Distribution of Tracheids in Conifer Rings: Finding Universal Criterion for Earlywood-Latewood Distinction.

The quantitative description of growth rings is yet incomplete, including the functional division into earlywood and latewood. Methods developed to date, such as the Mork criterion for conifers, can be biased and arbitrary depending on species and growth conditions. We proposed the use of modeling of the statistical distribution of tracheids to determine a universal criterion applicable to all conifer species. Thisstudy was based on 50-year anatomical measurements of Pinus sylvestris L., Pinus sibirica Du Tour, and Picea obovata Ledeb. near the upper tree line in the Western Sayan Mountains (South Siberia). Statistical distributions of the cell wall thickness (CWT)-to-radial-diameter (D) ratio and its slope were investigated for raw and standardized data (divided by the mean). The bimodal distribution of the slope for standardized CWT and D was modeled with beta distributions for earlywood and latewood tracheids and a generalized normal distribution for transition wood to account for the gradual shift in cell traits. The modelcan describe with high accuracy the growth ring structure for species characterized by various proportions of latewood, histometric traits, and gradual or abrupt transition. The proportion of two (or three, including transition wood) zones in the modeled distribution is proposed as a desired criterion.

Structural, rheological, pasting, and digestive properties of wheat A-starch: Effect of outshell removal combined with annealing

Wheat A- starch was subjected to single and combined CaCl2 and annealing (ANN) treatments. The influence of the treatment on wheat A- starch's structural, rheological, pasting, and digestive characteristics were studied. The results indicated that the application of CaCl2 treatment caused the removal of the outer layer of wheat A-starch, disrupted the integrity of the growth ring structure, and lowered the molecular weight of amylopectin and relative crystallinity. Meanwhile, the application of outshell removal combined with ANN treatment led to significant damage to the starch granules, resulting in a marked reduction in relative crystallinity, as well as the molecular weight of amylopectin and amylose. However, no changes were found in the non-Newtonian pseudoplastic behavior of starch after single or combined treatments. Furthermore, the combination of outshell removal and annealing treatment resulted in a decreased peak viscosity as well as trough viscosity of starch. Moreover, long-time ANN treatment had the potential to improve the resistant starch (RS) content of deshell starch.

Spatial variation of eucalyptus fibres considering the structure of annual growth rings

Background: The fibres dimensions vary along a tree trunk, and these variations are related to the apical meristem and vascular cambium activities; understanding these variations would guide the best use of wood. There have been studies on the pattern of fibres dimensions variation along the tree trunk in the radial and longitudinal directions; however, the vast majority do not take into account the structure of the annual growth rings. Hence, this study aimed to obtain the pattern of fibres dimensions variation and their quality indexes along the tree trunk take into account the structure of the annual growth rings. Two Eucalyptus urophylla x Eucalyptus grandis hybrid clones were used in the study. Ten-year-old trees were selected and discs were removed from 13 longitudinal positions. The disks were prepared and the growth rings were subsequently identified and the samples used for maceration were collected. Twenty fibres were measured in the annual growth rings present in each longitudinal position. Results: In the longitudinal direction, within the annual growth rings, the fibre dimensions and their quality indices did not show a well-defined pattern of variation. In the radial direction, the length, cell wall thickness, wall fraction, and Runkel ratio of the fibres tended to increase following the pith-bark direction, while the lumen diameter and flexibility coefficient decreased. Conclusion: Nevertheless, the fibre width and fibre slenderness index did not present a well-defined pattern of variation in the radial direction.

Effect of twin-xuscrew extrusion combined with cold plasma on multi-scale structure, physicochemical properties, and digestibility of potato starches

The influence of twin-screw extrusion (TSE), cold plasma (CP, 1, 5, and 9 min), and their combination (TSE-CP) treatment on the structural, physicochemical, rheological, solubility, and in vitro digestive properties of potato starches were studied. The results showed that CP slightly changed the starch granules morphology, maintained the growth ring and crystalline structure, promoted depolymerization of the amylopectin branch chain, and increased crystallinity and the ΔH value. It is worth noting that the resistant starch content increased from 84.80 to 86.46% in the short time CP modified potato starch. Meanwhile, TSE and TSE-CP treatments influenced surface morphology, growth ring of potato starch significantly. However, the dually modified potato starch using combined TSE and CP treatments promoted depolymerization of longer chains, increased the proportion of shorter chains and solubility, and improved the degree of hydrolysis. Furthermore, the single and dual treatments did not change the FT-IR spectra pattern. This study suggests that the combination between TSE and CP had more profound modification than the single treatment. The TSE combined with CP is an eco-friendly, thermal, and non-thermal combination technology, which can improve the multi-scale structure of starch and enhance physicochemical properties. Also, the dual treatment can be used to produce modified starch for industrial applications.

Understanding the granule, growth ring, blocklets, crystalline and molecular structure of normal and waxy wheat A- and B- starch granules

Understanding the structural characteristics of starch can help in determining its functional properties and choosing appropriate applications. This work aimed to comprehensively characterize and understand the morphological, crystalline, and molecular structure of the normal and waxy wheat A- and B- starch granules. X-ray diffraction analysis revealed that both normal and waxy wheat A- and B- starch granules have a typical A-type crystalline structure. Additionally, scanning electron microscopy, small-angle X-ray scattering, and Fourier transform infrared spectroscopy analyses showed differences in shape, the thickness of semi-crystalline growth rings, and short-range molecular order of the normal and waxy A- and B- starch granules. The wheat A-starch granules contained lower proportions of A-chains (DP 6–12) and B1- chains (DP 13–24) than those of the wheat B- starch granules. Also, the results revealed that B1-chains (DP 13–24) play an important role in the formation of surface/mass fractal characteristics of starch granules. Furthermore, the atomic force microscopy analysis showed that the normal and waxy wheat A-starch granules are mass fractal, while the normal and waxy wheat B- starch granules are surface fractal.

Numerical Simulation of the Forming Process of Veneer Laminates

In automotive manufacturing, laminated veneer sheets are formed to have 3D geometries for the production of trim parts with wood surfaces. Nowadays, investigation of the formability requires extensive tests with prototype tools, due to the brittle, anisotropic and inhomogeneous material behaviors. The present paper provides numerical methods for the simulation of the forming process of veneers with non-woven backings. Therefore, a conventional forming process of an interior trim part surface is carried out experimentally and numerically, using veneer samples with different individual textures originating from the characteristic growth ring structure. Gray scale images of these samples are mapped to finite element models to account for the wood-specific structure. The forming simulation process comprises two steps, where a gravity simulation depicts the initial position of the blank sheets and the closing of the tool induces the material deformation. The virtual forming of the digital twins accurately reproduces the wrinkling behavior observed in experimental studies. Based on the proposed methods, the design process of manufacturing wood trim parts based on tedious prototype tooling can be replaced by a fully virtual forming process taking into account the individual growth-related properties of the veneer structure.

Structural changes in corn starch granules treated at different temperatures

The four structural levels of corn starch granules are as follows: particle structure, growth ring, crystalline region and chain structure. In this study, corn starch granules treated at different temperatures (50, 60, 70, 80, and 90 °C), then freeze-dried were evaluated. The corn starch granules remained largely intact in the control and at 50 °C and 60 °C, but with increasing temperature, the starch granules were broken. The growth ring structure and crystallization zone gradually broke up and disappeared with increasing temperature. Moreover, with increasing temperature, the degree of order (DO) and degree of the double helix (DD) of the crystalline region decreased gradually, indicating that the double helix structure of amylopectin in corn starch dissociated during heating. The molecular weight distribution index of corn starch was analyzed by gel permeation chromatography (GPC) and found that it increased with increasing temperature, indicating that the molecular chains of corn starch were broken during heating. In sum, the structural levels of corn starch granules, including the particle structure, growth ring, and crystalline region were damaged to varying degrees, whereas chain structure has been changed, after being processed at different temperatures. This study provides a model for theory of gelatinization in corn starch system.

Effect of thermal packaging temperature on Chinese steamed bread quality during room temperature storage

In order to investigate the influence of different packaging temperature on thermal-vacuum packaged Chinese steamed bread (CSB) quality under room temperature storage, the packaging temperatures of 50 °C, 70 °C and 90 °C were set respectively to study the effect on the packaging vacuum degree (VD) and starch retrogradation properties. The VD and moisture content of thermal-vacuum packaged CSB significantly increased with the increase of the packaging temperature from 50 °C to 90 °C, while the hardness of CSB decreased, and there was no significant difference in moisture migration during room temperature storage. The results of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and small angle X-ray scattering (SAXS) indicated that CSB packaged at different temperatures formed B-type crystals, leading to an enhanced the ordered and dense state of starch structure, and the semi-crystalline growth ring structure disappeared during storage. The influence of different packaging temperatures on VD of CSB could effectively hinder the formation of ordered and dense state of CSB starch, consequently delaying the crystallization of amylopectin and inhibiting the progress of staling. The result of this study is of great significance for improving the quality of starchy foods and guiding the industrial development of Chinese steamed bread.

Structural characteristics of low-digestible sweet potato starch prepared by heat-moisture treatment

The objectives of this study were to optimize the conditions for the preparation of sweet potato starch containing a high proportion of slowly digestible starch (SDS) by heat-moisture treatment (HMT), and to investigate the structural properties of SDS and resistant starch (RS) fractions isolated from this modified starch. Response surface methodology evaluation of considering temperature, time, and moisture content was conducted to determine the HMT condition for maximizing SDS yield. Maximum SDS content (50.9%) was obtained after 8.6 h at 113 °C with 22.8% moisture level. Scanning electron micrographs of RS fractions displayed growth ring structure and hollow regions. X-ray diffraction patterns of SDS + RS and RS fractions were not changed by HMT. Gelatinization enthalpy of the SDS + RS fraction was decreased more than that of the RS fraction. The results indicated that the SDS fraction consisted of less perfect crystallites and amorphous regions, whereas the RS fraction was composed mostly of crystalline regions.

Tree rings and growth trajectories of tree species from seasonally dry tropical forest

The presence of distinct growth rings in a large number of tropical tree species has allowed a range of studies involving the growth history during the life span of the tree. This work aimed to examine the presence of tree rings and study growth patterns of tree species from five seasonally dry tropical forest fragments. Wood cores were extracted using 5-mm increment borer. The macroscopic structure of growth rings from 24 deciduous tree species was observed under stereomicroscope and classified according to anatomical features and visibility of the ring boundary. Distinct growth rings were detected for 19 species (79%). Seven species were submitted to tree-ring analyses, including cross-dating and dating quality control using the COFECHA program. Dated ring-series were analysed by comparing increment rates and accumulated diameter at breast height fitted curves to detect growth patterns. The variations among growth curves indicated different strategies of establishment and development for each studied species, and allowed the identification of different ecological groups. The results show the potential of tree rings to study populations and communities of seasonally dry tropical forest.

The effect of surface fire on tree ring growth of Pinus radiata trees

Pinus radiata trees showed significantly reduced basal area increments and increased latewood/earlywood ratios, when their stem was charred by surface fires even if no needle damage occurred. An interaction of fire damage and precipitation on growth was observed. Heat from forest fires is able to penetrate beyond the bark layer and damage or completely kill a tree’s cambium. Short-term growth reductions following surface fires have been reported for some species. However, most studies have in common that they describe a compound effect of stem and foliage damage. This study investigated the impact of surface fires on the radial growth of Pinus radiata, where only the stem of trees was charred, while no needle damage was recorded. Tree ring measurements were performed on cores obtained at breast height. Analysis of variance and tests, based on annual basal area increment values were calculated to quantify pre- and post-fire growth differences of tree ring width and latewood/earlywood ratios. The analysis revealed significant growth reductions following a surface fire on P. radiata in the year on which the fire occurred as well as in the following year. As a consequence of the fire, basal area increment and latewood/earlywood ratios were significantly reduced. An interaction of fire damage and precipitation on growth was observed. The obtained results show how fires without crown damage can affect growth and tree ring structure of P. radiata trees and indicate that stem char could be associated with a significant decrease in ring width and latewood/earlywood ratio.

The frankincense tree Boswellia neglecta reveals high potential for restoration of woodlands in the Horn of Africa

Boswellia neglecta S. Moore is a frankincense-producing tree species dominantly found in the dry woodlands of southeastern Ethiopia. Currently, the population of this socio-economically and ecologically important species is threatened by complex anthropogenic and climate change related factors. Evaluation of tree age and its radial growth dynamics in relation to climate variables helps to understand the response of the species to climate change. It is also crucial for sustainable forest resource management and utilization. Dendrochronological and remote-sensing techniques were used to study periodicity of wood formation and leaf phenology and to assess the growth dynamics of B. neglecta. The results show that B. neglecta forms two growth rings per year in the study area. The growth ring structure is characterized by larger vessels at the beginning of each growing season and smaller vessels formed later in the growing season, suggesting adaptation to decreasing soil moisture deficits at the end of the growing season. Seasonality in cambial activity matches with a bimodal leaf phenological pattern. The mean annual radial growth rate of B. neglecta trees is 2.5mm. Tree age varied between 16 and 28years, with an average age of 22years. The young age of these trees indicates recent colonization of B. neglecta in the study region. The growth rate and seasonal canopy greenness (expressed by Normalized Difference Vegetation Index – NDVI) were positively correlated with rainfall, suggesting that rainfall is the main climatic factor controlling growth of B. neglecta. The observed temporal changes in leaf phenology and vessel size across the growth rings indicate that the species is drought tolerant. Therefore, it can be regarded as a key tree species for restoration of moisture-related limited areas across the Horn of Africa.

Microscopic investigation of defects in thermally compressed poplar wood panels

The combined effects of temperature and compression on the microstructure of solid-wood panels produced by Aspen (Populus tremula) wood were evaluated. Thermal compression was applied on aspen wood to increase the density for improving its physical and mechanical properties. The solid wood panels with dimensions of 100 mm by 500 mm by 25 mm were hot-pressed by using a laboratory hot press at a temperature of either 150 °C or 170 °C and pressure of either 1MPa or 2 MPa, respectively, for 45 min. Changes in the microstructure were detected by using a light microscope. The microscopic investigations revealed that the wood exhibited much defects in the process conditions of 170 oC / 2 MPa, and the distribution of defects were not uniform in the growth rings of the wood specimens in the two treatment groups. All defects in cell structure were quite distinct in the beginning and the last parts of the growth rings and the largest damages occurred in the fibers and vessels for the two process conditions. The results indicate that growth ring structure, vessel porosity, and cell wall thickness have a strong effect on wood behavior in various process conditions.

Analytical modeling, finite-difference simulation and experimental validation of air-coupled ultrasound beam refraction and damping through timber laminates, with application to non-destructive testing

Reliable non-destructive testing (NDT) ultrasound systems for timber composite structures require quantitative understanding of the propagation of ultrasound beams in wood. A finite-difference time-domain (FDTD) model is described, which incorporates local anisotropy variations of stiffness, damping and density in timber elements. The propagation of pulsed air-coupled ultrasound (ACU) beams in normal and slanted incidence configurations is reproduced by direct definition of material properties (gas, solid) at each model pixel. First, the model was quantitatively validated against analytical derivations. Time-varying wavefronts in unbounded timber with curved growth rings were accurately reproduced, as well as the acoustic properties (velocity, attenuation, beam skewing) of ACU beams transmitted through timber lamellas. An experimental sound field imaging (SFI) setup was implemented at NDT frequencies (120kHz), which for specific beam incidence positions allows spatially resolved ACU field characterization at the receiver side. The good agreement of experimental and modeled beam shifts across timber laminates allowed extrapolation of the inner propagation paths. The modeling base is an orthotropic stiffness dataset for the desired wood species. In cross-grain planes, beam skewing leads to position-dependent wave paths. They are well-described in terms of the growth ring curvature, which is obtained by visual observation of the laminate. Extraordinary refraction phenomena were observed, which lead to well-collimated quasi-shear wave coupling at grazing beam incidence angles. The anisotropic damping in cross-grain planes is satisfactorily explained in terms of the known anisotropic stiffness dataset and a constant loss tangent. The incorporation of high-resolution density maps (X-ray computed tomography) provided insight into ultrasound scattering effects in the layered growth ring structure. Finally, the combined potential of the FDTD model and the SFI setup for material property and defect inversion in anisotropic materials was demonstrated. A portable SFI demonstrator was implemented with a multi-sensor MEMs receiver array that captures and compensates for variable wave propagation paths in glued laminated timber, and improves the imaging of lamination defects.

Structural characteristics of slowly digestible starch and resistant starch isolated from heat–moisture treated waxy potato starch

The objective of this study was to investigate the structural characteristics of slowly digestible starch (SDS) and resistant starch (RS) fractions isolated from heat–moisture treated waxy potato starch. The waxy potato starch with 25.7% moisture content was heated at 120°C for 5.3h. Scanning electron micrographs of the cross sections of RS and SDS+RS fractions revealed a growth ring structure. The branch chain-length distribution of debranched amylopectin from the RS fraction had a higher proportion of long chains (DP≥37) than the SDS+RS fraction. The X-ray diffraction intensities of RS and SDS+RS fractions were increased compared to the control. The SDS+RS fraction showed a lower gelatinization enthalpy than the control while the RS fraction had a higher value than the SDS+RS fraction. In this study we showed the RS fraction is composed mainly of crystalline structure and the SDS fraction consists of weak crystallites and amorphous regions.

The significance of compression wood in restoration of the leader in Pinus sihestris L. damaged by moose (Alces alces). II. Structure of growth rings in regenerating stems in relation to juvenile wood formation

The corewood of pine ds very prone to compression wood formation, this changing the whole pattern of the tree ring structure and the siz.es of early and late wood. Compression wood always increases the formation of late wood at the expense of early wood. Tree rings with compression wood are generally wider than those without it, but there occur also tree rings wihout compression wood wider than those in which it is present, formed in the same year and in the same tree.

Dynamic response of earlywood and latewood within annual growth ring structure of Scots pine subjected to changing relative humidity

Abstract Scots pine (Pinus sylvestris L.) was subjected to relative humidity (RH) changes, and the dynamic strain field on the surface and in the bulk wood was monitored by digital speckle pattern interferometry and X-ray computed microtomography assisted by digital volume correlation. If a freely shrinking specimen was subjected to an RH decrement, earlywood (EW) and latewood (LW) at the surface layer were deformed in the opposite directions at the beginning of drying due to moisture gradient across the specimen. As a result, the surface and core behaved as independent sub-components, with the surface restrained in its response by the dimensionally unchanged core. With time, both LW and EW shrank as moisture content (MC) became uniform across the specimen. When an entire wood specimen was restrained from movement and desiccated in ambient RH, EW was stretched to compensate for the considerable shrinkage of LW. Knowledge about surface deformation at the annual ring level as a function of varying RH may be helpful to assess the risks associated with the damage of paint layers caused by fluctuations of ambient RH.

Moisture content effect on the fracture characterisation of Pinus pinaster under mode I

A moisture content effect on fracture characterisation of Pinus pinaster under mode I is addressed. The double cantilever beam test is selected for mode I loading, based on specimens scaled down to the growth ring level. Specimens are stabilised using aqueous solutions at several equilibrium moisture contents (\( M_{\text{e}} \)) ranging from 0 % to about 13 %. The strain energy release rate (\( G_{\text{I}} \)) is evaluated by applying the compliance-based beam method, from which the Resistance-curve is determined directly from load–displacement (P–δ) data without crack length measurement. The crack tip opening displacement in mode I (\( w_{\text{I}} \)) is determined by post-processing the displacements at the initial crack tip determined from digital image correlation. \( G_{\text{I}} \) and \( w_{\text{I}} \) are then combined for the direct identification of the cohesive law, \( \sigma_{\text{I}} = {\text{f}}(w_{\text{I}} ) \), which is assumed in cohesive zone modelling. Experimentally, crack propagation consistently occurs in the earlywood layer. The increase of \( M_{\text{e}} \) does not show any influence on the initiation stage of the fracture process zone. However, a statistical correlation exists for the critical (\( G_{\text{I,max}} \)) and at maximum load (\( G_{{{\text{I,}}P_{ \hbox{max} } }} \)) values of \( G_{\text{I}} \) with regard to \( M_{\text{e}} \). Consistently, the area under the identified cohesive curve increases with \( M_{\text{e}} \), although high scatter and low correlation between maximum cohesive strength (\( \sigma_{\text{Iu}} \)) and \( M_{\text{e}} \) are observed. The methodology is also validated using finite element analysis including cohesive elements and taking into account the growth rings heterogeneity. The numerical results show that the identification of the cohesive law is insensitive to the variability of the growth ring structure observed experimentally.