Transition Wood Research Articles

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 Variation Patterns in Xylem Vessels and Parenchyma Cells and Their Association with Tree Evolution

Xylem vessels and parenchyma cells perform functions such as water transport and nutrient storage in trees. However, they are highly variable in different trees. Therefore, this study aimed to explore the structural change patterns in vessels and parenchyma cells in the sapwood, transition wood, and heartwood of tree species with different degrees of evolution. The structural characteristics of the two types of cells in the sapwood, transitional wood, and heartwood were measured in six species with different levels of evolution, namely, Michelia macclurei Dandy, Cinnamomum camphora (L.) presl, Erythrophleum fordii Oliv, Melaleuca leucadendron L., Parashorea chinensis Wang Hsie and Tectona grandis L.F. The results showed that the more evolved species had larger earlywood vessel lumen diameters, thicker walls, and wider hydraulic diameters, as well as smaller latewood vessel densities, reflecting better water transport effectiveness and higher safety. From the sapwood to the transition wood and heartwood, the earlywood vessel lumen diameter of the more primitive species tended to be stable and then decrease, while that of the more evolved species gradually decreased. The latewood vessel density of the more primitive species tended to be stable and then increase, while that of the more evolved species tended to be stable. Additionally, the starch grains of the more primitive species were mainly distributed in the axial or ray parenchyma cells of the sapwood, while those of the more evolved species were abundantly distributed in the axial and ray parenchyma cells of the sapwood, and the distribution of the starch grains was reduced in the transition wood and heartwood. From the sapwood to the heartwood, the ray parenchyma cell fraction tended to be stable in the more primitive species, and tended to be stable before decreasing in the more evolved species. The pit density in the horizontal wall of the ray parenchyma cells tended to be stable and decrease in the more primitive species, while in the more evolved species it tended to be stable or decrease before stabilizing. Overall, trees’ vessels have gradually undergone the optimal selection of vessels during evolution, and the structural variation in the parenchyma cells contributes to their nutrient storage and transport.

Repellent properties against four Ascomycota species and Reticulitermes flavipes of acetonic extractives from Cedrus atlantica sapwood to inner heartwood fractions

Cedrus atlantica is a tree species present in the south of France which, in the context of climate change, could become a conservation priority in the coming years. This tree species is also of considerable ecological and socio-economic interest in the Mediterranean Basin area, where it is mainly recognized for its durable timber, and also for the potentially interesting chemical properties of its essential oil. Studies of its heartwood formation and the properties of its extractives are therefore of interest, although very few have been conducted so far. The radial distribution of water/acetone extractives within the Atlas cedar tree (bark, sapwood, transition wood, outer heartwood and inner heartwood) selected for this study was screened at different tree height levels. High-performance liquid chromatography (HPLC) analyses were performed, especially to characterize flavonoid compounds in these extractive fractions. The radial variation of the extractive composition obtained highlights the phenomenon of heartwood formation. Assumptions were put forward as to the metabolic pathways involved in the heartwood formation process of cedar wood, based in particular on the occurrence and radial evolution of (-)-catechin, (+)-taxifolin and flavan compounds. The fungicidal and termite-repellent activities of the extracts were then tested. The water/acetone extractives from the Cedrus atlantica individual studied showed strong termite repellent activity and moderate antifungal activity against crop and fruit pathogens. Even though the sampling in this study was limited to a single tree, the results point to a potential for commercial use of Atlas cedar extractives as wood preservatives and/or as biocontrol products against pathogens of woody agricultural crops. Additional tests and chemical analyses will be carried out to confirm these interesting preliminary results.

BASIC DENSITY AND SCALING OF JUVENILE AND MATURE WOOD IN PINUS CARIBAEA TREES

"The objective of the present study was to evaluate the density, and delimit the transition age and the volume proportion of wood types in Pinus caribaea trees. Trees from two genetic materials (A and B) were selected from a 20-year-old P. caribaea plantation. Disks from the base were used to determine the age of wood segregation and disks from different axial position – to determine the basic density and volume of juvenile, transition and mature wood in the trees. The density of the wood decreased from the base to the tree top. The juvenile wood corresponded to the beginning of the cambium activity until the eighth ring, the rest being characterized as transition wood and no mature wood was found in the 20-year-old P. caribaea trees. The proportion of juvenile wood volume in the genetic materials A and B was 58.57% and 80.51%. Transition wood was found up to 17.3 meters height of the trees."

Non-destructive determination of core-transition-outer wood of Pinus nigra combining FTIR spectroscopy and prediction models

The early detection of wood quality by using advanced analytical non-destructive methods is an ongoing area of research and is highly interesting for the forest-based sector. The presence of core wood has negative effects on the performance of this material; hence, it is essential to identify this region as well as to define the endpoint where the region defined as transition wood begins. The purpose of this study was to apply a novel methodology for wood quality classification, based on FTIR spectroscopy, in combination with chemometrics, generating models capable of differentiating and predicting core wood, transition, and outer wood of Pinus nigra. This study also attempts to classify which specific IR bands define the chemical differentiation of woody regions. The results of the predictive models generated were satisfactory, attaining a full identification of classes with a non-linear SVM-DA model showing higher correlation coefficients than the generated linear SIMCA and PLS-DA models. SIMCA and PLS-DA were suitable for bands contrast and for categorizing the IR fingerprint in relation to the core-transition-outer regions. This study presents discriminative models generated from a non-destructive and relatively fast IR methodology with high correlation coefficients, thus improving the existing methods that are currently practiced for identifying wood quality. However, the database requires progressive calibration and adjustments to have acceptable reliability when validating the methods over time.

Diversifying Forest Landscape Management—A Case Study of a Shift from Native Forest Logging to Plantations in Australian Wet Forests

Natural forests have many ecological, economic and other values, and sustaining them is a challenge for policy makers and forest managers. Conventional approaches to forest management such as those based on maximum sustained yield principles disregard fundamental tenets of ecological sustainability and often fail. Here we describe the failure of a highly regulated approach to forest management focused on intensive wood production in the mountain ash forests of Victoria, Australia. Poor past management led to overcutting with timber yields too high to be sustainable and failing to account for uncertainties. Ongoing logging will have negative impacts on biodiversity and water production, alter fire regimes, and generate economic losses. This means there are few options to diversify forest management. The only ecologically and economically viable option is to cease logging mountain ash forests altogether and transition wood production to plantations located elsewhere in the state of Victoria. We outline general lessons for diversifying land management from our case study.

LATERAL GROWTH AFFECTS XYLEM MATURATION PROPERTIES OF 8-YEAR-OLD BIG-LEAF MAHOGANY (SWIETENIA MACROPHYLLA)

The area of juvenile wood zone of an 8-year-old planted big-leaf mahogany (Swietenia macrophylla) was uniform regardless of diameter. Hence, it was assumed that xylem maturation is dependent on diameter. Radial distribution patterns with reference from the pith exhibited short fibre and vessel lengths, narrow vessel width and low xylem density, and exhibited gradual increase outward and became more or less stable near the bark. However, the radial distribution patterns of fibre width and modulus of elasticity were scattered regardless of tree diameter sizes. Fibre length, vessel length, vessel width and xylem density of the juvenile wood zones showed significant differences compared with the transition and mature wood zones. However, no significant difference was observed between transition wood zone and mature wood zone except for fibre length. A negative correlation was observed in fibre length, vessel length, vessel width and xylem density in terms of their relationship with diameter at breast height and the radial distribution of fibre (i.e. b-value), and the diameter boundaries of the three wood zones. At diameters 18.08, 17.36, 16.23 and 17.87 cm respectively, fibre length, vessel length, vessel width and xylem density can be used to identify xylem maturation boundary.

Radial Variation of Wood Anatomical Properties Determines the Demarcation of Juvenile-Mature Wood in Schima superba

Schima superba is a precious broadleaf tree species that produces excellent timber. Analyzing the radial variation of wood anatomical properties within stems and determining the boundary between the juvenile and mature wood can provide a theoretical basis for the breeding and cultivation of S. superba. Herein, 30 54-year-old trees were used to analyze the radial variation of wood anatomical properties qualitatively. The correlation among wood properties was analyzed. On this basis, four types of model were used to predict the wood properties quantitatively, and the optimal segmentation model was used to determine the boundary between juvenile and mature wood. The results showed that the variation of the early stage (before the 20th year) was larger than that of the later stage (after the 20th year); moreover, the variation of the vessel features (9.56%) was greater than that of the fiber features (7.42%), the vessel lumen diameter (11.94%) and the fiber length (8.00%) had the most variation. There were three radial variation patterns in the wood properties. In the early stage, there was a significant positive correlation between the ring width and wood air-dry density (0.78) and wood basic density (0.89), and a significant negative correlation between the ring width and the fiber characters (−0.79~−0.93) and vessel characters (−0.64~−0.90). The growth models of Logistic and Richards were more suitable (R2 = 84.2%~95.2%) for the radial variation of wood anatomical properties than the nonlinear least square model (R2 = 67.7%~90.9%). The transition wood between juvenile and mature wood of S. superba was from the 11th to the 16th year based on aggregative indicators from the pith to bark at breast height. Finally, when taken together, the wood anatomical properties of S. superba had regular radial variation. Breeding programs need to consider both growth and wood anatomical properties in the early stage, but they can be neglected in the mature stage. The formation of mature wood of S. superba occurred after the 16th year.

Sifat fisik dan mekanik kayu randu (Ceiba pentandra L. Gaerner) terdensifikasi dari hutan rakyat [Physical and mechanical properties of densified randu wood (Ceiba pentandra L. Gaerner) from community forest

Kapok wood has high potential availability of wood. Although, the weakness is its low quality. However, kapok wood quality can be improved by compaction technology. This research aims to improve the physical and mechanical properties of wood with wood compaction technology, and to determine the effect of variations in the horizontal position of trees and the length of steaming on the mechanical properties of compacted wood. The method used was compaction method with steaming treatment. The study used three types of wood method variations, namely terrace wood, transition wood and sapwood and four types of treatment with steaming duration of 30 minutes, 60 minutes, 90 minutes and without steaming. Wood testing on the physical properties of wood was guided by JIS Z 2102 (1957) and JIS Z 2103 (1957), while the mechanical properties of wood testing was guided by JIS Z 2113 (1963). Research showed that compaction on stretched wood with a target thickness of upto 2 cm improved the physical and mechanical properties of compacted wood. Steaming treatment prior to pressing for 90 minutes was effective in improving the mechanical properties of wood. The mechanical properties values improved by the increasing time of the steaming time before pressing the wood. The variation of wood position/parts affect the enhancement of the mechanical properties of wood in the parallel compressive strength test.

Within-ring variability of wood structure and its relationship to drought sensitivity in Norway spruce trunks

ABSTRACTRelationships between hydraulic vulnerability expressed asP50(the air pressure causing 50% loss of hydraulic conductivity) and within-ring differences in wood density (WD) and anatomical features were investigated with the aim to find efficient proxies forP50relating to functional aspects. WD and tracheid dimensions were measured with SilviScan on Norway spruce (Picea abies(L.) Karst.) trunk wood.P50was strongly related to mean WD (r= -0.64) and conduit wall reinforcement ((t/b)2), the square of the ratio between the tracheid double wall thickness (t) and the lumen width (b), where use of tangential lumen width ((t/bt)2) gave better results (r= -0.54) than radial lumen width (r= -0.31). The correlations ofP50with earlywood (EW), transition wood (TW) and latewood (LW) traits were lower than with the specimen averages, both for WD (r= -0.60 for WDEW,r= -0.56 for WDTW,r= -0.23 for WDLW) and all anatomical traits. The loss of hydraulic conductivity was addressed as a dynamic process and was simulated by defining consecutive phases of 5% theoretical conductivity loss. WD and tracheid traits were calculated and correlated withP50values of each specimen. Tightest correlations were found for (t/bt)2, at relative cumulated theoretical conductivities until 45 to 50% (r= -0.75).We conclude that WD is one of the best available proxies forP50, but does not necessarily reflect the mechanism behind resistance to cavitation. The new trait, based on estimation of conductivity loss as a dynamic process, provided even stronger correlations.

Effects of Drought on Xylem Anatomy and Water-Use Efficiency of Two Co-Occurring Pine Species

Exploring how drought influences growth, performance, and survival in different species is crucial to understanding the impacts of climate change on forest ecosystems. Here, we investigate the responses of two co-occurring pines (Pinus nigra and Pinus sylvestris) to interannual drought in east-central Spain by dendrochronological and wood anatomical features integrated with isotopic ratios of carbon (δ13C) and oxygen (δ18O) in tree rings. Our results showed that drought induces both species to allocate less carbon to build tracheid cell-walls but increases tracheid lumen diameters, particularly in the transition wood between early and latewood, potentially maximizing hydraulic conductivity but reducing resistance to embolism at a critical phase during the growing season. The thicker cell-wall-to-lumen ratio in P. nigra could imply that its xylem may be more resistant to bending stress and drought-induced cavitation than P. sylvestris. In contrast, the higher intrinsic water-use efficiency (iWUE) in P. sylvestris suggests that it relies more on a water-saving strategy. Our results suggest that narrower cell-walls and reduced growth under drought are not necessarily linked to increased iWUE. At our site P. nigra showed a higher growth plasticity, grew faster and was more competitive than P. sylvestris. In the long term, these sustained differences in iWUE and anatomical characters could affect forest species performance and composition, particularly under increased drought stress.

Dendrochronology of maritime pine in the middle of the Atlantic Ocean

The Azores Archipelago, located in the North Atlantic Ridge, experiences heavy rainfall and mild temperatures with weak seasonal differences due to oceanic influence. To our knowledge, there have been no dendrochronological studies in the Azores. The aim of this study is to explore the dendrochronological potential of Pinus pinaster Ait. growing in this archipelago and to determine what limiting factor is regulating tree growth. To do so, we have sampled adult maritime pine trees growing in a plantation, in the Pico island of the Azores.Tree ring boundaries were not always easily distinguished, suggesting that in some years cambial activity did not stop during winter. Despite this, it was possible to successfully crossdate the tree-ring series and to establish a tree-ring width chronology with a strong common signal. Climatic correlations revealed a positive response to spring precipitation but no temperature signal in the tree-ring width chronology. Tree-ring width was also negatively correlated with the North Atlantic Oscillation (NAO) and the sea level pressure (SLP) in May − June.Intra-annual density fluctuations (IADFs), which are anatomical features formed in response to variations in environmental conditions during the growing season, were present in 85% of the tree rings. IADFs were identified based on its position within the ring: type E+, characterized as a transition wood from early- to latewood; type L, the most frequent, characterized as earlywood-like cells within latewood; and type L+, characterized as earlywood-like cells between latewood and earlywood of the next tree ring. Each IADF type presented a unique climatic signal: type E+ was positively correlated with early summer precipitation and early spring temperature; type L was positively correlated with early autumn precipitation and temperature; and type L+ was positively correlated with late autumn precipitation.In conclusion, the tree-ring width chronology established for maritime pine growing in the Pico Island of Azores contains a clear climatic signal for spring precipitation, whereas IADFs frequency correlated better with precipitation later in the growing season. For this reason, we suggest that IADFs should be included in future dendrochronological studies in the Macaronesia Biogeographical region since they can improve the climatic signal present in tree-ring width chronologies.

Anatomical properties of Eucalyptus grandis wood and transition age between the juvenile and mature woods

The present study is aimed at evaluating the anatomical characteristics of Eucalyptus grandis wood and the transition age between the juvenile and mature woods. Four trees of 23-year-old E. grandis were used. The juvenile, transition and mature wood zones were found by fiber length measurement from the pith to the bark. Samples were taken from juvenile wood, transition wood and mature wood and the anatomical properties of the wood were determined. The results showed that: (1) the fiber length, cell wall thickness, slenderness ratio, cell wall fraction and tangential vessel diameter increase from pith to bark; (2) fibers, axial parenchyma, ray parenchyma cells and vessels are equally distributed from pith to bark; (3) the transition zone between juvenile and mature wood occurs between the age of 8 and 13 years.

Variation in Wood Quality in White Spruce (Picea Glauca (Moench) Voss). Part I. Defining the Juvenile–Mature Wood Transition Based on Tracheid Length

Estimations of transition age (TA) and juvenile wood proportion (JWP) are important for wood industries due to their impact on end-product quality. However, the relationships between analytical determination of TA based on tracheid length (TL) and recognized thresholds for adequate end products have not yet been established. In this study, we used three different statistical models to estimate TA in white spruce (Picea glauca (Moench) Voss) based on TL radial variation. We compared the results with technological maturity. A two-millimeter threshold, previously suggested for good paper tear strength, was used. Tracheid length increased from pith to bark and from breast height to upper height. Juvenile wood (JW) was conical with the three models. At breast height, TA ranged from 11 to 27 years and JWP ranged from 15.3% to 47.5% across the three models. The linear mixed model produced more conservative estimates than the maximum-quadratic-linear (M_Q_L) model. Both the linear mixed model and the M_Q_L model produced more conservative TA estimates than the piecewise model. TA estimates by the MIXED model, and to a lesser extent by the M_Q_L model, were equivalent to those for real mature wood, whereas TA estimates by the piecewise model were considerably lower, falling into the transition wood area.

Collapse of Eucalyptus nitens Wood After Drying Depending on the Radial Location Within the Stem

Collapse is almost certain to occur in the industrial drying of Eucalyptus nitens and, as such this prevents the lumber manufacturing industry in Chile from producing commercial solid wood products from this species. This problem is still unsolved, and different studies to reduce collapse are currently underway. In this exploratory study, shrinkage and collapse after drying of Eucalyptus nitens was measured for boards cut from different radial locations within the stem (core, transition, and outer wood from pith to bark) and having different annual ring orientations (flat-sawn and quarter-sawn). Though exploratory, the results appear to confirm that pieces that were cut from the center of the trees were less susceptible to collapse than pieces cut from the transition zone between the center and the periphery. On average, collapse in transition wood was approximately 50% higher than the collapse observed in wood cut from the central zone of the trees.

Tree heights in the ring-formed years affect microfibril angles in the rings from juvenile to mature wood at breast height in hinoki trees (Chamaecyparis obtusa)

In this study, we examined past growth traits of hinoki (Chamaecyparis obtusa) trees by stem analysis, as well as growth traits in the years when the rings at breast height were formed. We tried to clarify the effects of growth traits in the ring-formed years on the wood properties of the rings from juvenile to mature wood. Height to diameter ratio (H/D) had a larger correlation coefficient in relation to stem stiffness than tree height or diameter at breast height (DBH). The longitudinal variation in stiffness of logs, except for first and top logs, in each tree was assumed to be constant with the height position in the trunk. Tree height in the ring-formed year had a significant negative effect on microfibril angle (MFA) near the pith, in transition wood, and in mature wood. DBH in the ring-formed year had a significant negative effect on density in mature wood. We concluded that the effects of tree height on MFA and of DBH on density produced the effect of H/D on stem stiffness of the trunk. Greater tree height in younger age may contribute to the improvement of juvenile wood properties.

Palatability of Field-Collected Eastern Redcedar,Juniperus virginianaL., Components to Subterranean Termites (Isoptera: Rhinotermitidae)

Feeding bioassays were conducted to evaluate relative palatability of three different components of eastern redcedar (ERC) wood to the subterranean termite, Reticulitermes flavipes Kollar. Sections of fresh-cut ERC trunk were separated into three component groups: heartwood, sapwood, and ‘transition wood’ (sapwood-heartwood interface). Wooden blocks cut from these groups, as well as pine sapwood (control), were used in ‘choice’ and ‘no-choice’ bioassays. Half of each group was oven-dried while the other half was air-dried. In choice bioassays, pine sustained significantly greater weight loss compared with the air-dried ERC groups. Weight loss for air-dried ERC sapwood was significantly greater compared with both air-dried heartwood and transition wood. In no-choice bioassays, air-dried sapwood and pine sustained the greatest weight losses. Termite worker survival on pine (86.6 ± 2.6%) was significantly greater compared with both oven-dried sapwood (73.2 ± 4.2%) and air-dried sapwood (70.9 ± 3.2%), which were significantly greater than oven-dried transition wood (53.3 ± 4.2) and oven-dried heartwood (38.6 ± 6.5%). Overall, both oven-dried and air-dried heartwood were least palatable to termites.

High negative genetic correlations between growth traits and wood properties suggest incorporating multiple traits selection including economic weights for the future Scots pine breeding programs

The development of multiple trait selection indices for solid (structure) wood production in the Scots pine (Pinus sylvestris L.) breeding program requires genetic variances and covariances estimated among wood quality traits including stiffness. Genetic control and relationships among Scots pine growth, fiber, and wood quality traits were assessed by estimating heritability, phenotypic and genetic correlation using a Scots pine full-sib family trial. Wood quality traits including clearwood and dynamic acoustic stiffness were measured using SilviScan and Hitman in a 40-year-old progeny trial and by sampling increment cores of 778 trees of 120 families. Genetic parameters were estimated using the mixed model by the ASReml software. Heritability ranged from 0.147 to 0.306 for growth, earlywood, transition wood and latewood proportion traits and from 0.260 to 0.524 for fiber dimension, wood density, MFA and stiffness traits. The highly unfavorable genetic correlation between diameter and whole core density (−0.479) and clearwood stiffness (−0.506) and dynamic acoustic stiffness (−0.382) was observed in this study. The unfavorable genetic correlations between growth traits and stiffness indicate that multiple traits selection using optimal economic weights and optimal breeding strategies are recommended for the advanced Scots pine breeding program.

Changes in the properties of wood cell walls during the transformation from sapwood to heartwood

Changes in the chemical, viscoelastic and hygroscopic properties of wood cell walls in Chinese fir (Cunninghamia lanceolata) during the transition from sapwood to heartwood were studied to provide insights into the formation of heartwood. In situ imaging FTIR measurements indicated that the composition of the main components of cell walls remained almost unaltered, but more extractives were deposited in the wood cell walls during the sapwood–heartwood transition. Compared to the sapwood and transition wood, the heartwood had a higher softening temperature and greater activation energy, suggesting that the mobility restrictions of cell wall biopolymers were due to extractives obstructing the accessing of the plasticizer (ethylene glycol). The moisture sorption was the same from the sapwood to heartwood at a low relative humidity (RH), while the heartwood adsorbed less water at a high RH, probably caused by the extractives deposited in the matrix and mesopores of heartwood cell walls.

Full-field moisture induced deformation in Norway spruce: intra-ring variation of transverse swelling

The transverse hygro-expansion of Norway spruce wood is studied on the growth ring level using digital image correlation. This non-destructive technique offers the possibility for a contactless study of deformation fields of relatively large areas. The measured full-field strains are segmented into individual growth rings. Whereas radial strains closely follow the density progression with the maximum in the dense latewood (LW), tangential and shear strain remain constant except for positions around the edges of the sample. A simple FE three phase growth ring model is in good agreement with the experimental values. The selective activation of individual phases like earlywood (EW), transition wood and LW demonstrates that the radial hygro-expansion is dominated by the EW deformation, whereas tangential deformation is a complex interplay of expansion and compression that needs all tissues to fully develop.