Selecting earlywood vessels to maximize their environmental signal

The anatomical features of earlywood vessels often reflect information about past climatic conditions. We examined the relationships between mean monthly temperature and mean vessel lumen area (MVA) in various categories of earlywood vessels. Subsets of earlywood vessels of chestnut (Castanea sativa Mill.) were selected from a previously reported dataset based on several progressive size-related procedures. To include all earlywood vessels, the minimum size considered was 10,000 microm2. Changes in the correlations between MVA and the mean air temperature in March are described and discussed. The results show that not all vessels embody the same information. The MVA of a proportion of the largest earlywood vessels in each annual ring was most closely related to March temperature, whereas MVA of the smallest earlywood vessels was better correlated with June temperature. This difference is probably a result of the vessels being formed at different times: early spring for the largest earlywood vessels and later in spring for the smallest earlywood vessels. Analyses combining large and small vessels yielded lower correlations between MVA and monthly temperature. The number, size and distribution of vessels can vary greatly from ring to ring. In making year-to-year comparisons, the best information is provided by observations on vessels of contemporaneous ontogenesis. Criteria for the selection and analysis of vessels in the assessment of temperature during the season of wood formation are proposed and discussed.     

Influence of drought on tree rings and tracheid features of Pinus nigra and Pinus sylvestris in a mesic Mediterranean forest

We investigated the influence of climate on the ring width and xylem anatomy of two co-occurring pines (Pinus nigra Arn. and P. sylvestris L.) in the mountains of east-central Spain in order to test their utility for dendroclimatic reconstructions. We developed chronologies of ring width, mean lumen diameter and mean cell-wall thickness (in the earlywood, latewood, and the total annual ring) and the number of cells between 1960 and 2006. Drought, expressed as the standardized precipitation-evapotranspiration index (SPEI), was the main climatic driver of tree radial growth, although trees were also sensitive to temperature (negative effect in previous autumn and current summer) and precipitation (with a general positive effect). P. sylvestris response was stronger to climate of the current year, whereas the effect of previous-year climate was more important for P. nigra. Warm and dry summers reduced ring width, tracheid lumen, and wall thickness in both species, whereas warm winter-spring temperatures had the opposite effect, primarily for P. sylvestris. Previous-year or early-season conditions mainly affected earlywood features, whereas latewood was more responsive to summer climate. Overall, climate appeared to be a stronger limiting factor for P. sylvestris. During periods of drought, cell-wall thickness was reduced while lumen width increased in the latewood of P. sylvestris. This could compromise its hydraulic safety against drought-induced cavitation as our site was close to the southern and dry edge of the species distribution area. Our results suggest that anatomical variables record different and stronger climate information than ring width variables, especially in P. sylvestris. Reconstruction models for SPEI at the 3-month scale were developed for July–August and September–October using principal components regression. The best models included anatomical and width variables of both pine species suggesting that tracheid chronologies can be useful for drought reconstructions especially at mesic sites or with species that encode a mixed drought and temperature-precipitation signal.     

Elevated temperature and CO(2) concentration effects on xylem anatomy of Scots pine

We studied the effects of elevated temperature and carbon dioxide concentration ([CO(2)]) alone and together on wood anatomy of 20-year-old Scots pine (Pinus sylvestris L.) trees. The study was conducted in 16 closed chambers, providing a factorial combination of two temperature regimes and two CO(2) concentrations (ambient and elevated), with four trees in each treatment. The climate scenario included a doubling of [CO(2)] and a corresponding increase of 2-6 degrees C in temperature at the site depending on the season. Anatomical characteristics analyzed were annual earlywood, latewood and ring widths, intra-ring wood densities (earlywood, latewood and mean wood density), tracheid width, length, wall thickness, lumen diameter, wall thickness:lumen diameter ratio and mass per unit length (coarseness), and numbers of rays, resin canals and tracheids per xylem cross-sectional area. Elevated [CO(2)] increased ring width in four of six treatment years; earlywood width increased in the first two years and latewood width in the third year. Tracheid walls in both the earlywood and latewood tended to become thicker over the 6-year treatment period when temperature or [CO(2)] was elevated alone, whereas in the combined treatment they tended to become thinner relative to the tracheids of trees grown under ambient conditions. Latewood tracheid lumen diameters were larger in all the treatments relative to ambient conditions over the 6-year period, whereas lumen diameters in earlywood increased only in response to elevated [CO(2)] and were 3-6% smaller in the treatments with elevated temperature than in ambient conditions. Tracheid width, length and coarseness were greater in trees grown in elevated than in ambient temperature. The number of resin canals per mm(2) decreased in the elevated [CO(2)] treatment and increased in the elevated temperature treatments relative to ambient conditions. The treatments decreased the number of rays and tracheids per mm(2) of cross-sectional area, the greatest decrease occurring in the elevated [CO(2)] treatment. It seemed that xylem anatomy was affected more by elevated temperature than by elevated [CO(2)] and that the effects of temperature were confined to the earlywood.     

Relationships of climate and cell features in stems and roots of black spruce and balsam fir

? The anatomical differences of mature black spruces and balsam firs were examined at stem and root level in order to characterize their wood properties at cellular level and link these differences to climate.

? Anatomical variability of these species was evaluated in relation to climate data gathered from 2001 to 2004 during the cell enlargement (CE) and wall thickening and lignification (WTL) phases. Lumen area, single cell wall thickness and total tracheid radial diameter were analyzed and regrouped into earlywood and latewood.

? Results from a principal component analysis (PCA) indicated that both first eigenvectors account for 82% and 90% of total variance for CE and WTL respectively. These component factors revealed that precipitation, humidity and number of days with precipitation significantly influence the lumen area (p = 0.0168) and radial cell diameter (p = 0.0222) in earlywood. Significant differences were registered between species and tree parts (stem and root) for the lumen area, radial cell diameter and cell wall thickness in both earlywood and latewood.

? In our study, black spruce exhibited smaller tracheid size in both stem and roots compared to balsam fir. Furthermore, the lower amount of tracheids produced during the growing season and higher proportion of latewood ensure a higher wood density of black spruce. The influence of temperature on earlywood formation is significant, whereas no influence was observed on latewood.

     

Cavitation in dehydrating xylem of Picea abies: energy properties of ultrasonic emissions reflect tracheid dimensions

Ultrasonic emission (UE) testing is used to analyse the vulnerability of xylem to embolism, but the number of UEs often does not sufficiently reflect effects on hydraulic conductivity. We monitored the absolute energy of UE signals in dehydrating xylem samples hypothesizing that (i) conduit diameter is correlated with UE energy and (ii) monitoring of UE energy may enhance the utility of this technique for analysis of xylem vulnerability. Split xylem samples were prepared from trunk wood of Picea abies, and four categories of samples, derived from mature (I: earlywood, II: 30-50% latewood, III: >50% latewood) or juvenile wood (IV: earlywood) were used. Ultrasonic emissions during dehydration were registered and anatomical parameters (tracheid lumen area, number per area) were analysed from cross-sections. Attenuation of UE energy was measured on a dehydrating wood beam by repeated lead breaks. Vulnerability to drought-induced embolism was analysed on dehydrating branches by hydraulic, UE number or UE energy measurements. In split samples, the cumulative number of UEs increased linearly with the number of tracheids per cross-section, and UE energy was positively correlated with the mean lumen area. Ultrasonic emission energies of earlywood samples (I and IV), which showed normally distributed tracheid lumen areas, increased during dehydration, whereas samples with latewood (II and III) exhibited a right-skewed distribution of lumina and UE energies. Ultrasonic emission energy was hardly influenced by moisture content until ～40% moisture loss, and decreased exponentially thereafter. Dehydrating branches showed a 50% loss of conductivity at -3.6 MPa in hydraulic measurements and at -3.9 and -3.5 MPa in UE analysis based on cumulative number or energy of signals, respectively. Ultrasonic emission energy emitted by cavitating conduits is determined by the xylem water potential and by the size of element. Energy patterns during dehydration are thus influenced by the vulnerability to cavitation, conduit size distribution as well as attenuation properties. Measurements of UE energy may be used as an alternative to the number of UEs in vulnerability analysis.     

Variation of measured cross-sectional cell dimensions and calculated water vapor permeability across a single growth ring of spruce wood

A statistical study of the cell dimensions in a growth ring of spruce along the radial and tangential directions is performed. The data are used to study the variation of the cell vapor permeability in the growth ring. Studying cell rows within one growth ring, the frequency distributions of the cell wall thickness in the radial direction and of the lumen dimension in the tangential direction are found to be both unimodal. In contrast, the frequency distributions of these dimensions in the other directions are bimodal, where the different modes can be attributed to earlywood and latewood. Analysis of the bimodal distributions results in the determination of threshold values of cell wall thickness and the lumen dimension for earlywood and latewood tracheids. The cell dimensions are used to predict cell porosity and water vapor permeability distribution within a growth ring. The bimodal frequency distributions of the tangential cell wall thickness and the radial lumen dimension provide an explanation for the observed bimodal frequency distribution of the cell water vapor permeability both in radial and in tangential directions. Contrary to measured macroscopic vapor permeability results, the tracheid geometry results in lower cell vapor permeability in radial than in tangential direction. This confirms that rays play an important role in the vapor permeability of wood, as they can be considered as pathways for vapor transport in radial direction. The dataset analyzed in this paper leads to a set of parameters characterizing the earlywood and latewood cell dimensions. Such characterization can be used, for example, for producing synthetic data for computational modeling studies.     

The anatomical traits of trunk wood and their relevance to oak (Quercus robur L.) vitality

Oaks’ decline in vitality is attributed to a complex process that involves interactions of several factors leading to increased trees’ mortality. This study investigates the structure of trunk wood of oaks with reference to its physiological role in hydraulic conductivity. On the basis of the crown condition, the oaks were classified into three health groups: healthy trees, declining trees and dead trees. Anatomical traits of wood, such as annual ring width, vessel density, vessel diameter of earlywood and theoretical hydraulic conductivity, were measured and calculated. The narrowest annual rings formed by the cambium were observed in dead oaks. These trees were also characterized by the smallest diameter of earlywood vessels, not only in the period of occurrence of dieback symptoms, but also during their whole life. It is suggested that the formation of narrow annual rings and earlywood vessels of small diameter increases susceptibility of a tree to decay. A reduced vessel diameter implies changes in hydraulic conductivity of oak trunks and thus impairs the water transport, which affects the health of trees. The process of oak decline is considered to have characteristics of natural selection and leads to the elimination of the weakest trees.     

广西柳州杉木种源树轮宽度对温度与湿度的年际响应

[目的]为选择适合试验区域未来气候变化条件下生长的杉木种源,[方法]运用年轮气候学方法,研究52个杉木地理种源3个树轮宽度指标对气候因子的响应。[结果]整轮宽度、早材宽度和晚材宽度与年平均气温的响应呈强负相关关系,相关系数最大值分别为-0.515、-0.590和-0.451;整轮宽度、早材宽度和晚材宽度与年最高气温均呈强负相关关系,相关系数最大值分别为-482、-0.624和-0.499。[结论]未来试点年平均气温有升高的趋势,这将会在一定程度上抑制杉木的径向生长,而选择对温度响应不太敏感的湖南江华、广西博白和广西资源种源在试验林所在区域进行造林,将是解决这一问题的有效途径。     

Response to climate changes in radial growth of Picea crassifolia in the Qilian mountains of northwestern China

In order to investigate the response to climate changes in radial growth of Picea crassifolia at the lower tree line in the middle Qilian mountains in northwestern China, relationships of standardized chronologies of annua ring, earlywood and latewood widths with mean monthly temperature and total monthly precipitation were analyzed by ways of correlation and pointer year analyses. The results show that annual ring, earlywood and latewood widths are significantly negatively correlated with mean monthly temperature in June and Juy. Annual ring and eadywooc widths are significantly and positively correlated with tOtal monthly precipitation in March, May and June and negatively correlated with total monthly precipitation in September. Latewood width is less sensitive to climate changes than the width of earlywood and insignificantly sensitive to precipitation. The results of pointer year analysis revealed that whet summer temperatures are higher than the mean summer temperature synchronization and the summer precipitatior lower than mean summer precipitation synchronization, narrow annual rings are formed. Wide annual rings are formec~ when summer temperatures are lower than the mean summer temperature synchronization and summer precipitation higher than mean summer precipitation synchronization. The results indicate that more precipitation in the spring and summer is helpful for radial growth while warmer summer restricts radial growth of P. crassifolia at the lower tree line in the middle Qilian mountains.     

Hydraulic and mechanical properties of young Norway spruce clones related to growth and wood structure

Stem segments of eight five-year-old Norway spruce (Picea abies (L.) Karst.) clones differing in growth characteristics were tested for maximum specific hydraulic conductivity (k(s100)), vulnerability to cavitation and behavior under mechanical stress. The vulnerability of the clones to cavitation was assessed by measuring the applied air pressure required to cause 12 and 50% loss of conductivity (Psi(12), Psi(50)) and the percent loss of conductivity at 4 MPa applied air pressure (PLC(4MPa)). The bending strength and stiffness and the axial compression strength and stiffness of the same stem segments were measured to characterize wood mechanical properties. Growth ring width, wood density, latewood percentage, lumen diameter, cell wall thickness, tracheid length and pit dimensions of earlywood cells, spiral grain and microfibril angles were examined to identify structure-function relationships. High k(s100) was strongly and positively related to spiral grain angle, which corresponded positively to tracheid length and pit dimensions. Spiral grain may reduce flow resistance of the bordered pits of the first earlywood tracheids, which are characterized by rounded tips and an equal distribution of pits along the entire length. Wood density was unrelated to hydraulic vulnerability parameters. Traits associated with higher hydraulic vulnerability were long tracheids, high latewood percentage and thick earlywood cell walls. The positive relationship between earlywood cell wall thickness and vulnerability to cavitation suggest that air seeding through the margo of bordered pits may occur in earlywood. There was a positive phenotypic and genotypic relationship between k(s100) and PLC(4MPa), and both parameters were positively related to tree growth rate. Variability in mechanical properties depended mostly on wood density, but also on the amount of compression wood. Accordingly, hydraulic conductivity and mechanical strength or stiffness showed no tradeoff.     

Refined pipe theory for mechanistic modeling of wood development

We present a mechanistic model of wood tissue development in response to changes in competition, management and climate. The model is based on a refinement of the pipe theory, where the constant ratio between sapwood and leaf area (pipe theory) is replaced by a ratio between pipe conductivity and leaf area. Simulated pipe conductivity changes with age, stand density and climate in response to changes in allocation or pipe radius, or both. The central equation of the model, which calculates the ratio of carbon (C) allocated to leaves and pipes, can be parameterized to describe the contrasting stem conductivity behavior of different tree species: from constant stem conductivity (functional homeostasis hypothesis) to height-related reduction in stem conductivity with age (hydraulic limitation hypothesis). The model simulates the daily growth of pipes (vessels or tracheids), fibers and parenchyma as well as vessel size and simulates the wood density profile and the earlywood to latewood ratio from these data. Initial runs indicate the model yields realistic seasonal changes in pipe radius (decreasing pipe radius from spring to autumn) and wood density, as well as realistic differences associated with the competitive status of trees (denser wood in suppressed trees).     

A Possible Indicator of Shake in Oak: Relationship between Flushing Dates and Vessel Sizes

Previous work by Savill (1986) has shown that oak trees (Quercusrobur and Q. petraea) with large earlywood vessels appear tohave a much greater predisposition to shake than trees withsmaller vessels. The aim of the investigation described herewas to determine whether there are any externally visible characteristicscorrelated with vessel size, so that shake-prone trees can berecognized in the field. It was found that trees that flushlatest within a population tend to have the biggest vessels.Possible reasons for this correlation are discussed briefly.The finding has the practical value that oaks which are predisposedto shake can be marked at flushing time and removed in thinningoperations.     

Maximum effective lumen and pit pore sizes of the earlywood and the latewood of never dried loblolly pine sapwood

Summary Measurements of the air pressure required to initially displace a saturating liquid and allow a slow continuous stream of air bubbles to pass through wood cross sections of different thickness, together with the equilibrium surface tension of the saturating liquid, make it possible to calculate the maximum effective opening radii. Previous measurements were made for wood as a whole over complete annual rings. Measurements reported here were made separately for earlywood and latewood. Extrapolating plots of the maximum effective opening radius-cross section thickness, for thicknesses below the maximum fiber length, to zero thickness gave maximum lumen radii of 16 m for the earlywood and 10.3 m for the latewood. The values are only slightly greater than the calculated average values. Extrapolating the plots in the opposite direction to zero opening radius gave approximate maximum lumen or fiber lengths for the earlywood of 6 mm and for the latewood of 5 mm. The maximum effective opening radii for cross sections thicker than the maximum fiber length give maximum effective communicating pore radii. These values continue to decrease, with increasing thickness of the cross sections due to the decreasing probability of the largest openings falling in any one series path through the structures. The maximum effective pit pore radius for passage through fifty pits in series was 0.8 m for the earlywood and 0.28 m for the latewood.Paper No. 3787 of the Journal Series of North Carolina State University Agricultural Experiment Station, Releigh, N. C.     

Xylem hydraulic adjustment and growth response of Quercus canariensis Willd. to climatic variability

Global change challenges forest adaptability at the distributional limit of species. We studied ring-porous Quercus canariensis Willd. xylem traits to analyze how they adjust to spatio-temporal variability in climate. Trees were sampled along altitudinal transects, and annual time series of radial growth (ring width (RW)) and several earlywood vessel (EV) traits were built to analyze their relationships with climate. The trees responded to increasing water constraints with decreasing altitude and changes in climate in the short term but the analyses showed that xylem did not acclimate in response to long-term temperature increase during the past 30 years. The plants' adjustment to climate variability was expressed in a different but complementary manner by the different xylem traits. At low elevations, trees exhibited higher correlations with water stress indices and trees acclimated to more xeric conditions at low elevations by reducing radial growth and hydraulic diameter (D(H)) but increasing the density of vessels (DV). Average potential conductivity (K(H)) was similar for trees at different altitudes. However, inter-tree differences in xylem traits were higher than those between altitudes, suggesting a strong influence of individual genetic features or micro-site conditions. Trees exhibited higher RW those years with larger D(H) and particularly the linear density of vessels (DV(l)), but partly, climatic signals expressed in RW differed from those in EVs. Trees produced larger D(H) after cold winters and wet years. Ring width responded positively to wet and cool weather in fall and spring, whereas the response to climate of DV and K(H) was generally opposite to that of RW. These relationships likely expressed the negative impact of high respiration rates in winter on the carbon pools used to produce the EVs in the next spring and the overall positive influence of water availability for trees. Our results showed that trees at different sites were able to adjust their hydraulic architecture to climatic variability and temperature increase during recent decades coordinating several complementary traits. Nonetheless, it should be monitored whether they will succeed to acclimate to future climatic scenarios of increasing water stress.     

Dry matter content during extension of twigs,buds and leaves reflects hydraulic status related to earlywood vessel development in <Emphasis Type="Italic">Quercus pyrenaica</Emphasis> Willd.

A quantitative method was tested to describe crown phenophases in relation to water content and to secondary growth in ring-porous species, based on the hypothesis that new shoots require hydrated tissues to maintain the necessary turgor for extension, leading to a reduction in dry matter content (DMC). We collected a three-year-old branch from 11 Quercus pyrenaica Willd. trees at 10-day intervals to estimate DMC of newly developing buds, leaves, and twigs, and processed two opposite stem microcores for xylogenesis. Branch phenophases and shoot length were recorded in the field. The DMC of all organs decreased during crown development, with a minimum in early June, followed by a gradual increase up to initial values in late September. The shoot extension period concurred with the lowest DMC, but also with the beginning of earlywood maturation in the main stem, suggesting a high tissue hydration only when earlywood vessels become functional to fulfill enough water requirements for shoot and leaf extension. These results confirm the usefulness of DMC to accurately quantify the phenology of primary growth from bud swelling up to full leaf extension, as a complement to qualitative methods. This variation in DMC appears to be linked to secondary growth as a result of earlywood vessel development.     

Predicting anisotropic shringkage of softwood Part 1: Theories

 The phenomenon of wood shrinkage by losing moisture can be analysed at four levels: molecular, ultrastructural, microstructural and macrostructural levels. To predict the shrinkage of wood cells, the model of Barber and Meylan is modified in the current work to reflect combined effects of shrinkage of the cell wall, changes of the lumen shape and effects of rays and bordered pits. Where a piece of wood contains a multi-layer of earlywood and latewood or multi-layer of normal and defect wood with variable properties, a model is proposed to relate the total, measurable shrinkage to the shrinkage of each layer. The model can be applied to a specimen with asymmetric properties through the thickness. In such a board, bow (or crook), cup and twist are often observed. The modified and proposed models involve several mechanical properties of the cell wall which are difficult to measure. These properties vary with wood types, such as earlywood, late wood, compression wood, or wood with spiral grain. However, an alternative method may be used to obtain these properties from experimentally measured shrinkage data, and this method will be presented in a subsequent paper. Received 25 January 1999     

Variations and correlations of various ring width and ring density features in European oak: implications in dendroclimatology

Summary Variations and correlations of various ring width and ring density features were analyzed in 18 European oak (Quercus petraea andQuercus robur) trees from northeastern France. In light of these analyses, the goodness of various tree-ring features as a climatic parameter was discussed. In general, ring density features (viz. earlywood density, latewood density, average ring density, minimum density and maximum density) show a stronger response to calendar year, a comprehensive climatic variable, than ring width features (viz. earlywood width, latewood width, total ring width and latewood percent). The response of latewood features (viz. latewood width, latewood density and maximum latewood density) is stronger than that of earlywood features (viz. earlywood width, earlywood density and minimum earlywood density). Average ring density seems to be the most sensible tree-ring feature in European oak in terms of the response to calendar year. Moreover, total ring width as a climatic parameter is not as good as latewood width, and maximum (latewood) density and minimum (earlywood) density appears not to contain as much climatic information as (average) latewood density and (average) earlywood density, respectively.This project was supported by the institut National de la Recherche Agromonique (INRA). Thanks are due to Dr. G. Nepveu for his constant encouragement and assistance during this study     

Modelling water absorption in wood

Abstract

A fibre-level model for the longitudinal absorption of liquid water in wood has been developed. The model is primarily intended for simulation of absorption in softwoods. Capillary suction is based on the lumen radius, which is a stochastic parameter. The average lumen volume (and thus radius) is assumed to vary linearly across the annual ring and thus account for the difference in earlywood/latewood. The number of open bordered pits between fibres is also a stochastic parameter. The water flow rate is determined by the capillary suction and the flow resistance between fibres, i.e. the number of unaspirated bordered pits between fibres. The resulting pressure field in the liquid phase is calculated and the calculation has to be updated each time a new fibre has been filled with water. In this way the absorption is determined in a stepwise manner. Some general results are presented and the results resemble those obtained in experiments. It is shown that the model can predict features that a pure diffusion-based model cannot predict. Finally, the model is used for the simulation of an experiment that showed some unexpected results and the model gives a reasonable explanation.     

Earlywood vessel area of <Emphasis Type="Italic">Quercus pyrenaica</Emphasis> Willd. is a powerful indicator of soil water excess at growth resumption

We selected two sites dominated by the sub-Mediterranean oak Quercus pyrenaica Willd. close to its distribution boundary in northwestern Iberia, within a mountain region with a high winter precipitation. The sites differed in their soil water regime, corresponding to the edge of a peat bog, and to a moderate slope. We obtained tree-ring chronologies of total ring width (RW), and mean earlywood vessel area (MVA); their responses to climatic factors were compared for the period 1945–2002. RW presented a higher chronology quality than MVA, but was rather independent of climate, probably because of the presence of recurrent growth reductions. In contrast, MVA was closely related to precipitation during April and May, whereby a high water availability was coupled to smaller vessels. We found remarkable differences between the climatic signal of both stands, as trees growing on the peat soil responded later and with considerably lower intensity. We hypothesize that spring waterlogging causes that the response at the wettest site occurs only when soil desiccation begins, which results in a delayed climatic signal, and also lower intra- and inter-annual variation due to more homogeneous conditions. Climate–growth relationships at the driest site were mainly associated with the first row, whereas it is vessels expanding later in the season that show this relation for the moist site. Our results confirm that MVA chronologies are reliable proxies of both regional and local climatic conditions, but only a careful optimization by selecting vessel subsets does provide a complete view of their potential.     

Distribution of structure and lignin within growth rings of Norway spruce

A radial core from a Norway spruce (Picea abies (L.) Karst.) estimated to be about 107 years old was cut from a board and was analyzed for density and microfibril angle (MFA). Furthermore, cell geometry, wall thickness and lignin distribution were analyzed on three selected growth rings in detail. Intra-ring differences in the density profiles are also true for cell wall thicknesses as well as radial and tangential lumen diameters. A higher MFA was found for earlywood with a slow decrease toward the latewood region. The lignin was found to remain rather constant throughout the growth rings, which suggests a constant chemical composition of the cell wall material within the growth ring. From the recorded datasets on a cellular level, it can be concluded that the main adaptation regarding structure–property relationships toward the optimization of water transport and mechanical stability is mainly achieved at the cell level.