Tracheid Diameter Research Articles

Tracheid development under a drought event producing intra-annual density fluctuations in the semi-arid China

Drought is the primary limiting factor for tree growth in arid and semi-arid regions, where it can greatly influence xylem anatomical traits and induce multiple responses to wood development. However, the mechanisms driving xylogenesis and intra-annual density fluctuations (IADFs), as well as the seasonal dynamics of wood development in water-limited environments, are still unclear. In this study, we assessed the kinetics of xylem development weekly in Chinese pine (Pinus tabuliformis) and Qinghai spruce (Picea crassifolia), at two altitudes in the Helan Mountains, semi-arid China. Results indicate that summer drought in June inhibited cambial division and reduced xylogenesis, resulting in only 40% of the xylem developing before August. The onset of abundant precipitation in mid-July reactivated radial growth. This second growth extended the growing season by one month and partly compensated for the negative effect of the drought on growth. E-type IADF were characterized by narrow cells with thick walls, formed during July and early August. The duration of cell enlargement explained 57% of variance in tracheid diameter, showing that it played an important role in determining cell size. In contrast, changes in the cell wall thickness were mainly driven by the rate of secondary wall thickening, which explained 65% of the variance. This study reveals the potential mechanisms for xylem development and E-IADF formation under summer drought in semi-arid China, provides evidence for the plasticity and resistance of Chinese pine and Qinghai spruce under varying environmental conditions, and contributes to our understanding of likely future trends in forest productivity under climate changes.

Compressive strength parallel to grain of earlywood and latewood of yellow pine

The compressive strength parallel to grain of earlywood and latewood from the yellow pine sapwood and heartwood areas was examined in the study. The structure of the basic structural elements of wood - tracheids, which conduct water and/or perform the mechanical function - was also characterized. The compressive strength parallel to grain of latewood in the sapwood area was found to be twice as high as the compressive strength parallel to grain of earlywood. The compressive strength parallel to grain of latewood in the heartwood area, on the other hand, was found to be 2,5 times higher than the compressive strength parallel to grain of earlywood. This was due to the density of particular areas of wood and the dimensions of structural elements - tracheids. In the sapwood area, the density of latewood was ca. twice as high as the density of earlywood. Similar relationships were found for heartwood. The thickness of latewood tracheids was found to be 1,5 times greater than the thickness of earlywood tracheids. These relationships were observed in sapwood and heartwood. The diameter of earlywood tracheids in radial direction was twice as large as the diameter of latewood tracheids. These relationships were observed in yellow pine sapwood and heartwood

Paleoclimatic inferences based on wood growth interruptions in Late Triassic flood deposits from the southernmost Brazilian Gondwana

The goals of this study were to establish patterns in a silicified wood assemblage to depict the evolution patterns of the Triassic paleoclimate in southern Brazilian Gondwana during an interval of global arid to semi-arid climatic context, and the taphonomic process that led to the preservation of the so-called “Petrified Forest”, which is preserved in the central area of the state of Rio Grande do Sul. Analyses were developed with an assemblage of 13 permineralized conifer wood, using standard thin sections, whose anatomical details were studied in transmitted light. Ground-Penetrating Radar was used to obtain information about the depositional characteristics of the site. Main results are: true growth rings are absent in all samples, and the boundaries of the interruption zones are marked by an abrupt decline in cell diameter, but they are not accompanied by a reduction of cell wall thickness. The subsequent reversion to normal tracheid diameter is also abrupt, revealing the return of the previous growing conditions. Ground-penetrating Radar analyses confirmed that the Mata Sequence deposits correspond to a river. The identification of growth interruption zones in a Late Triassic wood assemblage in southernmost Brazilian Gondwana (Paleobotanic Garden of the city of Mata, RS) indicates the presence of tropical, temporarily dry climate conditions, characterized by irregular, short-term environmental disturbances to growth. The taphonomic process was related to a river-channel infilling depositional process, under the influence of high-energy flood events that dragged and buried the trees. Keywords: Wood growth patterns, Mata sequence, gymnosperms, Triassic climate, petrified forest.

Permeation behavior of low-melting-point Sn–Bi alloy in the fiber channel of pine wood

Wood and metal are the two most common materials, both with distinct advantages and disadvantages. Through the metallization process, the inherent defects of the two materials can be avoided, so that the composite material exhibits excellent structural properties and anisotropy. In this study, the pine wood was pretreated with dilute ammonia (5%), and then the low melting point Sn–Bi alloy was filled into the pine fiber without lignin at 180 °C and 3000 Pa. The density of metallic wood is about 3 times that of pine, while the impact toughness can be up to 2 times that of pine. By building the capillary buddle model, the filling mechanism of molten metal in pine wood was analyzed, and it was clear that high vacuum, high temperature, large porosity and large tracheid diameter are the conditions for rapid penetration. The conductive anisotropy was found on metalized wood, making metalized wood available in different places with requirements for electromagnetic shielding and antistatic.

Functional Relationships of Wood Anatomical Traits in Norway Spruce.

The quantitative assessment of wood anatomical traits offers important insights into those factors that shape tree growth. While it is known that conduit diameter, cell wall thickness, and wood density vary substantially between and within species, the interconnection between wood anatomical traits, tree-ring width, tree height and age, as well as environment effects on wood anatomy remain unclear. Here, we measure and derived 65 wood anatomical traits in cross-sections of the five outermost tree rings (2008–2012) of 30 Norway spruce [Picea abies (L.) H. Karst.] trees growing along an altitudinal gradient (1,400–1,750 m a.s.l.) in the northern Apennines (Italy). We assess the relationship among each anatomical trait and between anatomical trait groups according to their function for (i) tree-ring growth, (ii) cell growth, (iii) hydraulic traits, and (iv) mechanical traits. The results show that tree height significantly affects wood hydraulic traits, as well as number and tangential diameter of tracheids, and ultimately the total ring width. Moreover, the amount of earlywood and latewood percentage influence wood hydraulic safety and efficiency, as well as mechanical traits. Mechanically relevant wood anatomical traits are mainly influenced by tree age, not necessarily correlated with tree height. An additional level of complexity is also indicated by some anatomical traits, such as latewood lumen diameter and the cell wall reinforcement index, showing large inter-annual variation as a proxy of phenotypic plasticity. This study unravels the complex interconnection of tree-ring tracheid structure and identifies anatomical traits showing a large inter-individual variation and a strong interannual coherency. Knowing and quantifying anatomical variation in cells of plant stem is crucial in ecological and biological studies for an appropriate interpretation of abiotic drivers of wood formation often related to tree height and/or tree age.

Changes in wood anatomical traits in Scots pine under different climate-change scenarios

Abstract Although cell-anatomical variables are promising proxies reflecting seasonal as well as annual climate changes, their interdependencies are not yet fully understood. In the present study we assessed the changes in tree-ring width and various wood anatomical traits, including wall thickness, lumen diameter and tracheid diameter in the radial direction in saplings of Pinus sylvestris under six climatic conditions: 5°C warmer alone (ET) or combined with drought in June (ETJ) and in August (ETA) and CO2 enrichment alone (EC, 770 ppm) or combined with drought in June (ECJ) and in August (ECA). The experiments related to temperature conditions using 2-year saplings and CO2 conditions using 3-year saplings were completed in 2009 and 2010 in a greenhouse, respectively. Results showed that tree-ring width and tracheid diameter were not affected by any of the conditions applied, but the lumen diameter was larger and the wall thickness was thinner than those under control conditions. These reactions were verified under ETJ in the warming treatment and under all conditions under CO2 enrichment conditions. Our results indicated that drought counteracted the effects of elevated CO2 concentrations on wood anatomical properties, signifying complex interactions between the two major effects of climate change. Our comparison of wood parameters through experiments highlight the potential effect of climate change — increased drought stress due to higher temperatures and water shortage as well as elevated ambient CO2, on tracheid lumen diameter and wall thickness. Whereas the ring-width and tracheid diameter practically remained unaffected under the above-mentioned conditions.

Cross-field pitting characteristics of compression, lateral, and opposite wood in the stem wood of Ginkgo biloba and Pinus densiflora

AbstractThe characteristics of cross-field pitting among compression wood, lateral wood, and opposite wood, in the stem woods ofGinkgo bilobaandPinus densiflorawere investigated with optical and scanning electron microscopy. InGinkgo biloba, compression wood exhibited piceoid pits, while lateral and opposite wood exhibited cupressoid pits. The compression wood ofPinus densifloraexhibited cupressoid pits and piceoid pits, while lateral wood and opposite wood exhibited pinoid and window-like pits in the cross-field. In both species, compression wood yielded the smallest pit number among each part, while opposite wood yielded the greatest pit number per cross-field. Cross-field pitting diameters of compression wood and opposite wood were significantly smaller than lateral wood inGinkgo biloba, while the cross-field pitting of compression wood was the smallest inPinus densiflora. Radial tracheid diameter of compression wood was slightly smaller than lateral and opposite wood inGinkgo bilobaand significantly smaller than lateral and opposite wood inPinus densiflora. In conclusion, the cross-field pitting type, pit number, and cross-field pitting diameter could be used to identify reaction wood in the stem wood ofGinkgo bilobaandPinus densiflora.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ МОРФОЛОГО-АНАТОМИЧЕСКОЙ СТРУКТУРЫ ГОДИЧНЫХ СЛОЕВ СОСНЫ ОБЫКНОВЕННОЙ В МШИСТОМ И ОРЛЯКОВОМ ТИПАХ ЛЕСА

It is a well-known fact that life form of any plant is determined by its genetic characteristics. However, depending on the conditions of natural habitat, there are certain variations of not only external specific features of the same plants, but also of their anatomic organization. The article provides the results of the cell structure examinations of the Scots pine (Pinus sylvestris L.) growing in moss-covered (Pinetum pleurozium) and bracken (Pinetum pleurozium) forests. Ten temporary experimental sites for each type of forest were set according to methods used in forest sciences and forest taxation. Taking into account the structure of annual layers of conifers, the study determined the quantitative parameters of radial growth and the main size indicators of early and late tracheids. It is revealed that the width of an annual layer and the quantity of tracheids in a radial row belong to the most changeable parameters, while tangential dimensions of tracheids belong to the least changeable parameters. In general, the analyses of obtained data from 18 dimensional characteristics showed that moss-covered pine forest is characterized by the greater value of a radial diameter of early tracheids (6 %) and their cavities (3 %), as well as greater cavity areas (3 %); a bracken pine forest, in turn, has a greater width of latewood in an annual layer (16 %) and thickness of a cell wall of late tracheids (10 %). Therefore, it is recommended to measure only these specific parameters to reduce the time spent on conducting researches in future. The cluster analysis confirmed that the morphological and anatomical characteristics are effective indicators to define the forest type.

Effect of Seed Transfer on Selected Wood Quality Attributes of Jack Pine (Pinus banksiana Lamb.)

So far, few studies have considered the impacts of seed sources transfer on jack pine (Pinus banksiana Lamb.) wood quality, although wood quality attributes (WQA) in general and the differences between juvenile and mature wood in particular will determine suitability of the produced wood for end-uses. The main objective of this study was to examine the possibility of selecting superior jack pine provenances based on selected WQA. Twenty-two provenances of jack pine were planted in 1964 in Petawawa Research Forest, ON, Canada, as part of a provenance test. The plantation location offers conditions close to optimum for jack pine growth. Transition ages at breast height, determined with tracheids length, were computed with a piecewise model. Measurements at age 42 from seed were subjected to analyses of variance. Radial variations from pith to bark, as well as trends with seed sources origin of the selected WQA were also considered. A ranking was made based on a selection index built with four WQA. The provenances matured between 8 and 14 years, corresponding to 17%–48% of juvenile wood proportion. Significant differences among provenances were observed for ring width, ring density, tracheid length, and diameter at breast height but not for tracheid diameter, tree height, transition age, and juvenile wood proportion. None of the provenances ranked the best with all the selected WQA, but it was possible to find provenances exhibiting both high growth rate and good wood quality. A surprising result of this study was that tracheid diameter initially enlarged for 8 years, before declining toward the bark. It is possible to select provenances for a higher growth rate and for good physical (i.e., related to wood density) and anatomical (i.e., related to tracheid dimensions) wood quality attributes.

Water potential control of turgor-driven tracheid enlargement in Scots pine at its xeric distribution edge.

The extent to which water availability can be used to predict the enlargement and final dimensions of xylem conduits remains an open issue. We reconstructed the time course of tracheid enlargement in Pinus sylvestris trees in central Spain by repeated measurements of tracheid diameter on microcores sampled weekly during a 2yr period. We analyzed the role of water availability in these dynamics empirically through time-series correlation analysis and mechanistically by building a model that simulates daily tracheid enlargement rate and duration based on Lockhart's equation and water potential as the sole input. Tracheid enlargement followed a sigmoid-like time course, which varied intra- and interannually. Our empirical analysis showed that final tracheid diameter was strongly related to water availability during tracheid enlargement. The mechanistic model was calibrated and successfully validated (R2 =0.92) against the observed tracheid enlargement time course. The model was also able to reproduce the seasonal variations of tracheid enlargement rate, duration and final diameter (R2 =0.84-0.99). Our results support the hypothesis that tracheid enlargement and final dimensions can be modeled based on the direct effect of water potential on turgor-driven cell expansion. We argue that such a mechanism is consistent with other reported patterns of tracheid dimension variation.

Acoustic-Based Prediction of End-Product-Based Fibre Determinates within Standing Jack Pine Trees

The objective of this study was to specify, parameterize, and evaluate an acoustic-based inferential framework for estimating commercially-relevant wood attributes within standing jack pine (Pinus banksiana Lamb) trees. The analytical framework consisted of a suite of models for predicting the dynamic modulus of elasticity (me), microfibril angle (ma), oven-dried wood density (wd), tracheid wall thickness (wt), radial and tangential tracheid diameters (dr and dt, respectively), fibre coarseness (co), and specific surface area (sa), from dilatational stress wave velocity (vd). Data acquisition consisted of (1) in-forest collection of acoustic velocity measurements on 61 sample trees situated within 10 variable-sized plots that were established in four mature jack pine stands situated in boreal Canada followed by the removal of breast-height cross-sectional disk samples, and (2) given (1), in-laboratory extraction of radial-based transverse xylem samples from the 61 disks and subsequent attribute determination via Silviscan-3. Statistically, attribute-specific acoustic prediction models were specified, parameterized, and, subsequently, evaluated on their goodness-of-fit, lack-of-fit, and predictive ability. The results indicated that significant (p ≤ 0.05) and unbiased relationships could be established for all attributes but dt. The models explained 71%, 66%, 61%, 42%, 30%, 19%, and 13% of the variation in me, wt, sa, co, wd, ma, and dr, respectively. Simulated model performance when deploying an acoustic-based wood density estimate indicated that the expected magnitude of the error arising from predicting dt, co, sa, wt, me, and ma prediction would be in the order of ±8%, ±12%, ±12%, ±13%, ±20%, and ±39% of their true values, respectively. Assessment of the utility of predicting the prerequisite wd estimate using micro-drill resistance measures revealed that the amplitude-based wd estimate was inconsequentially more precise than that obtained from vd (≈ <2%). A discourse regarding the potential utility and limitations of the acoustic-based computational suite for forecasting jack pine end-product potential was also articulated.

Phenotypic Correlations among Growth and Selected Wood Properties in White Spruce (Picea glauca (Moench) Voss) †

We examined phenotypic relationships among radial growth-related, physical (i.e., related to wood density), and anatomical (i.e., related to tracheid dimensions) wood properties in white spruce (Picea glauca (Moench) Voss), in order to determine the strength and significance of their correlations. Additionally, principal component analysis (PCA) was used to establish if all of the properties must be measured and to determine the key properties that can be used as proxies for the other variables. Radial growth-related and physical properties were measured with an X-ray densitometer, while anatomical properties were measured with a Fiber Quality Analyzer. Fifteen wood properties (tracheid length (TL) and diameter (TD), earlywood tracheid length (ETL) and diameter (ETD), latewood tracheid length (LTL) and diameter (LTD), ring width (RW), ring area (RA), earlywood width (EWW), latewood width (LWW), latewood proportion (LWP), ring density (RD), intra-ring density variation, earlywood density (EWD), and latewood density (LWD)) were assessed. Relationships were evaluated at intra-ring and inter-ring levels in the juvenile wood (JW) and mature wood (MW) zones. Except for a few cases when mature tracheid diameter (TD) was involved, all intra-ring anatomical properties were highly and significantly correlated. Radial growth properties were correlated, with stronger relationships in MW compared to JW. Physical properties were often positively and significantly correlated in both JW and MW. A higher earlywood density coupled with a lower latewood density favored wood uniformity, i.e., the homogeneity of ring density within a growth ring. Managing plantations to suppress trees growth during JW formation, and enhancing radial growth when MW formation starts will favor overall wood quality. In order, RW-EWW-RA, TL-ETL-LTL, and RD-EWD-LWP are the three clusters that appeared in the three wood zones, the whole pith-to-bark radial section, the juvenile wood zone, and the mature wood zone.

Conflicting functional effects of xylem pit structure relate to the growth-longevity trade-off in a conifer species

Consistent with a ubiquitous life history trade-off, trees exhibit a negative relationship between growth and longevity both among and within species. However, the mechanistic basis of this life history trade-off is not well understood. In addition to resource allocation conflicts among multiple traits, functional conflicts arising from individual morphological traits may also contribute to life history trade-offs. We hypothesized that conflicting functional effects of xylem structural traits contribute to the growth-longevity trade-off in trees. We tested this hypothesis by examining the extent to which xylem morphological traits (i.e., wood density, tracheid diameters, and pit structure) relate to growth rates and longevity in two natural populations of the conifer species Pinus ponderosa Hydraulic constraints arise as trees grow larger and xylem anatomical traits adjust to compensate. We disentangled the effects of size through ontogeny in individual trees and growth rates among trees on xylem traits by sampling each tree at multiple trunk diameters. We found that the oldest trees had slower lifetime growth rates compared with younger trees in the studied populations, indicating a growth-longevity trade-off. We further provide evidence that a single xylem trait, pit structure, with conflicting effects on xylem function (hydraulic safety and efficiency) relates to the growth-longevity trade-off in a conifer species. This study highlights that, in addition to trade-offs among multiple traits, functional constraints based on individual morphological traits like that of pit structure provide mechanistic insight into how and when life history trade-offs arise.

Response of alfalfa and sugar beet to field dodder (Cuscuta campestris Yunck.) parasitism: a physiological and anatomical approach

The physiological and anatomical impact of field dodder (Cuscuta campestris Yunck.) on alfalfa and sugar beet was examined under controlled conditions. The following parameters were checked: physiological — content of pigments (chlorophyll a, chlorophyll b, and carotenoids) and mineral nutrients: nitrogen, phosphorus, potassium, and percent of organic and mineral nutrients; and anatomical — thickness of the epidermis and cortex, diameter of the stem and central cylinder of alfalfa plants, diameter of tracheids and phloem cells, area of xylem and phloem, and hydraulic conductance of petiole bundles in petiole vascular bundles of sugar beet plants. Leaf parameters were also measured on both host plants: thickness of upper and underside leaf epidermis, thickness of palisade, spongy and mesophyll tissue, and diameter of vascular bundle cells. Pigments content and anatomical parameters were measured 7, 14, 21, 28, 35, and 42 d after infestation (DAI), while mineral nutrient contents were determined 20 and 40 DAI. Field dodder caused a significant reduction in pigments content in infested alfalfa (15%–68%) and sugar beet plants (1%–54%). The results obtained in this study confirmed that this parasitic flowering plant has a strong effect on most anatomical parameters of the stem and leaf of alfalfa and leaf and petiole of sugar beet. Also, it was revealed that field dodder increased the contents of N, P2O5, K2O, and organic nutrients in infested alfalfa plants, while infested sugar beet plants had higher contents of N and organic nutrients compared with non-infested plants.

Environmental Factors Influence Plant Vascular System and Water Regulation.

Developmental initiation of plant vascular tissue, including xylem and phloem, from the vascular cambium depends on environmental factors, such as temperature and precipitation. Proper formation of vascular tissue is critical for the transpiration stream, along with photosynthesis as a whole. While effects of individual environmental factors on the transpiration stream are well studied, interactive effects of multiple stress factors are underrepresented. As expected, climate change will result in plants experiencing multiple co-occurring environmental stress factors, which require further studies. Also, the effects of the main climate change components (carbon dioxide, temperature, and drought) on vascular cambium are not well understood. This review aims at synthesizing current knowledge regarding the effects of the main climate change components on the initiation and differentiation of vascular cambium, the transpiration stream, and photosynthesis. We predict that combined environmental factors will result in increased diameter and density of xylem vessels or tracheids in the absence of water stress. However, drought may decrease the density of xylem vessels or tracheids. All interactive combinations are expected to increase vascular cell wall thickness, and therefore increase carbon allocation to these tissues. A comprehensive study of the effects of multiple environmental factors on plant vascular tissue and water regulation should help us understand plant responses to climate change.

Does climate-related in situ variability of Scots pine (Pinus sylvestris L.) needles have a genetic basis? Evidence from common garden experiments.

The correlations of phenotypic traits with environmental drivers suggest that variability of these traits is a result of natural selection, especially if such trait correlations are based on genetic variability. We hypothesized that in situ correlations of structural needle traits of Scots pine (Pinus sylvestris L) with minimal winter temperature (Tmin) reported previously from a temperate/boreal transect would be conserved when plants are cultivated under common conditions. We tested this hypothesis by analyzing needles from two common gardens located in the temperate zone, one including adult trees and the other juvenile seedlings. The majority of adult needle traits for which correlations with Tmin were found in the field turned out to be under environmental influence. In contrast, the majority of traits studied in juvenile needles were correlated with the original Tmin suggesting the role of past natural selection in shaping their variability. Juvenile needles thus appeared to be inherently less plastic than adult needles, perhaps reflecting the stronger selective pressure acting during juvenile, as compared with adult, ontogenetic stage. Genetically based cold-climate adaptation in either juvenile or adult needles, or both, involved an increase in leaf mass per area and leaf density, decrease in needle length, reduction in the amount of xylem and phloem, increase in thickness of epidermis, decrease in tracheid diameter and increase in tracheid density, and increase in diameter and volume fraction of resin ducts. We also show that at least some traits, such as transverse xylem and phloem areas and number of fibers, scale with needle length, suggesting that climate-related trait variation may also be mediated by changes in needle length. Moreover, slopes of these allometric relationships may themselves be plastically modified. The phenotypic syndrome typical of needles from cold environments may thus be under environmental, genetic and allometric control.

Drought-induced dieback of Pinus nigra: a tale of hydraulic failure and carbon starvation.

Ongoing climate change is apparently increasing tree mortality rates, and understanding mechanisms of drought-induced tree decline can improve mortality projections. Differential drought impact on conspecific individuals within a population has been reported, but no clear mechanistic explanation for this pattern has emerged. Following a severe drought (summer 2012), we monitored over a 3-year period healthy (H) and declining (D) Pinus nigra trees co-occurring in a karstic woodland to highlight eventual individual-specific physiological differences underlying differential canopy dieback. We investigated differences in water and carbon metabolism, and xylem anatomy as a function of crown health status, as well as eventual genotypic basis of contrasting drought responses. H and D trees exploited the same water pools and relied on similar hydraulic strategies to cope with drought stress. Genetic analyses did not highlight differences between groups in terms of geographical provenance. Hydraulic and anatomical analyses showed conflicting results. The hydraulic tracheid diameter and theoretical hydraulic conductivity were similar, but D trees were characterized by lower water transport efficiency, greater vulnerability to xylem conduit implosion and reduced carbohydrate stores. Our results suggest that extreme drought events can have different impacts on conspecific individuals, with differential vulnerability to xylem embolism likely playing a major role in setting the fate of trees under climate change.

Acoustic Velocity—Wood Fiber Attribute Relationships for Jack Pine Logs and Their Potential Utility

This study presents an acoustic-based predictive modeling framework for estimating a suite of wood fiber attributes within jack pine (Pinus banksiana Lamb.) logs for informing in-forest log-segregation decision-making. Specifically, the relationships between acoustic velocity (longitudinal stress wave velocity; vl) and the dynamic modulus of elasticity (me), wood density (wd), microfibril angle (ma), tracheid wall thickness (wt), tracheid radial and tangential diameters (dr and dt, respectively), fiber coarseness (co), and specific surface area (sa), were parameterized deploying hierarchical mixed-effects model specifications and subsequently evaluated on their resultant goodness-of-fit, lack-of-fit, and predictive precision. Procedurally, the data acquisition phase involved: (1) randomly selecting 61 semi-mature sample trees within ten variable-sized plots established in unthinned and thinned compartments of four natural-origin stands situated in the central portion the Canadian Boreal Forest Region; (2) felling and sectioning each sample tree into four equal-length logs and obtaining twice-replicate vl measurements at the bottom and top cross-sectional faces of each log (n = 4) from which a log-specific mean vl value was calculated; and (3) sectioning each log at its midpoint and obtaining a cross-sectional sample disk from which a 2 × 2 cm bark-to-pith radial xylem sample was extracted and subsequently processed via SilviScan-3 to derive annual-ring-specific attribute values. The analytical phase involved: (1) stratifying the resultant attribute—acoustic velocity observational pairs for the 243 sample logs into approximately equal-sized calibration and validation data subsets; (2) parameterizing the attribute—acoustic relationships employing mixed-effects hierarchical linear regression specifications using the calibration data subset; and (3) evaluating the resultant models using the validation data subset via the deployment of suite of statistical-based metrics pertinent to the evaluation of the underlying assumptions and predictive performance. The results indicated that apart from tracheid diameters (dr and dt), the regression models were significant (p ≤ 0.05) and unbiased predictors which adhered to the underlying parameterization assumptions. However, the relationships varied widely in terms of explanatory power (index-of-fit ranking: wt (0.53) > me > sa > co > wd >> ma (0.08)) and predictive ability (sa > wt > wd > co >> me >>> ma). Likewise, based on simulations where an acoustic-based wd estimate is used as a surrogate measure for a Silviscan-equivalent value for a newly sampled log, predictive ability also varied by attribute: 95% of all future predictions for sa, wt, co, me, and ma would be within ±12%, ±14%, ±15%, ±27%, and ±55% and of the true values, respectively. Both the limitations and potential utility of these predictive relationships for use in log-segregation decision-making, are discussed. Future research initiatives, consisting of identifying and controlling extraneous sources of variation on acoustic velocity and establishing attribute-specific end-product-based design specifications, would be conducive to advancing the acoustic approach in boreal forest management.

Pine and larch tracheids capture seasonal variations of climatic signal at moisture-limited sites

Key messageAlthough the radial diameter and wall thickness of conifer tracheids from dry environments are climatic-sensitive across the full ring area, each cell parameter has a specific zone in a ring where its climatic response reaches the maximum.Seasonal dynamics of the timing and rate in cell production and differentiation imprint climate signals into intra-ring variations of anatomical wood structure (e.g. intra-annual density fluctuations). Despite recent methodological advances in quantitative wood anatomy, our understanding of xylem response to climate at the finest scale of intra-ring resolution is incomplete. The goal of this study is to investigate intra-ring changes of tracheid dimensions (cell radial diameter and wall thickness) controlled by moisture stress. Anatomical wood parameters of Pinus sylvestris and Larix sibirica from two drought-susceptible locations in Khakassia, South Siberia, were analysed. We found that inter-annual variation of tracheid parameters regularly exceeds the variation between radial tracheid files. This suggests that the climatic signal is recorded throughout the entire ring. However, each cell parameter has a specific zone in the ring where its climatic response reaches the maximum. The climatic response of the radial cell diameter has a temporal shift across the ring, which is particularly apparent in pine rings. The climatic response of cell wall thickness at the intra-ring scale has a more complex pattern. Our results facilitate investigation of the climate impact on tree rings at the finest intra-ring scale by quantifying the timing of climatic impact on ring structure and identifying specifically when climate impacts the formation of a particular cell.

Tree-ring anatomy and carbon isotope ratio show both direct and legacy effects of climate on bimodal xylem formation in Pinus pinea.

Understanding how climate affects xylem formation is critical for predicting the impact of future conditions on tree growth and functioning in the Mediterranean region, which is expected to face warmer and drier conditions. However, mechanisms of growth response to climate at different temporal scales are still largely unknown, being complicated by separation between spring and autumn xylogenesis (bimodal temporal pattern) in most species such as Mediterranean pines. We investigated wood anatomical characteristics and carbon stable isotope composition in Mediterranean Pinus pinea L. along tree-ring series at intra-ring resolution to assess xylem formation processes and responses to intra-annual climate variability. Xylem anatomy was strongly related to environmental conditions occurring a few months before and during the growing season, but was not affected by summer drought. In particular, the lumen diameter of the first earlywood tracheids was related to winter precipitation, whereas the size of tracheids produced later was influenced by mid-spring precipitation. Diameter of latewood tracheids was associated with precipitation in mid-autumn. In contrast, tree-ring carbon isotope composition was mostly related to climate of the previous seasons. Earlywood was likely formed using both recently and formerly assimilated carbon, while latewood relied mostly on carbon accumulated many months prior to its formation. Our integrated approach provided new evidence on the short-term and carry-over effects of climate on the bimodal temporal xylem formation in P. pinea. Investigations on different variables and time scales are necessary to disentangle the complex climate influence on tree growth processes under Mediterranean conditions.