Variation In Wood Density Research Articles

Climate has a larger effect than stand basal area on wood density in Pinus ponderosa var. scopulorum in the southwestern USA

Stand basal area of ponderosa pine ( Pinus ponderosa var. scopulorum Engelm.) in the US Southwest has little effect on the density of the wood produced, but climatic fluctuations have a strong effect. Wood density increases during drought, particularly if the drought occurs in late winter/early spring. Future droughts, as are predicted to increase in the US Southwest, may lead to production of smaller radial increments of higher density wood in ponderosa pine. Forest restoration treatments in the US Southwest are generating large quantities of small-diameter logs. Due to negative perceptions about ponderosa pine wood quality, this material is often seen as a “waste disposal” problem rather than a high-value resource. Our objective was to understand more about variation in southwestern US ponderosa pine wood density, an important indicator of wood quality. Specifically, we investigated the effect of stand basal area on wood density, and the effect of annual and quarterly climatic variation on wood density. We collected samples from 54 trees grown at six different basal area levels from a replicated stand density experiment. Pith-to-bark strips were used in an X-ray densitometer to obtain annual density and growth measurements from 1919 to the present. Stand density had a strong effect on growth rate, but little effect on wood density. However, climatic variation did influence wood density, which increased in drought years before quickly returning to pre-drought levels. Stand basal area is not a good indicator of wood density for foresters planning to utilize material from timber harvests in the southwestern USA. Future droughts, as are predicted to increase in the region, will likely reduce wood volume production but may increase wood density in ponderosa pine.

Vulnerability to xylem embolism correlates to wood parenchyma fraction in angiosperms but not in gymnosperms.

Understanding which structural and functional traits are linked to species' vulnerability to embolism formation (P50) may provide fundamental knowledge on plant strategies to maintain an efficient water transport. We measured P50, wood density (WD), mean conduit area, conduit density, percentage areas occupied by vessels, parenchyma cells (PATOT) and fibers (FA) on branches of angiosperm and gymnosperm species. Moreover, we compiled a dataset of published hydraulic and anatomical data to be compared with our results. Species more vulnerable to embolism had lower WD. In angiosperms, the variability in WD was better explained by PATOT and FA, which were highly correlated. Angiosperms with a higher P50 (less negative) had a higher amount of PATOT and total amount of nonstructural carbohydrates. Instead, in gymnosperms, P50 vs PATOT was not significant. The correlation between PATOT and P50 might have a biological meaning and also suggests that the causality of the commonly observed relationship of WD vs P50 is indirect and dependent on the parenchyma fraction. Our study suggests that angiosperms have a potential active embolism reversal capacity in which parenchyma has an important role, while in gymnosperms this might not be the case.

Tropical Tree Branch-Leaf Nutrient Scaling Relationships Vary With Sampling Location.

Bivariate relationships between plant tissue nutrient concentration have largely been studied across broad environmental scales regardless of their covariation with soil and climate. Comparing leaf and branch wood concentrations of C, Ca, K, Mg, N, Na, and P for trees growing in tropical forests in Amazonia and Australia we found that the concentrations of most elements varied with sampling location, but with foliar and branch woody tissues varying from site to site in different ways. Using a Mixed Effect Model (MEM) approach it was further found that relationships between branch and leaf concentrations within individual plots differed in terms of both slope and/or significance to the ordinary least squares (OLS) estimates for most elements. Specifically, using MEM we found that within plots only K and Mg were correlated across organs, but with the K cross-organ intercept estimates varying significantly between sites. MEM analyses further showed that within-plot wood density variations were also negatively related to wood K and Na, suggesting a potentially important role for these cations in water transport and/or storage in woody tissues. The OLS method could not detect significant correlations in any of the above cases. By contrast, although Ca, N, and P leaf and wood tissue concentrations showed similar patterns when individual elements were compared across sites, MEM analyses suggested no consistent association within sites. Thus, for all these three elements, strong within-tree scaling relationships were inferred when data were analyzed across sites using OLS, even though there was no relationship within individual sites. Thus (as for Ca, N, and P) not only can a pooling of data across sites result in trait (co)variations attributable to the environment potentially being incorrectly attributed solely to the species and/or individual (the so-called “ecological fallacy”), but in some cases (as was found here for K and Na) the opposite can also sometimes occur with significant within-site covariations being obscured by large site-site variations. We refer to the latter phenomenon as “environmental obfuscation.”

Pollution-induced slowdown of coarse woody debris decomposition differs between two coniferous tree species

Boreal forests store a large portion of the planet’s terrestrial carbon. A significant portion of this carbon is stored in coarse woody debris (CWD). Industrial pollution greatly inhibits organic matter decomposition and thus enhances carbon sequestration in the soil. However, little is known about the decomposition of CWD in polluted areas. In this work, by means of dendrochronological cross-dating, we determined the death dates of 90 downed Siberian spruce (Picea obovata Ledeb.) and Siberian fir (Abies sibirica Ledeb.) logs in the latest stages of decay in an undisturbed boreal forest and in two industrially polluted forests with 10-fold and more than 100-fold higher copper content in the soil. We found that, in the unpolluted area, the mean halftime of fir and spruce decomposition was 26 years and 23 years, respectively. In polluted areas, this time increased by approximately 16 years for fir and 5 years for spruce. Based on an exponential decay model, pollution caused a 16–60% decrease in the wood decomposition rate constant. Copper concentrations in CWD were similar between tree species and were about 10–20 times lower than in the surrounding soil. These values are comparable with the concentrations tolerated by fungi in laboratory tests, indicating that heavy metal excess cannot be considered a primary inhibitor of wood decomposer activity. The greater pollution-induced delay in the decomposition of fir trees, which are lighter and smaller in size than spruce trees, suggests that dead tree leaning is an important factor in the wood decomposition slowdown in polluted areas where stand density increases due to intensive forest regeneration because of the reduced competition of tree seedlings with toxically inhibited herbaceous vegetation.We also evaluated dynamic probing as a rapid, low-cost, and nondestructive surrogate of wood density measuring. Dynamic probing performed in the field on heavily decayed CWD explained about 40% of wood density variability and about 70% of variability when taking into account the gravimetrically measured wood moisture content. With negligible modifications, this method can be applied in the field monitoring of wood density loss. For the purpose of between-study comparisons, we recommend transforming the widely used measure of penetration depth to specific resistance to penetration and encourage the elaboration of reference tables that relate specific resistance to penetration and wood density for different tree species across distinct ecological zones.

Comparison of dendrometric features of Scots pine trees and wood density from one of genetic origin obtained from the provenance surface in Forest Research Institute in Rogów

Comparison of dendrometric features of Scots pine trees and wood density from one of genetic origin obtained from the provenance surface in Forest Research Institute in Rogów. Scots pine is characterized by high variability of morphological-tribal and physiological-growth features, which also translates into high variability in wood density. The provenance area of LZD in Rogów was founded on the international project of IUFRO organization in 1966. It is composed by 16 genetic origins of Scots pine closely described and nurtured throughout the life of trees, which creates wood material from this surface unique in research. Due to the fact that Scots pine is the most important conifer species in Poland, both for forests and for the industry, comprehensive research with regard to genetic origin seems to be necessary.

Intraspecific trait variation and neighborhood competition drive community dynamics in an old-growth spruce forest in northwest China

Identifying the factors driving the growth and mortality of trees is important for understanding the mechanisms of forest dynamics. Here, we studied the growth and survival of trees ≥10 cm diameter at breast height (DBH) in a 15-ha temperate coniferous old growth forest plot in northwest China. We examined the relative importance of abiotic (i.e., soil nutrient and topographic) and biotic variables (i.e., tree size, competition intensity, and wood density of each individual) on the growth and mortality Picea schrenkiana, the dominant species in this forest. We found a high mortality rate and a low recruitment rate for P. schrenkiana over a period of six years. The total abundance and basal area of this species decreased, respectively. Overall, nearly 10% of P. schrenkiana individuals died. Our models of mortality had relatively low explanatory power (3% for all trees and 5% for trees <30 cm DBH), while growth models had moderate explanatory power. The growth of P. schrenkiana trees more strongly correlated with biotic factors (i.e., competition and trait) than abiotic factors (i.e., soil nutrients and topography). Overall, DBH, neighborhood crowding index (NCI), wood density (WD), and convexity explained 26% of the variation in the relative growth rate (RGR) of P. schrenkiana trees. The majority of this variation was explained by DBH alone. For trees with DBH <30 cm, DBH, NCI, WD, convexity, and slope) explained 29% of variation in RGR. In contrast, models of the absolute growth rate (AGR) of all P. schrenkiana trees only explained 3% of variation. For trees <30 cm DBH, NCI, WD, and slope explained 21% variation in AGR and the main part was explained by intraspecific variation in WD. Ultimately, our results highlight the importance of intraspecific variation in traits and competition when exploring demographic process in low-density and species-poor forests.

Variation in carbon concentration and wood density for five most commonly grown native tree species in central highlands of Ethiopia: The case of Chilimo dry Afromontane forest

ABSTRACTInformation regarding carbon concentration and wood density are lacking in Chilimo dry Afromontane forest.The aim of this study was to estimate carbon concentration and wood density for Allophyllus abyssinicus, Olea europaea, Olinia rochetiana, Rhus glutinosa, and Scolopia theifolia. A total of 105, 30–50 mm thick wood discs were collected and oven dried at 102°C and 67°C to constant weight, chopped and finally grinded into 0.2 mm with a grinding mill. Carbon concentration was analyzed using the ash method, while wood density was estimated using the water displacement method. The highest carbon concentration (57.12%) was found for O. rochetiana, however, the lowest carbon concentration (56.43%) was found for A. abyssinicus. Stem parts had higher carbon concentration (56.98%) than branch (56.74%) and leave (54.53%) parts. O. europaea exhibited the highest wood density (0.67 g cm−3) value than other species. However, the lowest wood density (0.42 g cm−3) was exhibited for A. abyssinicus. Wood density was also showed a decreasing trend along with increases in stem height and maximum wood density (0.62 g cm−3) was found under stump position, while, the minimum wood density (0.4 g cm−3) was found under tree commercial height.

Tree rings in tree species of a seasonal semi-deciduous forest in southern Brazil: wood anatomical markers, annual formation and radial growth dynamic

Tree rings provide valid predictions regarding species age and growth rates and, therefore, they can contribute to understand forest dynamics and ecology. In this work, we evaluated the tree rings of eight tree species from different successional groups that show distinct degrees of deciduousness in a seasonal semi-deciduous forest located in a transition zone between subtropical and the tropical climates in southern Brazil. We focused on wood anatomical markers, the annual nature of tree-ring formation, the description of false rings, a cross-dating analyses and an interpretation of the radial increment dynamics of the species. We sampled increment cores at breast height, performed cambial wounding and measured tree-ring widths. Annual tree rings were found in seven species, which were confirmed by cambium wounding. Differences in fiber wall thickness between latewood and earlywood and the marginal parenchyma were the main anatomical markers observed. Deciduous species had better distinction of tree ring boundaries, while the evergreen species had slightly distinct tree ring boundaries. False rings were characterized by variations in wood density and axial parenchyma bands of different widths within true tree rings. The annual tree ring confirmation and the anatomical description of the true and false rings are useful for future dendroecological research in the area. Considering the cross-dating analyses and tree-ring distinctiveness, Chrysophyllum gonocarpum is a recommended species. Regarding radial growth, the early secondary species had higher growth rates than the late secondary species. Assessing the growth trajectories over time, distinct patterns were observed among the species: a constant growth, an initial increase followed by a reduction, and oscillations of the growth were observed. As no consistent pattern of the growth trajectories was observed among species that belong to the same successional groups, they contribute to the explanation of the particular life history of these individuals in the seasonal semi-deciduous forest.

Intra-Ring Variations and Interrelationships for Selected Wood Anatomical and Physical Properties of Thuja Occidentalis L.

Intra-ring variation in wood density and tracheid anatomical properties and wood property interrelationships were investigated in Thuja occidentalis L. Samples were taken from three stands in Abitibi–Témiscamingue, Quebec, Canada. The structure of T. occidentalis wood is simple, homogeneous and uniform, which is desirable for wooden structures that require wood uniformity. From early- to latewood, cell and lumen diameter decreased, while cell wall thickness increased. These changes led to an increase of the cell wall proportion. Wood ring density and width interrelationships were weaker in mature wood compared to juvenile wood. Earlywood density is the more important in determining mature wood density than latewood density and proportion. Earlywood density explains 92% and 89% of the variation in juvenile and mature wood density, respectively. The negative relationship between ring density and width, although significant, was low and tends to weaken with increasing tree age, thus providing the opportunity for silvicultural practices to improve both growth and wood density. Ring width was positively and strongly correlated to early- and latewood width, but negatively correlated to tracheid length and latewood proportion. Accordingly, increases in ring width produce smaller tracheids and wider earlywood without a corresponding increase in latewood. Practical implications of the results are discussed.

Variation of Wood Density and Anatomical Characters from Altitude Differences: Case Study of Selected Fabaceae Trees in West Sumatra Secondary Forest, Indonesia

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Characterizing wood density–climate relationships along the stem in black spruce (Picea mariana (Mill.) B.S.P.) using a combination of boosted regression trees and mixed-effects models

The relationships between climate and wood density components, i.e. minimum, maximum and average ring density, have been characterized mainly at breast height, while little information is available for other stem heights. This work aimed to (1) identify the significant climate variables related to ring density components in black spruce (Picea mariana (Mill.) B.S.P.) and (2) assess whether their effects vary significantly along the stem. Densitometric data were obtained from 68 black spruce trees from northwestern Ontario, Canada. Six discs along the stem, from stump to base of the live crown, were sampled. For each sample height and density component, we first developed mixed-effects models using ring width and cambial age as predictors. Monthly climate variables were later integrated into the models. The candidate climate variables were pre-selected using the boosted regression trees method. In addition to observed density–climate relationships, a significant effect of sample height was found. Findings revealed that the relationships were similar in nature but varied in strength and timing along the stem. The wood density variation showed delayed sensitivities to some climate variables among sampling heights. Such delayed responses may be caused by the axial progression of water requirement and of hormonal and photosynthetic allocation along the stem throughout the growing season.

Effect of provenance and climate on intra-annual density fluctuations of Norway spruce Picea abies (L.) Karst. in Poland

Understanding the growth pattern of trees of various provenances in response to climatic conditions provides information on the adaptive potential of trees. Intra-annual density fluctuations (IADFs) are anatomical markers of variations in wood density within the annual wood increment. Latewood-like cells within earlywood, resulting from severe drought during spring and early summer, express the structural adaptation of the wood tissue to unfavorable climatic conditions. In this study, we used two 40-year old IUFRO provenance trials of Norway spruce located in the western and north-eastern Poland to i) determine the effect of provenance on the IADF frequency and ii) to define the climatic factors determining the formation of IADF. Three highly polymorphic nuclear microsatellites are used to determine the differentiation among provenances in particular between the northern and southern Polish distribution area.Our results demonstrate that the frequency of all types of IADFs is determined by the growing conditions, and only the IADFs in the transition zone are determined by provenance origin. The highest variability between provenances in response to climatic differences was observed for IADF in transition zone, where temperatures and rainfall of spring and early summer differentiated northern and southern provenances. Moreover, the IADF frequency was influenced by drought, thereby differentiating provenances in terms of their sensitivity to severe conditions. Furthermore, environmental differentiation of climate-growth reaction was expressed by a stronger impact of climatic conditions observed in the western than in the northeastern trial site.The results of this study confirm the dependency of climate related changes in wood characteristics on provenance origin. Therefore, density fluctuations seem to be an appropriate adaptive trait for selecting Norway spruce provenances with varying degree of drought sensitivity.

Wood Density Variations of Legume Trees in French Guiana along the Shade Tolerance Continuum: Heartwood Effects on Radial Patterns and Gradients

Increasing or decreasing wood density (WD) from pith to bark is commonly observed in tropical tree species. The different types of WD radial variations, long been considered to depict the diversity of growth and mechanical strategies among forest guilds (heliophilic vs. shade-tolerant), were never analyzed in the light of heartwood (HW) formation. Yet, the additional mass of chemical extractives associated to HW formation increases WD and might affect both WD radial gradient (i.e., the slope of the relation between WD and radial distance) and pattern (i.e., linear or nonlinear variation). We studied 16 legumes species from French Guiana representing a wide diversity of growth strategies and positions on the shade-tolerance continuum. Using WD measurements and available HW extractives content values, we computed WD corrected by the extractive content and analyzed the effect of HW on WD radial gradients and patterns. We also related WD variations to demographic variables, such as sapling growth and mortality rates. Regardless of the position along the shade-tolerance continuum, correcting WD gradients reveals only increasing gradients. We determined three types of corrected WD patterns: (1) the upward curvilinear pattern is a specific feature of heliophilic species, whereas (2) the linear and (3) the downward curvilinear patterns are observed in both mid- and late-successional species. In addition, we found that saplings growth and mortality rates are better correlated with the corrected WD at stem center than with the uncorrected value: taking into account the effect of HW extractives on WD radial variations provides unbiased interpretation of biomass accumulation and tree mechanical strategies. Rather than a specific feature of heliophilic species, the increasing WD gradient is a shared strategy regardless of the shade tolerance habit. Finally, our study stresses to consider the occurrence of HW when using WD.

XRing—An R package to identify and measure tree-ring features using X-ray microdensity profiles

Climate influences tree-ring density and ring-density variables extracted from X-ray images have been widely used for climate reconstructions. The R package xRing was developed to identify and measure tree rings on X-ray microdensity profiles automatically. This package is available for free and it offers functions to visualize and calibrate X-ray images, to detect tree-ring borders and to identify earlywood-latewood transition using wood density variations at the inter- and the intra-ring scale. The most important functions are calibrateFilm, detectRings, correctRings, detectEwLw, and getDensity. Outputs of these functions are S3 objects, for which specific methods are provided, including plot and print. The non-linear relationship between optical density of the film and wood density is defined by the function calibrateFilm. The function detectRings detects tree rings using wood density profiles as input. This function uses the difference between local maximum and minimum values to identify tree-ring borders automatically. The correctRings function is used to call a Graphical User Interface (GUI) to visualize and to correct tree-ring borders manually. After correcting tree-ring borders, the detectEwLw function is used to compute earlywood and latewood widths by dividing rings according to relative intra-ring density changes. The getDensity function computes for each tree ring the minimum (maximum) density and the mean earlywood, latewood and whole-ring density. Finally, a list with dataframes with tree-ring width and density variables can be obtained using the function getRwls. One of the major advantages of xRing package is that requires little knowledge of R language, but at the same time it can be easily changed or adapted by experienced users.

Predicting wood density of growth increments of Douglas-fir stands in New Zealand

BackgroundDouglas-fir comprises 6% of New Zealand’s planted forest area and contributes to the national carbon sequestration estimate. Carbon stock changes in Douglas-fir stem wood can be calculated by multiplying the increment in stem volume under bark by the density of the growth sheath and the carbon fraction. This paper describes a new model developed to predict variation in wood density of Douglas-fir growth sheaths from known wood density drivers.MethodsDatasets used to parameterise the wood density model contained: (1) mean breast height (1.4 m above ground) outerwood (based on 50 mm long cores) density of 30 trees per stand from 32 semi-mature and mature stands with soil and climate data, for predicting wood basic density from environmental factors; (2) basic density of wood samples taken at breast height and at regular height intervals along the stem of 75 trees from 10 stands, for predicting the weighted mean wood basic density of pre-defined growth sheaths; and (3) breast height pith-to-bark radial density profiles based on 500 trees from 47 stands, for predicting wood density of individual annual growth rings at breast height. Linear and non-linear mixed models were developed using these data to explain the variation in wood density of growth sheaths.ResultsBreast height outerwood density was positively related to mean annual air temperature and negatively related to soil nitrogen fertility. This environmental model jointly explaining 83% of the variation in wood basic density at breast height of ring 30 from the pith. The radial pattern of wood density variation of annual growth rings at breast height was calibrated to a site using predictions from the environmental model. The ratio of growth sheath density to breast height ring density was applied to the predicted density of annual growth rings at breast height. This ratio decreased from 1.05 close to the pith to 0.95 in outerwood rings of mature trees, with ring number from pith explaining 49% of the variation in this ratio.ConclusionsA wood density model that incorporates the important drivers of variation in density of stem wood growth sheaths in New Zealand-grown Douglas-fir will improve the accuracy of carbon stock and stock change estimates in NZ’s planted forest estate. The new wood density model has been linked to the Forest Carbon Predictor which predicts carbon stocks in live and dead biomass pools from inventory plot measurements, site mean annual temperature, and soil nitrogen fertility information.

Щільність основних компонентів фітомаси стовбурів дерев робінії несправжньоакації в умовах Північного степу України

Здійснення лісогосподарських заходів, спрямованих на отримання якісної деревини, раціональне перероблення деревної сировини неможливі без аналізу варіабельності щільності компонентів надземної фітомаси стовбурів – деревини і кори. Наведено результати оцінювання середньої природної та базисної щільності деревини та кори стовбурів робінії несправжньоакації в умовах Північного Степу України. Дослідження проведено на 20 тимчасових пробних площах у робінієвих деревостанах у найпоширеніших групах типів лісу (С0–С1), віком від 3 до 89 років, продуктивністю IА–III класів бонітету. Проаналізовано зміну локальної щільності з віком модельних дерев та відносною висотою стовбурів. Середню локальну природну та базисну щільність фракцій фітомаси стовбурів розраховано з використанням комп'ютерної програми PLOT. Встановлено, що показники локальної природної та базисної щільності деревини і кори дерев робінії несправжньоакації в умовах Північного Степу України мають комбінований тип змін із відносною висотою стовбура: від окоренкової частини стовбура до відносної висоти 0,5h відбувається збільшення щільності з подальшим поступовим її зменшенням від середини стовбура до верхівки дерева. Локальна базисна щільність деревини молодих дерев (3–20 років) має стрімке зростання від окоренкової частини до відносної висоти 0,1h з подальшими змінами, характерними для інших груп віку. Найщільніша деревина і кора в дерев робінії несправжньоакації формується на середині стовбура (0,5h) у віці 41–60 років.

Biomass dynamics in a logged forest: the role of wood density

Wood density (WD) is believed to be a key trait in driving growth strategies of tropical forest species, and as it entails the amount of mass per volume of wood, it also tends to correlate with forest carbon stocks. Yet there is relatively little information on how interspecific variation in WD correlates with biomass dynamics at the species and population level. We determined changes in biomass in permanent plots in a logged forest in Vietnam from 2004 to 2012, a period representing the last 8 years of a 30 years logging cycle. We measured diameter at breast height (DBH) and estimated aboveground biomass (AGB) growth, mortality, and net AGB increment (the difference between AGB gains and losses through growth and mortality) per species at the individual and population (i.e. corrected for species abundance) level, and correlated these with WD. At the population level, mean net AGB increment rates were 6.47 Mg ha−1 year−1 resulting from a mean AGB growth of 8.30 Mg ha−1 year−1, AGB recruitment of 0.67 Mg ha−1 year−1 and AGB losses through mortality of 2.50 Mg ha−1 year−1. Across species there was a negative relationship between WD and mortality rate, WD and DBH growth rate, and a positive relationship between WD and tree standing biomass. Standing biomass in turn was positively related to AGB growth, and net AGB increment both at the individual and population level. Our findings support the view that high wood density species contribute more to total biomass and indirectly to biomass increment than low wood density species in tropical forests. Maintaining high wood density species thus has potential to increase biomass recovery and carbon sequestration after logging.

The timing of latewood formation determines the genetic variation of wood density in Larix kaempferi

The seasonal change of the wood formation stage, especially the timing of the cessation of cell division, are key to understanding the genetic difference of wood density. Wood density is important in terms of various wood properties and forest carbon sequestration properties. Wood density is genetically variable, although the mechanism that causes this variability is not well clarified. We hypothesized that wood formation dynamics differ genetically and that this affects wood density. We analyzed the dynamics of wood formation, including the timing of earlywood-latewood transition and the cessation of cell division, and their relationship to clonal differences in wood density using nine clones of Larix kaempferi, through microscopy observations and X-ray densitometry. Wood density showed a strong correlation with the proportion of latewood. The clonal variation of the timing of the earlywood-latewood transition was small. The timing of the cessation of cell division differed clonally by a maximum of 42.7 days and was correlated with the duration of latewood formation. The duration of latewood formation showed a correlation coefficient of 0.925 with the proportion of latewood. We described a hierarchical relationship that explained the genetic difference in wood density in mature L. kaempferi wood in the following sequence; the timing of cessation of latewood formation, the duration of latewood formation, the proportion of latewood, and wood density.

Basic wood density variations of Parkia velutina Benoist, a long-lived heliophilic Neotropical rainforest tree

L’analyse de la densité radiale des bois tropicaux révèle des profils linéaires et parfois curvilignes. Ce type d’étude ne prend généralement pas en compte les variations longitudinales, qui sont considérées comme similaires aux variations radiales. La présente étude vise à mettre en lumière (1) un nouveau profil curviligne de la densité radiale du bois, (2) des différences d’amplitude entre les gradients radiaux et longitudinaux et (3) à classer les variations de la densité du bois (DB) selon différentes échelles pour Parkia velutina, essence émergente des forêts humides néotropicales. La variabilité de la densité du bois a été évaluée sur des rondelles entières recueillies sur six arbres abattus et des carottes radiales prélevées sur dix arbres sur pied, et le taux de croissance en hauteur par des prélèvements sur un axe dominant. Cette essence montre des taux de croissance très élevés indicatifs d’un tempérament héliophile. La DB varie de 0,194 à 0,642 g/cm3, amplitude rarement observée au sein d’un même arbre. La variation radiale de la DB est curviligne, l’amplitude radiale étant généralement plus faible qu’en longitudinal. En conséquence, pour les arbres matures, les valeurs DB dans les houppiers sont plus élevées que dans le tronc. Les variations de la DB peuvent être très significatives à différentes échelles. Le partitionnement de la variance montre également que l’estimation intra-individu de la DB pour l’essence Parkia velutina est plus précise si l’on prend en compte à la fois le gradient longitudinal et radial.

Insights into intraspecific wood density variation and its relationship to growth, height and elevation in a treeline species.

The wood economics spectrum provides a general framework for interspecific trait-trait coordination across wide environmental gradients. Whether global patterns are mirrored within species constitutes a poorly explored subject. In this study, I first determined whether wood density co-varies together with elevation, tree growth and height at the within-species level. Second, I determined the variation of wood density in different stem parts (trunk, branch and twigs). In situ trunk sapwood, trunk heartwood, branch and twig densities, in addition to stem growth rates and tree height were determined in adult trees of Nothofagus pumilio at four elevations in five locations spanning 18° of latitude. Mixed effects models were fitted to test relationships among variables. The variation in wood density reported in this study was narrow (ca. 0.4-0.6gcm-3 ) relative to global density variation (ca. 0.3-1.0gcm-3 ). There was no significant relationship between stem growth rates and wood density. Furthermore, the elevation gradient did not alter the wood density of any stem part. Trunk sapwood density was negatively related to tree height. Twig density was higher than branch and trunk densities. Trunk heartwood density was always significantly higher than sapwood density. Negative across-species trends found in the growth-wood density relationship may not emerge as the aggregate of parallel intraspecific patterns. Actually, trees with contrasting growth rates show similar wood density values. Tree height, which is tightly related to elevation, showed a negative relationship with sapwood density.