Differences In Wood Density Research Articles

Analysis of surface roughness of chemically impregnated Scots pine processed using frame-sawing machine

ABSTRACT The objective of this work was to evaluate the effect of the impregnation process of pine wood (Pinus sylvestris L.) on roughness parameters of the surface processed on a frame sawing. The samples were dried and impregnated using a commercial procedure by a local company. The touch method with the use of measuring stylus (pin) was employed to determine of surface roughness of the samples considering parameters, namely, arithmetical mean roughness value (Ra), total height of the roughness profile (Rt), maximum height of roughness profile (Rz) and root-mean-square roughness (Rq). All measured values of the analysed surface roughness parameters were normalised by the raw density of wood in order to eliminate the effect of differences in wood density and moisture content of the tested samples of impregnated and non-impregnated pine. Generally, no effect of feed per tooth was observed for the analysed values of f z1 = 0.11 mm and f z2 = 0.22 mm on the surface roughness parameters. Only for the parameter Rq of impregnated wood was a significant effect of feed per tooth observed. The effect of the pine wood impregnation process on all analysed surface roughness parameters was observed for both analysed feeds per tooth.

Influence of Wood Knots of Chinese Weeping Cypress on Selected Physical Properties

The effects of wood knots of Chinese weeping cypress (Cupressus funebris Endl.) wood on selected physical and color properties were investigated. Thirty samples of live knots, dead knots, and clear wood groups were selected for experiments to determine the physical properties of wood density, wood shrinkage, wood swelling, and wood color. The experimental analysis results showed that the wood density values are in the order: dead knots > live knots > clear wood, with a significant difference in wood density between different groups (p < 0.01). In addition, the values of the air-dry volumetric wood shrinkage, air-dry volumetric wood swelling, oven-dry volumetric wood shrinkage, and oven-dry volumetric wood swelling ratios are in the order: dead knots > live knots > clear wood, being consistent with a variation in wood density. Three groups of wood colors were provided: the color of clear wood is light, the color of live knots is reddish, and the color of live knots is blackish, in relative terms. The chromatic aberration between the three groups can be identified, and the wood color difference resulted from the discrepancy in the lightness index.

A comparison of radial increment and wood density from beech provenance trials in Slovenia and Hungary

Provenance trials are a valuable source of information, especially in species such as European beech (Fagus sylvatica L.), which will likely increase its distribution due to global warming. The current study compares radial increment and wood density of beech provenances in the juvenile development stage from contrasting environments in Europe (Belgium, Slovenia, Czech Republic, Italy) planted at a mesic to wet site in Slovenia and a xeric site in Hungary. Existing data (past measurements of diameters and height) were combined with new measurements of tree height, diameter, dendrochronological and resistance drilling density measurements to assess differences in provenance radial growth. The wood density data were evaluated using a Bayesian general linear model. In order to study the differences in radial increment in more detail, two weather-wise contrasting years (2014 and 2017) were selected from the last decade, based on calculations of the 12-month Standardized Precipitation-Evapotranspiration Index. The differences in average tree-ring width among provenances at each sampled site appeared to be relatively small when averaged over a whole decade of data. However, according to year-to-year data, some provenances grew faster than others, especially in favorable weather conditions. In unfavorable conditions, the differences in tree-ring widths among provenances were smaller. For most provenances, variation in tree-ring widths within the same provenance increased in unfavorable conditions. The difference between the provenances with the highest and lowest wood densities at both locations did not exceed 5%. The model results indicate that the Idrija (Slovenia) provenance probably has a higher median wood density than other studied provenances at both sites. Although the current study confirmed some differences in wood density between provenances and trial locations, the differences are negligible in practice due to their low magnitude and the fact that the analyzed trees were still juvenile. As beech has a diffuse-porous wood, negligible differences in wood density would also be expected in adult trees. Beech provenances for planting in relation to changing weather should probably be chosen for their ability to survive more extreme weather events rather than to improve radial increment or wood density, especially as the differences in wood density of juvenile trees are relatively small.

Short communication: Basic wood density and moisture content of 14 shrub species under two different site conditions in the Chilean Mediterranean shrubland

Aim of the study: The aim of this study is to provide information on species-specific basic wood density (g cm-3) and moisture content (%) in Mediterranean shrublands. Area of study: The study covers two sites of the sclerophyllous shrubland in central Chile, Cortaderal (34°35’S 71°29’W) and Miraflores (34°08’S 70°37’W), characterized by different climatic and topographic conditions. Material and methods: The sampling area covers 4,000 m2 over four plots at two sites. Shrub species were identified and size-related attributes such as height and crown size measured. A total of 322 shrubs were sampled at 0.3 m aboveground to determine basic wood density and moisture content. Species-specific differences and similarities were analyzed by multiple pairwise comparisons (post-hoc tests) and by ordination and hierarchical clustering. Main results: We found high variation across species in wood density (0.46-0.77 g cm-3) and moisture content (41.6-113.1%), with many significant differences among species in wood density and among sites in moisture content. Because intraspecific variability could not be explained by shrub size and pronounced differences in wood density (0.49-0.64 g cm-3) also occurred between species of the same genus (e.g., Baccharis linearis and Baccharis macraei), our results suggested that phylogenetic affinity may be less important than adaptation to local conditions. Research highlights: The values presented here were variable according to the type of species and environmental conditions, necessitating the determination of basic wood density (BWD) and moisture content at site – and species-specific level. The provided BWD estimates allow converting green volume to aboveground biomass in shrubland areas and are an essential source of information for estimating the carbon stocks.

Factors That Affect the Mechanical Strength of Archaeological Wood-A Case Study of 18th-Century Wooden Water Pipes from Bóżnicza Street in Poznań, Poland.

Large amounts of archaeological wood are often excavated during groundworks in cities and towns. Part of the unearthed artefacts is usually saved, conserved and then presented in museums. However, if the finding contains several similar objects, some of them could potentially be further employed for some other practical purposes. The research aimed to determine the mechanical performance of the remains of wooden water mains excavated at Bóżnicza street in Poznań, Poland and evaluate its potential usefulness for any practical purposes. First, wood density was determined along with its mechanical strength in compression. The density of archaeological wood identified as Scots pine was lower than contemporary pinewood (383 kg × m−3 vs. 572 kg × m−3); therefore, its mechanical properties in compression tests were also lower, as expected, making the wood unsuitable for any practical applications. However, the differences in modulus of elasticity and compressive strength were not justified by the differences in wood density. Further infrared spectroscopy and X-ray diffraction analyses revealed additional differences in chemical composition and cellulose crystallinity between archaeological and contemporary wood. The results indicated the decrease in carbohydrate content and cellulose crystallinity in degraded wood, which, in addition to wood density, apparently contribute to the deterioration in mechanical strength of archaeological wood. The case study of the excavated archaeological wooden pipes shows that they have historical value but are not useful for practical purposes. It also revealed that not only wood density but also its chemical composition and cellulose crystallinity level has a substantial impact on the wood mechanical properties, particularly in compression.

Seasonal variations of auxin and gibberellin A4 levels in cambial-region tissues of three conifers (Pinus elliottii, Chamaecyparis obtusa, and Cryptomeria japonica) with inherently different wood densities

We previously reported the species-specific annual ring formation characteristics of three conifers (slash pine (Pinus elliottii), hinoki (Japanese cypress, Chamaecyparis obtusa) and sugi (Japanese cedar, Cryptomeria japonica)) grown in the same stand over 2 years. We found that the species-specific annual ring formation characteristics affected the inherent difference in wood density among these conifers (slash pine > hinoki > sugi). Plant hormones in cambial-region tissues were believed to affect annual ring formation. However, seasonal variation of the amounts of plant hormones in cambial-region tissues had only been examined in a few tree species. In this study, as the first step to elucidating the role of plant hormones in annual ring formation in conifers, we report the seasonal variations of the auxin (indole acetic acid, IAA) and gibberellin A4 (GA4) levels in cambial-region tissues and their effects on annual ring formation in three conifers (slash pine, hinoki, and sugi) with inherently different wood densities.Sugi (small wood density) had significantly higher levels of IAA and formed more tracheids in the early season than in the late season, although slash pine (large wood density) had higher levels of IAA and formed significantly more tracheids in the late season than in the early season. Hinoki (intermediate wood density) had constant IAA levels and formed a constant number of tracheids throughout the season. There were significant positive correlations between the levels of IAA in cambial-region tissues and the number of tracheids formed during late season in the two conifer species. A close relationship was observed between the seasonal ratio of the IAA levels (late/early season) and wood density. No consistent trend in the change in the level of IAA during the transition from earlywood to latewood formation was recognized among the three conifers. The IAA levels in slash pines were significantly higher than those in sugi and hinoki. The GA4 levels had no significant effect on number of tracheids formed in the three conifers. These results suggest that the species-specific seasonal variation patterns of the IAA levels might lead to the inherent differences in wood density among these three conifers through species-specific characteristics in the formation of annual rings.

Variations in temperate forest stem biomass ratio along three environmental gradients are dominated by interspecific differences in wood density

Variations in temperate forest stem biomass ratio along three environmental gradients are dominated by interspecific differences in wood density

Functional Relationships Between Branch and Stem Wood Density for Temperate Tree Species in North America

Wood density is strongly related to key aspects of tree physiological performance. While many studies have examined wood density in different parts of trees for a variety of reasons, there are very few studies that have compared within-tree density variation across many trees, of many species, drawn from a large geographic area. Here, a large data set representing trees of 78 species/genera in the Eastern United States was compiled and analyzed to explore branch to main stem wood basic density relationships. The expectation was that differences in stem versus branch wood density among trees would be due to both genetic constraints and plastic responses in wood properties, due to tree growth responses to external environments. The results show a wide tree-to-tree variation in average branch density, relative to main stem density. However, there was a general pattern for overstory tree species to have high tree branch density relative to stem density, at lower stem densities, and a declining branch to stem wood density ratio as stem density increased. Evergreen gymnosperms showed the strongest change in branch to stem wood density ratios over the range of stem wood densities and deciduous angiosperms the least; deciduous gymnosperms showed an intermediate pattern, but with generally higher branch- than stem- wood densities. More cold-hearty, shade-tolerant / drought-intolerant, evergreen gymnosperms, growing at higher latitudes, showed higher branch to stem density ratios than more shade-intolerant / drought tolerant evergreen gymnosperms growing at lower latitudes. Across all trees, canopy position had a significant influence on branch to stem density relationships, with higher branch to stem density ratios for canopy dominant trees and successively lower branch to stem density ratios for trees in successively inferior canopy positions (in terms of light availability). Understory tree species, which remain in the forest understory at maximum height, showed generally lower branch than stem densities over a wide range of stem densities. The results suggested that tradeoffs between mechanical safety and whole-tree hydraulic conductance are driving within-tree differences in wood density and highlighted the need for more detailed examinations of within-tree density variation at the whole-tree level.

An evaluation of fiber biometry and nanomechanical properties of different Eucalyptus species

Wood fibers from seven Eucalyptus species were collected to investigate the relationships among species, fiber biometry, and nanomechanical properties. The results indicated significant differences in wood density, coarseness, fiber length, fiber width, and cell wall thickness among the different Eucalyptus species. The nanomechanical properties of the S2 cell wall layer also showed significant differences among the Eucalyptus species. The elasticity modulus ranged from 16 to 19 GPa, the hardness spanned 0.24 to 0.31 GPa, and the ductility ratio was between 54 and 68. Moreover, significant correlations were observed for hardness versus cell wall thickness (r = 0.87), and elasticity modulus versus crystallinity index (r = 0.80) and crystallite size (r = 0.68). Among the evaluated species, E. dunnii showed the highest elasticity modulus, highest hardness average, and the highest crystallinity index. The range of nanomechanical values indicated that Eucalyptus wood fibers are suitable for the development of new composite materials or engineering products by selecting the most adequate species for each use according to its properties.

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

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

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.

Tree growth traits and social status affect the wood density of pioneer species in secondary subtropical forest.

Wood density (WD) is not only an important parameter to estimate aboveground biomass but also an indicator of timber quality and plant adaptation strategies to stressful conditions (i.e., windthrow, pests, and pathogens). This study had three objectives: (1) to compare WD among seven subtropical tree species; (2) to determine how tree growth traits may influence possible differences in WD between the pioneer and shade‐tolerant species; and (3) to examine whether or not WD differs by tree social status (dominant vs. suppressed trees) within species. To do this, 70 trees were destructively harvested. From each tree, disks at different stem heights were obtained and subjected to a method of stem analysis to measure whole tree level WD. The results showed that WD differed significantly among the seven species (p < .001). Their average WD was 0.537 g/cm3, ranging from 0.409 g/cm3 for Choerospondias axillaris to 0.691 g/cm3 for Cyclobalanopsis glauca. The average WD of the four pioneer species (0.497 ± 0.13 g/cm3) was significantly lower (p < .01) than that of the three shade‐tolerant species (0.589 ± 0.12 g/cm3). The WD of the pioneers had a significant positive correlation with their stem diameter at breast height (DBH), tree height (H), and tree age, but WD had a significant negative correlation with relative growth rate (RGR). In contrast, the WD of the shade‐tolerant tree species had no significant relationships with DBH, H, tree age, or RGR. The dominant trees of the pioneer species had a higher WD than the suppressed trees, whereas the shade‐tolerant species had a lower WD for dominant trees than the suppressed trees. However, the differences in WD between dominant and suppressed trees were not significant. Taken together, the results suggest that classifying species into pioneer and shade‐tolerant groups to examine the effects of tree growth traits and social status could improve our understanding of intra‐ and interspecific variation in WD among subtropical tree species.

Carbon stocks and dynamics at different successional stages in an Afromontane tropical forest

Abstract. As a result of different types of disturbance, forests are a mixture of stands at different stages of ecological succession. Successional stage is likely to influence forest productivity and carbon storage, linking the degree of forest disturbance to the global carbon cycle and climate. Although tropical montane forests are an important part of tropical forest ecosystems (ca. 8 %, elevation &gt; 1000 m a.s.l.), there are still significant knowledge gaps regarding the carbon dynamics and stocks of these forests, and how these differ between early (ES) and late successional (LS) stages. This study examines the carbon (C) stock, relative growth rate (RGR) and net primary production (NPP) of ES and LS forest stands in an Afromontane tropical rainforest using data from inventories of quantitatively important ecosystem compartments in fifteen 0.5 ha plots in Nyungwe National Park in Rwanda. The total C stock was 35 % larger in LS compared to ES plots due to significantly larger above-ground biomass (AGB; 185 and 76 Mg C ha−1 in LS and ES plots), while the soil and root C stock (down to 45 cm depth in the mineral soil) did not significantly differ between the two successional stages (178 and 204 Mg C ha−1 in LS and ES plots). The main reasons for the difference in AGB were that ES trees had significantly lower stature and wood density compared to LS trees. However, ES and LS stands had similar total NPP (canopy, wood and roots of all plots ∼ 9.4 Mg C ha−1) due to counterbalancing effects of differences in AGB (higher in LS stands) and RGR (higher in ES stands). The AGB in the LS plots was considerably higher than the average value reported for old-growth tropical montane forest of south-east Asia and Central and South America at similar elevations and temperatures, and of the same magnitude as in tropical lowland forest of these regions. The results of this study highlight the importance of accounting for disturbance regimes and differences in wood density and allometry of tree species dominating at different successional stages in an attempt to quantify the C stock and sink strength of tropical montane forests and how they may differ among continents.

Wood Density and Mechanical Properties of Pinus kesiya Royle ex Gordon in Malawi

Successful development of an appropriate tree breeding strategy and wood utilization requires information on wood properties. This study was therefore conducted to assess wood density and mechanical properties of Pinus kesiya Royle ex Gordon grown in Malawi. Wood samples from six families of P. kesiya at the age of 30 years were used for the study. The estimated mean wood density, Modulus of Elasticity (MoE), Modulus of Rupture (MoR) and moisture content were 0.593 ± 0.001 g/cm3, 13.46 ± 0.07 GPa, 113.67 ± 0.57 MPa and 12.08% ± 0.03%, respectively. There were statistically significant (p &lt; 0.001) differences in wood density and mechanical properties along the radial direction and stem height. Wood density and mechanical properties increased from pith to bark and decreased from the butt upwards. There were no significant (p &gt; 0.05) differences in wood density and mechanical properties among the families. This is an indication that any tree among the families can be selected for tree improvement programs if density is considered as a variable. Wood density had a strong positive significant linear relationship with both MoE (r = 0.790; p &lt; 0.001) and MoR (r = 0.793; p &lt; 0.001). This suggests that it has the potential to simultaneously improve the wood density and mechanical properties of this species. Therefore, controlling wood density for the tree improvement program of P. kesiya in Malawi would have a positive impact on mechanical properties.

Wood density, but not leaf hydraulic architecture, is associated with drought tolerance in clones of Coffea canephora

Key message This study highlights that wood density integrates the xylem structural changes and plays a key role in drought tolerance at the intraspecific level in clones of robusta coffee. Robusta coffee (Coffea canephora) is largely cropped in regions where drought stress is the major bottleneck limiting crop yields. We hypothesized that clonal differences in wood density (D w) would be reflected in xylem anatomical differences with associated consequences for hydraulic functioning and ultimately drought tolerance. We assessed the major functional properties of water conduction systems at both the leaf and stem levels in 8-year-old clones of robusta coffee with varying degrees of drought tolerance. The plants were grown outdoors in 24-L pots and either irrigated or subjected to a 4-month water deficit. Upon drought imposition, increased D w, primarily associated with a rearrangement of the fiber matrix and secondarily associated with narrower vessels (although more numerous per cross-sectional area), was correlated with tolerance to hydraulic dysfunctions. Some coordination at the leaf level concerning hydraulic and stomatal anatomical patterns, with stem structural properties, was observed under ample irrigation, but this coordination was decoupled by the imposed drought stress. In conclusion, our data suggest a role for D w in drought tolerance in coffee; however, drought tolerance implies that clones that successfully thrive under low water supply might have compromised fitness under ample irrigation, suggesting a trade-off between D w and the conduction capacity in coffee.

Structural features of dioxane lignin from Eucalyptus globulus and their relationship with the pulp yield of contrasting genotypes

The chemical structure of dioxane lignins isolated from two groups of Eucalyptus globulus genotypes with contrasting pulpwood characteristics were evaluated. Six genotypes were selected and separated in two groups (G1 and G2) based on differences in wood density, pulp yield and chemical characteristics. Lignin was isolated from both milled wood and kraft pulps produced at kappa number 16, and were characterized by different techniques such as FTIR, elemental analysis, molar mass distribution and 31P NMR spectroscopy. From the different characteristics evaluated, some were determined as more relevant, such as syringyl (S) and guaiacyl (G) amounts, S/G ratio and condensed biphenyl units, were correlated with the pulp yield. High correlations were found between pulp yield and syringyl units (R2 = 0,69), and pulp yield and syringyl/guaicyl ratio (R2 = 0,88). The condensed 5-5 biphenyl units presented a negative correlation with pulp yield (R2 = 0,76). The information obtained explained part of the difference in pulpability of the contrasting genotypes and can be used for the selection and improvement of the species for the pulp and paper industry.

Retention and Structure of Xylans from Eucalyptus Globulus Genotypes with Different Pulpwood Characteristics

In this work, six different genotypes of Eucalyptus globulus were selected on the basis of their differences in wood density and pulp yield. The trees were separated into two groups of three genotypes each: group I (samples Eg1, Eg2, and Eg3) presented wood density values of 547–573 kg/m3 and pulp yields of 52.7–54.6%; group II (samples Eg4, Eg5, and Eg6) presented wood density of 471–485 kg/m3 and pulp yields of 49.8–52.3%. Chemical characterization showed that genotypes of group I also presented high glucose and low lignin content as compared with genotypes from group II. Xylans content was lower in samples of group I than group II. Kraft pulps from group I presented high retention of xylans in comparison with pulps from group II. This behavior was associated with a high degree of substitution (DS) of the xylose units with methylglucuronic acids in wood and in kraft pulps in samples of group I compared with group II. Xylans isolated from wood samples of group I also presented slightly higher molar mass than xylans from group II. Results showed that xylans from a single species presented differences in their retention and structure that affected the pulp yield of E. globulus.

Decayed Wood Affecting the Attraction of the Pest Arboretum Termite Nasutitermes corniger (Isoptera: Termitidae) to Resource Foods

Nasutitermes corniger shows preferential feeding for the wood of different tree species, but it is not known whether attractiveness is a function of the state of decay. This study examined the foraging behavior of N. corniger towards wood in different stages of decay. Wood was exposed to weather for durations of 0, 3, 6 or 9 months. Then the wood was placed in a standard foraging arena with termites. Exploration and recruitment behavior were recorded for 1 h. Separate bioassays were conducted for three species: Pinus elliottii, Eucalyptus grandis and Manilkara huberi. In the tests with P. elliottii and E. grandis, more individuals were recruited to wood decayed for 6 months (191 and 185, respectively) than to undecayed wood (12 and 69, respectively). Similarly, more individuals were recruited to decayed M. huberi wood than undecayed, but only after 9 months (249 and 7, respectively). Decayed wood has therefore been demonstrated to be more attractive to N. corniger than undecayed wood. The different decomposition rates necessary to increase attractiveness may be explained by differences in wood density.

Variation in wood density and carbon content of tropical plantation tree species from Ghana

Most research on carbon content of trees has focused on temperate species, with less information existing for tropical trees and very little for tropical plantations. This study investigated factors affecting the carbon content of nineteen tropical plantation tree species of ages seven to twelve and compared carbon content of Khaya species from two ecozones in Ghana. For all sample trees, volume of the main stem, wood density, wood carbon (C) concentration and C content were determined. Estimated stem volume for the 12-year-old trees varied widely among species, from 0.01 to 1.04 m3, with main stem C content ranging from 3 to 205 kg. Wood density among species varied from 0.27 to 0.76 g cm−3, with faster growing species exhibiting lower density. Significant differences in wood density also occurred with position along the main stem. Carbon concentration also differed among tree species, ranging from 458 to 498 g kg−1. Differences among species in main stem C content largely reflected differences among species in estimated main stem volume, with values modified somewhat by wood density and C concentration. The use of species-specific wood density values was more important for ensuring accurate conversion of estimated stem volumes to C content than was the use of species-specific C concentrations. Significant differences in wood density did exist between Khaya species from the wet and moist semi-deciduous ecozones, suggesting climatic and site factors may also need to be considered. Wood densities for these plantation grown trees were lower than literature values reported for the same species in natural forests, suggesting that the application of data derived from natural forests could result in overestimation of the biomass and C content of trees of the same species grown in plantations.

Hydraulic differences along the water transport system of South American Nothofagus species: do leaves protect the stem functionality?

Hydraulic traits were studied for six Nothofagus species from South America (Argentina and Chile), and for three of these species two populations were studied. The main goal was to determine if properties of the water conductive pathway in stems and leaves are functionally coordinated and to assess if leaves are more vulnerable to cavitation than stems, consistent with the theory of hydraulic segmentation along the vascular system of trees in ecosystems subject to seasonal drought. Vulnerability to cavitation, hydraulic conductivity of stems and leaves, leaf water potential, wood density and leaf water relations were examined. Large variations in vulnerability to cavitation of stems and leaves were observed across populations and species, but leaves were consistently more vulnerable than stems. Water potential at 50% loss of maximum hydraulic efficiency (P(50)) ranged from -0.94 to -2.44 MPa in leaves and from -2.6 to -5.3 MPa in stems across species and populations. Populations in the driest sites had sapwood and leaves more vulnerable to cavitation than those grown in the wettest sites. Stronger diurnal down-regulation in leaf hydraulic conductance compared with stem hydraulic conductivity apparently has the function to slow down potential water loss in stems and protect stem hydraulics from cavitation. Species-specific differences in wood density and leaf hydraulic conductance (K(Leaf)) were observed. Both traits were functionally related: species with higher wood density had lower K(Leaf). Other stem and leaf hydraulic traits were functionally coordinated, resulting in Nothofagus species with an efficient delivery of water to the leaves. The integrity of the more expensive woody portion of the water transport pathway can thus be maintained at the expense of the replaceable portion (leaves) of the stem-leaf continuum under prolonged drought. Compensatory adjustments between hydraulic traits may help to decrease the rate of embolism formation in the trees more vulnerable to cavitation.