Differences In Wood Density Research Articles

Stem radial increment of forest and savanna ecotypes of a Neotropical tree: relationships with climate, phenology, and water potential

The aim of the present study was to investigate differences in stem radial increment between the savanna and forest ecotypes of Plathymenia reticulata at an ecotonal site. It was hypothesised that even under similar climate conditions, the savanna and forest ecotypes exhibit differences in radial growth, phenology, and water status because of differences in wood density. Stem radial increment, phenology, and water potential were evaluated monthly. The radial increment was positively related to precipitation and displayed no increment (or decrement) in months with low rainfall. A negative relationship was observed between radial growth and wood density, with the forest ecotype exhibiting a higher radial increment than the savanna ecotype. Midday water potential (ΨMD) was also negatively related to wood density. Compared to the forest ecotype, the savanna ecotype displayed lower values of ΨMD during the dry season and started leaf senescence earlier at the beginning of the dry season. Leaf fall improved water status, resulting in leaf flushing even without a significant increase in rainfall. Radial growth significantly increased only after the crown leaf cover was completed. The results confirmed the importance of wood density in the differential responses of ecotypes in relation to growth, water status, and phenology.

Effects of radial growth, tree age, climate, and seed origin on wood density of diverse jack pine populations

Several models of the effects of silviculture, radial growth, and tree age on wood density have been developed, but they have rarely considered the roles of diverse seed origins and climate. We developed a model to test the effects of radial growth, tree age, climate, and seed-source origins on wood density in 21 diverse populations of jack pine in a common garden in Petawawa, Ontario, Canada over the last 24 years using a linear mixed-effects model. Although we found significant differences in wood density among diverse seed origins, there were no differences between seed origins having the same ring age and ring width, indicating an indirect effect on wood density of seed-source origin via radial growth. High variation in wood density among trees within the same population and between populations indicated high genetic control of wood density. The climate effect was significant on wood density in all populations, but smaller when radial growth was controlled. Climate effect did not differ significantly among populations. Precipitation in July negatively affected latewood density, whereas precipitation in May in the current year and September of the previous year negatively affected earlywood density. We concluded that a single model of jack pine wood density and radial growth could be used, either controlling for climate effects or not, as the relationship between wood density and radial growth is preserved among the diverse populations, and the climate effect controlling for radial growth in the model was only slight.

Intra- and interspecific variation in wood density and fine-scale spatial distribution of stand-level wood density in a northern Thai tropical montane forest

Abstract:Tropical tree wood density is often related to other species-specific functional traits, e.g. size, growth rate and mortality. We would therefore expect significant associations within tropical forests between the spatial distributions of stand-level wood density and micro-environments when interspecific variation in wood density is larger than intraspecific variation and when habitat-based species assembly is important in the forest. In this study, we used wood cores collected from 515 trees of 72 species in a 15-ha plot in northern Thailand to analyse intra- and interspecific variation in wood density and the spatial association of stand-level wood density. Intraspecific variation was lower than interspecific variation (20% vs. 80% of the total variation), indicating that species-specific differences in wood density, rather than phenotypic plasticity, are the major source of variation in wood density at the study site. Wood density of individual species was significantly negatively related to maximum diameter, growth rate of sapling diameter and mortality of saplings. Stand-level mean wood density was significantly negatively related to elevation, slope convexity, sapling growth rate and sapling mortality, and positively related to slope inclination. East-facing slopes had significantly lower stand-level mean wood densities than west-facing slopes. We hypothesized that ridges and east-facing slopes in the study forest experience strong and frequent wind disturbance, and that this severe impact may lead to faster stand turnover, creating conditions that favour fast-growing species with low wood density.

Effects of tree height on branch hydraulics, leaf structure and gas exchange in California redwoods

We examined changes in branch hydraulic, leaf structure and gas exchange properties in coast redwood (Sequoia sempervirens) and giant sequoia (Sequoiadendron giganteum) trees of different sizes. Leaf-specific hydraulic conductivity (k(L)) increased with height in S. sempervirens but not in S. giganteum, while xylem cavitation resistance increased with height in both species. Despite hydraulic adjustments, leaf mass per unit area (LMA) and leaf carbon isotope ratios (delta(13)C) increased, and maximum mass-based stomatal conductance (g(mass)) and photosynthesis (A(mass)) decreased with height in both species. As a result, both A(mass) and g(mass) were negatively correlated with branch hydraulic properties in S. sempervirens and uncorrelated in S. giganteum. In addition, A(mass) and g(mass) were negatively correlated with LMA in both species, which we attributed to the effects of decreasing leaf internal CO(2) conductance (g(i)). Species-level differences in wood density, LMA and area-based gas exchange capacity constrained other structural and physiological properties, with S. sempervirens exhibiting increased branch water transport efficiency and S. giganteum exhibiting increased leaf-level water-use efficiency with increasing height. Our results reveal different adaptive strategies for the two redwoods that help them compensate for constraints associated with growing taller, and reflect contrasting environmental conditions each species faces in its native habitat.

Wood density and its radial variation in six canopy tree species differing in shade-tolerance in western Thailand

Background and AimsWood density is a key variable for understanding life history strategies in tropical trees. Differences in wood density and its radial variation were related to the shade-tolerance of six canopy tree species in seasonally dry tropical forest in Thailand. In addition, using tree ring measurements, the influence of tree size, age and annual increment on radial density gradients was analysed.MethodsWood density was determined from tree cores using X-ray densitometry. X-ray films were digitized and images were measured, resulting in a continuous density profile for each sample. Mixed models were then developed to analyse differences in average wood density and in radial gradients in density among the six tree species, as well as the effects of tree age, size and annual increment on radial increases in Melia azedarach.Key ResultsAverage wood density generally reflected differences in shade-tolerance, varying by nearly a factor of two. Radial gradients occurred in all species, ranging from an increase of (approx. 70%) in the shade-intolerant Melia azedarach to a decrease of approx. 13% in the shade-tolerant Neolitsea obtusifolia, but the slopes of radial gradients were generally unrelated to shade-tolerance. For Melia azedarach, radial increases were most-parsimoniously explained by log-transformed tree age and annual increment rather than by tree size.ConclusionsThe results indicate that average wood density generally reflects differences in shade-tolerance in seasonally dry tropical forests; however, inferences based on wood density alone are potentially misleading for species with complex life histories. In addition, the findings suggest that a ‘whole-tree’ view of life history and biomechanics is important for understanding patterns of radial variation in wood density. Finally, accounting for wood density gradients is likely to improve the accuracy of estimates of stem biomass and carbon in tropical trees.

Impacts of forest harvesting related soil disturbance on end-of-rotation wood quality and quantity in a New Zealand radiata pine forest

The long-term effect of soil disturbance (litter removal, topsoil removal and compaction) from forest harvesting on wood quality and quantity of second-rotation Pinus radiata growing on a clay loam soil, was assessed at the end the rotation, 26 years after planting. Relative to Control plots, average tree and stand total volume at rotation end was not significantly affected by litter removal and nil or light compaction, but was significantly reduced by 28% by litter and topsoil removal and moderate subsoil compaction, and further reduced by 38% by heavy compaction. Wood density at breast height in the inner rings of trees in the most disturbed treatments was elevated by up to 30 kg m. This occurred because these treatments were more N deficient as reflected by foliar N levels during the first 11 years of growth relative to the Control. However, no treatment differences in wood density were evident in outer rings, and by rotation age overall mean density did not differ significantly between treatments. Neither acoustic velocity of standing trees, nor acoustic velocity of logs, was significantly affected by soil disturbance, indicating that stiffness of lumber cut from trees in the trial was likely to be similar for all treatments. Economic impacts of soil disturbance and compaction on this soil type will therefore result largely from the considerable negative impacts on final tree size, with little or no compensation from improved wood properties.–3

Clonal differences in log end splitting in Eucalyptus grandis in relation to age, parent performance, growth rate and wood density in two even-aged trials in Mpumalanga, South Africa

This paper discusses the juvenile–mature correlation of log end splitting among Eucalyptus grandis clones from two trials and how differences in splitting relate to differences in wood density, pith-to-bark gradient and growth rate. Two approximately 20-year-old Eucalyptus grandis clonal trials at Bergvliet plantation were sampled. The first trial (Trial A) consisted of clones of eight ortets (genotypes) specifically selected for their widely different propensities to develop end splitting. The second trial (Trial B) consisted of 80 clones and one seedling control. From the latter trial 15 clones were selected in such a manner that they constituted three groups of clones representing a combination of high- and low-volume producers and, among the high-volume producers, clones exhibiting high and low propensities towards end splitting. The fourth group represented the seedling control. Trial A showed highly significant clonal differences in splitting, basic wood density, as well as its pith-to-bark gradient. No relationship of splitting with differences in growth rate, density or density gradient was found. The clones derived from the low- and high-splitting ortets maintained their general statuses as low and high splitters over a considerable period of time, but some of the individual clones did not reflect the performance of the ortets from which they were derived. Trial B revealed that clones classified as good-volume producers at the age of 65 months still outperformed the clones classified as low-volume producers approximately 15 years later. No significant differences in average wood density between the groups of clones studied was found, irrespective of differences in growth rate and degree of splitting, but trees from the slow-growing group of clones were significantly more variable across the radius in average wood density. The outcome of both trials confirmed results of many previous studies on this species, in that rapid and uniform growth has no significant detrimental effect on wood density or its rate of change across the radius of the tree. It may, in fact, be associated with increased uniformity from pith to bark with increasing age, sometimes resulting in slightly increased overall wood density.

Wood density within Norway spruce stems

We studied the variation in average wood density of annual rings, earlywood density, and latewood density in addition to ring width and latewood percentage within Norway spruce (Picea abies (L.) Karst.) stems from the pith to the bark, and from the stem base towards the stem apex. Moreover, the variation in wood density within annual rings was studied at the different heights and radial positions in the stem. The material consisted of 85 trees from central and south-eastern Finland. Variation between the annual rings accounted for 11–27% of the total variation in wood density. Only small differences (3–6%) in wood density were found between different heights in the stem. The largest (49–80%) variation in wood density was found within the annual rings. The difference in wood density between earlywood and latewood was smaller in the rings near the pith than in the outer rings. The increasing wood density from the pith outwards was related to increasing latewood density and latewood percentage, whereas the earlywood density increased only slightly from the pith outwards. In a given cambial age (i.e., given rings from the pith), the average wood density of annual rings increased with increasing stem height. In contrast, in the rings formed in the same calendar years (i.e., given rings from the bark), the average wood density of annual rings decreased with increasing stem height. The results of this study verify our knowledge of wood density variation and can further contribute to creating models to predict wood density.

Overturning resistance of western redcedar and western hemlock in mixed-species stands in coastal British Columbia

Specific information about the applied forces that cause trees to fail is required to validate mechanistic models of windthrow in different forest types. Static tree-pulling tests were conducted to examine the overturning resistance of western redcedar ( Thuja plicata Donn ex D. Don) and western hemlock ( Tsuga heterophylla (Raf.) Sarg.) in a mixed species second-growth stand in coastal British Columbia. Although widely used, tree-pulling techniques are not standardized. Data from three inclinometers were used to estimate stem deflection, which was found to increase with tree slenderness. Differing methods of fitting stem curvature had a small effect on estimates of self-loading at failure. The distance of the pivot point from the centre of the stem base increased with tree diameter. Accounting for the correct self-loading at failure produced a small difference in the overall turning moment regressions but did not improve the fit of these regressions. However, this difference increased with tree size and warrants consideration in future tree-pulling tests with large or plate-rooted trees. The stem mass – overturning resistance relationship had the best fit and was not significantly different for these species in spite of their differences in wood density and stem form.

Do browsing elephants damage female trees more?

AbstractHerbivory in unisexual plants has mainly been assessed in studies of invertebrates, mostly insects. At a different scale of disturbance, browsing by large animals has rarely been studied. Elephants can seriously damage or kill trees by removing parts of the canopy, debark, or break the stem. We compared browsing by African elephants (Loxodonta africana) in male and female Marula trees (Sclerocarya birrea ssp. caffra). We expected females to incur more damage because of their sweet and fleshy fruits, known to attract elephants from far. Following this, we expected females to give more resistance through a denser branch wood that would break off at a larger diameter than in males. We tested this by pulling branches down to simulate elephant browsing as to compare branch resistance and design. All trees showed signs of browsing and females were generally more injured. However, there was no sexual difference in wood density and diameter at breaking point. Female branches were shorter, less ramified and carried fewer reproductive shoots than male branches. This sexual dimorphism could result from costly reproductive allocation in females and sexual selection, promoting intensive male flowering. Indirectly, elephants could reinforce this difference by engaging females more in tissue repair after browsing.

Variation in Wood Physical Properties of Eucalyptus Growing in Seedling Seed Orchard in Pleihari, South Kalimantan

This study shows an effort to obtain the best performance of Eucalyptus pellita trees, which was conducted by examining the physical properties of wood of 116 months age Eucalyptus pellita trees. The trees of various families used in this study were all grown in Seedling Seed Orchard (SSO), Pleihari. A total of 10 families with 3 individual trees for each family as replication were randomly selected for the whole SSO. Selected sample trees were felled, cut and divided into three different parts (bottom, middle and top) of the stem. Each stem part was then cut into wood samples running from pith to bark portion for the examination of its physical properties according to British Standard BS 373-1957. The collected data on those properties were analyzed by using a completely randomized design (CRD). The results showed that there were significant differences in wood density and fiber length among different height, and among wood sections from pith to bark in individual trees as well as among families. Wood density showed high family heritability (0.708) and genetic correlation between wood density and fiber length were significantly different (r = 0.543).

Variation and Correlations Among Stem Growth and Wood Traits of Calycophyllum spruceanum Benth. from the Peruvian Amazon

Abstract Calycophyllum spruceanum Benth. is an important tree for timber and energy in the western Amazon, with expanding national and international markets for its wood. There is relatively little information, however, about geographic variation in tree growth and wood properties, and correlations among these traits. The first provenance trial was established with farming communities in the Peruvian Amazon. Seven provenances, sampled from regions near the equator, were tested in three planting zones located in one watershed. Variation and correlations were investigated in stem growth at 30 and 42 months, wood density (in the lower and upper parts of the stem) and mean heat content of stem wood at 32 months. Stem height varied significantly among provenances and planting zones, but zones accounted for much more variation than provenances. Stem wood traits did not vary significantly among provenances. Wood density was greater in the lower than in the upper stem. Wood density in the upper stem and the difference in density between the lower and upper stem varied significantly among planting zones: density in the upper stem was lowest, and the difference in density between the lower and upper stem was largest in the zone where trees grew most rapidly. Phenotypic correlations between stem growth and wood density differed in sign among planting zones, suggesting that selecting fastgrowing trees could indirectly reduce wood density in environments where trees grow slowly, and increase the difference in wood density between the lower and upper stem in environments where trees grow very rapidly. Correlations between stem growth and wood heat content were stable across zones, and indicated that larger trees tended to have wood with higher heat content. Stem-wood heat content varied with provenance latitude/ longitude in the sample region, but none of the other traits varied clinally. Results indicate that there is potential to select faster-growing provenances at an early age, but this could affect wood density in certain environments.

Differences in wood density and growth of fertilized and nonfertilized loblolly pine associated with a mutant gene, cad-n1

A rare mutant allele (cad-n1) of the cad gene in loblolly pine (Pinus taeda L.) causes a deficiency in the production of cinnamyl alcohol dehydrogenase (CAD). Effects associated with this allele were examined by comparing wood density and growth traits of cad-n1 heterozygous trees with those of wild-type trees in a 10-year-old open-pollinated family trial growing under two levels of fertilization in Scotland County, North Carolina. In all, 200 trees were sampled, with 100 trees for each fertilizer treatment. Wood density measurements were collected from wood cores at breast height using X-ray densitometry. We found that the substitution of a cad-n1 for a wild-type allele (Cad) was associated with a significant effect on wood density. The cad-n1 heterozygotes had a significantly higher wood density (+2.6%) compared with wild-type trees. The higher density was apparently due to the higher percentage of latewood in the heterozygotes. The fertilization effect was highly significant for both growth and wood density traits. This study indicates that the cad-n1 allele could be a valuable gene to the pulp and paper industry for the purpose of enhancing pulp yields by increasing wood density.

Wood density of young-growth western hemlock: relation to ring age, radial growth, stand density, and site quality

Breast-high stem sections were sampled from 56 western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees growing in 15 plots representing a wide range of tree and site conditions in northwestern Oregon. Growth and wood density traits of individual rings were measured via X-ray densitometry, and relationships of ring density and its components to age and growth rate were analyzed. Ring density was highest (0.49 g/cm3) near the pith, declined to 0.40 g/cm3 at age 10, remained stable to about age 25, and then increased gradually and remained between 0.43 and 0.44 g/cm3 from age 38 to 45 and beyond. A negative influence of rapid growth on whole ring density was greatest at young ages and diminished with time, becoming nonsignificant beyond age 30. Earlywood density, latewood density, and latewood proportion were all negatively related to ring width at young ages, but by age 21-25, latewood proportion was the only component of ring density that remained significantly diminished by increased growth rate. Residual differences in wood density (after age and growth rate were considered) did not appear to be related to either stand density or site class. Overall, young-growth hemlock trees are relatively uniform in wood density and likely to be more so if grown in intensively managed stands.

X-ray microdensitometry analysis of vibration-welded wood

X-ray microdensitometry tests on vibration-welded hardwoods (beech and oak) and a softwood (spruce) showed that adhesion of wood surfaces by vibration welding was accompanied by a considerable increase in the density of the wood at the bonded interface. This is due to the loss of the intercellular structure of the wood at the interface and considerable decrease of empty spaces in its cellular structure. The sharper and more regular is the increase in density at the interface the better is the mechanical performance of the joint. This was ascribed to the marked difference in wood density between earlywood and latewood. This intra-ring wood heterogeneity is a limiting factor for reaching high local compression rates during the welding process. In the case of spruce wood it causes cells collapse and, consequently, poorer bonding. Absolute and relative density maps of well-bonded, poorly-bonded and unbonded joints are reported. X-ray microdensitometry proved to be a valuable technique to determine the extent of wood welding.

THE AGE AND DENSITY OF ANCIENT AND MODERN OAK WOOD IN STREAMS AND SEDIMENTS

Large wood of oak trees (Quercus spp.) has resided in the streams and sediments of north Missouri, USA for many thousands of years. This wood affords the opportunity to compare a chronosequence of differences in wood density over a very long period. We analyzed the relationship between the age (residence time) and density of heartwood from oak boles using tree-ring and 14C dating methods and discuss their implications. The residence time of large oak wood (> 25 cm diameter) sampled in the streams and sediments ranged from less than 14 years to more than 12,320 years. The oak wood ranged in density from 0.82 g cm-3 for a tree that had recently fallen into the stream to 0.14 g cm-3 for ancient oak wood. Two regression equations relate age (residence time) and density of oak wood and explain 88 percent of the variance in the dependent variables. Equation 1, heartwood density = age, can be used for studies in carbon cycling, wood as invertebrate habitat, or other questions related to the density and ecology of wood in streams such as wood retention and export. Equation 2, age = heartwood density, can be used for estimating when oak wood was formed on a very coarse scale over many thousands of years.

Clonal variation in nutrient content in woody biomass of hybrid aspen (Populus tremula L. x P. tremuloides Michx.)

Differences in the nutrient concentrations and nutrient amounts of stems and branches amongst clones of hybrid aspen (Populus tremula L. x P. tremuloides Michx.) were investigated. Seven clones with superior and seven with medium growth rates were selected from a test of 119 clones in southern Sweden. Four trees per clone were randomly identified and harvested in dormant conditions. Sample discs from the stems and branches were collected and analysed for N, K, P, Ca, Mg, and S concentrations, as well as wood density. The analyses revealed significant genetic differences in wood density, K, P, and Mg concentrations in the stems. There were weak (non-significant) and negative genetic correlations between stem volume and concentrations of all the nutrients, except potassium, suggesting that nutrient-efficient clones could be selected without significantly sacrificing genetic gain for growth. In the branches K, Ca, and Mg concentrations differed significantly among clones. After selecting more nutrient efficient clones, the potential savings of nutrients compared with current hybrid aspen material was estimated to be around 5%, which seems fairly low, at least in a short-term perspective. However, the use of clones with different nutrient storage strategies may be regarded as a possible way in the long run to save nutrients in hybrid aspen ecosystems, or of removing them when sludge is applied.

Relationships between surface growth strain and some tree, wood and sawn timber characteristics ofEucalyptus cloeziana

SYMMARY To assess the utility of the CIRAD-Fort% growth strain gauge for estimating stein growth stress, the relationship of longitudinal growth strain (LGS) with log-end splitting, sawn timber distortion and other tree and wood properties was studied in 23 ten-year-old Eucalyptus cloeziana trees. The CIRAD-Foret growth strain gauge appears to be useful as a means of predicting sawn timber distortion in young E. cloeziana trees. LGS correlated well with bow and spring and accounted for 50 and 30% of the respective total variation. The relationships of LGS with log end splitting, wood density, tree diameter and height were weak. However, distinct differences in wood density and sawtimber distortion were observed between trees with low and high strain. Trees with high growth strain were generally smaller with wood of significantly higher basic density and bow. Sampling position around the stem was not important and LGS increased with tree height.

Variation in Wood Density and Tracheid Length inPinus patulagrown in Zimbabwe

SYNOPSIS Within-tree variation of wood density was studied for 14-and 25-year-old Pinus patula Schiede & Deppe trees grown at two plantation sites in Zimbabwe. Three trees of each age per site were selected and disc samples obtained at six relative height levels. A diametric strip was prepared from each sample disc and cut into two sample strips. Conditioned density was measured along the first strip using an x-ray densitometer. The second strip was pulped while clamped between perforated plates and tracheid length measured with the Kajaani FS 200 fibre analyser. At both sites, 25-year-old trees had higher density and longer tracheids than 14-year-old trees (0,557 and 0,544 g/cm3 as against 0,476 and 0,492 g/cm3; 3,55 and 3,84 mm against 3,48 mm and 3,07 mm), There were minimal differences in wood density between sites, but tracheid length showed substantial differences between sites. Wood density and tracheid length increased with growth ring age, with a rapid increase occurring in the first 14 years for...

Infrared Studies of Wood Weathering. Part II: Hardwoods

Four different hardwoods—yellow poplar, quaking aspen, white oak, and hard maple—have been subjected to a range of artificial weathering conditions, and their surfaces monitored with the use of diffuse reflectance infrared spectroscopy. The first two species show a weathering pattern rather similar to that of softwoods, whereas the latter two are more resistant to the effects of light and water. The differences in wood density are thought to be significant in the different behavior of the woods towards weathering, in addition to any contributing effects that might be caused by a variation in the overall chemical composition. After 2400 hours of full artificial weathering, all traces of lignin seem to have been removed from the surfaces of all four woods.