Variation In Wood Specific Gravity Research Articles

An application of mixed-effects model to evaluate the role of age and size on radial variation in wood specific gravity in teak (Tectona grandis)

To test whether radial variation of wood specific gravity (WSG) is controlled by tree age or tree size in teak (Tectona grandis L.f) plantation trees, opposing different-length pith-to-bark strips which represents the differential lateral growth rate was compared using mixed-effects model which considers the heterogeneity of variances and dependency in the data to gain insight into the stochastic processes that govern the wood formation process. Various models were tested in devising an appropriate radial WSG model. Models that accounted for serial correlation in WSG data performed better than the simple structure that assumes zero correlation between measurements. The autoregressive plus random tree effect structure performed better in describing the radial variation pattern. The variability of the data related to random fluctuations during tree development and the wood formation process is modeled by the autoregressive parameter revealing the intrinsic complexity of wood formation. Since they cannot be attributed to observed factors, models should consider temporal or serial correlations when assessing wood quality. The results revealed that tree age is a decisive factor in controlling the WSG of wood, while tree size is statistically less important. Furthermore, the core wood production period varies with the growth rate. It is shown that the core wood area decreased with slow growth. Findings presented here appear to provide the first demonstration of radial variation in WSG with respect to growth rate and age for planted teak growing in Ghana.

Space-time analysis of the longitudinal variation in wood specific gravity of teak and its effect on tree growth and development

The space-time structure of a teak wood specific gravity (SG) dataset was analyzed using a mixed-effects model. Spatial correlation increased in space, a phenomenon attributable to the maturation of apical meristems, while the temporal correlation of vascular meristems decreased over time. The decay of temporal correlation over time was attributed to the diminishing crown effect on the later formed wood further away from the pith, morphogen gradient, and probably changing microenvironmental conditions. The Kronecker product was used to collect spatiotemporal data on the intricate dynamic process of the evolution of the apical and lateral meristems. The results showed that height and relative radial distance (RRD) (i.e., the flow of time with wood formation) were statistically significant factors, with their interaction showing no significance. The results confirm the usefulness of using the space-time approach to elucidate the interaction between the apical and lateral meristems, two major inherent biological systems that control tree growth and wood formation dynamics. To understand the origins of patterns that vary both temporally and spatially in the tree, future work should describe the variation of SG within the tree due to increasing height (space) and diameter (age) as a matrix; then the correlation function can be modelled.

Size‐dependent intraspecific variation in wood traits has little impact on aboveground carbon estimates in a tropical forest landscape

Abstract There is increasing evidence that intraspecific trait variation plays a role in governing rates of ecosystem functioning. While wood traits such as wood specific gravity (WSG) and wood carbon concentration (WCC) are key drivers of forest aboveground carbon (AGC) stocks, the sources of intraspecific variation in these wood traits and the consequences of this variation on AGC are poorly known, especially in the tropics. Here, we investigated intraspecific variation in wood specific gravity (WSG) and wood carbon concentration (WCC) from 556 individual trees belonging to 15 species that well characterize different successional stages of seasonal evergreen forests in Southeast Asia. Specifically, we tested the contribution of individual or species characteristics (tree size, growth rate and regeneration guilds) and local environmental conditions (topographic wetness index and successional stages) to intraspecific variation in WSG and WCC, and assessed the consequences of intraspecific variation in these wood traits on AGC estimates in 14 permanent forest plots established along a successional gradient in Khao Yai National park, Thailand. We found that tree size was the main driver of intraspecific variation in WSG and WCC as tree sizes increased from 10–100 cm in diameter, WSG increased by 7.3%, while WCC increased by 2.4% in heartwood, 1.6% and 2.7% in sapwood without and with volatile carbon included. There was no effect of the topographic wetness and other local environment condition in wood traits led to a slight overestimation of AGC in young secondary forests (+0.09% to +1.29%) and a small underestimation in older forests (−0.86% to −2.87%), but overall AGC estimates (13 of 14 forest plots) remained within error margins (the 95% interval). Our study provides evidence that tree size variation translates into intraspecific variability in wood traits, whereas local environmental conditions related to topography successional stages had no effect on wood trait variability. While size‐dependent variation in WSG and WCC have largely been undocumented and thus ignored in forest carbon assessment approaches, we highlight that it has a limited impact on AGC estimates, indicating that it does not invalidate current forest carbon stock estimation approaches. Read the free Plain Language Summary for this article on the Journal blog.

Ignoring variation in wood density drives substantial bias in biomass estimates across spatial scales

Rapid development of remote sensing and Light Detection and Ranging (LiDAR) technology has refined estimates of tree architecture and extrapolation of biomass across large spatial scales. Yet, current biomass maps show significant discrepancies and mismatch to independent ground data. A potential obstacle to accurate biomass estimation is the loss of information on wood density, which can vary at local and regional scales, in the extrapolation process. Here we investigate if variation in wood specific gravity (WSG) substantially impacts the distribution of above-ground biomass (AGB) across a range of scales from local plots to large regions. We collected wood cores and measured tree volume in 341 forest sites across large altitudinal and climatic gradients in Colombia. At all spatial scales, variation in WSG was substantial compared to variation in volume. Imputing study-wide average values of WSG induced regional biases in AGB estimates of almost 30%, consequently undervaluing the difference between forest areas of low and high average wood density. Further, neither stem size nor climate usefully predicted WSG when accounting for spatial dependencies among our sampling plots. These results suggest that remote sensing- and LiDAR-based projections to biomass estimates can be considerably improved by explicitly accounting for spatial variation in WSG, necessitating further research on the spatial distribution of WSG and potential environmental predictors to advance efficient and accurate large-scale mapping of biomass.

How forest structure varies with elevation in old growth and secondary forest in Costa Rica

Clarifying how forests vary with elevation can inform our understanding of forests and their responses to climate. Despite the prevalence of secondary forests (defined as regrowth after disturbance), few studies have examined how their structure and recovery vary with elevation. Here, in apparently the first study of its kind, we explored how basal area, stem density and community wood specific gravity of stems ≥ 10 cm diameter vary along an old growth and a 25–30 years old secondary forest transect, each spanning over 2000 m of elevation in Costa Rica. The old growth transect comprises 29 plots of 0.25 ha from 440 to 2900 m.asl. and the secondary 28 plots of 0.1 ha and 10 plots of 0.25 ha from 600 to 2750 m.asl. We characterized how stand characteristics vary with elevation using linear and generaled additive models. To our surprise basal area increased with elevation not only in the old growth (from 24 to 56 m2/ha) but also in the secondary forest (11 to 59 m2/ha). This increase reflected the greater density of larger trees (≥40 cm diameter) at higher elevations. Basal area decreased with inferred water availability (global aridity index) in the secondary, but not the old growth forest. Surprisingly, wood specific gravity revealed no clear pattern with elevation in either transect though within stand variation decreased with elevation in both. In both forests, basal area is positively correlated with mean wood specific gravity, being significantly greater in stands with less variation in wood specific gravity. We interpret these patterns as resulting from reduced mortality of larger trees at higher versus lower elevations in both old-growth and secondary forest. Our results imply that planting trees to enhance recovery would be more beneficial in lowland than in high elevation forests.

Radial variation in wood specific gravity of tropical tree species differing in growth-mortality strategies.

• Wood specific gravity (WSG) mediates an interspecific trade-off between growth and mortality and is a key measure for estimating carbon stocks. Most studies use species mean values to represent WSG, despite variation at different levels of biological organization. We examined sources of variation in WSG across four nested scales (segments within cores, cores within trees, trees within species, and species), compared the pattern of radial variation in WSG among species differing in growth strategies, and investigated the effect of WSG radial variation on aboveground biomass estimates.• We took two perpendicular cores from six individuals each of 20 tropical tree species representing a broad range of mean WSGs and growth-mortality strategies in a lowland tropical moist forest in Panama. Cores were divided into 1-cm segments, and WSG was determined for each segment.• The bulk of the total variance in WSG was dominated by interspecies variation (88%), whereas variation due to measurement error, segments within cores, and cores within trees (8%) was minimal. Radial variation in WSG, defined as change in WSG with increasing distance from the pith, was significant in 17 of the 20 species and included significant monotonic increases in 6 species and nonmonotonic patterns in 11 species. Radial variation in WSG resulted in a small but significant bias in aboveground biomass estimates.• Radial variation in WSG is related to a species' growth strategy and, though minimal compared with interspecific variation in WSG, can cause a downward bias when not incorporated into aboveground biomass estimates.

Wood specific gravity and anatomy of branches and roots in 113 Amazonian rainforest tree species across environmental gradients

Wood specific gravity (WSG) is a strong predictor of tree performance across environmental gradients. Yet it remains unclear how anatomical elements linked to different wood functions contribute to variation in WSG in branches and roots across tropical forests. We examined WSG and wood anatomy in white sand, clay terra firme and seasonally flooded forests in French Guiana, spanning broad environmental gradients found throughout Amazonia. We measured 15 traits relating to branches and small woody roots in 113 species representing the 15 most abundant species in each habitat and representative species from seven monophyletic lineages occurring in all habitats. Fiber traits appear to be major determinants of WSG, independent of vessel traits, in branches and roots. Fiber traits and branch and root WSG increased from seasonally flooded species to clay terra firme species and lastly to white sand species. Branch and root wood traits were strongly phylogenetically constrained. Lineages differed in wood design, but exhibited similar variation in wood structure across habitats. We conclude that tropical trees can invest differently in support and transport to respond to environmental conditions. Wind disturbance and drought stress represent significant filters driving tree distribution of Amazonian forests; hence we suggest that biophysical explanations should receive more attention.

Structural relationships between form factor, wood density, and biomass in African savanna woodlands

Variation in tree biomass among African savanna species of equal size is driven by a wide inter-specific variation in wood specific gravity. Tree form and taper is a fundamental component of tree structure and has been used for over a century in forestry to estimate timber yields and in ecological theories of scaling laws. Here, we investigate variation in form factor in the context of biomass in African savannas. Biomass is a fundamental metric of vegetation state, yet in African savannas it remains unclear whether variation in form factor F (taper) or wood specific gravity (G) is a more dominant driver of biomass differences between tree species of equal stem diameter and height. Improving our knowledge of vertical mass distribution in savanna trees provides insight into differences in life strategies, such as tradeoffs between production, disturbance avoidance, and water storage. Here, we destructively harvested 782 stems in a savanna woodland near Kruger National Park, South Africa, and measured whole tree wet mass, wood specific gravity, water content, and form factor. We found that three of four dominant species can vary in mass by over twofold, yet inter-specific variation in taper was low and taper did not vary significantly between common species (P > 0.05) (species-mean form factors ranged from F = 0.57 to 0.77, where cone F = $$0.\bar{3}$$ , quadratic paraboloid F = 0.5, cylinder F = 1.0). Comparison of a general biomass allometry model to species-specific models supported the conclusion that the large difference in biomass between species of the same size was explained almost entirely (R 2 = 0.97) by including species-mean G with D and H in a general allometric equation, where F was constant. Our results suggest that inter-specific variation in wood density, not form factor, is the primary driver of biomass differences between species of the same size. We also determined that a simple analytical volume-filling model accurately relates wood specific gravity of these species to their water and gas content (R 2 = 0.68). These results indicate which species use a wide spectrum of water storage strategies in savanna woodlands, adhering to a trade-off between the benefits of denser wood or increased water storage.

Radial Gradients in Wood Specific Gravity, Water and Gas Content in Trees of a Mexican Tropical Rain Forest

AbstractCell walls, water, and gas that have mechanical and physiological functions in wood, and wood specific gravity (WSG) is related to demographic traits. To understand variation in wood structure and function, we analyzed radial changes in WSG, in the gas and the water fractions from trees growing in four different habitats in a southern Mexican rain forest. Mean WSG was 0.55 ± 0.16, slightly lower than reported for other tropical forests. In 27 species, WSG decreased and in two species, it increased from pith to bark with a strong (r2 = 0.65) negative correlation between WSG in the center of the tree and the radial WSG gradient. Habitat had some effect on mean WSG and trees growing on karst had significantly higher WSG than the same species growing on alluvial soil. The cell wall, water, and gas fractions accounted for 35 percent (range: 16–50), 42 percent (28–65), and 23 percent (2–56), respectively, of wood volume, with a negative correlation between the gas and the cell wall and between the gas and the water fractions, but not between the cell wall and water fractions. Radially increasing WSG is advantageous for pioneer trees with fast initial growth. We found that the water displacement method may result in biased WSG estimates. To increase the accuracy of WSG data, we suggest to measure sample volume geometrically using a constant diameter (that of the borer tip), to include radial variation in WSG, and to consider for possible site effects on species‐specific WSG.

Age versus size determination of radial variation in wood specific gravity: lessons from eccentrics

Radial increases in wood specific gravity have been shown to characterize early successional trees from tropical forests. Here, we develop and apply a novel method to test whether radial increases are determined by tree age or tree size. The method compares the slopes of specific gravity changes across a short radius and a long radius of trees with eccentric trunks. If radial changes are determined by size, then the slope of the change should be the same on both radii. If radial changes are determined by age, then the slope should be greater on the short radius. For 30 trees from 12 species with eccentricity of at least 4%, the ratio of the slopes of the linear regressions of specific gravity on radial distance (short radius slope/long radius slope) was regressed on the ratio of radii lengths (long radius/short radius). The regression was highly significant, and the faster increase in specific gravity on the short radius was sufficient to compensate for the difference in radius lengths, so the specific gravity of wood along the short radius was equal to the specific gravity on the long radius at any given proportional distance on the radius. Therefore, trees that are producing xylem faster on one radius than another produce wood of comparable specific gravity on both radii at the same time, so radial increases in specific gravity are dependent on tree age, not tree size.

Modeling the longitudinal variation in wood specific gravity of planted loblolly pine (Pinus taeda) in the United States

Loblolly pine (Pinus taeda L.) is a major plantation species grown in the southern United States, producing wood having a multitude of uses including pulp and lumber production. Specific gravity (SG) is an important property used to measure the quality of wood produced, and it varies regionally and within the tree with height and radius. SG at different height levels was measured from 407 trees representing 135 plantations across the natural range of loblolly pine. A three-segment quadratic model and a semiparametric model were proposed to explain the vertical and regional variations in SG. Both models were in agreement that a stem can be divided into three segments based on the vertical variation in SG. Based on the fitted models, the mean trend in SG of trees from the southern Atlantic Coastal Plain and Gulf Coastal Plain was observed to be higher than in other physiographical regions (Upper Coastal Plain, Hilly Coastal Plain, northern Atlantic Coastal Plain, and Piedmont). Maps showing the regional variation in disk SG at a specified height were also developed. Maps indicated that the stands in the southern Atlantic Coastal Plain and Gulf Coastal Plain have the highest SG at a given height level.

Genetic variation in wood specific gravity among half-sib families of chir pine (Pinus roxburghii sargent)

Chir pine (Pinus roxburghii) is an important tree species that grows all along the Himalayas. Wood specific gravity of chir pine before and after removal of extractives from wood increment cores was assessed from a 22-years-old progeny test in Himachal Pradesh, India. These values averaged 0.433 and 0.425, respectively. A large amount of genetic variation among the 58 half-sib families was found as indicated by range of values, additive coefficient of variation, variance estimates and narrow-sense heritability values for these traits. Moisture and extractive content averaged 86.259% of oven-dry weight and 2.003% of extractive-free oven-dry weight, respectively. Wood extractive content was highly variable and the family differences were highly heritable (hf2 = 0.5831). There was wide variability in moisture content, but a large portion of it was due to environmental or non-additive component of genetic variation. Heritability on family mean basis was found to be lower than that on individual tree basis for each trait. Estimated gain in specific gravity resulting from 30 to 50% family selection ranged from 0.0080 to 0.0127. Growth data and specific gravity were not significantly correlated implying that selection for higher growth rate would not necessarily result in reduction in wood specific gravity in chir pine.

Regional variation in wood specific gravity of planted loblolly pine in the United States

Loblolly pine ( Pinus taeda L.) is the most important plantation species in the southeastern United States and specific gravity (SG) is its most important wood quality trait. Analysis of annual ring SG of breast height (1.37 m) increment cores from 3957 trees representing 147 plantations across the species natural range showed that ring SG increases with increasing age and varies significantly among physiographic regions. The South Atlantic and Gulf regions had the highest ring SGs, while the Hilly and Piedmont regions had the lowest. Based on ring SG, the juvenile period averages 4.3 years, followed by 8.6 years of transition wood, with mature wood produced by year 13. Whole-core mean SG was significantly higher in the South Atlantic (0.486) compared with the other regions (mean = 0.455), which were not statistically different from each other. Trees from the South Atlantic have significantly higher whole-core SG because they contain significantly more latewood (40.1%) compared with trees growing in other regions (33.8%). Maps indicate that stands in the South Atlantic and Gulf regions have the highest SG at a given age. Stands growing on the northern and western fringe of the natural range of loblolly pine have the lowest whole-core SG.

Regional scale variation in forest structure and biomass in the Yucatan Peninsula, Mexico: Effects of forest disturbance

Aboveground biomass is a key variable in understanding the role of tropical forests in the global carbon cycle. The forests of the Yucatan Peninsula form part of the largest remaining tract of Mesoamerican forests, where the predominant land use is still slash-and-burn agriculture. Previous estimates of aboveground live phytomass of late-successional forests in this region vary almost twofold, but are derived from relatively few forest plots. We estimate aboveground forest biomass using data from 243 inventoried forest plots (totalling 58.5 ha), ranging across a disturbance gradient from nearly intact to severely degraded forests. We assess the effects of environmental and disturbance variables on forest basal area, stand-level wood specific gravity and aboveground biomass. Major differences in basal area and aboveground biomass were explained by levels of human disturbance (clear-cutting, logging, and fire disturbance), whereas edaphic factors played only a minor role. Total mean phytomass density estimates ranged from 28.8 ± 3.8 mg ha −1 in plots aged 10–15 years to 191.9 ± 9.5 mg ha −1 in undisturbed old-growth forest plots (>50 years). Severe logging and fire disturbance reduced AGB in late-successional plots (30–50 years) by 36% and 37%, respectively. Stand-level wood specific gravity increased with succession, due to an increase in the proportion of total basal area contributed by high wood density genera. Logging intensity had a small additional effect on stand-level wood specific gravity. Incorporating stand-level wood specific gravity into the algorithm explained only an additional 4% of the variation in estimates of aboveground biomass, which was largely determined by basal area. However, ignoring plot-level variation in wood specific gravity resulted in overestimates of 19% in plots aged 10–15 years. Our aboveground biomass estimates were highly comparable with previous studies using the same allometric equations, and fell within the highest range of estimates reported for tropical dry forests. Forest of this region still retains a significant carbon stock, but rates of biomass recovery (2.8 ± 0.2S.E. mg ha −1 year −1) were low compared to other neotropical forests.

Genetic Variation in Wood Specific Gravity in Poplar (Populus deltoides Bartr.) from two locations in Punjab

Specific gravity of wood was measured of samples collected at breast height of Poplars planted at two locations of Punjab viz. central plain region (Ludhiana) and semi-arid region (Bathinda). Significant differences among clones were noticed at both the locations. Specific gravity ranged from 0.403 to 0.475 in central plain region and from 0.356 to 0.436 in semi-arid region. The genotype x environment interaction was also significant. The genotypic and phenotypic coefficients of variation were low (2.88 to 5.88%). The heritability was moderate (40.82%) in central plain region and high (64.82%) in semi-arid region. Selection of promising clones for end use of wood on basis of specific gravity has been discussed.

Interspecific and Inter‐site Variation in Wood Specific Gravity of Tropical Trees

ABSTRACTVariation in climate and soils results in inter‐site differences in the assemblages of tree life history strategies within a community, which has important implications for ecosystem structure and dynamics. I investigated interspecific and inter‐site variation in wood specific gravity–an easily measured indicator of tree life history strategy–in four Neotropical forests and analyzed its correlates. Mean wood specific gravity (oven‐dry weight divided by fresh volume, sometimes also referred to as wood density in the literature) differed significantly among sites, varying inversely with soil fertility and independently of rainfall, seasonality, and temperature. Mean wood specific gravity values were much higher at Kilometer 41, Manaus, Brazil, where soils are extremely poor, than at Cocha Cashu, Peru, Barro Colorado Island, Panama, or La Selva, Costa Rica, where soils are better and mortality rates of trees are higher. Within sites, wood specific gravity varied widely among species. On Barro Colorado Island, among‐species variation was significantly, albeit weakly, negatively correlated with sapling and tree mortality and relative growth rates. Altogether, the results suggest that the distribution of tree life history strategies in a community varies substantially among sites, with important consequences for community and ecosystem properties such as aboveground carbon stores.RESUMENLa variación climática y edáfica da lugar a diferencias entre sitios con respecto a los ensambles de las estrategias de historia de vida de los árboles de una comunidad, lo cual tiene consecuencias importantes para la estructura y la dinámica del ecosistema. Investigué la variación interespecífica y espacial en la gravedad específica de la Madera–un indicador de fácil medición de la estrategia de historia de vida de los árboles–en cuatro bosques neotropicales y analizé sus factores asociados. La gravedad especifica media de la madera (el peso seco dividido por el volumen fresco, frecuentemente llamado “densidad de la madera” en la literatura ecológica) fue significativamente diferente entre sitios, variando inversamente con la fertilidad del suelo, e independientemence de la precipitación, la estacionalidad, y la temperatura. La gravedad especifica media de la madera fue mucho más alta en Kilómetro 41, Manaus, Brasil, donde los suelos son extremadamente pobres, en comparación con Cocha Cashu, Perú, Barro Colorado, Panamá, o La Selva, Costa Rica, donde los suelos son mejores y las tasas de mortalidad de los árboles son más altas. Dentro de los sitios, la gravedad especifica de la madera varió extensamente entre especies. En Barro Colorado, la variación entre especies estuvo correlacionada negativamente, aunque sólo débilmente, con las tasas de mortalidad y de crecimiento relativo de los árboles juveniles y adultos. En conjunto, los resultados sugieren que la distribución de las estrategias de historia de vida de los árboles en una comunidad varía sustancialmente entre sitios, con consecuencias importantes para características comunitarias y del ecosistema tales como las reservas de carbono.

Interspecific and Inter-site Variation in Wood Specific Gravity of Tropical Trees1

Interspecific and Inter-site Variation in Wood Specific Gravity of Tropical Trees1

Radial Variation in Wood Specific Gravity, Fibre Length and Vessel Area for Two Central American Hardwoods: Hyeronima Alchorneoides and Vochysia Guatemalensis: Natural and Plantation-Grown Trees

Natural-grown and young (5.5 year old) plantation-grown trees were sampled for two Central American hardwood species: Hyeronima alchorneoides and Vochysia guatemalensis in the Atlantic lowlands of Costa Rica. Increment cores extracted at a height of 1.3 m from trees were divided into 1cm segments from pith to bark. Basic specific gravity was calculated for each segment. Using the same cores, fibre length was measured from macerations for five natural and plantation-grown trees of each species. Number of vessels/mm2 and vessel tangential diameter were measured from segment cross sections for five natural-grown trees of each species.

Gradients in Wood Specific Gravity of Trees

WILLIAMSON, G. B. (Dept. Botany, Louisiana St. Univ., Baton Rouge, LA 70803). Bull. Torrey Bot. Club. 111: 51-55. 1984.-Wood specific gravity, an index of structural support, is more variable among species in Trinidad and in Costa Rica than in Indiana. Therefore, structural support may be one dimension of increased niche diversification of tropical trees. Furthermore, the high variance in specific gravity among species in the tropical areas is present within individual forest stands. The Indiana stands lack the low specific gravity ( 0.70) woods found in the tropical stands. With increasing elevation in both Trinidad and in Costa Rica there is a two-step transition where low specific ( 0.70) woods disappear. Montane forests in Trinidad and Costa Rica have specific gravity distributions similar to those of Indiana forests. There are no apparent differences in specific gravity distributions among forests along wet-dry gradients in Trinidad, Costa Rica or Indiana. Variation in wood specific gravity and related strength properties parallels variation in species richness along elevational and latitudinal gradients but not along wet-dry gradients.