Measured Wood Density Research Articles

Non-Destructive Wood Analysis Dataset: Comparing X-Ray and Terahertz Imaging Techniques

Wood density measurement plays a crucial role in assessing wood quality and predicting its mechanical performance. This dataset was collected to compare the accuracy and reliability of two non-destructive techniques, X-rays and terahertz waves, for measuring wood density. While X-rays have been commonly used in the industry due to their effectiveness, they pose health risks due to ionizing radiation. Terahertz waves, on the other hand, are non-ionizing and offer high spatial resolution. This article presents a database of wood samples measurements obtained using both techniques, on the same 110 samples with a fine location of the measuring points, on a wide range of wood species (tropical and temperate ones) and densities, from 111 kg·m−3 to 1086 kg·m−3. The database includes X-ray and terahertz scans, sample dimensions, moisture content, and color photographs.

Linking seedling wood anatomical trade-offs with drought and seedling growth and survival in tropical dry forests.

Wood anatomy plays a key role in plants' ability to persist under drought and should therefore predict demography. Plants balance their resource allocation among wood cell types responsible for different functions. However, it remains unclear how these anatomical trade-offs vary with water availability, and the extent to which they influence demographic rates. We investigated how wood anatomical trade-offs were related to drought and demographic rates, for seedling communities in four tropical dry forests differing in their aridity indexes (AIs). We measured wood density, as well as vessel, fiber and parenchyma traits of 65 species, and we monitored growth and survival for a 1-yr period. Two axes defined wood anatomical structure: a fiber-parenchyma axis and a vessel-wood density axis. Seedlings in drier sites had larger fiber but lower parenchyma fractions, while in less dry forests, seedlings had the opposite allocation pattern. The fiber-parenchyma trade-off was unrelated to growth but was positively related to survival, and this later relationship was mediated by the AI. These findings expand our knowledge about the wood anatomical trade-offs that mediate responses to drought conditions and influence demographic rates, in the seedling layer. This information is needed to anticipate future responses of forests to changing drought conditions.

Influence of reforestation tree species on decomposition of larch stumps and coarse roots: role of wood microbial communities and soil properties

Abstract Stumps and coarse roots are the most important coarse woody debris component in managed forests. However, their decomposition is still poorly understood, especially the influence of the characteristics of the microbial communities on wood decomposition. In this study, we investigated decaying larch (Larix olgensis Henry) stumps and coarse roots in reforestations of birch (Betula pendula Roth.), ash (Fraxinus mandshurica Rupr.), pine (Pinus sylvestris var. Mongolica), and larch in the northeast of China. We measured wood density loss, cellulose, and lignin concentrations, analyzed microbial community composition, and assessed the physical and chemical properties of woodland soils. Our findings reveal that larch stumps and coarse roots experienced the most rapid decomposition within birch reforestation areas, exhibiting significant density loss in stumps (33.84%) and coarse roots (43.68%). Bacterial diversity on larch stumps and coarse roots was highest in birch reforestation, with dominant phyla including Proteobacteria, Actinobacteriota, and Bacteroidota. Fungal diversity was also highest in birch reforestation, with Ascomycota as the dominant phylum in larch stumps and coarse roots. Furthermore, a mantel test analysis indicated that soil pH and temperature were significant factors in wood decomposition which affected microbial communities. This suggests that the choice of the reforestation tree species affects the decomposition of stumps and coarse roots by affecting soil properties and wood microbial communities. Understanding this process is vital for refining carbon balance evaluations, and enhancing ecosystem-level carbon modeling.

Research on the Wood Density Measurement in Standing Trees through the Micro Drilling Resistance Method

To achieve a micro-destructive and rapid measurement of the wood density of standing trees, this study investigated the possibility of the unified modeling of multiple tree species, the reliability of the micro drilling resistance method for measuring wood density, the relationship between drilling needle resistance and wood density, and whether moisture content has a significant impact on the model. First, 231 tree cores and drill resistance data were sampled from Pinus massoniana, Cunninghamia lanceolate, and Cryptomeria fortunei. The basic density and moisture content of each core were measured, and the average value of each resistance data record was calculated. Second, the average drill resistance, the natural logarithm of average drill resistance, and absolute moisture content were used as independent variables, while the basic wood density was used as the dependent variable. Third, the total model of the three tree species and sub-model for each tree species were established through a stepwise regression method. Finally, the accuracy of each model was compared and analyzed with that of using the average basic density of each tree species as an estimated density. The estimated accuracy of the total model, sub model, and average wood density modeling data were 90.070%, 93.865%, and 92.195%, respectively. The results revealed that the estimation accuracy of the sub-model was 1.670 percentage points higher than that of the average wood density modeling data, while the estimation accuracy of the total model was 2.125 percentage points lower than that of the average wood density modeling data. Additionally, except for Cryptomeria fortunei, the natural logarithm of drill resistance significantly influenced the wood density model at a significance level of 0.05. Moreover, moisture content significantly affected the total model and sub-models of Pinus massoniana at a significance level of 0.05. The results indicated the feasibility of using the micro-drilling resistance method to measure the wood density of standing trees. Moreover, the relationship between wood density and drill resistance did not follow a linear pattern, and moisture content slightly influenced the drill needle resistance. Furthermore, the establishment of a mathematical model for each tree species was deemed essential. This study provides valuable guidance for measuring the wood density of standing trees through the micro-drilling resistance method.

Widespread stem snapping but limited mortality caused by a category 5 hurricane on the Caribbean Island of Dominica

Hurricanes are projected to increase in frequency and severity over the coming century, and predicting the effects of strong hurricanes on forest communities requires an understanding of the damage patterns caused to individual trees and what drives those damage patterns. To better understand damage patterns caused by a category 5 hurricane, we censused nine permanent vegetation plots across the island of Dominica, West Indies, nine months after Hurricane Maria took a direct path over the island. We measured size, damage, and mortality for all adult trees, and measured wood density and carbon content for the 44 most common species to calculate biomass and carbon relocation from the hurricane. Despite widespread major tree damage (76% of trees), mortality nine months after the hurricane was relatively low (10% of trees). The most common damage types were stem snapping (40% of trees) and major branch damage (26% of trees), but the damage types with the highest rates of mortality were uprooting and being crushed by a neighboring tree (33% and 47% of uprooted and crushed trees died, respectively). Larger individual trees and species with lower wood density were more susceptible to snapping, uprooting and mortality, and trees on steeper slopes were more prone to being crushed by neighboring trees. Hurricane Maria caused an average loss of 44 Mg ha−1 of aboveground carbon and 90.3 Mg ha−1 of aboveground biomass. Synthesis – Trees in these hurricane-prone forests show a strong ability to survive extremely strong storms even when severely damaged, but substantial amounts of forest carbon are redistributed to the forest floor even when mortality rates are relatively low. Our data suggest that these hurricane-prone forests will continue to shift toward smaller, high wood-density species with increasing hurricane frequency and intensity.

Are underground organs able to store water and nutrients? A study case in non-arboreal species from the Brazilian Cerrado

In seasonal systems, species have specific traits to deal with water shortage. This is the case for plants in Neotropical savannas, where the dry season can endure 3 to 5 months without rain. Ecophysiological strategies to deal with the dry period are well known for savanna trees, however little is known for non-arboreal species such herbs and subshrubs concerning their water use strategies. In this study we analyzed traits related to water and nutrient storage in underground organs and leaves of non-arboreal Cerrado (Neotropical savanna of Brazil) plants. We hypothesized that underground organs are able to retain water and nutrients allowing non-arboreal plants to resprout even during water shortage. We measured wood density (WD) and saturated water content (SWC) in underground organs of 15 species differing in their growth form (5 herbs, 5 subshrubs and 5 shrubs). We also measured macronutrients concentration in underground organs and leaves of these species. We tested relationships between WD and SWC and between concentrations of underground and leaf macronutrients. We found that WD and SWC are negatively related, and that herbs showed the lowest WD, but the highest capacity to store water (higher SWC). We did not find any significant difference concerning nutrient content in underground organs and leaves among the growth forms; however, the leaf nutrient content was positively affected by the nutrient content in underground organs for N, K and Ca. We conclude that underground organs may have an important role on storing water and nutrients in savanna herbaceous species, which will promote their resprout even during the dry period.

Intra-Ring Wood Density and Dynamic Modulus of Elasticity Profiles for Black Spruce and Jack Pine from X-Ray Densitometry and Ultrasonic Wave Velocity Measurement

Currently, ultrasonic measurement is a widely used nondestructive approach to determine wood elastic properties, including the dynamic modulus of elasticity (DMOE). DMOE is determined based on wood density and ultrasonic wave velocity measurement. The use of wood average density to estimate DMOE introduces significant imprecision: Density varies due to intra-tree and intra-ring differences and differing silvicultural treatments. To ensure accurate DMOE assessment, we developed a prototype device to measure ultrasonic wave velocity with the same resolution as that provided by the X-ray densitometer for measuring wood density. A nondestructive method based on X-ray densitometry and the developed prototype was applied to determine radial and intra-ring wood DMOE profiles. This method provides accurate information on wood mechanical properties and their sources of variation. High-order polynomials were used to model intra-ring wood density and DMOE profiles in black spruce and jack pine wood. The transition from earlywood to latewood was defined as the inflection point. High and highly significant correlations were obtained between predicted and measured wood density and DMOE. An examination of the correlations between wood radial growth, density, and DMOE revealed close correlations between density and DMOE in rings, earlywood, and latewood

CarDen: A software for fast measurement of wood density on increment cores by CT scanning

Increment cores are often used in wood science for measuring wood density of trees non destructively and at large scale, for instance with the objective to assess the available biomass in a forest resource. This paper presents a software allowing to measure by X-ray computed tomography (CT) the wood density of thousands increment cores. The software is able to process 3000 cores per hour semi-automatically. Manual intervention may be required to control and eventually adjust the positioning of the cores. The software was tested on 30 trees from 13 temperate species. Two increment cores were taken from each tree: one 5 mm diameter core and one 4 mm diameter core. The obtained CT density of the cores was compared to reference data obtained by volume and mass measurement on the 5 mm cores. The reference data were used for tuning the software settings by leave-one-out cross validation method. The obtained root mean square error was below 10 kg/m3 (1.7%) for the 5 mm cores. For the 4 mm cores, the root mean square difference with the reference density of the 5 mm cores was 25 kg/m3 (4.2%).

Exclusion of invertebrates influences saprotrophic fungal community and wood decay rate in an experimental field study

Abstract Decomposer communities perform an essential ecosystem function by recycling nutrients. However, the effect of higher trophic levels on microbial decomposer communities and rate of decomposition is poorly understood. We therefore conducted an exclusion experiment to test the effect of invertebrates on fungal decomposer communities in dead wood, repeated at 30 sites in two landscapes, and measured wood density to assess effect on decay rate. Invertebrates were excluded from recently cut logs by cages with a 1‐mm‐mesh net, and fungal communities in caged logs were compared to logs accessible to invertebrates by DNA metabarcoding analyses. Accessible logs included control logs, cage control logs and positive control logs. We found that exclusion of invertebrates had a significant effect on fungal community composition. For example, the wood decay fungi Trametes versicolor and T. ochraceawere significantly more abundant in accessible logs than in caged logs. The strongest effect on fungal community composition, however, was attributed to differing baseline conditions in the individual trees. When accounting for these baseline differences, caged logs had significantly higher wood density than control logs after 2 years, indicating lower rates of wood decay in caged logs. Further studies, spanning several years, are required to fully understand the influence of invertebrates on fungi and wood decay. However, our results indicate that invertebrates influence both the composition of saprotrophic communities in dead wood and their decomposition function, which is vital to forest ecosystems. A plain language summary is available for this article.

Xylem adjusts to maintain efficiency across a steep precipitation gradient in two coexisting generalist species.

Trees adjust the configuration of their conductive system in response to changes in water availability, maximizing efficiency in wet environments and increasing safety in dry habitats. However, evidence of this general trend is not conclusive. Generalist species growing across broad climatic gradients provide an ideal framework to assess intra-specific xylem adjustments under contrasting environmental conditions. Our aims were to compare the response of xylem traits to variations in precipitation of two co-occurring generalist tree species, and to assess climate control on xylem trait variability and co-ordination. We evaluated xylem traits of Embothrium coccineum (Proteaceae, evergreen) and Nothofagus antarctica (Nothofagaceae, deciduous) in three areas across an abrupt precipitation gradient, from 500 to 2500 mm, in southern Chile. We measured wood density, vessel lumen area and density, percentage of conductive area and vessel grouping, and estimated the hydraulic function from anatomical measurements in 60 individuals per species. Both species shared a common pattern of response along the precipitation gradient, with an increase in vessel density with dryness, but without changes in estimated hydraulic conductivity. Xylem traits in E. coccineum were more variable and more responsive to the climate gradient, decreasing vessel lumen area and increasing wood density, whereas vessel grouping showed contrasting patterns between species. Additionally, the analysis of trait co-ordination at the individual level revealed a tighter co-ordination among xylem traits in E. coccineum. Estimated xylem efficiency was maintained in combination with different levels of expected xylem safety within species. Reduction in vessel lumen area was compensated through large increases in vessel density, thus breaking the trade-off between xylem efficiency and safety. Otherwise, the existence of alternative internal adjustments in coexisting species to face similar climatic constraints might increase resilience of temperate forests against unpredictable changes in climatic conditions.

Nocturnal transpiration in 18 broadleaf timber species under a tropical seasonal climate

Global increase in night time as compared to day time temperatures results in an increased nocturnal VPD, which possibly increases nocturnal transpiration of plants. However, there are few studies on nocturnal transpiration of plantations in the tropics. Here, we investigated the ratio of nocturnal to daily transpiration and its seasonal differences in timber plantations of tropical angiosperm tree species in low land seasonal tropical botanical garden in southwest China. We measured sap flow in 18 tree, comprising of nine evergreen and nine deciduous species, during three months in the wet season and three months in the dry season between 2012 and 2013. We partitioned the nocturnal sap flux density (SFD) into nocturnal transpiration and trunk water recharge. We also measured wood density to investigate its relationship with nocturnal sap flux density. Our results showed that the mean nocturnal (whole night-time) VPD was linearly correlated with mean nocturnal SFD (R2 > 0.41–0.73 across species) in both the wet and dry seasons. During the wet season, the ratio of nocturnal SFD to daily SFD was 0.12–0.19 and 0.15–0.2 among evergreen and deciduous species, respectively. During the dry season, this ratio increased to 0.18–0.28 for evergreen species. For evergreen species, the nocturnal trunk water recharge and nocturnal transpiration in the wet season were between 11.37–59.80% and 40.20–88.62% of nocturnal SFD, respectively. For deciduous species, these values were 18.10–66.26% and 81.90–33.73%, respectively. We found an inverse relationship between nocturnal SFD and wood density (R2 = 0.24, P = ≤0.05) across the 18 studied species. In conclusion, this study demonstrates a substantia amount of nocturnal transpiration in a number of tropical tree species, even in the wet season and increased nocturnal transpiration in evergreen species in dry season. However, there was not any significant difference of the nocturnal SFD between evergreen and deciduous species during the wet season. Nocturnal transpiration is constrained by wood density across species. High nocturnal air temperature will result in increased transpirational demand and hence water loss at night. Our findings revealed important implications for nocturnal transpiration on soil-plant equilibrium and hydrology of forest ecosystems in the seasonal tropics.

Wood traits related to size and life history of trees in a Panamanian rainforest.

Wood structure differs widely among tree species and species with faster growth, higher mortality and larger maximum size have been reported to have fewer but larger vessels and higher hydraulic conductivity (Kh). However, previous studies compiled data from various sources, often failed to control tree size and rarely controlled variation in other traits. We measured wood density, tree size and vessel traits for 325 species from a wet forest in Panama, and compared wood and leaf traits to demographic traits using species-level data and phylogenetically independent contrasts. Wood traits showed strong phylogenetic signal whereas pairwise relationships between traits were mostly phylogenetically independent. Trees with larger vessels had a lower fraction of the cross-sectional area occupied by vessel lumina, suggesting that the hydraulic efficiency of large vessels permits trees to dedicate a larger proportion of the wood to functions other than water transport. Vessel traits were more strongly correlated with the size of individual trees than with maximal size of a species. When individual tree size was included in models, Kh scaled positively with maximal size and was the best predictor for both diameter and biomass growth rates, but was unrelated to mortality.

Paludification of boreal soils reduces wood decomposition rates and increases wood‐based carbon storage

Over long time periods, paludification reduces aboveground productivity resulting in forest retrogression. Paludified forests are typified by intense accumulation of the soil organic layer and a reduction in soil temperatures and nutrient availability. En route to paludification, early successional forests experience large inputs of deadwood biomass during the senescence of the post‐fire cohort, much of which may be entombed in this rapidly growing soil organic layer. Here we examined the effects of paludification across a >2000‐year chronosequence of black spruce forests on wood decomposition using three complementary approaches. We (1) repeatedly measured wood density of logs through time, (2) utilize a time‐series of logs that varied in time since death, and (3) estimate woody biomass at the stand level as it progresses from live trees to snags, logs and ultimately to buried or decomposed deadwood. Together these approaches demonstrated a 6–7‐year delay before the onset of rapid decomposition. We also found strong evidence that paludification results in a large proportion of logs becoming buried in the soil organic layer. Stand level modeling indicates that the rates of accumulation of buried deadwood were greatest following the senescence of the post‐fire cohort when both soil organic layer build‐up and creation of deadwood peaked. Following this period of high deadwood creation, stands enter a retrogressive state whereby productivity continues to decline albeit more slowly. Continued losses in woody carbon biomass from trees during this retrogressive state are offset by lower wood decomposition rates and a high biomass of accumulated buried deadwood, essentially stabilizing the wood based carbon budget in these ecosystems. We recommend that partial cutting be conducted prior to or near the senescence of the post‐fire cohort to improve emulation of natural forest succession in terms of both live tree and deadwood biomass. Furthermore, deadwood during this period has an extremely short residence time and the dynamics of deadwood should recover much quicker than if harvesting is conducted later in succession when there is less live tree biomass and deadwood has longer residence times.

Applicability of effective medium theory to wood density measurements using terahertz time-domain spectroscopy

The use of an effective medium theory is important when accurately measuring wood density using millimeter and terahertz wave techniques. To confirm the applicability of this theory to the evaluation of wood density, the relative permittivity and dielectric loss of oven-dry flat-sawn specimens of 11 different wood species were measured in a frequency range of 0.15–1.2 THz using a transmission measurement system for terahertz time-domain spectroscopy. A mixture model based on the effective medium theory well explained the density dependence of relative permittivity over the entire frequency range, while it did not fully explain that of dielectric loss, especially for higher frequencies. This indicates that wood scatters the terahertz wave with a wavelength close to the transverse sectional dimensions of the pores in wood in the same way as Mie scattering. It was found from the dielectric loss spectrum of wood substance that the frequency around 0.23 THz was preferable for the nondestructive evaluation of wood.

Fibre wall and lumen fractions drive wood density variation across 24 Australian angiosperms

Wood density is considered a key plant trait, affecting mechanical and physiological performance, yet its biological meaning is still rather unclear. Accordingly we investigated the anatomical underpinnings of wood density in trees and shrubs. We measured wood density and anatomical traits in distal stems 4–10 mm diameter under bark in 24 Australian species. Proportions of wood components that are functionally distinct were analysed, including fibre wall and lumen, vessel wall and lumen, and axial and ray parenchyma. Wood density was mainly driven by the density of wood outside vessel lumens (densityNV) rather than by vessel lumen fraction. In turn, densityNV variation was chiefly affected by fibre wall and lumen fractions. Considerable anatomical variation was observed at a given densityNV, especially among medium-densityNV species (0.60–0.85 g cm−3); this range of medium densityNV roughly translates to 0.50–0.75 g cm−3 of overall density. The anatomy of these species formed a continuum from low fibre lumen and medium parenchyma fractions to medium fibre lumen and low parenchyma fractions. Our data suggest that wood density is an emergent property influenced by a complex anatomy rather than an unambiguous functional trait, particularly in medium-density species. With much anatomical variation, they likely represent a wide range of ecological strategies.

Measurement of intra-ring wood density by means of imaging VIS/NIR spectroscopy (hyperspectral imaging)

Abstract This paper reports a novel application of hyperspectral imaging (a spectroscopic technique) for measuring wood density profiles at the growth ring scale. The measurements were performed with a spatial resolution of 79 µm. In the present case, hyperspectral imaging was used to measure wood sample reflectance for light in the wavelength range between 380 and 1028 nm, with a resolution of approximately 0.6 nm. The work was performed with 34 samples collected from 34 trees of Pinus pinea. A total of 34,093 density points were used to create and validate a partial least-squares (PLS) regression that converts spectroscopic reflectance data into density values. The coefficient of determination value between the present method and X-ray microdensitometry is 0.810 with a root mean squared error of 6.54×10-2 g.cm-3.

A non-destructive field method for measuring wood density of decaying logs

Decaying dead wood density measurements are a useful indicator for multiple purposes, such as for estimating the amount of carbon in dead wood and making predictions of potential diversity of dead wood inhabiting fungi and insects. Currently, qualitative decay phases are used as wood density estimates in many applications, since measuring the density is laborious. A quantitative measure of density would, however, be preferred over the qualitative one. Penetrometers, which are commonly used for measuring the density of standing trees, might also be applicable to dead wood density measurements. We tested the device for making quick, quantitative measurements of decaying logs. The penetrometer measures the depth into which a pre-loaded spring forces a pin in the wood. We tested pins of 5 and 10 mm diameter together with an original 2.5 mm pin and compared the results with gravimetric density measurements of the sample logs. Our results suggest that the standard pin works for less decayed wood, but for more decomposed wood, the thicker 5 mm pin gave more reliable estimates when the penetration measures were converted to densities with a linear regression function (R = 0.62, F = 82.9, p = 0.000). The range of wood densities successfully measured with the 5 mm pin was from 180 to 510 kg m. With the 10 mm pin, the measuring resolution of denser wood was compromised, while the improvement at the other end of density scale was not large. As a conclusion, the penetrometer seems to be a promising tool for quick density testing of decaying logs in field, but it needs to be modified to use a thicker measuring pin than the standard 2.5 mm pin.2–3

Measuring wood density by means of X-ray computer tomography

• Wood density is a characteristic of major interest. Usually, it is used as an indicator of wood quality; however, in the context of global change, it is increasingly used for biomass and carbon storage estimations. X-ray computer tomography is a method which enables quick estimates of wood density after applying a calibration procedure. • A review of the literature is presented in this article. Most of the previous studies have been performed in the 80’s or at the beginning of the 90’s. • In this study, the relationship between wood density and Hounsfield numbers was investigated using a recent medical scanner. A linear relationship was fitted using a calibration data set which consisted in tropical wood samples representing a large range of densities ranging between 133 and 1319 kg m−3, and then validated using an independent data set (mainly temperate tree species). The fitted relationships were very strong (R2 > 0.999), whichever the tested scanner settings, with slight but significant effects of the current voltage and reconstruction filters. The RMSE values computed from the validation data set ranged between 5.4 and 7.7 kg m−3 for densities ranging between 364 and 821 kg m−3. • In conclusion, this method of calibration enables the use of a medical scanner to obtain maps of wood density, in a fast and non destructive way, and with a very good accuracy. Very interesting perspectives are opened regarding biomass distribution within trees.

Batch measurements of wood density on intact or prepared drill cores using x-ray microdensitometry

The performance of a batch scanning x-ray densitometer for measuring wood density without sample preparation, i.e., on intact drill cores, or on rectangular samples prepared from drill cores, was analysed. Effects of x-ray intensity, sample thickness and fiber direction, as well as extractives content, were evaluated for young (mainly sapwood) and old (mainly heartwood) wood from Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.). The x-ray power level used as standard (1.4 kW; 40 kV and 35 mA) seemed appropriate for the tested species and specimen thickness. The density of intact drill cores could be determined with a mean standard deviation of 1.6% for each sample, with a single machine run, if the cores were mounted with a fixed fiber direction and calibrations were made for each wood type. The corresponding precision for rectangular samples was 1.0%. Further improvements are attainable by using standard reference samples in each machine run and batch-wise analysis. For the chosen wood types and measurement technique, a sample thickness of 5 mm should give the best precision. However, for species with very narrow rings, thinner samples would improve the spatial resolution when ring boundaries are angled or curved. Extractives should be removed, especially for pine, but possibly also for spruce, if high precision in density determination is required.