Wood Density Research Articles

Density profile and NIRs spectra of boron-densified wood at different compression ratios

The present study investigates the effect of pre-treatment and compression ratio (CR) on the enhancement of density in three wood species, specifically nyatoh (Palaquium spp.), pisang putih (Mezzettia spp.) and sepetir (Sindora spp.) cultivated in the North Kalimantan Province. The phenomenon occurred during those treatments was analyzed using X-ray Densitometer and Near Infrared Spectroscopy (NIRs). The wood was subjected to a pre-treatment process involving hot immersion within 2 and 5% of boron solutions at 80 °C for 3 hours. Subsequently, a densification process was performed using hot press machine at 30 kg/cm2 of pressure and 160 °C of temperature for 15 minutes with 20% and 40% CR from the initial thickness. The findings indicated a significant increase in density values for densified wood in comparison to untreated wood. The density values for nyatoh, pisang putih, and sepetir exhibited increases of approximately 31.73%, 36.52%, and 35.04%, respectively. The application of a higher CR leads to a more substantial enhancement in wood density, with an increase of approximately 23.08-25.53% and 30.13-47.01% at 20% and 40% of CR, respectively. The density distribution across the thickness exhibited an M-shape gradient, which convinced the surface densification occurred during the process. NIRs spectra absorbance revealed a prominent peak at wavelength 2178 nm for untreated wood, whereas no such peak was observed in the boron-densified wood. This phenomenon associated with the degradation of hemicellulose during the subsequent treatment applied.

Damage to tropical forests caused by cyclones is driven by wind speed but mediated by topographical exposure and tree characteristics.

Each year, an average of 45 tropical cyclones affect coastal areas and potentially impact forests. The proportion of the most intense cyclones has increased over the past four decades and is predicted to continue to do so. Yet, it remains uncertain how topographical exposure and tree characteristics can mediate the damage caused by increasing wind speed. Here, we compiled empirical data on the damage caused by 11 cyclones occurring over the past 40 years, from 74 forest plots representing tropical regions worldwide, encompassing field data for 22,176 trees and 815 species. We reconstructed the wind structure of those tropical cyclones to estimate the maximum sustained wind speed (MSW) and wind direction at the studied plots. Then, we used a causal inference framework combined with Bayesian generalised linear mixed models to understand and quantify the causal effects of MSW, topographical exposure to wind (EXP), tree size (DBH) and species wood density (ρ) on the proportion of damaged trees at the community level, and on the probability of snapping or uprooting at the tree level. The probability of snapping or uprooting at the tree level and, hence, the proportion of damaged trees at the community level, increased with increasing MSW, and with increasing EXP accentuating the damaging effects of cyclones, in particular at higher wind speeds. Higher ρ decreased the probability of snapping and to a lesser extent of uprooting. Larger trees tended to have lower probabilities of snapping but increased probabilities of uprooting. Importantly, the effect of ρ decreasing the probabilities of snapping was more marked for smaller than larger trees and was further accentuated at higher MSW. Our work emphasises how local topography, tree size and species wood density together mediate cyclone damage to tropical forests, facilitating better predictions of the impacts of such disturbances in an increasingly windier world.

Nitrogen-fixing and non-nitrogen-fixing legume plants differ in leaf nutrient concentrations and relationships between photosynthetic and hydraulic traits.

Legumes account for a significant proportion of plants in the terrestrial ecosystems. Nitrogen (N)-fixing capability of certain legumes is a pivotal trait that contributes to their ecological dominance. Yet, the functional traits and trait relationships between N-fixer and non-N-fixer legumes are poorly understood. Here, we investigated 27 functional traits associated with morphology, nutrients, hydraulic conductance and photosynthesis in 42 woody legumes (19N-fixers and 23 non-N-fixers) in a common garden. Our results showed that N-fixers had higher specific leaf area, photosynthetic phosphorus (P)-use efficiency, leaf N, and iron concentrations on both area and mass basis, N/P ratio, and carbon (C) to P ratio, but lower wood density, area-based maximum photosynthetic rate (Aa), photosynthetic N-use efficiency, leaf mass- and area-based P and molybdenum and area-based boron concentrations, and C/N ratio, compared with non-N-fixers. The mass-based maximum photosynthetic rate (Am), stomatal conductance (gs), intrinsic water-use efficiency (WUEi), mass- and area-based leaf potassium and mass-based boron concentrations, leaf hydraulic conductance (Kleaf), and whole-shoot hydraulic conductance (Kshoot) showed no difference between N-fixers and non-N-fixers. Significant positive associations between all hydraulic and photosynthetic trait pairs were found in N-fixers, but only one pair (Kshoot-Aa) in non-N-fixers, suggesting that hydraulic conductance plays a more important role in mediating photosynthetic capacity in N-fixers compared with non-N-fixers. Higher mass-based leaf N was linked to lower time-integrated gs and higher WUEi among non-N-fixer legumes or all legumes pooled after phylogeny was considered. Moreover, mass-based P concentration was positively related to Am and gs in N-fixers, but not in non-N-fixers, indicating that the photosynthetic capacity and stomatal conductance in N-fixers were more dependent on leaf P status than in non-N-fixers. These findings expand our understanding of the trait-based ecology within and across N-fixer and non-N-fixer legumes in tropics.

NIR Inversion Model of Larch Wood Density at Different Moisture Contents Based on MVO-BPNN

NIR Inversion Model of Larch Wood Density at Different Moisture Contents Based on MVO-BPNN

Coordination of bark and wood traits underlies forest‐to‐savanna evolutionary transitions

AbstractAimTo test the hypothesis that adaptive shifts leading to the assembly of tropical savannas involved coordination between bark and wood traits and to understand the underlying mechanisms.LocationTropical South America.TaxonAngiosperms (woody).MethodsWe compiled data on three bark traits (total, inner and outer relative bark thickness), wood density, maximum height, five secondary xylem traits and on species' habitat information (light environment, climate, soil and fire history) for Neotropical savanna, forest and generalist species (biome groups). We tested for pairwise and multivariate associations among traits across species and if biome group and habitat conditions explained species positions along the resulting strategy axes.ResultsTraits covaried along four different axes. The first axis was consistent with a trade‐off between fire (thick barks) and shade tolerance (low bark to diameter ratio, high vessel density) and contributed to differentiate the three biome groups according to the preference for shaded environments. Forest species also differed from savanna and generalist species in a separate axis by being more resource acquisitive. Maximum height and wood density did not strongly trade‐off with bark thickness, although maximum height was negatively covaried with relative outer bark thickness. Preference for shaded conditions was the main driver of variation in the two principal strategy axes, but temperature, fire and soil sand content also explained differences in plant stature between savanna and generalist species.Main ConclusionsAllocation to bark is constrained by trade‐offs with wood, opposing shade‐tolerant and acquisitive forest species to fire‐resistant and conservative savanna species. Rather than a single strategy axis, three axes are necessary to understand the functional differences among savanna, forest and generalist species. Because two of these axes are controlled by light availability, the associated traits tend to covary in space and time, but not across species.

Phloem Sap and Wood Carbon Isotope Abundance (δ13C) Varies with Growth and Wood Density of Eucalyptus globulus under Nutrient Deficit and Inform Supplemental Nutrient Application

Eucalyptus globulus, commonly known as blue gum or southern blue gum, is a tall, evergreen tree endemic to southeastern Australia. E. globulus is grown extensively in plantations to improve the sustainability of timber and fibre production across Australia. Sustainable forest management practices necessitate the consideration of ‘off-site’ carbon and ecological footprints. Pursuing optimal supplemental nutrient application and maximum growth rates is therefore critical to the establishment of a sustainable timber and fibre production industry. Biological indicators that can predict growth responses are therefore of extreme value. We investigated the carbon isotope abundance of wood cellulose (δ13Ccel) in E. globulus to determine potential relationships with the carbon isotope abundance of phloem sap (δ13Cphl) where the trees were subjected to different level of nutrient availability. This study also sought to determine the effect of nutrient additions on the growth of the E. globulus and to quantify the relationship between the volumetric growth of wood and δ13Ccel. Phloem sap and wood cores were collected from trees within study plots which were subjected to seven nutrient treatments over a two-year period in a monoculture E. globulus plantation in South Australia. Phloem sap was collected using the razor blade technique and wood cores were collected using a stem borer. The carbon isotope abundance (δ13C) of phloem sap and wood grown in the radial direction of the stem were determined. The basic and dry densities of wood were determined, and their relationships with phloem and wood δ13C were established. The δ13Cphl was significantly correlated with δ13Ccel. The relationship between δ13Ccel and the wood density of the respective wood sections was significant but did not consistently show the same pattern. There was no significant variation in basic density observed along the radial direction of the stem wood of the short-rotation E. globulus trees. A positive correlation was observed between δ13Ccel and the wood basic density, but the relationship was not consistent along the radial direction of the stem. However, positive correlations were observed between δ13Ccel and the air-dry density of respective wood sections. The relationship between phloem and wood δ13C and the relationship between δ13C and wood density along the radial direction of the stem needs to be considered while monitoring forest growth under nutrient- and water-limited conditions.

Relationship Between Wood Properties and Drying Qualities at Three Age Groups of Mindi (Melia azedarah L) Tree for Furnitur Materials

All wood based products should have been dried to ensure their stable dimension. Indicators of stable dimension can be figured-out from wood physical properties, especially ratio of tangensial shrinkage to radial shrinkage (T/R ratio) and wood drying properties at high temperature. From those two indicators could be predicted the drying quality of wood as a basic to determine minimum – maximum of drying temperature. This research aimed to look-into the relationship between wood properties of wood and drying quality of mindi (Melia azedarach L)wood at their 5, 9, and 13 year-old trees. The preparing of test samples, and testing methods on wood physical properties covered moisture content, air-dry density, and shrinkage in tangential and radial direction, which referred to the BS 1957. Meanwhile, drying properties followed the modified Terazawa’s method. Five classes of wood drying qualities could be derived from the analysis of T/R ratio and drying property at each tree age group. Results revealed that wood density ranged about 0.46 – 0.58 g/cm3. Drying quality of each wood (except the portion near the pith) belong to B (good) for 13 years old, C (fair) for 9 years, and D (poor) for 5 years old. Related to the drying quality, the minimum – maximum temperature for 13 years mindi wood was 55–85 oC; for 9 years was 50–80 oC; and for 5 years was 40–65 oC. Supported by the performance of wood surface, especially at 13 years old, mindi wood was suitable for wooden furniture.

INFLUENCE OF SITES ON THE PHYSICAL AND MECHANICAL PROPERTIES OF NATIVE TROPICAL WOODS

The Amazon rainforest displays wide ecological diversity, reflected in its wood variation. The study evaluated the influence of different locations on the properties of wood from native tropical species extracted from the Brazilian Amazon. The most frequent species in the locations were selected, and a total of 104 trees were extracted. The logs were sawed breakdown to make beams (50 × 110 × 2,000 mm). The wood density and mechanical resistance of these samples were determined. The wood density ranged of 0.25-1.00 g/cm3, modulus of elasticity and rupture in static bending ranged of 5,982-19,025 MPa and 35-204 MPa, respectively. For compressive strength parallel to the grain, the range was 24-111 MPa; the strength of wood compressed parallel was 20-245 MPa, and the shear strength was 50-245 MPa. The study detected differences in the physical and mechanical properties of the woods regarding the origin of the sites (Amazonas-Pará/Brazil), with the modulus of elasticity and the wood density showing the greatest variations.

EVALUATION OF DYNAMIC AND STATIC MODULI OF ELASTICITY OF HYBRID EUCALYPTUS WOOD FROM DIFFERENT LOCATIONS IN GHANA

This study explores the mechanical properties of hybrid eucalyptus wood, with a focus on dynamic and static moduli of elasticity (MOE), which is crucial for understanding the stiffness behaviour of wood. The research employs acoustic and static measurements on samples prepared from six trees sourced from Winneba and Amantia in Ghana. The results reveal significant variations in static and dynamic MOE, with higher static MOE observed in both Amantia and Winneba samples. However, Winneba and Amantia samples at the tree level were found to be insignificant statistically. The densities of the samples from the two locations, Winneba and Amantia, were found to be significantly different. Correlation studies revealed strong relationships between wood density and static MOE, as well as static and dynamic MOE, providing valuable insights into the comprehensive characterization of the eucalyptus globulus species grown in Ghana.

Alpha and beta diversity of functional traits in subtropical evergreen broad-leaved secondary forest communities.

Intra-speciic variation is the main source of functional trait diversity and has similar ecological effects as inter-speciic variation. We studied 79 species and 3546 individuals from 50 ixed monitoring plots in subtropical evergreen broad - leaved secondary forests in Zhejiang Province, China. Using trait gradient analysis, we examined nine traits (speciic leaf area, leaf dry matter content, wood density, leaf area, chlorophyll content, leaf nitrogen content, leaf phosphorus content, leaf potassium content, and nitrogen-phosphorus ratio) by decomposing species functional traits into alpha (within-community) and beta (among-communities) measure the impact of environmental gradients and the presence of other species on the variation of traits. All nine functional traits showed some degree of differentiation in the forest communities, with a greater range of variation in alpha values than in beta values . Correlations were signiicantly different between the trait differences in the communities. The alpha values of each trait showed a higher correlation with other components than the beta values. The factors affecting intra-speciic trait variation were relatively complex. The alpha component had a more signiicant and stronger effect on intra-speciic trait variation compared to the beta component. Abiotic factors, such as soil nutrient content, soil nitrogen-phosphorus content, directly affected the beta component. In contrast, biotic factors, such as tree height variation, had a direct and stronger effect on the alpha component. Our results demonstrate that alpha and beta components, as independent differentiation axes among coexisting species, have different sensitivities to different environmental factors and traits in different ecological strategies and spatial scales. Trait gradient analysis can more clearly reveal the variation patterns of species traits in communities, which will help to understand the scale effects and potential mechanisms of trait relationships.

Chemical and Thermal Exposure Risks in a Multi Compartment Training Structure

Providing NFPA 1403 compliant live-fire training can present thermal and chemical exposure risk to instructors and students. To reduce risk, training academies, fire departments, instructors, and standards setting technical committees need more information on how different training fuels used in common training structures can impact the environment in which firefighter training occurs. This study utilized a traditional concrete training structure with multiple compartments to characterize training environments with three different fuel package materials [i.e., low density wood fiberboard, oriented strand board (OSB), and wood pallets]. Exposure risks for a fire instructor located on either the first or second floor were characterized using measurements of heat flux, air temperature and airborne concentrations of several contaminants including known, probable, or possible carcinogens. It was hypothesized that utilizing a training fuel package with solid wood pallets would result in lower concentrations of these airborne contaminants [aldehydes, polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs)] than wood-based sheet goods containing additional resins and/or waxes. Additionally, it was hypothesized that these concentrations would be lower than in the single compartment Fire Behavior Lab presented in a companion manuscript. For all measured compounds other than hydrochloric acid, airborne concentrations were 10 to 100 times lower than in the Fire Behavior Lab. OSB-fueled fires produced the highest median concentrations of total PAHs and VOCs such as benzene, while the pallet fuel package produced the lowest median concentrations of these compounds. These trends generally followed the qualitative visual obscuration created by each fuel. Additional tests were conducted on the OSB-fueled fires with increased ventilation and an alternate means of reducing visibility through smoldering smoke barrels. This OSB experiment with increased ventilation resulted in the highest temperatures in the fire room but the lowest impact on visibility throughout the structure, as well as the lowest overall concentrations of contaminants in this study. In contrast, the smoldering straw-filled smoke barrel created a highly obscured environment (with minimal impact on thermal environment) and some of the highest concentrations of the targeted contaminants of any test. These data may be useful in balancing obscuration for training with potential exposure to thermal stressors and contaminants.

Developing poplar wood into a green structure-decoration integrated material for prefabricated wooden building application

Fast growing poplar wood poses significant challenges including low mechanical strength, poor dimensional stability and weak texture, limiting its direct application in the field of building structures and decoration. We treated poplar wood using compression, digital printing and waterproofing techniques to develop a green structure-decoration integrated material. The compression treatment significantly improved the wood density, fiber orientation and surface smoothness. At a compression ratio of 60 %, poplar veneer demonstrates remarkable improvements in modulus of elasticity (MOE), modulus of rupture (MOR) and surface smoothness, with increases of 222.53 %, 233.53 % and 93.20 %, respectively, compared to uncompressed wood. Notably, this compression treatment reduces the surface roughness of poplar to 0.75 μm, meeting the flatness requirements for digital printing. Consequently, clear textures and vibrant colors are directly printed onto the flat surface of compression-densified poplar wood, eliminating the need for traditional surface sanding pre-treatment process, and accordingly improving the efficiency of the material preparation. Furthermore, a final waterproofing emulsion spraying treatment creates a dense micro/nanoscale hierarchical structure on the surface, enabling the compression-densified poplar wood samples to achieve MOE and MOR of 14.15 GPa and 123.00 MPa respectively, even after water absorption and re-dried processes. These values consistently exceed the standard value of MOE (12.50 GPa) and MOR (35.00 MPa) for the highest grade (TCT40) specified in GB50005-2017, indicating significantly improved structural stability. The structure-decoration integrated materials developed in this study offer high strength and dimensional stability, making them promising candidates for high value utilization in prefabricated wooden buildings.

Environmental filtering of regeneration patterns in a forest dynamic mosaic in south-central Chile

A trade-off between growth in high light and survival under shade is widely regarded as the main driver of secondary succession in humid forests. Outside the humid tropics, however, the microclimates of large openings may select for traits other than those that maximize growth rates. We tested for differential filtering of sapling functional traits by four different microenvironments in a south-temperate forest in south-central Chile. We measured light, temperatures, humidity, soil nutrients and sapling densities in each of four phases of a forest dynamic mosaic: shaded understoreys, tree-fall gaps, Chusquea bamboo thickets, and clearings. We then measured leaf, wood and reproductive traits, as potential predictors of species’ regeneration patterns. Clearings were exposed to more than twice as many frost days as any other forest phase, and to much larger vapour pressure deficits in summer. Clearings were compositionally distinct from the other three phases, which were indistinguishable from each other. Saplings of 6 out of 20 common arborescent species were significantly associated with one or other of the four phases. These associations were best predicted by a three-trait model combining seed mass, leaf dry matter content, and % winter leaf retention; though this model explained only 10% of observed variation. No species was significantly associated with bamboo thickets. Community-weighted trait means showed that large seeds were the most distinctive trait of understorey plots, whereas bamboo thicket plots had the highest average wood density, and winter leaf retention was significantly lower in clearings than in any other forest phase. Despite the abundant recruitment of large-leaved (semi)deciduous species in clearings, several evergreens with small leaves (< 3.5 cm2) also established primarily or exclusively in clearings. Although this study confirms the strong environmental filtering imposed by the microclimates of clearings in some temperate forests, it reveals more functionally diverse responses to clearing environments than was reported in a parallel study in New Zealand. Smaller sample sizes may partly explain why overall we found less evidence of regeneration niche differentiation and environmental filtering than in the New Zealand study, although attenuation of filtering by vegetative reproduction may also have contributed.

Spatial mapping of key plant functional traits in terrestrial ecosystems across China

Abstract. Trait-based approaches are of increasing concern in predicting vegetation changes and linking ecosystem structures to functions at large scales. However, a critical challenge for such approaches is acquiring spatially continuous plant functional trait maps. Here, six key plant functional traits were selected as they can reflect plant resource acquisition strategies and ecosystem functions, including specific leaf area (SLA), leaf dry matter content (LDMC), leaf N concentration (LNC), leaf P concentration (LPC), leaf area (LA) and wood density (WD). A total of 34 589 in situ trait measurements of 3447 seed plant species were collected from 1430 sampling sites in China and were used to generate spatial plant functional trait maps (∼1 km), together with environmental variables and vegetation indices based on two machine learning models (random forest and boosted regression trees). To obtain the optimal estimates, a weighted average algorithm was further applied to merge the predictions of the two models to derive the final spatial plant functional trait maps. The models showed good accuracy in estimating WD, LPC and SLA, with average R2 values ranging from 0.48 to 0.68. In contrast, both the models had weak performance in estimating LDMC, with average R2 values less than 0.30. Meanwhile, LA showed considerable differences between the two models in some regions. Climatic effects were more important than those of edaphic factors in predicting the spatial distributions of plant functional traits. Estimates of plant functional traits in northeastern China and the Qinghai–Tibetan Plateau had relatively high uncertainties due to sparse samplings, implying a need for more observations in these regions in the future. Our spatial trait maps could provide critical support for trait-based vegetation models and allow exploration of the relationships between vegetation characteristics and ecosystem functions at large scales. The six plant functional trait maps for China with 1 km spatial resolution are now available at https://doi.org/10.6084/m9.figshare.22351498 (An et al., 2023).

Evolutionary history shapes variation of wood density of tree species across the world

The effect of evolutionary history on wood density variation may play an important role in shaping variation in wood density, but this has largely not been tested. Using a comprehensive global dataset including 27,297 measurements of wood density from 2621 tree species worldwide, we test the hypothesis that the legacy of evolutionary history plays an important role in driving the variation of wood density among tree species. We assessed phylogenetic signal in different taxonomic (e.g., angiosperms and gymnosperms) and ecological (e.g., tropical, temperate, and boreal) groups of tree species, explored the biogeographical and phylogenetic patterns of wood density, and quantified the relative importance of current environmental factors (e.g., climatic and soil variables) and evolutionary history (i.e., phylogenetic relatedness among species and lineages) in driving global wood density variation. We found that wood density displayed a significant phylogenetic signal. Wood density differed among different biomes and climatic zones, with higher mean values of wood density in relatively drier regions (highest in subtropical desert). Our study revealed that at a global scale, for angiosperms and gymnosperms combined, phylogeny and species (representing the variance explained by taxonomy and not direct explained by long-term evolution process) explained 84.3% and 7.7% of total wood density variation, respectively, whereas current environment explained 2.7% of total wood density variation when phylogeny and species were taken into account. When angiosperms and gymnosperms were considered separately, the three proportions of explained variation are, respectively, 84.2%, 7.5% and 6.7% for angiosperms, and 45.7%, 21.3% and 18.6% for gymnosperms. Our study shows that evolutionary history outpaced current environmental factors in shaping global variation in wood density.

Shade tree trait diversity and functions in agroforestry systems: A review of which traits matter

Abstract Shade trees in agroforestry systems confer ecosystem services, such as enhanced soil fertility from diverse litter inputs, microclimate regulation via shade, and disease mitigation through trophic and abiotic interactions. With this thriving role of agroforestry in sustainable agriculture, particularly for tree crops, systematic and reliable methods to select shade trees for specific agroecosystem outcomes are crucial. Plant functional traits offer a framework to describe, select and manage shade trees. Over the last decade, shade tree leaf functional traits and whole plant traits have been assessed in agroforestry systems. Yet, we lack amalgamated information on (i) what we know about shade tree trait relationships with functions to achieve desired agroecosystem outcomes, (ii) how decades of shade tree selection by farmers impacts agroforests inter‐ and intraspecific trait diversity, and (iii) which shade tree traits should be considered for achieving farmer priorities. We consolidate literature on Coffea arabica (coffee) and Theobroma cacao (cocoa) agroforestry systems to summarize the role of shade tree functional traits in three key ecosystem functions: soil fertility, microclimate modification and crop productivity. We compile global and regional datasets on tree functional trait diversity to show the functional space of agroforestry tree species compared with the overall functional space observed in plants. Despite, or maybe because of, high shade tree diversity, shade tree trait characterization remains coarse and commonly measured at the community scale in the literature. Based on published trait data, we show that farmers adjust the functional composition of shade trees to increase the recycling of soil nutrients (high leaf nitrogen), the production of wood (skewing towards lower wood densities) and the production of fruits (tendency towards high seed size). Common shade trees in coffee and cocoa systems fall in the mid‐range of leaf acquisitive to conservative strategies, providing evidence that expanding shade tree portfolios can improve, or even accelerate, functions. Synthesis and applications: Based on the agroforestry literature and on trait‐environment relationships, we propose a matrix of shade tree traits that influence desirable agroecosystem outcomes for farmers, which can guide fine‐scale coordination of trait expression and agroforestry functions.

A definition and standardised terminology for Blue Intensity from Conifers

The published literature of the past 20 years expresses inconsistent terminology for the Blue Intensity (BI) method that could lead to confusion in analysis and interpretation. In this technical note we propose a standard terminology based around the prevalent use of BI for the variant that is positively correlated with wood density derived from X-ray and equivalent wood anatomical techniques. We highlight significant practical advantages of this standard terminology for data analysis, scientific interpretations as well as archiving, and provide some cautionary examples that could occur if not adhering to this terminology. In future studies using BI, we recommend to explicitly clarify that the standard terminology is used with the following phrase: The BI data produced in this study is consistent with the ‘2024 BI standard terminology’.

Influence of Climatic Variables on the Stem Growth Rate in Trees of a Tropical Wet Forest

The growth of tropical wet forests has a significant relationship with the climate; aspects such as temperature and precipitation affect the species; however, few studies have characterized the stem growth rate of tropical tree species. This study’s objective was to characterize the effects of climatic variation on the interannual stem growth rate of eight species in tropical wet forest. Six trees per species were selected (n = 48 trees), and a dendrometer was installed to measure diametric growth bi-monthly between 2015 and 2018 (3 years), complemented with environmental measurements, to determine their growth equations from environmental variables and, finally, to define the relationship between the wood density and the stem growth rate. The results showed an average stem growth from 0.45 to 4.35 mm year−1, and 40 to 70% growth occurred in the months with the highest rainfall. Also, species with higher wood densities were found to have lower stem growth rates. Finally, the analysis of stem growth rate showed a significant relationship in all species between the variables of temperature and precipitation (R2 adj 0.88 to 0.96). Our results suggest that species with greater stem growth rates in wet tropical forests are more susceptible to climate changes, which may affect their dynamics in the face of potential drought scenarios and heat waves associated with climate change.

Fabrication of High-Performance Densified Wood via High-Pressure Steam Treatment and Hot-Pressing.

The fabrication of sustainable structural materials with high physical properties to replace engineering plastics is a major challenge for modern industry, and wood, as the most abundant sustainable natural raw material on the planet, has received a great deal of attention from researchers. Researchers have made efforts to enhance the physical properties of wood in order to replace plastics. However, it is also difficult to meet practical demands at a low cost. Herein, we report a simple and efficient top-down strategy to transform bulk natural basswood into a high-performance structural material. This three-step strategy involves partial removal of hemicellulose and lignin via treating basswood by boiling an aqueous mixture of NaOH and Na2SO3, and a high-pressure steam treatment (HPST) was applied to delignified wood followed by hot-pressing, which allowed the wood to absorb moisture uniformly and quickly. HPST-treated dense delignified wood (HDDW) has a tensile strength of ~420 MPa, which is 6.5 times better than natural basswood (~65 MPa). We systematically investigated the various factors affecting the tensile strength of this wood material and explored the reasons why these factors affect the tensile strength, as well as the intrinsic connection between the moisture absorbed through HPST and the increased tensile strength of HDDW. Through our experiments, we realized the enhancement mechanism of HDDW and the optimal experimental conditions for the fabrication of HDDW.

Variations in Wood Anatomy in Afrotropical Trees with a special emphasis on radial and axial parenchyma.

Understanding anatomical variations across plant phylogenies and environmental gradients is vital for comprehending plant evolution and adaptation. Prior studies on tropical woody plants have paid limited attention to quantitative differences in major xylem tissues, which serve specific roles in mechanical support (fibers), carbohydrate storage and radial conduction (radial parenchyma, rays), wood capacitance (axial parenchyma), and water transport (vessels). To address this gap, we investigate xylem fractions in 173 tropical tree species spanning 134 genera and 53 families along a 2200 m elevational gradient on Mount Cameroon, West Africa. We determined how elevation, stem height, and wood density affect interspecific differences in vessel, fiber, and specific axial (AP) and radial (RP) parenchyma fractions. We focus on quantifying distinct subcategories of homogenous or heterogeneous rays and apotracheal, paratracheal, and banded axial parenchyma. Elevation-related cooling correlated with reduced AP fractions and vessel diameters, while fiber fractions increased. Lower elevations exhibited elevated AP fractions due to abundant paratracheal and wide-banded parenchyma in tall trees from coastal and lowland forests. Vasicentric and aliform AP were predominantly associated with greater tree height and wider vessels, which might help cope with high evaporative demands via elastic wood capacitance. In contrast, montane trees featured a higher fiber proportion, scarce axial parenchyma, smaller vessel diameters, and higher vessel densities. The lack of AP in montane trees was often compensated by extended uniseriate ray sections with upright or squared ray cells or the presence of living fibers. Elevation gradient influenced specific xylem fractions, with lower elevations showing elevated AP due to abundant paratracheal and wide-banded parenchyma, securing greater vessel-to-parenchyma connectivity and lower embolism risk. Montane trees featured a higher fiber proportion and smaller vessel diameters, which may aid survival under greater environmental seasonality and fire risk.