Wood plays a crucial role in the economies of Central African countries, yet knowledge of the ecological and genetic determinants of intraspecific wood quality variation remains limited. In this study, we combined microsatellite-based population genetic analyses with short-wave near-infrared (NIR) hyperspectral imaging (HSI) of transverse wood slices to investigate the genetic diversity and wood spectral variability of three Entandrophragma cylindricum populations across distinct forest management units in northern Republic of the Congo. Genotyping of adult trees using 10 nuclear microsatellite loci revealed high levels of genetic diversity and low inbreeding across all populations. No significant genetic differentiation was detected among sites, although a weak but significant spatial genetic structure was observed, consistent with an isolation-by-distance (IBD) pattern, suggesting ongoing gene flow over the landscape. Hyperspectral imaging of transverse wood samples highlighted substantial inter-individual and site-related variability in NIR spectral signatures, with the highest spectral heterogeneity observed in the site characterized by the long-term logging history. However, this variability was not correlated with genetic distance, as confirmed by Mantel tests, indicating that site-specific context and logging intensity are the primary drivers of wood spectral variation. The results suggest that E. cylindricum populations retain considerable genetic potential for conservation and improvement. Moreover, the observed site-related variation in wood spectral traits highlights the importance of considering local growing context when interpreting wood spectral variability in tropical timber species. Further research combining near-infrared spectroscopy with detailed wood anatomical analyses and direct measurements of environmental variables would be necessary to disentangle the mechanisms underlying site-associated spectral variation.

Wood density is central for estimating vegetation carbon storage and a plant functional trait of great ecological and evolutionary importance. However, the global extent of wood density variation is unclear, especially at the intraspecific level. We assembled the most comprehensive wood density collection to date, including 109 626 records from 16 829 plant species across woody life forms and biomes (GWDD v.2, available here: doi: 10.5281/zenodo.16919509). Using the GWDD v.2, we explored the sources of wood density variation within individuals, within species and across environmental gradients. Intraspecific variation accounted for c. 15% of overall wood density variation (SD = 0.068 g cm-3). Variance was 50% smaller in sapwood than heartwood, and 30% smaller in branchwood than trunkwood. Individuals in extreme environments (dry, hot and acidic soils) had higher wood density than conspecifics elsewhere (+0.02 g cm-3, c. 4% of the mean). Intraspecific environmental effects strongly tracked interspecific patterns (r = 0.83) but were 70-80% smaller and varied considerably among taxa. Individual plant wood density was difficult to predict (root mean square error > 0.08 g cm-3; single-measurement R2 = 0.59). We recommend: (1) systematic sampling of multiple individuals and tissues for local applications; and (2) expanded taxonomic coverage combined with integrative models for robust estimates across ecological scales.

Wood density influences how quickly woody plants grow, how long they live and how much carbon they store, yet its global variation remains poorly mapped. Here we combined 109,626 wood density measurements from 16,829 species with 300,949 vegetation plots to produce a km-scale map of community-weighted wood density for every woody biome. Our model led to a prediction accuracy 32–51 % higher than previous global products, and a 1.8–3.7-fold wider wood density range (0.28–1.00 g cm−3; global mean: 0.57 g cm−3) than previously assumed. Spatial cross-validation showed low bias (±2.5 % of the mean), and uncertainties decreased from 20% in poorly sampled drylands and boreal regions to 5% in data-rich temperate forests. Mean annual temperature was the best predictor of community-weighted mean wood density, increasing by 0.01 g cm−3 for every 1°C change. We deliver a low-bias, high-resolution wood density layer for Earth system models, together with spatially explicit error maps. This study represents a major step forward for carbon accounting and trait-based forecasts of vegetation change. ### Competing Interest Statement The authors have declared no competing interest. European Research Council, 101001905 Agence Nationale de la Recherche, ANR-10-LABX-25-01, ;ANR-10-LABX-0041 Natural Environment Research Council, NE/S01537X/1, NE/M018458/1, NE/X013766/1, ;NOTALLOWED UK Research and Innovation, EP/Y003810/1 Leverhulme Trust, RPG-2020-341 Agencia Nacional de Investigación y Desarrollo, Anid-Fondecyt 1231025 São Paulo Research Foundation, 13/08722-5 Fondation Pour la Recherche Sur la Biodiversité, BIOSCENEMADA Smithsonian Tropical Research Institute, https://ror.org/035jbxr46 Ministerio de Ciencia, Innovación y Universidades, PID2021-123675OB-C43, TED2021-129770B-C21 Anusandhan National Research Foundation, SRG/2022/002286 SRM University, Andhra Pradesh, SRMAP/URG/E&PP/2022-23/012 Council of Scientific and Industrial Research, no.38(1349)/13/EMR-II National Council for Scientific and Technological Development, 12450/2021-4, 406941/2022-0, 307984/2022-2, PELD 441510/2020-5 Fundação de Amparo à Pesquisa do Estado do Amazonas, 01.02.016301.02529/2024-87 Brazilian Research Network on Climate Change, 01.13.0353-00 Science and Engineering Research Board, PDF/2021/003742/LS Deutsche Forschungsgemeinschaft, CRC TRR-228/1, CRS TRR-228/2 Fundação de Amparo à Ciência e Tecnologia de Pernambuco, https://ror.org/02te5rf52 Royal Society Te Apārangi, RDF-UOA1504, UOA1207 Natural Sciences and Engineering Research Council, https://ror.org/01h531d29 National Science Foundation, 2046768 National Institute of Amazonian Research, https://ror.org/01xe86309 Ministry of Business, Innovation and Employment Universidad de Panamá, https://ror.org/0070j0q91 Ecopetrol (Colombia), 135-2009 Dutch Research Council, NWO-VI.Veni.192.027 Ministerio de Economía, Comercio y Empresa, CGL2013-46808-R Ministerio de Ciencia, Tecnología e Innovación, https://ror.org/03fd5ne08, Convocatoria 860

The present study examined the wood properties of Pterocarpus erinaceus, a species found in West Africa's Guineo-Sudanian and Sudano-Sahelian zones. The primarily focus was on wood fiber properties, which serve as indicators of cambial growth and the transition between juvenile and mature wood. The aim was to analyze the factors contributing to the variability of the wood fiber properties. Specifically, it examined the effect of cambial age and ecological factors on fiber properties and analyzed how the fiber properties influence density and dimensional characteristics of the wood. Measurements of fiber properties were obtained from 451 specimens collected in the Guinean, Sudanian, and Sahelian zones in Burkina Faso, Niger, and Togo. The results indicate significant variations in average fiber parameters among the three climatic zones. This variability leads to an increase in the length, width, and thickness of the fibers along the north-south decreasing rainfall gradient. However, no noteworthy correlations were observed between cambial age and fiber properties, posing challenges in distinguishing between juvenile and adult wood. In terms of correlation, the analysis shows that fiber length has no effect on physical properties, but fiber width significantly influences basic density, wood shrinkage, and the fiber saturation point (FSP).

Abstract Pterocarpus erinaceus Poir. is a species found in the Guineo-Sudanian and Sudano-Sahelian zones, known for its high-quality wood. However, there is limited understanding of its forestry and technological properties, which currently prevents its inclusion in reforestation programs. The objective of this study was to analyze the factors influencing heartwood variability in P. erinaceus. The study was conducted on 40 wood cores collected from three climatic zones (Sudanian, Guinean, and Sahelian). The results revealed significant variation in the percentage of heartwood across agroecological zones, with the highest percentage observed in the Sahelian zone (90.16 ± 3.21%) and the lowest in the Guinean zone (75.20 ± 6.85%). The study also found a significant correlation between the percentage of heartwood and tree diameter, as well as between the percentage of heartwood and tree age. Duraminization initiation was found to occur early in trees from the Guinean (14 years) and Sudanian (16 years) zones, while in the Sahelian zone, it starts at the age of 21 years. The results also reveal a decrease in duraminization rate with age, regardless of climatic zone.

Grenadilla wood (Dalbergia melanoxylon Guill. & Perr.) is a hardwood species found in Tanzania, Mozambique, and other countries in the tropical part of Africa, especially in the Eastern-Central region. Thanks to its high density and good hygroscopic stability, it is used in the making of various musical instruments and fine furniture. Due to the scarcity of published data on this wood species, more studies on its properties are needed to improve its processing and use, and even to search for sustainable alternative materials as its trade is increasingly limited by new regulations. This work is focused on the hygromechanical properties, which hold an important role in the applications of this wood: diffusion coefficients and adsorption–desorption curve (both measured at $$T = 20\,^{\circ }\hbox {C}$$), swelling–shrinkage coefficients and full orthotropic elastic constants using an ultrasonic method. Results show that grenadilla wood possesses small water diffusion coefficients (from $$1.54\pm 0.49\times 10^{-7}\,\hbox {cm}^2/\hbox {s}$$ in T direction to $$4.58\pm 0.84\times 10^{-7}\,\hbox {cm}^{2}/\hbox {s}$$ in L direction), which is probably related to its high density ($$1250.0\pm 26.2\,\hbox {kg}/\hbox {m}^{2}$$); unique equilibrium moisture content (sorption) curve with a lower fiber saturation point ($$0.173\pm 0.003$$); smaller swelling–shrinkage coefficients ($$0.20\pm 0.03$$ and $$0.32\pm 0.05$$ in T and R directions, respectively); and elastic constants lower in the longitudinal direction ($$15.56\pm 1.79$$ GPa) and higher in the transverse ones ($$5.10\pm 0.46$$ GPa and $$4.05\pm 0.35$$ GPa in R and T directions, respectively) than what could be expected with a standard model based on the density only. Several explanations were described here, from the effects of a high extractive content to the possibility of a high microfibril and/or fiber angle.

Abstract Pterocarpus erinaceus (Poir) is currently the most exploited and threatened spontaneous tree species in the Guinean-Sudanian and Sudano-Sahelian zones in West Africa. This work analyzed the density and color parameters of P. erinaceus wood in the phytogeographic zones (Sudanian, Guinean and Sahelian) in three countries in West Africa (Togo, Burkina Faso and Niger). The results obtained by studying 451 specimens taken from 95 trees showed significant differences in basic density and color parameter values (P < 0.001) based on phytogeographic zones. Individual tree samples from the Sahelian zone were denser (780 ± 63 kg · m − 3), darker (L* = 48.3 ± 0.6) and redder (a* = 8.2 ± 2) than those in the Guinean zone (basic density = 684 ± 53 kg · m−3; L* = 59.7 ± 0.5; a* = 6 ± 0.2) and the Sudanian zone (basic density = 725 ± 70 kg · m−3; L* = 53.7 ± 0.40; a* = 7.30 ± 0.2). At intra-tree scale, the results did not show a significant variation of basic density according to the number of rings counted from the pith (P > 0.05). This indicated that the age of the trees has little influence on the basic density of P. erinaceus wood.

Acacia auriculiformis is increasingly used as timber in Benin, while little is known about its wood characteristics and the factors affecting such characteristics in the country. The determination of these characteristics is necessary for understanding the functioning of this species and its uses. The aim of this study was to evaluate anatomical and physico-mechanical properties of Acacia auriculiformis in relation to age and soil type in Benin, West Africa. Nine different age plantations (young 6–7 years old, middle-aged 9–11 years old, aged 15–29 years old) were sampled on three soil types (ferruginous, sandy and vertisol). In total, 30 trees were felled for determination of vessel diameter and vessel frequency from pith to bark, basic density, density at 12% moisture content, tangential and radial shrinkages, fiber saturation point, anisotropy of shrinkage, modulus of elasticity, compression strength, and bending strength. Age is the main factor influencing the physico-mechanical characteristics of the species and Acacia auriculiformis could be exploited at 15 years old for use as timber. Still, a high deformation ratio is noted on ferruginous soil. Besides, wood density is negatively correlated with anisotropy of shrinkage, which is an asset for the use of high density wood for structures. In contrast, the parameters of the vessels are weakly correlated with wood density. Further studies are necessary to understand the densification process of Acacia auriculiformis wood in order to optimize the production of high-density wood of the species, which is important for the use of wood as timber.

Les bois employes en facture instrumentale recouvrent une large diversite, selon les fonctions (familles et parties d’instruments) considerees, mais aussi selon les cultures (historiques et geographiques), et selon les preferences propres a chaque culture, voire a chaque artisan. Ces choix de bois font appel a un large eventail de parametres, allant de la disponibilite des especes, a des criteres physiques, mecaniques et « acoustiques » tres exigeants, en passant par des parametres de « travaillabilite » et de « sensorialite » des bois. Mais de nombreux bois actuellement preferes en facture instrumentale viennent d’especes en voie de rarefaction. La multiplicite des criteres et implications des choix de bois en facture instrumentale en fait une sorte de « miroir a facettes » de la crise actuelle de biodiversite. Cette presentation vise a proposer un etat de l’art des proprietes materielles, notamment vibro-mecaniques, de bois importants en facture instrumentale mais en voie de rarefaction. Un accent particulier sera porte sur les Palissandres (genre Dalbergia et genres botaniques proches). En depit de l’importance emblematique de ces bois, tres peu de donnees sont actuellement disponibles dans la litterature sur les proprietes de ces bois. Apres avoir etabli la synthese de ces informations existantes, de nouveaux resultats sur la diversite des proprietes vibratoires des Palissandres seront presentes. Ces resultats sont bases d’une part sur des echantillons collectes grâce a la participation active de plusieurs luthiers Francais, d’autre part sur une analyse des echantillons de la xylotheque (collection botanique de bois) de l’Unite BioWooEB, cette xylotheque du CIRAD-Montpellier etant l’une des plus riches collections de bois dans le monde. Ce travail fait partie d’un projet en cours, international et inter-metiers, visant a comprendre les specificites des Palissandres.

Some relationships between ray proportions, strength and shrinkage properties and basic density in hardwood species were highlighted. A better understanding of their relationships caused by the variation in moisture content in the hygroscopic domain could be a key factor in determining of wood stability properties and to determine the choice of a specific wood species according to its service life condition. The objectives of this study were (i) to determine the physical properties of various ring porous wood species (ii) and to evaluate the influence of wood rays (according to their proportions and volume) on physical properties of wood and more particularly on the Transverse Anisotropy Ratio for Shrinkage (TARS). This study focused on four ring-porous hardwood species; Castanea sativa, Quercus canariensis, Quercus petraea and Quercus robur, differing by the presence and abundance of their multiseriate wood rays. Basic densities, tangential shrinkages, radial shrinkages and the TARS of heartwood and sapwood from each wood species were determined. Wood-rays' proportions and volume were measured by the image analysis method, and their influence on the last three shrinkages was investigated. A significant correlation between wood ray proportions, wood shrinkage values and basic density was observed.

Timber grading is an essential step into the value process to determine wood usability for structural uses. It requires well-described characteristics obtained easily by taking non-destructive measurements to quantify reliable indicators of mechanical properties. In this paper we present an approach based on both timber scale and clear-wood scale measurements using the case of Mountain pine (Pinus uncinata). An important experimental plan have been performed from collected trees of French and Spain Pyrenean regions allowing significantly the use of inter-correlations between measurements. The physical properties of clear wood present an important adaptation of tree growth condition with a lower modulus of elasticity as a consequence of microstructure at cell-wall level but a conventional modulus or rupture in bending for pines. However, the results on timber presents an important the difference between visual and machine grading for this species in view of mechanical properties considered. The results obtained also show possible improvement and limitations of current regulation in the grading mountain pine timber for structural use.

La xylothèque du Cirad est composée d’échantillons provenant de 34 395 arbres issus de 123 pays, appartenant à 235 familles, 2 160 genres et 8 385 espèces (dont 60 % sont représentées par plus d’un spécimen par arbre). Les espèces d’Afrique, d’Asie et d’Amérique représentent 85 % de la collection. Une description botanique des familles, genres et espèces les plus représentés a été faite dans les dix régions géographiques pour lesquelles il y a suffisamment d’échantillons (plus de 1 000). Ces régions comprennent neuf régions tropicales ou subtropicales et une grande entité appelée « Climat Froid du Nord » (NCC), qui couvre tous les pays de l’hémisphère nord ayant une saison froide marquée (climats boréal, alpin tempéré et méditerranéen). Les neuf régions tropicales et subtropicales ont plus ou moins les mêmes familles dominantes, mais différents genres dominants alors que les familles dominantes dans l’entité NCC diffèrent largement. La collection est décrite dans une base de données spécifique : échantillons de bois, sections et photographies avec leurs noms et provenance. La densité a été mesurée pour les deux tiers des spécimens (6 750 espèces). Dans l’ensemble, les valeurs de la densité ont une distribution presque normale dans une plage de 0,04 à 1,36, avec une médiane de 0,72 et un coefficient de variation (CV) de 28 %. La différence entre régions, quant à la distribution de la densité, est assez faible (valeurs moyennes variant de 0,66 à 0,76) avec un CV systématiquement élevé (26 % à 32 %). En examinant les familles, genres et espèces les mieux représentés, le CV moyen pour les familles (26 %) est similaire à celui des régions et beaucoup plus bas pour les genres (18 %) et espèces (13 %). L’éventail des densités augmente de la famille au genre et à l’espèce (0,53 à 0,86, 0,46 à 0,95, 0,23 à 1,07 respectivement). Dans l’article, les différents usages actuels et potentiels de la xylothèque sont discutés.

Sycamore maple (Acer pseudoplatanus L.) is a wood species particularly known for its wavy grain figure and its high-value utilization among luthiers and craftsmen for making musical instruments or furniture. In this study, the anatomical and physical-acoustical characteristics of its wood, taken from different trees with various surface figures, were characterized. Vibrational mechanical measurements were conducted taking into account radial and longitudinal directions and local variations. Waviness parameters were quantified on split blocks, and anatomical properties such as microfibril angle and ray dimensions were measured using light microscopy. Results provide a complete dataset on the properties of sycamore maple along a gradient of the wavy figure. Through statistical analysis, significant correlations were found between the measured parameters, particularly between the waviness and microfibril angle, and between the anatomical features and the specific modulus of elasticity and damping by internal friction of the wood in the longitudinal direction. Anisotropy was found to be very low but was not satisfactorily explained by the studied anatomical features. Prospects for future studies on the wavy figure are discussed.

Premise of the study Basic wood density is an important ecological trait for woody plants. It is used to characterize species performance and fitness in community ecology, and to compute tree and forest biomass in carbon cycle studies. While wood density has been historically measured at 12% moisture, it is convenient for ecological purposes to convert this measure to basic wood density, i.e. the ratio of dry mass over green volume. Basic wood density can then be used to compute tree dry biomass from living tree volume. Methods Here, we derive a new, exact formula to compute the basic wood density D b from the density at moisture content w denoted D w , the fibre saturation point S , and the volumetric shrinkage coefficient R . We estimated a new conversion factor using a global wood technology database where values to use this formula are available for 4022 trees collected in 64 countries (mostly tropical) and representing 872 species. Key results We show that previous conversion factors used to convert densities at 12% moisture into basic wood densities are inconsistent. Based on theory and data, we found that basic wood density could be inferred from the density at 12% moisture using the following formula: D b = 0.828 D 122 . This value of 0.828 provides basic wood density estimates 4-5% smaller than values inferred from previous conversion factors. Conclusions This new conversion factor should be used to derive basic wood densities in global wood density databases. This would prevent overestimating global forest carbon stocks and allow predicting better tree species community dynamics from wood density.