Juan Guo

Understanding how anatomy shapes wood mechanics is essential for grading and breeding. This study develop an interpretable-SHAP-based framework providing the first conditionally independent decomposition of anatomical effects on Chinese fir ( Cunninghamia lanceolata ) performance. To mitigate data scarcity, synthetic-data generated by three generative models were evaluated for correlation, distribution and prediction. Five machine-learning models were trained on synthetic data to predict modulus of elasticity (MOE), modulus of rupture (MOR), and compressive strength parallel to grain (CSP). All generative methods produced realistic data, with Gaussian Copula performing best. The best accuracy was achieved by CopulaGAN–XGBoost (MOE, 75 %), Gaussian Copula–AdaBoost (MOR, 80 %), and Gaussian Copula–Random Forest (CSP, 91 %), outperforming models trained on real data (58 %, 64 %, 68 %). SHAP analysis identified tracheid length (15.6 %, 6.0 %, 8.3 %), wall thickness (13.8 %, 12.6 %, 7.5 %), and microfibril angle (3.4 %, 2.7 %, 4.5 %) as key traits, with microfibril angle showing the strongest interactions. Latewood versus earlywood contributions were 24.1 % versus 16.7 % (MOE), 16.6 % versus 39.9 % (MOR), and 18.1 % versus 28.8 % (CSP). Density was the most influential trait: strength (MOR, CSP) was driven by density and earlywood traits, while stiffness (MOE) depended on density and overall anatomy. These findings provide interpretable guidance for wood quality assessment, material grading and plantation improvement.

Summary: Understanding the radial anatomical variation and determining the transition between juvenile and mature wood is crucial for enhancing harvesting efficiency and resource utilisation of Pinus elliottii . In this study, two slash pine half-sib families, A04 and A05 less investigated, were selected to study the radial variation of wood anatomical characteristics, i.e. annual ring width, latewood ratio, tracheid length, tracheid length-to-width ratio, double wall thickness, and wall-to-lumen ratio. Specifically, annual ring width decreased from pith to bark, whereas latewood ratio, tracheid length and tracheid length-to-width ratio both of earlywood and latewood, double wall thickness and wall-to-lumen ratio of latewood increased. Moreover, annual ring width, latewood ratio, tracheid length and tracheid length-to-width ratio both of earlywood and latewood, and wall-to-lumen ratio of earlywood were identified as suitable for distinguishing juvenile from mature wood. Additionally, the double wall thickness of latewood proved effective for demarcation in A05. Nevertheless, results revealed that double wall thickness of both earlywood and latewood, as well as wall-to-lumen ratio of latewood, were insensitive indicators for demarcation in A04. Similarly, the double wall thickness of earlywood and the wall-to-lumen ratio of latewood were not sensitive to the demarcation between juvenile and mature wood in A05. Furthermore, the transition from juvenile to mature wood of two half-sib families was evaluated using a segmented regression model and a cubic polynomial third-order regression model. Distinct maturation patterns illustrated A04 exhibited juvenile wood formation during the period of years from 2 to 10, followed by a transitional period from 10 to 15 years before reaching maturity from 15 to 18 years, while A05 demonstrated different development with the transition from 8 to 11 years. Furthermore, a third-order polynomial regression model was fitted for each anatomical trait within distinct growth stages. Systematic anatomical characteristics and determination of juvenile and mature wood constitute critical evidence for guiding family selection in silviculture and optimising processing parameters in wood industries.

Carbon fraction (CF) of trees is essential for quantifying forest carbon (C) stocks. Considerable attention has been paid to CF variations at various levels with the exception of inter- and intra-growth rings. Herein, the inter- and intra-growth ring variation of CF in Pinus tabuliformis was investigated. Elemental analysis was performed to obtain CF values of the earlywood and latewood in each growth ring of the xylem. Patterns of CF variation at the growth ring level were evaluated using mixed-effect models. The results showed that latewood CF, 50.6 %, was significantly higher than earlywood CF, 49.9 % (p < 0.01). In particular, inter-growth ring variations of CF differed between heartwood and sapwood, as well as between juvenile wood and mature wood. CF values decreased nonlinearly with cambium age toward the heartwood or juvenile wood, with estimated least-squares means of 50.4 % and 51.8 %, respectively. While CF values were almost unaltered in sapwood, and slightly decreased in mature wood, with estimated least-squares means of 50.0 % and 50.2 %, respectively. It indicates that patterns of CF variation between juvenile wood and mature wood are important to estimate the C stock of P. tabuliformis. This research provides insights into C uptake dynamics to support forest management and wood utilization.

Main conclusion Spatial organization and connectivity of wood rays in Pinus massoniana was comprehensively viewed and regarded as anatomical adaptions to ensure the properties of rays in xylem. Abstract Spatial organization and connectivity of wood rays are essential for understanding the wood hierarchical architecture, but the spatial information is ambiguous due to small cell size. Herein, 3D visualization of rays in Pinus massoniana was performed using high-resolution μCT. We found brick-shaped rays were 6.5% in volume fractions, nearly twice the area fractions estimated by 2D levels. Uniseriate rays became taller and wider during the transition from earlywood to latewood, which was mainly contributed from the height increment of ray tracheids and widened ray parenchyma cells. Furthermore, both volume and surface area of ray parenchyma cells were larger than ray tracheids, so ray parenchyma took a higher proportion in rays. Moreover, three different types of pits for connectivity were segmented and revealed. Pits in both axial tracheids and ray tracheids were bordered, but the pit volume and pit aperture of earlywood axial tracheids were almost tenfold and over fourfold larger than ray tracheids. Contrarily, cross-field pits between ray parenchyma and axial tracheids were window-like with the principal axis of 31.0 μm, but its pit volume was approximately one-third of axial tracheids. Additionally, spatial organization of rays and axial resin canal was analyzed by a curved surface reformation tool, providing the first evidence of rays close to epithelial cells inward through the resin canal. Epithelial cells had various morphologies and large variations in cell size. Our results give new insights into the organization of radial system of xylem, especially the connectivity of rays with adjacent cells.

Studying waterlogged archaeological wood moisture characteristics can provide strong support for the safe dehydration and preservation of waterlogged wooden artifacts. Herein, six waterlogged archaeological wood samples with moisture contents of 154%–968% chosen from two ancient Chinese shipwrecks, Nanhai No. 1 and Changjiangkou No. 2, and six non-degraded modern wood samples of the relevant corresponding species were selected to study the moisture characteristics by low-temperature nuclear magnetic resonance (NMR) and the dynamic sorption of water vapor (DVS). It was found that the six waterlogged archaeological wood samples exhibited three deterioration states: slightly, moderately, and seriously deteriorated. Wood deterioration caused significantly increased fiber saturation point (FSP) values for waterlogged archaeological wood. This is mainly owing to changes in the pore size distribution of cell walls. Moreover, NMR is more accurate than DVS in obtaining FSP for severely degraded samples. Additionally, moisture content was positively associated with wood deterioration. Maximum water content (MWC), free water content, and bound water content exhibited an exponential relationship with the basic density (BD). The contribution of bound water in waterlogged archaeological wood was less than that of modern wood and decreased with deterioration.

Wood is an anisotropic material, the mechanical properties of which are strongly influenced by its microstructure. In wood, grain compression strength and modulus are the weakest perpendicular to the grain compared to other grain directions. FE (finite element) models have been developed to investigate the mechanical properties of wood under transverse compression. However, almost all existing models were deterministic. Thus, the variations of geometry of the cellular structure were not considered, and the statistical characteristic of the mechanical property was not involved. This study aimed to develop an approach to investigate the compression property of wood in a statistical sense by considering the irregular geometry of wood cells. First, the mechanical properties of wood under radial perpendicular to grain compression was experimentally investigated, then the statistical characteristic of cell geometry was extracted from test data. Finally, the mechanical property of wood was investigated using the finite element method in combination with the Monte Carlo Simulation (MCS) techniques using randomly generated FE models. By parameter sensitivity analysis, it was found that the occurrence of the yield points was caused by the bending or buckling of the earlywood axial tracheid cell wall in the tangential direction. The MCS-based stochastic FE analysis was revealed as an interesting approach for assessing the micro-mechanical performance of wood and in assisting in understanding the mechanical behavior of wood based on its hierarchical structure.

Ray traits affect secondary xylem development and wood properties. Pinus massonia and Cunninghamia lanceolata, commercially important timber species, were chosen to study the differences in wood ray traits of juvenile versus mature wood. Seven ray traits, i.e., percentage of rays, ray spacing, ray number, uniseriate ray height, fusiform ray height, ray parenchyma cell length and ray tracheid length, as well as eight wood axial tissue traits, were investigated quantitatively. Intraspecific variations in ray traits and axial tissue traits between juvenile wood and mature wood were displayed in violin plots. The results showed that anatomical differences between juvenile wood and mature wood were significant for both ray traits and axial tissue traits. Juvenile wood generally possessed the larger percentage of rays, higher ray spacing and ray number, smaller ray height and shorter ray cells than mature wood. A positive correlation was present between the ray parenchyma cell length and ray tracheid length. Negative correlations of the ray number and ray spacing with uniseriate ray height were found. Additionally, the axial tracheid cell wall thickness all had Pearson’s correlations with ray spacing, ray number and ray parenchyma cell length.

Evaluating the deterioration state of archeological wood is obligatory before the preservation of archeological wooden artifacts. Herein, a nondestructive, accurate, and rapid methodology is first developed via direct analysis in real time-mass spectrometry (DART-MS) with chemometrics to classify archeological wood and recent wood into 3 groups according to their deterioration states. As water in wooden artifacts probably affected the ion fragmentation process during DART-MS, ions responsible for evaluating the deterioration state were separately screened toward waterlogged archeological wood and dried archeological wood by partial least-squares discriminant analysis (PLS-DA). The well-defined separation of severely decayed archeological wood, moderately decayed archeological wood and recent wood was revealed in PLS-DA models. Twenty and 27 wood fragment ions were further screened as key variables to evaluate the deterioration state of waterlogged archeological wood and dried archeological wood, respectively. They were tentatively identified as ions of lignin monomeric compositions, lignin dimers, lignin trimers, and oligosaccharides. Results strongly suggested that differences in the structure and relative abundances of wood cell wall components accounts for the evaluation of deterioration state by DART-MS coupled to chemometrics. PLS-DA models provided R²Y = 0.836, Q² = 0.817, and R²Y = 0.754, Q² = 0.682 were then established separately using mass spectral fingerprints of respective potential predictive wood fragment ions. Furthermore, archeological woods, consisting of Castanopsis, Quercus, Idesia, Populus, and Cunninghamia species and with an average MWC range of 103–465%, were used as an external validation set and evaluated with the methodology developed herein and the MWC criteria. Results showed that DART-MS coupled to chemometrics could accurately predict the inhomogeneous deterioration states of archeological wooden artifacts and avoid the interference of inorganic deposits, in comparison with the MWC criteria.