Volume 78, Issue 3

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.

A lignin model oligomer with only β- O -4 linkages and a selectively deuterium-labelled methoxy group at the phenolic terminal units was synthesised to clarify the behaviour of the phenolic end of oligolignols. First, t- butoxycarbonylmethyl vanillin was synthesised and oligomerised by nucleophilic addition, a known method. The terminal of the oligomers was then subjected to nucleophilic addition to [3-OCD 3 ]benzyl vanillin to achieve selective labelling of the terminal units. A deuterium-labelled lignin model oligomer (D-LM) was obtained through debenzylation and subsequent reduction. The results of thioacidolysis after methylation revealed that the degree of polymerisation was about five, and the deuterium-labelled phenylpropane unit was located only at the phenolic terminal moiety.

Resin production in wood tissues is a regular feature of pine wood species, including southern pine. High resin contents of southern pine wood may increase wood resistance against decay fungi. The current study investigated the effect of resin contents in southern pine wood on decay resistance by exposing non-extracted heartwood, mixed wood (sapwood + heartwood), and sapwood blocks with varying resin content to brown rot, Fomitopsis ostreiformis in a laboratory decay test. Matching blocks of each wood type were successively extracted in a Soxhlet using three solvents to determine resin content and were exposed to decay fungus in parallel. Results showed that mass losses in non-extracted heartwood and mixed wood depended on resin content levels, and very shallow or no mass losses were observed in blocks containing more than 31 % resin content. Sapwood experienced high mass losses, but the presence of resinous extractives significantly increased the decay resistance. All solvent-extracted blocks experienced high mass loss (53–55 %). Scanning electron microscopy showed that penetration of brown rot hyphae and cell damage depended on the resin contents of blocks. Most of the identified compounds through GC-MS belonged to oleoresins, among which monoterpene hydrocarbons, oxygenated monoterpenoids, and sesquiterpenes were more abundant in heartwood than sapwood.

The time domain nuclear magnetic resonance (TD-NMR) technique was employed to distinguish various water states, and the moisture migration during Elm wood ( Ulmus rubra ) heartwood vacuum drying was quantitatively analyzed. The transverse relaxation time (T2) was employed to establish the correlation between drying time and moisture migration. Additionally, the longitudinal relaxation time (T1) was utilized to identify two types of water states within the cell wall: OH bound water (B-water) and more freely bound water (C-water). Meanwhile, the changes in these two types of bound water during the drying were investigated. The results demonstrated an exponential decrease in the content of OH bound water and more freely bound water with drying time. OH bound water within the cell wall predominated, with only a small portion of more freely bound water experiencing migration loss when the moisture content (MC) dropped below 20 %. Furthermore, OH bound water exhibited higher migration rate compared to more freely bound water at 10–20 % MC, while the motion of OH bound water molecules became highly restricted and stronger binding to cell walls than more freely bound water at a MC level of below 10 %. These findings yield a theoretical foundation and empirical support for optimizing drying methods.

The hygroscopic and moisture-dependent mechanical characteristics of small-leaved lime wood ( Tilia cordata ) were investigated experimentally. This study includes sorption, swelling and shrinkage experiments, as well as tension and compression tests in the three principal anatomical directions at four relative humidity levels. Four sample groups from trees of three different locations in Germany were used. The findings are comparable to those of earlier studies. The hygro-expansion anisotropy is relatively small. Young’s moduli at tension/compression decreased by about 52 %/64 % in radial, 19 %/48 % in tangential and 16 %/58 % in longitudinal direction for an increase of moisture content from 10 % (65 % RH) to 20 % (95 % RH). Tension strengths/compression yield stresses decreased by about 25 %/45 % in radial, 9 %/42 % in tangential, and 32 % (compression) in longitudinal direction, respectively. These parameters increased with an increasing density. Based on the mechanical tests, Young’s modulus, tension strength and compression yield stress were derived as density- and moisture-dependent material model parameters. Shear modulus and shear strength were estimated by a theoretical approach. The experimental and modelling study was accompanied by a literature survey on characteristics of lime wood relevant for hygro-mechanical material modelling.

In this study, the influence of “bear claw” or indented growth ring anatomical patterns on the vibro-mechanical behavior of spruce wood have been investigated, particularly in the context of utilizing these singularities/specific features for the construction of violins. By employing vibrometry and modal analysis followed by finite element model updating, the vibro-mechanical properties (specific stiffness in longitudinal (L) and radial (R) directions and shear LR plane, and associated damping) of the indented growth rings spruce were identified and implemented in a numerical model of a violin. Results have revealed a significant increase in specific moduli in R direction and LR plane and decrease in L direction of spruce wood in the presence of indented growth rings, therefore accompanied by a reduction in anisotropic elastic properties, in comparison to spruce without these patterns. These properties led to changes in violin dynamics, globally increasing resonance frequencies and changing the shape of the vibration modes. The simulated frequency response function of the violin at the bridge suggested a global shift of the admittance of the bridge toward higher frequencies. These results suggest a potential impact of indented growth rings of spruce on the acoustic properties of instruments.