Key message
Climate change is posing a considerable challenge to foresters. The intensity of required adaptive measures and the relevance of old-growth forests as benchmark for managed forests are ...debated. Forest managers need to make decisions on stand treatment that are based on climatological and biological parameters with high uncertainties. We provided the conceptual basis for adaptive forest management and provide a number of case studies that reflect the options and limitations of ways of coping with climate change. The examples are derived from the experience of the authors. We conclude that only few forest types are either not strongly affected by climate change or do not require immediate adaptations of forest management. Many productive forests have stand properties that are decisively shaped by past management decisions, such as tree species composition, age distribution, rotation period, and stand structure. Maintaining these properties under the influence of climate change requires continuous and even increasing efforts of forest managers.
This paper describes one of a series of studies carried out at the University of Bio-Bio in Chile with the objective of characterizing the response of Eucalyptus nitens to drying. The ultimate goal ...is to minimize collapse and internal intra-ring checking in the industrial drying of Eucalyptus nitens, which currently prevents the lumber manufacturing industry in Chile from producing a large number of commercial solid wood products from this species. This study focuses, however, on the drying conditions that have been shown in previous studies and are known in the industry to minimize collapse and internal intra-ring checking. For these conditions, this study reports the development of moisture content and internal strain profiles during drying. In addition, a simple diffusion model based on the concept of the effective diffusion coefficient was proposed to compare the drying rates in the radial and tangential directions. The results showed that the diffusion coefficient in the radial direction was approximately 50% higher than that in the tangential direction. Internal strains, on the other hand, developed approximately at the same time, regardless of the annual ring orientation. This indicates that it would be feasible to apply strain relief strategies simultaneously to all boards regardless of their annual ring orientation in order avoid internal intra-ring checking during pre-drying. This finding could be used as a benchmarking tool in the industrial drying for solid wood products of Eucalyptus nitens.
The connection between branch and trunk in a tree must be strong enough to transfer all loads acting on the branch, and it is well known that such branch-stem connections are indeed very strong. In ...this paper, X-ray computer tomography is employed to investigate the local fibre orientation in the close surrounding of a knot in a Norway spruce specimen to better understand the origins of the mechanical strength of the branch-trunk connection. First, a wood specimen containing an entire knot from pith to bark was imaged with a voxel size of 52 µm. Subsequently, smaller specimens were cut from this original specimen and imaged again with increasingly higher resolution over four levels. With the highest resolution level (2.6 µm voxel size), the tracheids with smallest lumen were successfully traced. The results revealed how the direction of the fibre paths that start below the knot curve around it as the paths progress upwards to the region just above the knot, where the paths divide into two: one set of paths integrating with the knot on its top side and the other set continuing up along the trunk. Fibres that integrate with the knot at its top follow paths just before they continue into the knot, with a radius of curvature of only about 1 mm in both vertical and horizontal directions. No abrupt change of fibre pattern between latewood and earlywood is observed; rather, a continuous change of fibre direction across annual layers can be seen. The detailed characterisation of the local fibre structure around the knot provides new data that can explain the remarkable strength of the branch-trunk connection.
Balsa (
Ochroma pyramidale
), which is the lowest density wood, is a useful species in various industries. In general, balsa can be divided into three types (low density: LD, middle density: MD, high ...density: HD). In this study, we classified the porosities of the three balsa types into through-pore porosity, blind-pore porosity, and closed-pore porosity. As a result, the total porosity of balsa showed a high positive (+) correlation with closed-pore porosity, but total porosity of balsa showed negative (−) correlations with blind-pore porosity and through-pore porosity. Such information can be useful when using balsa as a natural porous material.
Wood modification improves the properties of wood as a building material by altering the wood structure on a cellular level. This study investigated how dimensional changes of wood on a macroscopic ...scale are related to the cellular level chemical changes on the micron level after impregnation modification with melamine formaldehyde (MF) resin under different heat curing conditions. Our results showed that the curing conditions affected the polycondensation reactions and the morphological structure of the MF resin within the cell lumen. The diffusion of the resin into the cell wall was estimated based on the triazine ring vibration of melamine in the Raman spectrum at 950-990 cm
. Thereby, it was shown that macroscopic changes in wood dimensions do not provide a reliable estimate for the cell wall diffusion of the resin. The removal of cell wall constituents during the modification, which was facilitated by the alkaline pH of the impregnation solution, counterbalanced the cell wall bulking effect of the resin. This was particularly evident for wet cured samples, where diffusion of MF resin into the cell wall was observed by confocal Raman microscopy, despite a reduction in macroscopic wood dimensions.
Key message
Woody plants have salt-tolerant mechanisms similar to those developed by non-woody plants. Among others, compartmentalization of ions, production of compatible solutes, synthesis of ...specific proteins and metabolites, and induction of transcriptional factors are the most relevant. Woody plant-associated microbial interactions as well as naturally stress-adapted trees are resources that deserve to be deepened to fully understand the tolerance mechanisms.
Context
The high variability of salinity responses found in woody plants implies a high potentiality for germplasm selection and breeding. Salt tolerance mechanisms of plants are regulated by numerous genes, which control ion homeostasis, production of compatible solutes and specific proteins, and activation or repression of specific transcription factors. Despite the fact that numerous studies have been done on herbaceous model plants, knowledge about salt tolerance mechanisms in woody plants is still scarce.
Aims
The present review critically evaluates molecular control of salt tolerance mechanisms of woody plants, focusing on the regulation and compartmentalization of ions, production of compatible solutes, activation of transcription factors, and differential expression of stress response-related proteins, including omics-based approaches and the role of plant-microbial interactions. The potential identification of genes from naturally stress-adapted woody plants and the integration of the massive omics data are also discussed.
Conclusion
In woody plants, salt tolerance mechanisms seem not to diverge to those identified in non-woody plants. More comparative studies between woody and non-woody salt tolerance plants will be relevant to identify potential molecular mechanisms specifically developed for wood plants. In this sense, the activation of metabolic pathways and molecular networks by novel genetic engineering techniques is key to establish strategies to improve the salt tolerance in woody plant species and to contribute to more sustainable agricultural and forestry systems.
Text mining techniques provide valuable insights into research information across various fields. In this study, text mining was used to identify research trends in wood science from 2012 to 2022, ...with a focus on representative journals published in Korea and Japan. Abstracts from Journal of the Korean Wood Science and Technology (JKWST, 785 articles) and Journal of Wood Science (JWS, 812 articles) obtained from the SCOPUS database were analyzed in terms of the word frequency (specifically, term frequency-inverse document frequency) and co-occurrence network analysis. Both journals showed a significant occurrence of words related to the physical and mechanical properties of wood. Furthermore, words related to wood species native to each country and their respective timber industries frequently appeared in both journals. CLT was a common keyword in engineering wood materials in Korea and Japan. In addition, the keywords “MDF,” “MUF,” and “GFRP” were ranked in the top 50 in Korea. Research on wood anatomy was inferred to be more active in Japan than in Korea. Co-occurrence network analysis showed that words related to the physical and structural characteristics of wood were organically related to wood materials.
The effect of thermal modification (TM) on the chemistry, anatomy and mechanical properties of wood is often investigated using small clear samples. Little is known on the effect of growth-related ...and processing defects, such as knots and checks, on the bending strength and stiffness of thermally modified timber (TMT). Nine boards of Norway spruce with different combinations of knot types were used to study the combined effects of checks and knots on the bending behaviour of TMT. Digital image correlation (DIC) measurements on board surfaces at sites of knots subjected to bending allowed to study strain distribution and localise cracks prior to and after TM, and to monitor development of fracture (around knots) in TMT to failure. DIC confirmed that checking in knots was increased after TM compared to kiln-dried timber, specifically for intergrown knots and intergrown parts of encased knots. Effects appear local and do not affect board bending stiffness at these sites. Bending failure in TMT initiated mainly at knot interfaces or besides knots and fractures often propagated from checks. Scanning electron microscopy analyses of fracture surfaces confirmed this, and fractures were typically initiated around knots and at knot interfaces due to crack propagation along the grain in the longitudinal–radial plane (TL fracture) under mixed mode I and II loading, such that boards failed in simple tension like unmodified timber. Images of fracture surfaces at the ultrastructural level revealed details of the brittle behaviour of TM wood. This was especially apparent from the smooth appearance of transwall failure under mode I loading across the grain.
In this study, the combined effects of chemical (with tricine and bicine) and thermal treatments were investigated. The modifications which appeared in the wood structure were evaluated by infrared ...spectroscopy and chemometric methods (principal component analysis and hierarchical cluster analysis). After the treatment, about 6–7% of WPG was identified in treated samples, but further thermal treatment decreased the WPG to about 5%. The modifications appearing in the spectra were mostly related to increase of the intensities of the bands assigned to CO groups but also to N–H and C–N groups, with shifting of some bands to higher wavenumber values.
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•The combined effects of chemical and thermal treatment on soft and hardwood were evaluated.•The effectiveness of treatment was evaluated by infrared spectroscopy and chemometric methods.•The occurrence of the reactions between the functional groups from bicine and tricine and wood structure were identified.•Softwood samples were more susceptible to chemical/thermal modification than the hardwood samples.
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