Pleating is an optimal way to increase bendability of wood used in diverse industrial applications. It results in the excessive buckling of cell walls and modifications of constitutive polymers. However, thoughtful understanding of the physical–chemical mechanisms of that modification process is very limited. The main purpose of the present study was to identify changes in functional groups of wood polymers induced by longitudinal compression. Four types of wood samples prepared from beech and sessile oak (untreated, steamed, longitudinally compressed and fixated for 1 min as well as longitudinally compressed and fixated for 18 h) were assessed by infrared spectroscopy. The spectra interpretation revealed that changes can be observed in hydroxyl as well as in carbon–oxygen single and carbon-hydrogen functional groups of polysaccharides and lignin. Beech wood seems to be more susceptible to investigated modification processes as compared to oak. Detailed interpretation of infrared spectra allows identification of changes in the hygroscopicity of wood as well as alterations in the linkage between structural elements in the polymer matrix of wood induced by the applied treatments.Graphic Abstract

Since the properties of wood significantly change with its moisture content, it is important to know the effect of different moisture conditions on wood. A brief summary is provided on this topic in the first part of this article. The compression along the wood grain is a modification resulting in better pliability. The moisture dependence of mechanical properties of longitudinally compressed wood is not known yet. For this purpose, the results in this article are considered as basic research results. Bending- and compression tests on beech specimens compressed longitudinally by 20% were carried out at different moisture contents. Changing moisture content has almost no significant effect on the modulus of rupture of wood that has been longitudinally compressed, compared to the sensitivity to changes in moisture content of untreated wood. However, the effect of moisture content on the change of bending modulus of elasticity, compressive strength parallel to the grain and bendability coefficient diverges significantly. As a result of these changes, there is a great difference in the pliability with different moisture contents of treated wood. For the best pliability during bending, the moisture content of longitudinally compressed wood must be close to its fiber saturation point.

One of the goals of the European Union’s agroforestry plans is to alleviate the shortage of timber in Europe caused by the growing demand for hardwoods and the declining import of tropical timber. The study shows which tree species can be considered in agroforestry systems in Europe, and which of them can be used as raw material for the wood industry and what quality of wood can be produced in agroforestry systems. Since 2005, the European Union has been officially encouraging farmers to plant the crops in an agroforestry system and parallel try to produce trunks for high quality timber. By analysing the current economic developments of the European Union, especially Horizon 2020, our study provides an overview of what can be expected by the participants of the agroforestry sector and the related primary wood industry in the European Union now and in the future. In addition to the distribution analysis, indices describing projects have also been created. Rank correlation was used to examine the relationship between them. Possible decision mechanisms were also outlined using a custom-built expert software system.

Longitudinal compression induces changes in wood tissue resulting in better bendability. The main purpose of the present study is to identify the changes occurring at the microscopic level. Air-dried oak wood samples (Quercus petraea (Matt.) Liebl.) exposed to a thermo-hydro-mechanical treatment—combined with different longitudinal compression and relaxation treatments—were subjected to micromechanical (nanoindentation) and ultrastructural (scanning electron microscopy, atomic force microscopy) analyses at the wood cell wall level. The comparison of the various methods of treatments shows that the secondary cell wall S2 hardness decreased by 6% as a result of the compression and by 12%, when combined with a long relaxation period. Cell wall indentation modulus decreased by 25% and 51%, respectively. Relative elastic deformation work increased at the expense of plastic deformation work, while the relative proportion of viscoelastic work remained unchanged. Atomic force microscopic images revealed distinct disorientation of the normally straight microfibrils as a result of longitudinal compression, which was attributed to cause the weakening of the cell wall. The results indicate that changes at the ultra-structural level of the wood cell wall contributed to the changes in the macromechanical properties (for example modulus of elasticity and bendability) already reported previously, of the treated wood samples.

Among fast-growing wood species, poplars (Populus spp.) can be grown well. Thanks to their valuable wood, they also play an important role in the world. In Europe, regarding poplar forest areas, Hungary is ranked second, where the territorial proportion of poplars has not changed in the past ten years, and currently, two-thirds of them are constituted by two species. The proportion of grey poplar (P. × canescens) is 42%, while the proportion of ’Pannonia’ hybrid (P. × euramericana cv. Pannonia) is 22%. With regard to gross wood production, they are second after black locust (Robinia pseudoacacia), and their standing tree volume is significant for up to 30 years of age. The average age of hybrid poplars is 21 years, while that of the natives is 26 years. Its wood is used by the packaging industry (pallets and boxes) and the furniture industry (700,000 m³), the plywood industry (200,000 m³), and the fiber industry (300,000 m³), but it is also an important source for energetic purposes (150,000 m³).

The question of the hybrid walnut (Juglans × intermedia Carr.) is still under debate in the Central European region. There is not simply just an underutilization, rather, even the existence of these hybrid forms is not broadly accepted. On the contrary, there is an intensive cross-breeding activity in the western part of Europe resulting in commercially available hybrid clones. In Hungary, several individuals have been reported with intermediate morphology from different old black walnut plantations. Due to the lacking information, a preliminary study was conducted in order to prove the difference of these selected trees and to test the hybrid state. For this purpose, DNA fingerprinting was used by applying 13 simple sequence repeat (SSR) markers for the identification of 22 hybrid genotypes selected from one study plot. A comparative analysis with a reference sample set of the ‘parental’ species and other known hybrids was performed as well. The genetic analysis resulted distinct, unique genotypes for all of the samples. Based on the genetic pattern, the analyzed hybrid group was clearly distinguishable from the other two walnut groups. The result of this study also highlights the hidden potential in walnut breeding in the Central European region. Future concepts concerning hybrid walnut utilization in plantation forestry, agroforestry or as breeding material are also discussed.