Maks Merela

A single point NMR method for an instantaneous determination of the moisture content of wood

Abstract Nuclear magnetic resonance (NMR) enables an instantaneous determination of the proton density in liquids and is thus convenient for determining the moisture content (MC) of wood. We demonstrated that the MC of a wood sample can be determined instantaneously on the basis of its mass (m) and the amplitude of its NMR free-induction-decay (FID) signal. The measurement is based on the assumption that the only liquid in the wood is water and that the relationship between the amplitude of the FID signal (S) and the mass of the water (m w ) in the sample is linear, i.e., S=k m w +k′ (m-m w ), and can be precisely calibrated for a given NMR probe and NMR spectrometer setup (in our case k=105 AU g-1 and k/k′ =34). With the FID signal converted into the mass of water, the MC is calculated as: MC=(S-m k′)/(m k-S). After the initial calibration of the FID signal with respect to the content of water, the correctness of the method was verified on samples of different wood species with various MCs. The results confirmed that the proposed method is comparable in terms of accuracy and reliability to the gravimetric method, regardless of the species of wood. As the method is instantaneous, it might become the method of choice in applications where a short measurement time combined with a high accuracy is demanded.

MISSING AND DARK RINGS ASSOCIATED WITH DROUGHT IN PINUS HALEPENSIS

The responses of the vascular cambium and tracheid differentiation to extreme drought in Aleppo pine (Pinus halepensis Mill.) were investigated. The research focused on the drought year of 2005, in the primary study area at Maigmo (MAI) in southeastern Spain, with comparisons in Jarafuel (JAL) and Guardamar (GUA). The climate in this region is typically warm and dry with hot summers. Wood formation throughout the 2005 growing season was studied in transverse microtome sections and integrated with a retrospective dendrochronological analysis of crossdated increment cores collected in 2009. For most anatomical sections collected throughout the growing season at MAI, the vascular cambium appeared to be dormant as indicated by the low number of cells per radial file. Occasionally, immature xylem derivatives were observed during the growing season but without production of an annual ring. In increment cores collected at MAI, the 2005 position in the annual ring series contained either a narrow ring of both earlywood and latewood (47% of samples), a narrow ring of apparent latewood with no earlywood (13%), or a missing ring (50%). We introduce the term “dark ring” to refer to those annual rings of apparent latewood with no earlywood. For trees at JAL, the 2005 ring had below-average width and contained both earlywood and latewood. At GUA, the trees produced the widest 2005 ring of all three sites and mainly contained an intra-annual density fluctuation (IADF). The IADF was formed after cambial reactivation in the autumn. Although dark rings, IADFs, and especially missing rings complicate dendrochronological analysis, these anatomical features may provide an additional proxy record from which to infer climate variability and change in the past.

Three-dimensional in vivo magnetic resonance microscopy of beech (Fagus sylvatica L.) wood

Spatial structure and water distribution in branch tissues after mechanical injury were investigated in vivo by three-dimensional (3D) magnetic resonance (MR) microscopy. On a beech tree (Fagus sylvatica L.), transplanted in a portable pot, a branch was topped and then MR imaged. High-resolution 3D MR images revealed structures which could not be identified by conventional MR images or by light microscopy. MR measurements confirmed our assumption that moisture content is decreasing towards the wounded part of the branch. This indicates that quick moisture loss from mechanically wounded tissues represents the initial passive response of compromised tissue.

3D magnetic resonance microscopy of a wounded beech branch

Abstract The pruned part of a beech (Fagus sylvatica) branch was imaged by a 3D spin-echo magnetic resonance imaging (MRI) technique to visualize change in structure and water content in the tissues. Proton density-weighted MR images of intact tissues confirmed high moisture content (MC) associated with high MRI signal in the pith, xylem rays and earlywood vessels, as well as in the cambial zone with current annual xylem and phloem increment. MRI images derived from the 3D datasets showed a previously unreported moisture-related structural response of the beech branch to wounding. An extensive wound tissue with a high MRI signal at the wound edge was a conspicuous new structure clearly visualized by 3D MRI. MRI revealed that the xylem at the wound was dehydrated in a cone-shaped pattern extending approximately 4.5 mm deep into the branch. Dehydration was delimited from the underlying sound wood by a layer, corresponding to the reaction zone, of tissue with a high MRI signal and hence high moisture content. Moisture content of these reaction zones in beech determined by MRI were greater than in healthy wood by factors of 1.3–1.8. Accordingly, in the margins of wounded beech wood not only cell wall alterations can be observed, but also an intensive water accumulation, which is probably an integral part of the protective mechanism for the underlying sound wood.

Timing of False Ring Formation in Pinus halepensis and Arbutus unedo in Southern Italy: Outlook from an Analysis of Xylogenesis and Tree-Ring Chronologies

Mediterranean tree rings are characterized by intra-annual density fluctuations (IADFs) due to partly climate-driven cambial activity. IADFs are used as structural signals to gain information on relations between environmental conditions and eco-physiological processes during xylogenesis, with intra-annual resolution. To reach an unbiased synchronization of the IADF position within tree rings and seasonal fluctuations in environmental conditions, it is necessary to know the timing of cambial activity and wood formation, which are species- and site-specific processes. We applied the microcoring technique to analyze xylogenesis in Pinus halepensis and Arbutus unedo. To the best of our knowledge, this is the first attempt to study xylogenesis in a hardwood species forming frequent IADFs. Both species co-occur at a site in southern Italy characterized by a Mediterranean climate. To facilitate tree-ring dating and identification of IADFs, we performed traditional dendroecological analysis. We analyzed xylogenesis during summer, which is considered a constraint for xylogenesis and a trigger for IADF formation. We followed the different phases of cell development in the current wood increment with the aim of evaluating whether and which type of IADFs were formed. We additionally analyzed the same phases again in September and in winter to verify the possible formation of IADFs in fall and whether cell production and differentiation was completed by the end of the calendar year. Both species formed the same type of IADFs (earlywood-like cells within latewood), due to temporary growth restoration triggered by rain events during the period of summer drought. At the end of the calendar year, no cells in the phases of enlargement and secondary cell wall deposition occurred. A. unedo was more sensitive than P. halepensis because IADFs were formed earlier in the season and were more frequent in the tree-ring series. The dendro-anatomical approach, combining analysis of tree-ring series and of xylogenesis, helped to detect the period of IADF formation in the two species. Results are discussed in functional terms, highlighting the environmental conditions triggering IADFs, and also in methodological terms, evaluating the applicability of xylogenesis analysis in Mediterranean woods, especially when the formation of IADFs is not uniform around the stem.

Do variations in leaf phenology affect radial growth variations in Fagus sylvatica

We used a dendrochronological and leaf phenology network of European beech (Fagus sylvatica) in Slovenia, a transitional area between Mediterranean, Alpine and continental climatic regimes, for the period 1955–2007 to test whether year to year variations in leaf unfolding and canopy duration (i.e. time between leaf unfolding and colouring) influence radial growth (annual xylem production and tree ring widths) and if such influences are more pronounced at higher altitudes. We showed that variability in leaf phenology has no significant effect on variations in radial growth. The results are consistent in the entire region, irrespective of the climatic regime or altitude, although previous studies have shown that leaf phenology and tree ring variation depend on altitude. The lack of relationship between year to year variability in leaf phenology and radial growth may suggest that earlier leaf unfolding—as observed in a previous study—probably does not cause increased tree growth rates in beech in Slovenia.

Application of 3D magnetic resonance microscopy to the anatomy of woody tissues

We demonstrate the use of high-resolution three-dimensional magnetic resonance microscopy (3D MRM) for anatomical studies of woody tissues. Samples of normal and pathological structures in the branches of four tree species were imaged by 3D MRM immediately after removal from the tree, without additional tissue preparation. MRM data sets were displayed in 2D sections and in a 3D volume rendered mode. Good image contrasts between identical anatomical structures in different tree species suggest that 3D MRM may be a promising method in comparative wood anatomy. MRM can be used for general morphological observations, as well as for positioning and examination of a particular portion of tissue in the investigated object. This is demonstrated by examples of a needle trace within the xylem in Norway spruce and by localisation of the protection zone at the base of a dead branch in beech. Visualisation of a wound scar in beech demonstrates the efficiency of 3D MRM in revealing the spatial dimensions of any moisture-related structural defects within wood. It can provide relatively high and isotropic resolution, thus enabling non-destructive and accurate determination of the moisture content of any wood structure. High-resolution 3D MRM has great potential in studying the anatomy of woody plants due to the non-destructive nature of the technique, the simplicity of tissue preparation and very versatile information retrieval by choosing an appropriate MRM method and its parameter set.

Xylogenesis reveals the genesis and ecological signal of IADFs in Pinus pinea L. and Arbutus unedo L.

Background and Aims Mediterranean trees have patterns of cambial activity with one or more pauses per year, leading to intra-annual density fluctuations (IADFs) in tree rings. We analysed xylogenesis (January 2015-January 2016) in Pinus pinea L. and Arbutus unedo L., co-occurring at a site on Mt. Vesuvius (southern Italy), to identify the cambial productivity and timing of IADF formation. Methods Dendrochronological methods and quantitative wood anatomy were applied and enabled IADF identification and classification. Key Results We showed that cambium in P. pinea was productive throughout the calendar year. From January to March 2015, post-cambial (enlarging) earlywood-like tracheids were observed, which were similar to transition tracheids. The beginning of the tree ring was therefore not marked by a sharp boundary between latewood of the previous year and the new xylem produced. True earlywood tracheids were formed in April. L-IADFs were formed in autumn, with earlywood-like cells in latewood. In A. unedo, a double pause in cell production was observed, in summer and winter, leading to L-IADFs in autumn as well. Moreover, the formation of more than one IADF was observed in A. unedo. Conclusions Despite having completely different wood formation models and different life strategies, the production of earlywood, latewood and IADF cells was strongly controlled by climatic factors in the two species. Such cambial production patterns need to be taken into account in dendroecological studies to interpret climatic signals in wood from Mediterranean trees.

Palisandri in sorodniki iz rodu Dalbergia na seznamu CITES

The wood of rosewoods and palisanders from the botanical genus Dalbergia has a decorative coloured heartwood with dark streaks, high density and favourable wood properties, and thus is traditionally used and highly valued for prestige products and musical instruments. Among the most famous representatives of the genus are Brazilian rosewood (D. nigra) and Indian rosewood (D. latifolia). Due to its over-exploitation, Brazilian rosewood was put on the CITES list (Convention on International Trade and Endangered Species of Wild Fauna and Flora) in 1992 (Cites, 2018) as part of Appendix I, which lists the species threatened with extinction, and trade in these is generally prohibited. According to new CITES trade rules which came into effect at the beginning of 2017, the entire genus of Dalbergia (>250 species) has been put in Appendix II, which includes species not necessarily threatened with extinction, but in which trade must be controlled in order to avoid utilization incompatible with their survival. Due to these regulations, the correct identification of the wood is very important. Based on the use of relevant wood anatomical keys we present the 20 most important species of Dalbergia. We present and discuss the main wood anatomy features and questions related to identification of species belonging to the same genus. We present the importance of rosewoods for the production of musical instruments, as well as the problem of control and prevention of their illegal trade.

Lastnosti bukovine in njena raba / Properties of beechwood and its use

We present the structure as well as biological, physical and mechanical properties of European beech (Fagus sylvatica L.) wood in comparison with that of Norway spruce and selected hardwoods. Fine grain, high homogeneity, low anisotropy, medium to high density, favourable mechanical properties, machining, bonding, and finishing, as well as suitability for bending, are among the main advantages which enable wide use of beechwood. Large amounts of beechwood are currently used as fuel. However, for its optimal use, we should revitalize and increase the production of traditional and new semi-finished products like sawn timber, structural and decorative veneer, composite boards and products of chemical processing. In contrast, for energy purposes we should mainly use the residues from these wood-working procedures. According to the numerous favourable properties of beechwood and fairly good possibilities of increasing its durability, we should focus on the development of innovative products to increase its use for construction purposes in buildings.