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Highlights: [•] Thermal decomposition of corks from Quercus cerris and Quercus suber is similar. [•] Cork undergoes two exothermal reactions at approximately 313°C and 445°C. [•] Suberin has a key role in the thermal stability of corks. [•] Q. cerris cork granulates with phloem remains have potential for insulation. [•] Extractives contribute to shielding against heat-induced degradation. [ABSTRACT FROM AUTHOR]

Abstract: The current state-of-the-art of tree-ring analysis and densitometry is still mainly limited to two dimensions and mostly requires proper treatment of the surface of the samples. In this paper we elaborate on the potential of helical X-ray computed tomography for 3D tree-ring analysis. Microdensitometrical profiles are obtained by processing of the reconstructed volumes. Correction of the structure direction, taking into account the angle of growth rings and grain, results in very accurate microdensity and precise ring width measurements. Both a manual as well as an automated methodology is proposed here, of which the MATLAB© code is available. Examples are given for pine (Pinus sylvestris L.), oak (Quercus robur L.) and teak (Tectona grandis L.). In all, the methodologies applied here on the 3D volumes are useful for growth related studies, enabling a fast and non-destructive analysis. [Copyright &y& Elsevier]

X-ray scattering and microtomography (μCT) are useful techniques to reveal the structure of wood at the nano- and micrometer scales. The nanostructure of xylem in greenhouse-grown 2.5- to 3.5-month-old Populus tremula L. × tremuloides Michx. trees was characterized using wide-angle X-ray scattering (WAXS), and the cellular structure was investigated using μCT. For comparison, the nanostructure of wood in 2-year-old silver birch, Norway spruce and Scots pine saplings was determined. Based on the μCT results, the lengths of fiber lumina of the hybrid aspen saplings were shorter than any previous results on the lengths of wood fibers. The mean microfibril angles of the hybrid aspen saplings were significantly lower (8°-14°) than those of the birch, spruce and pine saplings (27°-35°) implicating that cellulose microfibrils were oriented nearly parallel to the cell axis in the young hybrid aspen saplings. Hybrid aspen saplings were found to contain tension wood based on the histochemical analysis and μCT images. However, typical tension wood properties, i.e. larger crystallite width and higher crystallinity than in normal wood, were detected only in a few hybrid aspen samples, while in most of the hybrid aspen saplings, the crystallite widths (3.0 ± 0.1 nm) and the crystallinities (30 ± 5 %) corresponded to those of normal wood. The deformations of cellulose crystallites were determined using WAXS in situ upon dehydration of the never-dried samples. In all the species studied, the cellulose unit cell dimension decreased and disorder of cellulose chains increased parallel to the chains upon drying. Also, the transverse disorder of chains increased in birch, spruce and pine, while no changes were detected in this direction in hybrid aspen. The crystallite widths and drying deformation results might indicate that the gelatinous layer has not fully developed in the young hybrid aspen saplings. [ABSTRACT FROM AUTHOR]

Context: Customers have limited tolerances for colour differences between oak wood elements in parquetry or furniture, whereas manufacturers are in need of an objective method to communicate possible differences in their products. Aims: This study is aimed at grading oak wood boards in objectively defined colour classes in correspondence with the visual assessment by an expert panel. Methods: First, the most suitable spectrophotometer for measurements approximating the perception of the human eye was selected. Then, three colour grading algorithms were evaluated: one based on the smallest distance towards the centre of the colour subspaces, the second using a classification tree and the last implementing the CIEDE2000 colour difference formula to determine tolerance ellipsoids. Results: Statistical analysis using a classification tree and CIEDE2000 tolerance ellipsoids classified the specimens in good accordance with visual assessment, with a 6 and 5 % misclassification, respectively. Conclusions: The colour grading methodology can be adapted to particular grading purposes and is proposed as a basis for development of an inline colour grading system to be added to commonly used defect detection scanners. [ABSTRACT FROM AUTHOR]

Background and Aims Teak forms xylem rings that potentially carry records of carbon sequestration and climate in the tropics. These records are only useful when the structural variations of tree rings and their periodicity of formation are known. Methods The seasonality of ring formation in mature teak trees was examined via correlative analysis of cambial activity, xylem and phloem formation, and climate throughout 1·5 years. Xylem and phloem differentiation were visualized by light microscopy and scanning electron microscopy. Key Results A 3 month dry season resulted in semi-deciduousness, cambial dormancy and formation of annual xylem growth rings (AXGRs). Intra-annual xylem and phloem growth was characterized by variable intensity. Morphometric features of cambium such as cambium thickness and differentiating xylem layers were positively correlated. Cambium thickness was strongly correlated with monthly rainfall (R2 = 0·7535). In all sampled trees, xylem growth zones (XGZs) were formed within the AXGRs during the seasonal development of new foliage. When trees achieved full leaf, the xylem in the new XGZs appeared completely differentiated and functional for water transport. Two phloem growth rings were formed in one growing season. Conclusions The seasonal formation pattern and microstructure of teak xylem suggest that AXGRs and XGZs can be used as proxies for analyses of the tree history and climate at annual and intra-annual resolution. [ABSTRACT FROM AUTHOR]

Abstract: Direct evidence for Central African vegetation history is mostly derived from palynology and palaeolimnology. Although anthracology has proven worthwhile for palaeovegetation reconstructions in temperate regions and South America, charcoal analysis has hardly been applied for Central Africa. Moreover, a transparent charcoal identification procedure using large databases and well defined characters has never been developed. Therefore, we present a Central African charcoal identification protocol within an umbrella database of species names and metadata, compiled from an on-line database of wood-anatomical descriptions (InsideWood), the database of the world''s largest reference collection of Central African wood specimens (RMCA, Tervuren, Belgium) and inventory and indicator species lists. The 2909 Central African woody species covered by this database represent a large fraction of the total woody species richness of Central Africa. The database enables a directed search taking into account metadata on (1) anatomical features, (2) availability of thin sections within the reference collection, (3) species distribution and (4) synonymy. The protocol starts with an anatomical query within this database, focussing on genus rather than species level, proceeds with automatic extension and reduction phases of the resulting species list and ends with a comparative microscopic study of wood reference thin sections and charcoal anatomy. In total, 76.2% of the Central African species in the database are taken into consideration, focussing on indicator and inventory species. The protocol has a large geographical applicability, as it can be optimised for every research area within Central Africa. Specifically, the protocol has been optimised for the Mayumbe region and applied to radiocarbon dated (2055–2205 14Cyr BP) charcoal collections from a pedoanthracological excavation. The validity of the protocol has been proven by the mutual consistency of charcoal identification results and the consistency of these identification results with vegetation history based on phytogeographical and palynological research within and around the Mayumbe. As such, anthracology complements palynology and a combination of both can lead to stronger palaeobotanical reconstructions. [Copyright &y& Elsevier]

Abstract: Engineered wood products are widely used in construction and transportation. Plywood has one of the best physical and mechanical properties for application under moist conditions in use class 3, i.e. exterior exposure without ground contact. Yet a profound knowledge of their moisture dynamics and fungal susceptibility is a prerequisite for proper use. In this paper the results of more than two years of continuous recording of the moisture content of different plywood types in exterior exposure is presented. Clear differences concerning moisture dynamics are apparent regarding wood species, glue type, and veneer thickness. X-ray tomography scans literally offer insight into the weathering state of the veneer layers and glue lines. Fungal susceptibility of the samples relates primarily to wood species and glue type. Furthermore, edge-sealing for fungal testing is necessary to represent in-service situations and yields distinct differences compared to non-sealed test results. There seems to be a relationship between the accumulated moisture content and layered structure of the plywood, but an unequivocal link with fungal decay is not straightforward. [Copyright &y& Elsevier]

Background and Aims Density is a crucial variable in forest and wood science and is evaluated by a multitude of methods. Direct gravimetric methods are mostly destructive and time-consuming. Therefore, faster and semi- to non-destructive indirect methods have been developed. Methods Profiles of wood density variations with a resolution of approx. 50 µm were derived from one-dimensional resistance drillings, two-dimensional neutron scans, and three-dimensional neutron and X-ray scans. All methods were applied on Terminalia superba Engl. & Diels, an African pioneer species which sometimes exhibits a brown heart (limba noir). Key Results The use of X-ray tomography combined with a reference material permitted direct estimates of wood density. These X-ray-derived densities overestimated gravimetrically determined densities non-significantly and showed high correlation (linear regression, R2 = 0·995). When comparing X-ray densities with the attenuation coefficients of neutron scans and the amplitude of drilling resistance, a significant linear relation was found with the neutron attenuation coefficient (R2 = 0·986) yet a weak relation with drilling resistance (R2 = 0·243). When density patterns are compared, all three methods are capable of revealing the same trends. Differences are mainly due to the orientation of tree rings and the different characteristics of the indirect methods. Conclusions High-resolution X-ray computed tomography is a promising technique for research on wood cores and will be explored further on other temperate and tropical species. Further study on limba noir is necessary to reveal the causes of density variations and to determine how resistance drillings can be further refined. [ABSTRACT FROM AUTHOR]

Wood coatings are widely used for aesthetic and protective reasons. Assessment of coating performance during service life is crucial in order to establish a knowledge database for product optimization. A vast amount of techniques is available for analysis of a coating’s behavior of which microimaging is an important tool. In addition to standard microscopy techniques, high-resolution X-ray tomography is presented as a modality offering nondestructive visualization of a coating and the substrate on which it is applied. Combined with analysis of the 3D volumetric data, surface roughness, structure and thickness of the coating layer, penetration depth and related mechanical anchoring can be studied in relation with the underlying substrate. To provide a clear illustration of the possibilities and limitations of this technique, both an opaque solventborne and an opaque waterborne coating applied on two different wood types were scanned and analyzed. Clearly, three-dimensional X-ray imaging at high resolution produces valuable information merely by visualization. Moreover, by proper analysis, quantitative data are obtained taking into account the limitations of X-ray computed tomography and of automated image processing. [ABSTRACT FROM AUTHOR]

• Soil texture did not affect added OM decomposition in winter. • Less added OM was decomposed with coarser texture during warm and dry summer. • This textural influence was indirect by regulation of soil moisture. • Capillary rise had no pronounced impact on added OM mineralization. • Summer drought significantly preserved added OM in sandy soils. Soil organic carbon (SOC) levels generally increase with increasing clay and silt content under similar climatic conditions because of increased physicochemical protection. Surprisingly though, many silt loam soils in Western Europe have low top SOC levels compared to coarser textured soils. Soil texture also strongly controls soil moisture with consequent indirect impact on heterotrophic activity. Especially during periods of prolonged drought, which seem to be occurring more frequently throughout Europe, it could be expected that this soil textural control of moisture retention decisively affects added organic matter (OM) decomposition. We hypothesized that, contrary to expected textural effects on physicochemical protection of OM, the higher moisture availability in silty soils strongly favors added OM mineralization during periodic drought than sandy soils. Moreover, as a secondary objective, we investigated if during prolonged drought, capillary moisture supply could significantly alleviate the water stress on added OM decomposition in sand with rather shallow groundwater table. Therefore, we established a one-year field trial in which the upper 0.5 m soil layer was replaced by sand, sandy loam and silt loam soil with low SOC. In a fourth treatment, a gravel layer was added beneath the sand layer to exclude capillary rise. Maize residues were mixed homogenously with soil in top 25 cm in all plots. Changes in soil moisture and maize-C mineralization (C maize -min) were measured. We found that soil texture did not affect C maize -min until after about five months and thereafter C maize -min rates were higher in the silt loam than in the sandy soils. Moisture content correlated positively with the C maize -min rate for the sand-textured soils only. Capillary rise did not result in a significant increase in C maize -min in the sandy soil. After one year, a larger share of added C maize was mineralized in the silt loam soil (81 ± 6%) than in the sandy soil (56 ± 7%). These results clearly highlight that soil texture controlled C maize -min indirectly through regulating moisture under the field conditions when the study area faced a period of unusual drought. Moreover, our results imply that, under future climate scenarios, more frequent droughts might lead to a lesser SOC depletion in sandy soils compared to in finer textured soils under similar management. [ABSTRACT FROM AUTHOR]

• Multispecies H-D allometric equations underestimate the total height of the emergent tree species Pericopsis elata. • The H-D allometric equation specific to P. elata varies significantly between sites. • This site-specific variation showed to be associated with differences in the stand-level basal area at the regional-scale and tree-level light-availability at the local-scale. • The stand-level maximum asymptotic height increased with tree-level light-availability. Reliable tree height-diameter (H-D) allometric equations are a key tool for the estimation of forest productivity and Above Ground Biomass (AGB). Most existing H-D allometric equations developed for the tropical region are based on large-scale multi-species datasets, and their use to derive information on productivity and AGB at the species level is prone to uncertainties. The single-species H-D allometric equations available are mainly focused on monocultures or stands with simple tree species mixtures and did not account for the site effects. Here we measured the height and diameter of 2,288 trees of the emergent tree species Pericopsis elata (Harms) Meeuwen in the Democratic Republic of the Congo (DRC) and in Cameroon. We first examined how accurate multispecies H-D allometric equations are in predicting the total height of P. elata. We then tested whether single-species H-D allometric equations vary between sites. We developed the first H-D allometric equation of P. elata and tested whether and how stand-level and environmental variables induce changes in H-D allometric relationship of P. elata at the regional level. We additionally evaluated whether tree-level variables are important at the local level where climate and stand development stage are expected to be less variable. We found that pantropical, regional and local H-D allometric equations significantly underestimate the total height of P. elata. The local multi-species H-D allometric equation developed for Yangambi showed the highest underestimation in all the studied sites. This result supports the need for an H-D allometric equation specific for P. elata. The species-level H-D allometric equation developed showed significant underestimations for trees from the disturbed and undisturbed forests in DRC, while overestimations were observed for similar sites in Cameroon. Using a mixed-effect H-D allometric equation, we showed that even within a single species, a substantial variation exists between sites. This variation showed to be driven by the differences in the maximum asymptotic height (H max) between sites. We found that P. elata trees are taller and attain higher H max in DRC than in Cameroon. The basal area showed to be a significant covariate accounting for the site effects at the regional-scale where climate variables showed minor effects. However, at the local-scale, none of climate or stand variables showed to be significant. Local-scale variation showed to be associated with differences in light availability, highlighting the potential of management options that shape the local environment in driving species productivity. [ABSTRACT FROM AUTHOR]

The global role of tree-based climate change mitigation is widely recognized; trees sequester large amounts of atmospheric carbon, and woody biomass has an important role in the future biobased economy. In national carbon and biomass budgets, trees growing in hedgerows and tree rows are often allocated the same biomass increment data as forest-grown trees. However, the growing conditions in these linear habitats are different from forests given that the trees receive more solar radiation, potentially benefit from fertilization residuals from adjacent fields and have more physical growing space. Tree biomass increment and carbon storage in linear woody elements should therefore be quantified and correctly accounted for. We examined four different hedgerow systems with combinations of pedunculate oak, black alder and silver birch in northern Belgium. We used X-ray CT scans of pith-to-bark cores of 73 trees to model long-term (tree life span) and short-term (last five years) trends in basal area increment and increment in aboveground stem biomass. The studied hedgerows and tree rows showed high densities (168–985 trees km-1) and basal areas (22.1–44.9 m2 km-1). In all four hedgerow systems, we found a strong and persistent increase in stem biomass and thus carbon accumulation with diameter (long-term trend). The current growth performance (short-term trend) also increased with tree diameter and was not related to hedgerow tree density or basal area, which indicates that competition for light does not (yet) limit tree growth in these ecosystems. The total stem volume was 82.0–339.7 m³ km-1 (corresponding to 18.8–100.7 Mg aboveground carbon km-1) and the stem volume increment was 3.1–14.5 m³ km-1 year-1 (aboveground carbon sequestration 0.7–4.3 Mg km-1 year-1). The high tree densities and the persistent increase in growth of trees growing in hedgerow systems resulted in substantial wood production and carbon sequestration rates at the landscape scale. Our findings show that trees growing in hedgerow systems should be included when biomass and carbon budgets are drafted. The biomass production rates of hedgerow trees we provide can help refine the IPCC Guidelines for National Greenhouse Gas Inventories. • Hedgerows and tree rows show high tree density and basal area per running kilometer. • Aboveground stem growth does not stagnate with the aging of hedgerow trees. • Tier 3 estimates for oak, birch and alder in hedgerow systems are formulated. • Hedgerow systems represent a substantial contribution to biomass and carbon budgets. [ABSTRACT FROM AUTHOR]

Clanwilliam cedar (Widdringtonia cedarbergensis ; WICE) , a long-lived conifer with distinct tree rings in Cape Province, South Africa, has potential to provide a unique high-resolution climate proxy for southern Africa. However, the climate signal in WICE tree-ring width (TRW) is weak and the dendroclimatic potential of other WICE tree-ring parameters therefore needs to be explored. Here, we investigate the climatic signal in various tree-ring parameters, including TRW, Minimum Density (MND), Maximum Latewood Density (MXD), Maximum Latewood Blue Intensity (MXBI), and stable carbon and oxygen isotopes (δ 18O and δ 13C) measured in WICE samples collected in 1978. MND was negatively influenced by early spring (October-November) precipitation whereas TRW was positively influenced by spring November-December precipitation. MXD was negatively influenced by autumn (April-May) temperature whereas MXBI was not influenced by temperature. Both MXD and MXBI were negatively influenced by January-March and January-May precipitation respectively. We did not find a significant climate signal in either of the stable isotope time series, which were measured on a limited number of samples. WICE can live to be at least 356 years old and the current TRW chronology extends back to 1564 CE. The development of full-length chronologies of alternative tree-ring parameters, particularly MND, would allow for an annually resolved, multi-century spring precipitation reconstruction for this region in southern Africa, where vulnerability to future climate change is high. [ABSTRACT FROM AUTHOR]

Many microdensitometric techniques are available for deriving maximum latewood density (MXD), which is the state-of-the-art proxy parameter for local to hemispheric-scale temperature reconstructions of the last millennium. Techniques based on X-ray radiation and visible light reflection, such as "blue intensity" (BI), integrate both the density/composition and the dimensions of the cell walls to derive microdensitometric data. In contrast, the dendroanatomical technique relies only on the dimensions of the cell walls. It is therefore possible to isolate cell wall variables by subtracting data derived using the dendroanatomical technique from data derived using X-ray and BI-based techniques. In this study, we explore differences in well-replicated data from parallel X-ray, BI, and dendroanatomical measurements of temperature-sensitive Pinus sylvestris trees from northern Finland. We aim to determine whether cell wall density is critical to the success of X-ray-based MXD, and whether the BI-based parameter counterpart, here termed MXBI, contains useful information about the composition of the cell wall (specifically the lignin). Our results indicate that cell wall density and cell wall BI have no relevant influence on MXD and MXBI measurements. Even in years with severely reduced lignification, identified as so-called "blue rings", dendroanatomical MXD (aMXD) measurements do not deviate significantly from their MXD or MXBI counterparts. Moreover, derived chronologies of cell wall density and cell wall BI contain no significant climate signals when correlated with local climate. Maximum latewood density of conifers can thus be obtained without bias using the dendroanatomical technique. Because lignin content appears to play a negligible role for cell wall BI, the cell wall BI likely presents the biggest challenge when producing unbiased MXBI data. This is because BI data is notorious for cell wall color distortion across the heartwood and sapwood, and between living wood and dead wood, and may therefore distort the otherwise strong link with wood density on multidecadal scales. [ABSTRACT FROM AUTHOR]

Soil texture is well known to directly affect bioavailability of organic matter to heterotrophs, but it also steers their activity by moderating soil moisture fluctuation. Disentangling these direct and indirect textural controls is, however, not trivial and attempts to do so are very scarce. Most attention has just gone to the stimulation of soil carbon (C) mineralization by soil moisture fluctuation per se. To quantify the indirect moisture-mediation control of soil texture on C mineralization, we monitored maize straw degradation in various soil texture/moisture regime combinations. Moisture levels were firstly kept fixed at 32% WFPS (experiment Fixed 32) in a sand, sandy loam and silt loam soil or allowed to fluctuate between 20% and 50% water-filled pore space (WFPS, Dry-wet 20-50). Total maize-C (C maize) mineralized was highly similar between these three textures and thus the direct textural control was minor. On the contrary with the fluctuating moisture level, around threefold more added C maize was mineralized (P < 0.01) in the sand (86%) than in the silt loam (25%) soil. We owe this boost in C maize mineralization to the rewetting of larger pores in the sandy soil which should contain most of the ground maize residue. This determining control of texture on distribution of moisture as well as the maize substrate clearly exceeded the direct impact of texture on organic matter stability. In a third and fourth experiment, timing and dose to remoisten a silt loam soil back to 50% (experiment Equal 20-50) or 35% WFPS (experiment Equal 20-35) when dried out to 20% WFPS were additionally mimicked in the sand and sandy loam soils. These scenarios correspond more closely to a field situation in which nearby differently textured soils all receive the same precipitation input. After several rewetting cycles, the silt loam soil eventually had a 13.9% higher WFPS than the sandy soils. By then moisture stress clearly limited C maize mineralization in the sandy soil (0.13 (Equal 20-50) and 0.05 (Equal 20-35) mg kg−1 h−1) as it proceeded at only half of the rate as in the silt loam soil (0.21 (Equal 20-50) and 0.12 (Equal 20-35) mg kg−1 h−1). The amount of C maize mineralized after 120 days in the silt loam soil was simulated to surpass that in the sandy soil. We conclude that the effect of soil texture on decomposition of a fresh substrate is largely indirect, i.e. through mediation of soil water content and its distribution in the soil matrix. Moreover, our data suggests that in the event of prolonged drought C maize mineralization will be less limited in finer textured soil, contradicting the widespread idea that organic matter would degrade more rapidly in coarser textured soils. • At fixed moisture level OM decomposition was not strongly impacted by soil texture. • With moisture fluctuation textural control enlarged by mediating presence of water. • With equal moisture supply, drying overridingly inhibited C mineralization. • This indirect textural impact depended strongly on moisture regime. [ABSTRACT FROM AUTHOR]

Climate change will intensify drought periods during the growing season in Western Europe. We mimicked this prediction by withholding water in summer from young rooted cuttings of Frangula alnus Mill., a common shrub species, originating from different latitudes in Europe (Italy, Belgium and Sweden) and growing in a common garden environment in Belgium. We followed the responses to the drought up to two years after the treatment. Counter-intuitively, the Italian provenance displayed earlier symptoms and stronger effects of water limitation than the other two provenances. A putative higher transpiration in this provenance could be suggested based on a relative larger shoot growth, larger leaves and a higher stomatal density. After the post-drought re-watering, the droughted plants of the Italian provenance entered leaf senescence later than the control plants, likely as a compensation mechanism for the lost growing time. Bud burst in the first year after the drought treatment and leaf senescence in the next autumn were both advanced in the drought treated group when compared with the control plants. Bud burst in the second year after the drought treatment did not display any differentiation anymore between control and drought treated plants. Growth traits also displayed legacies of the water limitation. For example, the drought treated plants showed a lower number of reshoots upon pruning in the year after the drought treatment. Our results suggest that assisted migration from southern Europe to western Europe as a climate change adaptation strategy might not always follow the expected patterns. [ABSTRACT FROM AUTHOR]

We explore whether a growth-ring analysis can produce additional information about carbon budgets in tropical forests. Such forests are characterized by a high number of species and by trees that rarely have anatomically distinct annual growth rings, which hampers the application of dendrochronological tools in carbon balance assessments in the tropics. We use forest inventory data and archived annual diameter measurements from the Luki Biosphere Reserve in the southwestern margin of the Congo Basin forest massif. In addition, dated wood data are available from the same location thanks to tag nail traces that allow for the measurement of growth increments over a period of 66 years. We find that precise increment measurements based on dated wood are advisable for small subsets of many less abundant species and for functional species groups characterized by slow growth. The dated wood approach shows that many understory trees with non-periodical rings remain in a steady state for long periods of time. These results suggest a dated wood approach is advisable for studies of growth trajectories of individual trees that might be of importance for carbon assessments in degraded forests. [ABSTRACT FROM AUTHOR]

Research Highlights: We investigated the variability of vessel diameter distributions within the liana growth form among liana individuals originating from a single site in Laussat, French Guiana. Background and Objectives: Lianas (woody vines) are key components of tropical forests. Lianas are believed to be strong competitors for water, thanks to their presumed efficient vascular systems. However, unlike tropical trees, lianas are overlooked in field data collection. As a result, lianas are often referred to as a homogeneous growth form while little is known about the hydraulic architecture variation among liana individuals. Materials and Methods: We measured several wood hydraulic and structural traits (e.g., basic specific gravity, vessel area, and vessel diameter distribution) of 22 liana individuals in a single sandy site in Laussat, French Guiana. We compared the liana variability of these wood traits and the correlations among them with an existing liana pantropical dataset and two published datasets of trees originating from different, but species-rich, tropical sites. Results: Liana vessel diameter distribution and density were heterogeneous among individuals: there were two orders of magnitude difference between the smallest (4 µm) and the largest (494 µm) vessel diameters, a 50-fold difference existed between extreme vessel densities ranging from 1.8 to 89.3 vessels mm−2, the mean vessel diameter varied between 26 µm and 271 µm, and the individual theoretical stem hydraulic conductivity estimates ranged between 28 and 1041 kg m−1 s−1 MPa−1. Basic specific gravity varied between 0.26 and 0.61. Consequently, liana wood trait variability, even within a small sample, was comparable in magnitude with tree surveys from other tropical sites and the pantropical liana dataset. Conclusions: This study illustrates that even controlling for site and soil type, liana traits are heterogeneous and cannot be considered as a homogeneous growth form. Our results show that the liana hydraulic architecture heterogeneity across and within sites warrants further investigation in order to categorize lianas into functional groups in the same way as trees [ABSTRACT FROM AUTHOR]

In many research areas, particularly in materials science, retrieving a 3D distribution of the material density in a sample is of key interest. Although standard lab-based X-ray μCT imaging is capable of retrieving the 3D distribution of local attenuation coefficients, the local density cannot be determined unambiguously without the use of calibration standards due to the polychromaticity of the used X-ray tubes. In this paper, two methods are presented to retrieve this information based on accurate knowledge of the polychromatic properties of source and detector in the used μCT system. The methods use a very different approach, one being a polychromatic pre-processing method and one relying on a novel polychromatic iterative reconstruction method, yet produce equivalent results. They are limited to objects with a homogeneous composition, but are extremely powerful in a broad range of applications in materials characterization where the density distribution is of interest. Moreover, the method relying on iterative reconstruction has the potential to be applied for multi-material objects as well. A number of application examples illustrate the potential of the methods to not only retrieve quantitative estimates of density and sub-voxel porosity, but also to greatly reduce or eliminate the spectral artifacts that often hinder conventional calibration schemes. • Two methods for quantitative reconstruction of polychromatic μCT data are presented. • The material density is directly retrieved for mono-material objects. • Using the proposed methodologies, no material-dependent calibration is required. • The methods improve the reconstruction quality for highly-attenuating materials. • One of the methods offers potential for multi-material objects. [ABSTRACT FROM AUTHOR]

Traditionally, fungal growth dynamics were assessed manually, limiting the research to a few environmental conditions and/or fungal species. Fortunately, more automated ways of measurement are gaining momentum due to the availability of cheap imaging and processing equipment and the development of dedicated image analysis algorithms. In this paper, we use image analysis to assess the impact of environmental conditions on the growth dynamics of two economically important fungal species, Coniophora puteana and Rhizoctonia solani. Sixteen environmental conditions combining four temperatures (15, 20, 25 and 30 °C) and four relative humidity (RH) conditions (65, 70, 75 and 80% RH) were tested. Fungal growth characteristics were extracted from images of the growing fungi, taken at regular points in time. Advanced time series analysis was applied to quantitatively compare the effect of the environmental conditions on these growth characteristics. The evolution of the mycelial area and the number of tips over time resulted in typical sigmoidal growth curves. Other growth characteristics such as the mean hyphal segment length did not vary significantly over time. Temperature and RH usually had a combined effect on the growth dynamics of the mycelial area and the number of tips. When defining optimal growth conditions for a fungus, it is therefore of primordial importance that the effect of temperature and RH is assessed simultaneously. At the most extreme conditions we tested, the mycelium most probably experienced water stress when developing over the inert Petri dish surface. An RH of 65% (independent of temperature) for C. puteana and a temperature of 30 °C (independent of RH) for both C. puteana and R. solani therefore always resulted in limited fungal growth, while the optimal growing conditions were at 20 °C and 75% RH and at 25 °C and 80% RH for R. solani and at 20 °C and 75% RH for C. puteana. The method applied in this study offers an updated and broader alternative to classical and narrowly focused studies on fungal growth dynamics, and is well suited to efficiently assess the effect of environmental conditions on fungal growth. [ABSTRACT FROM AUTHOR]

Background: Taxonomic identification of wood specimens provides vital information for a wide variety of academic (e.g. paleoecology, cultural heritage studies) and commercial (e.g. wood trade) purposes. It is generally accomplished through the observation of key anatomical features. Classic methodologies mostly require destructive sub-sampling, which is not always acceptable. X-ray computed micro-tomography (µCT) is a promising non-destructive alternative since it allows a detailed non-invasive visualization of the internal wood structure. There is, however, no standardized approach that determines the required resolution for proper wood identification using X-ray µCT. Here we compared X-ray µCT scans of 17 African wood species at four resolutions (1 µm, 3 µm, 8 µm and 15 µm). The species were selected from the Xylarium of the Royal Museum for Central Africa, Belgium, and represent a wide variety of wood-anatomical features. Results: For each resolution, we determined which standardized anatomical features can be distinguished or measured, using the anatomical descriptions and microscopic photographs on the Inside Wood Online Database as a reference. We show that small-scale features (e.g. pits and fibres) can be best distinguished at high resolution (especially 1 µm voxel size). In contrast, large-scale features (e.g. vessel porosity or arrangement) can be best observed at low resolution due to a larger field of view. Intermediate resolutions are optimal (especially 3 µm voxel size), allowing recognition of most small- and large-scale features. While the potential for wood identification is thus highest at 3 µm, the scans at 1 µm and 8 µm were successful in more than half of the studied cases, and even the 15 µm resolution showed a high potential for 40% of the samples. Conclusions: The results show the potential of X-ray µCT for non-destructive wood identification. Each of the four studied resolutions proved to contain information on the anatomical features and has the potential to lead to an identification. The dataset of 17 scanned species is made available online and serves as the first step towards a reference database of scanned wood species, facilitating and encouraging more systematic use of X-ray µCT for the identification of wood species. [ABSTRACT FROM AUTHOR]

Wood density profiles reveal a tree's life strategy and growth. Density profiles are, however, rarely defined in terms of tissue fractions for wood of tropical angiosperm trees. Here, we aim at linking these fractions to corresponding density profiles of tropical trees from the Congo Basin. Cores of 8 tree species were scanned with X-ray Computed Tomography to calculate density profiles. Then, cores were sanded and the outermost 3 cm were used to semi-automatically measure vessel lumen, parenchyma and fibre fractions using the Weka segmentation tool in ImageJ. Fibre wall and lumen widths were measured using a newly developed semi-automated method. An assessment of density variation in function of growth ring boundary detection is done. A mixed regression model estimated the relative contribution of each trait to the density, with a species effect on slope and intercept of the regression. Position-dependent correlations were made between the fractions and the corresponding wood density profile. On average, density profile variation mostly reflects variations in fibre lumen and wall fractions, but these are species- and position-dependent: on some positions, parenchyma and vessels have a more pronounced effect on density. The model linking density to traits explains 92% of the variation, with 65% of the density profile variation attributed to the three measured traits. The remaining 27% is explained by species as a random effect. There is a clear variation between trees and within trees that have implications for interpreting density profiles in angiosperm trees: the exact driving anatomical fraction behind every density value will depend on the position within the core. The underlying function of density will thus vary accordingly. [ABSTRACT FROM AUTHOR]

X-ray CT scanning is an invaluable technique in many research domains. Different commercial scanner types are developed, tailored to different needs, yet the Centre for X-ray Tomography of the Ghent University (UGCT) develops its own in-house open modular scanners with significant experimental freedom, both for applied research in various fields as for research on tomography itself. The maturity of the technique opens up possibilities in cultural heritage, more specifically the field of wooden musical instruments. Here, we present the possibilities and opportunities of two particular scanners at UGCT: Nanowood and HECTOR. Instruments of different size and shape can be scanned either entirely either one can focus on a specific region of the instrument, resulting in qualitative and quantitative mapping of a range of features at different spatial scales. A cello, acoustic guitar, violin and bow, pipa and standard recorder are scanned using different acquisition modes, and qualitative and quantitative assessment of different features such as general structure assessment, glue line integrity, thickness distribution mapping, volume calculations, growth ring analysis are illustrated. These examples demonstrate the flexible and powerful use of lab-based CT scanners for nondestructive research of wooden musical instruments. [ABSTRACT FROM AUTHOR]

The article discusses the importance of conserving African bistable savannas due to their biodiversity value. It presents an experiment on natural forest regeneration through the exclusion of anthropogenic fire, arguing that it is more effective to let nature restore forests rather than artificially planting or burning. The authors clarify that their study did not advocate for afforestation, but rather focused on natural forest regeneration. They emphasize the need for a thorough understanding of the local context when deciding between restoring forests or protecting savannas. [Extracted from the article]

Background: Acoustic emission (AE) sensing is in use since the late 1960s in drought-induced embolism research as a non-invasive and continuous method. It is very well suited to assess a plant's vulnerability to dehydration. Over the last couple of years, AE sensing has further improved due to progress in AE sensors, data acquisition methods and analysis systems. Despite these recent advances, it is still challenging to detect drought-induced embolism events in the AE sources registered by the sensors during dehydration, which sometimes questions the quantitative potential of AE sensing. Results: In quest of a method to separate embolism-related AE signals from other dehydration-related signals, a 2-year-old potted Fraxinus excelsior L. tree was subjected to a drought experiment. Embolism formation was acoustically measured with two broadband point-contact AE sensors while simultaneously being visualized by X-ray computed microtomography (µCT). A machine learning method was used to link visually detected embolism formation by µCT with corresponding AE signals. Specifically, applying linear discriminant analysis (LDA) on the six AE waveform parameters amplitude, counts, duration, signal strength, absolute energy and partial power in the range 100–200 kHz resulted in an embolism-related acoustic vulnerability curve (VCAE-E) better resembling the standard µCT VC (VCCT), both in time and in absolute number of embolized vessels. Interestingly, the unfiltered acoustic vulnerability curve (VCAE) also closely resembled VCCT, indicating that VCs constructed from all registered AE signals did not compromise the quantitative interpretation of the species' vulnerability to drought-induced embolism formation. Conclusion: Although machine learning could detect similar numbers of embolism-related AE as µCT, there still is insufficient model-based evidence to conclusively attribute these signals to embolism events. Future research should therefore focus on similar experiments with more in-depth analysis of acoustic waveforms, as well as explore the possibility of Fast Fourier transformation (FFT) to remove non-embolism-related AE signals. [ABSTRACT FROM AUTHOR]

• Water sorption/desorption can linearly increase the deflection of OSB. • Strain transferal plays a crucial role in the mechanical performance of OSB. • Recommendations for OSB application in dynamic moisture conditions were drafted. Oriented strand board (OSB) is used as in-service loadbearing material. The impact of water sorption/desorption on the fatigue deflection is not fully understood yet. In this study, fatigue deflection of two types of OSB was studied when exposed to cyclic loading using the three point bending static method for 12 cycles. During cyclic loading, the specimens were wetted and dried before cycle 4, 7 and 10 respectively. Deflection and strain distributions were continuously recorded with digital image correlation (DIC) during the bending test. The results show that both recoverable and residual deflection mainly occurs in the first cycle. Water sorption/desorption can linearly increase the deflection of the specimens. Both large deflection and strain are prone to occur in a region 1–3 mm beneath the top surface. Large strains along the thickness direction induced during water sorption/desorption can be transferred from the top to the bottom surface of the specimens. Strain accumulation is an important factor of the decreasing loading capacity of OSB. Structural changes induced with shear strain could hurdle strain transferal along the thickness direction. Increasing water resistance and reducing structural defects are essential to guarantee proper strain transfer in OSB aiming at in-service loading conditions. [ABSTRACT FROM AUTHOR]

A large share of the global forest restoration potential is situated in artificial 'unstable' mesic African savannas, which could be restored to higher carbon and biodiversity states if protected from human‐induced burning. However, uncertainty on recovery rates in protected unstable savannas impedes science‐informed forest restoration initiatives. Here, we quantify the forest restoration success of anthropogenic fire exclusion within an 88‐ha mesic artificial savanna patch in the Kongo Central province of the Democratic Republic of the Congo (DR Congo). We found that aboveground carbon recovery after 17 years was on average 11.40 ± 0.85 Mg C ha−1. Using a statistical model, we found that aboveground carbon stocks take 112 ± 3 years to recover to 90% of aboveground carbon stocks in old‐growth forests. Assuming that this recovery trajectory would be representative for all unstable savannas, we estimate that they could have a total carbon uptake potential of 12.13 ± 2.25 Gt C by 2100 across DR Congo, Congo and Angola. Species richness recovered to 33.17% after 17 years, and we predicted a 90% recovery at 54 ± 2 years. In contrast, we predicted that species composition would recover to 90% of old‐growth forest composition only after 124 ± 3 years. We conclude that the relatively simple and cost‐efficient measure of fire exclusion in artificial savannas is an effective nature‐based solution to climate change and biodiversity loss. However, more long‐term and in situ monitoring efforts are needed to quantify variation in long‐term carbon and diversity recovery pathways. Particular uncertainties are spatial variability in socio‐economics and growing conditions as well as the effects of projected climate change. [ABSTRACT FROM AUTHOR]

Meteorological stations are rare in central Africa, which leads to uncertainty in regional climatic trends. This is particularly problematic for the Congo Basin, where station coverage decreased significantly during the last few decades. Here, we present a digitized dataset of daily temperature and precipitation from the Yangambi biosphere reserve, covering the period 1960–2020 (61 years) and located in the heart of the Congo Basin. Our results confirm a long-term increase in temperature and temperature extremes since the 1960s, with strong upward trends since the early 1990s. Our results also indicate a drying trend for the dry season and intensification of the wet season since the early 2000s. Ongoing warming and increasing precipitation seasonality and intensity already have a significant impact on crop yields in Yangambi. This calls for urgent development of climate-smart and dynamic agriculture and agroforestry systems. We conclude that systematic digitization and climate recording in the Congo Basin will be critical to improve much-needed gridded benchmark datasets of climatic variables. [ABSTRACT FROM AUTHOR]

Thermally modified timber (TMT) reduces hygroscopicity, increases dimensional stability, and decay resistance. Although there is a substantial amount of research on heat-treated wood, investigations on the sensitivity of cell wall swelling behavior to water variation are limited. Therefore, this study focused on the swelling behavior of TMT from cellular and chemical perspectives. The effects of heat treatment on the hygroscopicity and swelling behavior of the wood cell walls were studied using dynamic vapor sorption and confocal laser scanning microscopy. Changes in the chemical composition and cellulose crystallinity were studied using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction. The results revealed that the hygroscopic swelling of latewood significantly decreased with increasing treatment temperature, reducing the anisotropy of the wood cell swelling. The hygroscopicity of wood was reduced by heat treatment, and a clear decrease in hysteresis was observed at elevated treatment temperatures. The FTIR spectra indicated that both hemicellulose and lignin were degraded. The crystallinity and lateral size of the cellulose increased after heat treatment. Similar changes in the chemical composition and crystallinity of cellulose were observed in the latewood and earlywood. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Recent research has highlighted the importance of living tissue in wood. Polyploidization can impact amounts and arrangements of living cells in wood, potentially leading to increased drought tolerance. Tetraploid variants were created from the apple cultivar Malus .domestica 'Gala' (Gala-4x) and their vulnerability to drought-induced cavitation and their hydraulic capacitance were compared to those of their diploid predecessors (Gala-2x). Assuming a positive correlation between polyploidy and drought tolerance, we hypothesized lower vulnerability and higher capacitance for the tetraploid. METHODS: Vulnerability to drought-induced cavitation and the hydraulic capacitance were quantified through acoustic emission and continuous weighing of shoots during a bench-top dehydration experiment. To underpin the hydraulic trait results, anatomical variables such as vessel area, conduit diameter, cell wall reinforcement, and ray and vessel-associated parenchyma were measured. KEY RESULTS: Vulnerability to drought-induced cavitation was intrinsically equal for both ploidy variants, but Gala-4x proved to be more vulnerable than Gala-2x during the early phase of desiccation as was indicated by its significantly lower air entry value. Higher change in water content of the leafy shoot, higher amount of parenchyma, and larger vessel area and size resulted in a significantly higher hydraulic capacitance and efficiency for Gala-4x compared to Gala-2x. CONCLUSIONS: Both ploidy variants were typified as highly sensitive to drought-induced cavitation, with no significant difference in their overall drought vulnerability. But, when water deficit is short and moderate, Gala-4x may delay a drought-induced decrease in performance by trading hydraulic safety for increased release of capacitively stored water from living tissue. [ABSTRACT FROM AUTHOR]

Moisture has a significant influence on the mechanical and physical properties and on the biological durability of wood and wood based materials. As plywood is commonly used as a building material for outdoor applications knowledge regarding its moisture behaviour is of utmost importance. The aim of this research is to model water accumulation in plywood panels in terms of their basic characteristics and in-service moisture conditions. Therefore, moisture dynamics of 29 uncoated plywood types consisting of different wood species, adhesives and layering were evaluated using a simple laboratory water floating test and an outdoor continuous moisture measurement set-up. A significant correlation was found between laboratory and field test results. By means of regression analysis the material characteristics affecting the moisture dynamics of plywood were evaluated. The most influential parameters were wood species, glue type and thickness of the top veneer. Limit values for the water left in the plywood specimen after 72 h absorption and subsequent 72 h desorption, the residual moisture content (rm 72 ), were calculated as to develop a classification tool for plywood. Based on such a classification tool some recommendations for uncoated plywood regarding end use and service life were drafted. Enhanced performance should be obtained by means of wood preservation or by reducing its residual moisture by applying a coating or by an optimal selection of adhesive, wood species and top veneer thickness. [ABSTRACT FROM AUTHOR]

The distribution and good spreading of adhesive resins is critical for the wood-based panels industry. Full 3D non-destructive characterization is necessary, but methods are limited due to the chemical similarities between the resins and the wood fibers. For X-ray microtomography (μ CT), the doping of the resin with a highly attenuating contrast agent is necessary to visualize the resin distribution. However, the attenuation signal remains hard to segment clearly due to partial volume effects in the image, and phase mixing in the material. To help in the identification of the doped resin, dual-energy X-ray CT (DECT) is used to exploit the contrast agent's K-edge, based on simulations which take into account the polychromatic properties of the X-ray tube and detector response. The contrast agent's identification with DECT is validated with elemental mapping using scanning electron microscopy combined with energy-dispersive spectroscopy (SEM-EDX) on the surface of a wood-based panel sample, using data fusion between DECT and SEM-EDX. Overall, DECT results here in the first 3D identification of doped resin inside wood fiberboards, guiding the industry's efforts in further improving the durability of wood-based panels. [ABSTRACT FROM AUTHOR]

Thermal modification is widely applied to improve moisture dynamics of wood, however often decreasing the mechanical strength. It is therefore required to enhance the mechanical strength of thermally modified timber (TMT), for example by impregnation with adhesives. Specimens, cut from Douglas-fir, were thermally modified (TM) either after phenol formaldehyde (PF) resin impregnation (IM-TM) or before (TM-IM). The microstructural and chemical properties were investigated with SEM and FTIR. Compressive stress, as one of the important mechanical properties, was measured using a universal testing machine, while strain distribution was recorded with digital image correlation (DIC). The results show that the compressive stress of TM specimens can be enhanced significantly by PF resin impregnation. Compressive stress differences between IM-TM and TM-IM specimens are small despite of the larger amount of resin in TM-IM specimens. Thermal modification decomposes part of the PF resin in the cell lumens and promotes chemical reaction between the PF resin and wood. PF resin improves the stiffness and ductility of the wood cell wall, resulting in smaller strain and homogenous distribution thereof. These factors lead to high compressive stress of IM-TM and TM-IM specimens. Although PF resin impregnation contributes to narrowing strain accumulation in earlywood of TM specimens, control specimens have the smallest strain ratio between earlywood and latewood. The findings of this study are helpful for optimizing the cost effective thermal-impregnation technology of producing TMT with improved compressive stress. [ABSTRACT FROM AUTHOR]

Background: The identification of tropical African wood species based on microscopic imagery is a challenging problem due to the heterogeneous nature of the composition of wood combined with the vast number of candidate species. Image classification methods that rely on machine learning can facilitate this identification, provided that sufficient training material is available. Despite the fact that the three main anatomical sections contain information that is relevant for species identification, current methods only rely on transverse sections. Additionally, commonly used procedures for evaluating the performance of these methods neglect the fact that multiple images often originate from the same tree, leading to an overly optimistic estimate of the performance. Results: We introduce a new image dataset containing microscopic images of the three main anatomical sections of 77 Congolese wood species. A dedicated multi-view image classification method is developed and obtains an accuracy (computed using the naive but common approach) of 95%, outperforming the single-view methods by a large margin. An in-depth analysis shows that naive accuracy estimates can lead to a dramatic over-prediction, of up to 60%, of the accuracy. Conclusions: Additional images from non-transverse sections can boost the performance of machine-learning-based wood species identification methods. Additionally, care should be taken when evaluating the performance of machine-learning-based wood species identification methods to avoid an overestimation of the performance. [ABSTRACT FROM AUTHOR]

As the current method is most suited at a submillimetre scale, it would be most useful to gain insight in decay of wood species and engineered wood-based products with distinct material structures, such as plywood, oriented strand board and insulation materials, where the effect of glue layers, porosity, strand size and orientation on decay progress remains a mystery. Keywords: fungal decay; non-destructive monitoring; structure; wood; X-ray CT scanning EN fungal decay non-destructive monitoring structure wood X-ray CT scanning 408 420 13 05/09/22 20220501 NES 220501 1 Introduction Bio-based building materials are made from renewable resources and produced with considerably less energy and associated carbon emissions than many traditional building materials ([14]; [42]). The wood industry makes use of so-called "Use classes" to determine in which conditions non-durable wood can be used and for which applications the use of durable wood and wood products is necessary to prevent decay over the desired use period ([10]). [Extracted from the article]

Thermal treatment (TMT) impacts the mechanical strength of wood. Investigating the compressive strength (CS) of thermally treated wood with variable growth ring orientation is helpful to better understand the effect of TMT on mechanical performance of wood. Specimens, cut from spruce wood, were classified according to two growth ring orientations, namely 10 degree (fc10) and 40 degree (fc40), these two situations commonly exist in practice. Six replicates from each type were thermally treated with saturated steam at two different temperatures (180 °C and 210 °C), respectively. Dimensional changes, chemical composition, and microstructure of the specimens were monitored before and after TMT using FTIR spectroscopy and optical microscopy. Compressive stress of specimens was determined and, simultaneously, strain distribution was recorded using digital image correlation. The results show that TMT caused mass loss and shrinkage in tangential and radial directions. Changes in chemical composition were mainly due to hemicellulose degradation. For both treated and untreated samples, the CS perpendicular to the grain and deformation of fc10 samples were higher and smaller than that of fc40 samples, respectively. TMT results in brittle wood tissue, which hampered strain transfer along growth rings and changed failure modes of samples. Mechanical strength of fc40 samples was sensitive to be impacted by TMT. Prior to TMT, failure modes of fc10 and fc40 specimens were shear deformation and growth ring buckling, respectively. After TM, failure modes of all specimens changed to shear failure parallel to growth ring boundaries. These structural changes mainly occurred in earlywood. The output of this work contributes to the effective application and scientific evaluation of mechanical performance of TMT wood by considering growth ring orientations. [ABSTRACT FROM AUTHOR]

Laminated veneer lumber (LVL) is an important engineered wood product. Internal structural changes have a substantial influence on the mechanical performance of LVL. To investigate the relationship between the internal structural changes and the compressive strength, poplar LVL layering is manufactured by taking into account the veneer lathe checks, namely lathe checks both facing inwards (TLLT), lathe checks both oriented outwards (LTTL) and lathe checks in one layer facing outwards (LTLT). Macroscopic compressive strength of the samples is measured using a universal testing machine. Microscopic internal structural changes are periodically recorded with X-ray CT when the samples are compressed using a load cell. The results show that the compressive strength of LTLT is significantly higher than that of LTTL and TLLT types of LVL. During the compression test, density increase in the samples is non-homogenous. There is a minor increase in density of the glue line, while this is larger in regions with a low density. Density increase is mainly induced by collapse of large vessels. However, the presence of phenol formaldehyde resin can enhance the resistance of vessels against collapse. Structural changes, i.e., vessels collapse and collapse propagation, are likely to occur in locally heterogeneous regions. Propagation of collapsed vessels is more frequently observed in regions where large vessels are contiguous. [ABSTRACT FROM AUTHOR]

Birch and spruce samples were scanned using X-ray computed tomography (CT) to determine changes in the density and density profile caused by thermo-hydro treatment (THT). Small-dimension wood blocks were subjected to treatment at three different temperatures (160 °C, 170 °C and 180 °C) for 1 h and scanned before and after treatment. Identical acquisition and analysis procedures were used to evaluate the changes in approximate mean density and radial density profile of oven-dried untreated and treated material. The X-ray CT scans enabled measuring of the changes in wood density after THT. The results confirm that there were similar tendencies in the total density decrease with increasing temperature. However, variations in density changes between the earlywood (EW) and latewood (LW) of birch and spruce were found. A correlation of the radial density profiles of treated versus untreated specimens showed a similar density decrease in EW and LW in birch wood and inconsistent reductions in spruce wood. [ABSTRACT FROM AUTHOR]

More severe water limitations will challenge forest ecosystems in Europe. To gain more insight into the putative consequences for forests, we studied how the common shrub Cornus sanguinea L. responds to a period of water withholding in summer, followed by rewatering. We grew potted saplings of a local Belgian and a Pyrenean provenance in a common garden experiment. We quantified the impact on growth and several phenological traits, with a specific focus on autumnal leaf senescence. We showed that the timing of autumnal leaf senescence was earlier in plants that displayed no to little leaf desiccation due to the experienced drought, compared to the controls. On the contrary, plants that suffered heavy to total leaf desiccation resprouted after the drought period and displayed delayed leaf senescence. No shift in the timing of autumnal leaf senescence was observed for plants with intermediate leaf desiccation. Our results suggest two different post-drought recovery strategies acting in the same experiment. Which strategy was activated depended on the severity of the drought stress, and the two strategies cancelled each other for the group of plants with intermediate drought symptoms. The earlier leaf senescence is likely an acclimation response whereas the delayed leaf senescence enables plants to repair damaged tissues. Our results also suggest provenance-dependent responses as the earlier leaf senescence was activated earlier in the Pyrenean provenance (no difference in timing for the delayed leaf senescence). • Two different post-drought recovery strategies act in the same summer dry-out experiment on a common shrub species. • Which strategy is activated depends on the severity of the preceding drought stress. • Limited leaf desiccation due to the drought leads to an advanced leaf senescence, severe leaf desiccation leads to a delay. • Population differentiation was observed in the responses to the drought stress. [ABSTRACT FROM AUTHOR]

Abstract Purpose Droughts are expected to become more intense and frequent. Mixed forests can be more resilient to extreme events, but are the individual trees in mixed forests also more resilient to drought? Methods We sampled 275 trees in 53 temperate forest stands in northern Belgium: monocultures, two-species mixtures, and the three-species mixture of Fagus sylvatica , Quercus robur , and Q. rubra. We related the annual basal area increment of individual trees to drought severity from 1955 to 2015 and calculated growth resistance, recovery, and resilience for six contrasting drought episodes (spring, summer, or full-year drought). Results Tree growth of the diffuse-porous F. sylvatica was more sensitive to drought, summer drought in particular. The ring-porous Q. robur and Q. rubra were mainly affected by spring drought. In general, a tree's growth response to drought was not affected by tree species diversity, but some identity effects emerged. Conclusion The asynchrony in drought responses among the tree species (a large and immediate decrease in growth followed by swift recovery in F. sylvatica vs a smaller delayed response in Quercus) might stabilize productivity in forests in which both are present. The impact of the predicted increasing drought frequency will depend on the timing of the droughts (spring vs summer). Graphical abstract Unlabelled Image Highlights • Drought effects similar in mixed and monoculture TREEWEB forest plots • Asynchrony in the response of Quercus and Fagus tree growth • Fagus more sensitive and more resilient to drought than Quercus • Spring drought relevant for Quercus , summer drought for Fagus [ABSTRACT FROM AUTHOR]

Sustainable use is essential to guarantee future availability of wood. Structural and chemical mapping can contribute to fit-for-purpose usage, as accurate and detailed knowledge of the material enables guided utilization and optimal performance of wood. The platform presented in this paper, illustrated on poplar disks for early selection, collects data in the NIR, visual and X-ray spectrum in maximum 30 min per wood disk. Flatbed scanning proves to be a cheap and fast technique to evaluate basic physical properties such as cross-sectional area and wood density. X-ray CT scanning is used for density mapping adding information on density variation between and within disks. Chemometric modeling of infrared spectra is used to map density, tension wood and lignin content. X-ray- and NIR-based density mapping showed good correlation, although NIR-based maps do not show the same level of detail as X-ray images do due to lower resolution. Results of NIR-based hyperspectral mapping illustrate that tension wood zones were denser and contained less lignin which corresponds with the existence of the G-layer described in the literature. In all, the combination of high-end tools together with simple tools such as flatbed scanning allows for high-throughput and high-resolution quantitative mapping of some of the main properties of poplar wood. Furthermore, infrared scanning can be used to map density, tension wood and chemistry without the need for more complex, expensive and/or time-consuming methods, yet with less accuracy and lower resolution, thus being applicable as single tool for breeding selection. [ABSTRACT FROM AUTHOR]

With the increase in working widths for applicators, granular fertiliser particles spread by centrifugal spreaders have more extensive airborne trajectories. In the field, particles can be subjected to wind which can cause their trajectories to change. In this paper, a 3D ballistic model was developed describing the motion of fertiliser particles taking wind effects into account. The physical properties of eight commonly used fertiliser types were determined: particle density, size distribution and angle of repose. X-ray micro computed tomography was used to determine the shape of the particles and estimate the corresponding drag coefficient. Using these parameters in the newly derived ballistic model, the effect of wind on individual fertiliser trajectories was quantified for each fertiliser type. Three wind directions (head- tail- and crosswind) were analysed for two windspeeds: 3 and 6 m s −1 . The magnitude of the effect was strongly dependent on the physical properties of the fertiliser type, the windspeed and wind direction. Simulations showed that a windspeed of 3 m s −1 already can affect the landing position of individual fertiliser particles by several metres. Generally, particles with lower density, smaller size and a more irregular shape were more sensitive to wind. [ABSTRACT FROM AUTHOR]

Background and Aims Disentangling tree growth requires more than ring width data only. Densitometry is considered a valuable proxy, yet laborious wood sample preparation and lack of dedicated software limit the widespread use of density profiling for tree ring analysis. An X-ray computed tomography-based toolchain of tree increment cores is presented, which results in profile data sets suitable for visual exploration as well as density-based pattern matching. Methods Two temperate (Quercus petraea, Fagus sylvatica) and one tropical species (Terminalia superba) were used for density profiling using an X-ray computed tomography facility with custom-made sample holders and dedicated processing software. Key Results Density-based pattern matching is developed and able to detect anomalies in ring series that can be corrected via interactive software. Conclusions A digital workflow allows generation of structure-corrected profiles of large sets of cores in a short time span that provide sufficient intra-annual density information for tree ring analysis. Furthermore, visual exploration of such data sets is of high value. The dated profiles can be used for high-resolution chronologies and also offer opportunities for fast screening of lesser studied tropical tree species. [ABSTRACT FROM AUTHOR]

• Bending strength of OSB was studied using DIC and X-ray CT. • High MOR is attributed to strain propagation along the central layer. • Strain propagation across the central layer causes low MOR. • Different modes of structural change lead to large variability of MOE and MOR. Oriented strand board (OSB) is an important engineered wood product manufactured through bonding of wood strands in cross-oriented layers. The bending strength, one of the crucial properties for loadbearing material, of OSB strongly depends on its structural characteristics. To understand the bending strength of OSB, strain distribution was continuously monitored during a three-point bending test using digital image correlation (DIC) and internal structure was recorded before and after bending using X-ray computed tomography (X-ray CT) respectively. Specimens were cut either along the length (L specimens) or width (W specimens) of OSB panels. For all specimens, strain accumulation mainly seemed to occur in the top and bottom layers and then propagate along or across the central layer. Structural changes in the top and bottom layers of L specimens was either strand delamination or snap off, while only snap off is found in W specimens. This is the main reason of high modulus of elasticity (MOE) and modulus of rupture (MOR) of L specimens in comparison to W specimens. High MOR of the specimens is attributed to strain propagation along the central layer, which can absorb energy from loading. Strain propagation across the central layer causes low MOR, resulting from failure of small strands and delamination in the central layer. Different modes of structural change lead to large variability of MOE, MOR and deformation of the specimens even cut from a single OSB panel. Understanding the bending strength contributes to optimizing the production and application of OSB. [ABSTRACT FROM AUTHOR]