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Understanding the macroscopic structure of wood and its formation is essential to identifying wood and evaluating its properties and quality. Depending on genetic background, environmental conditions, and tree developmental stage, the macroscopic structure of wood can vary greatly and produce specific macroscopic signatures. Here, a comprehensive outline of the wood’s macroscopic structure and the features that can be used to identify wood by macroscopic examination is presented. The planes of observations are first depicted, and the fundamental differences between softwoods and hardwoods are outlined. Then, all the different cell characteristics, arrangements, and distributions that can be macroscopically observed are illustrated with their influence on wood figure and texture and non-anatomical features.

Linked to major volcanic eruptions around 536 and 540 CE, the onset of the Late Antique Little Ice Age has been described as the coldest period of the past two millennia. The exact timing and spatial extent of this exceptional cold phase are, however, still under debate because of the limited resolution and geographical distribution of the available proxy archives. Here, we use 106 wood anatomical thin sections from 23 forest sites and 20 tree species in both hemispheres to search for cell-level fingerprints of ephemeral summer cooling between 530 and 550 CE. After cross-dating and double-staining, we identified 89 Blue Rings (lack of cell wall lignification), nine Frost Rings (cell deformation and collapse), and 93 Light Rings (reduced cell wall thickening) in the Northern Hemisphere. Our network reveals evidence for the strongest temperature depression between mid-July and early-August 536 CE across North America and Eurasia, whereas more localised cold spells occurred in the summers of 532, 540-43, and 548 CE. The lack of anatomical signatures in the austral trees suggests limited incursion of stratospheric volcanic aerosol into the Southern Hemisphere extra-tropics, that any forcing was mitigated by atmosphere-ocean dynamical responses and/or concentrated outside the growing season, or a combination of factors. Our findings demonstrate the advantage of wood anatomical investigations over traditional dendrochronological measurements, provide a benchmark for Earth system models, support cross-disciplinary studies into the entanglements of climate and history, and question the relevance of global climate averages.

Exploring the anatomical variability along the stem of cacti requires obtaining high-quality thin sections from hard and soft tissues. Several embedding, infiltration, and sectioning methods have been applied mainly to investigate the harder stem base of cacti, where thin cross-sections are relatively easy to obtain. However, analyzing the variation of anatomical features along cacti stems remains a challenge. Specifically, at the tip of cacti stems, the soft and water-rich dominant tissues are difficult to infiltrate. Here we show results obtained by adapting polyethylene glycol (PEG) infiltration techniques and present a step-by-step description of a fast and hazardous chemical-free method that allows successful cross-sectioning. This infiltration technique may provide a tool to further explore and quantify xylem anatomical trait variation along stems of a wide range of succulent-stemmed taxa.

Near upper forest line, values of conifer wood anatomical traits are species-specific, but relationships among traits are common. Growing season temperature significantly impacts wood anatomy only in its extremes. Quantitative wood anatomy can provide detailed insight into adaptation of trees to changing environment, especially on the borders of species distribution ranges. This study investigated wood anatomy of Pinus sylvestris L., Pinus sibirica Du Tour, and Picea obovata Ledeb. near the forest line in the Western Sayan Mountains, where local climate changes rapidly. Anatomical traits reflecting three developmental stages of conifer tracheids (division = cell number, cell enlargement = radial diameter, and secondary wall deposition = cell wall thickness) were calculated for earlywood, latewood and total tree ring over 50 years. Similar earlywood anatomical structure and low between-trait correlations (r = 0.21…67) were observed in all species, which supports prevalence of external impact on its formation, i.e. that shared habitat, climate, and similar habitus provide common trade-off between hydraulic efficiency and safety. Also, stronger nonlinearity of relationship between cell number and radial diameter in earlywood decreased correlations between them. In latewood, anatomical traits are strongly interconnected (r = 0.63…93) for all species. However, Siberian pine has significantly less pronounced latewood; later switch from earlywood and different strategy of carbon allocation are proposed as possible reasons. Length of vegetative season and sum of temperatures above thresholds 5 °C and 8 °C have no significant correlations with anatomical traits, but extremes of these temperature variables led to forming more pronounced latewood (higher proportion of latewood cells with thicker walls) during warm/long vegetative seasons than during short/cool ones.

The largest explosive volcanic eruption of the Common Era in terms of estimated sulphur yield to the stratosphere was identified in glaciochemical records 40 years ago, and dates to the mid-thirteenth century. Despite eventual attribution to the Samalas (Rinjani) volcano in Indonesia, the eruption date remains uncertain, and the climate response only partially understood. Seeking a more global perspective on summer surface temperature and hydroclimate change following the eruption, we present an analysis of 249 tree-ring chronologies spanning the thirteenth century and representing all continents except Antarctica. Of the 170 predominantly temperature sensitive high-frequency chronologies, the earliest hints of boreal summer cooling are the growth depressions found at sites in the western US and Canada in 1257 CE. If this response is a result of Samalas, it would be consistent with an eruption window of circa May–July 1257 CE. More widespread summer cooling across the mid-latitudes of North America and Eurasia is pronounced in 1258, while records from Scandinavia and Siberia reveal peak cooling in 1259. In contrast to the marked post-Samalas temperature response at high-elevation sites in the Northern Hemisphere, no strong hydroclimatic anomalies emerge from the 79 precipitation-sensitive chronologies. Although our findings remain spatially biased towards the western US and central Europe, and growth-climate response patterns are not always dominated by a single meteorological factor, this study offers a global proxy framework for the evaluation of paleoclimate model simulations.

Background and AimsPetioles are important plant organs connecting stems with leaf blades and affecting light-harvesting ability of the leaf as well as transport of water, nutrients and biochemical signals. Despite the high diversity in petiole size, shape and anatomy, little information is available regarding their structural adaptations across evolutionary lineages and environmental conditions. To fill this knowledge gap, we investigated the variation of petiole morphology and anatomy of mainly European woody species to better understand the drivers of internal and external constraints in an evolutionary context.MethodsWe studied how petiole anatomical features differed according to whole-plant size, leaf traits, thermal and hydrological conditions, and taxonomic origin in 95 shrubs and trees using phylogenetic distance-based generalized least squares models.Key ResultsTwo major axes of variation were related to leaf area and plant size. Larger and softer leaves are found in taller trees of more productive habitats. Their petioles are longer, with a circular outline and are anatomically characterized by the predominance of sclerenchyma, larger vessels, interfascicular areas with fibres and indistinct phloem rays. In contrast, smaller and tougher leaves are found in shorter trees and shrubs of colder or drier habitats. Their petioles have a terete outline, phloem composed of small cells and radially arranged vessels, fibreless xylem and lamellar collenchyma. Individual anatomical traits were linked to different internal and external drivers. Petiole length and vessel diameter increase with increasing leaf blade area. Collenchyma becomes absent with increasing temperature, and petiole outline becomes polygonal with increasing precipitation.ConclusionsWe conclude that species’ temperature and precipitation optima, plant height, and leaf area and thickness exerted a significant control on petiole anatomical and morphological structures not confounded by phylogenetic inertia. Species with different evolutionary histories but similar thermal and hydrological requirements have converged to similar petiole anatomical structures.

Although wood anatomical features can provide yearly resolved climatic information at sub-seasonal resolution, the occurrence of intra-annual density fluctuations (IADFs) might be triggered by several abiotic factors under different ecological settings. Here, we use information on cambial age and tree-ring width to standardize the frequency of IADFs in European black pines from three different mountain slopes in the central Apennines (Italy). At each site, we sampled isolated 15–30-year pioneer pines above the forest limit, as well as close-grown 40–60-year planted pines at the forest limit. Mainly restricted to the latewood of both pioneer and planted trees, the occurrence of IADFs reveals a significant positive relationship with cambial age and ring width. Although the standardized IADFs are well synchronized between the planted and pioneer pines, the frequency of IADFs in narrow rings was higher in the pioneer pines. Drought conditions in July and August are responsible for the highest IADFs frequency in planted and pioneer pines, respectively. Our study underlines the value of IADFs to obtain a more nuanced understanding of the climatic drivers of wood formation at the intra-annual scale.

Wood identification has never been more important to serve the purpose of global forest protection, by controlling international illegal timber trade and enabling the enforcement of timber trade regulations. Macroscopic wood identification is the fastest method for the first identification of an unknown timber and, with proper training, it can be performed by operators in the timber industry, restorers and curators of cultural heritage, wood traders, designers, students and customs officers. Here we describe a wood atlas and accompanying software, SIR-Legno, developed for the identification of 48 Italian timber species based on a recently proposed list of macroscopic features for wood identification. For each species the atlas provides a complete macroscopic description plus information on natural durability, end-use class, physico-mechanical properties, conservation status, maximum diameter of the bole and most frequent uses. For each genus covered by the atlas, information about species number, CITES-listed species, main commercial timbers, similarly-named timbers from other genera, geographical distribution and notes on species or species group recognition at macroscopic and microscopic level are provided. SIR-Legno is an educational product, a handy identification key and a tool to search woods by their natural durability, end-use class and physico-mechanical properties. Both the atlas and the software can be freely downloaded from the web. Thanks to the adoption of a codified list of characters and a transferable design, SIR-Legno can be easily replicated or expanded to other databases in order to include new species. SIR-Legno is freeware and works on any version of Windows.

In the Earth’s tallest tree species, axial variation in conduit size matches theoretical predictions minimizing the accumulation of hydraulic resistance with height growth, within a constraint of maximum conduit diameter. Hydraulic limitations to tree height can be mitigated by widening the conducting elements toward a tree’s base. However, size limits of tracheid and vessel dimensions may constrain this compensation mechanism as the water transport pathway elongates. Moreover, variation in conduit size is poorly described in tall trees even though their long transport paths have high potential for hydraulic resistance. Here, we evaluated whether axial variation in conduit diameter was uniquely structured, or matched theoretical predictions in Sequoia sempervirens, Sequoiadendron giganteum, and Eucalyptus regnans that were 86–105 m tall and exceeded 85% of the maximum height for each species. Across Sequoia and Sequoiadendron, tree top tracheids maintained constant width, whereas tree base tracheids in the outermost ring were 20% wider in taller trees, suggesting maintenance of basipetal conduit widening with height growth. In all trees, the observed widening decreased at a rate per unit path length that fitted well to a power function with an exponent consistent with hydraulic compensation. However, below about 60 m from the tree tops, conduit diameters approached an asymptote beneath the power function, indicating a limit to maximum conduit size. Quantifying the distribution of base-to-top hydraulic resistance suggested that the minimal hydraulic benefit gained with increasingly wider conduits near the tree base may trade off with other factors such as maintaining mechanical strength or reducing fluid volume. We summarize these results into an anatomical model of height growth that includes limits to axial variation in conduit diameter and is supported by many physiological and anatomical observations.

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Petioles are important plant organs connecting stems with leaf blades and affecting light-harvesting leaf ability as well as transport of water, nutrient and biochemical signals. Despite petiole’s high diversity in size, shape and anatomical settings, little information is available about their structural adaptations across evolutionary lineages and environmental conditions. To fill our knowledge gap, we investigated the variation of petiole morphology and anatomy in 95 European woody plant species using phylogenetic comparative models. Two major axes of variation were related to leaf area (from large and soft to small and tough leaves), and plant size (from cold-adapted shrubs to warm-adapted tall trees). Larger and softer leaves are found in taller trees of more productive habitats. Their petioles are longer, with a circular outline, thin cuticles without trichomes, and are anatomically characterised by the predominance of sclerenchyma, larger vessels, interfascicular areas with fibers, indistinct phloem rays, and the occurrence of prismatic crystals and druses. In contrast, smaller and tougher leaves are found in shorter trees and shrubs of colder or drier habitats. Their petioles are characterized by teret outline, thick cuticle, simple and non-glandular trichomes, epidermal cells smaller than cortex cells, phloem composed of small cells and radially arranged vessels, fiberless xylem, lamellar collenchyma, acicular crystals and secretory elements. Individual anatomical traits were linked to different internal and external drivers. The petiole length and vessel conduit size increase, while cuticle thickness decreases, with increasing leaf blade area. Epidermis cell walls are thicker in leaves with higher specific leaf area. Collenchyma becomes absent with increasing temperature, epidermis cell size increases with plant height and temperature, and petiole outline becomes polygonal with increasing precipitation. We conclude that species temperature and precipitation optima, plant height, leaf area and thickness exerted a significant control on petiole anatomical and morphological structures not confounded by phylogenetic inertia. Unrelated species with different evolutionary histories but similar thermal and hydrological requirements have converged to similar petiole anatomical structures. Our findings contribute to improving current knowledge about the functional morphoanatomy of the petiole as the key organ that plays a crucial role in the hydraulic pathways in plants.

Increased wood density is obtained by compressing the wood porous structure under suitable moisture and temperature conditions to improve its physical, mechanical and color properties. A recently proposed wood densification method based on partial removal of lignin and hemicellulose in hot water solution of sodium hydroxide and sodium sulphite has shown promising results on solid wood. However, its applicability and effect on thin wood veneers have not been tested yet. In this study, the timing of the method has been adapted to estimate the densification treatment intensity dependence of wood properties (wood density and modulus of elasticity) and color change of softwood (Norway spruce) and hardwood (beech) veneers. Compared to control, density and rigidity increased, with improved wood properties peaking after only 90 s of treatment intensity. Furthermore, the color became darker after treatment compared to control, with no significant color difference between treatment intensities. In conclusion, densification of veneers, according to the presented adapted method, provides a significant improvement of veneers physical and mechanical properties, and produces color changes perceptible by the human eye. Our results can be further implemented and adapted to application in industrial plants, calling for new application of densified veneers.

Trees that were killed and buried by volcanic eruptions can be used to date an eruption with annual or even sub-annual resolution. The detection and measurement of subfossil tree-ring widths (TRW), however, often remains challenging if the material was carbonized during the eruption. Here, we show that the application of X-ray densitometry can improve the assessment of charcoal. Measuring the wood density of carbonized trees killed by the Laacher See Eruption ~13,000 years ago, facilitates the identification of the outermost rings that were formed just before the eruption. Our results suggest that anatomical techniques should be routinely applied in the assessment of historical, archaeological and subfossil wood.

This article illustrates a wide multidisciplinary project carried out as part of recent restoration works of the great timber roof of Porta Nuova Railway Station in Turin (Italy). The station was b...

Although the importance of centuries-long tree ring width oak chronologies in dating wood, eastern European regions are still lacking a reference chronology. To fill this geographical gap, we combined living and historical chronologies from the Moldova region, including part of Romania and the Republic of Moldova. Here we present the “Suceava oak chronology” as the first 804 years long chronology continuously covering the 1216–2019 period. Our analyses further revealed the strong teleconnection of the Suceava oak chronology with south European ones. The link between Romania and northern Turkey chronologies is of particular importance in the context of the high abundance of undated subfossil and archaeological/historical oak wood in eastern Europe and intense wood trades with central Europe in XV-XVII centuries. The availability of the Suceava oak chronology will provide a good base for precise dating and climatic reconstructions.

It is generally accepted that animal heartbeat and lifespan are often inversely correlated, however, the relationship between productivity and longevity has not yet been described for trees growing under industrial and pre-industrial climates. Using 1768 annually resolved and absolutely dated ring width measurement series from living and dead conifers that grew in undisturbed, high-elevation sites in the Spanish Pyrenees and the Russian Altai over the past 2000 years, we test the hypothesis of grow fast—die young. We find maximum tree ages are significantly correlated with slow juvenile growth rates. We conclude, the interdependence between higher stem productivity, faster tree turnover, and shorter carbon residence time, reduces the capacity of forest ecosystems to store carbon under a climate warming-induced stimulation of tree growth at policy-relevant timescales. Fertilization under greenhouse warming conditions is expected to accelerate tree growth and potentially increase the biological storage of CO2. Here the authors analyse ring width measurements from 1768 conifers from the Spanish and Russian mountains and demonstrate that longevity requires slow growth rates at least in mountainous regions.

‘Blue Rings’ (BRs) are distinct wood anatomical anomalies recently discovered in several tree species from different sites. While it is evident that they are associated with a cooling-induced lack of cell wall lignification, BRs have yet to be evaluated systematically in paleoclimate studies. Here, we present a continuous wood anatomical assessment of 31 living and relict pine samples from a high-elevation site in the central Spanish Pyrenees that span the period 1150–2017 CE at annual resolution. While most BR years coincide with cold summer temperatures and many BRs follow large volcanic eruptions, some were formed during overall warm summers. We also see a differential response between eruptions: the Samalas eruption is followed by 80% BRs in 1258, but only a modest signal is evident after the 1815 Tambora eruption, and there are no wood anatomical effects of the Laki eruption in 1783–1784. Apparently linked to a cluster of tropical eruptions in 1695 and 1696 CE, 85% BRs occurred in 1698. This new wood anatomical evidence is corroborated by the record of sulphur deposition in polar ice cores, and corresponds with catastrophic famine and unprecedented mortality in Scotland. The extremely rare occurrence of consecutive BRs in 1345 and 1346 marks the onset and spread of the Black Death, Europe’s most devastating plague pandemic. In their ability to capture severe ephemeral cold spells, as short as several days or weeks, BR chronologies can help to investigate and understand the impacts of volcanism on climate and society.

To perform the identification of an unknown specimen you first have to prepare it. To do so, you need some water and one or more of the following cutting tools depending on the specimen: a saw, a utility knife or a razor blade. The saw is a tool you will seldom use; it is necessary only to reshape specimen with grossly out-of-plane surfaces (see section “Specimen Preparation”). At this purpose, a small benchtop band saw or a common handsaw is the best choice. The utility knife is the most useful tool for wood specimen preparation. Thanks to its thin cutting-edge angle it is the best tool to perform clean cuts of the surfaces to obtain a good visibility of the anatomical characters. Moreover, it can be used to adjust the orientation of a specimen surface (see section “Specimen Preparation”). In order to safely make a cut with the utility knife follow this procedure (Fig. 2.1)

This chapter aims to give some basic knowledge to understand and make the best use of the book. After an overview on the three anatomical planes, the main wood features are presented, from the most evident macroscopic ones to the inner cellular composition and structure of softwoods and hardwoods.

In this chapter each character applied for macroscopic wood identification is described along with its character states (in square brackets) and definition (Ruffinatto et al. 2015). Character states represent any possible attribute applicable to a character. The implied surface of observation is the transverse one unless otherwise stated in the character description. A summary of all characters is provided in Table 4.1.