Wood anatomy is a scientific sub-area of wood science, which examines the variations in xylem anatomical characteristics across trees, shrubs, and herbaceous species to explore inquiries related to plant function, growth, and the environment. Extensive study of the wood structure helps also in macroscopically or microscopically identifying the exact wood species for a variety of scientific, technical, historical, economical and other reasons. In recent years, wood anatomy also helps developing new techniques in preventing the illegal logging of forests, that is the harvest, transportation, purchase, or sale of timber in violation of laws, leading to a number of environmental issues such as deforestation, soil erosion and biodiversity loss. Commonly studied features include the dimensions of lumens and the thickness of walls in the conducting cells (tracheids, vessels), fibers, and various ray properties. The structural attributes of each xylem anatomical feature are largely predetermined upon formation and significantly influence its functionality, encompassing the transport and storage of water, nutrients, sugars, hormones, and mechanical support provision. These anatomical features are localized within the growth rings, facilitating the establishment of intra-annual structure-function relationships and sensitivity to environmental fluctuations. However, generating large datasets of xylem anatomical data poses numerous methodological challenges.
Main topics The wood anatomy includes the study of the structure of the bark, cork, xylem, phloem, vascular cambium, heartwood and sapwood and branch collar. The main topic is the anatomy of two distinct types of wood:
Softwoods Hardwoods
In botanical terminology, softwoods are sourced from gymnosperms, primarily conifers, whereas hardwoods originate from angiosperms, specifically flowering plants. Within the temperate zones of the northern hemisphere, softwoods are typically represented by needle-leaved evergreen trees such as pine (Pinus) and spruce (Picea), while hardwoods are predominantly composed of broadleaf, deciduous trees like maple (Acer), birch (Betula), and oak (Quercus). The differentiation between softwoods and hardwoods extends beyond tree categorization to the cellular level. Softwoods exhibit a simpler basic wood structure, characterized by only two cell types and limited variation within these categories. In contrast, hardwoods display increased structural complexity owing to a higher number of fundamental cell types and a considerable degree of variability within these cell types. The primary distinguishing feature lies in the presence of vessel elements, also referred to as pores, which are characteristic of hardwoods and absent in softwoods. Despite these disparities, softwoods and hardwoods share a cellular similarity – the majority of cells are non-living at maturity, even within the sapwood. These living cells at maturity, identified as parenchyma cells, are present in both softwoods and hardwoods. Specific features (macroscopic, physical, microscopic) have been established by the IAWA for the identification of softwoods and hardwoods.
Databases There are several databases relating to wood anatomy. One of them, InsideWood, is an online resource and database for wood anatomy, serving as a reference, research, and teaching tool. This database was created by several international researchers, members of the IAWA, mostly botanists, biologists and wood scientists. The database thousands of wood anatomical descriptions and nearly 66,000 photomicrographs of contemporary woods, along with more than 1,600 descriptions and 2,000 images of fossil woods. Another very important database for wood anatomy, is the so-called, Delta Intkey. In 2024, a new novel electronic device, named as The XyloTron, was fully developed at the Forest Products Laboratory for fast and reliable identification of wood.
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