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Iveta Čabalová
Technical University in Zvolen, Faculty of Wood Sciences and Technology, Department of Chemistry and Chemical Technologies, T. G. Masaryka 24, 960 01 Zvolen, Slovakia;
Corresponding email: cabalova@tuzvo.sk
ORCID ID: https://orcid.org/0000-0003-2775-047X
ABSTRACT
This scientific monograph focuses on the chemical and morphological changes in Norway spruce wood (Picea abies L. Karst) during storage under natural conditions. Spruce wood is the most common coniferous species in Slovakia and is widely used in the pulp and paper, as well as wood-based panel industries. However, improper or prolonged storage significantly affects its quality and usability due to degradation of its chemical constituents and structural components.
The study provides a comprehensive overview of the wood’s microstructure and its primary chemical components—cellulose, hemicelluloses, lignin, and extractives—while emphasizing the role of external factors such as fungi, temperature, moisture, and UV radiation in their degradation. Experimental methods including chromatographic analysis, pH determination, and fiber morphology assessment were applied to evaluate changes occurring over a 15-month storage period.
The results show a clear decline in the content of extractives and hemicelluloses, a decrease in polymerization degree and molecular weight of cellulose, and changes in fiber dimensions and their distribution. The wood’s acidity increased, which may negatively influence further processing, especially in pulp production. Additionally, microbial activity and fungal colonization were observed to accelerate chemical breakdown, leading to reduced mechanical and physical properties.
The scientific monograph highlights the implications of these changes for industrial applications, especially in the context of producing lower-quality pulp or wood-based boards. It suggests that improved storage strategies—such as debarking or compact stacking—may mitigate degradation and preserve key properties of spruce wood. These findings are relevant for forestry managers, wood processors, and researchers working with lignocellulosic biomass and its utilization in sustainable bio-based industries.
Keywords:
Spruce Wood; Wood Degradation; Storage Impact, Fiber Morphology; Wood –Based Panel Industry
Introduction
Wood is an anisotropic material in terms of its anatomical, physical and chemical properties, and is composed of different types of cells. It is used for various purposes, such as furniture, construction materials, and other uses, or in the pulp and paper industry, for the production of pulp and paper. It is degradable by fungi, microorganisms and thermal action (Yang and Jaakkola, 2011). The degradation of wood and its chemical structure is influenced by temperature, oxygen available to the material, ambient pressure, type and shape of the wood, moisture content in the wood and additives such as inorganic substances, sorbed emissions, etc. (Reinprecht, 2016; Hill, 2006; Militz, 2002). The structure of wood, its chemical components (the content of cellulose, hemicelluloses, lignin and extractives – EL) and its chemical composition depend on the morphological composition, tree species and age of the wood (Yang and Jaakkola, 2011). Differences can be found within a single tree in the direction from the middle of the trunk to the bark, from the ground part to the top, between sapwood and heartwood (Côté, 1968). According to Fengel and Wegener (1989), spring wood contains more lignin and significantly less cellulose than summer wood.
Understanding the morphological and chemical heterogeneity of wood is important for its use in the woodworking and construction industries. Like wood, bark is an important source of raw materials and chemical compounds. The chemical composition of bark varies between different tree species and depends on the morphological composition. Many components contained in wood are also found in bark, but their proportion is different. Bark can be divided into fractions: fibers, cork cells and fine part (including parenchyma cells) (Yang and Jaakkola, 2011). Bark contains much more extractives than wood from the trunk (Rhén, 2004), a significant amount of bioactive components such as antioxidants (polyphenols) and also structural polysaccharides such as pectin (Le Normand et al., 2021).
Like any wood material, spruce wood is chemically complex and its physical, chemical and morphological properties are not uniform. It is the most common type of wood in Slovakia. In spruce wood, approximately 95% of the matrix of wood cells is formed by tracheids, which can also be called fibers. The average length of tracheids is mainly influenced by the age of the tree. Like many other properties of wood, the length and width of the fibers are different depending on their vertical or radial position in the trunk (Dinwoodie, 1961). The length of tracheids is shortest near the pith. Wood growth is first very fast, especially in the juvenile period, then it slows down between the 10th and 30th year and then, when mature wood begins to form, it increases very gradually with seasonal fluctuations (Kučera, 1994).
The scientific monograph focuses on the possibilities of using spruce wood (Picea abies, L. Karst) depending on the length of its storage, focusing on the qualitative requirements of the raw material for the needs of the pulp and paper and woodworking (e.g. for the production of wooden composites) industries.