Wood Anatomy

Fiber diameters are typically 15-45 j,m. When wood is reduced to wood flour, the resulting particles are actually bundles of wood fibers rather than individual fibers and can contain lesser amounts of other features such as ray cells and vessel elements. Further information on wood anatomy can be found in Refs [10, 11]. 

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Trees are classified into two major groups termed softwoods (gymnosperms) and hardwoods (angiosperms). The botanical basis for classification is whether or not the tree seed is naked as in softwoods or covered as in hardwoods. A more familiar classification, which with some exceptions is valid, is based on the retention of leaves by softwoods or the shedding of leaves by hardwoods. Thus the softwoods are often referred to as evergreen trees and hardwood as deciduous trees. The major difference with regard to wood anatomy is the presence of vessels in hardwoods. Vessels are structures composed of cells created exclusively for the conduction of water. Softwoods lack vessels but have cells termed longitudinal tracheids which perform a dual role of conduction and support. 

Carlquist, S. 2001. Comparative Wood Anatomy Systematic, Ecological, and Evolutionary Aspects of Dicotyledon Wood, 2nd ed. Springer Verlag, Berlin. 

It was mentioned earlier that charcoal makers are well aware that woods from different tree species yield charcoals of differing quality. These differences can be linked to differences in wood anatomy and composition. There are well known and well-characterised anatomical and chemical differences between softwoods and hardwoods, for example [13], and softwood charcoal is widely regarded as inferior to that from hardwoods. Significant differences can also exist between the charcoals and charcoal yields from superficially similar species of the same genus. This has been shown in the case of Eucalyptus species [14][15]. There can even be differences in charcoals made from trees of the same species when these come from regions with dissimilar climates or soil types. 

Anderson, L.C. 1974. A study of systematic wood anatomy in Cannabis Botanical Museum Leaflets Harvard University 24(2) 29-36. 

As the structure is assimilated or altered by deleterious agents, resistance is diminished relative to the component that has been lost or altered. Loss or alteration of wood components can occur on either the microstructural level (as precipitated by microorganisms) or on the macrostructural level (as precipitated by insects). Dysfunction properties are qualitatively and quantitatively related to degradation. A knowledge of wood anatomy and the relationship between its components is essential to understanding what occurs when a particular component or section of the matrix has been degraded. Some appropriate publications are Core et al. (2), Jane (3) and Panshin and de Zeeuw (4). 

Perre, R, 1997. Image analysis, homogenization, numerical simulation and experiment as complementary tools to enlighten the relationship between wood anatomy and drying behavior. Drying Technol. J., 15 2211-2238. 

Figures 7.5-7.8 are SEM micrographs of carbonized woods. Wood anatomy is a developed science with an extensive literature. These four micrographs are included to show the...

McGinnes E A Jr, Phelps J E, Szopa P S, Shigo A L 1977 Wood anatomy after tree injury -a pictorial study. Univ Missouri College Agric Res Bull 1025, 35 pp... 

Carlquist, S., 2001. Comparative Wood Anatomy, Springer, Berlin. 

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