ABSTRACT
Wood exposed outdoors undergoes a number of physical and chemical phenomena mostly caused by moisture influences, sunlight, and temperature. The degradation of wood by any biological or physical agent modifies some of the organic components of wood. These components are primarily polysaccharides (cellulose and hemicelluloses) and polyphenolics (lignin). Extractives are also present in relatively small quantities, and their concentration determines color, odor, and other nonmechanical properties of a wood species. A change in the organic components may be caused by an enzyme, a chemical, or electromagnetic radiation, but invariably the net result is a change in molecular structure through some chemical reaction.
