The normal color change of wood due to the effect of environment (sunlight, oxygen, water temperature, etc.) and microorganisms (fungi) is called discoloration.
　　1.Classification of wood discoloration
　　Chemical discoloration: abnormal discoloration of red brown, brown or orange yellow caused by chemical and biochemical reaction process of felled wood is called chemical discoloration. Its color is generally uniform, and its distribution is limited to the surface layer (up to 1-5mm deep). After drying, it fades and fades.
　　Discoloration of discoloring bacteria: It is formed by felling sapwood under the action of discoloring bacteria. The most common are cyanosis and mildew. Next is other sapwood stain, including orange yellow, pink or light purple, brown, etc. This defect is mainly caused by slow drying or lack of storage measures.
　　2.Wood decay
　　After being eroded by wood rot fungus, not only the physical and mechanical properties of wood will change, but finally the wood will become soft and fragile, in the form of sieve or powder. This phenomenon is called decay< br> According to the type and nature of decay, it can be divided into white decay and brown decay.