Wood Quality  - Three factors are considered for wood quality: color, texture, and figure.  Color of sapwood does not vary greatly among tree species, but color of heartwood does.  Chemicals called extractives give heartwood a great variety of colors.  Extractives are chemicals that act as natural preservatives.  Cellulose has a specific gravity of 1.53.  Density of wood depends on how closely the cellulose is packed and the amount of extractives in the wood.  Some tropical woods have specific gravity over 1, which means they do not float.  Texture is greatly dependent on size of cells and figure on cell arrangements.  But, the 3 characteristics -color, texture, figure-all assume that the wood has not been altered by extrinsic agents.  This is highly unlikely in nature.  Branches are always dying, protection zones are failing, wounds are being inflicted, roots are dying, and all of these events incite defense processes that cause chemical shunts to produce protection chemicals, and changes in cell types and arrangements.  It is difficult to think of a tree that has not had many injuries.  As a result, cells are different, and cell arrangements are altered.  A tree with high quality wood has few extrinsic disturbances, or the tree has an effective compartmentalization process that keeps all infections walled off to smaller volumes of wood.  A major point is that trees will have wounds and dying branches and, in a sense, these problems become part of the "normal" processes.  To talk about wood quality without considering these points is foolish.

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