ABSTRACT
Green wood of living and freshly felled trees is a natural and renewable resource prevalent in many human activities, such as wood frame houses and furniture. It is a porous, hygroscopic substance consisting of dead and living cells, and is filled with either water or air. Its physical and chemical properties, as well as drying characteristics, depend on the species, tree structure, and amount of moisture content. From the outermost to the center, a cross section of mature trees consists of three distinguishable parts: bark; wood, and pith. The woody part of mature trees is composed of three zones: the sapwood; heartwood; and pith. Softwoods have a simple, uniform structure with few fiber cell types vertically aligned, with both vertical and horizontal enlarged cavities surrounded by cells. Hardwoods, species derived from the botanic group of angiosperms, are porous materials with a greater variety of more complex cell structures than softwoods.
