Usable Types of Wood
The wood from heartwood and branches larger than 3 inches in diameter is not desirable due to its high C/N ratio (approximately 600:1), which requires a lot of nitrogen in its decomposition. Only the sapwood and young branches (under 3 inches in diameter) from the various noble hardwoods (hard woods high in tannins such as oak, chestnut, maple, beech and acacia) is used as their heartwood is high in tannins.
Conifers are avoided because of their specific lignin (10 to 20%, however, they are tolerated in combination with deciduous RCW). The resin has no aggradation character because it consists of derivatives of diterpenes (resin part) and monoterpenes (part turpentine). Note that only the genera Pinus, Picea, Larix and Pseudotsuga have resin canals. The cedars are characterized by their constituents of the heartwood toxic to microorganisms, tropolone derivatives (thujaplicines) phenolic nature, and are therefore to be avoided in the production of ramial chipped wood.
The acidification of soils by RCW has not been observed. In contrast, acidic soils tend to have thei pH raised by RCW applications.
While some species, such as Black Locust and Black Walnut, bear heartwood containing resins that make them resistant to rot; in practice their RCW decomposes well on a moist soil. Even Larch, which resists decomposition and is also a gymnosperm, promoted successful forest regeneration in Quebec and was found to be the best of the gymnosperms for use in RCW (even better than some hardwoods).
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