In the United States, more than 100 wood species are available to the prospective user, but all are unlikely to be available in any one locality. About 60 native woods are of major commercial importance. Another 30 species are commonly imported in the form of logs, cants, lumber, and veneer for industrial uses, the building trade, and crafts.
A continuing program of timber inventory is in effect in the United States through the cooperation of Federal and State agencies, and new information on wood resources is published in State and Federal reports. Two of the most valuable sourcebooks are An Analysis of the Timber Situation in the United States 1989-2040 (USDA 1990) and The 1993 RPA Timber Assessment Update (Haynes and others 1995).
or sap in the tree. Typically, hardwoods are plants with broad leaves that, with few exceptions in the temperate region, lose their leaves in autumn or winter. Most imported tropical woods are hardwoods. Botanically, softwoods are Gymnosperms or conifers; the seeds are naked (not enclosed in the ovary of the flower). Anatomically, softwoods are nonporous and do not contain vessels. Softwoods are usually cone-bearing plants with needle- or scale-like evergreen leaves. Some softwoods, such as larches and baldcypress, lose their needles during autumn or winter.
Major resources of softwood species are spread across the United States, except for the Great Plains where only small areas are forested. Softwood species are often loosely grouped in three general regions, as shown in Table 1-1. Hardwoods also occur in all parts of the United States, although most grow east of the Great Plains. Hardwood species are shown by region in Table 1-2.
Softwoods are available directly from the sawmill, wholesale and retail yards, or lumber brokers. Softwood lumber and plywood are used in construction for forms, scaffolding, framing, sheathing, flooring, moulding, paneling, cabinets, poles and piles, and many other building components. Softwoods may also appear in the form of shingles, sashes, doors, and other millwork, in addition to some rough products such as timber and round posts.
Hardwoods are used in construction for flooring, architectural woodwork, interior woodwork, and paneling. These items are usually available from lumberyards and building supply dealers. Most hardwood lumber and dimension stock are remanufactured into furniture, flooring, pallets, containers, dunnage, and blocking. Hardwood lumber and dimension
Current information on wood consumption, production, imports, and supply and demand is published periodically by the Forest Products Laboratory (Howard 1997) and is available from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC.
Trees are divided into two broad classes, usually referred to as hardwoods and softwoods. These names can be confusing since some softwoods are actually harder than some hardwoods, and conversely some hardwoods are softer than some softwoods. For example, softwoods such as longleaf pine and Douglas-fir are typically harder than the hardwoods basswood and aspen. Botanically, hardwoods are Angiosperms; the seeds are enclosed in the ovary of the flower. Anatomically, hardwoods are porous; that is, they contain vessel elements. A vessel element is a wood cell with open ends; when vessel elements are set one above another, they form a continuous tube (vessel), which serves as a conduit for transporting water
Table 1-1. Major resources of U.S. softwoods according to region
Incense-cedar Port-Orford-cedar Douglas-fir White firs Western hemlock Western larch Lodgepole pine Ponderosa pine Sugar pine Western white pine Western redcedar Redwood
Engelmann spruce Sitka spruce Yellow-cedar
Northern white-cedar Atlantic white-cedar
Balsam fir Eastern hemlock Fraser fir Jack pine Red pine
Eastern white pine Eastern redcedar Eastern spruces Tamarack
Baldcypress Fraser fir Southern Pine Eastern redcedar
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