Lumber Industry, production and harvesting of trees for varied uses, as in the fabrication of telegraph poles and railroad ties, and in building construction, shipbuilding, and furniture manufacture. The lumber industry includes the various businesses that convert trees, or timber, into lumber products. Other industries convert timber into pulp and paper, chemicals, or fuelwood.
The United States, Russia, Canada, Japan, Sweden, Germany, Poland, France, Finland, and Brazil are the chief lumber-producing countries in the world. In addition, many beautiful varieties of timbersuch as mahogany, ebony, and rosewood, used chiefly in furniture manufactureare produced in tropical Asian, Latin American, and African countries.
Lumber is produced from both hardwood and softwood.Wood from broad-leaved trees is called hardwood, and wood from cone-bearing trees is called softwood, regardless of its actual hardness. Many softwoods are actually harder than some of the so-called hardwoods. Most lumber in the United States is softwood, such as southern yellow pine, Douglas-fir, ponderosa pine, western redcedar, and true firs. Most hardwood lumber, such as oak, gum, yellow-poplar, maple, and ash, is used for miscellaneous industrial applications, primarily wood pallets. Hardwood species with beautiful colors and patterns, such as black walnut, black cherry, or red oak, are used for such high-grade products as furniture, flooring, paneling, and cabinets.
Approximately one-fifth of all U.S. land grows potentially commercial timber, of which about 70 percent is privately owned. The United States annually produces over 30 billion board feet of lumber from theseforests. (The board foot is the standard U.S. measure of lumber and equals the volume of a board that is 1 square ft in area and 1 in thick.) Over two-thirds of this lumber is softwood, which comes primarily from the Southeast and Pacific Northwest. Appalachian and northeastern states produce the majority of hardwood lumber.
Most U.S. lumber production supplies domestic markets, particularly single-family homes. The national economy and natural events both influence the activity of the lumber industry. A good economy encourages people to build new homes or remodel existing ones. Natural disasters, such as the devastation left by Hurricane Andrew in Florida and Louisiana in 1992 and by the Mississippi River flooding in the Midwest in 1993, create a demand for lumber to rebuild damaged homes and businesses. Large forest fires, hurricanes, and epidemic outbreaks of forest pests can also damage forest lands and decrease timber supplies to local mills.
Currently, the United States exports logs and finished lumber products primarily to Japan, Mexico, Germany, and the United Kingdom. Many of the exported logs are converted to lumber that is imported back into the United States. The Canadian provinces of Québec and British Columbia are major global exporters of softwood logs and lumber products, and the United States both exports and imports lumber to and from Canada.
As global demand for lumber rises, increased harvesting has developed in tropical countries and recently in the northern, or boreal, forests of Russia. The current rate of harvesting in tropicalrain forests has alarmed scientists concerned with the ecological importance of these forests in the preservation of biodiversity. Forests also play an important role in regulating the climate of the planet by removing carbon dioxide from the atmosphere (see Carbon Cycle; Ecology). Scientists are therefore also increasingly concerned about the role that tropical deforestation may play in global warming (see Environment).
II. Methods of Lumbering
The lumber industry consists of three divisionsthe logging industry, the sawmill industry, and the panel industryeach of which can be seen as a stage in the journey of a tree from the forest to its final lumber products.
A. The Logging Industry
The logging industry includes felling, or cutting down, the timber; cutting it into lengths; and transporting it, usually by truck, to the sawmill. In a well-planned harvest, before the timber is felled, the foresterthe person in charge of managing the forestdecides which trees will be cut and when (seeForestry). These decisions must be made within the context of the forester's overall responsibility for maintaining the quality of the forest as an ongoing resource. The forester and loggers then establish a network of roads and trails on which the timber will be transported. To protect the land, sensitive areas such as wetlands or steep terrain are avoided. Small streams may be spanned by temporary bridges made of logs. The transportation network connects to one or more clearings, called landings, where logs are sorted and piled for loading onto trucks. Landings are located in central locations easily accessed from public or private roads that can support truck traffic.
Loggers generally fell trees with gasoline-powered chainsaws. However, the use of mechanized felling equipment has increased on harvesting operations. Mechanical fellers, consisting of large steel blades mounted on a vehicle, sever the tree at the stump much as a pair of scissors cuts paper. Whether using chain saws or mechanical fellers, responsible loggers plan their cuts carefully to avoid smashing and scarring trees that are to be left standing. Once a tree is down, the logger removes its limbs to make it easier to transport the stem, or trunk.
After the trees are felled and trimmed, the logs are skidded to landings where they can be put on trucks and hauled to the mill. Skidding involves raising one end of the log and dragging it across the ground. Early skidding relied on teams of horses, mules, or oxen. The term skid row, used for a district of cheap saloons and rooming houses, takes its name from early loggers, or skidders, who frivolously spent their low wages in cheap areas of nearby towns.
Animal skidding still occurs in some developing countries and on small woodlots, but wheeled or tracked vehicles have largely replaced animals on commercial operations in North America. Cable skidders are vehicles that pull logs behind them with steel ropes placed, or choked, around each log. A grapple skidder saves time by scooping up a bunch, or hitch, of logs by means of hydraulic arms mounted on its back.
In muddy conditions, wheeled, trucklike vehicles called forwarders may carry logs to landings without dragging them. On difficult terrain and in remote areas, other systems replace wheeled vehicles. For example, on steep slopes in the Pacific Northwest, logs are skidded to a landing by a system of cables and pulleys mounted onto standing trees and driven by a machine called a cable yarder. In remote areas, even hot-air balloons and helicopters may be used to transport logs to landings.
After the trees reach a landing, loggers cut, or buck, them into sawlogslogs that are large enough to be sawed into lumber. At the landing, the logs are scaled and graded. Scaling estimates the number of board feet a sawlog contains. Grading describes the quality of the log, taking into account visible defects such as branch scars or rot. An experienced logger bucks trees in a manner that maximizes the scale and grade. The sawlogs are then loaded onto trucks by hydraulic booms and transported to a sawmill.
Technological advances have increased the speed and efficiency of harvesting through mechanization and reliable equipment that can perform under extreme conditions. Still, logging ranks as one of the most hazardous occupations, and many safety precautions are necessary to avoid injury. Vehicles used as skidders are equipped with rollover cages and seat belts to protect the operator should the equipment turn over or a tree fall on it. Chain saws have safety features that allow quick shutoff in an emergency. Well-equipped loggers wear safety equipment, such as hard hats, ear protection, face screens, and steel-toed boots. Clothing made from the same material used in bullet-proof vests protects them from chain-saw cuts.
B. The Sawmill Industry
At the mill, the sawlog is first passed through a debarkera rotating ring with pressure plates that tear off the bark. Sand and dirt that could damage the saw are simultaneously removed. In what is called the primary breakdown, the debarked sawlog is then placed onto a steel carriage that holds the log and passes it through a circular saw or a band saw, a flexible saw-toothed band of steel mounted onflywheels above and below the log to be cut. The saw removes slabs of wood to produce a rectangular log, called a cant. During the secondary breakdown of the log, the cant is sawed into boards that are trimmed and edged to the desired lengths and widths. This process can increase the value of the lumber by removing defects.
The board lumber is then sorted by species and grade to be dried, or seasoned, either in the open air or in a kiln, a heated drying shed. All lumber must be seasonedthat is, dried slowly and uniformlyto prevent cracking and warping. Finishing methods vary by species and ultimate product. Some lumber is sold rough, whereas some is planed to create a smooth surface. Boards may also be treated with chemicals to prevent decay. Because seasoning and finishing shrink wood, a standard U.S. two-by-four piece of lumber5.08 cm (2 in) thick by 10.16 cm (4 in) wideis actually slightly less than these dimensions.
Milling technologies have sought to increase the amount of lumber sawed from a log, known as the lumber recovery factor. For example, high-grade steels allow for thin saws that make a smaller kerf, or cutting groove, in the log, thus reducing the amount of log lost to sawdust. In addition, modern sawmills now uselaser scanners and computer technology to determine the best cuts for maximizing the value and volume of boards from a sawlog.
C. The Panel Industry
The panel industry uses glues and pressing techniques to turn otherwise unusable logs, branches, and various wood residues left over from sawing into thin, flat panels of wood. Such panels have a wide variety of uses from construction to toy making.
The products of the panel industry areveneer, plywood, particleboard, and fiberboard. Veneer is a thin layer of wood used primarily in plywood manufacture and furniture making. Softwood veneers are commonly produced by heating a log with steam and mounting it to a lathe that rotates it. A roller bar presses the spinning log against a long knife that peels a thin sheet from the log. This action in effect unravels the log. Hardwood veneers are generally sliced rather than rotary cut.
Plywood is composed of several layers of veneer bonded together withadhesives. The veneer sheets are sprayed or rolled with adhesives and then layered so that the grain of one sheet is perpendicular to that of the next. The panels are then pressed at specific temperatures to bind the adhesives and the layers together. Plywood is graded by its durability, strength, visual quality, and resistance to fire and decay. Hardwood plywoods serve primarily for appearance and are not as strong as those made from softwoods.
Particleboard (made of particles of wood) and fiberboard (made of smaller fibers of wood) are manufactured from what are known as composite materialswood residues mixed withresins and wax. Multiple manufacturing methods are used, depending on the final product. In general, raw material is sorted according to form (such as wood chips or sawdust), tree species, and moisture content. Machines grind this material into a range of particle sizes, after which the particles are dried to a prescribed moisture content. The dried particles are then blended with resins and waxes to form what is termed the furnish. The furnish is deposited into a form to produce a uniform mat, which is then cured by pressure and heat. Mats are cooled, sanded, and cut into standard U.S. panels measuring 1.2 by 2.4 m (4 by 8 ft) or into custom sizes for specific manufacturers. Particles are generally laid down randomly in the boards, but oriented-strand boards have particles aligned perpendicularly to each other, resulting in a more durable panel similar to plywood.
III. History of Lumbering
Humans have utilized wood for construction for thousands of years. However, the heaviness of timber and the dependence on manual tools for harvesting and manufacturing prevented large-scale lumbering until the mechanical advances of theIndustrial Revolution.
A. The Colonial Period
The vast stands of old-growth forests in North America were an unprecedented resource to the first settlers from Europe, Africa, and Asia, where many of the forests had been cut for centuries. American pioneers cleared forests for cropland, pastures, and settlements. As early as 1607, settlers in Jamestown, Virginia, began shipping hand-sawed clapboards to England, and lumber exports exceeded domestic demand during most of the colonial period.Shipbuilding ranked as one of the earliest and largest industries in North America. East Coast oaks were used for ship ribs and keels, and pines served as masts and decking. Some of the best white pines of New England were reserved for the British Royal Navy by a broad-arrow mark cut into the trunk by the king's surveyor general.
The early lumber industry relied heavily on water. Logs were floated, or driven, downriver to sawmills, and the sawmills themselves were powered by large wooden wheels turned by the stream flow. Since the flow of water varied with the season, mills were often halted because of flood, drought, or freezing.
B. The Industrial Revolution
Lumber demand soared as the United States developed during the 19th century, and new industrial technology provided the means to supply it.Railroads promoted industrialism in the Northeast and expansion in the West, both of which created a demand for lumber. Meanwhile, the steam engine freed sawmills from their dependence on flowing water and allowed them to operate throughout the year. The high-speed circular saw and the band saw provided a continuous cutting action that improved the output and quality of lumber. Mechanized planers (see Machine Tools), which smoothed rough lumber, also increased production.
Large-scale logging began in New England, where Maine led lumber production during the early 19th century. Typically, timber companies purchased land with the intention of cutting only the best trees or a single species. The logging debris, or slash, generated from a harvest often fueled wildfires that destroyed farms and villages. Loggers systematically cut their way from New England down through the Appalachian states and across the Great Lake states of Michigan, Wisconsin, and Minnesota. Logging reached its peak in the South and rapidly expanded in the far West during the latter part of the 19th century.
The lumber industry still relied heavily on water for transportation of logs, and settlements developed where sawmills concentrated along rivers and ports. While loggers cleared forests that eventually became farmland, sawmills provided the building materials for businesses and homes. Several large cities, such as Chicago, Minneapolis, and Seattle, grew up around the sawmill and lumber marketing industries.
Loggers in the 19th century lived in camps throughout the year. They labored all day, endured extreme weather, and worked under life-threatening conditions. The river drives, in which loggers walked the rolling logs as they floated downstream to the sawmills, were particularly dangerous. The harshness of the occupation and the hardiness of the men inspired many stories and songs. Loggers were romanticized in American folklore with such legendary characters as the powerfulPaul Bunyan and his giant blue ox, Babe.
C. The 20th Century
Large-scale logging of the nation's forests without concern for the future continued into the 20th century, and by then most of the original old-growth stands of trees had been cut. However,conservation of forests was bolstered when the federal government established the Division of Forestry in 1885 (see Forest Service) and authorized forest reserves in 1897. Some industry leaders realized as well that the once "endless" supply of big timber would soon disappear and in the 1920s began to purchase land to grow timber for the future.
The economic boom following World War II fueled lumber demand, especially for building suburban homes. During this time, some lumber companies and even public forests developed intensive forestry operations by growing single-species plantations and maximizing their production with fertilizers, herbicides, and pesticides. However, at the same time, more people were becoming environmentally conscious. No longer were forests viewed only as sources of timber; they became valued as sources of recreation, clean water, wilderness, and biodiversity. Recently, environmental concerns over lumbering have intensified, particularly regarding public forests, which many people wish to preserve as wilderness areas, especially those containing old-growth stands of trees.
Exploitative logging still occurs, damaging the reputation of conscientious members of the lumber industry. However, both lumber industry leaders and environmental advocates are working to prevent the destruction of forests and to protect the forest environment during logging. Many lumber companies have adopted what are known as best management practices, which prescribe methods for protecting the forest environment during harvesting operations. For example, a buffer zone of 50 feet around streams is not logged in order to protect stream ecology; waterbars, or trenches, are dug at right angles across logging roads to divert water from running down the roads and eroding the soil; and skid trails are reseeded with grass after a logging operation has been completed. State and federal regulations have made certain harvesting activities, such as operating in wetland areas and in endangered species habitats, illegal or subject to approval. Some environmentalists have used the judicial system to halt logging, particularly on public lands. Foresters have searched for creative solutions to minimize the visual and ecological impacts of harvesting while producing timber in a sustainable manner. In addition, markets have developed for certified lumber products guaranteed to have come from sustainably managed forests.
The efficacy of all these actions has been hotly debated from both emotional and scientific perspectives. At issue is the balance between private property rights, the jurisdiction of government to regulate industry, and the long-term, sustainable use of natural resources on a global basis.
P. Gregory Harris, B.S., M.F.
Manager, Yale School Forests.
HOW TO CITE THIS ARTICLE
"Lumber Industry," Microsoft® Encarta® Online Encyclopedia 2000
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