Science Fair Project Encyclopedia
- For another article about a different type of logging, see data logging.
Logging is the practice of cutting down trees, then cutting out their central boles (the clear trunk or central stem) and possibly branches in order to use the wood directly or to market it as an economic resource. Standing trees viewed as a potential economic resources are termed timber.
Most conventional logging is either for pulpwood production for the manufacture of paper products or for sawlogs for lumber production. In the United States, standard sawlogs are sixteen feet long. Trees may be referred to as "two-saw-log-trees", for instance, meaning that they have a clear bole for at least 34 or so feet (allowing for the remaining stump).
A significant amount of logging is also done for firewood production, and, today, a very large and growing amount of logging is being done for chipwood production.
There are several methods of logging. The most common in commercial operations is clearcutting, a practice that removes essentially all the trees in a selected area. In clearcutting for lumber production, where the logging is done in a mixed-age forest, all the large trees are taken and the saplings and smaller trees may be left for regeneration. In the case of a pure-age stand, such as a tree farm, or in certain mature forests, such as some of the virgin Douglas-fir stands of the West, virtually all trees are cut.
There are two principle variants of clearcutting. In the first, just mentioned, all marketable trees are removed and trees too small for market, including saplings, are left. However, clearcutting in the case of pulpwood production usually involves cutting away all woody plants, often producing a "shaved" effect. This may be also true in the case of chipwood production. This type of clearcut area takes a longer time to regenerate forest and suffers more erosion than does mixed-stand clearcutting that leaves younger trees intact.
There are supportable claims that clearcutting can be an ecologically healthy forestry practice, mimicking the effects of a natural disturbance. However, clearcutting is also the most economically-efficient way to remove timber. Obviously, large poorly planned clearcuts are far more destructive than cuts that take into consideration natural topography, and bioregions. The effects of sustainable clearcutting can mimic the effects of a forest fire or other natural disturbance in a number of important ways. Conscientious logging will leave standing snags and small "residual patches" for wildlife, and organic matter such as "slash piles" of unusable material are left on-site as ash to fertilize the soil or as partly-burnt wood that will quickly decay into the soil. If logged on frozen ground with lighter machinery, or even horses, the ground can be left generally undisturbed and unbroken which can let groundcover regenerate quickly. In the case of a poorly planned larger (over 1 km²) clearcut, there are few or no residual patches or wildlife snags left behind and the ground will be highly disturbed and compacted; erosion and poor forest regeneration will result.
A critical problem with poorly operated forestry practices, especially in the eastern North American hardwood forests , is the problem of colonization of the forest area by invasive exotics. In a normal, intact forest, or even in a carefully-managed woodlot, such species find it very difficult to gain a toe-hold, but clearcutting opens up the land to large-scale colonization by such species as Japanese Honeysuckle, Multiflora Rose, Kudzu, Oriental Bittersweet , Garlic Mustard, and other species which take over the ecosystem and displace other plant species and dependent animal species.
Selective logging vs. clearcut logging
Selective cutting is the practice of only taking certain trees that are deemed the most desirable for harvest, and leaving the rest. This is a practice most often engaged in by woodlot owners who wish to sustain their timber yield. However, only the largest, most commercially viable trees are cut, leaving younger trees and non commercial trees to continue to grow. For instance, trees that were originally open-grown have much lower value for lumber than do forest-grown trees, and strongly cross-grained trees such as elms tend to be avoided for firewood production. A particular type of selective cutting that targets only the highest-quality trees of certain species is termed high-grading, which ultimately results in much lower-quality woodlands.
This is a problem with selective logging, in that it tends to harvest the best trees, removing them from the seedstock, producing an evolutionary pressure towards lower quality. In coniferous forests a larger "clearcut" that removes all trees in a given area will regenerate into a healthier forest than if it was selectively logged. Most tree species require large amount of light to grow therefore, trees will grow faster in an open area than in a gradually "thinned" forest.
Forest regeneration, silviculture and biodiversity
In clearcuts where natural regeneration is poor, sound forestry legislation will demand that a logging company plant seedlings to aid the natural regeneration of the forest. Some argue that treeplanting leads to a "monoculture" forest which destroys the biodiversity of the area. This however is not usually the case. Most seedlings used in reforestation come from the seeds found in the recently cut forest as these trees are naturally adapted to the area. In many areas multiple species will be planted according to the smaller ecoregions of the cutblock ie) lodgepole pine, white or black spruce, cedar, etc.
Riparian strips or zoning is an important forest management practice in which trees are left standing along waterways to protect the banks and water quality. Failure to do so historically has exacerbated flooding, erosion and siltation, and caused local extirpations of sensitive plant and animal species. Some of the most marked effects of large-scale clearcutting, including the stream corridors, has been seen in the American Pacific Northwest, where salmon streams have been completely destroyed in terms of their salmon-supporting capability, and local populations of salmon and even subspecies have become extinct as a result.
The negative portrayal of logging by the media and popular culture
The logging industry is often portrayed in the media and popular culture as one of the most ecologically destructive corporate practices on earth. Though there are some notable cases of severe environmental degradation by greed-motivated large multinational logging operations, the truth remains that agriculture, livestock grazing, mineral mining, the petroleum industry and urban sprawl are even greater contributors to deforestation and ecological degredation. For example, a house built out of steel, plastic and concrete requires more energy and non-renewable resources to produce than a house built with wood products. However, destroying high gradient forest ecosystems is the result only of questionable timber sales sold at a loss by the U.S. Forest Service i.e. American taxpayers without enough regard to ecosystem health and endangered species such as salmon. The roads required further degrade the system long after the timber is gone.
When logging and the art of forest management is performed in a conscientious manner, it provides humankind with one of the greatest sources of renewable and ecologically sustainable energy. Paper, dimensional lumber, fibreboard, particleboard, furniture, utensils, a hydrocarbon fuel source, recreational areas, animal habitat, and clean air are just some of the benefits of the world's forests.
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