Logging

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 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 have long been claims that clearcutting is a healthy forestry practice, mimicking the effects of a forest fire. However, clearcutting is most likely done because it is the most economically-efficient and thus profitable way to remove timber. Obviously, the "shaving" method is far more destructive than the conventional timber-production method.

The effects of clearcutting differ markedly from the effects of a forest fire in a number of important ways. In the case of a forest fire, many standing snags are left for wildlife, and the organic matter is left on-site as ash to fertilize the soil or as partly-burnt wood that will quickly decay into the soil, and the ground is generally intact, or left unbroken, to quickly regenerate groundcover. In the case of a clearcut, especially for pulpwood or chipwood, all woody matter is removed, depleting the ambient stock of organic matter, and the ground is both severely broken, resulting in serious erosion, or compacted, retarding the recovery of any plant life in those places.

Another critical problem with clearcutting, 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 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. Presumably, only the largest trees are cut, leaving younger trees to continue to grow. However, certain trees are always more desirable for either lumber or firewood production, so there tends to be a bias in the cutting. 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 logging in general, and in particular high-grading, in that it tends to harvest the best trees, removing them from the seedstock, producing a de-evolutionary pressure. In the ideal selective cutting, a few of the best trees of each species would always be left as seedstock, and a few of the least desirable trees would be girdled and left for dead as snags for use by wildlife.

Riparian strips are where 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.

See also:

• Illegal logging

• NASA Earth Observatory
• The Causes of Deforestation
• Movie of logging in Maine, 1906