How Trees Are Cut Down & Transported to Saw Mills

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Trees harvested for lumber are stored at sawmills for processing.
Trees harvested for lumber are stored at sawmills for processing. (Image: scierie image by herreneck from <a href='http://www.fotolia.com'>Fotolia.com</a>)

Lumber is produced by processing raw timber at saw mills. Trees are cut down in approved lumber harvesting areas and loaded onto trucks or made into barges for transport. Once they arrive at the sawmill, they are sorted for processing. There are a number of ways these trees are harvested and processed, once a logging company has gotten approval to harvest lumber.

Selection

Lumber can only be harvested from areas approved by a nation's forestry council. Loggers must apply for yearly quotas from specific areas. Once a quota is approved, the company may begin logging. Ordinarily, all trees within the approved area above three inches in width are cut down.

Felling and Limbing

The trees will be cut down either by hand, using a chainsaw, or using a large machine called a "feller buncher," which is similar to a backhoe, but instead of a shovel, has a grasping assembly with circular saws at the bottom. The assembly grasps the tree firmly, cuts through the trunk, and then lays the felled tree on the ground. The tree branches are then removed with chainsaws, a process called "limbing."

Loading

If the logging site is near a river, the limbed trunks are dragged to shore, where they will be arranged for floating. At logging sites away from rivers, they are loaded onto the backs of waiting semi trucks by log loaders, another backhoe-like piece of machinery with a specialized hydraulic assembly on the end of its arm. The log loader's assembly is designed to simply grip and lift tree trunks. These machines are able to lift and carry tremendous weight while retaining 360 degree mobility with the loading arm.

Transport

For riverside logging camps, transport is often still done by creating log barges. Since wood floats, all that is needed to form a log barge is an enclosed area on the water's surface. Most of the time, some of the logs themselves are chained together to create this enclosure. These log barges are them either floated downriver or pulled upriver by a tug boat to the sawmill. Logs transported over land are loaded onto a special type of semi trailer. At the front and rear of the trailer are strong metal brackets with vertical arms between seven and ten feet tall. The rear wheels of the trailer are connected to the front of it by a single metal beam, since there is little weight to be supported by a truck bed. The rear wheels on trailers for exceptionally long logs are not connected at all. Instead, they are tightly chained to the bundle of logs.

Logs are transported over land using specialized semi trailers.
Logs are transported over land using specialized semi trailers. (Image: log truck 2 image by Jim Parkin from <a href='http://www.fotolia.com'>Fotolia.com</a>)

Unloading

At river-based sawmills, the log barges are chained to heavy cement pylons upriver from a receiving area. The logs are then gradually allowed to float downriver into the receiving area, where they are guided onto toothed chain belts that pull them out of the water and into the sawmill proper. At landlocked sawmills, the logs are unloaded from the semi trailers by another log loader and stacked in piles organized by log width. A forklift with a grasping attachment will return for individual logs when that size of log is being processed by the sawmill.saw

Logs are sorted by trunk size at the sawmill.
Logs are sorted by trunk size at the sawmill. (Image: scierie image by dominique touchard from <a href='http://www.fotolia.com'>Fotolia.com</a>)

Reforesting

The last stage of lumber harvesting is reforestation. Loggers are generally required to plant more trees than they harvested, to ensure that we don't run out of forest. The exact number of trees replanted varies, but some logging companies plant up to 20 tree for each tree cut down. The logging company must ensure that at least as many trees as were cut down survive to adulthood.

Logging companies must replace the trees they've harvested.
Logging companies must replace the trees they've harvested. (Image: reforestation image by Greg Pickens from <a href='http://www.fotolia.com'>Fotolia.com</a>)

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