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  Sawlogs with pruning

Pruning reduces the time it takes to grow large logs and increases the quality of logs. Experience suggests that pruned eucalypt plantations might be able to reach an average diameter of 50 centimetres in half the time of conventional plantations. This is because pruning allows farmers to space their trees wider apart therefore allowing for faster diameter growth. Unpruned plantations need to be held at higher stocking rates to control branch development.

Because they are under less stress, the trees in these plantations may also be less susceptible to drought or disease. It is common in plantation forestry to plant more trees than are expected to be harvested. This provides mutual shelter for the young trees and helps control tree form and branch growth. It also allows selection so that all the final crop trees are of high quality. For example, if the aim is to grow a plantation of at least 100 perfectly straight high pruned eucalypts per hectare, the farmer might establish more than 600 stems per hectare. As the plantation grows, the better performing trees are selected for the first pruning—for example 400 stems per hectare of the most vigorous straight trees—and the remainder are culled. The following season, the best 200 stems per hectare might be selected for a second prune and the others culled. Finally the best 150 stems per hectare might be high pruned to the final height and the others culled. The trees are then left to grow on with 50 trees in reserve in case of disease or wind damage.

Farmers growing a more tolerant species, such as exotic or native pines, might choose to aim for around 200 stems per hectare. To achieve this, they would establish 800–1000 stems per hectare. If they were confident that the trees would not require early shelter and growth, and would be very uniform, they might be able to plant fewer trees initially.

Publicly available data for eucalypt plantations up to age 40 years from Australia and New Zealand. The data shows that pruning might allow growers to reduce the rotation length.

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