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Managing individual trees for sawlogs
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  Managing individual trees for sawlogs

Timber production is only one reason farmers establish forests and plantations. Many farmers manage mixed species or mixed age forests to produce a range of products and services. For these farmers it might be more viable to manage individual trees within their forest for timber rather than the whole plantation. The emphasis must be on high quality to ensure that trees are viable to harvest. Pruning, culling and managing competition from other trees in their forest will help ensure a viable harvest.

Promising trees located in areas with easy access for harvesting could be pruned. Immediately after each pruning it is important to make sure the tree is under competition from adjacent trees or vegetation for light, water and other resources. Examining the forest canopy is the simplest way to assess competition. If the pruned tree is overtopped by nearby trees, then those trees should be culled. Another relatively simple way to assess competition is to use the spacing factor. The aim is to ensure that the selected tree’s canopy can develop freely.

If, for example, the farmer wanted to reduce the competition in their forest down to a basal area of 10 m2/ha to promote diameter growth the spacing between trees of a similar diameter would need to be about 30 times the diameter. For example, if the trees were all around 15 centimetres in diameter, then culling any tree within 4.5 metres—15 cm x 30 cm = 4.5 m—would reduce the basal area to less than 10 square metres per hectare. As the trees grow they will require more space.

In a mixed-age forest, where the trees are different sizes, the same technique can be used to determine if a large tree near the selected tree should be culled. If it is located within 30 times its own diameter, then it might be assumed to be competing with the selected tree. For farmers comfortable with using a basal area wedge, assessing competition levels is simple. A farmer stands beside the selected tree, estimates the basal area using the wedge—including the selected tree in the count—and can use this as a measure of the level of competition affecting that tree. If it is more than the desired level of competition for the species on that site, the sweep could be repeated excluding trees that might be culled.

Tree and forest measurement

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