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  Sawlogs without pruning



Throughout most of Australia conventional pine plantations focus on producing sawlogs with small branches that are suitable for structural timber. Competition, rather than manual pruning, is used to control the branch size. To prevent competition slowing growth to a halt, or threatening the forest’s stability or health, several thinning operations are undertaken to reduce the basal area. Where possible, pulp or other small diameter products are produced from the thinning operation to help cover costs.

But farmers may put themselves at risk when they adopt these regimes. If there isn’t a viable market for the thinnings when thinning is required, the whole investment might be at risk. Overstocked plantations under excessive competition are susceptible to drought, diseases, insects and wind. Diameter growth on the best trees can slow to a halt as the plantation becomes locked up. In eucalypts, thinning in dense stands can also lead to severe epicormic shoot development—that is, shoots sprouting up the stem—as the trees try to rebuild a canopy after a period of intense competition.

It is common for farmers to consider postponing the first thinning until the trees are large enough to provide a commercial return. However, experience suggests that farmers with small plantations should be cautious about assuming they will be able to negotiate a commercial thinning. To be viable the plantation must be relatively large, easily accessible and close to markets. The machinery required to efficiently harvest, delimb, debark and load small diameter logs efficiently is expensive. Few farmers have access to this equipment and—because of the small volume of timber involved—many find themselves unable to attract contractors. Cheap culling methods—for example, stem injection and ring barking—offer a cheaper method of thinning to waste for farmers who want to use competition to control branch development in their plantations or native forests. These methods enable farmers to maintain competition at a level required to encourage self-pruning. They can then thin repeatedly to maintain diameter growth.



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