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Silviculture / Silvicultural Examples for timber Plantations / High volume production regimes
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  High volume production regimes



To maximise timber volume production, intensive site preparation and high stocking rates are used to encourage early canopy closure and to generate high basal areas. This high level of competition has the advantage of minimising each tree’s canopy area thereby reducing the size of the branches and ensuring that most of the wood is produced in the stems. The most appropriate initial spacing is determined from knowing the mean tree diameter required for economical harvesting and processing, and the likely basal area at the time of harvest.

For example, if the basal area of a eucalypt plantation at age ten is expected to be 20 square metres per hectare, and the farmer would like the mean tree diameter to be 20 centimetres, the final stocking rate would need to be about 640 stems per hectare. Allowing for some losses, the farmer might choose to plant 700 stems per hectare, spaced at approximately 3.5 x 4.0 metres. On a high quality site, where the final basal area might be expected to reach 30 square metres per hectare, the same mean tree diameter would require 955 stems per hectare. In this case an initial stocking rate of 1111 stems per hectare, spaced at approximately 3.0 x 3.0 meters might be used.

Maximum tree height and the basal area are largely a function of site quality so only the best quality sites are able to achieve very high volume yields. Sites with cool climates and deep fertile soils that receive more than 1000 millimetres rainfall per year are ideal and excellent production levels are possible. However, with many more marginal sites being planted to pulpwood plantations, it is common to find that although early growth is excellent the plantations soon "hit the wall" as basal area and height reach their limit. When this happens, the growth of any tree in the stand must be compensated for by the death of others. Unfortunately, many plantations reach their limit at an early age with little prospect of commercial pulpwood production.



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