Between the period when a crop is established and the first harvesting operation (first thinning) there are a number of tasks that are carried out to allow access to the crop and improve tree form and wood quality. These operations are collectively known as tending.
Brashing is the removal of the lower branches of conifer trees usually up to a height of 2 metres. It is normally carried out to gain access into a plantation when the crops reach the late thicket stage prior to the first thinning. Brashing is carried out using a pruning saw or light chainsaw. Not all trees are brashed, only those necessary to allow access for the inspection of the crop or the measurement of timber volume.
Brashing is not required in broadleaved plantations due their lighter canopies and reduced branching from previous shaping operations.
FORMATIVE SHAPING OF BROADLEAVES
Conifers species have a tendency to grow with a very definite leading shoot resulting in trees with straight stems. Broadleaves, however, have a different growth habit and being less apically dominant are prone to forking and the production of large heavy branches which can result in trees with poor quality timber.
Formative shaping is therefore carried out in the early years of broadleaved crops to ensure straight stems with a single, leading shoot through the removal of competing shoots. As well as encouraging the growth of a straight leading shoot, formative shaping also removes heavy side branches. All branches cause knots and the larger and more plentiful the branches the more knots will be present causing a reduction in timber strength, quality and value.
Formative shaping is carried out using secateurs or loppers and generally commences when the trees are between 1.0-1.5 m in height and continues as required, until the crop reaches 3.0 m or more. Particular attention is needed during the first few years, especially on fertile sites where vigorous growth takes place.
As a tree grows in diameter the base of its branches become included in the stem. These form knots in the timber which can cause distortions in the grain of the wood (live knots) and/or holes where dead branches become detached from the surrounding wood (dead knots). In either case knots lead to a reduction in the quality and strength of the timber.
The size and frequency of branching can be controlled through proper planting densities but pruning or the removal for the dead and lower live branches of a tree can also be used to improve wood quality. Pruning is carried out on trees that will from the final crop and is normally carried out in two stages called lifts. The first lift is carried out around the time of the first thinning, and the second applied 5 to 10 years later. In sessile oak, pruning may be repeated later on during the rotation, if epicormic branching occurs.
Pruning is normally carried out using a saw attached to the end of a long pole. Specialised pruning machines have been developed for use on species with straight regular stems. These machines climb up the tree to the required height, removing branches as they go.
Pruning is generally carried out on trees that will be used for higher value end uses such as transmission poles, joinery, furniture etc. The preferred species for pruning are fast growing stands of Douglas fir, spruce and pine and all of the commercial broadleaves.
Further information at: Pruning adds value to plantations