4.6. Pruning regimes
Pruning can be carried out in different ways that
have trade-offs in terms of labour costs and control of
the size of the knotty core. The most appropriate
regime will be dependant on the cost of labour and
the value of the clear wood produced. Fixed lift
pruning (FLP) is the simplest regime. It involves
pruning to a fixed height (typically 2.0–2.5 m in the
first lift), with operations scheduled by age or the
mean dominant height of a stand. In FLP regimes, all
trees are pruned to the same height, regardless of
variations in individual tree size (Fig. 3). As a result,
the DOS and proportion of crown removed will vary
depending on tree size. This may have implications for
subsequent tree growth if the stand growth is variable.
By contrast variable lift pruning (VLP) uses tree
size criteria to determine the extent of pruning. A tree
is pruned up to a minimum stem diameter or to a set
proportion of tree height or crown length (Fig. 3)
(Koehler, 1984). The main benefit of VLP over FLP
is that there is more control over DOS of individual
trees.