EFFECTS OF GREEN PRUNING ON GROWTH AND STEM SHAPE OF EUCALYPTUS NITENS (DEANE AND MAIDEN) MAIDEN

An experiment was established in two high quality Eucalyptus nitens De ane and Maiden (Maiden) plantations in Tasmania. At the start of the e xperiment the trees were three years old and the plantations were on t he point of canopy closure. Selected trees were pruned to remove 0, 50 % or 70% of the lower green crown length, and each was surrounded by e ight unpruned trees. The 50% treatment had no impact on height or diam eter increment in the two years following treatment, but removal of 70 % of the lower crown length resulted in significant decreases in both height and diameter increment. There were no changes in the height of 50%-pruned trees relative to the height of surrounding unpruned trees (relative height), and it was concluded that dominance would not be af fected by this treatment. The relative height of 70%-pruned trees was less at one site, and this treatment may result in loss of dominance. Stem taper was generally unaffected by either pruning treatment. Chang es in stem form were restricted to trees in the 70% pruning treatment and were only transient. It was concluded that removal of 50% of the l ower green crown length is an appropriate level of pruning for the spe cies provided that growth rates are rapid and pruning is timed to coin cide with canopy closure. Since dominance was unaffected by this level of pruning, thinning at the time of pruning is unnecessary. It may be possible to minimise the impact on growth of higher levels of pruning by thinning at the time of pruning.