Physiological and growth responses related to pattern and severity of green pruning in young Eucalyptus globulus
2003
Pinkard, E.A.
Eucalyptus globulus (Labill.) is grown for a variety of purposes that require removal of some of the foliage from a young age, such as oil production and floral supplies. Often these uses are a sideline to the main purpose of the plantation which is to grow timber. If plantations are grown for solid wood production, pre-canopy closure removal of large branches or forks may be necessary to improve stem form and wood quality. An experiment was established to determine the appropriate severity and pattern of pruning that would allow foliage removal in pre-canopy closure plantations without reducing stem growth. It was found that removal of as little as 20% of leaf area reduced stem volume, although more severe pruning was possible on high productivity sites. The growth responses to pruning were moderated to some degree by increases in levels of net CO2 assimilation. Light-saturated CO2 assimilation (A(max)) increased with pruning severity. Pattern of pruning had a substantial effect on A(max), but there was little difference in stem growth following removal of a selection of branches from throughout the crown or removal of all branches to a predetermined stem diameter. From a wood quality perspective removing all branches to a predetermined stem diameter was more appropriate than selective branch pruning, because it reduced the number of dead branches. However, pre-canopy closure pruning had no effect on branch diameter increment except at severe pruning levels on high productivity sites. It was concluded that it should be possible to combine early foliage removal with production of solid wood from E. globulus plantations, provided leaf area removal is around 20%, or 40% on high productivity sites.
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