Growth of Eucalyptus delegatensis following partial harvesting of multi-aged stands

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Abstract
This paper reports the results from an experiment in partial cutting conducted in 12.7 ha of multi-aged stands of E. delegatensis situated on private property in central Tasmania. The objective of management is to maximise sustained yield of sawlogs, with a variable yield of pulpwood. Following a precise survey of the positions of all trees greater than 20 cm dbh, the stands were partially cut. Nearly all trees that were sound, of good form, and therefore considered likely to appreciate in value, were retained; defective and overmature trees were removed regardless of size. The degree of release of retained trees was calculated as the change, before and after felling, in a competition index that was derived from the relative size and distance apart of subject and competing trees. Regression analysis of diameter increment against per cent reduction in competition index explained 63 per cent of variation in growth in trees less than 30 cm dbh, but less than 15 per cent variation in growth in trees greater than 50 cm dbh during a four year period. Trees less than 40 cm dbh were both more susceptible to suppression and more responsive to release than were larger trees. In all size classes trees with the more healthy crowns grew much faster on average than those with less healthy crowns. For one defined scenario of management, calculation is made of the potential productivity of the stands assuming ideal size distribution and spatial distribution of trees.