Growth response pf mixed species eucalypt regrowth in East Gippsland 7 years after early spacing treatments.  Y. Wang, P. C. Fagg and F. Hamilton.  June 2002.  9pp. (unpubl.)

SUMMARY

Data from the permanent plots established in an early spacing (pre-commercial thinning) trial was analysed to examine the growth responses 7 years after treatments. The trial was established in a 9-year old mixed species regrowth stand dominated by silvertop ash (Eucalyptus sieberi) near Cann River, East Gippsland. Growth estimates determined from the measurements taken post-thinning in 1992 and in 1999 were compared for three spacing treatments and the untreated control.

In general, all three spacing treatments resulted in improved growth of the crop trees due to the reduction of high competition in the early stages of stand development. There was some indication that the spacing treatments, which combined corridors and selective spacing using clearing saws or chemical stem injection might increase the merchantable yields in the treated stands. However, in the future, this needs to be further investigated in terms of product volumes.

The comparisons of the three spacing techniques showed that the non-selective mechanical spacing of corridors combined with the selective spacing using chemical stem injection (Corridor + stem injection treatment) or clearing saws (Corridor + clearing saw treatment) were superior to the Corridor spacing only. The Corridor + stem injection treatment resulted in a mean annual diameter increment of 1.2 cm over the 7 year period, compared with 0.9 cm for the Corridor + clearing saw treatment and the untreated control of 0.7 cm.

Because of the significant cost advantage of the Corridor + stem injection over the Corridor + clearing saw treatment indicated by Kerruish et al. (1993), the Corridor + stem injection is the favoured technique of those trialled. The option of stem injection alone was not included in this trial, but based on other data, it is likely to be the most cost-effective method of early spacing.