Regeneration of high elevation, mixed species eucalypt forests in East Gippsland.  P. C. Fagg.  May 1981.  75 pp. (unpubl.)

SUMMARY

High elevation mixed species (HEMS) forests in East Gippsland (dominant species Eucalyptus obliqua L’Hérit (messmate stringybark) and E. fastigata Deane & Maiden (cut-tail) have proved difficult to regenerate after logging. This study, undertaken at five sites in the HEMS zone during 1974-1979, was initiated to identify and quantify the factors contributing to seedling germination, mortality and establishment, with a view to recommending successful regeneration techniques.

Seedbed type was found to be the most important factor affecting establishment of seedlings. Sowings on disturbed mineral soil yielded a significantly higher seedling per cent after three to four years then did sowings on ‘burnt’ soil (i.e. seedbeds produced by various intensities of slash-burn), with 5.0 ± 0.9% compared with 1.7% ± 0.7% seedling yield.

Seedbeds disturbed in March, April or May yielded the best seedling percent when sown in April, May or August. Sowings in June and July were not tested but are also expected to be successful. January, February (one site only) and March (three sites) sowings yielded lower seedling per cents than the April-August sowings, and October (two sites) sowings were unsuccessful.

Seedbeds prepared by slash-burning in March and sown between March and October generally yielded low final seedling per cents (< 2.0% ). Low survival rates on many burnt seed beds were attributed to suppression of the small eucalypt seedlings by mat-forming native weeds, though other seedling deaths on these beds were difficult to explain. Seedling mortality on disturbed soil seedbeds appeared to be mainly due to competition from woody weeds and/or other seedlings, animal browsing and trampling, the freezing of tissues, and high soil temperatures and/or local soil drought. Browsing by rabbits and wallabies was locally severe, and control measures for this need to be evaluated.

Height growth was not significantly different on burnt and unburnt seedbeds after three to four years. ‘Ash-bed effects’, producing enhanced growth, were obtained, but were confined to only 10% of the burnt study plots.

Although seedbed preparation by slash-burning is initially cheaper than methods involving soil disturbance, e.g. rough-heaping, it carries a much higher risk of regeneration failure. Thus the application of practices that produce increased amounts of soil disturbance are likely to lead to a higher regeneration success rate. An increase in the proportion of disturbed soil area on a coupe from 20% to 65%, as obtained by rough-heaping, would cost up to $110 ha^-1; though this expense could be offset by up to $40 ha^-1 due to the lower sowing rate required to obtain satisfactory stocking.

Some avenues of further research are suggested.