The effect of time of sowing on eucalypt regeneration success following direct sowing onto disturbed soil in the high elevation mixed species forests of East Gippsland.  M. T. Lutze, O. Gourley and R. More.  February 1998.  47pp. (unpubl.)

SUMMARY

The time of sowing of high elevation mixed species (HEMS) forest is an important factor in the success of regeneration. This study was undertaken to determine the best time of sowing for the germination, survival and early growth of seed sown on mechanically disturbed seedbeds. The objectives of the trial were to:

• observe and understand regeneration processes;
• evaluate the effect of time of sowing on eucalypt regeneration success in terms of early stocking (no. stems/ha) and height growth of established seedlings; and
• recommend guidelines for sowing time under operational conditions.

Plots were raked and sown with a pre-determined quantity of seed during March, April, May and August 1991 at two sites prepared by machine. These sites had been logged and slash-burnt several years previously, but had failed to regenerate satisfactorily. Sowings were repeated during January, February, March, April, May, June and August 1992 at another two backlog regeneration sites. Germination, survival and height growth were monitored monthly up until July of the year following sowing. It was found that:

• Germination patterns varied widely with species, site and timing of sowing. Peaks of germination occurred in autumn and early spring with some germination in the mild summer of the year 91/92. Winter germination was limited and subject to heavy mortality. denticulata apparently germinated later than other species.
• Survival of germinants varied with time of germination, site and season. Winter mortality following autumn germination was heavy. Survival following spring germination varied with the season , but was clearly superior to that of autumn germination in the circumstances of the present study. Summer germination under mild weather conditions followed by rapid autumn growth led to reasonable rates of survival.
• Height growth of the tallest seedlings per plot was similar for both autumn and spring germinants. Browsing was a major factor limiting height growth and varied widely between coupes. Height growth was very poor in coupes where plots were hand-raked and sown approximately one year after the surrounding areas had been regenerated.

For the site preparation sequence followed in this study the success of different sowing times varied between sites. However, on balance, winter sowing followed by spring germination gave the highest stocking and height growth equal to or greater than autumn sowing. The following factors contributed to this result:

• sowing at a time that minimised the period between sowing and germination maximised germination percent;
• spring germination reduced mortality due to the main adverse environmental conditions in HEMS; and
• sowing in the period June to August increased the chance of spring germination and minimised the period between sowing and germination which led to an increased chance of attaining adequate stocking of eucalypt seedlings with acceptable competitive position.

The findings support the current prescription of sowing HEMS forest in winter.

The effect of greater competition in routine coupes prepared by slash-burning compared to backlog regeneration sites is discussed.

Recommendations are made about future research and the operational application of the results of this study of time of sowing in HEMS.