Effects of seedbed type on early height growth of silvertop: a case study.  M. T. Lutze and G. R. Featherstone.  June 1999.  12pp. (unpubl.)

SUMMARY

A study was established to investigate the effects of different seedbed types on the height growth of silvertop (Eucalyptus sieberi) trees up to five years of age. The study plot was located in a coupe logged during 1975-76 near Cann River in East Gippsland, and regenerated following a regeneration burn in May 1976, relying on burning to induce seedfall from retained seed trees. Measurements of initial seedling density and early height growth of selected dominant and co-dominant seedlings on six types of seedbed ranging from 'hot burn' to 'unburnt/undisturbed', were carried out during 1977, 1979 and 1981.

Analysis of the results showed that:

• Seedling density at age 17 months did not significantly affect the height at age 60 months (five years) or height increment on any of the seedbed types.
• A significant 'ashbed effect' was measured in terms of mean height of selected seedlings after five years on the hot and medium burn seedbeds, compared with the unburnt/loose seedbeds.
• At five years, mean tree height on the hot burn (8.0 m) was 36% greater than that on the unburnt/loose seedbeds (5.8 m). Trees on hot and medium burn seedbeds are considered to be more likely to become future crop trees than those originating on other seedbed types.
• However, for the period 33-60 months after burning, trees on all burnt seedbeds, and unburnt (loose or compacted) seedbeds had comparable growth rates. After five years, the trees on hot burn seedbeds had reached a constant 15-month time-lead over trees on unburnt/loose seedbeds.
• The time-lead for medium and light burn seedbeds was less than 15 months but was still increasing after five years. Some reasons for these trends are suggested.