INFLUENCE OF FUEL REDUCTION BURNING AND FERTILISATION ON THE GROWTH AND NUTRITION OF EUCALYPT SEEDLINGS

Abstract

The effects of long-term prescribed burning and N and P additions on tree
seedling growth, nutrient concentration and nutrient uptake were evaluated. Two eucalypt species were grown under glasshouse conditions on potted topsoils collected from two recurrently burnt forests in subtropical Queensland. Annual burning for 42 years and biennial burning for over 20 years had no significant effect on biomass production of four-month-old Corymbia variegata and Eucalyptus pilularis seedlings respectively. However, annual burning did increase P concentration and uptake in C. variegata seedlings. Biennial burning decreased the N concentration but not N uptake of E. pilularis seedlings; P uptake was unaffected by burning. Biomass production of C. variegata seedlings grown on unburnt soil increased with added P and N + P; seedling
growth on the annually burnt soil improved with N and N + P additions. In annually burnt soil, N is more limiting while in unburnt soil, P is more limiting. Only the combined application of N and P significantly increased the biomass production of E. pilularis seedlings, indicating that both nutrients are limiting growth irrespective of burning treatments. Long-term burning may have significant impacts on the N and P nutrition of recruited eucalypts of successive stands.