GROWTH, BIOMASS ALLOCATION AND FOLIAR NUTRIENT CONTENTS OF 2 EUCALYPTUS SPECIES OF THE WET DRY TROPICS OF AUSTRALIA GROWN UNDER CO2 ENRICHMENT

1. Seeds of Eucalyptus tetrodonta and E. miniata were sown in duplicated air-conditioned tents which were ventilated with either ambient or CO2-enriched (700 mumol mol-1) air. Growth, foliar nutrient content, soluble protein and biomass allocation were investigated over the subsequent 32-week experimental period. 2. It was found that CO2 enrichment significantly increased the total biomass and tree height of E. tetrodonta, but had no effect on total biomass or tree height of E. miniata. 3. Allocation of biomass to main-stem wood and main-stem leaf mass increased and allocation to branch wood and branch leaves declined, under CO2 enrichment for E. tetrodonta. No change in allocation patterns for E miniata was observed in response to CO2 enrichment. 4. Foliar nitrogen, manganese and phosphorus contents were decreased under CO2 enrichment in E tetrodonta, but there was no effect of CO2 concentration in E. miniata. Soluble protein contents were not affected by CO2 enrichment in either species. These results are discussed in relation to the competitive relationship between these two species in northern Australia.