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 duplicat ed air-conditioned tents which were ventilated with either ambient or CO2-enriched (700 mumol mol-1) air. Growth, foliar nutrient content, s oluble protein and biomass allocation were investigated over the subse quent 32-week experimental period. 2. It was found that CO2 enrichment significantly increased the total biomass and tree height of E. tetro donta, 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 i ncreased and allocation to branch wood and branch leaves declined, und er CO2 enrichment for E. tetrodonta. No change in allocation patterns for E miniata was observed in response to CO2 enrichment. 4. Foliar ni trogen, manganese and phosphorus contents were decreased under CO2 enr ichment in E tetrodonta, but there was no effect of CO2 concentration in E. miniata. Soluble protein contents were not affected by CO2 enric hment in either species. These results are discussed in relation to th e competitive relationship between these two species in northern Austr alia.