COMBINED EFFECTS OF CO2 CONCENTRATION AND NUTRIENT STATUS ON THE BIOMASS PRODUCTION AND NUTRIENT-UPTAKE OF BIRCH SEEDLINGS (BETULA-PENDULA)

Birch seedlings (Betula pendula) were grown for four months in a greenhouse at three nutrient levels (fertilization of 0, 100 and 500 kg ha(-1) monthly) and at four CO2 concentrations (350, 700, 1050 and 1400 ppm). The effect of CO2 concentration on the biomass production depended on the nutrient status. When mineralization of the soil material was the only source of nutrients (0 kg ha(-1)), CO2 enhancement reduced the biomass production slightly, whereas the highest production increase occurred at a fertilization of 100 kg ha(-1), being over 100% between 350 and 700 ppm CO2. At 500 kg ha(-1) the production increase was smaller, and the production decreased beyond a CO2 concentration of 700 ppm. The CO2 concentration had a slight effect on the biomass distribution, the leaves accounting for the highest proportion at the lowest CO2 concentration (350 ppm). An increase in nutrient status led to a longer growth period and increased the nutrient concentrations in the plants, but the CO2 concentration had no effect on the growth rhythm and higher CO2 reduced the nutrient concentrations.