SEASONAL AND ANNUAL VARIATIONS OF PHOSPHORUS, CALCIUM, POTASSIUM AND MANGANESE CONTENTS IN DIFFERENT CROSS-SECTIONS OF PICEA-ABIES (L) KARST NEEDLES AND QUERCUS-RUBRA L LEAVES EXPOSED TO ELEVATED CO2

Norway spruce and red oak trees were planted directly into the soil an d enclosed in open-top chambers. For 2 years the trees were exposed to both ambient and elevated CO2 concentrations (700 mu mol mol(-1)) and during this time variations in nutrient concentrations were studied. CO2-treated plants had decreases in global leaf concentrations of nitr ogen, potassium, calcium and manganese for both species. When differen t areas of the foliage were analysed however, the response showed much variability between the respective sites and between species. Further more the nutrient concentrations changed differently as the plant mate rial aged and this change showed inter-treatment differences. These re sults show how it may be important to analyse plant material of differ ent ages and at different cell sites when studying nutrient levels.