Partitioning of remobilised N in young beech (Fagus sylvatica L.) is not affected by elevated [CO2]

Effects of elevated CO2 concentration ([CO2]) on the remobilisation of tree internal nitrogen (N) of 3-year-old beech (Fagus sylvatica L.) was determined in a labeling experiment. Trees were pre-treated with N-15 for 1 year and the remobilization of stored N was monitored in ambient (350 ppm) or elevated [CO2] (700 ppm) in the subsequent year. N taken up during the pre-treatment made up 24.7% of total N at the start of the experiment. This value was almost halved after 24 weeks of growth for both CO2-treatments. Significant differences in the partitioning of the remobilized N were only observed transiently after 6 weeks of growth but no CO2-effect was observed at the end of the growing season.