Einfluß der N-Versorgung und der CO₂-Konzentration auf die Feinwurzelbildung und die Veratmung wurzelbürtigen Kohlenstoffs der Buche

Abstract

Increasing atmospheric CO₂ concentrations and nitrogen deposition may change below ground allocation of assimilates in trees. We conducted an ¹³C labelling experiment with beech to quantify the effects of elevated [CO₂] and tree internal N stocks on the allocation of assimilates to the fine roots and on below ground respiration. Our data show that both elevated [CO₂] and reduced tree internal N stores led to an increased investment of assimilates into root growth and root respiration. Root activity (expressed as below ground respiration per mass unit fine roots) was also increased under elevated [CO₂], but lowered for trees with reduced N stocks growing under ambient [CO₂]. The measured changes in root activity were due to changes in total root growth rather than changes in specific root activity.