Home

Editors

Contents

Contribute

Subscribe

Contact

Effects of elevated carbon dioxide concentration on growth and N₂ fixation of young Robinia pseudoacacia

Z. Feng (1), J. Dyckmans (2, 3, 4) and H. Flessa (1)

1. Institute of Soil Science and Forest Nutrition, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany / 2. Environmental Resource Management, Faculty of Agriculture, University College Dublin, Belfield, Dublin 4, Ireland / 3. Institute of Soil Science and Forest Nutrition, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany / 4. Corresponding author (jdyckma@gwdg.de) / Received April 8, 2003; accepted July 20, 2003; published online January 2, 2004

Summary

Effects of elevated CO₂ concentration ([CO₂]) on carbon (C) and nitrogen (N) uptake and N source partitioning (N₂ fixation versus mineral soil N uptake) of 1-year-old Robinia pseudoacacia were determined in a dual ¹³C and ¹⁵N continuous labeling experiment. Seedlings were grown for 16 weeks in ambient (350 ppm) or elevated [CO₂] (700 ppm) with ¹⁵NH₄¹⁵NO₃ as the only mineral nitrogen source. Elevated [CO₂] increased the fraction of new C in total C, but it did not alter C partitioning among plant compartments. Elevated [CO₂] also increased the fraction of new N in total N and this was coupled with a shift in N source partitioning toward N₂ fixation. Soil N uptake was unaffected by elevated [CO₂], whereas N₂ fixation was markedly increased by the elevated [CO₂] treatment, mainly because of increased specific fixation (mg N mg^–1 nodule). As a result of increased N₂ fixation, the C/N ratio of tree biomass tended to decrease in the elevated [CO₂] treatment. Partitioning of N uptake among plant compartments was unaffected by elevated [CO₂]. Total dry mass of root nodules doubled in response to elevated [CO₂], but this effect was not significant because of the great variability of root nodule formation. Our results show that, in the N₂-fixing R. pseudoacacia, increased C uptake in response to increased [CO₂] is matched by increased N₂ fixation, indicating that enhanced growth in elevated [CO₂] might not be restricted by N limitations.

Keywords: carbon uptake, nitrogen uptake, N source partitioning, stable isotope.

---

ISSN 0829-318X Copyright © 2002–2008 Heron Publishing