Articles | Volume 5, issue 1
Biogeosciences, 5, 123–128, 2008
Biogeosciences, 5, 123–128, 2008

  01 Feb 2008

01 Feb 2008

Relative stability of soil carbon revealed by shifts in δ15N and C:N ratio

F. Conen1, M. Zimmermann2, J. Leifeld3, B. Seth1, and C. Alewell1 F. Conen et al.
  • 1Institute of Environmental Geosciences, University of Basel, Bernoullistr. 30, 4056 Basel, Switzerland
  • 2School of Geosciences, University of Edinburgh, Drummond Street, EH8 9XP Edinburgh, UK
  • 3Research Station ART, Reckenholzstr. 191, 8046 Zürich, Switzerland

Abstract. Life on earth drives a continuous exchange of carbon between soils and the atmosphere. Some forms of soil carbon, or organic matter, are more stable and have a longer residence time in soil than others. Relative differences in stability have often been derived from shifts in δ13C (which is bound to a vegetation change from C3 to C4 type) or through 14C-dating (which is bound to small sample numbers because of high measurement costs). Here, we propose a new concept based on the increase in δ15N and the decrease in C:N ratio with increasing stability. We tested the concept on grasslands at different elevations in the Swiss Alps. Depending on elevation and soil depth, it predicted mineral-associated organic carbon to be 3 to 73 times more stable than particulate organic carbon. Analysis of 14C-ages generally endorsed these predictions.

Final-revised paper