SOIL CARBON STORAGE

Element interactions limit soil carbon storage
Kees-Jan van Groenigen*,†,‡,
Johan Six*,
Bruce A. Hungate§,
Marie-Anne de Graaff*,†,
Nico van Breemen†, and
Chris van Kessel*
+Author Affiliations

*Department of Plant Sciences, One Shields Avenue, University of California, Davis, CA 95616;

†Laboratory for Soil Science and Geology, Wageningen University, P.O. Box 37, 6700 AA, Wageningen, The Netherlands; and

§Department of Biological Sciences and Merriam–Powell Center for Environmental Research, Northern Arizona University, P.O. Box 5640, Flagstaff, AZ 86011
Edited by Christopher B. Field, Carnegie Institution of Washington, Stanford, CA, and approved March 7, 2006 (received for review October 15, 2005)
Abstract
Rising levels of atmospheric CO2 are thought to increase C sinks in terrestrial ecosystems. The potential of these sinks to mitigate CO2 emissions, however, may be constrained by nutrients. By using metaanalysis, we found that elevated CO2 only causes accumulation of soil C when N is added at rates well above typical atmospheric N inputs. Similarly, elevated CO2 only enhances N2 fixation, the major natural process providing soil N input, when other nutrients (e.g., phosphorus, molybdenum, and potassium) are added. Hence, soil C sequestration under elevated CO2 is constrained both directly by N availability and indirectly by nutrients needed to support N2 fixation.