Friday, August 7, 2009: 10:10 AM
Sendero Blrm I, Hyatt
Lei Cheng1, Cong Tu2, Fitzgerald L. Booker3, Kent O. Burkey4, H. David Shew5, Thomas W. Rufty2 and Shuijin Hu5, (1)Life Sciences, Zhejiang University, Hangzhou, China, (2)Department of Plant Pathology, North Carolina State University, Raleigh, NC, (3)Crop Science & USDA-ARS, North Carolina State University, Raleigh, NC, (4)USDA, Plant Science Research Unit, NC, (5)Plant Pathology, North Carolina State University, Raleigh, NC
Background/Question/Methods A great effort in global change research has recently been directed towards assessing the potential of soil as a C sink under future CO2 scenarios. Considerable attention has been focused on the impact of elevated CO2 on mycorrhizae, particularly arbuscular mycorrhizae (AM), assuming that stimulation of mycorrhizae by elevated CO2 will enhance soil C sequestration through facilitating soil aggregation and reducing C losses. However, the role of AM fungi in organic matter decomposition in response to global change factors has not been carefully assessed. Results/Conclusions
Here we present results from two independent but complementary experiments illustrating that CO2-enhancement of AM fungi increases organic carbon decomposition, positively feeding back to atmospheric CO2. Results from 15N tracer measurements also indicated that elevated CO2 considerably increased mycorrhizally-mediated plant N acquisition from decomposing residues. These findings directly challenge the current view that increasing mycorrhizal fungi with rising CO2 could increase soil C sequestration. They also suggest that mycorrhizal fungi might shortcut soil N cycle by increasing plant N acquisition from decomposing residues under elevated CO2, especially in N-poor soils, thereby alleviating N limitation on ecosystem responses to elevated CO2.
