583-13 Roots Increase the Temperature Sensitivity of Soil Carbon Decomposition.

Poster Number 483

See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: Div. S03 Graduate Student Poster Competition (Posters)

Monday, 6 October 2008
George R. Brown Convention Center, Exhibit Hall E

Biao Zhu, Jessica Gutknecht, Daniel Keck and Weixin Cheng, Department of Environmental Studies, University of California at Santa Cruz, Santa Cruz, CA
Abstract:
The temperature sensitivity of soil CO2 efflux underlies a potentially important feedback mechanism in the global carbon cycle, yet remains a subject of debate.  Total soil CO2 efflux originates from two main sources, rhizosphere respiration of root-derived carbon by roots and associated rhizosphere microbes and microbial respiration of soil organic carbon (SOC).  The two sources also interact through a process known as the rhizosphere priming effect in which root-derived carbon stimulates microbial respiration of soil organic carbon.  Here we ask which component of soil CO2 efflux is more sensitive to warming, rhizosphere respiration, SOC decomposition, or rhizosphere-primed SOC decomposition?  Past studies excluding roots from soil or soil incubations totally without plants omit the rhizospere respiration component and the rhizosphere priming effect, while field-warming experiments that measure total soil CO2 efflux cannot discern the temperature sensitivity of rhizosphere respiration from that of SOC decomposition.  Results from a continuous 13C-labeling experiment show that, with 3ºC warming, rhizosphere-primed SOC decomposition increases 50% and exhibits the highest temperature sensitivity; whereas total soil CO2 efflux, rhizosphere respiration, and SOC decomposition from soil incubation without plants are virtually insensitive.  These results indicate that root-soil interactions play a pivital role in determining the overall temperature sensitivity of SOC decomposition.

See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: Div. S03 Graduate Student Poster Competition (Posters)