2008 Joint Annual Meeting (5-9 Oct. 2008): Roots Increase the Temperature Sensitivity of Soil Carbon Decomposition.
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583-13 Roots Increase the Temperature Sensitivity of Soil Carbon Decomposition.



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, 1156 High Street, Santa Cruz, CA 95064
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.
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