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United States Department of Agriculture

Agricultural Research Service

Title: Dynamics of Labile and Recalcitrant Soil Carbon Pools in a Sorghum Free-Air Co2 Enrichment (Face) Agroecosystem

Authors
item Cheng, L - UNIV OF AZ, TUCSON
item Leavitt, S - UNIV OF AZ, TUCSON
item KIMBALL, BRUCE
item Pinter Jr, Paul
item Ottman, M - UNIV OF AZ, TUCSON
item Matthias, A - UNIV OF AZ, TUCSON
item WALL, GERARD
item Brooks, T - USDA-ARS-USWCL, PHOENIX
item Williams, D - UNIV OF WYOMING
item Thompson, T - UNIV OF AZ, TUCSON

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 18, 2004
Publication Date: December 13, 2004
Citation: Cheng, L., Leavitt, S.W., Kimball, B.A., Pinter Jr, P.J., Ottman, M.J., Matthias, A., Wall, G.W., Brooks, T., Williams, D.G., Thompson, T.L. 2004. Dynamics of labile and recalcitrant soil carbon pools in a sorghum free-air co2 enrichment (face) agroecosystem. Agronomy Abstracts. B13C-0242.

Technical Abstract: Experimentation with dynamics of soil carbon pools as affected by elevated CO2 can better define the ability of terrestrial ecosystems to sequester global carbon. In the present study, 6 N HC1 hydrolysis and stable carbon isotopic (Delta 13 C) analysis were used to investigate the labile and recalcitrant soil carbon pools and the translocation, among these pools, of sorghum residues isotopically labeled in the 1998-1999 Arizona Maricopa Free Air CO2 Enrichment (FACE) experiment, in which elevated CO2 (FACE: 560 ppmv) and ambient CO2 (Control: 360 ppmv) interact with well-watered (wet) and water-stressed (dry) treatments. We found that on average 53% of the final soil organic carbon (SOC) in the FACE plot was in the recalcitrant carbon pool and 47% in the labile pool, whereas in the Control plot 46% and 54% of carbon were in recalcitrant and labile pools, respectively, indicating that elevated CO2 resulted in more SOC transferred into a slow-decay carbon pool. Also, isotopic mass balance analysis reveals that more new sorghum residue input to the recalcitrant pool mainly accounts for this change, especially for the upper soil horizon (0-30 cm) where new carbon in FACE wet and dry soil recalcitrant pools were 1.7 and 2.8 times those in Control wet and dry recalcitrant pools, respectively. Mean residence time of bulk soil carbon at the depth of 0-30 cm increased from 17 plus or minus 5.2 yrs in the Control plots compared to 37 plus or minus 23.6 yrs in FACE plots, which was positively correlated to the ratio of carbon content in the recalcitrant pool to total SOC and negatively correlated to the raio of carbon content in the labile pool to that in total SOC. Our results imply that terrestrial ecosystem such as agroecosystems may play a critical role in mitigating excess CO2 in the furture atmosphere.

Last Modified: 8/19/2014
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