C4-derived soil organic carbon decomposes faster than its C3 counterpart in mixed C3/C4 soils

Wynn, Jonathan G., and Bird, Michael I. (2007) C4-derived soil organic carbon decomposes faster than its C3 counterpart in mixed C3/C4 soils. Global Change Biology, 13 (10). pp. 2206-2217.

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The large difference in the degree of discrimination of stable carbon isotopes between C3 and C4 plants is widely exploited in global change and carbon cycle research, often with the assumption that carbon retains the carbon isotopic signature of its photosynthetic pathway during later stages of decomposition in soil and sediments. We applied long-term incubation experiments and natural 13C-labelling of C3 and C4-derived soil organic carbon (SOC) collected from across major environmental gradients in Australia to elucidate a significant difference in the rate of decomposition of C3- and C4-derived SOC. We find that the active pool of SOC (ASOC) derived from C4 plants decomposes at over twice the rate of the total pool of ASOC. As a result, the proportion of C4 photosynthesis represented in the heterotrophic CO2 flux from soil must be over twice the proportional representation of C4-derived biomass in SOC. This observation has significant implications for much carbon cycle research that exploits the carbon isotopic difference in these two photosynthetic pathways.

Item ID: 18908
Item Type: Article (Research - C1)
ISSN: 1365-2486
Keywords: C3-plants; C4; decomposition rate; soil organic carbon; stable carbon isotope
Date Deposited: 03 Oct 2011 02:17
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040203 Isotope Geochemistry @ 100%
SEO Codes: 96 ENVIRONMENT > 9614 Soils > 961403 Forest and Woodlands Soils @ 50%
96 ENVIRONMENT > 9614 Soils > 961406 Sparseland, Permanent Grassland and Arid Zone Soils @ 50%
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