Effluxed CO 2- 13C from sterilized and unsterilized treatments of a calcareous soil

• Published in: Soil biology & biochemistry Vol. 38; no. 7; pp. 1727 - 1733
• Main Authors: Stevenson, B.A., Verburg, P.S.J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2006
• Subjects: Calcareous soils; Carbon flux; Carbonates; HgCl 2; Respired CO 2- 13C; Soil sterilization; Respired CO 2- 13C; Calcareous soils; HgCl 2; Soil sterilization; Carbon flux; Carbonates
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2005.11.028

Soil inorganic carbon (C) represents a substantial C pool in arid ecosystems, yet little data exist on the contribution of this pool to ecosystem C fluxes. A closed jar incubation study was carried out to test the hypothesis that CO 2- 13C production and response to sterilization would differ in a calcareous (Mojave Desert) soil and a non-calcareous (Oklahoma Prairie) soil due to contributions of carbonate-derived CO 2. In addition to non-sterilized controls, soils were subjected to sterilization treatments (unbuffered HgCl 2 addition for Oklahoma soil and unbuffered HgCl 2 addition, buffered HgCl 2 addition, and autoclaving for Mojave Desert soil) to decrease biotic respiration and more readily measure abiotic CO 2 flux. Temperature and moisture treatments were also included with sterilization treatments in a factorial design. The rate of CO 2 production in both soils was significantly decreased (36–87%) by sterilization, but sterilization treatments differed in effectiveness. Sterilization had no significant effect on effluxed CO 2- 13C values in the non-calcareous Oklahoma Prairie soil and autoclaved Mojave Desert soil as compared to their respective non-sterilized controls. However, sterilization significantly altered CO 2- 13C values in Mojave Desert soil HgCl 2 sterilization treatments (both buffered and non-buffered). Plots of 1/CO 2 versus CO 2-δ 13C (similar to Keeling plots) indicated that the source CO 2-δ 13C value of the Oklahoma Prairie soil treatments was similar to the δ 13C value of soil organic matter [(SOM); −17.76‰ VPDB] whereas the source for the (acidic) unbuffered-HgCl 2 sterilized Mojave Desert soil was similar to the δ 13C value of carbonates (−0.93‰ VPDB). The source CO 2-δ 13C value of non-sterilized and autoclaved (−18.4‰ VPDB) Mojave Desert soil treatments was intermediate between SOM (−21.43‰ VPDB) and carbonates and indicates up to 13% of total C efflux may be from abiotic sources in calcareous soils.