Depthwise Carbon Dioxide Production and Transport in a Rangeland Soil
2012
Verma, A. K. | Kelleners, T. J.
The objective of this study was to determine depthwise CO2 production in a semiarid rangeland soil near Laramie, WY, and to quantify the controls exerted by soil temperature and moisture. Depthwise CO2 flux and production were calculated for the 1 Nov. 2010 to 31 Oct. 2011 study period using continuous measurements of soil CO2 concentration, temperature, and water content. Calculated soil efflux using two different tortuosity models was compared with ecosystem respiration (Reco) as measured by a surface flux chamber. The efflux was mostly lower than the Reco values, as would be expected. Calculated CO2 production for the growing season was dominated by the 7.5- to 15-cm depth (43 g C m-2), compared with the 0- to 7.5-cm depth (17 g C m-2) and the 15- to 25-cm depth (9 g C m-2). The relatively high production at the 7.5- to 15-cm depth was attributed to the fine-textured soil at this depth, resulting in higher surface area, higher soil water retention, and possibly more favorable conditions for biological activity. The soil CO2 production increased with soil temperature, as expected, with temperature quotient (Q10) values of 2.98 and 3.03 for the 0- to 7.5- and 7.5- to 15-cm depths, respectively. Temperature-normalized CO2 production was found to be a function of soil water content (?w) at all depths. Maximum production was observed at ?w = 0.20 to 0.21 m3 m-3 (0-7.5-cm depth), ?w = 0.17 to 0.23 m3 m-3 (7.5-15-cm depth), and ?w = 0.19 to 0.22 m3 m-3 (15-25-cm depth). The range of water contents for which soil respiration is at its peak should be confirmed for other rangelands.
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