Erosion effects on carbon dioxide concentration and carbon flux from an Ohio alfisol

Carbon dioxide concentrations in soil both reflect and influence soil biological activity and C nux to the atmosphere. We hypothesized that erosion affects CO2 concentration and C flux from the soil surface because of its effects on soil temperature and water regimes. The soil air concentrations of CO2 and corresponding temperature and water contents were monitored on slight (SLI), moderate (MOD), severe (SEV), and depositional (DEP) phases at 2-wk intervals between May 1996 and June 1997. The ambient soil CO2 concentration and CO2-C nux were determined using gas chromatograph analyses. Seasonal patterns in soil air CO2 concentrations (ranging from a winter low of 0.56 mL L-1 to a summer high of 20.90 mL L-1) predominated over more subtle differences (20-80% variation) due to erosion phase effects. Significantly greater (by 12-37%) CO2 concentrations for SEV and MOD phases over SLI and DEP were observed mainly during the summer. The effects of the erosion phase on soil CO2 concentrations appeared to be indirect through its impacts primarily on soil temperature and, presumably, soil biological activity. Soil air CO2 concentrations were significantly correlated with soil temperature (R-2 = 0.61) and CO2-C (R-2 = 0.65) nux from the soil surface but not with soil water content. Both linear and second-order polynomial regression equations using soil temperature predicted soil CO2 concentration.