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 flux to the atmosphere. We hypothesized that erosion affects C[O.sub.2] concentration and C flux from the soil surface because of its effects on soil temperature and water regimes. The soil air concentrations of C[O.sub.2] 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 C[O.sub.2] concentration and C[O.sub.2]-C flux were determined using gas chromatograph analyses. Seasonal patterns in soil air C[O.sub.2] concentrations (ranging from a winter low of 0.56 mL [L.sup.-1] to a summer high of 20.90 mL [L.sup.-1]) predominated over more subtle differences (20-80% variation) due to erosion phase effects. Significantly greater (by 12-37%) C[O.sub.2] concentrations for SEV and MOD phases over SLI and DEP were observed mainly during the summer. The effects of the erosion phase on soil C[O.sub.2] concentrations appeared to be indirect through its impacts primarily on soil temperature and, presumably, soil biological activity. Soil air C[O.sub.2] concentrations were significantly correlated with soil temperature ([R.sup.2] = 0.61) and C[O.sub.2]-C ([R.sup.2] = 0.65) flux from the soil surface but not with soil water content. Both linear and second-order polynomial regression equations using soil temperature predicted soil C[O.sub.2] concentration.