The effect of precipitation events on inorganic carbon in soil and shallow groundwater,Konza Prairie LTER Site,NE Kansas,USA

Monthly sampling for 1 year at the Konza Prairie LTER (Long-Term Ecological Research) Site in northeastern Kansas shows a connection between the annual cycles of CO₂ in soil air and shallow groundwater DIC (dissolved inorganic C). Soil air CO₂ reached 6–7% in July to mid-August, when moisture was not limiting to soil respiration. Following the annual maximum there was a sequential decrease in CO₂ in three soil horizons to less than 0.5% because of moisture deficiency in the late summer and temperature decline in the fall and winter. Groundwater pCO₂ reached its maximum of 5% in October; the lag-time of 2–3 months may correspond to the travel time of soil-generated CO₂ to the water table. The time-variable CO₂ caused an annual carbonate-mineral saturation cycle, intensifying limestone dissolution and DIC production when CO₂ was high.