This dataset compiles soil carbonate (i.e., soil inorganic carbon or SIC) content (% C) up to 7.8 m depth under natural vegetation (grassland or woodland) and cropland (rain-fed or irrigated). The dataset was collected to examine whether SIC content changes with decades-old agricultural conversion of natural vegetation.
SIC represent more than a quarter of the terrestrial carbon pool and are often considered to be relatively stable, with fluxes significant only on geologic timescales. However, given the importance of climatic water balance on SIC accumulation, we tested the hypothesis that increased soil water storage and transport resulting from cultivation may enhance dissolution of SIC, altering their local stock at decadal timescales. We compared SIC storage to 7.3 m depth in eight sites across the Great Plains of the United States of America and the Pampas grasslands of Argentina, each site having paired plots of native vegetation and rain-fed croplands, and half of the sites having additional irrigated cropland plots.
We took soil samples down to 8.5 m depth using a direct-push coring rig in the US sites and hand augers at the Argentinean sites. Sampling increments were every 0.3 m in the top 0.61 m of the soil and every 0.61 m thereafter in the US sites, and every 0.2 m to 1 m depth, then every 0.3 m to 4 m depth, and every 0.5 m thereafter in the Argentina sites. Sieved and homogenized soil samples were oven-dried at 60°C for for SIC measurement with a Carlo Erba Elemental Analyzer using the two-temperature combustion method. SIC contents are expressed as %C by weight; we note that this differs from carbonate contents reported by local soil surveys, which are %CaCO3 by weight. Inorganic carbon contents (%C) of the soil and carbonate nodules by depth were multiplied by soil and nodule weights and summed to estimate SIC storage.
