Soil organic C stocks and SOCMA were positively related with CI in both soils at 0–5 cm depth (P < 0.1) for the Mollisol and (P < 0.01) for the Vertisol (Fig. 2). Regression models showed that SOC stocks were higher in the Mollisol than in the Vertisol, at an equivalent value of CI, without differences in slope (Fig. 2a). However, at low values of CI, SOCMAvalues were similar between soils, but differences between soils became higher with increases in CI (Fig. 2c), as a result of higher slope in the Mollisol than in the Vertisol. In fact, increases of SOCMA per each 10% of increase in CI were 0.75 Mg ha−1 in the Mollisol and 0.43 Mg ha−1 in the Vertisol (Fig. 2c).