Table 1 List of functions and kinetic parameters.

Parameters describe changes in bulk SOC stocks and C3- and C4-derived C stocks in the four sampled soil layers. R2, coefficient of determination; slopes 1 and 2, significance of the two slopes for segmented regression analysis; K, rate constant; A, annual input of C3-C; C0, SOC stocks before pasture change to OP. **P < 0.01; ***P < 0.001.

Soil layerModel typeFunctionR2Slope 1Slope 2AICk (year−1)Half-lifeAC0
Bulk soil, 0- to 10-cmSegmentedF(t) = 31.87 − 0.42*t0.75***NS88.26
OP-derived C, 0- to 10-cmExponential rise to equilibriumF(t) = −0.62*exp(−0.038*t) + 0.62/0.0380.9166.0**18.1***
Pasture-derived C, 0- to 10-cmSingle exponential decayF(t) = 31.4*exp(t* − 0.037)0.9186.2***18.7***
Bulk soil, 10- to 20-cmSegmentedF(t) = 24.49 − 0.36*t0.83***NS75.52
OP-derived C, 10- to 20-cmLinearF(t) = −0.27 + 0.10*t0.8546.4
Pasture-derived C, 10- to 20-cmSingle exponential decayF(t) = 24.1*exp(t* − 0.02)0.8480.7***34.7***
Bulk soil, 20- to 30-cmSegmentedF(t) = 19.91 − 0.23*t0.75***NS75.08
OP-derived C, 20- to 30-cmLinearF(t) = −0.20 + 0.07*t0.745.56
Pasture-derived C, 20- to 30-cmSingle exponential decayF(t) = 19.8*exp(t* − 0.02)0.7977.7***40.8***
Bulk soil, 30- to 50-cmLinearF(t) = 29.42 − 0.25*t0.7187.73
OP-derived C, 30- to 50-cmLinearF(t) = 0.02 + 0.10*t0.6066.39
Pasture-derived C, 30- to 50-cmSingle exponential decayF(t) = 29.8*exp(t* − 0.016)0.6999***43.3***