## 3 Results
### Mineralization Dynamics
#### 3.3.2 Mineralization Dynamics of Soil Aggregates  
Figures 6 and 7 depict the changes in CO\({}_{2}\) emission and cumulative mineralization of soil aggregates under three grassland types over the incubation time. Within the 60-day \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Steppe-Types**} & \multicolumn{3}{c}{**Fitting Parameters**} \\ \cline{2-4}  & **Co (mg C kg\({}^{-1}\))** & **K (d\({}^{-1}\))** & **R\({}^{2}\)** \\ \hline MS & 939.14 \(\pm\) 19.43 a & 0.31 \(\pm\) 0.03 a & 0.94 \\ TS & 775.49 \(\pm\) 16.52 b & 0.26 \(\pm\) 0.04 b & 0.91 \\ DS & 469.66 \(\pm\) 11.30 c & 0.20 \(\pm\) 0.03 c & 0.92 \\ \hline \hline \end{tabular} Different letters indicate a significant difference between steppe types (\(p\) < 0.05). MS: meadow steppe; TS: typical steppe; DS: desert steppe; Co: potential carbon that could be mineralized without time limit; K: parameter of turnover coefficient; R\({}^{2}\): fitting results.  
\end{table} 
Table 2: Dynamic parameters of SOC mineralization process in the Loess Plateau profile. Figure 5: Dynamics and cumulative mineralization of SOC in the Loess Plateau profile. MS: meadow steppe; TS: typical steppe; DS: desert steppe. incubation period, the order of mineralization and cumulative mineralization among different grassland types was MS > TS > DS. The mineralization patterns for different grassland types all exhibited a higher mineralization rate in the initial stage, with a rapid increase in cumulative mineralization. Specifically, the initial 0-10 days showed a faster mineralization rate, reaching a relatively stable state around day 40. Among the three grassland types, the mineralization and cumulative mineralization of different mechanical aggregate sizes were highest in 1-2 mm, followed by 3-5 mm, and lowest in 0.25-0.5 mm. For MS, the cumulative mineralization amounts were 1146.60 mg kg\({}^{-1}\), 1002.75 mg kg\({}^{-1}\), and 880.38 mg kg\({}^{-1}\), respectively. The mineralization rate and cumulative mineralization of different water-stable aggregate sizes were also highest in 1-2 mm, followed by 0.25-0.5 mm, and lowest in <0.053 mm, with MS showing cumulative mineralization amounts of 937.55 mg kg\({}^{-1}\), 848.31 mg kg\({}^{-1}\), and 800.49 mg kg\({}^{-1}\), respectively. In this study, SOC mineralization followed first-order kinetics, as only labile carbon was mineralized during the 60-day incubation period. Curve fitting parameters, as shown in Tables 3 and 4, indicated that the turnover rate coefficient k was highest for MS. The potential mineralizable carbon (Co) was highest for MS and lowest for DS. \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Steppe-Types**} & \multirow{2}{*}{**Particle Size (mm)**} & \multicolumn{3}{c}{**Fitting Parameters**} \\ \cline{3-5}  & & **Co (mg C kg\({}^{-1}\))** & **K (d\({}^{-1}\))** & **R\({}^{2}\)** \\ \hline \multirow{3}{*}{MS} & 1–2 & 1066.47 \(\pm\) 25.28 a & 0.39 \(\pm\) 0.05 ab & 0.83 \\  & 3–5 & 932.03 \(\pm\) 23.11 b & 0.38 \(\pm\) 0.05 abc & 0.82 \\  & 0.25–0.5 & 817.33 \(\pm\) 26.37 d & 0.34 \(\pm\) 0.05 bc & 0.80 \\ \hline \end{tabular}
\end{table} 
Table 3: Dynamic parameters of the SOC mineralization process of mechanical aggregates in the Loess Plateau. Figure 6: Dynamics and cumulative mineralization of SOC of mechanical aggregates in the Loess Plateau. MS: meadow steppe; TS: typical steppe; DS: desert steppe.