## Results  
### Effect of Urban-Rural Gradients on Soil Carbon Dynamics: MANOVA Results and Interactions  
MANOVA results (Table 1) show that SOCD, SR, Q\({}_{10}\), and TT differed among two urban-rural gradients related to human distance time (\(p<0.05\)) and ring road (\(p<0.01\)). However, there was no significant interaction between human distance time and ring road (\(p>0.05\)). Using the \(F\)-value as an indicator of the magnitude of the effects of both urban-rural gradients, SOCD and TT were most affected by human disturbance time (7-31% higher \(F\)-values) while SR and Q\({}_{10}\) were most affected by ring roads (51-55% higher \(F\)-values). Influence of Human Disturbance Time on SOCD, SR, Q\({}_{10}\) and TT: Magnitude and Regression Analyses  
Figure 2 shows the magnitude of these differences in SOCD, SR, Q\({}_{10}\) and TT. The highest SOCD, SR, and TT and the lowest Q\({}_{10}\) were found in the oldest urban region, i.e., in the region with 114 years of human disturbance. Linear regression analyses showed a significant increase in SOCD and TT with increasing human disturbance time (\(R^{2}>0.91\), \(p<0.05\)), while a linear and significant decrease was found in Q\({}_{10}\) (\(R^{2}=0.87\), \(p=0.038\)). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Independent Factors** & \(F\) **or \(p\) Values** & **SOCD** & **SR** & **Q\({}_{10}\)** & **TT** \\ \hline Human disturbance time & \(F\)-value & 8.32 * & 2.71 * & 2.45 * & 6.01 * \\  & \(p\)-value & 0.000 * & 0.030 * & 0.047 * & 0.000 * \\  & \(df\) & 4 & 4 & 4 & 4 \\ Ring road urban–rural gradient & \(F\)-value & 7.78 * & 4.20 * & 3.71 * & 4.60 * \\  & \(p\)-value & 0.000 * & 0.003 * & 0.006 * & 0.001 * \\  & \(df\) & 4 & 4 & 4 & 4 \\ Human disturbance time \(\times\) Ring road urban–rural gradient & \(F\)-value & 0.36 & 0.65 & 0.52 & 0.35 \\  & \(p\)-value & 0.939 & 0.735 & 0.843 & 0.946 \\  & \(df\) & 8 & 8 & 8 & 8 \\ \hline \hline \end{tabular} Note: * indicates significant influences of urbanization. SOCD, soil organic carbon density; SR, soil basal respiration rate; and TT, turnover time.  
\end{table} 
Table 1: MANOVA results of urban–rural gradients on soil organic carbon (SOC)-related properties in forest soil of Changchun city of China. Figure 2: Human disturbance time influences on (**A**) SOCD; (**B**) SR; (**C**) Q\({}_{10}\) and (**D**) TT, in forest soil of Changchun city of China. Notes: SOCD, soil organic carbon density; SR, soil basal respiration rate; and TT, turnover time. Error bars showed standard deviation, and lowercase letters indicate significant differences based on the MANOVA test statistics. The same letters indicate no significant differences, and different letters indicate significant differences (\(p<0.05\)). The disturbance time-related variations in SOCD, SR, Q\({}_{10}\) and TT were 1.54-, 1.35-, 1.23-, and 1.38-fold, respectively. Considering the significant linear slopes of their regression analyses as the changing rate, SOCD accumulated 13.4 g C m\({}^{-2}\) year\({}^{-1}\), Q\({}_{10}\) decreased 0.076 year\({}^{-1}\), and TT increased 0.041 year\({}^{-1}\) (Figure 2). Influence of Ring Road Development on SOCD, SR, Q\({}_{10}\) and TT: Magnitude and Regression Analyses  
Significant differences in SOCD, SR, Q\({}_{10}\) and TT were found among the 5 ring roads (Figure 3). A linear increase in SOCD was found from the 5 th to the 1 st ring road, whereas Q\({}_{10}\) presented the opposite trend; such linear relationships were not found for SR and TT. Linear regression analyses showed a significant increase in SOCD (\(R^{2}\) = 0.80, \(p\) = 0.025) and a significant decrease in Q\({}_{10}\) soil temperature stability (\(R^{2}\) = 0.84, \(p\) = 0.028) with increasing ring road development. The variations in ring road-related SOCD, SR, Q\({}_{10}\) and TT were 1.54-, 1.35-, 1.23-, and 1.36-fold, respectively.