Vegetation factors are the most important influences on USLE/RUSLE models. The observed data for runoff and sediment yields from field runoff plots between 2011 and 2013, their variation characteristics, and the impacts of rainfall and vegetation types on the C values were analyzed for different time scales. The results showed that: (1) The C values fluctuated between seasons. The values were higher for summer and the fall than for spring and winter, and were similar for summer and fall. Furthermore, dry seasons show higher C values than wet seasons. Specifically, higher values were found in November, August, and July, and lower values were observed in June, May, and January. The C values for herbs were significantly affected by the vegetation coverage. (2) The C values were positively correlated with rainfall volume, and the correlation coefficients between the C values and rainfall volume for individual rainfall events were 0.360^{* *}, 0.349^{* *}, and 0.291^{* *} for the eucalyptus and pine trees, and Melinis minutiflora runoff plots, respectively. The correlation coefficients for average interval rainfall volume and the C values were 0.912^*, 0.909^*, and 0.822 for the eucalyptus and pine trees, and Melinis minutiflora runoff plots, respectively. The rainfall volume had a much stronger influence on the C values for the woody plants compared with the herbaceous plants, suggested that the C values could not be determined by the vegetation coverage alone. (3) A comparison of the runoff plots for bare soil showed that the volume of soil lost was reduced by 14.2%, 21.5%, and 23.2%, and the C values were 0.814, 0.748, and 0.772 for the eucalyptus and pine trees, and Melinis minutiflora runoff plots, respectively. The results showed that Melinis minutiflora and pine trees were better at conserving soil and water than eucalyptus.