Lateral transport of soil total carbon with slope runoff and interflow: Effects of rainstorm characteristics under simulated rainfall.

In order to study the characteristics of soil total carbon (TC) transport with slope runoff and interflow during rainstorms in the Zhejiang-Fujian hilly region, China. Slope gradients (5, 8, 15, 25°) and rainfall intensities (60, 90, 150 mm·h−1) were selected as the variable factors for artificially simulated rainfall experiments. Runoff samples were collected every 3 min to measure the volume and TC mass concentration, then we calculated the TC loss rates and loss gross amount. The results showed that the overall trend of TC mass concentration in slope runoff presented a high initial value that gradually decreased with the increase of rainfall duration and finally tended to be stable, and it mean mass concentration was relatively highest at all the 15° conditions. The TC loss rates presented a stability at a certain value after gradually increasing over time at gentle slopes while it led to an increasing trend when the slope was steeper, yet these trends weren't obvious at 150 mm·h−1 condition. The initial TC mass concentration was low at beginning in interflow which rose rapidly to the peak and finally continued to drop to a stable level. The shape of TC loss rate curves was similar to mass concentration curves. For both slope runoff and interflow, the slope gradient had little effect on TC mass concentration. The TC loss gross amount in the runoff (slope runoff + interflow) increased with the increase of slope gradients or rainfall intensities, which reached the maximum value at the 25°, 150 mm·h−1 condition, namely, 12.56 g, though the increase rates of TC transport decreased. The TC loss gross amount with slope runoff showed a trend of increasing first and then decreasing with increasing slope gradients, which all reached the maximum at 8° conditions, however it showed a continued rising trend as slope gradients increased in interflow. TC at 15° and 25° conditions mainly lost with the interflow, though at other slope gradients it mainly transported with the slope runoff. Similarly, the more gentle the slope gradients, the greater the proportion of the slope runoff volume in total runoff. The regression analysis showed at identical conditions, the influence of rainfall intensity on TC loss was larger than slope gradient in slope runoff while the slope gradient had a greater influence on TC loss in interflow. Correlation analysis showed that there was a significant correlation between the runoff volume and the TC loss gross amount in slope runoff and interflow (P < 0.01). There was a linear correlation between runoff volume and TC loss in slope runoff (R2 = 0.95), and power function fits the relationship between TC loss in interflow and runoff volume better (R2 = 0.66). The results provided a calculation method for estimating TC loss in runoff from bare land of weathered granite parent soil in the Zhejiang-Fujian hilly region of China. • The first study on process of total carbon transport on weathered granite parent soil. • Total carbon loss increases as the slope gradient or rainfall intensity increase. • Rainfall intensity has a greater influence on total carbon loss in slope runoff. • Slope gradient has a greater influence on total carbon loss in interflow. • Runoff volume is the most important factor in total carbon loss. [ABSTRACT FROM AUTHOR]