Mitigation of soil organic carbon mineralization by soil redistribution - An erosion-deposition plot study under natural rainfall over five years

Abstract

As the essential driving force of soil redistribution, runoff and sediment are not often considered when quantifying and integrating the effects of soil erosion and deposition on soil CO2 emissions. Therefore, in this study, variations in soil CO2 emissions from erosion-deposition plots were regularly monitored in China’s Loess Plateau (2015–2019). The cumulative soil CO2 emissions from the depositional zones with slope gradients of 5°, 10°, and 20° were increased by 0.4–16.7%, 20.1–32.6%, and 31.9–51.5%, respectively, than those of their respective eroding slopes. Relative to the 5° eroding slopes, the cumulative soil CO2 emissions decreased by 2.8–13.5% and 11.3–15.6% on the steeper 10° and 20° eroding slopes, respectively. Conversely, cumulative soil CO2 emissions increased by 1.0–7.9% and 6.9–13.3% in the depositional zones of 10° and 20°, respectively, as compared with that in the 5° depositional zones. Considering both the eroding slopes and depositional zones, the total amount of CO2 emissions from the 10° and 20° erosion-deposition plots were 114 g CO2-C y−1 and 177 g CO2-C y−1 lower than those from the 5° erosion-deposition plots, respectively. This can be attributed to the combined effects of the amounts of runoff and sediment displacement on soil CO2 emissions from eroding slopes and depositional zones. Our results indicate that, soil erosion and deposition together have great potential to mitigate soil organic carbon mineralization and preserve soil carbon pools in slope lands. Furthermore, soil organic carbon mineralization at the slope scale is sensitive to displaced runoff and sediment. Therefore, possible variations in soil-atmospheric carbon exchanges induced by erosion-displaced runoff and sediment should be properly accounted for when attributing carbon fluxes in regions dominated by sloping landscapes.