Factors controlling soil organic carbon persistence along an eroding hillslope on the loess belt

We observed significant differences in respiration along the topographical gradient, i.e. 30% more at the downslope and 50% more at the backslope, relative to the uneroded summit position. Soil OC persistence along the hillslope was mainly controlled by the labile OC stock and moisture content. Our in-situ measurements also indicated that the temperature sensitivity of soil OC (as expressed by Q10 values) was strongly related to soil water content. The large stock of OC stored in colluvial soils has a higher temperature sensitivity (Q10 = 3.72 ± 0.17) than in non-depositional slope positions (Q10 = 1.77 ± 0.18 to 2.59 ± 0.13). Given the large stock of labile OC, its high temperature sensitivity and the high water contents that are needed to stabilize OC, we conclude that the OC stored in colluvial soils is particularly vulnerable to OC mineralization under drier/warmer conditions. When considering the large amount of OC that has been buried globally as a result of agricultural erosion during the last decades, the long-term stability of this pool under future land use and/or climate disturbance is an area of concern.