Single-grain OSL dating reveals coupled natural and anthropogenic soil redistribution in northeastern China

Worldwide, fertile black soils have experienced severe degradation due to agriculturally induced erosion. Disentangling and quantifying the relative contributions of anthropogenic versus natural soil transport remains challenging because their signals often overlap in colluvial soil archives. In northeastern China, black soils have been cultivated for only ∼200 years, providing a unique setting to distinguish human-induced erosion from natural soil transport. We investigated the single-grain post-infrared infrared stimulated luminescence (pIRIR) signals of potassium feldspar from 19 samples collected along 3 profiles within a hillslope catena with a mean slope of 1.91°, and compared the luminescence results with other soil properties. Single-grain luminescence data enabled the reconstruction of sediment transport pathways by capturing grain-scale bleaching histories, thereby distinguishing slow subsurface creep, representing natural processes, from rapid surface-driven erosion associated with tillage. Abrupt changes in soil properties at 43 cm, an age inversion between 40 and 60 cm within the colluvium, and truncated upslope soil profiles indicate that intensive soil redistribution coincided with the onset of regional agriculture. The deeper colluvium (60–180 cm) records an earlier phase of soil transport, likely driven by natural soil creep. In contrast, modern anthropogenic deposition rates (1.61–2.04 mm/a) are approximately 20–25 times higher than natural OSL-derived rates rate (mean: 0.16 mm/a), underscoring the dominant role of agricultural activity in accelerating soil redistribution during the late Holocene. Although these findings are derived from a single hillslope catena and therefore require validation across a broader range of slope settings, they demonstrate the potential of single-grain luminescence dating to disentangle natural and anthropogenic soil transport processes in recently cultivated black-soil landscapes.