Using depression deposits to reconstruct human impact on sediment yields from a small karst catchment over the past 600 years

Assessment of long-term human impact on sediment yields from karst settings can improve our understanding of the pattern of soil erosion causing rocky desertification in the historical context of environmental change influenced by human activity. Few previous investigations have estimated this impact over time-scales longer than 50 years. This study used dated depression deposits to reconstruct human impact on sediment yields from a small karst catchment in the Three Gorges Reservoir Region, China, over the past 600 years. ¹³⁷Cs, ²¹⁰Pb_ex, and ¹⁴C techniques were used to determine short-term (~50 yr), medium-term (~100 yr), and long-term (~600 yr) sedimentation in the karst depression, respectively. Sedimentation rates and specific sediment yields in the catchment during six distinct stages (1351–1462, 1463–1701, 1702–1809, 1810–1916, 1917–1962, and 1963–2017) were determined from core samples. The results indicate that soil loss during the period 1351–1962 was more intensive than that since 1963, which reveals changing sediment yields impacted by human activity over the past 600 years. The high values during the three stages before 1810 can be attributed to the impacts of large-scale migration of people from Huguang to Sichuan during the Ming and Qing dynasties; the higher values during 1810–1916 might reflect increasing disturbance related to rapid population expansion; the highest values (1917–1962) were caused by large-scale deforestation in 1958 and a consistently increasing population; and low values since 1963 reflect constraints on the supply of sediment source materials. These results suggest that rocky desertification might be a long-term land-surface process induced by human activity over timescales of >100 years rather than a short-term modern process occurring over a number of decades. This is the first attempt to examine the long-term history of human impact on sediment yields from a karst catchment using depression deposits. This work improves our understanding of the influence of human activities on soil loss at a depression-catchment scale, and of the evolution and dynamics of rocky desertification in karst areas.