Coprostanol records from two distinct prehistoric profiles in the middle and lower reaches of the Yellow River, China, provide evidence of anthropogenic fires

Abstract

Resolving the complex interplay between natural and anthropogenic fire drivers remains a critical challenge in paleoenvironmental studies. This investigation employs an innovative multi-proxy approach integrating fecal stanol biomarkers with high-resolution records of charcoal and black carbon to reconstruct Holocene biomass burning dynamics and human-environment interactions at two key prehistoric profiles: the Yangguancun (YGC) loess profile (Shaanxi Province, the middle reaches of the Yellow River Drainage Basin) and Changyi (CY) terrestrial sequence (Shandong Province, the lower reaches of the Yellow River Basin). Our analysis reveals three distinct fire regime phases across the basin: 1) Early Holocene monsoon-controlled infrequent wildfires (8700–8500 yr BP), 2) Mid-late Holocene localized anthropogenic high biomass burning (6000–1000 yr BP), and 3) Recent millennium-scale regional anthropogenic combustion dominance. Between 6200 and 5300 yr BP, high-intensity biomass burning in the middle reaches of the Yellow River was primarily driven by frequent slash-and-burn practices for forest clearance for millet cultivation and daily subsistence activities during the late Miaodigou and Banpo IV Cultures. Contrastingly, between 4000 and 3500 yr BP, low-intensity smoldering fires in the lower reaches of the Yellow River were associated with persistent aridity and deforestation during the Longshan and Yueshi Cultures. These contrasting fire regimes reflect the complex interplay between monsoon-driven climate variability and anthropogenic land-use practices, leading to significant landscape changes in the region during the mid-to-late Holocene. Meanwhile, the region underwent a vegetation evolution, transitioning from fire-resilient natural forests and grasslands to fire-prone secondary shrub lands and cultivated lands. It was noted that long-term deforestation and vegetation fragmentation, exacerbated by persistent drought, has triggered smoldering biomass burning pattern, which have become a primary driver of future wildfires and vegetation degradation in the middle and lower reaches of the Yellow River. Combining fecal stanol molecular biomarkers with sedimentary charcoal and black carbon records, we clarify the distinctions between natural and human-induced fires, providing a deeper understanding of the impact of anthropogenic biomass burning on regional and global warming.