Mainstream migration events of the Yellow River and anthropogenic responses during the Mid-Holocene

The flooding and diversion of the Yellow River is a major concern for the Chinese. Since the Spring and Autumn Period and the Warring States periods, historical documents have recorded many events of the Yellow River's migration and diversion, but there are few records of earlier events. The ancient Daluze Lake, located in the transitional area between the North China Plain and the Taihang Mountains, has been greatly affected by the Yellow River's flooding throughout history. The sediment in the lake continuously recorded the regional environmental evolution information, which is of significant value for studying prehistoric floods of the Yellow River and the interactive effects of early human activities and natural environment. Using a combination of geophysical, geochemical, and biological properties of drilling sediments, we establish the climate and vegetation evolution history in the ancient Daluze region since the Middle Holocene, and discuss a migration event of the Yellow River in the Middle Holocene. The results suggest that: 1) Since Mid-Holocene, the ancient vegetation of the Daluze area has always been a temperate mixed coniferous-broadleaf forest type of sparse forest-grassland, but its internal structure has changed: the local vegetation experienced a transition from sparse forest-grassland vegetation to grassland-meadow expansion, while in the middle of the Holocene (∼ca. 4.04 ka) forest vegetation began to show a growth trend. 2) At about ca. 4.04 ka, an environmental anomaly event occurred in the ancient Daluze area, with grain size and other indicators changed significantly, indicating that the Yellow River may have undergone a migration: the mainstream of the Yellow River changed from northward to southward and forced the ancient humans of the Longshan Culture and Dawenkou Culture periods to construct ramparts to prevent flood disasters caused by the migration of the mainstream of the Yellow River. The study deepens the understanding of the environmental evolution history and human-environment relationship of the Daluze area to some extent, and provides some theoretical basis for local ecological restoration and sustainable development.