Human impact overwhelms long-term climatic control on C4 vegetation in the Yellow River Basin after 3 ka BP

Abstract

The distribution and evolution of C4 plants are closely related to climate change. However, with the development of agriculture, to what extent human activities affect the natural environment and play an important role in controlling C3/C4 vegetation remains unclear. In this study, the carbon isotopic composition of black carbon (BC) extracted from sediments in core CSDP-1 in the western South Yellow Sea was used to reconstruct the evolution of C3/C4 vegetation in the Yellow River Basin since ∼7 ka BP. The results show that the warm and humid climate in northern China was more suitable for C4 plant growth during the middle Holocene. The relative abundance of C4 plants in the source region, the Yellow River Basin, decreased with lower temperature and precipitation from 7 to 3 ka BP. However, after ∼3 ka BP, the inherent relationship between climate and vegetation growth decoupled, with rapid expansion of C4 plants under cooling and drying climates. We suggest that strengthened human activity (including deforestation and cultivating C4 crops) replaced climate as the main factor affecting C3/C4 vegetation during the late Holocene.

Keywords

• C4 plant expansion
• Yellow River Basin
• South Yellow Sea
• Black carbon
• Holocene
• Anthropocene