Pyrogenic carbon records of Holocene fire dynamics in the Yellow River Basin: Climate change and human activity forcing

Abstract

Fire is a crucial component of Earth's ecosystems, with important environmental and socioeconomic implications. In this paper, we analyze black carbon and polycyclic aromatic hydrocarbons in a sediment core (YS-A) from the South Yellow Sea to investigate the driving forces of fire activity in the Yellow River Basin since 7.0 ka BP, when sea level stabilized and the modern pattern of ocean circulation system established. Our results indicate that fire activity gradually increased between 7.0 and 4.0 ka BP, reaching its highest level around 4.0–3.5 ka BP, and weakened between 3.5 and 0.5 ka BP, before rapidly increasing again after 0.5 ka BP. Climate change was found to be the dominant factor influencing fire history, with drier climatic conditions promoting fire activity during 7.0–4.0 ka BP, but suppressing it after 4.0 ka BP. This varied response of fire to climatic conditions is linked to the complex interaction between rainfall, vegetation cover, and fuel availability. Human activity is also shown to exert a complex impact, with some activities, such as deforestation, reducing vegetation cover and limiting fire activity over Late Holocene timescales, while other factors, such as coal burning, increasing high-temperature combustion since 0.5 ka BP. Furthermore, our findings suggest that fire activity has significantly influenced carbon sequestration in marine sediments, leading to an increase in the burial of refractory carbon from approximately 12 % to 18 % between 7.0 and 3.5 ka BP, and a higher proportion of terrestrial organic matter.