Anthropogenic origin of a change in the fire-climate relationship in northern China after similar to 2000 yr BP: Evidence from a 15,500-year black carbon record from Dali Lake

There are debates regarding whether a wet and warm climate or a dry and cold climate dominated Holocene fire activity in northern China on the millennial timescale, and when human activities overtook climate change as the dominant control on fire occurrence in the region. Here we present a high-resolution fire history for the past similar to 15,500 years from a sediment core in Dali Lake, located in the foothills of the Greater Hinggan Mountains, one of the areas of highest fire risk in China. The results demonstrate that fire activity was rare during the last deglaciation (similar to 15,500-11,700 yr BP), gradually increased at the beginning of the Holocene, and reached its highest level during similar to 9000-5000 yr BP, after which there was a decreasing trend. However, after similar to 2000 yr BP this decreasing trend ended, and the most prominent feature is a peak in fire activity during the Medieval Warm Period (MWP). Overall, fire activity corresponded well to changes in the East Asian summer monsoon (EASM) precipitation on the millennial timescale during similar to 15,500-2000 yr BP, but this relationship changed after similar to 2000 yr BP. We propose that fire activity in northern China on the millennial timescale during similar to 15,500-2000 yr BP was dominated by the biofuels reserve under the control of the EASM precipitation. In contrast, with the intensification of human activities after similar to 2000 yr BP, human activity caused a similar to 62%-73% increase in fire activity, which altered the fire-climate relationship that had previously prevailed in northern China. Our results indicate that a wet-warm climate (increased EASM intensity), rather than a dry-cold climate, was the dominant control on fire activity in northern China during 15,500-2000 yr BP on the millennial timescale, but that human activities played an important role in fire occurrence after similar to 2000 yr BP.