Fire history of the Chinese Loess Plateau under extreme warming scenarios: A case study of the loess-paleosol sequence L5-S5

Abstract

In order to study the history of natural fires under warming scenarios and to evaluate the possible incidence of fires in the future, we analyzed the carbon concentration and carbon isotope composition of black carbon within the loess-paleosol sequence of the Chinese Loess Plateau. Notably, the interglacials in this East Asian monsoon region were abnormally warm. The results from the interval of L5-S5 of the studied Xifeng section suggest that the principal factors controlling natural fires in an interglacial period (S5) and a glacial period (L5) were fuel load and fuel moisture level, respectively. The difference between the carbon isotope composition of black carbon and soil organic carbon during S5LL1 (marine oxygen isotope stage (MIS) 14) was due to the fact that the former records the more positive carbon isotope values of C3 plants caused by drought and low temperatures in the fire season, while the latter records the carbon isotope of plants throughout the year. The optimum temperature and humidity conditions during S5SS1 (MIS 13) were the most conducive to fires during the interglacial period of S5. However, when the temperature and humidity decreased to a specific range (mean annual temperature 2-12 °C, mean annual precipitation 200–700 mm) during the glacial period of L5, the fire occurrence reached its highest level.