Vegetation characteristics in the western Loess plateau between 5200 and 4300 cal. BP based on fossil charcoal records

Understanding terrestrial vegetation dynamics is a crucial tool in global change research. The Loess Plateau, an important area for the study of Asian monsoons and early agriculture, poses a controversial question on the potential vegetation and its pattern. Fossil charcoal as direct evidence of wood provides precision in species identification and hence vegetation reconstruction. Charcoals from the Dadiwan and Xishanping sites suggest a great variety of plants between 5200 and 4300 cal. b.p. in the valley area of the western Loess Plateau. The deciduous broad-leaf wood from Quercus, Ulmus, Betula, Corylus and Acer is very frequent and makes up almost half the total abundance ratio of the represented taxa. Meanwhile, some typical subtropical taxa such as Liquidambar formosana, Eucommia ulmoides, Toxicodendron and Bambusoideae, are present at the two study sites. The high abundance of Picea appearing between 5200 and 4300 cal. b.p. suggests the development of Picea forests in the valley of the western Loess Plateau. The assemblages of charcoal indicate that the mixed forest of evergreen deciduous and conifer-deciduous broadleaved trees developed in the valley of the Loess Plateau during the Holocene optimum. Precipitation is the main controlling factor for forest development. The increasing precipitation is the probable reason for the appearance of north-subtropical forests between 5200 and 4300 cal. b.p.