Charcoal records of Holocene loess-soil sequences and its palaeoenvironmental significance in Weihe River Drainage
渭河流域全新世土壤剖面木炭屑记录及其古环境意义

Analysis (of samples collected through field investigation) of total organic carbon, magnetic susceptibility of Holocene loess-soil charcoal sequences in Weihe River Drainage have revealed the relationship between Holocene wildfire occurrence changes and ecological environment. The current study shows that total organic carbon (TOC) does not fully indicate the occurrence of wildfire in an ecological environment. However, charcoal is regarded as a direct and reliable indicator of wildfire occurrence. Indications of changes in Holocene and charcoal environment have great environmental significance. Before 11 500 a B.P., the climate was arid and wildfire frequently occurred in semi-desert grasslands. Conversely, the incidence of wildfires decreased during the early Holocene epoch. During the optimum Holocene climatic between 8 500 a B.P. and 3 100 a B.P., natural wildfires occurrence fell sharply. Pathogenic alterations in dust accumulation processes were so active that forest-grasslands formed under humid warmer Holocene Mega thermal climate. However, with regional distinction, localized wildfires in connection with human activity occasionally occurred. Levels of burnt biomass were very high during the Late Holocene epoch when the climate was drier and historical land-use more intensive in the study area. After 1 500 a B.P., the amount of charcoal sharply decreased and wildfire occurrence slowly disappeared. It may had resulted from a significant change in land use pattern. The artificial-natural ecological landscape had been established and large-scale burning of land did not occured. Charcoal could therefore be used as a vital indicator for human activity in geological time.