Spatiotemporal Distribution and Geographical Impact Factors of Barley and Wheat during the Late Neolithic and Bronze Age (4000–2300 cal. a BP) in the Gansu–Qinghai Region, Northwest China

During the Late Neolithic and Bronze Age, the spread of Triticeae crops gradually transformed local millet agriculture in the Gansu–Qinghai region. However, few studies focused on the distribution characteristics and geographical factors influencing Triticeae agriculture. Here, geographical data from 65 sites with barley ( Hordeum vulgare ) and wheat ( Triticum aestivum ) remains in Gansu–Qinghai region were studied by spatial analysis in ArcGIS. The results showed that spatiotemporal distribution of barley and wheat exhibited three stages: firstly appeared in the central Hexi Corridor at ~4000 cal. a BP, then spread throughout the Hexi Corridor and Qinghai Lake area during 3600–3200 cal. a BP, and continued to move southward to the Hehuang Valley and Weihe River Basin during 3200–2300 cal. a BP. The studied sites were mainly distributed along rivers and certain altitude with suitable climatic conditions. The average distance to the nearest river was ~8 km, with wheat sites ~300 m closer than barley’s. The average elevation was 3500–1500 m, with wheat sites ~200 m lower than barley’s. The variations in spatiotemporal distribution were attributed to greater environmental tolerance of barley. These findings provide important environmental insights into the spatiotemporal distribution and transmission routes of barley and wheat in northwest China.