Archaeobotanical Study In Zongri Site,Qinghai Province,China

Subsistence strategy for adaptation to different environments is a hot spot of Environmental Archaeology,and has been increasingly concerned.The history and influencing factors of the spread of prehistoric human to the Tibetan Plateau,the highest and largest plateau of the world,has been intensively studied in recent years.Recent research shows that agriculture promoted the large-scale permanent settlement on the northeast Tibetan Plateau since 5200 cal yr BP?“BP”means“years before present”?.However,previous archaeobotanical study had more attention at the region with altitude below 2500 m asl on the northeast Tibetan Plateau during the Neolithic Age,and the systematic archaeobotanical study of the late Neolithic period?5200-4000 cal yr BP?above 2500m asl remains unclear,which still need to be further studied.The mean elevation of Gonghe Basin,located in the eastern parts of Qinghai Province,is3000 m asl.Large numbers of Neolithic and Bronze sites distribute in Gonghe basin.Moreover,Zongri culture with local characteristics has been founded,which is approximately contemporaneous with Majiayao and Qijia culture periods.The study of human bones C/N?mol ratio?reveals that C₄ plants was the main food of the Zongri inhabitants?probably millet?,and a lot of pottery remains have been unearthed at Zongri site,indicating that agricultural production may be an important mode of production for Zongri inhabitants.With the excavation in Zongri site in 2015,three culture layers were found.Through the flotation of 134 soil samples and 2351 L soil,4150 charred plant seeds which belong to 12 distinct species are identified.In addition,we directly dated charred crop seeds samples from each culture layer with AMS ¹⁴C dating.Based on these works,combined with published archaeological materials,we study the plant utilization strategy of Zongri culture.We also summarized the plant subsistence transition,as well as influencing factors of it in Gonghe basin and the northeast Tibetan Plateau from late Neolithic to Early Bronze Age.The main conclusions are listed as below.?1?Three culture layers of this excavation in Zongri site was 4550-4400 cal yr BP?4400-4250 cal yr BP and 4150-3950 cal yr BP respectively,roughly the same period in the late Majiayao culture.?2?4148 charred seeds were identified from flotation samples,including 4009 crop seeds which account for 96.65%of total identified charred seeds.Form early to late culture layers,the proportion of crop seeds changed from 94.53%,97.39%to 95.16%.The proportion of broomcorn millet seeds increased from 64.18%,81.79%to 85.25%.In contrast,the proportion of foxtail millet seeds decreased from 30.35%,15.60%to 9.91%.?3?During 4500-3900 cal yr BP,the plant resources used by Zongri prehistoric human were mainly broomcorn and foxtail millet.And broomcorn millet was the primary one.Meanwhile,they also used some wild plants that can be medicinal and edible.?4?In the northeast Tibetan Plateau,the proportion of broomcorn millet and foxtail millet remains varied remarkably from late Neolithic to early Bronze Age.The elevation is the major influencing factor for the spatial difference and climate change is the primary factor for the temporal variation.the proportion of broomcorn millet basically increased when climate was cold and dry.The research work provides the key archaeobotanical evidence for the Zongri inhabitants'utilization strategies of plant resources and lays an important foundation for understanding the spatial and temporal differences of human plant resource utilization and its influencing factors during the late Neolithic to early Bronze Age on the northeastern Tibetan Plateau.This work has a positive significance for promoting the process and pattern of the spread of the prehistoric human to the high altitude area.It is still need to carry out more research on whether millet is grown locally or in exchange in Zongri site.