Analysis On Agricultural Development History And Influential Factors In The Upper Reaches Of Wei River Region During The 5500-2000 BP

Human-environment interaction is the core scientific issue of geography.And human adaptation to the environment is the focus of environmental archaeology.The upper reaches of Wei River region are located on the eastern side of the ancient Silk Road.As one of the earliest regions inhabited by ancestors,the upper reaches of Wei River region has a long history of agricultural development and a complete cultural sequence,making it an ideal area for studying the origin of millets agriculture in Northern China and the exchange and spread of eastern and western crops.In recent years,a lot of works have been done and fruitful achievements have been made in the study of environmental archaeology in this area.However,the distribution of research sites and time periods is uneven.it mainly focused on the detailed discussion of a typical site in a certain period,but it has not carried out the study of agricultural development in a large area with a long time scale,nor has systematic dating been done.In the light of the problems above,this paper has completed the identification of14503 charred plant remains from 44 Neolithic-Bronze Age sites of different periods in the upper reaches of Wei River region,including 13603 crop seeds?foxtail millet:10238,broomcorn millet:2032,wheat:1017,barley:259,rice:2 and buckwheat:55?,and the measurement of the length and width grain sizes of 1507,and the dating of AMS¹⁴C at 21 sites.Based on the researches of this paper,the system combined the Wei River upstream region 5500-2000 BP?BP:Before Present?of agricultural development and its affecting factors,combined with Ganqing region,especially the published data in Northeast Tibet Plateau regions,different regional climate mutation strategies were distinctly various by analysing and comparing.The results of this paper are as follows:?1?The utilization of main crops by the ancestors in the upper reaches of Wei River region can be divided into four stages:Stage 1?5500-4300 BP?,the ancestors used millets,mainly used foxtail millet,and broomcorn millet as a supplement.Stage2?4300-3600 BP?,millets were mainly used by the ancestors,but triticeae crops began to spread to the region,but not widely used.Stage 4?3000-2000 BP?,the ancestors mainly used wheat,millets become auxiliary crops.In this paper,the dating results show that there is a gap between 3600-3000 BP,and it is speculated that the human settlement intensity in the upper reaches of Wei River region is low at this stage.?2?The ancestors in the upper reaches of Wei River region carried out a long-term breeding evolution on the main crops,foxtail millet,broomcorn millet,wheat and barley,and the grain size of these crops as a whole showed an increasing trend with the passage of time.?3?The change course of agricultural structure in the upper reaches of Wei River region are mainly influenced by climate,crop characteristics and population.5500-4300 BP,the increase of population settlement intensity prompted ancestors to choose foxtail millet?higher yield than broomcorn millet?as the main crop,and the relatively warm and wet climate conditions provided a guarantee for millets cultivation in this period.4300-3600 BP,wheat was introduced into the upper reaches of Wei River region,but millets were still the main crops.3000-2000 BP,the temperature and precipitation were significantly lower than those in the previous two periods.The ancestors adjusted the planting structure,mainly focusing on wheat and turning millets into auxiliary crops.?4?There are significant spatial and temporal differences in the response patterns of the ancestors in Ganqing region to climate change.From the late Neolithic to the early Bronze Age?circa 4500-3600 BP?,the climate turned warm to cold drying.The ancestors of the Northeast Tibet plateau adjusted their living patterns.After 3600 BP,they adopted the mixed economy of farming and animal husbandry adapted to the alpine environment and settled permanently in the high-altitude region.However,the population in the upper reaches of Wei River region did not adjust the planting structure significantly during this period,which was probably an important reason for the significant decline in human settlement intensity of 3600-3000 BP.About 3000BP,the ancestors in this region changed the main crops from millets to wheat,reflecting the adaptation to the change of living environment.This work obtained a number of important plant archaeology and new AMS¹⁴C data of the Neolithic to Bronze Age sites in the upper reaches of Wei River region,which provided important information for understanding the history of human activities and agricultural development in this area.Through the comparative study of different regional data,it provides valuable research cases for understanding of the new interaction between human and environment in the Middle-late Holocene of Ganqing area.