THE IMPACT OF CLIMATE CHANGE ON RICE AGRICULTURE DURING THE END OF THE SHANG PERIOD:RESULTS OF THE PLANT REMAINS FROM DAXINZHUANG AND LIUJIAZHUANG SITES,JINAN,SHANDONG PROVINCE
The Daxinzhuang (36°42'41.85"N,117°06'13.94"E)and Liujiazhuang (36°41'15.5"N,116°59'58.8"E)sites are located in Jinan City in Shandong Province.Archaeologists have excavated the two sites during 2010.A total of 166 soil samples of Daxinzhuang site were collected mostly from ash pits and layers dated to the Middle and Late Shang periods.Through detailed identification,a total of 24715 plant remains,including plant seeds,fruits and tubers,have been discovered,in which the plant seeds include 17377 crops and 7270 weeds.At Liujiazhuang site,a total of 8544 plant seeds,fruits and tubers,of which 5131 crops and 3360 weeds,have been identified in 128 flotation samples,which were mostly excavated from Late-Shang to Early-Zhou ash pits.Based on the archaeobotanical evidence,the crops in the two sites include foxtail millet(Setaria italica (L.)Beauv.),broomcorn millet(Panicum miliaceum L.),soybean(Glycine max(L.)Merr.),and wheat(Ttiticum aestivum L.).A relatively large quantity of rice (Oryza sativa L.)was discovered at Daxinzhuang site,but no rice seed has been found at Liujiazhuang site.By integrating the findings of plant remains from other sites in this region,it can be reflected that the status of rice cultivation declined during the Late Shang and Early Zhou periods,although rice was one of the main crops during the Yueshi and Shang periods.This trend can also be observed in the Guanzhong Basin and the Central Plains.Multiple geologic records show that the East Asian summer monsoon weakened rapidly around 3000 a B.P.,resulting in the decrease of precipitation in the Shandong region during the end of Shang period.The decrease of precipitation probably could not guarantee the needs of water for local rice agriculture,leading to the decline of rice yields.Hence,the climate change at the end of the Shang period was the main reason for the absence of rice in Liujiazhuang site and decline in quantity of rice in Shandong during the Late Shang and Early Zhou periods.And it was likely to influence the shrink of rice agriculture in the middle and lower Yellow River area during the Late Shang and Early Zhou periods.