Water management and wheat yields in ancient China: Carbon isotope discrimination of archaeological wheat grains

The evaluation of ancient crop production and its response to climate change is key to exploring the ancient demographic and social changes. Wheat is currently the third most widely cultivated crop worldwide and was a major component across of the agricultural systems of the ancient Eurasia. In this study, the Delta C-13 values of 116 charred wheat grains from 28 archaeological sites, with direct AMS C-14 dating of 3952 +/- 66 to 389 +/- 73 cal yr BP, across northern China are reported. The result shows that the Delta C-13 values estimated wheat yields ranged from 0.5 to 2.5 Mg ha(-1), during the past 4000 years. The water supply and grain yield of wheat cultivation is the highest in China during the Bronze Age; however, the water supply and yield were significantly affected by climate fluctuation in the middle-late Holocene. No significant long-term trend of increasing wheat yield is observed over this interval, but a correlation between Delta C-13 values estimated wheat yield and cyclical climate changes can be noted.