Reconstruction of cropland cover using historical literature in Northern China, Sui Dynasty, AD 609

Reconstruction of historical cropland cover is not only essential for studying agricultural development in historical periods, but also provides the basic data for long-term global and climatic change simulations. However, reconstructing the amount and spatial distribution of cropland prior to the past millennium remains challenging because of incomplete data and the suitability of the allocation method. Based on the household census and cropland demand per household data, which was calculated from grain consumption per household and crop yield per unit area, this study estimated the prefecture-level cropland area in northern China in AD 609 during the Sui dynasty. Then, a cropland allocation model based on natural land suitability for cultivation was used to reconstruct the spatial distribution of cropland in 5′ × 5′ grid cells. The results were as follows: (1) the cropland area in northern China in AD 609 was 1.77 × 105 km2, with an average cropland area fraction of 10.04%. (2) The cropland was continuously distributed in the North China Plain, Guanzhong Plain, Fenhe Valley and central Shangdang and Changping on the Loess Plateau, resulting in a high cropland agglomeration area appearing in those regions. While it is scattered in the northern Loess Plateau and the Hexi Corridor. (3) Compared with our reconstruction, the HYDE dataset underestimated the cropland area in plains except for riverine areas and overestimated the cropland area in the hills and mountainous areas along the border. (4) This discrepancy was primarily derived from population differences and the divergent cropland allocation methods between the two datasets.