Geoarchaeological study of the evolution of rice farming fields in prehistoric Yangtze Delta and Huai River regions of China

The construction of rice fields represents a milestone development in humans' continuous effort to modify and transform their environments for rice framing. They appeared very early in the Yangtze Delta region and continued to develop into diverse forms and structures, becoming essential parts of the expanding rice-farming economies and stimulating great social structural changes in prehistoric and historic times. This paper examines the physical environmental conditions, field construction and modification, and water management of prehistoric rice fields that were excavated recently in the Yangtze Delta and Huai River regions through geoarchaeological surveys of excavated fields and detailed micromorphological and sedimentation analyses of collected samples. We sketch out the broad developmental trajectory of rice fields from the preliminary field modification to systematic landscape transformation during the intensification process of rice farming with macro-scale environmental evidence and micro-morphological evidence. Our results show that alongside the macro-scale morphological changes of the rice fields with a noticeable trend of size increase over the long-term period, are more intensive field management practices as evidenced by the increasing presence of diagnostic soil micromorphological features such as concentric clay textural features and redoximorphic features caused by frequent wet-dry alternations from more sophisticated manipulation of field hydrologies and soils. We also compare the similarities and differences in the scale, structure, and soil and environmental conditions of rice fields in different regions and discuss their significance to understand different intensification processes and interactions with rice-farming societies in prehistoric Yangtze Delta and Huai River regions. We suggest that constrained by regional soil, hydrological and topographic differences, these regions might have undergone intensification and extensification processes. Typically, small fields or field-like structures in the Upper-and-Middle Huai River and around Taihu-Lake regions remained unchanged for a relatively long time until the late Majiabang when systematic transformation of local environments for large-scale rice farming began. This is in contrast with the Ningshao Plain where Hemudu-period rice fields were without field bunds and other facilities. However, the divergent regional trends in the scale and practices of rice farming around the Taihu Lake and Ningshao Plain regions might have converged during the Liangzhu period, leading to a significant expansion in rice fields, as vividly represented by the Shi'ao and Maoshan examples discussed in our paper. • First systematic, cross-regional geoarchaeological study of rice fields and cultivated soils in prehistoric China. • Integrating archaeological, environmental, and soil micromorphological evidence to reconstruct different cultivation modes. • An important research shift to study the evolution of rice farming landscapes