Evidence of Rice Cultivation in Primorye in the Middle Ages.

A displaced paleosol layer presumably used for rice farming was found in the section under a rampart in the Southern Ussuriysk fortress. The paleosol was periodically flooded, as evidenced by diatoms from different environments. Bulliform rice phytoliths were found in the paleosol. The obtained range of radiocarbon dates made it possible to reconstruct the course of events. Based on a finding of B-Tm cryptotephra of the Baitoushan Volcano (946/947 CE), the rice field existed in the period between the middle of the tenth century and the construction of the fortress at the beginning of the twelfth century. The soil was transferred from the floodplain where soil profiles were formed in the Middle–Late Holocene under drier conditions than in the Middle Ages. The moisture increase in the Medieval Warm Period was favorable for the agriculture development, including the rice cultivation. The deposits formed during severe floods overlapped both the cultural layers and the paleosol of the rice field. It was likely one of the reasons for the end of rice cultivation along with the climate change towards cooling and a decrease in precipitation. [ABSTRACT FROM AUTHOR]