Chronosequencing methanogenic archaea in ancient Longji rice Terraces in China

Chronosequences of ancient rice terraces serve as an invaluable archive for reconstructions of historical human-environment interactions. Presently, however, these reconstructions are based on traditional soil physico-chemical properties. The microorganisms in palaeosols have been unexplored. We hypothesized that microbial information can be used as an additional proxy to complement and consolidate archaeological interpretations. To test this hypothesis, the palaeoenvironmental methanogenic archaeal DNA in Longji Terraces, one of the famous ancient terraces in China, dating back to the late Yuan Dynasty (CE 1361–1406), was chronosequenced by high-throughput sequencing. It was found that the methanogenic archaeal abundance, diversity and community composition were closely associated with the 630 years of rice cultivation and in line with changes in multi-proxy data. Particularly, the centennial- and decadal-scale influences of known historical events, including social turbulences (The Taiping Rebellion, CE 1850–1865), palaeoclimate changes (the Little Ice Age) and recorded natural disasters (earthquakes and inundation), on ancient agricultural society were clearly echoed in the microbial archives as variations in alpha and beta diversity. This striking correlation suggests that the microorganisms archived in palaeosols can be quantitatively and qualitatively analyzed to provide an additional proxy, and palaeo-microbial information could be routinely incorporated in the toolkit for archaeological interpretation.