Late Holocene climatic impact on vegetation and human activity in central Japan, recorded in sediment at Arao-Minami archaeological site, northwestern Nobi Plain

Abstract Late Holocene histories of vegetation, human activity, and climate inland of the Nobi Plain, central Japan, were investigated using pollen, charcoal, and chronological (radiocarbon and pottery) analyses of the Arao-Minami archaeological sediment layers. This site was home to a large regional community from the Yayoi to Kofun periods. Agricultural production of buckwheat began before the Middle Yayoi (∼200 BC). Cultivated Poaceae increased in the warm period at ca. 2.2–1.7 cal ka BP (ca. 250 BC to ca. 250 AD), based on the pollen-based climate indices. This can be regarded as intensified wet rice agriculture occurring at this period because the archaeological examinations report the existence of paddy-field remains and rice phytoliths from the Late Yayoi to Early Kofun. This period approximately corresponds to the Roman Warm Period. Primary natural forests, such as Quercus subg. Lepidobalanus , Quercus subg. Cyclobalanopsis , Cupressaceae, and Cryptomeria , as well as cultivated Poaceae gradually decreased from ca. 1.7 to ca. 1.2 cal ka BP (ca. 250 AD to 750 AD), which corresponds to the Dark Age Cold Period. In contrast, an expansion of Pinus conifer forests and temporal rises of accumulation rates occurred in this period. Based on the evidences, we propose that the agriculture at this site temporarily changed to slash-and-burn cultivation at a nearby mountain, associated with the cold climate. In the warm period from ca. 1.2 cal ka BP (ca. 750 AD), cultivated Poaceae increased again, suggesting a return to wet rice agriculture around the site. In this paper, we conclude that ancient people who lived inland of the Nobi Plain adapted to global climate changes.