Vegetation and Agriculture Since the Jomon Age with Special Reference to Evidence in the Northwest Boso Region, Central Japan

Abstract

The late Holocene after ca. 4, 500 years B.P. consists of four forest stages. The first (ca. 4, 500-3, 500 years B.P.) is characterized by plentiful deciduous broadleaf trees with Japanese nutmeg (Torreya nucifera). The second (ca. 3, 500-1, 900 years B.P.) shows the maximum development of the warm-temperate evergreen oak. A large expansion of the evergreen oak began at about 3, 000 years later than that in the south western Japan (e.g. Osaka region). The third (ca. 1, 900-1, 500 years B.P.) is distinguished by a small expansion of Cryptomeria japonica. The last (after ca. 1, 500 years B.P.) is the secondary pine forest stage. Two vegetational destructions by a human activity are recognized. In the first destruction (about 2, 300 years B.P. based upon radiocarbon ages), marsh alder forest was destroyed, followed by a rice crop. The second destruction is characterized by a disappearance of natural forest mainly composed of evergreen oak followed by a rapid expansion of the secondary pine forest. Important scoriaceous tephra as a time marker of about 1, 900 years B.P., erupted from the Fuji volcano, is first found in the Boso region and is named the Moro ash.