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

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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.